ALBERT

Description: Investigations are carried out to study the heat and mass transfer characteristics of a falling film horizontal absorber by employing a two-dimensional numerical technique. The potential refrigerant, R134a (1,1,1,2-tetrafluroethane), is absorbed by the falling film of the R134a–DMAC (dimethylacetamide) solution. The variations of performance parameters along the tube surface are presented for different solution inlet temperatures and absorber pressures. The mass flux at the interface is observed to be higher at higher solution temperature and absorber pressure. The variation of the interface to bulk fluid and bulk fluid to wall heat transfer coefficient, overall heat transfer coefficient and mass transfer coefficient are studied for different solution temperatures and absorber pressures.

Description: Solar–thermal power plants are being deployed world-wide. These plants have traditionally used steel absorber pipes. Two types of fluids have been used in such ventures, synthetic aromatic fluid or water. Fluid flow in parabolic trough systems leads to instability in the tube due to the concentrated solar flux on only one-half of the absorber tube, resulting in temperature asymmetricity. The resulting stresses cause deflection and bending of the tube. This paper deals with direct steam systems and proposes incorporation of internal helical fins within the tube to reduce temperature variation. The fins provide an orderly distribution of flow from the ‘hot’ to the ‘cold’ side of the tube. A CFD simulation was carried out for three fin pitches, and an aluminium pipe without fins. The effect on heat transfer improvement and temperature asymmetry is presently reported. It is shown that the thermal gradient between the upper and lower temperature for the pipe without a helical fin (20 K) is considerably higher compared with the pipes with 100, 200 and 400 mm pitch helical fins, i.e. 10.8, 13, 14.9 K, respectively. Also, the thermal gradient for the aluminium pipe was also much lower when compared with the steel pipe.

Description: Aerogels are a special type of solid material with nanometre-scale pores 〈1/3000th the width of a human hair. Porosity is in excess of 90%, in some cases as high as 99.9%, and densities can be as low as 3 kg/m 3 . Aerogels are essentially ‘puffed-up sand’ and are often termed ‘frozen smoke’. Their thermal conductivity (0.014 W/m K at room temperature) is the lowest of any solids, and they also have good transparency. The acoustic properties of aerogels make them effective insulators against noise, and aerogels have the lowest refractive index, and dielectric constant of all solid materials. The unusual properties of aerogels open the way to a new range of opportunities for their application in buildings. This paper provides information on their unique features and reviews the potential applications for aerogels in buildings as well as latest developments in the field.

Description: The UK is implementing different types of policies to encourage the use of renewable energy for electricity generation. Currently, the UK is falling behind other European countries in this respect. Hence, co-operatives play an important role in helping the UK to move forward. Co-operatives are of interest to the Government in respect of economic development in the community. Co-operatives keep both the business, or entity, and the wealth it creates locally, which also supports the local economy. Survival rates are higher for co-operatives, which will make them a more sustainable choice for businesses and have a positive impact upon employment opportunities. Co-operatives can be adapted to suit all types of situations, especially during difficult times such as the world economic downturn. This article explores the role energy co-operatives can play within the context of electricity generation in the UK. A review of the degree of exploitation of two leading and currently deployed renewable energy technologies is presented for key member states within the EU. This is followed by a discussion on the growth of the co-operatives and their role in meeting the aims of achieving a low-carbon economy.

Description: This paper presents the experimental results of a single cylinder Enfield engine using an electronically controlled fuel injection system which was developed to carry out exhaustive tests using neat compressed natural gas (CNG), and mixtures of hydrogen in CNG (HCNG) as 5, 10, 15 and 20% by energy. Experiments were performed at 2000, 2400 and 2800 rpm with wide open throttle and varying the equivalence ratio. Hydrogen, which has a fast burning rate, when added to CNG, enhances its flame propagation rate. The emissions of HC, CO, decreased with increasing percentage of hydrogen but NO x was found to increase. The results indicated a marked improvement in the brake thermal efficiency with the increase in percentage of hydrogen added. The improved thermal efficiency was clearly observed to be more in lean regions when compared with rich regions.

Description: Green roof is a passive cooling technique that stops incoming solar radiation from reaching the building structure below. Many studies have been conducted over the past 10 years to consider the potential building energy benefits of green roofs and have shown that they can offer benefits in energy reduction for winter heating as well as summer cooling. Green roofs have many benefits over conventional roofs: they reduce storm water run-off, the heat island effect in cities and energy requirements for cooling; all of this while sequestering some CO 2 from the atmosphere. But because of their expense, the building industry has yet to fully embrace their large-scale implementation. Over the summer', two test structures, one with a green roof and the other with an RCC roof, were built and tested at the Ujjain Engineering College, Ujjain, RGPV University, to determine their cooling potential. Results indicate that the test cell with the green roof consistently performs better than those with the conventional cement RCC roof.

Description: For better use of evaporative cooling techniques in humid climate, a desiccant cooling system (DCS) can be an alternative option in place of a conventional cooling system. This paper presents a theoretical comparative study of the performance of a DCS for four different climatic conditions of India (i.e. hot and dry, warm and humid, moderate and composite climates). From the analysis, it was found that the performance of a DCS is suitable in warm and humid climate. The thermodynamic equations of intermediate states of the desiccant cooling cycle are also presented. Effects of some parameters such as outdoor specific humidity, R / P ratio (regeneration air flow/process air flow) and power required to regenerate the desiccant wheel have been studied. The theoretical minimum R / P ratio has been computed for the maximum coefficient of performance (COP) of a DCS and its value was found to be 0.55 in Mumbai (warm and humid climate) for the 80% effectiveness of ECW. This paper also presents the relationship between COP and regeneration power with the different values of R / P ratios.

Description: This article studies in detail the permeation properties of highly permeable and highly selective polymer membrane for water vapor/volatile organic compound (VOC). A dense cellulose acetate (CA) membrane is prepared by the dry method. The sorption and permeation properties of water vapor and VOCs (acetic acid, formaldehyde, acetaldehyde, toluene and ethane) are experimentally investigated. Besides, the mass transfer coefficient of self-membrane can be separated from the total mass transfer coefficient. Using sorption and permeation data of gases, diffusion coefficient is calculated based on a solution–diffusion mechanism. The selectivity for water vapor/VOC is discussed and analyzed. The permeability selectivities of water vapor/VOC are all over 100. The result shows that the novel CA sense membrane is suitable for air dehumidification and total heat recovery.

Description: Building-mounted micro-wind turbines are capable of contributing a significant proportion of a building's energy needs. However, the introduction of this technology in built-up areas has been limited due to a number of issues, such as lower wind speeds, high turbulence and noise. This study presents an investigation into the effect of turbulence, which is more prominent in the built environment, on the operation of a micro-scale horizontal-axis wind turbine. For this purpose, an innovative method of sensing the yaw position of the wind turbine is required, which is discussed along with detailed methodology and the results obtained. The wind turbine used in the experiment uses a swing rudder system, and the effectiveness of this in turbulent conditions was also investigated. This study concluded that the wind turbine missed ~20% of the total power available in the wind and that the swing rudder system was suited to high wind speeds, while the fixed rudder suited to low wind speeds.

Description: Electricity production with an organic Rankine cycle and a transcritical Rankine cycle is investigated in this paper with R-123 and CO 2 as working fluids, respectively. The analysis focuses on the off-design behavior with different control strategies to show some of the occurring difficulties. It was found that both cycles need an advanced control strategy to avoid non-feasible operation (R-123) or significant losses in work output (CO 2 ). A challenge for the advanced control is the required large change in expander speed, which can lead to compatibility problems with the grid.

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: 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: 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: Results obtained from thermodynamic analysis of a solid sorption refrigeration system with and without internal heat recovery (IHR) employing ammonia as the refrigerant are presented. Four combinations of salts, namely MgCl 2 /SrCl 2 , MgCl 2 /CaCl 2 , CaCl 2 /SrCl 2 and CaCl 2 /CaCl 2 , are studied for systems with internal recovery. The system chosen is the one that can produce ice at –10°C using a waste heat source available at 613 K. Energy and entropy balance equations are applied to analyse each of the processes to estimate the individual heat transfer and entropy generation rates for all the systems. Effects of the sorbent and reactor mass are duly considered. Results show that among the four combinations studied, CaCl 2 /CaCl 2 cycle yields the highest coefficient of performance and specific cooling output per kilogram of the salt. Cooling/heating of the generator/absorber results in significant entropy generation in all the systems. IHR improves the performance significantly.

Description: This paper presents a feasibility study of a low-energy consumption ground source cooling system based on a periodic two-phase thermosyphon (PTPT) device in which a condensate is periodically transferred back to the evaporator. Operation of the PTPT is passive with the ground condenser positioned 1–11 m below the evaporator. The ground condenser may be at the condensing temperatures of 12–20°C depending on the ground depth. A semi-analytical approach is used to simulate the transient behaviour of the PTPT device. The simulation aims to study the effect of several parameters on the cooling rate of the device, including the length of condensing coil, the ground depth, the temperatures of the soil and the indoor air. The preliminary simulation results indicate that the PTPT device may be promising for ground source cooling applications.

Description: This comment analyses the relationship between climate law and environmental law. It examines this relationship from both a normative and a descriptive point of view. Normatively, it brings together various strands from some of the existing literature to form an overall model of the relationship—looking at ‘crowding out’, ‘crowding in’, ‘climate exceptionalism’ and adding in ‘climate unexceptionalism’. In descriptive terms, it considers, inter alia , ‘super wickedness’, instruments and governance, mitigation and adaptation.

Description: The polycentric, interdisciplinary, normative and scientifically uncertain nature of environmental problems leads to a body of environmental law in which it can be difficult to settle on a single frame for understanding a problem and thus to identify relevant parties, the relationships between them, and the courses of action that can be taken. Using Michel Callon’s terminology this can be understood as ‘hot situations’ leading to ‘hot law’. In this Introduction to the Special Issue celebrating 25 years of the Journal of Environmental Law the nature of ‘hot environmental law’ is considered, as is the role of environmental law scholarship.

Description: The launch of the Journal of Environmental Law coincided with the first proposals in England and Wales for a specialised environmental court or tribunal. Nearly 25 years later an environmental tribunal has now been established. The long saga provides an important reflection of competing visions of the role of environmental law, and a lesson in the role that chance and opportunism plays in significant policy development.

Description: This article considers the unwieldy state of UK environmental legislation in 2013, after 25 years of innovation, ad hoc reform and political change. It shows that an appraisal of UK environmental legislation involves considering much more than primary legislation emanating from Westminster—secondary legislation, devolved legislative instruments, policy documents and administrative norms all serve to constitute and inform the legislative picture. Through this wide analytical lens, the article considers legal problems that characterise UK environmental legislation today, from undermining of the rule of law due to its inaccessible complexity, to occupying an awkward place in public law terms. A particular problem is the fragmentation of legislation, and the article examines the case for integrating environmental legislation in a way that does not undermine the flexibility and institutional expertise that more focused legislation allows. The article offers not only a method for analysing the current UK environmental legislative landscape, but suggests routes for reform that might now be considered.

Description: In this article we consider the economic ideas that have influenced climate disruption law both in the USA and the EU. Although economic thought has led to the adoption of ‘market-based’ mechanisms in both places, its impact has been different: it created regulatory inertia in the USA, and green leadership in the EU—at least with respect to responding to climate disruption. We argue that different culture-specific economic conceptions about appropriate policy and policy analysis may help explain this divergence, thereby illustrating both various economic ideas and their distinct impact on climate law, as well as the need for environmental lawyers to engage with a discipline outside their own.

Description: The 25th Anniversary of the Journal of Environmental Law offers an opportunity to review the content of the Analysis section of the Journal, charting how it began life with an intention to report cases as well as to offer an analysis of them. The broad coverage of the section over 25 years is explored to allow discussion of the development of environmental law as a discipline over this time. In particular the role of a comment section is considered in an era in which news of legal developments and critiques of these are available contemporaneously from a multiplicity of sources. With this in mind, the future of Analysis is debated.

Description: During the two decades spanning the turn of the past century, the Court of Justice of the EU delivered a steady stream of preliminary rulings and judgments in actions for infringement that related to important and novel legislation on waste and environmental impact assessment. This article considers the significant contribution made by these cases, both to the interpretation of fundamental specific concepts underpinning both the Waste Directive and the Environmental Impact Directive and to the development of general principles of EU law in fields such as the direct effect of directives, aspects of implementation of directives, and judicial protection and enforcement. In the context of both the particular legislation at issue and the general principles relevant to its application, the Court’s rulings in these superficially narrow areas have dramatically advanced the scope and effectiveness of the directives and the evolution of critical principles.

Description: This article explains and analyses key trends in the environmental jurisprudence of international courts and tribunals over the past decade. It starts by discussing the different jurisdictional bases that are available to bring environmental claims at the international level, as well as some of the problems that arise from the current consent-based system of international dispute settlement. The article then turns to examine the growing cross-fertilisation that is evident in the environmental case law. The article provides examples of this phenomenon in relation to the interpretation of substantive rules on environmental protection and in relation to the development of procedural mechanisms to deal with certain challenging aspects of environmental litigation.

Description: The book review is assumed in some quarters to be vulnerable to the many other pressures that supply the ether of the modern academic world. This article offers an avowedly upbeat view, arguing that the review is not only surviving but that at its best it affords distinct advantages, not available in other formats, in the marshalling and wider dissemination of information and narrative argument. The analysis offers both a general perspective and one that is mindful both of experience across 25 years of the Journal of Environmental Law and of the vital demands for a lively and informed wider discourse in and around the field of environmental law.

Description: This article considers how far the climate change regime is an exemplar of international environmental law as well as public international law. We focus on five issues: the nature and extent of differentiation in favour of developing countries, the role of soft law, the dynamics of decision-making in multilateral negotiations, the contribution of dispute settlement, and the impact of (and assumptions underlying) scholarly offerings in this field. This article argues that the climate regime has both benefited from normative developments elsewhere as well as contributed to such developments (for instance, as regards the use and absorption of soft law within the regime). The article concludes with a reflection on legal scholarship and climate change and seeks to externalise the challenges, demands, choices and values of those who contribute to the discussion, to recognise the benefit of diversity.

Description: The article considers domestic environmental case law decided between 1989 and 2013. In 1989, the term ‘environmental law’ was hardly recognised in academic or practitioner circles and environmental litigation remained quite undeveloped in the United Kingdom. Twenty-five years on, environmental law is a distinctive and mature specialism. Environmental cases decided between 1989 and 2013 reveal three broad themes: the development of domestic environmental law has been dominated by European Union law; environmental public law has become a distinctive body of public law; and there are ongoing tensions between the role of statutory regulation and the common law in protecting the environment. The article discusses the themes and how they have developed before concluding with a selection of the top five cases over the past 25 years.

Description: This article is about how we look at EU chemicals law. It brings together the past and present of five decades of EU chemicals law in the hope that it may lead to a better understanding of the future potential and evolution of law in the area. The article tells a story of EU legislative centralisation, colonisation and standardisation. We argue that these historical trends have aroused certain expectations about the role and functioning of modern EU chemicals regulation in REACH. These expectations, we argue, are often unrealistically high, misplaced or at times unnecessarily low. The challenges set out in our article suggest that EU chemicals regulation in its current form is set up largely to fail. Moreover, we argue that these problems make a case for the radical reorientation of regulatory goals, values and practices and indicate that the biggest challenge in chemicals policymaking is not necessarily to meet expectations but to manage them more effectively.

Description: This article is intended to be a primer on the LNG industry and project structuring. Given the recent focus on gas and LNG as an energy source, the article first describes LNG, how the international LNG industry developed, LNG's importance and the ‘LNG chain'. Next, the article discusses how a typical LNG project is structured, the reasons why a particular structure is chosen, the critical contractual agreements utilized in these structures and some common structuring issues. Last, the article notes trends in the LNG industry of possible importance to those structuring, negotiating or documenting future LNG projects. The article was prepared based on author Philip Weems' more than 20 years experience in the LNG industry and both authors' recent participation as legal counsels to many of the LNG projects currently under development.

Description: The global energy requirement for sustaining economic activities, meeting social needs and social development is increasing daily. Environmentally friendly, 1 renewable energy resources are an alternative to the primary non-renewable energy resources, which devastate ecosystems in order to meet increasing demand. Among renewable energy sources such as hydropower, biopower, geothermal power and solar power, geothermal energy power offers distinct advantages to Turkey. There is an increasing tendency towards geothermal energy globally and the European Union has adjusted its legal regulations in this regard. As a potential EU Member state, Turkey is going through a similar process. The number of institutional and legal regulations concerning geothermal energy power has increased in recent years; technical infrastructure studies have been completed and some important steps taken in this regard. This study examines the way in which Turkey has developed support for geothermal energy power, presents a SWOT analysis of the geothermal energy power sector in Turkey and makes a projection for the concrete success expected to be accomplished in the future.

Description: The objective of this article is to promote global energy security by evaluating the existing patchwork of institutions and processes linked to the governance of the global energy economy. What we mean by ‘global energy security’ is the satisfaction of humankind’s energy needs to maintain lifestyle levels in the developed world and to promote development and improve the quality of life across the world, including least-developed and developing countries. The article focuses on the global energy economy, its fragmented governance and its implications for global energy security. Inter-State governance over the global energy economy is neither global nor cohesive. Rather, the various aspects pertinent to it—among others, economic development, climate change, trade, investment protection, finance and human security—are managed in a disparate and disjointed manner. What is more, the absence of a global energy security regime to address ‘global’—ie humankind’s collective—energy needs justifies the need to investigate the implications of the current state of play for global energy security. To do so, the article will examine all relevant institutions and processes linked to the global energy economy in order to assess their individual and combined implications for global energy security. This article therefore aims to promote an understanding of, and an attitude towards, the global energy economy that acknowledges that it is a composite affair with a high degree of interplay between its constituent parts, and that there are systemic reasons why the current state of play fails to address global energy security needs. The aim of the article is to perform an extensive mapping-out and analysis of the institutions and processes linked to the governance of the global energy economy, and of those purportedly concerned with global energy security, in order to answer the following three questions: How does the current governance system of the global energy economy affect global energy security? What challenges does the current global energy governance system pose to global energy security? Which models of global energy governance should be applied to promote and improve global energy governance generally and global energy security in particular?

Description: Disagreements regarding the role to be played in oil and gas activity by Iraq’s Kurdish regional and provincial governing structures always exist as a potential complication to the important contribution which that nation is capable of making to world oil and gas supplies. The principal touchstone for such disagreements resides in the terms of provisions of Iraq’s 2005 Constitution. Of especial significance are the Constitution’s articles 112 and 115, as well as the relationship between that instrument’s article 143, and its pulling-in of articles 25(E) and 53(A) of the Constitution’s predecessor document, the so-called Transitional Administrative Law. Examining the complexities of and interplay between these articles reveals a legal architecture vesting the federal government in Baghdad with powers over certain oil and gas activities, leaving other activities to the regional and provincial governments, and still others in a situation where the accuracy of assertions of regional and provincial governmental power is less than clear. A further complication to this constitutional architecture is the fact that specific interpretations of relevant legal provisions even suggest the possibility of differences in legal regimes dependent upon whether exploitation is from resource deposits found in certain named Kurdish provinces as opposed to others.

Description: Heat pump features can take advantage of better sources than air, for instance the ground heat, solar heat and heat recovery. A multisource system aims to enhance the performances of the heat pump, leading to a significant amount of primary energy being saved. The present work shows data monitoring and analysis for a real working application in northern Italy, for 12 months. The energy balance indicates that the integration of different sources not only increases the thermal performance of the system as a whole but also optimizes the use of each source.

Description: The process of the impinging of a droplet upon a heated flat solid surface was computationally studied to identify the key process occurring in a liquid droplet. A computational fluid dynamics model, based on the volume of fluid (VOF) approach, was used to simulate the impact of droplet dynamics on the heated flat solid surface. Surface tension and wall adhesion phenomena were taken into account in this model. The model was proved effective by comparing the simulation results with the experimental data in the literature. It could be concluded that the VOF-based model was able to simulate the dynamics of the impinging of a droplet upon a heated solid surface. The key characteristics of droplet evaporation and the interaction between the droplet and the solid surface could be captured.

Description: An interesting application of agricultural renewable sources is the use of ethanol for supplying molten carbonate fuel cells (MCFCs). However, ethanol has to be converted into hydrogen by a steam-reforming process. MCFCs are suitable for these applications due to their tolerability to the impurities of the reaction products and their high working temperatures (600–650°C) which allow to integrate the reforming stage to the stack. Ethanol-reforming tests were performed by using pure ethanol or bioethanol obtained by sugar beet syrup fermentation. Tests were performed by a specific reactor designed for its installation into the anodic compartment of small-size MCFCs.

Description: An experimental setup is devised to investigate the behaviour of a novel type of a horizontal ground heat exchanger (HGHE). The prototype is named ‘flat panel’ and is coupled with a hydraulic closed loop in which warm water is circulating to express the cooling mode from a reversible-cycle heat pump. Several thermal sensors are employed in the experimental field to monitor the ground temperature distribution and the fluid. The behaviour was tested during the summer of 2011, in the continuous and discontinuous operating mode. The HGHE behaviour was monitored in dry and wet conditions; the latter were induced with a dedicated irrigation system. The heat power for the unit exchanging surface dropped down from 140 to 40 W per metre of trench, moving from the start-up to the last period, late in the summer. The minimum was achieved in very hot conditions after long time in the continuous operating mode. When the working mode was switched to discontinuous, the power increased quickly over 50 W/m. Finally, the soil temperature was significantly altered up to 3 m far from the exchanger, and without over-heating conditions at the soil surface. The flat panel was able to involve a large soil volume, and this behaviour in turn enables high-energy performance, at least in the cooling mode.

Description: This paper presents a comprehensive and state-of-the-art review on thermochemical energy storage (ES) technologies using thermochemical materials (TCMs) for building applications. Thermochemical storage devices (materials, open and closed sorption as well as chemical heat pump) enhance the energy efficiency of systems and sustainability of buildings by reducing the mismatch between supply and demand. Thermal ES (TES) systems using TCMs are particularly attractive and provide a high ES density at a constant temperature. Technical and economical questions will need to be answered for all possibilities, which warrant more development and large-scale demonstration of TES in future.

Description: A computer program has been developed for numerical simulation of the dynamic thermal performance of horizontally coupled heat exchangers for ground-source heat pumps, taking account of dynamic variations of climatic, load and soil conditions. The program was used to investigate the effects of operating and start times, installation depth and soil freezing on the heat exchanger performance. It is shown that the rate of heat extraction decreases with increasing operating time. Operating a heat pump with an earlier start date in autumn would give rise to a higher amount of cumulative heat extraction. Also, a heat exchanger installed at a shallower depth can provide a larger heat extraction rate at the early stage of heating operation. In addition, soil freezing enhances heat extraction.

Description: Experimental field tests as well as laboratory tests have been conducted. In addition to field tests, a geothermal laboratory device has been developed. With the help of this device, the heat transport processes in different geological and hydrogeological conditions can be simulated. The different types of heat transport mechanisms in geothermal systems can be characterized clearly. Furthermore, it is possible to determine the increase of the effective thermal conductivity of a line source with rising groundwater flow velocities. With the geothermal data gathered, common numerical programs are verified and optimized. Therefore, all measured data are reconsidered by numerical back analysis.

Description: This study reviewed the current situation of carbon capture and storage (CCS) development in the UK, mainly within the last 10 years in general. It looked at the positive ways to implement the CCS technologies, including the geological advantages, potential sector growth, financial incentives and the support in the policies. Current projects were brought forward together with university and industry research. Some concerns and limitations of applying CCS technologies were discussed. Finally, the conclusion was made that the UK is in a good position to implement CCS technologies and would become a global leader in CCS development, providing that the first four trials were successful.

Description: The optimal configuration of the expansion process of a heated ideal gas inside a cylinder for maximum work output with a movable piston and time-dependent heat conductance is determined in this paper. The heat conductance of cylinder walls is not a constant, but depends on the time-dependent heat transfer surface area of the walls in contact with gas. Euler-Lagrange formalism is applied to obtain the optimal process that maximizes the work output of the working fluid with fixed initial energy, initial volume, final volume and total time allowed for the expansion. The method of exhaustion is applied to determine the optimal initial value of internal energy of the Euler-Lagrange arc. Numerical examples for the optimal configurations with time-dependent heat conductance are provided, and the obtained results are compared with those obtained with constant heat conductance. The results show that the optimal initial value of internal energy of the Euler-Lagrange arc, the time corresponding to the maximum optimal internal energy and the time spent on the compression process with time-dependent heat conductance are quite different from those obtained with constant heat conductance. In addition, the volume and internal energy along Euler-Lagrange arc obtained with time-dependent heat conductance are much sharper compared with those obtained with constant heat conductance.

Description: As electricity networks are being transformed in order to enhance their flexibility and ability to adapt to low-carbon energy sources, there is more emphasis on demand-side management. The electricity demand can be modelled based on the bottom-up approach. The UK Time Use Survey 2000 data are used to create a model for electricity demand. By introducing a new filter when processing the Time Use data, the effect of seasonal variation on active occupancy and electricity demand has been investigated and presented here in this work.

Description: Transcritical expansion through coiled adiabatic capillary tubes having CO 2 as the refrigerant is numerically simulated, and the performance is compared with the flow of R22 through such tubes. Mori and Nakayama friction factor correlation in combination with Churchill equation, which is fitted into the form of Blasius type equation, is employed to estimate the friction factor. Results indicate that the reduction in the mass flow rate with a coiled capillary tube compared with a straight one is more pronounced in case of R744 in comparison to R22. The mass flow rate of refrigerant increases as the coil diameter increases, but changes little beyond a coil diameter of 180 mm. Variation in gas-cooler exit temperature does not lead to any significant change in variation in the mass flow rate with coil diameter. A shorter capillary tube will be required to match the requisite system mass flow rate when coiled capillary tubes are employed in lieu of a straight one.

Description: Groundwater flow plays an important role in affecting the thermal performance of borehole heat exchangers (BHEs). In the present work, a few field tests are conducted in Shouguang, China, to compare the thermal performance of three BHEs in different aquifers. The results show that there is a good linear correlation between the heat transfer rate of BHEs at steady state and the average fluid temperature. A larger slope usually means a higher heat transfer rate of a BHE, under the same borehole conditions. The thermal performance of BHEs is extremely enhanced, especially in those regions with multiple aquifers, and even the thermal response test results can be enlarged to a great extent by groundwater flow. The enhanced effect of groundwater flow depends mainly on the amount, thickness and depth of aquifers. It is found that when the depth of aquifers covers the middle or lower part of BHEs, at least exceeding the depth of the constant temperature ground layer, the enhancement on the thermal performance of BHEs becomes more intense due to the increase of the heat transfer temperature difference and the decrease of the total thermal resistance from the inner fluid to the surrounding ground. Groundwater flow in aquifers is helpful to reduce the required length of BHEs and the construction cost of ground source heat pump systems.

Description: The efficient power, defined as the product of the power output and efficiency, is taken as the objective for performance analysis and optimization of an ideal air-standard Atkinson cycle with variable specific heats of the working fluid. Performance analysis is carried out in the viewpoint of finite-time thermodynamics or entropy generation minimization. Results obtained are compared with those obtained by using the maximum power (MP) and MP density (MPD) criteria, and the advantages and disadvantages of a maximum efficient power (MEP) design are analyzed. The result showed that the engine designs at MEP conditions have an advantage of smaller size over those designed at MP conditions and are more efficient than those designed at MP and MPD conditions. Moreover, engines designed at MEP conditions require lesser pressure ratio than those designed at MPD conditions.

Description: This paper deals with energy and exergy analyses of a multi-flash integrated system and studies three efficiency definitions for system assessment. In this regard, a comparative performance evaluation is conducted to investigate the effects of using these energy and exergy efficiencies on the assessment of a triple-flash integrated system with an electrolyzer. Parametric studies are conducted to investigate the effect of rise in the ambient temperature and geothermal source temperature on these energy and exergy efficiencies. The results show that the efficiency definition plays a critical role as the efficiency value differs from one definition to another. Increasing the ambient temperature decreases both energy and exergy efficiencies based on the first definition, but increases them based on the second and third definitions. An increase in the geothermal source temperature reduces both energy and exergy efficiencies based on the first definition, but increases them based on the second and third definitions of efficiencies. The energy and exergy efficiencies of the overall system based on the third definition are found to be increasing from 0.6 to 2.2% and 6.5 to 47.29%, respectively.

Description: Adoption of clean energy technologies is fundamental to equitably support and sustain a burgeoning population, particularly in progressive nations such as India. While solar represents the most ubiquitous energy source, its appropriate harnessing mechanism requires a careful approach and design. Amid the various direct and indirect electricity generation techniques available, building-integrated photovoltaic (BIPV) carries immense potential to harness solar energy integrated as a component of the building envelope. It is an onsite-distributed power source, offering advantages of size and scale variability, modularity and building integrability. To be energy efficient as a building envelope, BIPV would need to passively regulate the responsiveness of the building envelope to the external environment to accomplish the prime function of a building, i.e. to provide (natural) indoor thermal-comfort for conducive and productive living. However, the requirements for climate-responsive building design may infringe upon those required for optimal PV performance. Besides technological considerations attributed to varying PV (material-dependent) performance efficiencies and high initial investment, a pragmatic approach should also integrate social, environmental and economic factors for successful adoption of a BIPV. It would, thus, require addressing the design requirements for energy-efficient building performance, effective PV integration and societal feasibility. This article attempts to provide an integrability framework encompassing the climate responsiveness factors influencing BIPV performance, which can support further research in this arena.

Description: This paper reports on an experimental energy storage system, consisting of a longitudinally finned concentric container incorporating 98 kg of RT58 phase change material (PCM) with a melting point of 60°C. The research forms part of a wider study to explore PCMs to take advantage of off-peak electricity tariffs. The experimental study results have been reported using temperature time curves, isotherm plots, trend of heat transfer coefficients based on quantitative amounts of energy charged and discharged from the PCM. Isotherm plots indicated uneven heat distribution and the charge and discharge rates of energy averaged 0.6 and 0.2 kW, respectively, prompting the need to develop a more efficient heat transfer technique to improve charge and discharge rates. Increased average inlet heat transfer fluid temperature from 60.9 to 65.9°C improved heat transfer coefficient by as much as 70% for charging and 11.3% for discharge process.

Description: This paper presents the preliminary experimental results of a liquid desiccant cooling system driven by the flue gas waste heat of a biomass boiler. The desiccant cooling system is mainly composed of a regenerator, a dehumidifier and an evaporative cooler. The flue gas waste heat is applied to the regenerator to regenerate the desiccant solution. The environmentally friendly liquid desiccant potassium formate (HCOOK) solution is used in the dehumidifier for air dehumidification due to its less corrosion, lower cost, lower density and lower viscosity. A cross-flow heat and mass exchanger for indirect evaporative cooling is adopted in the evaporative cooler to ensure that product air meets the indoor air quality and thermal comfort standard. The desiccant cooling system operated in Autumn days in Nottingham was found to be able to decrease the air temperature by 4°C and reach a cooling capacity of up to 2381 W. Moreover, the dehumidifier is able to reduce the relative humidity of the humid air by 13%. The biomass boiler's flue gas waste heat extracted and supplied to the regenerator was found to be 554 W, which is insufficient to regenerate the dilute liquid desiccant solution under current experimental conditions. To obtain sufficient heat to regenerate the liquid desiccant, the existing first-of-its-kind concentric helical coil heat exchanger extracting the waste heat of the boiler needs to be redesigned, and, in particular, the concentric helical coils of the heat exchanger need to be placed inside the chimney to enhance the waste heat extraction.

Description: Pressure to slash CO 2 emissions continues to mount with growing levels of legislation and incentives to preserve our environment. To meet these targets, considerable research into renewable energy sources and energy efficiency is underway. Thermal energy storage (TES) systems offer attractive properties, enabling economical energy utilization within the built environment. Phase change material (PCM) has become a forerunner in the TES field due to its high-energy storage densities (~10 times that of concrete). An extensive review of PCM technology has been undertaken, with specific attention to TES applications within the built environment, assessing the capability of PCM.

Description: Pressure to slash CO 2 emissions continues to mount with growing levels of legislation and incentives to preserve our environment. To meet these targets, considerable research into renewable energy sources and energy efficiency is underway. Thermal energy storage (TES) systems offer attractive properties, enabling economical energy utilization within the built environment. Phase change material (PCM) has become a forerunner in the TES field due to its high-energy storage densities (~10 times that of concrete). An extensive review of PCM technology has been undertaken with specific attention to TES applications within the built environment, assessing the capability of PCM.

Description: The use of the heat pipe as a component in a heat recovery device has gained worldwide acceptance. Heat pipes are passive, highly reliable and offer high heat transfer rates. This study summarizes the investigation of different types of heat pipe heat recovery systems (HPHRSs). The studies are classified on the basis of the type of the HPHRS. This research is based on 30 years of experience on heat pipe and heat recovery systems that are presented in this study.

Description: Water thermal stratification exists in the discharging process of solar storage tanks, and a high efficiency of thermal stratification can greatly improve the discharging performance of solar tanks. The water tank with dimensions of 0.8 m (height) x 0.4 m (width) x 0.4 m (length) and three kinds of inlet structures were investigated in this study. The inlets included a perforated inlet, slotted inlet and direct inlet. The discharging performance of the tank was studied by presenting some compared experiments. The dimensionless discharging time was defined to analyze the temperature change of top-layer and inter-layer of water. Quantitative analysis and comparison based on the effective discharging efficiency and carbon reduction in the tank with different inlet structures were carried out in this study. The results indicated that the perforated inlet and slotted inlet improved the performance of thermal stratification effectively. The effective discharging efficiency of the perforated inlet structure was 21% higher than that of a direct inlet with the flow rate of 5 l/min and the gap increased to 40% when the flow rate increased to 15 l/min. The application of the perforated inlet tank in the discharging process in all solar water heaters in China can provide a CO 2 reduction of 5.39 x 10 4 t compared with the direct inlet tank.

Description: A generalized finite-time thermodynamic model of irreversible multi-element thermoelectric generator is established taking into account inner and external factors. The inner effects include Seebeck effect, Fourier effect, Joule effect and Thomson effect. The irreversibility is caused by the finite-rate heat transfer between the heat reservoirs and the device. The theoretical iterative functions of the hot and cold junction temperatures and energy equations are obtained. The model is applied to the analysis of a multi-element thermoelectric generator, which is made of typical thermoelectric materials. It is found that, for given other parameters, there is an optimal electrical current, an optimal length of thermoelectric elements and an optimal ratio of thermal conductance allocation corresponding to the maximum power output. Thus, internal and external simultaneous multivariable optimizations are performed for a maximum power output. The effects of several important parameters on the optimal variables are analyzed in detail. The comparison between the optimized power and the non-optimized power shows that the multivariable optimization is necessary and effective for various working conditions. The model and optimization conclusions obtained herein can be applied to not only the analysis and optimization but also the design of thermoelectric generators.

Description: In this study, we survey the alternative approach of using plasma technology to produce CO x free hydrogen. In a corona discharge reactor operating at atmospheric pressure, electrons were energized by an electric field to ionize propane and induce chemical reactions. A range of each test parameter was covered, namely the effect of power input in the range of 4.5–105 W and discharge time of 1, 2, 3, 4, 5 and 8.18 min. A 19% hydrogen content by volume was achieved at a power input of 102 W and discharge time of 8.18 min.

Description: The results of five thermal response tests (TRTs) are presented. Three of the tests were carried out consecutively on the same borehole to illustrate the importance of allowing artificially imposed thermal gradients to dissipate prior to commencement or re-commencement of a test following testing issues. The two remaining tests carried out on separate boreholes confirm the results obtained by the first (uncompromised) of the initial three tests. The testing regime demonstrates the necessity of careful performance of TRT's and shows the variation in costs/required borehole length which may occur if testing problems occur on site.

Description: This article presented a theoretical analysis of the heat transfer limits associated with a gravitational loop heat pipe (LHP), which involves the utilization of an innovative liquid feeding/distributing and vapour/liquid-separating structure. The mathematical equations governing the heat transport capacity were applied to simulate several commonly known heat transfer limits of the pipe, namely, viscous, sonic, entrainment, capillary, boiling and liquid filling mass limits. This will allow the determination of the actual figure of the limitation and analyses of the factors effecting the limits, including the loop operational temperature, wick type, evaporator diameter/length, evaporator inclination angle, vapour column diameter in the three-way fitting, liquid filling mass and evaporator-to-condenser height difference. During the study, the heat-transfer limits associated with the three-way fitting for liquid feeding/distribution and vapour/liquid separation were given particular attention. The results derived from the analytical model indicated that the compound screen mesh wick can achieve better thermal performance over the sintered powder and open rectangular groove wicks. It was also found that the heat transport capacity of such LHP operation is positively proportional to the operational temperature, evaporator diameter, evaporator inclination angle, vapour column diameter within the three-way fitting, liquid filling mass and evaporator-to-condenser height difference, and in a reciprocal order to the evaporator length. With the specified loop configuration and operational conditions, the LHP can achieve a high heat transport capacity of around 900 W. Overall, the work presented in this article provided an approach to determine the heat transfer limitations for such a specific LHP operation that will be of practical use for the associated system design and performance evaluation.