ALBERT

Description: There is a strong policy move in Britain to improve forest resilience to climate change by increasing stand structural and species diversity. Although currently little used in Britain, the technique of underplanting allows regeneration and diversification of stands while avoiding some of the disadvantages of clearfelling. Two experiments were examined: (1) the growth and survival of five underplanted conifer species of differing shade tolerance in a shelterwood and (2) compared performance of underplanted and open-grown Douglas-fir seedlings on restocking sites. Underplanted Sitka spruce, Norway spruce, noble fir, European silver fir and Douglas-fir were all able to survive and grow. However increased exposure following overstorey removal resulted in some damage and ‘socketing’, especially to taller seedlings, particularly Douglas-fir. This may be linked to poor root development when growing under an overstorey. Microclimate conditions on some underplanted sites were more sheltered from extreme climatic conditions, and in some cases this improved survival of Douglas-fir seedlings. However, seedling growth rates were reduced compared with those on open sites probably due to lower light levels. Underplanting may help to improve establishment success of some species, particularly in exposed areas. However, the shelter benefits of underplanting must be carefully balanced against the trade-off with lower light, and underplanting is likely to be more successful where low canopy density is maintained.

Description: The recent emergence of Olive Quick Decline Syndrome in Italy, caused by Xylella fastidiosa, has drawn attention to the risks posed by this vector-borne bacterium to important crops in Europe (especially fruit trees and grapevine). Comparatively very little is known on actual and potential impacts of this pathogen in forests, in the native (North American) and introduced (European) regions, respectively. The present review aims to address important questions related to the threat posed by X. fastidiosa to European forests, such as the following: What are the symptoms, hosts and impact of bacterial leaf scorch caused by X. fastidiosa on trees in North America? Which forest tree species have been found infected in the introduction area in Europe? How does X. fastidiosa cause disease in susceptible hosts? Are there any X. fastidiosa genotypes (subspecies and sequence types) specifically associated with forest trees? How is X. fastidiosa transmitted? What are the known and potential vectors for forest trees? How does vector ecology affect disease? Is the distribution of X. fastidiosa, especially the strains associated with trees, restricted by climatic factors? Is disease risk for trees different in forest ecosystems as compared with urban settings? We conclude by pointing to important knowledge gaps related to all these questions and strongly advocate for more research about the Xylella-forest pathosystems, in both North America and Europe.

Description: Wood removed in Southwestern US forest restoration treatments currently has limited markets and thus low value. One important property of wood in structural products is its stiffness (measured as modulus of elasticity), which is known to vary systematically within trees. Directly measuring wood stiffness is expensive, time consuming and destructive. Therefore, we tested samples of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) from northern Arizona destructively in bending and also non-destructively using acoustic velocity (AV) methods. In total, we tested multiple pith-to-bark small clear (2.54 × 2.54 × 40.64 cm) samples from up to four heights in 103 trees. We first measured the standing-tree AV of sample trees, then the AV of small clear samples, and finally measured wood stiffness using three point static bending tests. We found that a Michaelis–Menten curve was a good fit to the radial profile of wood stiffness, with a steep increase outward from the pith that approached an asymptote. The AV of small clear samples, coupled with measured volumetric density values, approximated the static modulus of elasticity values with high accuracy (r2 = 0.86). At the stand level, a model predicting standing tree AV from tree morphology fit the data well (r2 = 0.77). Results indicate that southwestern ponderosa pine contains outerwood with relatively high stiffness that could be suitable for structural products. However, when assessed using wood stiffness, the trees take a long time to reach maturity (~50 years) and thus the corewood proportion is large. AV measurements are a good way to assess variability within and among stands and thus could be employed to segregate the resource by expected stiffness values. Segregation could help identify stands not suitable for structural uses and direct them toward more appropriate products.

Description: Harmonized forest area information provides an important basis for environmental modelling and policy-making at both national and international levels. Traditionally, this information has been provided by national forest inventory statistics but is now increasingly complemented with remote sensing tools. Reliability and harmonization of both sources are important aspects to ensure comparability and to enable the development of international forest scenarios. Initiatives with the purpose of harmonization of forest area for both sources are currently ongoing. Nevertheless, all forest area estimates contain uncertainties, which must be quantified and included in the error budget. This is a prerequisite for combining and comparing data. The purpose of this study is to compare, taking into account uncertainties, forest area estimates for year 2000 derived from four different harmonized satellite-based maps, covering Europe with recognized official forest statistics. It was found that the major cause of disagreements between official statistics and map-derived forest area originates from the general issue of accounting for land cover instead of land use. Consequently, CORINE land cover results had the best accordance with official statistics due to its focus on land use. The other maps overestimated the forest area in mountainous countries and showed underestimation in countries with large forest area or open forest formations.

Description: A sampling strategy to be used with multi-phase forest inventories is proposed for assessing scattered trees outside the forest on large territories. The first phase is carried out by means of a systematic search over the area to be inventoried. The area is partitioned into regular polygons of the same size and points are randomly located, one per polygon. Subsequently, in the second phase, the land cover class of the first-phase points is determined by very high-resolution remotely sensed imagery and a sample of points are selected from each land cover stratum. Then, the number of trees outside the forest lying within plots at the sampled points is recorded on the imagery. Finally, in the third phase, a subsample is selected from the second-phase samples of each stratum and the biophysical attributes of trees within plots are measured in the field. Approximately unbiased estimators of abundance and of totals and averages of biophysical attributes are achieved in the second and third phase, respectively, together with the estimators of the corresponding variances. A simulation study is performed in order to assess the accuracy of the strategy under random and aggregated distributions of trees. The sampling errors achieved in the second phase using sampling fractions of ~0.3 per cent of trees vary from 6 to 13 per cent, whereas the errors achieved in the third phase using sampling fractions of ~0.15 per cent vary from 15 to 31 per cent. The results obtained from three case studies carried out in Italy confirm the accuracy levels achieved in the simulation.

Description: A new model for computing the allowable cut for uneven-aged stands is described. The model is focused on the Gini index against basal area and the target structure of stand volume on diameter classes, assumed to be achieved by the end of transformation period from even-aged to the uneven-aged structure. The real structure of the stand is characterized by a given Gini index while the target structure is characterized by a benchmark Gini index. In order to determine the benchmark Gini index, the model allows the establishment of target structure of the stand based on a new idea: target structure of trees number in diameter classes for a particular stand corresponds to a certain target distribution of volumes on diameter classes. According to the difference between the two mentioned Gini indices, a certain period for directing the real structure to the target structure is further chosen while the computation of the allowable cut is based on the assumption of Gaussian distribution of volume against diameter classes. Eventually, the computation of allowable cut takes into account the stand growth, the differences between the real and the target growing stock, the adopted transformation period and the management goals.

Description: A hybrid jet-pump CO 2 compression system that may enhance system COP and reduce the environmental impact of transport refrigeration is analysed. At an evaporator temperature of –15°C, an ambient temperature of 35°C and a generator temperature of 120°C, COP increases from 1.0 to 2.27 as subcooling increases from 0 to 20 K. Compressor work is reduced by 24% at 20 K subcooling. The optimum degree of subcooling was ~10 K for the operating conditions examined. COP is improved while the size of heat exchangers required to operate the jet pump are minimised with respect to the overall weight of the system.

Description: Libya has a growing demand for electricity and presently generates almost all of its electrical energy using fossil-fuelled generation plant. An opportunity exists to use the naturally high solar radiation resource that occurs in the south of the country to meet this demand with a renewable energy source. This paper describes the design of a 50 MW photovoltaic (PV) power plant which has been modelled on the conditions pertaining to Al-Kufra. The general energy situation within Libya is described, along with the solar conditions at the proposed location of the power plant. An HIT type PV module has been selected and modelled. The effectiveness of the use of a cooling jacket on the modules has been evaluated. The results show an average increase in efficiency of 0.6%; however, this is not considered to be a justifiable expense. The optimum tilt angle and array layout have been evaluated for the proposed site. The projected energy output has been determined to be 114 GWh per annum with a payback time of 2.7 years and a reduction of CO 2 pollution by 76 thousand tonnes per year. It is recommended that very large-scale PV plants of this type are installed within Libya for the sake of benign environmental impact and diversification of the electrical generation mix.

Description: In this paper, a thorough review of the available literature on photovoltaic/thermal (PV/T) systems is presented. The review is performed in a thematic way in order to allow an easier comparison, discussion and evaluation of the findings obtained by researchers, especially on parameters affecting the electrical and thermal performance of PV/T systems. The review covers a comprehensive historic overview of PV/T technology, detailed description of conventional flat-plate and concentrating PV/T systems, analysis of PV/T systems using water or air as the working fluid, analytical and numerical models, simulation and experimental studies, thermodynamic assessment of PV and PV/T systems and qualitative evaluation of thermal and electrical outputs. Furthermore, parameters affecting the performance of PV/T systems such as glazed versus unglazed PV/T collectors, optimum mass flow rate, packing factor, configuration design types and absorber plate parameters including tube spacing, tube diameter and fin thickness are extensively analyzed. Based on the thorough review, it can be easily said that the PV/T systems are very promising devices and PV/T technology is expected to become strongly competitive with the conventional power generation in the near future.

Description: In this study, an experimental research concerning the effects of passive cooling on performance parameters of silicon solar cells was presented. An aluminum heat sink was used in order to dissipate waste heat from a photovoltaic (PV) cell. Dimensions of the heat sink were determined considering the results of a steady-state heat transfer analysis. The experiments were carried out for different ambient temperatures and various illumination intensities up to 1 sun under solar simulator. Experimental results indicate that energy, exergy and power conversion efficiency of the PV cell considerably increase with the proposed cooling technique. An increase of ~20% in power output of the PV cell is achieved at 800 W/m 2 radiation condition. Maximum level of cooling is observed for the intensity level of 600 W/m 2 . Performance of PV cells both with and without fins increases with decreasing ambient temperature.

Description: High-temperature thermal storage (HTTS) in soils is a promising energy-saving technology for space heating of buildings. Based on a laboratory experimental setup using a vertical borehole heat exchanger (BHE), dynamic changes of the soil temperature and moisture content during the thermal storage process are studied. Effects of the heat injection temperature and initial moisture content on the thermal performance of the BHE are analyzed. The results show that at the first thermal storage stage, the soil temperature and moisture content near the heat source may appear a temporary peak. Its occurrence depends on the initial soil moisture content, the heat injection temperature and the distance from the heat source. As the heat injection temperature increases, the heat transfer rate of the BHE increases greatly. As the initial soil moisture content increases, the temperature profile near the BHE tends to be deviated from the results predicted by heat conduction, thereby influencing the thermal performance of the BHE. The present results can provide useful guidelines for the design of an HTTS system.

Description: The thermal performance of a horizontal-coupled ground-source heat pump system has been assessed both experimentally and numerically in a UK climate. A numerical simulation of thermal behaviour of the horizontal-coupled heat exchanger for combinations of different ambient air temperatures, wind speeds, refrigerant temperature and soil thermal properties was studied using a validated 2D transient model. The specific heat extraction by the heat exchanger increased with ambient temperature and soil thermal conductivity, however it decreased with increasing refrigerant temperature. The effect of wind speed was negligible.

Description: CO 2 solid–gas two-phase flow is investigated in an ultra-low temperature cascade refrigeration system. Visualization test shows that dry ice sedimentation occurs in low mass flow rate. The sedimentation also occurs at low condensation temperature and low heating power input. On the basis of the present investigation, it is found that the present ultra-low temperature cascade refrigeration system works better at a heating power input above 900 W and condensation temperature above –20°C. Under suitable operating conditions, the present ultra-low temperature cascade refrigeration system has shown the capability of achieving an ultra-low temperature of –62°C continuously and stably.

Description: Nowadays, many working environments are located within facilities that are not visually connected with the exterior. This is due to the new architectural paradigms as regards the design, based on the possibility to substitute natural light for artificial lighting even in daytime. Accordingly, the need of reducing energy costs and the user's wish to optimize lighting and visual comfort levels raises the option of innovative natural lighting systems implementation. For a luminous retrofitting case, located in Mendoza, Argentina, a specific methodology used determined that the more adequate natural lighting strategy would be redirecting direct sunlight, working on the reflected light design. The methodology proposed is formed by an analysis of the initial situation, conditions modelization and design resolving proposals, through luminous evaluation, real and virtual scale model construction, and performance evaluation using heliodon and simulation software. This work points to use natural lighting to reduce energy consumption and get better luminous ambient through the application of a low-cost daylighting system. In the mentioned case, strategies of redirection of the solar component capable of optimizing indoor lighting levels up to a 40% were applied.

Description: This paper aimed to numerically investigate the performance comparison between counterflow and crossflow heat exchangers for indirect evaporative air cooler. Simulation results indicate that cooling performance difference between the two configurations considerably depends on the configuration structure of heat exchangers, the inlet air status and the mass flow rates of primary and secondary. Among types of the cross-sectional shape considered in this paper, the counter configuration with rectangle channels which has a length-to-width ratio of 16:1 can provide the best cooling performance. The wet bulb effectiveness of counterflow configuration is about 7% greater than that of crossflow configuration with increasing inlet air temperature on average. The higher the inlet air temperature, the bigger the EER, cooling capacity and supply air temperature difference between the two configurations. With increasing relative humidity, the two configurations keep an average wet bulb effectiveness difference of 7.1%. The wet bulb effectiveness difference between the two configurations narrows down from 8.3 to 5.3% with increasing air velocity.

Description: Harvesting models are needed within simulation studies to assess ‘business as usual’ scenarios in future stand development. Such models require data from repeated observations addressing the removals as they are based on specific silvicultural management regimes. The purpose of this paper was to develop and apply a harvesting model for uneven-aged single-tree forest management based on data from the forest company ‘Forstbetrieb Ligist, Souveräner Malteser Ritterorden’ in Austria. This company has been known for its transition from even-aged to uneven-aged forest management since the 1930s. Our harvesting model comprises two logistic functions to simulate a single-tree selection process: (1) predicting the probability of harvesting and (2) removal. The set of equations are tested and implemented in the tree growth model MOSES (MOdelling Stand rESponse). MOSES is used as a diagnostic tool to assess different forest management regimes. In this study, we are specifically interested in (1) evaluating the model by comparing predicted and observed removals and (2) predicting future stand development considering the current management practices—the business as usual as it can be derived from the harvesting model. The results suggest that in combination with MOSES, our model correctly mimics the growth development over time since no systematic trends between predicted and observed diameter growth at breast height classes are apparent. Furthermore, it is evident that by applying the current plenter harvesting strategy, a constant stand basal area of ~35 m 2 ha –1 will be achieved.

Description: The article summarizes results obtained from several field experiments, measured in uneven-aged forests during a long period; from the 1930s until the present. Experiments have been established in both Norway spruce- and Scots pine-dominated stands. The purpose is to evaluate the feasibility of uneven-aged forest management under Finnish conditions and compare uneven-aged management to the current even-aged forestry. The analysed datasets demonstrate relatively rich regeneration under many types of tree canopies. The number of stabilized (height 0.1–1.3 m) spruce seedlings does not always correlate with the stand density. The amount of small labile (height 〈 0.1 m) spruce seedlings may even increase with increasing stand volume. Contrary to spruce, the regeneration of birch and pine decreases with increasing stand volume. The yield comparisons show that uneven-aged stands have often grown faster than even-aged stands with the same post-cutting stand density. High thinnings have resulted in better volume increments than low thinnings. Recent studies show that uneven-aged management is more profitable than even-aged rotation forestry (RF), especially with high discount rates. Uneven-aged management seems to be superior to current even-aged RF also with respect to environmental and multifunctional aspects, such as carbon sequestration, bilberry yield, structural diversity and scenic values.

Description: The selection method applied in shade-intolerant pine stands in the southern United States has been shown to be an effective method of uneven-aged silviculture, but it is becoming less frequently practiced for a variety of reasons. Economically, the high value of standing timber puts fully stocked uneven-aged pine stands at risk of liquidation if the timberland is sold. This is increasingly common on private lands in the southern United States, where forest industry landowners have been selling timberlands over the past two decades to timber investment management organizations and real estate investment trusts. Ecologically, the benefits of open woodland habitat restoration in southern pines are being optimized by use of prescribed burning, which is much more adaptable to even-aged silvicultural systems such as the shelterwood method than it is to the selection method. But uneven-aged silviculture will be important in the twenty-first century; its values centre around the ability of uneven-aged stands to resist and especially to recover from exogenous disturbance events, as well as the opportunity for frequent establishment of new regeneration cohorts under changing climatic conditions.

Description: While sustainable forest management (SFM) policy processes are well developed, implementation on the ground remains a challenge. Given the diversity of biophysical conditions, economic histories and governance systems on the European continent, regionally and temporally adapted and adaptive solutions are needed for both social and ecological systems. To illustrate this, we apply (1) a biographic forest and woodland history approach to central Sweden’s Bergslagen region, where boreal sustained yield forestry was widely applied first and (2) a comparative case study approach using five European landscapes that represent different forest history phases in Scotland, Germany, Ukraine and Russia. Additionally, we illustrate the need to learn from reference landscapes for natural forest and cultural woodland systems such as in economically remote regions in Romania, Russia and on the Iberian Peninsula. We conclude that there is great opportunity for innovative knowledge production about both governance and management for different SFM dimensions based on comparisons among concrete landscapes. In addition, there is a need to develop local place-based social learning processes that are characterized by a focus on a geographical area, commitment to SFM policy visions and collaborative approaches to development that include both ecological and social systems.

Description: The relationships between climatic variables, soil parameters, tree nutrition and site index (SI) were examined in 30 chestnut coppice stands in Asturias, the region with the largest area of chestnut coppice in north-west Spain. SI was estimated from a top height projection equation for this species. A soil sample was obtained at 0- to 20-cm depth and several leaves were collected from the upper zone of the dominant trees in each plot for further analysis. Chi-square automatic interaction detection and parametric regression techniques were used to determine the key factors affecting SI. According to the regression tree and the parametric regression model for all variables, the extractable Mg in the soil and mean temperature of the warmest month were the most important variables explaining SI in the region. Elevation and foliar concentrations of phosphorus were not significant factors in the parametric regression analysis (although considered key factors when foliar nutrients and physiographical variables were analysed separately). The results show the importance, for chestnut growth, of site selection and balanced fertilizer treatment consistent with the soil requirements of the species.

Description: The identification of past insect outbreaks is often determined using a comparison of host/non-host tree ring growth chronologies. Yet this may be a problem when non-hosts are either affected by the outbreaking insect or when the growth of host and non-host trees does not respond similarly to the same climatic factors. We investigate the use of a blind source separation method to identify past outbreaks. This method, used in neurology and called independent components analysis (ICA), directly identifies disturbance patterns. We analysed the tree-ring data from papers dealing with insect outbreaks. These papers focus on western spruce budworm, pandora moth and Douglas-fir tussock moth outbreaks. We compared the results of the original analyses, conducted using the host/non-host approach, with results from ICA. We detected the outbreaks identified in the original papers. However, the start and end dates for the outbreaks were different in 75 per cent of the ICA analyses. On the other hand, we were able to detect growth reduction in non-host Ponderosa pine chronologies as well as increased growth during outbreak periods. Since conventional methods may be less robust when the growth of non-host trees is affected, the ICA may provide a powerful new method to identify outbreaks in such situation.

Description: To implement policies on sustainable forest management (SFM), there is a need to satisfy economical, ecological and socio-cultural sustainability objectives. Due to a long history of sustained yield wood production to satisfy the needs of the forest industry, clearfelling management systems are used in ~96 per cent of managed forests in Sweden. To satisfy the intentions of contemporary forest and land use policies, uneven-aged forest management systems as a complement are currently debated. We interviewed local forestry stakeholders in the Swedish boreal forest region’s north and south about their views on and attitudes towards different forest management systems’ contribution to SFM. Most stakeholders were generally negative to the use of uneven-aged system for sustained yield wood production but saw advantages for ecological and socio-cultural dimensions of SFM. To encourage the use of even-aged cohort and uneven-aged systems to satisfy all dimensions of SFM, there is a need for improved communication, education and public awareness. This could ultimately lead to a more constructive and less heated debate. In addition, there is a need of more empirically based knowledge about uneven-aged and cohort forest management systems’ pros and cons when it comes to satisfying economical, ecological and socio-cultural objectives.

Description: There is a need for a better understanding of the primary role of macronutrients in Aleppo pine stock quality and for producing larger nutrient-loaded stock, which may be challenging for inland nurseries. The influence of nursery location and fertilization on nursery culture, growth, allometry and seedling quality of Aleppo pine was studied in seedlings cultivated over the 2006 growing year. Fertilization treatments considered how a K enrichment performed over common programs currently being practiced and divided into three levels of K/N ratio: 0.63–0.89 (normal), 1.81–1.89 (high), and 2.25–2.53 (very high). Results showed that fertilization had a minor effect on seedling growth and allometry in comparison with location, which was the governing factor. However, fertilizing treatments significantly affected final seedling attributes, which has its origin on the early treatment differences that were kept up to the end of culture. Higher nutrient supply treatments produced the highest nutrient concentration in seedlings but they were associated with lower fertilization efficiencies. Fertilizer efficiency was approximately twofold in the coastal nursery for the three macronutrients, although concentration was higher in the inland nursery due to lower seedling growth. It is concluded that warmer regions are more suitable for producing large stock more efficiently.

Description: Based on a literature review and on a new bioeconomic modelling approach, we investigated whether or not clear-cutting and mono-species forests are the optimal silvicultural strategies under the presence of risk. The model reflects a risk-avoiding attitude and builds upon portfolio theory. The selected tree species and the timing of regeneration harvests constitute a total of 22 management alternatives. Optimal area fractions of the alternatives were combined at the stand level to find the maximum value at risk (VaR, annualized net present value exceeded with probability of 0.99). Relevant uncertainties were integrated via Monte Carlo Simulation and bootstrapping. The results showed a maximum VaR for a highly diversified treatment combining 42 per cent Norway spruce and 58 per cent European beech and included area fractions with regeneration harvests from age 50 to 120 years. This treatment avoids clear-cutting and a mono-species forest composition. It uses tree species diversification and extends the regeneration period over 70 years to diversify hazard and price risks. The resulting scenario may be called ‘near-natural’ and emerges as the optimal choice, particularly for cautious, and thus risk-avoiding forest owners who do not have the opportunity to diversify risks by means of large-scale forest properties.

Description: Housing associations (HAs) are responsible for building and managing approximately one-third of affordable homes in Scotland. The adoption of low carbon technologies (LCTs) by HAs presents an area that could potentially help towards reducing the carbon footprint of affordable housing and the fuel poverty of tenants. This research thus explores the issues pertaining to the adoption of LCTs from the perspective of two Scottish HAs. Semi-structured interviews were conducted with selected members of the management team in both HAs. The empirical findings revealed that HA-related issues (such as organization culture, being a learning organization and training) and tenant-related issues (such as social cohesion, change in behaviour and training) can both impinge on the adoption of LCTs in HAs. It is contended that there is a piecemeal adoption of LCTs and if mass adoption is to be realized, this will require a nationwide programme that is aimed at supporting the adoption of LCT, in addition to building the skills capacity of the construction industry which is seemingly ill-prepared.

Description: Focusing on the ‘worst-case scenario', a modelling study was carried out to examine whether a low cost ventilation solution could provide basic comfort in a specific atrium-building design. This study combined dynamic thermal modelling (DTM) and computational fluid dynamics (CFD) in investigating how thermal conditions, namely the air movement and temperature distribution within an atrium responded to the side-lit form and other changes of design variables such as inlet to outlet opening area ratios and also the outlet's arrangement. The predicted temperature distribution, airflow patterns and comfort indices would provide a better understanding how the design variables affect thermal condition and comfort within the atrium, particularly at the occupied areas under a low cost ventilation solution—pressurized ventilation. The simulation results revealed that sufficiently higher inlet to outlet opening area ratio (i.e. n 〉 1) could improve the thermal condition on the open corridors, the occupied areas, even on high levels; while with an equal inlet to outlet opening area ratio (i.e. n = 1), changing the outlet's arrangement (i.e. location and configuration) did not significantly affect thermal condition. The practical aspect of this study is 2-fold. First, the low cost ventilation solution using exhaust air from surrounding fully air-conditioned rooms could provide acceptable thermal comfort at the open corridors/walkways surrounding the atrium. Secondly, combining a DTM and CFD can be an effective tool to test various design options to achieve an optimal solution. The parametric presented here could be used in similar studies aiming at optimize environmental engineering solutions that balance comfort and cost.

Description: Most existing nuclear power plants in North America are typically water-cooled and operate at 250–500°C. For this temperature level, the copper–chlorine (Cu–Cl) cycle is one of the most promising cycles that can be integrated with nuclear reactors for hydrogen production by decomposing water into its constituents. In this study, we analyze the heat exchangers in the Cu–Cl thermochemical cycle so as to enhance heat transfer effectiveness and thereby improve the cycle efficiency. The thermal management options for internal and external heat transfer are studied and heat recovery opportunities are investigated and compared. Each heat exchanger in the cycle is examined individually based on the chemical/physical behavior of the process, and the most appropriate options are recommended. A thermodynamic analysis and associated parametric studies are performed for various configurations to contrast their efficiencies and effectivenesses.

Description: The flaring of oil-associated gas continues to generate insidious environmental and energy consequences against efforts toward sustainable development for Nigeria. This study compared some of the economic benefits lost due to flared gas at flow stations with fuelwood energy consumption. The objectives were to assess comparative cost suffered by host communities, estimate greenhouse gases emissions of burnt-off gas and evaluate possible effects of post-global financial meltdown support policies on climate change. Parameters for evaluating the environmental and energy impacts were measured directly or collected from flow stations through opinion surveys and meetings. An inventory of the motors, voltages and power ratings of the machines used at the flow stations was made, with a view to quantifying the energy involved in drilling operations. For estimation of health risks and gaseous emissions, SIMPACTS method was used. Results from the study show that an annual average of 2040 MJ of fuelwood is consumed in Nigeria, 77.3% of the sourcing is done by children and the time spent in fuelwood trips is between 4 and 5 h, at a frequency of three to four times a week. This amount of fuelwood consumed examined alongside 2.5billion standard cubic feet of gas flared per day, revealed the quantity of energy that ought to be saved and related avoidable extreme weather conditions that prevail in Nigeria. Therefore, gas flaring violates the tenets of sustainable development and seriously contributes to global warming. In conclusion, flare down can be achieved by utilizing micro-gas turbines, re-injection and pursued as part of a new agenda for responsible governance in Nigeria.

Description: In order to investigate the operation performance of ground-coupled heat-pump (GCHP) system, an analytical simulation model of GCHP system on short time-step basis and a computer program based on this model to predict system operating parameters are developed in this study. Besides, detailed on-site experiments on GCHP test rig installed in a temperate region of China are carried out. The temperature distributions of borehole as well as ground around borehole at different depths are evaluated. Operation parameters of GCHP system such as circulating water temperature, heat rejection into ground and system power consumption when the system operated in intermittent and continuous modes are investigated. The accuracy of proposed simulation model is validated by experimental data. The advantage of GCHP technology in energy efficiency over other conventional air-conditioning systems is proved to be obvious and the performance of GCHP system is found to be affected by its operation modes.

Description: Sorption heat pumps based on monovariant reactions, such as ammonia-salt systems, can operate at low driving temperatures and achieve high power densities in comparison with multi-variant sorption systems. The disadvantage of monovariant systems, however, is the inflexibility towards required temperature levels. Where multivariant systems scale over a large range of temperatures, for the monovariant system, the temperature range is limited by the discrete transition from (fully) adsorbed to desorbed state. To increase flexibility towards changes in operating temperatures of the monovariant sorption systems, the extension of such systems with a compressor has been studied. Focus of this research is on the use of ammonia salts for type II heat pump for upgrading low temperature industrial waste heat to low–medium pressure steam. At ECN, a system based on LiCl–MgCl 2 ammonia reactions has proved to achieve sufficient temperature lift (〉50°C) and cyclic stability (〉100 cycles) but requires a minimum temperature of 120°C for proper operation. To add flexibility to this system, i.e. to be able to use waste heat below 120°C, the performance of a hybrid variant containing both thermally driven sorption reactors and a compressor has been evaluated. This evaluation focuses on extension in temperature range, and exergy efficiency and economic consequences of such a hybrid system. In addition, the possibility to use other ammonia-salt combinations has been investigated. The conclusions are that hybrid systems can reduce primary energy consumption and be economically feasible. It also shows that salt combinations other than LiCl–MgCl 2 could be more suitable for a hybrid thermo-chemical adsorption–compression system.

Description: Studies of old-growth forests are becoming increasingly important for the improvement of silviculture and for understanding environmental changes. However, in Europe such forests are rare, fragmented and influenced by millennia of human activity. Comparative studies of old-growth forests across Europe are needed to improve knowledge on how direct and indirect anthropogenic factors influence their structure. We analysed structural dynamics in 15 silver fir-beech-Norway spruce old-growth forests in Slovenia, Croatia, Slovakia and Bosnia-Herzegovina. Changes in diameter distributions, stand parameters and regeneration were analysed at intervals of 6–116 years. Most diameter growth at breast height (d.b.h.) distributions approximated a rotated sigmoid shape, which could be explained by differences in growth and mortality rates with respect to d.b.h. class and by disturbance history. Our results suggest that different disturbance types are likely to cause different changes in d.b.h. distributions. For example, overbrowsing, canopy dieback of silver fir and windthrow decreased the density of small, intermediate and large-diameter silver fir, respectively. The slopes of the fitted diameter distribution curves were steeper for beech than for silver fir, which could be explained by their different life strategies. Despite disturbances, growing stocks remained stable over the long term. A synchronous silver fir decline was confirmed. It was more pronounced in Slovenia and Slovakia, both of which experienced more SO 2 pollution and had higher ungulate densities. The silver fir sapling stage was often totally absent in both countries. Our results suggest that anthropogenic disturbances, especially air pollution and overbrowsing (resulting from human-induced increases in deer density), significantly influenced the coexistence of silver fir and beech; asynchronous, patchy changes in species mixture have been replaced by large-scale synchronous changes.

Description: The development of uneven-aged forest management in the Dinaric region (north-west Balkans) is reviewed. Uneven-aged silviculture has been the major silvicultural system in the region since regular forest management began in the second half of the nineteenth century. Regular forest management in former virgin forest areas began as selection forest management mainly because of the awareness of the importance of multilayered continuous forest cover for preventing soil erosion on carbonate substrate. The observed period of more than 100 years has seen several changes to uneven-aged forest management ranging from the complete domination of rigid selection forest management to the gradual acceptance and eventual domination of the irregular shelterwood system and finally to the acceptance of freestyle forest management, which is presently practiced in the Slovenian part of the Dinaric region. Freestyle silviculture combines practices of different silvicultural systems. By using this system, consideration for site conditions and heterogeneous stand dynamics at small spatial scales is possible. In the observed period, some stand parameters of Dinaric forests have changed substantially. Growing stock has increased significantly, the number of large-diameter trees has increased and alternation of the main tree species (silver fir and European beech) has occurred. The development of uneven-aged forest management is described and its prospects are discussed.

Description: We estimate a suitable strip-gap arrangement in Japanese cedar ( Cryptomeria japonica ) plantations to promote the growth of beech ( Fagus crenata ) seedlings and control dwarf bamboo ( Sasa kurilensis ) in mountainous areas using a hemispherical model and United States Geological Survey Digital Elevation Model (DEM). Clarification was also sought on whether the gap arrangement should be altered with topography and original stand structure. Nine modelled plantations were established by combining tree inventory and DEM data from three C.japonica plantations. We simulated spatial and temporal variations in photosynthetic photon flux density in stands 5 years after strip-gap creation under six scenarios for each modelled stand and integrated the light responses of F. crenata seedlings and S. kurikensis into the model. Finer strip-gap mosaics with gap width narrower than half the tree height inhibit the growth of S. kurikensis and provide a wider area suitable for F. crenata growth. Our simulation indicated a suitable strip-gap arrangement should be based on the stand structure but not necessarily on topography. However, it indicated that the possible range of practical gap arrangements changed with topography. The decision-support model for gap arrangement used in this study combined with DEM data provides flexible gap creation options adaptable to specific plantations in mountainous areas.

Description: Almost all commercial forests of Finland are simultaneously used for timber production, outdoor recreation and biodiversity maintenance. For the past 60 years, the official line of silviculture has been even-aged management. However, uneven-aged management and other forms of continuous cover forestry are gradually gaining popularity and also official acceptance. This study analyzed variable density thinning (VDT) in the context of uneven-aged management of Norway spruce ( Picea abies L.Karsten) stands. The aim was to find economically profitable management systems, which would result in forests that are good for recreation and biodiversity maintenance. The stand compartment was divided into cutting segments and only one segment was harvested at a time. When economic profitability was maximized as the sole management objective, 15-year cutting cycle with uniform thinning (UT) was the optimal management system. All trees larger than 19 cm in diameter at breast height (all saw log-sized trees) were removed in the cutting. When a continuous presence of large trees was required, VDT was clearly more profitable than UT. In VDT, all large trees were removed from the thinned places but there were large trees in the segments that will be cut in the next logging operation. The optimal cutting cycle (interval between successive cuttings in the same place) of VDT was 20–30 years when large trees were required in the post-cutting forest. Several combinations of the length of cutting cycle and number of cutting segments were nearly equally profitable. Profitable options were, for instance, to divide the stand into four cutting segments each cut at 20-year interval or three segments each cut at 30-year interval.

Description: We aimed to assess the potential of the natural regeneration of broadleaved tree species in relatively dense and approximately 30-year-old hinoki cypress ( Chamaecyparis obtusa ) plantations on the Pacific side of Shikoku in south-western Japan. The composition and size structure of naturally established canopy and sub-canopy species were investigated in 18 plots at two hinoki cypress plantation sites, namely Okuono and Karakawa (OKU and KRK). Local variation in the density and species richness of naturally established stems were analysed in relation to overstorey stand structure, local topography, soil properties and understorey vegetation. OKU was noteworthy for its relatively high proportion of sub-canopy species and L-shaped height distribution of saplings (〉200 cm), while KRK was characterized by a wider range in the height distribution of saplings and a low density of seedlings (〈200 cm) despite the relatively higher dominance of canopy species. This was attributed to the differences in the characteristics of component species and the thinning history of the sites. The density and species richness of the saplings at both sites and the seedlings at OKU were higher in plots with lower mean heights of hinoki cypress and higher soil C/N ratios. These results suggest that variation in the growth of hinoki cypress, which is related to the soil nitrogen status, brings about local variation in the regeneration potential at these sites.

Description: Uneven-aged silver fir-European beech forests in Slovenia were studied to investigate the dynamics of their structure and composition in three different study areas over the last century, with a particular focus on silver fir dynamics. The study used current and archival data from forest inventories and historic forest management maps for a period of ~110 years. The dynamics of several structural and compositional parameters of the forest stands were also examined using a stand volume index, the Gini coefficient and a recruitment rate index. Substantial changes in diameter growth at breast height structure, stand volume, tree size diversity and tree species composition were documented during the observed period. Additionally, silver fir underwent large-scale changes. Significant differences, as well as some similarities, in forest stand dynamics were observed on a regional spatial scale. These dynamics are underpinned by a complex array of natural and anthropogenic factors; past forest use and the silvicultural systems applied, the impact of large ungulates and site characteristics seem to play important roles.

Description: The aim of this study was to assess the effect of cytokinins not commonly used for shoot induction from zygotic embryos of Pinus radiata D. Don. The influence of in vitro shoot and root induction treatments on the subsequent ex vitro development of the regenerated plants was also tested. Embryos were cultured with benzyladenine (BA), thidiazuron (T) and two cytokinins not previously assayed in radiata pine organogenesis ( meta -topolin (m-T) and zeatin (Z)) in a range of concentrations and induction periods. Shoot induction treatments were assayed in seeds from different geographical origins to obtain wider conclusions. We analysed the effect of these cytokinin treatments on in vitro rooting with different auxins ((indole-3-butyric acid (IBA) and 1-naphtalene acetic acid (NAA)) and the traditionally used mixture. After in vitro rooting, the plantlets were acclimatized and their ex vitro behaviour was evaluated. Shoot induction treatments with 1 μM BA for 2 weeks, 4.4 μM BA for 3 weeks or 1 μM Z for 3 weeks were more effective than the other treatments. An interaction between in vitro shoot and root induction treatments was observed. IBA was more efficient for plant production because the explants rooted in this auxin had better survival rates in the greenhouse.

Description: The well-being of people living in forest-dependent communities has been studied extensively, but little research has explored how this relationship has changed over time. Some theories suggest that regional differences in well-being should decrease, through the flow of capital and labour, while other work suggests that these inequalities will grow. Our research uses Census of Canada data at the census subdivision level at 5-year intervals between 1986 and 2001 to describe regional differentiation in the relationship between employment in forest sectors (logging, services, pulp and lumber) and unemployment and median family income as indicators of well-being. We found general declines, which varied somewhat by region, over time in forest dependence across the regions and changing composition of the forest industry across these sectors. The relationship between forest dependence and well-being over time varied by region, largely tied to intra-industry sector shifts.

Description: Continuous cover forestry (CCF) aims at enhancing stand structural diversity and favouring natural regeneration. To give guidance on how to manage a CCF stand to achieve seedling growth below canopy, an estimate of light transmittance is required. So far, in the UK, only stand-level parameters have been used by managers to predict the understorey light in CCF stands. We assessed a UK Sitka spruce stand undergoing transformation to CCF and measured canopy transmittance using hemispherical pictures. Stand-level characteristics were found to be highly stand specific and not appropriate to predict seedling growth in CCF stands. We parameterized a detailed light model (4C-A-RTM) and a simple one-layer turbid medium model (BL). A sensitivity analysis was performed to test the effect of key stand structural parameters on the modelled transmittance. Measured transmittance from hemispherical photographs was used to validate the models. Both models tended to underestimate canopy transmittance but were positively related to current-year growth of the below canopy seedlings ( R 2 = 0.92, P 〈 0.001). Comparison of the two models showed that the 4C-A-RTM provided a better estimation of light transmittance across observed canopy structural differences. Furthermore, the inclusion of stand characteristics in the 4C-A-RTM is likely to confer greater applicability across stands.

Description: Since the 1970s, a long-term research project has been conducted to monitor the changes in primary productivity of Chinese fir plantation at Huitong Ecosystem Research Station, Hunan, China. Standing biomass and net primary productivity (NPP) of the plantation were investigated at four times (7, 11, 14 and 18 years old) in two successive rotations on the same site. The mean individual tree biomass and stand biomass in the second rotation were reduced by ~18, 17, 7 and 3 per cent in 7-, 11-, 14- and 18-year-old stands, respectively, compared with the first rotation. In the first rotation, annual NPP was higher in the 7-, 11- and 14-year-old stands, but lower in the 18-year-old stands, compared with those in the second rotation. The proportion of biomass in stem, canopy (branch and leaf) and root was ~80, 13 and 7 per cent and 64, 20 and 16 per cent at the later stages of the stand development (≥14-year old) in the first and second rotations, respectively. The results suggests that relative large dry matter found in root systems in the second rotation increases the capacity of Chinese fir to exploit the soil for nutrient and water resources, which facilitates tree growth and productivity.

Description: Knowing the abundance of small trees is necessary for accurate calculation of gross production, total carbon and/or biomass of forest stands. The abundance of small trees can also be used to predict ingrowth into larger tree diameter classes. We present a method of predicting numbers of trees in small diameter classes using diameter distributions of larger trees in stands. A truncated two-parameter Weibull distribution was fit to large tree diameters (diameter at breast height (d.b.h.) ≥ 9.0 cm). These parameters were then used to predict the number of small trees in d.b.h. classes smaller than 9.0 cm. Three methods of predicting densities of small trees were used: (1) an extrapolation of the truncated Weibull to a full two-parameter Weibull distribution; (2) a modification of the Weibull using an empirical estimate and (3) a combined approach. While the full two-parameter Weibull distribution generally fitted the distribution of small trees, densities were typically under-predicted. The empirical method (i.e. method 2) produced the best predictions of small tree densities, with a root mean square error of 132 trees h –1 (28 per cent of mean small tree density). Overall, predicting the distribution of small trees using the distribution of large trees worked very well in this study.

Description: As a result of escalating demands for wood and parts of trees for use as biofuels and energy generation, there is growing interest in increasing forest biomass production. The objective of this study, therefore, was to investigate whether the physical properties and modulus of elasticity (MOE) of Scots pine ( Pinus sylvestris L.) juvenile clearwood change in response to different silvicultural treatments (pre-commercial thinning and fertilizer application) in 22- to 25-year-old trees. We achieved this by measuring short-term mechanical properties and using X-ray densitometry. The results show that the MOE and latewood density were not affected by any treatment. The earlywood density and the percentages of earlywood and latewood were affected by the treatments. Fertilization increased ring width and the percentage of earlywood but decreased the percentage of latewood. Pre-commercial thinning also increased ring width and the percentage of earlywood, and decreased the percentage of latewood, but did not affect earlywood density. Furthermore, our results suggest that the MOE of wood is not affected by the different treatments as long as the cambial age and ring width are the same and that fertilization should be considered as a factor that increases the site index where intra-ring properties are concerned.

Description: This paper quantified the soil organic carbon (SOC) concentration, bulk density, depth and carbon (C) stocks of 24 afforested peatlands. We found that the peat bulk density does not increase with depth, as has been previously noted in the literature. The depths of each different peat type were found to vary widely with means of 192 ± 100, 145 ± 130 and 127 ± 100 cm for raised bogs (RB), high-level blanket bog (HLB) and low-level blanket bog (LLB), respectively. Based on the full-surveyed depth, we estimated carbon densities of: 1160 ± 520 Mg C ha –1 for RB peat; 775 ± 590 Mg C ha –1 for HLB peat and 705 ± 420 Mg C ha –1 for LLB peat. We found peat depth and peat type to be significant predictors of peat carbon density and present pedo-transfer functions for carbon density based on these predictors that will help to improve future peat C stock estimates. We suggest that due to the similarities between the carbon densities of the HLB and LLB, they can be analysed as one group for accounting purposes and future C stock estimates.

Description: The production of biofuels and other products from algae is a technology that is rapidly developing. This paper presents an overview of algae, its benefits over other biofuel sources and the technology involved in producing algal biofuel. The case study in this report looks at the potential of algal biodiesel, produced using power plant exhaust, to replace our current petrodiesel supply and consequently reduce greenhouse gas emissions. The results suggest that using 60% of all coal and gas power plants would allow this new fuel source to replace petrodiesel entirely and thus reduce greenhouse gas emissions by ~5%. The challenge at the present is to improve the efficiency of algal fuel production technology so as to lower the cost of algal biodiesel and thereby make it commercially competitive with petrodiesel. Researchers are currently developing various means of accomplishing this and successful commercialization is anticipated by 2018.

Description: Performance testing of solar heating systems and solar collectors according to International Standard Test procedures require sophisticated and expensive elaborate set-ups. Outdoor collector testing is not feasible in countries with widely fluctuating solar radiation conditions. Indoor testing does not give its true performance when the equipment is situated outdoors. This paper reports on a simple test procedure where the performances of the flat plate, U-tube and heat pipe natural convection solar heaters and the heat pipe force convection solar heater, which were tested on different days, were compared as if they were simultaneously tested side by side. The procedure allowed: (i) the maximum hot water storage temperature that could be achieved by the system over a long period of time without any water draw-off at all, (ii) overnight water temperature drop in the storage tank and (iii) expected end-of-day water temperature and mean system efficiency when water is completely drained down (draw-off) in the evening. Maximum temperatures reached for the natural convection heat pipe, force convection heat pipe, flat plate and U-tube system were 100, 84, 65 and 50°C, respectively. Overnight temperature drops due to standing tank loss and reverse flow were presented and found to be dependent upon initial tank temperature. By pro-rating all the results to reflect on the same area/volume ratio, the expected water temperature rise for the U-tube, forced convection heat pipe, flat plate and natural convection heat pipe systems was 13.6, 17.6, 20.6 and 28.4°C, respectively.

Description: New definitions of two-phase viscosity, based on its analogy with thermal conductivity of porous media, are investigated for transcritical capillary tube flow, with CO 2 as the refrigerant. Friction factor and pressure gradient quantifies are computed based on the proposed two-phase viscosity model using homogeneous modelling approach. The Proposed new models are assessed based on test results in the form of temperature profile and mass flow rate in a chosen capillary tube. It is shown that all the proposed models of two-phase viscosity models show a good agreement with the existing models such as McAdams et al ., Cicchitti et al ., etc. The influence of the viscosity model is found to be insignificant unlike to other conventional refrigerants in capillary tube flow.

Description: The ammonia–water absorption cycle could transfer thermal energy into chemical energy by the change in solution concentration, which low-grade heat released by industry-concentrated areas could be utilized to provide heating or cooling in the user site over long distance. No heat insulation is required for the transportation pipelines and the energy consumption is reduced greatly. The simulation researches show that thermal coefficient of performance (COP) is at 0.5 and exergy efficiency is 〉0.2 when generation temperature is at 110°C to provide cooling in summer; thermal COP is at 0.6 and exergy efficiency is 〉0.3 to provide heating in winter. Electrical COP as high as 50 could be realized if the transportation distance is 〉50 km. Therefore, the COP of the system is determined by thermal COP (nearly equal). An experimental prototype has been built to testify this theory. Thermal COP is 0.43 when chilled water at 8°C is obtained in summer. In winter, thermal COP is 0.45 when hot water at 58°C is obtained. The deviations between experimental and simulation results are ~20%. The economic assessment based on the reasonable assumptions shows that the investment cost of the transportation pipelines of a 500 MW, 50 km system could be recovered within 15 months, in which the whole system costs could be recovered within 4 years.

Description: In process industry, large amounts of surplus heat are available. Electricity production is an interesting method to recover this energy. This paper focuses on the off-design operation of the Rankine cycles and compares the behaviour of transcritical CO 2 cycles and an organic Rankine cycle (ORC) with R-123 as the working fluid. The simulations show that the ORC is more sensitive than the CO 2 cycle to reduction in available heat, and will with only small changes get droplets in the inlet of the expander. With small increments in the available heat source, the CO 2 cycle also seem to have a marginally better response without control of the process.

Description: The advantages of numerical modelling compared with experimental studies (e.g. reduced cost, easy control of the variables, high yield etc.) are well known. Theoretical studies where experimental validation is also presented provide an important added value to numerical investigations. In the present paper, experimental and computational fluid dynamics (CFD) results for a 5-kW-rated capacity steam ejector, with a variable primary nozzle geometry, are presented and compared. The variable geometry was achieved by applying a movable spindle at the primary nozzle inlet. Relatively low operating temperatures and pressures were considered, so that the cooling system could be operated with thermal energy supplied by solar collectors (solar air-conditioning). The CFD model was based on the axi-symmetric representation of the experimental ejector, using water as a working fluid. The experimental entrainment ratio varied in the range of 0.1–0.5, depending on operating conditions and spindle tip position. It was found that the primary flow rate can be successfully adjusted by the spindle. CFD and experimental primary flow rates agreed well, with an average relative error of 8%. CFD predicted the secondary flow rate and entrainment ratio with good accuracy only in 70% of the cases.

Description: Biodiesel, an alternative fuel of petroleum diesel, is mainly used to reduce the environmental impact of emissions without modifying engines. This study compares the performance and emissions characteristics of different biodiesel blends with petroleum diesel using an internal combustion engine (Kubota V3300) and following ISO 8178 standards. Two types of biodiesel, type A (80% tallow and 20% canola oil methyl ester) and type B (70% chicken tallow and 30% waste cooking oil methyl ester), were tested in this study. It was found that the performance (mainly torque and brake power) of both biodiesel fuels reduces with increasing blend ratio which can be attributed to lower energy content of biodiesel. Specific fuel consumption increases for both biodiesels compared with diesel fuel, as expected. Some of the greenhouse gas emissions were found to be higher than petroleum diesel, whereas some were lower. Overall, Biodiesel A was found to produce lower emissions across the board compared with diesel and Biodiesel B.

Description: In this work, a micro-tri-generation system integrated with a solar system is studied. A basic micro-cogeneration technology [micro-CHP (combined heat and power) system] integrating solar collectors, storage tank, micro-turbine and a thermodynamic cycle based on the organic Rankine cycle (ORC) is combined with an absorption chiller. The heat rejected at the condenser of the micro-CHP system is used for water heating (WH), and the absorption chiller is used for space cooling. Hot water from the solar storage tank is the heat source for the cooling system (absorption chiller) and the micro-CHP system. A heat exchanger is used to transfer heat from the hot water circuit to the power cycle (which uses an organic refrigerant). The micro-CHP system under analysis uses a micro-turbine and an electric generator with a power output of 5 kW. The turbine inlet temperature is 80°C and the working fluid is cyclohexane. The absorption chiller, which is a single-effect water-fired chiller, operates with a lithium bromide and water mixture, and water inlet temperature is between 80 and 100°C. The performance for different solar collector areas and tank capacities was evaluated through a numerical model. A hotel building was used as a case study and the analysis was extended throughout the cooling season, for climatic conditions of different European cities: Athens (Greece), Lisbon (Portugal), Madrid (Spain), Paris (France) and London (UK). The monthly average solar fraction was evaluated for different cases: the micro-CHP system, the cooling system and the micro-tri-generation system with the useful condenser energy used for WH. The solar fraction of the micro-CHP system was low, compared with that of the cooling system, because the efficiency of the micro-CHP system is lower than 7%. However, when the tri-generation system is considered, the monthly average solar fraction is much higher, due to the utilization of the condenser heat. The solar system, cooling system and its components were modelled with the TRNSYS simulation program. The micro-CHP system was modelled with EES software.

Description: Concentrating photovoltaic (PV) systems provide an effective way to reduce the cost of electricity production by reducing the amount of silicon required. The use of a Fresnel lens is one of the typical design options for the concentrating PV systems. Compared with a parabolic mirror, a Fresnel lens has its focus behind the lens surface. This gives a convenience for installation of PV cells and also there is no matter of shading caused by the PV cells. However, both Fresnel lens and parabolic dish concentrating PV systems need to be accompanied by a high accuracy sun-tracking system. This study presents the design analysis of a Fresnel lens concentrating PV cell which consists of a small linear Fresnel lens and a strip PV cell. A number of cells may form a modular large concentrating PV system using a single sun-tracking system. Based on the analysis of the ray path through the Fresnel lens and a current density distribution model for the PV cell, a computer program has been produced to predict the irradiance distribution on the PV cell and the distribution of current density. The results are used to determine the effect of sun-tracking deviation and PV cell position on the PV current distribution. The calculated and experimental short-circuit current and open-circuit voltage of the designed Fresnel lens concentrating PV cell are also given.

Description: In this paper, we investigate using a refrigeration scroll compressor as expander for power generation applications with a Rankine cycle. The methodology employed here has three steps: In the first step, a scroll compressor is selected from a refrigeration manufacturer catalog. Based on catalog data and our simplified model, the specific parameters of the compressor such as the built-in volume ratio and leakage coefficient are determined through mathematical regression. In the second step, the parameters and the efficiency of the Rankine cycle are determined, which use the selected scroll machine in reverse, namely as expander, without any geometrical modifications. The range of temperatures and pressures are kept the same as that characterizing the compressor operation. A simplified expander model is used to predict the efficiency of the prime mover and of the Rankine cycle. A range of working fluids are considered and compared. The expander does not operate optimally when converted from a compressor without any modifications. In the third phase, the geometry of the expander is modified with respect to the rolling angle only in order to obtain the appropriate built-in volume ratio which assures better efficiency of the Rankine heat engine. This paper also presents a parametric study in terms of geometry, working fluid and operating conditions.

Description: This paper presents the methodology, results and a discussion of thermal response tests (TRTs) performed on a multiple borehole ground heat exchanger. The ground heat exchanger consisted of nine 80-m deep boreholes. TRTs with durations between 48 and 260 h were performed on individual boreholes. Tests were analysed using common evaluation methods, and ground conductivity and borehole resistance values were determined for all nine boreholes. In addition to these parameters, the undisturbed ground temperatures were also determined for individual boreholes using multiple approaches. A sensitivity analysis was performed to analyse the effects of various test and parameter uncertainties on the ground thermal conductivity and borehole thermal resistance estimations.

Description: Recent studies have emphasized the nutritional interest of the fruits of strawberry tree ( Arbutus unedo L.), a species traditionally gathered in the Mediterranean region. Since fruit production in this species has been scarcely studied, we aimed to assess its local fruit supply in terms of fruit mass and fruit abundance. We carried out a 2-year study in two representative sites from continental and temperate regions of Central and Western Spain, respectively. Tree size, tree density and meteorological data were considered. The aged small population at Site 1 yielded 6.42 ± 1.19 kg per tree (46 ± 19 kg ha –1 ). The young large population from resprouts at Site 2, where forest management practices related to cork extraction have favoured shrubby growth forms, yielded 2.61 ± 0.42 kg per tree (539 ± 60 kg ha –1 ). Annual differences in fruit production per tree were recorded at Site 1, characterized by a Mediterranean climate with more severe continental traits than those at Site 2. This original data on wild fruit production may contribute to assessing the yield potential of this species for both sustainable use and cultivation purposes.

Description: This work investigates Aleppo pine performance under severe drought conditions according to seedling size and nutritional status, with special emphasis on potassium. The interaction of drought ameliorating measures such as hydrogels is also studied. Seven fertilization treatments applied in two nursery locations provided 14 stocklots, resulting in different seedling sizes for each nutrient concentration and vice versa. Stocklots were tested in a greenhouse experiment and a harsh site plantation experiment. In the greenhouse, seedlings given two hydrogel doses (0.01 and 0.1 per cent w/w) plus a control were allowed to dry and survival and soil moisture were measured. In parallel to this trial, the effects of hydrogel dosage, brand and soil texture on soil water properties were tested in a laboratory. Results show that large stock survived significantly better than conventionally sized stock in both experiments: 37 and 27 per cent more in the greenhouse and harsh site, respectively. Despite presenting wide variation, macronutrient concentration was not related to survival for a given size. Hydrogel effect on soil water was different according to factors, although in all cases, its effect diminished at suction tensions higher than 30 kPa. Results demonstrate the overriding effect of size over nutritional status on seedling survival in harsh environments.

Description: Balsam fir sawfly ( Neodiprion abietis (Harris)) has become a serious pest of young managed balsam fir ( Abies balsamea (L.) Mill.) stands in western Newfoundland, Canada. During 1991–2008, a total area of 561 000 hectares was moderate to severely defoliated. We quantified impacts (growth and survival) using data from permanent sample plots (PSPs) and dendrochronology and related these impacts to defoliation severity determined from aerial defoliation data, in order to provide input into a Decision Support System. We analyzed 67 Newfoundland Forest Service PSPs, selected based on severity of defoliation (classes 1–6), stand age and management interventions (pre-commercially thinned vs natural) and measured before and after defoliation (1996–2008). We used Bayesian statistics to combine information from different sources, each having their own limitations and associated uncertainty. No mortality was observed in immature plots 12 years after defoliation, but survival was 54 per cent lower in mature defoliated than in non-defoliated plots. Plots in defoliation class 1 (1 year of moderate, 30–70 per cent, defoliation) showed 22 per cent cumulative growth reduction and complete recovery to pre-defoliation growth increment after 5 years. Plots in defoliation classes 2–6 (one to three consecutive years of severe, 71–100 per cent, defoliation) had mean cumulative growth reductions of 26–40 per cent and did not recover to pre-defoliation levels even 9 years after defoliation ceased. Natural and thinned plots responded similarly to defoliation severity. These results suggest that proactive control measures need to be implemented since impacts are severe, even with only 1 year of severe defoliation.

Description: The significance of grey alder ( Alnus incana (L.) Moench.) as a fast-growing renewable source for energy and wood production has increased during the last decade. The aims of this study were to: (1) estimate the incidence of stem decay in A. incana stands, (2) measure the extent of decay within individual stems, (3) estimate the impact of decay on wood yield and (4) identify decay-causing fungi. In total, 4344 recently cut A. incana stumps were examined on 46 clearfelled areas in different regions of Latvia. The incidence of decayed stumps varied from 1 to 54 per cent. In addition, 175 living trees were cut to measure the extent of decay within the stems. The length of decay columns varied from 0.4 to 20.6 m and that of spongy rot from 0 to 18.0 m. In total, 354 isolates representing 70 fungal taxa and 1129 isolates representing 131 fungal taxa were obtained from decayed stumps and living stems, respectively. The present study shows that decay and associated fungi are important factors determining biomass production and quality in A. incana stands and that their impact should be seriously considered when cultivating this tree species in the future.

Description: Our study used ‘stand structures’ and ‘ecological indicators’ as inferences to managing dry Douglas-fir ( Pseudotsuga menziesii (Mirbel) Franco) forests for timber, biodiversity and range habitat attributes at 10–12 years after partial harvesting. Forest structures included densities and sizes of Douglas-fir and species and structural diversity of total conifers. Ecological indicators included cattle forage species in the understorey vegetation and three small mammal species: a closed-canopy specialist, the southern red-backed vole ( Myodes gapperi Vigors) and two early successional species, the long-tailed vole ( Microtus longicaudus Merriam) and heather vole ( Phenacomys intermedius Merriam). Harvesting treatments were across a gradient of historical cut, individual tree selection and patch cut sites in the upper Interior Douglas-fir (IDF dk ) biogeoclimatic zone near Summerland, British Columbia, Canada. Small mammal populations were sampled from 2006 to 2008. Closed-canopy forest structure seemed to maintain populations of red-backed voles in the harvested sites. Development of understorey vegetation in harvest-origin openings was similar across the levels of partial cutting and provided at least five plant species for cattle forage. Patches of grassland and shrubland in all treatment sites maintained viable populations of long-tailed voles and heather voles. These three small mammal indicators represent both late and early successional conditions in these IDF forests, which need to be managed for multiple objectives. Long-term monitoring of indicators will verify relationships with the components of biodiversity that they represent.

Description: Drought is a significant threat to forest health and the establishment of productive tree plantations. There is therefore great interest in understanding the mechanisms underpinning drought responses in forest trees. This review considers the means by which plants in general, and forest trees specifically, both detect and respond to water limitation. The review focuses on molecular-level responses to a drought stimulus, with an emphasis on responses that involve genome-wide reconfigurations in transcript abundance and protein complement in forest trees. A historical view of the molecular analysis of such responses shows a remarkable transition from understanding the impact of drought on individual genes to a more comprehensive picture of the suites of genes and proteins that constitute a drought response. Attention is paid to how this understanding might further the aims of preserving forest health and improve plantation productivity. The review suggests that genome-wide analysis of forest tree drought responses can be leveraged to provide new tools for conservation of adaptive variation and targets for selective breeding or directed modification of forest tree genotypes that can better contend with future drought scenarios.

Description: China’s collective forest tenure reform will have a profound impact on the livelihoods of rural people. For the equitable implementation of reform, rural smallholders need sufficient knowledge and understanding of the opportunities and limitations offered by reform. Here, we examine rural smallholder's awareness and attitude towards the reform, across the socio-economic range, in three villages of Zhang Guying Township, Hunan province. Income level and educational background played a consistent role in knowledge and understanding of the reform, as people with low income and no formal education were more likely to be unaware and have no clear understanding of the reform. Additionally, low-income rural smallholders were more likely to convert forest to cash crops, undercutting the central government's stated objectives for the forest reform to improve forest condition. Given our results, the government needs to ensure equitable distribution of information, specifically targeting low-income villagers without formal education. The strong disparity in knowledge and understanding between wealthy and poor creates a situation where the wealthy effectively benefit from the reform, while the poor miss its opportunity. This inequality has great potential for generating future unrest and conflict and for damaging forest condition due to unsustainable or uninformed practices.

Description: In UK forestry, the synthetic pyrethroid insecticides alpha-cypermethrin and cypermethrin have been used for many years to provide protection for young trees planted on restock sites from damage by the large pine weevil, Hylobius abietis L. However, concerns over the toxicity of these insecticides to aquatic life if misused have led to a search for alternative forms of protection. This paper describes a detailed programme of efficacy experiments undertaken between 2009 and 2015 to find replacements for these products. Over 50 combinations of chemical and non-chemical approaches were tested on 16 different sites. Of the alternative synthetic insecticides tested, applications of 0.037 g a.i. stem−1 acetamiprid provided high levels of protection from Hylobius browsing damage on young Sitka spruce (Picea sitchensis (Bong.) Carrière) trees, without causing any phytotoxic symptoms, and gave comparable levels of protection to those achievable using alpha-cypermethrin or cypermethrin. Acetamiprid is less toxic to aquatic life than alpha-cypermethrin or cypermethrin and has not been linked to bee decline. Applications of 0.0129 g a.i. stem−1 chlorantraniliprole also showed promise, and this relatively low toxicity non-neonicotinoid insecticide merits further study. Although imidacloprid and thiacloprid also provided good levels of protection, their use in forests is not now permitted due to concerns over their potential impacts on bees and drinking water, respectively. Whilst the natural product insecticide spinosad, and the entomopathogenic fungal control agent Metarhizium anisopliae (Metschn.) Sorokin, gave only limited protection in our work, they may have some future potential if methods of deployment can be improved. Other chemical and non-chemical approaches tested, but found to be largely ineffective in UK conditions, included the natural product insecticides azadirachtin, maltodextrin and pyrethrins, the synthetic insecticides lambda-cyhalothrin and spirotetramat and a wide range of repellents, flexible stem coatings and physical barrier products. However, we conclude that physical barrier sleeves such as MultiPro® and BioSleeve® may have a limited role as a partial substitute for the use of insecticides in the UK in some circumstances, but only if on-site populations of Hylobius are predicted to be low.

Description: To increase forest resilience to global change, forest managers are often directing forest stands towards a broader diversity of tree species. The small-leaved lime (Tilia cordata Mill.), a rare and scattered species in northwestern Europe, is a promising candidate for this purpose. Its life traits suggest a high resilience to climate change and a favourable impact on forest ecosystem services. This study used a dendroecological approach to assess how lime tree radial growth had responded to the past climatic change. First, 120 lime trees from nine sites were selected in southern Belgium based on criteria adapted to the rareness of the species. Chronology quality was assessed and resulting tree-ring series were validated at site and region levels. Second, a range of dendrochronological methods was used to analyze the changes over time in the variability and long-term trends of lime tree growth and their relation to climate during the period 1955–2016. Last, behaviour of lime trees was compared with that of beech from the same region and time period. For this purpose, the same methodology was applied to an additional beech tree-ring dataset (149 trees from 13 sites). Beech is the climax tree species of the region, but is known to be drought-sensitive and has shown weaknesses in the current climate. The quality of our tree-ring series attests that dendroecological investigation using rare and scattered species is possible, opening the way to further analysis on other such lesser-known forest tree species. The analysis showed that the small-leaved lime had been resilient to the past climatic change in multiple ways. Lime growth increased during the preceding decades despite an increased frequency and intensity of stressful climatic events. Lime growth quickly recovered in the years following the stresses. The growth–climate relationships were either stable over time or had a positive evolution. The behaviour of lime contrasted strongly with that of beech. Lime performed better than beech in every analysis. Small-leaved lime is thus a serious candidate for addressing climate change challenges in the region. It should be considered by forest managers planning to improve the sustainability and resilience of their forests, in particular in vulnerable beech stands.

Description: The restoration of forest structure and function is increasingly being used in boreal forests in order to halt the loss of biodiversity. Often ecological restoration is aimed at increasing the volume of dead and dying trees to enhance the biodiversity of deadwood-dependent organisms, but it may also increase population sizes of pest bark beetle species, even several years following restoration. Herein, we used a large-scale restoration experiment in Northern Sweden to assess the 5 years post-restoration effects of restorative gap cutting and prescribed burning on the populations of a set of economically harmful pest bark beetles (Ips typographus, Polygraphus poligraphus, Tomicus piniperda and Pityogenes chalcographus) and the most important predators of bark beetles, Thanasimus spp. In addition, we assessed the effects of forest stand characteristics at stand and landscape scale on the abundance of I. typographus. Five years post-restoration, gap-cut stands supported the highest abundances of P. poligraphus and contained the highest count of spruce trees newly attacked by bark beetles. By contrast, prescribed burning generally sustained the lowest abundances of pest bark beetles, especially I. typographus and P. poligraphus, and the highest abundance of their natural predators Thanasimus spp. The population abundance of I. typographus was also positively affected by the area of clear cuts within a 500 m radius from the stand. In conclusion, prescribed burning appears to be a safer method for ecological restoration than gap cutting in the long-term. According to our results, a risk of a local bark beetle outbreak still remains 5 years following the initiation of ecological restoration treatments on spruce-dominated mature gap-cut stands.

Description: ‘Analog’ forestry is a novel silvicultural approach for reforestation of degraded land that seeks to establish trees that are analogous in structure and ecological function to the original climax or subclimax vegetation of the region where they are planted. Analog forestry aims to strengthen rural communities, both socially and economically, with tree plantings of high biodiversity, which provide commercial products and resiliency, while avoiding agrochemicals and fossil fuels. The latter links this strategy to climate change mitigation and adaptation strategies, but there has been little analysis comparing the potential for above- and below-ground carbon storage in analog forests, as compared with more typical reforestation efforts via single-species plantations. We present the results of a study to estimate carbon sequestration levels, above- and below-ground, from an experimental analog forest system and a teak (Tectona grandis L.f.) plantation system, in comparison with a degraded pasture system. The study found that the analog and teak plantation forest systems stored higher quantities of total carbon (178 and 141 t C ha−1, respectively), when compared with a degraded pasture system (124 t C ha−1). However, the teak plantation had decreased soil carbon stocks, relative to the degraded pasture. The analog forest had the best balance of both above- and below-ground carbon stored over the 17-year study period and provided a more diverse array of timber and non-timber forest products when compared with the teak plantation. This suggests that analog forestry could be a viable social–ecological approach to carbon storage and reforestation in the study region and other places with large areas of degraded pasture and a good understanding of the structure and function of the original vegetation.

Description: Loblolly pine is a major fibre source for the pulp and paper industry. Here we developed the first nonlinear models to predict the within-tree and regional variation of tracheid length and width for planted loblolly pine. Data were obtained from macerated tracheids and near-infrared spectroscopy calibration models from trees sampled in 109 stands across the southeastern United States. The fixed effects for the final tracheid length model, which included cambial age, height of disk within tree, and physiographic region, explained 71 percent of the variation with root mean square error (RMSE) of 0.28 mm, while the fixed effects for the final tracheid width model explained 57 percent of the variation with RMSE of 1.4 μm. There was significant variation in tracheid properties across the growing regions. Tree maps showing within-tree variability in tracheid properties were produced. Five simulated scenarios were compared using the models developed, with mean tracheid dimensions calculated on a whole-tree basis at a first and second thinnings, and at final harvest. Also from the final harvest, the tops of trees, and outerwood chips produced during lumber manufacturing were also simulated. For the whole tree scenarios, both mean tracheid length and width increased with age, increasing from 2.24 mm and 40.5 μm (age 12), to 2.51 mm and 41.3 μm (age 18), and to 2.73 and 41.8 μm at age 25, respectively. The tops of the trees at age 25 had a mean tracheid length of 2.46 mm and a mean width of 41.0 μm, while the chips had a mean tracheid length of 3.13 mm and a mean width of 42.5 μm. Due to the models representing samples collected from across the southeastern United States, and their relatively high precision, they are suitable for incorporation into growth and yield systems allowing for prediction of tracheid properties.

Description: Light detection and ranging (LiDAR) is used to estimate tree, stand and forest characteristics across large geographic areas. In most analyses, several independent LiDAR-based allometric equations are built to predict various forest attributes. When each forest attribute is estimated independently, there is potential for predictions of forest attributes that are not mathematically or biologically consistent. Combined allometric equations can be considered a system of equations describing the stand structure. Mathematically compatible and biologically meaningful estimates can be derived by estimating key structural variables and solving for other components, rather than estimating each forest attribute separately and independently. In this study, we propose the development of a system of allometric equations describing the relationship between volume per unit area, Lorey’s average height, basal area, quadratic mean diameter (QMD) and density. The system of allometric equations is derived from extensive field data. Key structural attributes are predicted using LiDAR metrics, and the remaining structural variables are solved for using the system of allometric equations. Predictions of structural attributes from the system of allometric equations are compared with predictions from independent LiDAR-derived prediction equations. Results showed that applying the systems approach can provide reasonable and compatible estimates with lower required sample sizes, especially when multiple attributes need to be considered simultaneously. Testing the portability of the systems approach in more complex stand structures and across different LiDAR acquisitions will be required in the future.

Description: Forests of the world constitute one-third of the total land area and are critical for e.g. carbon balance, biodiversity, water supply and as source for bio-based products. Although the terrain within forest land has a great impact on accessibility, there is a lack of knowledge about the distribution of its variation in slope. The aim was to address that knowledge gap and create a globally consistent dataset of the distribution and area of forest land within different slope classes. A Geographic Information System (GIS) analysis was performed using the open-source QGIS, GDAL and R software. The core of the analysis was a digital elevation model and a forest cover mask, both with a final resolution of 90 m. The total forest area according to the forest mask was 4.15 billion hectares whereof 82 per cent was on slope  30°. Out of the major forestry countries, China had the largest proportion of forest steeper than 15° followed by Chile and India. A sensitivity analysis with 20 m resolution resulted in increased steep areas by 1 per cent point in flat Sweden and by 11 per cent points in steep Austria. In addition to country-specific and aggregated results of slope distribution and forest area, a global raster dataset is also made freely available to cover user-specific areas that are not necessarily demarcated by country borders. Apart from predicting the regional possibilities for different harvesting equipment, which was the original idea behind this study, the results can be used to relate geographical forest variables to slope. The results could also be used in strategic forest fire fighting and large-scale planning of forest conservation and management.

Description: Forest harvesting operations with heavy machinery can lead to significant soil rutting. Risks of rutting depend on the soil bearing capacity which has considerable spatial and temporal variability. Trafficability prediction is required in the selection of suitable operation sites for a given time window and conditions, and for on-site route optimization during the operation. Integrative tools are necessary to plan and carry out forest operations with minimal negative ecological and economic impacts. This study demonstrates a trafficability prediction framework that utilizes a spatial hydrological model and a wide range of spatial data. Trafficability was approached by producing a rut depth prediction map at a 16 × 16 m grid resolution, based on the outputs of a general linear mixed model developed using field data from Southern Finland, modelled daily soil moisture, spatial forest inventory and topography data, along with field measured rolling resistance and information on the mass transported through the grid cells. Dynamic rut depth prediction maps were produced by accounting for changing weather conditions through hydrological modelling. We also demonstrated a generalization of the rolling resistance coefficient, measured with harvester CAN-bus channel data. Future steps towards a nationwide prediction framework based on continuous data flow, process-based modelling and machine learning are discussed.

Description: In forest inventory, traditional ground-based resource assessments are often expensive and time-consuming forcing managers to reduce sample sizes to meet budgetary and logistical constraints. Small area estimation (SAE) is a class of statistical estimators that uses a combination of traditional survey data and linearly related auxiliary information to improve estimate precision. These techniques have been shown to improve the precision of stand-level inventory estimates in loblolly pine plantations using lidar height percentiles and thinning status as covariates. In this study, the effects of reduced lidar point-cloud densities and lower digital elevation model (DEM) spatial resolutions were investigated for total planted volume estimates using area-level SAE models. In the managed Piedmont pine plantation conditions evaluated, lower lidar point-cloud densities and DEM spatial resolutions were found to have minimal effects on estimates and precision. The results of this study are promising to those interested in incorporating SAE methods into forest inventory programs.

Description: We explore the implications of managing forests for the dual purpose of sequestering carbon and producing timber, using a model of the forest sector that includes a Hartman-based representation of forest owners’ behaviour as well as heterogeneity in environmental conditions. We focus on France, where recent policies aim at increasing the carbon sink and where the diversity of forests makes an analysis of spatial dynamics relevant, and we use recent estimates of the shadow price of carbon consistent with the country’s climate commitments. Results suggest that forests may sequester up to 550 MtCO2eq by 2100, driven by changes in harvest levels and species choice, whilst rotation lengths increase overall. A spatial analysis reveals a high spatial variability for these trends, highlighting the importance of considering the local context. Changes in investment patterns affect the spatial distribution of forest cover types: by the end of the century, a majority of regions comprise a larger share of older, multiple-species and mixed-structure forests. Whilst such an evolution may present benefits in terms of biodiversity, ecosystem services provision and resilience, it raises questions regarding the adequacy of such developments with current forest policy, which also aims at increasing harvest levels. An overall mitigation strategy for the forest sector would likely include incentives to energy and material substitution in downstream industries, which we did not consider and may interact with sequestration incentives.

Description: Invertebrate forest pests and pathogens can cause considerable economic losses and modern patterns of trade have facilitated the international movement of pest species on an unprecedented level. This upsurge in trade has increased the pathways available to high risk species, facilitating entry and potential establishment in nations where they were previously absent. To support policy and pest prioritization, pest risk analyses are conducted to decide ‘if’ and ‘how’ pests should be regulated in order to prevent entry or establishment; however, they cannot be carried out for every potential pest. This paper utilizes a hierarchical clustering (HC) approach to analyse distribution data for pests of Sitka spruce (Picea sitchensis (Bong.) Carr.) in order to identify species of high risk to Ireland, as well as potential source regions of these pests. The presence and absence of almost a 1000 pests across 386 regions globally are clustered based on their similarity of pest assemblages, to provide an objective examination of the highest risk pests to Irish forestry. Regional clusters were produced for each taxon analysed including the Coleoptera, Diptera, Hemiptera, Hymenoptera, Nematoda, Lepidoptera and the Fungi. The results produced by the HC analysis were interpreted with regard to biological realism and climate. Biologically meaningful clusters were produced for each of the groups, except for the Diptera and Nematoda, and each of the species analysed were ranked within their group by a quantitative risk index specific to the island of Ireland. The impact of uncertainty in the distribution data is also examined, in order to assess its influence over the final groupings produced. The outputs from this analysis suggest that the highest risk pests for Ireland’s Sitka spruce plantations will originate from within Europe. Ultimately, Ireland could benefit from seeking regulation for some of the higher ranking pests identified in this analysis. This analysis provides the first of its type for Sitka spruce, as well as its application in Ireland. It also serves to highlight the potential utility of HC as a ‘first approach’ to assessing the risk posed by alien species to hitherto novel regions.

Description: Regular biomass estimations for natural and plantation forests are important to support sustainable forestry and to calculate carbon-related statistics. The application of remote sensing data to estimate biomass of forests has been amply demonstrated but there is still space for increasing the efficiency of current approaches. Here, we investigated the influence of field plot and sample sizes on the accuracy of random forest models trained with information derived from Pléiades very high resolution (VHR) stereo images applied to plantation forests in an arid environment. We collected field data at 311 locations with three different plot area sizes (100, 300 and 500 m2). In two experiments, we demonstrate how plot and sample sizes influence the accuracy of biomass estimation models. In the first experiment, we compared model accuracies obtained with varying plot sizes but constant number of samples. In the second experiment, we fixed the total area to be sampled to account for the additional effort to collect large field plots. Our results for the first experiment show that model performance metrics Spearman’s r, RMSErel and RMSEnor improve from 0.61, 0.70 and 0.36 at a sample size of 24–0.79, 0.51 and 0.15 at a sample size of 192, respectively. In the second experiment, highest accuracies were obtained with a plot size of 100 m2 (most samples) with Spearman’s r = 0.77, RMSErel = 0.59 and RMSEnor = 0.15. Results from an analysis of variance type-II suggest that the overall most important factors to explain model performance metrics for our biomass models is sample size. Our results suggest no clear advantage for any plot size to reach accurate biomass estimates using VHR stereo imagery in plantations. This is an important finding, which partly contradicts the suggestions of earlier studies but requires validation for other forest types and remote sensing data types (e.g. LiDAR).

Description: Prosopis chilensis (Molina) Stuntz (Leguminosae) is a valuable native species in Argentina included in the Prosopis Management Programme. Natural provenances show important height and shape differentiation throughout their distribution in the Monte Desert. The availability of progeny trials provides an opportunity to quantify genetic differentiation among provenances and test the relative importance of demographic vs adaptive processes on morphological variation. We quantified both genetic and quantitative differentiation of neutral markers and five economically important traits, respectively, among four provenances in a provenance-progeny trial. We aimed to quantify the genetic basis of variations in height, basal diameter, tree shape, spine length and biomass. Two hypotheses were tested: (1) economically important traits have significant heritability, and (2) the phenotypic variation among provenances is the result of local adaptation to particular environmental conditions. Our results indicate that most morphological variation was found among individuals within families (~95 per cent). The h2 estimates were heterogeneous among traits and ranged from low (0 for number of stems) to moderate (0.22 and 0.28 for spine length and biomass, respectively). Variance among families (~5 per cent) was evenly distributed within and among provenances. Morphological differentiation among provenances was low, but significant, and could be attributed mainly to individuals from Villa Unión. Based on molecular markers, genetic differentiation among provenances was low and significant (FST = 0.03; P = 5 × 10−4) but was able to differentiate the groups from Villa Unión, Fiambalá and Mogna-Chilecito. Neutrality tests were conducted using the FST–QST test and DJSOST and δGREGORIUS alternative coefficients of differentiation. Neutrality tests yielded no evidence of local adaptation and were rather consistent in showing a trend toward stabilizing selection, particularly for spine length. The selection strategy for breeding programmes should depend on the trait to be improved and should consider both provenance and familiar information. Considering an intra-familiar ranking is encouraged in order to maximize the genetic gain. Additionally, in order to recover germplasm provenance diversity, based on morphological and microsatellite results, our recommendation would be to include seeds from individuals from at least the Villa Unión, Fiambalá and Mogna-Chilecito areas.

Description: To investigate enemy pressure across the range of the pine processionary moth (Thaumetopoea pityocampa, Den. & Schiff.) as it spreads northwards in Europe because of climate change, a survey of 206 egg batches from historical and newly colonized areas at both the westernmost and the easternmost ends of the front was carried out in 2016–2018. Out of them, 97 egg batches were collected from nine locations in three regions in France and 109 from four localities in two regions in Bulgaria, both within historical and newly colonized ranges of the pest. The average number of eggs per batch collected in Bulgaria (226.6 ± 43.2) was higher than that in France (194.3 ± 50.1). However, the hatching percentage was higher in French samples, varying from 69.8 to 95.7, vs 49.8 to 85.2 per cent in Bulgarian samples. Four primary parasitoids (Ooencyrtus pityocampae, Baryscapus servadeii, Anastatus bifasciatus, Trichogramma sp.) and a hyperparasitoid (Baryscapus transversalis, found only in two regions of the historical range in Bulgaria) were identified. The oligophagous species B. servadeii was present at all sites within the historical range of the pest. In newly colonized areas, the impact of primary parasitoids on the host was distinctly low, suggesting that they lag behind the range expansion of pine processionary moth. In France, the most abundant species in the T. pityocampa parasitoid complex were B. servadeii in Ré Island and Orléans (97.3 and 87.4 per cent, respectively), and Trichogramma sp. (99.7 per cent) in a newly colonized locality in Fréhel. Ooencyrtus pityocampae prevailed in three of four Bulgarian localities (72.1 per cent in Sandanski, 89.7 per cent in Maglizh and 65.7 per cent in Sladak kladenets), whereas B. servadeii was the most abundant in Gega (75.4 per cent). Mortality of B. servadeii and O. pityocampae caused by the hyperparasitoid B. transversalis amounted to 4.8–6.2 per cent. The impact of predators on the pine processionary moth in the egg stage was negligible at most sites, reaching 12.5 per cent in only one site (Maglizh).

Description: Widely distributed in Quebec, balsam fir (Abies balsamea (L.) Mill.) is highly vulnerable to wind damage. Recently, there has been a trend in forest management to increase the use of partial cuttings in naturally regenerating stands, leaving the remnant trees at increased risk of wind damage. In order to limit wind damage after partial cuttings, it is therefore important to find silvicultural practices that minimize the risk of wind damage in these fir stands. Our main objective was to find balsam fir-specific values of parameters to integrate into the wind risk model ForestGALES, in order to simulate the impact of different types of commercial thinning on wind damage risk, and to determine which practice potentially minimizes the risk in a naturally regenerated stand. An anemometer placed at canopy height and strain gauges attached to the trunks of balsam firs allowed us to measure the wind-induced bending moments experienced by a sample of balsam fir trees. This enabled the calculation of the turning moment coefficients specific to each of the trees in order to compare them with the ForestGALES model predictions and to adapt the model for balsam fir stands. The model was tested first with only tree diameter and height as input variables to calculate the turning moment coefficient, then with the addition of a competition index, and finally with the addition of crown dimensions. Wind climate parameters for prediction of the probability of damage were calculated using the Wind Atlas Analysis and Application Program airflow model. The model with the highest accuracy was then used to simulate two types of thinning and determine the impact on wind damage risk for each tree in the stand. According to the model’s predictions, thinning from below has a reduced risk of wind damage compared with thinning from above.

Description: An understanding of the relationship between volume increment and stand density (basal area, stand density index, etc.) is of utmost importance for properly managing stand density to achieve specific management objectives. There are two main approaches to analyse growth–density relationships. The first relates volume increment to stand density through a basic relationship, which can vary with site productivity, age, and potentially incorporates treatment effects. The second is to relate the volume increment and density of thinned experimental plots relative to that of an unthinned experimental plot on the same site. Using a dataset of 229 thinned and unthinned experimental plots of Norway spruce, a growth model is developed describing the relationship between gross or net volume increment and basal area. The models indicate that gross volume increases with increasing basal area up to 50 m2 and thereafter becomes constant out to the maximum basal area. Alternatively, net volume increment was maximized at a basal area of 43 m2 and decreased with further increases in basal area. However, the models indicated a wide range where net volume increment was essentially constant, varying by less than 1 m3 ha−1 year−1. An analysis of different thinning scenarios indicated that the relative relationship between volume increment and stand density was dynamic and changed over the course of a rotation.

Description: Substantial growth losses in Douglas-fir can be the result of Swiss needle cast, a foliar disease caused by the fungus Nothophaeocryptopus gaeumannii. Although the disease is native to western North America, it is expected to become increasingly problematic in regions where climates become warmer in winter and wetter in spring, such as in coastal British Columbia (BC), Canada. Previous research suggests that tolerance to this disease is under partial genetic control. We therefore aim to screen for tolerance and resistance to the disease in the tree breeding population of coastal Douglas-fir (Pseudotsuga menziesii var. menziesii) in BC. We evaluated if early screening for resistance or tolerance to this disease is possible. We worked with 32 families grown for 18-years on two full-sibling genetic field trial sites representing different climates. We assessed 〉900 trees for disease signs and symptoms from 2017 to 2019. Needle retention was assessed in the field. In the laboratory, the proportion of stomata occluded with pseudothecia was measured, deoxyribonucleic acid (DNA) was extracted, and the proportion of fungal DNA in the needles was assessed using quantitative polymerase chain reaction. Strong differences were observed among families for needle retention, stomatal occlusion and fungal load. The milder and wetter site closer to the coast was generally more severely affected. Families showed rank changes between the two sites for all response variables. Higher needle retention was correlated with increased tree volume. No correlation was found between the proportion of stomata occluded with pseudothecia, fungal DNA load and needle retention. These results indicate that a more complex pathology is involved in causing needle loss. We conclude that screening for Swiss needle cast tolerance in the coastal BC Douglas-fir breeding population is possible if needle retention can be assessed and that area-specific deployment strategies may be needed given family rank changes in different environments.

Description: Higher temperatures and drought are key aspects of global change with the potential to alter the distribution and severity of many arthropod pests in forest systems. Scale insects (Hemiptera: Coccoidea) infest many tree species and are among the most important pests of trees in urban and rural forests, plantations and other forest systems. Infestations of native or exotic scale insects can kill or sicken trees with economic and ecosystem-wide consequences. Warming can have direct effects on the life history, fitness and population dynamics of many scale insect species by increasing development rate, survival or fecundity. These direct benefits can increase the geographic distribution of scale insects and their consequences for tree health. Warming and drought can affect scale insects indirectly by altering the quality of their host trees. Additive or interactive effects of warming and drought can change tree quality in such a way that it increases scale insect fitness and population growth. However, the effects are species- and context-dependent with some scale insect species negatively affected by drought-induced changes in tree quality. Warming and drought are often coincident in urban forests and predicted to co-occur in many parts of the world under climate change scenarios. The individual and interactive effects of these factors require further research to inform predictions and management of scale insect pests. Warming also indirectly affects scale insects by altering interactions with natural enemies. This includes changes in natural enemy phenology, community composition and abundance. In addition, warming can alter scale insect phenology or voltinism causing asynchrony with natural enemies or population growth too rapid for natural enemies to suppress. Direct and indirect effects of warming and drought on scale insects can increase the potential for some exotic species to become established and for some native species to become invasive. Unfortunately, much research on scale insects is confined to a few particularly important native or exotic pests which limits our ability to predict the effects of warming on many current or potential pests. More research is required to understand how warming and drought affect scale insects, scale insect management and the forest systems they inhabit.

Description: Smartphones with their capability to receive Global Navigation Satellite Systems (GNSS) signals can be currently considered the most common devices used for positioning tasks, including forestry applications. This study focuses on possible improvements related to two crucial changes implemented into Android smartphone positioning in the last 3 years – dual-frequency (L1/L5) GNSS receivers and the possibility of recording raw GNSS data. The study comprises three experiments: (1) real-time measurements of individual points, (2) real-time recording of trajectories, and (3) post-processing of raw GNSS data provided by the smartphone receiver. The real-time tests were conducted using final positions provided by the internal receiver, i.e. without further processing or averaging. The test on individual points has proven that the Xiaomi Mi8 smartphone with a multi-constellation, dual-frequency receiver was the only device whose accuracy was not significantly different from single-frequency mapping-grade receiver under any conditions. The horizontal accuracy of most devices was lower during leaf-on season (root mean square errors between 5.41 and 12.55 m) than during leaf-off season (4.10–11.44 m), and the accuracy was significantly better under open-area conditions (1.72–4.51 m) for all tested devices when compared with forest conditions. Results of the second experiment with track recording suggest that smartphone receivers are better suited for dynamic applications – the mean shift between reference and measured trajectories varied from 1.23 to 5.98 m under leaf-on conditions. Post-processing of the raw GNSS data in the third experiment brought very variable results. We achieved centimetre-level accuracy under open-area conditions; however, in forest, the accuracies varied from meters to tens of meters. Observed loss of the signal strength in the forest represented ~20 per cent of the open-area value. Overall, the multi-constellation, dual-frequency receiver provided more robust and accurate positional solutions compared with single-frequency smartphones. Applicability of the raw GNSS data must be further studied especially in forests, as the provided data are highly susceptible to multipath and other GNSS adverse effects.

Description: National forest inventories, in which trees are often mapped within the plots, provide a tool for the quantification of large-scale forest structure since they cover all forest areas. Many National Forest Inventories follow a nested design in order to reduce the sampling effort for smaller trees. We propose and test a methodology that allows the spatial pattern of trees, species mingling and size differentiation to be characterized using the nearest neighbour indices and second-order moment functions from nested plot data. The nearest neighbour indices and second-order moment functions for the actual distribution are compared with simulations of the appropriate null model: spatial randomness for spatial pattern characterization or spatial independence for species mingling and size differentiation. The proposed method consists of constraining the null model to fit the nested plot design. For the purposes of the study, we simulated 120 plots and used 26 real plots located in pure and mixed stands in Central Spain, for which a complete census with detailed information about trees was available. The nested design used in the Spanish National Forest Inventory (SNFI) plots was simulated to test the performance, taking the complete census as reference. Despite of the limited accuracy for some structural measures, the proposed method based on nested design data performed better for most of the nearest neighbour indices and second-order moment functions than the strategy currently used in the SNFI for structure assessment in a subsample of SNFI plots, consisting of mapping the 20 trees closest to the plot centre. Nearest neighbour indices provided greater accuracy for species mingling assessment than second-order moment functions, whereas the opposite occurred when describing spatial pattern and size differentiation. The methodology proposed provides the first insight into the characterization of forest structure in nested designs although more evaluations are required for different forest types.

Description: Oak-dominated forests, economically and ecologically valuable ecosystems, are widely distributed in China. These oak-dominated forests are now generally degraded coppice forests, and are of relatively low quality. Climate change has been shown to affect forest growth, tree mortality, and recruitment, but available forest growth models are lacking to study climate effects. In this study, a climate-sensitive, transition-matrix growth model (CM) was developed for uneven-aged, mixed-species oak forests using data collected from 253 sample plots from the 8th (2010) and 9th (2015) Chinese National Forest Inventory in Shanxi Province, China. To investigate robustness of the model, we also produced a variable transition model that did not consider climate change (NCM), and fixed parameter transition matrix model (FM), using the same data. Short-term and long-term predictive performance of CM, NCM, and FM were compared. Results indicated that for short-term prediction (5 years), there was almost no significant difference among the three predictive models, though CM exhibited slightly better performance. In contrast, for long-term prediction (100 years), CM, under the three representative concentration pathways (RCPs), i.e. RCP2.6, RCP4.5 and RCP8.5, indicated rather different dynamics that were more reliable because climate factors were considered which could significantly influence forest dynamics, especially in long-term prediction intervals. The CM model provides a framework for the management of mixed-species oak forests in the context of climate change.

Description: Tree crown volume is a fundamental tree characteristic. It correlates to forest biomass production and most relevant ecosystem and environmental functions, such as carbon sequestration and air pollution reduction. When researching these relationships, it is necessary to clearly define and then quantify tree crown variables in a both accurate and operational manner. In this paper, we review the reported literature on the assessment of tree crown volume. First, we compile the varying definitions of crown volume and other tree crown variables that may be used as inputs to quantify crown volume. Then, we examine the data sources for quantifying these variables, including field measurements, terrestrial photographs, aerial photographs and laser scanning. Furthermore, we compare the published approaches on translating these crown variable measurements into tree crown volume. These approaches include the approximation of simple geometric solids, approaches of computational geometry and voxelization. We also compare the reported accuracies and major challenges of these approaches. From this literature review, the reader may craft a suitable approach for the assessment of crown volume.

Description: The significance of post-disaster temporary housing for the victims has led to the problem of designing a good model of temporary housing. According to research hypothesis, using the design of Iranian nomads’ housing instead of common forms of temporary housing contributes to energy saving. Investigating the architecture of nomads’ housing indicates that there is a type of indigenous knowledge for designing and constructing this type of housing. After the study, data collection and a review of the types of Iranian nomads’ housing using library and causal method, thermal simulation was conducted to investigate the effect of changing the temporary housing form inspired by the nomads’ housing on energy consumption. Findings showed that using shapes like Kapars of Baluchistan nomads, wigwams of Shahsavan tribe in Ardabil and mudhifs of Khuzestan will save energy for 36%, 24% and 25%, respectively.

Description: The quality and shelf-life of NCS (non-centrifugal sugar) mainly depend on the moisture content present in it. NCS formed by the current practice of open sun drying contains moisture substantially greater than the acceptable level of 3%. This paper presents the work undertaken to design a tunnel dryer to achieve the required moisture content of granular NCS for various load conditions. An experimental investigation was conducted on a laboratory-scale dryer to achieve the required moisture content for various loads. This experimental data was compared with the output of two drying models and a validated one that could be used to design an industrial-scale dryer. For various load conditions on each tray and dryer exit temperature, nine different cases were determined. The number of trucks, drying time, and energy requirements were computed using the validated theoretical model. A tunnel dryer with a length, height and width of 18, 1.2 and 1 m respectively and 18 trucks with 24 trays on each truck is shown to be dry 1 tone of NCS based on the minimum energy requirement of 176.49 MJ, and a drying time of 68 min.

Description: 4-Amino-3-(2-bromo-5-methoxyphenyl)-1H-1,2,4-triazole-5(4H)-thione (ATH) was synthesized and characterized by nuclear magnetic resonance and Fourier-transform infrared as spectroscopical techniques and elemental analysis. ATH was studied for corrosion inhibition of mild steel in corrosive environment by means of weight loss technique, scanning electron microscopy and the adsorption isotherm. ATH demonstrates a superior inhibition efficiency against corrosion of mild steel. Adsorption data fit well to a Langmuir isotherm model.

Description: Hydrogen-fueled combustion systems are becoming popular in recent years. Methane is one of the significant hydrogen supplier in nature. Thus, in the study, the natural gas-fueled reactor-assisted solid oxide fuel-cell system is configured to provide a current to load the battery to turn the propeller of an unmanned aerial vehicle in the large-scale hydrogen-onboard system. The methane-fueled reactor has not been studied under a large-scale case in literature yet. To investigate the amount of products, this paper presents about the steam-reforming performance of natural gas in steady state and transient in the reactor. The influence of vital parameters such as steam/carbon, gas feed temperatures, the amount of heat transferred to the reactor in methane steam reforming for a plug flow reactor, and a continuous stirred tank-type reactor is investigated respectively. Methane conversion, yield of hydrogen gas and H2 gas generation for different medium conditions along the reactor are studied on by using the COMSOL Multiphysics program. The steady-state and time-dependent characteristics of the steam reforming of natural gas are focused on. The high conversion ratio of methane gas is obtained by ranking the steam/carbon ratio. The released hydrogen gas molar flow rate is increasing according to the reactor volume. The achieved power provided by produced gas of H2 is 97 hp supplying the thrust force for an unmanned aerial vehicle.

Description: The corrosion inhibition of Schiff base, namely 2-((2-hydroxy-5-methoxybenzylidene)amino)pyridine (HMAP), for mild steel (MS) in a 1 M hydrochloric acid environment was investigated by means of weight loss and scanning electron microscopy techniques. Quantum chemical calculation based on density functional theory (DFT) was carried out on HMAP. Results illustrated that HMAP is a superior inhibitor for the corrosion of MS in 1.0M hydrochloric acid environment, and inhibition efficiency is higher than 90.0% at 0.5 g/L HMAP. Inhibition performance increases with regard to concentration increase and inhibition performance decreases when raising temperature. Adsorption of the inhibitor on the MS surface followed Langmuir adsorption isotherm and the value of the free energy of adsorption; ΔGads indicated that the adsorption of HMAP was a physisorption/chemisorption process. The DFT refers to perfect correlation with methodological inhibition performance.

Description: Ecological footprint (EF) is an indicator that accounts for human demand in the environment compared with the sizes of the bio-productive land and sea areas. This research was carried out to determine the EF for environmental sustainability in Ilorin Metropolis. Empirical surveying, which involved systematic random sample technique, was used to select residential households in each community for this investigation. The EF indicators, which include food, energy and waste consumptions, were determined empirically. The bio-capacity (BC), ecological stress and deficit were determined, from the land used as environmental sustainable areas in Ilorin, using Google Earth Mapping. The results revealed that energy has the highest EF of 44%, followed by waste and food with the footprint of 25% and 5%, respectively. A deficit of 38% was obtained, and this requires eight times the BC to balance the EF of the population. This implies that people are consuming more of the energy and generating more wastes than they consumed food.

Description: The case study presented in this paper is an innovative ground source heat pump (GSHP) system constituted by a hybrid Photovoltaic Thermal (PVT) solar system for poultry houses. Farmers tend to not to apply GSHPs because of the high prices of excavation and time consumption. The innovative heat pump system assessed in this study comprises of a new type of heat exchangers; a thin-tube solar polyethylene heat exchanger installed between roof tiles and PV panels and a novel vertical ground heat exchanger to utilize the heat stored in the soil. The heating system applied to a poultry house are monitored and evaluated under a variety of environmental and operating conditions to achieve annual/long-term efficiency of the heating system in Kirton, UK. The maximum heating demand of the poultry house is determined 34.4 MWh/PC while the minimum is 11,1 MWh/PC. The monitored results show that the heat pump produced 15.02 MWh of thermal energy per annum. Solar PV and heat pump worked very well together with solar PV covering all the heat pump’s annual electrical energy requirement and generated 8.74 MWh of extra electricity exported to the grid. The seasonal coefficient of performance is found 3.73 through a year. The novel PVT-GSHP heating system is a very promising solution for high fossil fuel consumption in the agriculture industry and the energy savings of the whole system can be noticeably increased dependent up on the system controlling.

Description: This paper introduces an innovative thin film PV vacuum glazing (PV-VG) technology. In addition to electricity generation, the PV-VG glazing can also reduce heat loss from the building in winter and reduce heat gain in summer. In building integrated photovoltaics application, optical characterization of the PV glazing is important in determining the solar ray transmission and thermal transfer process of the glazing. This paper discusses the optical properties of the PV-VG glazing by considering the different layers of the glazing unit that includes a self-cleaning glass, a thin film PV glass and a low-e vacuum glazing. Based on the optical transfer matrix, the transmission coefficients of different film layers were deduced. The theoretical calculations were then validated against the transmission coefficient experiment of the PV-VG using an EDTM SS2450 Solar Spectrum Meter. The calculation error of the transmission coefficient of the single-layer glazing is generally within 5%, the calculation error of the transmission coefficient of the integrated PV-VG glazing is about 6%. The results show that the average visible light transmission coefficient, the average infrared light transmission coefficient and the overall transmission coefficient of PV-VG glazing are 19%, 16% and 12%, respectively. The study is important to optimize the visible light transmission of the PV-VG glazing; the optical model obtained above lays a solid foundation for further study of transmission coefficient analysis of different functional coating of PV-VG glazing.

Description: Renewable energy technologies have been developed in recent years due to the limited sources of fossil fuels, the possibility of depletion of fossil fuels and the related environmental issues. In these types of systems, it is crucial to reach optimum sizing in order to have an affordable system based on solar and wind energy and energy storage. In this study, a powerful optimization scheme based on tabu search, called discrete tabu search, has been proposed for sizing three stand-alone solar/wind/energy storage (battery) hybrid systems. For validating the applied algorithm effectiveness, the results are compared with the results found by the discrete harmony search. The obtained outcomes are compared on the basis of total annual cost. The components of the scheme are analyzed in different operating conditions by applying meteorological data in addition to real time information from three typical regions of Iran. According to the obtained data, applying ‘discrete tabu search’ leads to better outputs on the basis of mean, standard deviation and worst indexes.

Description: Based on 804 samples of farmers in Hubei Province, a typical major grain-producing area in China, this study empirically analyzed the effects of two different policy tools, i.e. economic incentives (subsidies) and order enforcements (regulatory restrictions), as well as the effects of their interaction, on farmers’ chemical fertilizer reduction and substitution behaviors. Samples were grouped according to the degree of concurrent employment to analyze the effects on different groups. The results show that (1) the influences of these policies on the behaviors were significantly positive; (2) after constructing the interactive variables of the policies, the influence of the order enforcement policy was no longer significant, but the influence of the interaction was significantly positive; (3) the low-degree concurrent employment farmers were more likely to be affected by the order enforcement policy, whereas the high-degree ones were more affected by the economic incentive policy; and (4) the behaviors of the low-degree ones were strongly affected by family management characteristics, whereas the high-degree ones were more affected by the farmers’ individual characteristics.

Description: The present study aims to investigate the thermodynamic and financial aspect of concentrated solar power (CSP) plant hybridized with biomass-based organic Rankine cycle (ORC), thermal energy storage (TES), hot springs and CO2 capture systems. The organic working fluids namely R123, R235fa, D4 and MDM are selected for designing the hybrid system at different operating conditions. The nominal power capacities of the CSP and biomass ORC plants are 1.3 MW and 730 kW respectively. Additionally, a parametric study has been carried out to understand the influencing parameters that affect the system’s performance. From the results, it is revealed that the biomass ORC plant with a hot spring system alone can develop a power of 720 and 640 kW for D4 and MDM respectively. Furthermore, the power generation can be increased with addition of TES in the CSP plant. From the economic point of view, the hybrid system with special focus on CO2 capture could be very profitable if the levelized cost of electricity (LCOE) is fixed at 0.24$/kWh. In this scenario, the payback period is 8 years with an internal rate of return (IRR) more than 8%. Therefore, the hybrid system is thermodynamically and financially attractive for dispatchable electricity.

Description: Geothermal energy is a kind of green and non-polluting renewable energy. Medium and low-temperature geothermal energy below 150 °C is usually used directly for heating, industrial and agricultural heating, bathing, etc., and the utilization rate is low. Organic Rankine cycle (ORC) system can be used in a low-temperature geothermal power generation systems. Thermodynamic analysis of the thermal cycle system is carried out in this paper. Based on the principle of exergy analysis, the cycle parameters such as evaporation temperature, condensation temperature, superheating temperature, and supercooling temperature are analyzed. The results show that the exergy efficiency and system output power can improve by increasing evaporation temperature and the exergy loss can decrease in the evaporator. Increasing superheating temperature enhances the output power of the expander and the exergy loss in the condenser, decreases the exergy efficiency simultaneously. Increasing condensation temperature decreases the exergy efficiency of the system and the output power of the expander, and increases the exergy loss of the system. Although the output power of the expander will not be affected by supercooling temperature, the rise of supercooling temperature will reduce the exergy efficiency of the system and increase the exergy loss of the evaporator.

Description: The present work aimed to select the optimum solar tracking mode for parabolic trough concentrating collectors using numerical simulation. The current work involved: (1) the calculation of daily solar radiation on the Earth’s surface, (2) the comparison of annual direct solar radiation received under different tracking modes and (3) the determination of optimum tilt angle for the north-south tilt tracking mode. It was found that the order of solar radiation received in Shanghai under the available tracking modes was: dual-axis tracking 〉 north-south Earth’s axis tracking 〉 north-south tilt tracking (β = 15°) 〉 north-south tilt tracking (β = 45) 〉 north-south horizontal tracking 〉 east-west horizontal tracking. Single-axis solar tracking modes feature simple structures and low cost. This study also found that the solar radiation received under the north-south tilt tracking mode was higher than that of the north-south Earth’s axis tracking mode in 7 out of 12 months. Therefore, the north-south tilt tracking mode was studied separately to determine the corresponding optimum tilt angles in Haikou, Lhasa, Shanghai, Beijing and Hohhot, respectively, which were shown as follows: 18.81°, 27.29°, 28.67°, 36.21° and 37.97°.

Description: Renewable energies could be a good solution to the problems associated with fossil fuels. The storage of wind energy by means of small-scale devices rather than large-scale turbines is a topic that has gained lots of interest. In this study, a compact device is proposed to harvest wind energy and transform it into electrical energy, by means of oscillations of a magnet into a coil, using the concept of vortex-induced vibration (VIV) behind a barrier. For a more comprehensive investigation, this system is studied from two viewpoints of fluid mechanics (without magnet) and power generation (with the magnet). For this purpose, an oscillating plate hinging on one side and three barriers with different geometrical shapes including cylindrical, triangular and rectangular barriers are used. In addition to the effect of barrier geometry, the impacts of various barriers dimensions, the distance between the plate and the barriers as well as inclination angle of the plate with respect to the horizon on the amplitude of oscillations and generated power are investigated. Results showed that in each case, there is a unique Reynolds number in which the frequency of vortex shedding equals to the frequency of plate oscillation and the output power from the energy harvester device is maximum. Besides, by increasing the barrier dimensions, the amplitude of oscillations increases up to three times, which leads to a higher generated power. Finally, by considering the studied parameters, the best conditions for generating energy using the VIV method are presented for design purposes. Among all the considered cases, the cylindrical barrier with the highest diameter and nearest distance to the plate led to the highest efficiency (0.21%) in comparison with other barriers.