ALBERT

Description: Low-temperature methane and methanol steam-reforming catalysts Ni/Al 2 O 3 , Cu/Al 2 O 3 and Ni–Cu/Al 2 O 3 with various loadings of Ni and Cu were prepared using a wet impregnation method. The samples were characterized using scanning electron microscope, surface area (BET) test, X-ray diffraction (XRD), infrared test, CO chemisorption test and temperature-programmed reduction tests. XRD testing showed that NiO and CuO were present. Ni–Cu-alloyed catalyst shows a significant change in the catalyst characteristics compared with those of individual metals. The results presented in this paper show the main changes in the catalyst properties using ex situ testing.

Description: In this paper we report the synthesis of a series of new Mn/Ti containing perovskites, La 1– x Mn x Mn 1– x Ti x O 3– , for investigation of their potential for use as solid oxide fuel cell electrodes, particularly anodes. Single-phase samples could be achieved for x ≤ 0.4. Above this level, La 2 Ti 2 O 7 impurities were found. Conductivity measurements showed electronic conductivity up to a maximum of 12 S cm –1 at 850°C in air. While the samples were shown to be stable in both air and 5% H 2 /N 2 , the conductivities in the latter were significantly lower (0.4 S cm –1 ), which would be an issue for potential anode applications.

Description: In this paper, using lithium chloride and calcium chloride as modifying agents, the modified silica gel and molecular sieve composite based on ceramic fiber was prepared by treating ceramic fiber paper with sequential impregnation of the suspension of waterglass and molecular sieve and the aqueous solution of salt. The composition of the modified composite was characterized by using Fourier transform infrared spectroscopy (FTIR). Thermogravimetry (TG) and temperature programmed desorption (TPD) were used to evaluate the desorption performance of the composite. FTIR spectra indicated that impregnation salt has no effect on the composition of molecular sieve. TG and TPD analysis indicated that desorption activated energy of modified composite was lower than that of molecular sieve. The result of the dynamic and static adsorption experiment showed that the adsorption performance of molecular sieve enhanced greatly through the modification.

Description: In the present work, the process of synthesis of methyl esters from Jatropha curcas crude oil as an alternative vegetable oil, using a two-step catalyzed process is shown. In the first step, sulfuric acid was used as a catalyst for the esterification reaction of free fatty acid (FFA) and methanol in order to reduce the FFA content to ~0.2%. In the second step, the product from the first step was further reacted with methanol using potassium metoxide as a catalyst. The two-step processes have been developed and optimized by application of the factorial design and response surface methodology. The optimum conditions for biodiesel production were obtained when using methanol to FFA contents of Jatropha crude oil molar ratio (MR) of 20:1, 5 wt% of sulfuric acid, at 60°C with a reaction time of 60 min in the first step, followed by using an MR of methanol to product from the first step of 6:1, 0.95 wt% of KOCH 3 , at 45°C with a reaction time of 60 min in the second step. The percentage of methyl ester in the obtained product was more than 98%. The model has been found to describe the experimental range studied adequately and allows us to scale-up the process. In addition, the fuel properties of the produced biodiesel were in the acceptable ranges according to EN14214 European biodiesel standards.

Description: Adsorption heat transformation (AHT) is one of the challenging technical approaches for supporting the world community initiatives to alleviate or reverse the gravity of the problems arising from CO 2 emissions and global warming. The key tool for enhancement of the AHT efficiency and power is a harmonization of adsorbent properties with working conditions of the AHT cycles. It can be realized by means of target-oriented designing the adsorbent specified for a particular AHT cycle. Two-component composites ‘salt in porous matrix’ (CSPMs) offer new opportunities for nano-tailoring their sorption properties by varying the salt chemical nature and content, porous structure of the host matrix and synthesis conditions. CSPMs have been recognized as promising solid sorbents for various AHT cycles, namely adsorption chilling, desiccant cooling, heat storage and regeneration of heat and moisture in ventilation systems. In this review, we survey a current state-of-the-art and new trends in developing efficient CSPMs for various AHT cycles.

Description: In this article, we outline and review the methods that are currently used to simulate the micro/meso-scale flow and reactive transport processes in the porous catalyst layers (CLs) of a fuel cell. The approaches beyond the atomic scale (molecular dynamics) and below the conventional continuum scale (Navier–Stokes solvers) use coarse-grained pseudo-particles which can either move on a fixed lattice or continuously in space. The focus is mainly put on the development of the off-lattice pseudo-particle models, such as coarse-grained molecular dynamics (CG-MD), dissipative particle dynamics (DPD) and smoothed particle hydrodynamics (SPH) methods. As an example, a CG-MD method is performed as a microscopic structure reconstruction technique to reflect the self-organized phenomena during the formation steps of a CL. In addition, we also highlight the combined nano-scale elementary kinetic processes and the issues on the coupling of DPD and SPH to finite element (FE) modeling techniques. This article also highlights the critical aspects and addresses the future trends and challenges for these models.

Description: Novel binderless zeolite beads of types A and X have been synthesized and characterized by scanning electron microscopy, mercury intrusion, nitrogen adsorption, thermogravimetry, water adsorption isotherm measurements, cyclic hydrothermal treatments and storage tests. The binderless molecular sieves show an improved adsorption capacity, sufficient hydrothermal stability, higher specific energies and the potential for a better performance density of the storage. Both open and closed storage tests have shown comparable adsorption capacities and specific energies for the binderless molecular sieves. A significantly higher discharging temperature, however, could be realized with the open storage system.

Description: Climate change may seriously affect the energy consumption of buildings by influencing their air conditioning loads, especially the ventilation loads which vary directly with the local weather conditions. Research on how the ventilation load responds to climate change is of great significance, especially in coastline subtropical regions like Hong Kong. This paper investigated the impacts of climate change on buildings' ventilation load and building energy use in Hong Kong with the hourly meteorological data from 1950 to 2007. Results have been well validated by the simulation of a typical local hotel building during this period. The results show that climate warming increases both sensible and latent parts of the cooling ventilation load. The latent part, which occupies ~80% of the total ventilation load, increases at a higher rate, about twice of that of the sensible one. Furthermore, it is found that the urban heat island (UHI) effect causes a much higher growth rate of the ventilation load at night, which is about three times compared with that in the daytime. The latent part of the cooling ventilation load at night, which is found to be the most sensitive component to the climate change, plays a most significant role in the energy consumption increase. The possible measures were thus suggested to avoid negative changes of the ventilation load. Besides, reducing the UHI effect by better urban planning also significantly benefits the local buildings with a long air-conditioning operation time.

Description: This paper presents a numerical simulation of the fluid flow and heat transfer in the shell-side of a large-scale shell-and-tube heat exchanger with longitudinal flow through porous-medium and distributed-resistance model. Such characteristics as flow field distribution, shell-side pressure drop, heat transfer performance and overall performance factor of the shell-side were studied with change in L / D and Re . It was shown that when L / D decreased from 6.0 to 1.5 with the same Re , the fluid flow maldistribution became intense, pressure drop increased sharply, and that the overall performance factor decreased sharply. Particularly, when L / D ≤ 2.0, the problems became more and more serious. Through a detailed analysis of the pressure field distribution, it was discovered that 〉80% of the total pressure drop occurred in the region of the inlet and the outlet, where the fluid flow mainly cross the tube bundle. In order to solve the problems, the use of a novel structure of multi-parallel-channel inlet and outlet (MPC) in the shell-side was proposed. A comprehensive investigation showed that MPC is very effective not only in optimizing the fluid flow distribution of the shell-side and enhancing the global heat transfer performance of a heat exchanger, but also in decreasing shell-side pressure drop.

Description: Renewable energy has gained great attention and interest in recent years due to growing energy consumption and greater environmental concerns. Biomass is regarded as a promising candidate for replacing fossil-derived products, through either thermal, biological, or physical processes. This review focuses on thermal processing of biomass in molten salts for production of renewable fuels and chemicals, concepts based on dispersion of biomass or waste particles in a molten salt bath. Inorganic salts have very high heat capacities and good thermal stability at high temperatures. Some molten salts have catalytic properties, and in thermal processing of biomass, the product yields and compound compositions of products can be adjusted by varying compositions and amount of molten salts. In addition, molten salts will retain noxious contaminants, and it is thus possible to use difficult convertible- and/or contaminated biomass as feedstock.

Description: Reed canarygrass is a temperate perennial grass of interest as a bioenergy crop. The canarygrass was evaluated for conversion to bioethanol using liquid hot water and dilute ammonia pretreatments prior to fermentation. The resulting hydrolysates were evaluated for production of ethanol, xylose and soluble xylans. Dilute ammonia gave higher yield efficiencies than liquid hot water. The optimal condition for dilute ammonia (4% w/v) pretreatment was 170°C for 20 min. Hydrolysates were converted to ethanol using Saccharomyces in the presence of a blend of commercial cellulases and additional carbohydrases. The final ethanol conversion efficiency was 84% based upon total hexosans, with 72% of the xylan converted to soluble xylan oligomers.

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: In general, the raw product gas of biomass gasification contains a range of minor species and contaminants, including particles, tar, alkali metals, chlorine, nitrogen compounds and sulphur compounds. This study reviews the recent developments in product gas cleaning technologies for these species and summarizes the findings of the research project ‘Mop fan and electrofilter: an innovative approach for cleaning product gases from biomass gasification’ which was recently carried out by the authors. The results of the project showed that combination of mop fan and electrofilter (ESP) has great potential in removing fine particles, tars and chemical contaminants in the product gas.

Description: Low energy efficiency and limitations of cooling temperatures in the ejector refrigeration systems (ERSs) are major obstacles for its widespread use. The application of binary or multicomponent fluids may prove to be one of the successful ways to increase the ERS performance by 30–50%. Zeotropic mixtures, which have unlimited solubility and evaporate at specified pressures and varying temperatures, are considered as possible candidates to be applied in a binary-fluid ERS (BERS). An ideal candidate working fluid should exhibit high molecular weight, low latent heat of evaporation, high normal boiling temperature and high compressibility factor. A refrigerant fluid should have low molecular weight, high latent heat of evaporation, low boiling point and compressibility factor. BERS pursues simultaneous achievement of two main goals: increase in system's efficiency and take the condensation point up to 45–50°C at fixed coefficient of performance, i.e. employ atmospheric condenser in ERS. This article presents schematic diagrams of a multicomponent-fluid ERS; its cascade principle based on BERS enables to produce cold at several temperature ramps, using renewable or low-grade heat sources. Research outcomes from this article can improve the effective application of ejector technology.

Description: This paper presents a novel model to evaluate the electrical performance of a silicon photovoltaic (PV) module with respect to changes in main environmental parameters such as temperature and illumination intensity. A simple one-diode model is proposed to estimate the electrical parameters of PV module considering the series resistance and shunt conductance. Effects of PV module parameters on current–voltage characteristic curve are investigated. The proposed model also makes a thermodynamic assessment concerning the effects of environmental and electrical parameters on efficiency and maximum power output of the PV module. Kyocera KD205GH-2P 205-W high-efficiency multi-crystal PV module is used for model evaluation. Model results are compared with the manufacturer's data report and an excellent agreement is observed.

Description: Several solutions are currently being tested to improve the thermal efficiency of ground heat exchangers (GHEs) employed in geothermal closed loops. For shallow exchangers, the main effort is towards maximizing the surface available for heat exchange, while reducing the interference among exchangers; popular solutions towards this end are the slinky coil and the radiator shape. Recently, the flat panel has been proposed as a novel alternative to horizontal exchangers. In this study, the performance and thermal impact of the radiator and flat panel installations are compared by solving the transient flow and heat transport problem within the surrounding ground via a numerical model. Adopting the same computational conditions, the two installations yield different resulting domain thermal fields. The flat panel shows a higher capability to affect larger volumes of surrounding ground, so the soil temperatures reach values less extreme than in the radiator case. Since horizontal GHE temperatures remain 2–3° warmer in winter time, a higher coefficient of performance is expected for the flat panel.

Description: In this study, energy–exergy–environmental–economic (4-E) analyses of stand-alone line-focusing concentrating solar power plants are carried out for different plant capacities ranging from 1 to 50 MW e . Solar power plants based on concentrating power technologies are used to harness the solar radiation effectively. Among the solar power technologies, line-focusing concentrating systems such as linear Fresnel reflector (LFR) and parabolic trough collector (PTC) are simple in design and cost-effective with high dispatchability. The energy and exergy efficiencies of various components of the solar field and power block are determined. The overall energy and exergy efficiencies of 50-MW e LFR power plants are estimated as 12.17 and 17.21% and 23.16 and 32.76%, respectively, for the PTC power plant. The results show that a maximum energy loss occurs in the solar field and power block for LFR and PTC power plants respectively, and a maximum exergy loss occurs in the solar field for both power plants. The analyses of solar power plants have been carried out to estimate the environmental benefits; the results showed that a 1-MW e stand-alone line-focusing concentrating solar power plant can save 1813 tonnes of CO 2 , 12.52 tonnes of SO 2 , 6.23 tonnes of NO x and 0.98 tonnes of particulate matter annually compared with that of an Indian subcritical coal power plant. The levelized electricity cost for the LFR- and PTC-based stand-alone solar power plant varies from INR 14.77 to INR 10.19 and INR 14.7 to INR 8.48 for the plant capacities that vary from 1 to 50 MW e .

Description: The photosynthetic bacterium Rhodobacter capsulatus produces hydrogen under nitrogen-limited, anaerobic, photosynthetic conditions. The present study examined whether R. capsulatus can produce hydrogen under microaerobic conditions in the dark with limiting amounts of O 2 and fixed nitrogen. The relationship between hydrogen production, different O 2 concentrations and carbon sources as well as two different N sources, glutamate and ammonium, were studied in batch culture using a Hup strain of R. capsulatus . The effect of different O 2 concentrations, ranging from 0.5 to 20%, on hydrogen production was examined in dark batch cultures of R. capsulatus grown on RCV medium. Different carbon sources, e.g. glucose, succinate, lactate, acetate and malate, were used at various concentrations (20–40 mM). Similarly, different concentrations of glutamate and ammonium (2–9 mM) were examined for optimum microaerobic dark hydrogen production. Maximum hydrogen production was observed at an O 2 concentration of 4–8%. There was a highly positive correlation between O 2 and growth ( r 2 = 0.67), whereas O 2 concentration and hydrogen productivity were negatively correlated ( r 2 = –0.3). Succinate (25 mM) together with glutamate (3.5 mM) gave the highest specific hydrogen productivity [5.61 μmol hydrogen/(mg cell dry weight/ml)]. The maximum average hydrogen yield was 0.6 mol hydrogen/mol malate followed by 0.41 mol hydrogen/mol lactate, 0.36 mol hydrogen/mol succinate, whereas minimum amounts of hydrogen were produced from glucose and acetate (0.16 mol hydrogen/mol and 0.07 mol hydrogen/mol, respectively). The implications for developing a system capable of improved hydrogen production are discussed.

Description: Substantial growth in refrigeration and air-conditioning industry has made a significant impact on net energy consumption. Condenser pressure is one of the critical parameters in the energy-efficient operation of refrigeration and air-conditioning systems. A novel system is developed to use the condensate, available at the cooling coil, for condenser cooling of a window air-conditioner unit by employing evaporative cooling. Performance testing of the system has shown 13% savings in energy and up to 18% enhancement in coefficient of performance. The maximum benefit of the evaporative cooling cycle over the basic cycle was found to be in the region of moderate climatic conditions.

Description: The consumption of natural gas as a primary energy source in Italy has increased during recent years, mainly due to more widespread use of modern natural gas-fired combined cycle power plants. It is generally accepted that such an increased use of natural gas is beneficial, particularly in summer, due to the ‘take-or-pay’ contracts that often regulate energy supply. Conversely, the use of electrical energy should be decreased, in order to limit the ‘peak demand’ problem that has become prevalent in Italy. Therefore, besides electrically driven heat pumps (EHPs) that achieve good efficiencies, it is interesting to also consider the option of combustion engine-driven GEHPs for space heating purposes. In the latter type of HPs, losses attributed to the production and transport of electricity are eliminated and, in addition, there is the possibility to re-use the heat from the combustion engine. This article presents an assessment of the annual economic and energy profiles of electric and internal combustion engine HPs for space heating purposes. Due to the dependency of the performance of such technology on the source and sink (heating circuit) temperature levels, a comparison is performed of air-to-water HP systems (the most widely used) in two cases of maximum flow temperatures. The calculations show that natural gas-driven HPs can achieve approximately the same efficiency as electrically driven HPs that are powered with electricity from modern natural gas-fired combined cycle power plants. Within this study, the efficiencies of such systems are also compared with those that utilize conventional boiler technologies.

Description: The Intergovernmental Panel on Climate Change has estimated that ill-effects of carbon emissions will grow to 5% by 2050. Although ICAO had initially endorsed the idea of the emissions trading system to meet CO 2 emission reduction objectives, prospects for a comprehensive global agreement appear to be distant, and a multi-faceted approach is required with a strong commitment from all stakeholders. Other options could be the usage of carbon neutral fuels, coming from biomass, algae and most recently the usage of CO 2 in the air and water in the atmosphere, and then the Fischer Tropsche process to combine the H 2 and CO 2 together to produce oil (Louise and Paul. Aviation and climate change. House of Commons Library, 2008 ).

Description: A coupled system of two liquid desiccant columns—one dehumidifying the air and the other regenerating the solution—has been investigated for very low solution to air flow ratios ( S / A ) in the range of 0.2–1.6%. The present study explores the feasibility of integrating the columns with the conventional room air conditioner (AC) to enhance the dehumidification capacity of the hybrid AC system. The air inlet conditions to dehumidifying column are assumed typical of supply air from a room AC at 8–16°C dry bulb temperature (DBT) and 75–95% relative humidity. Similarly, inlet air to regenerating column is assumed at 40–60°C DBT and 15–20 g/kg specific humidity, which are typical of the condenser exit air. It is observed that the moisture transfer from supply to condenser air takes place at the rate of 0.28–0.6 g/s for a 0.8 TR AC unit. This indeed enhances the dehumidification of the supply air considerably. Moreover, the supply air gets sensibly heated following the isenthalpic dehumidification process, which enables the hybrid system to maintain low humidity in the conditioned space.

Description: Biomass energy is growing worldwide as generators continue their search for sustainable energy sources. This project focuses on the storage of biomass fuels, investigating degradation. Four different fuels were stored in air-tight buckets for 9 months to promote artificial degradation and provide an initial benchmark in a long-term project investigating the impact of different storage scenarios on a range of fuels. At regular intervals, samples were taken out of buckets for analysis including stereo zoom microscopy and thermogravimetric analysis. Fungal analysis was carried out on two degraded fuels.

Description: Energy generation by fossil fuel contributes to carbon emission to the atmosphere which is a major threat to global environment. Measuring energy consumption in building, accounting related carbon emission and selecting low embodied energy (EE) material by performing life-cycle analysis gives a clear idea about EE of the building and highlights mitigation potential. The review presented in the paper identifies the role of buildings in global carbon emission and solutions to reduce it with appropriate low EE material. This review helps in developing an insight for building's role in carbon emission and ways to develop carbon minus buildings.

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: This paper describes the setting up and first call results of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) established by the European Union (Council regulation No 521/2008 of 30 May 2008 setting up the Fuel Cells and Hydrogen Joint Undertaking, Official Journal of the European Union , 2008;L153:1–20). Funding for low carbon energy research on hydrogen and fuel cells in Europe has been gradually increasing since 1990 but has gained significant visibility with the establishment of the Joint Undertaking which is an innovative industry-led scheme, covering the full innovation cycle, from research to market entry. Significant projects led by industry are now running and hydrogen energy has great practical potential in five application areas; transport and refuelling infrastructure; hydrogen production and storage; stationary power production and combined heat and power; early markets; and cross-cutting areas such as codes and standards, regulation, life-cycle assessment, training.

Description: This research is aimed at investigating the aggregation behaviour of catalyst nanoparticles in proton exchange membrane fuel cells (PEMFCs). Electrocatalyst nanoparticles are prepared using various surfactants which are known to prevent aggregation. Well-dispersed nanoparticles are thought to have a higher available surface area, hence exhibiting higher catalytic activity than aggregated nanoparticles. Platinum nanoparticles have been successfully prepared in aqueous dispersion using tetradecyltrimethylammonium bromide (C 14 TAB), cetyltrimethylammonium bromide (C 16 TAB) and nonylphenolethoxylate (NP9). The aggregation behaviour of the particles was studied using transmission electron microscopy, Nanosight (Carr B, Hole P, Malloy A. Sizing of nanoparticles by visualizing and simultaneously tracking the Brownian motion of nanoparticles separately within a suspension. In: Eighth International Congress on Optical Particle Characterisation , Karl-Franzens University Graz, 2007) and dynamic light scattering. Electrochemistry results for the oxygen reduction reaction (ORR) on the platinum disc in the absence and in the presence of surfactants show that the surfactants have a marked effect on the reaction. The movement of the onset potential to lower voltages suggests the surfactant is poisoning the catalytic sites on the electrode. This shows that the surfactant molecule selection is vital to obtaining effective fuel cell catalyst.

Description: The function of a cycling test is the investigation of fuel cell stability and degradation behaviour under non-steady operating conditions. Cell quality becomes increasingly likely to degenerate at greater numbers of cycles. This work seeks to comprehensively test the durability of three tubes (tubes 1–3) of the integrated-planar solid oxide fuel cell (IP-SOFC) (Rolls Royce Fuel Cell Systems Ltd). The three IP-SOFC tubes were tested at a constant current of 1 A at 900°C for more than 1200h for tubes 1 and 3, and more than 4940h for tube 2. The fuel utilization was 13.94%, and the average voltage degradation rate measured was 1.3 and 1.5% per 1000h for tubes 2 and 3, respectively. After 1200h work, tube 1 failed because the air supply was cut off from the test station due to compressor overheating. Subsequently, the station closed all gas supply for safety, but the furnace continued to work at a temperature of 900°C for 16h. The tube showed clear signs of damage leading to complete failure.

Description: A balance of plant (BOP) system for a 9.5-kWe Nedstack P9.5-75 low-temperature proton exchange membrane fuel cell (FC) stack was tested up to a power of 2 kWe. The system has been designed to act as a range extender for a series hybrid electric vehicle driven under urban duty cycles. Vehicle simulations have estimated that an average gross power requirement of 4 kWe is needed from the FC, whilst simulations of the FC stack and BOP components have allowed for characterisation of transient behaviour and performance degradation.

Description: Local air quality was one of the main stimulants for low carbon vehicle development during the 1990s. Issues of national fuel security and global air quality (climate change) have added pressure for their development, stimulating schemes to facilitate their deployment in the UK. In this case study, Coventry City Council aimed to adopt an in-house fleet of electric and hybrid-electric vehicles to replace business mileage paid for in employee's private vehicles. This study made comparisons between the proposed vehicle technologies, in terms of costs and air quality, over projected scenarios of typical use. The study found that under 2009 conditions, the electric and hybrid fleet could not compete on cost with the current business model because of untested assumptions, but certain emissions were significantly reduced 〉50%. Climate change gas emissions were most drastically reduced where electric vehicles were adopted because the electricity supply was generated by renewable energy sources. The study identified the key cost barriers and benefits to adoption of low-emission vehicles in current conditions in the Coventry fleet. Low-emission vehicles achieved significant air pollution-associated health cost and atmospheric emission reductions per vehicle, and widespread adoption in cities could deliver significant change.

Description: Hydrogen and fuel cells for low-carbon energy have been considered in a road map for the UK, based on the existing predictions from Europe and the USA. Several key areas need to be addressed including renewable sources of fuel, buildings as power generators, hydrogen as a major energy vector, interconnection of dispersed generators/sinks and plug-in vehicles.

Description: Fossil fuel is the major source of energy for all forms of motor vehicle, with gasoline and diesel fuels dominating our personal transport. Although biofuels have been used to inject some renewable energy into the transport system, imports of oil and gas to Europe, the USA and Japan continue to rise. A move to reduce energy consumption and carbon emissions by driving more efficient vehicles is therefore necessary. This paper considers a shift to reduced friction hydrogen electric vehicles that give three major benefits: (i) sourcing hydrogen from low carbon sources like wind, biomass, nuclear and solar; (ii) using an electric drivetrain to minimize energy conversion to heat; and (iii) reducing resistances to motion to give lower energy requirements for traction. This energy dissipation due to friction proves to be a complex mixture of tyre losses, brake adhesion, wind resistance, fuel conversion inefficiency, motor resistance, drivetrain losses, auxiliary power consumption and so on. By considering the addition of many loss terms, it is shown that the energy dissipation in fuel cell-powered vehicles resolves into a linear function of vehicle weight.

Description: Hydrogen is considered to be an ideal energy carrier for low-carbon vehicles in the near future. It can be produced from water by using a variety of energy sources, such as solar, wind and nuclear, and it can be converted into useful energy efficiently and without detrimental environmental effects. The only by-product is water or water vapour in fuel cell vehicles, but small amounts of NO x are produced in combustion systems. Hydrogen can be used in any application in which fossil fuels are being used today, especially cars, buses and trucks. This paper considers how hydrogen can be combined with two other technologies; online vehicle monitoring and computer maps to give significant reduction in carbon emissions from combustion engines, especially on trucks.

Description: Platinum (Pt)-based nanowires can give excellent performance as electrochemical catalysts in low-temperature proton exchange fuel cells (PEFCs). Several preparation methods have been developed for this kind of application. In this paper, we review the development history of Pt-based nanowires for low-temperature fuel cells, focusing on the preparation method from the early template technique for the polycrystalline nanowires to the simple wet chemical approaches for preparing single crystal ones today. The limitations and future developments are also discussed.

Description: This investigation analyzes the thermal efficiency and pollutant emissions of a pressurized submerged combustion evaporator (PSCE). Experimental results show that our novel PSCE design can reduce NO x emissions to 12 mg/kg with increased submergence depth and CO emissions to 5.56 mg/kg when using an excess air coefficient of 〈1. As the excess air coefficient increases from 0.872 to 1.582, NO x emissions increase from 9.18 to 20.16 mg/kg, while CO emissions drop to zero. Therefore, it is the excess air coefficient, rather than the submergence depth, that plays a key role in controlling pollutant emissions. Water evaporation using this apparatus has a gross thermal efficiency of 95.2%.

Description: Shenzhen is a typical city of southern China. The current situation of natural gas utilization in Shenzhen is introduced. The experience of world energy consumption, especially the development trends of natural gas is reviewed. According to the characteristics of the economic development trends and the energy utilization planning in Shenzhen, the development prospect of natural gas utilization in Shenzhen is comprehensively analyzed. After the analysis, it is pointed out that natural gas will be a vital new source of energy utilization in Shenzhen. In the meanwhile, the problems and solution of interchangeability, price and alternate energy source in the natural gas development trend in Shenzhen are discussed. The results of the current study can be used as guidelines for the natural gas utilization and CO 2 emission reduction in other cities of southern China.

Description: Biodiesel production is gaining more and more relevance due to its environmental advantages and because of the world situation of petroleum: decreases of reserves, augmentation of prices etc. Biodiesel is produced by transesterification of triglycerides; however, it can also be generated by the esterification of fatty acid, normally considered as an impurity. The evolution of the reaction when using oleic acid (diluted in triglycerides) and ethanol, in the presence of a heterogeneous catalyst, has been studied. Kinetics expression for the esterification reaction as well as for the esterification and transesterification taking place simultaneously have been developed and fit with the experimental data. It is shown that, when both reactions are being taking into account, the kinetics fits the experimental data better since it does consider the interaction between all the compounds involved. The kinetics expression obtained represented satisfactorily the experimental information for several operations conditions.

Description: In this work, the esterification of oleic acid (OA) with methanol (MOH) using layered heterogeneous catalysts under various reaction conditions to produce biodiesel was studied. The zinc hydroxy nitrate salt Zn 5 (OH) 8 (NO 3 ) 2 · 2H 2 O (abbreviated Zn-N) and zinc hydroxy acetate Zn 5 (OH) 8 (CH 3 COO) 2 · 4H 2 O (abbreviated Zn-A), which have a layered structure, were synthesized (chemical precipitation) and characterized. Tests for the selection of reaction conditions that maximize the yield to methyl esters were performed. The variables considered were temperature, OA:MOH molar ratio and catalyst loading, selecting the study intervals within the range of feasible operating conditions for the catalysts. The layered solid Zn-A was seen to be more active than Zn-N for the esterification of OA. When working at 140°C, 1:30 OA:MOH molar ratio and catalyst loading of 3% w/w, conversions of 87.0 and 73.4% were obtained for Zn-A and Zn-N, respectively.

Description: Presently, India is almost dependent on coal-based energy, which leads to the generation of a considerable amount of CO 2 . In the context of climate change, solar energy is accepted as an important alternative source of energy as it is green energy. But the single crystal silicon cells, which are the starting material for solar energy, are produced in exchange of greenhouse gas, the carbon dioxide. Present article highlights an estimation of solar energy production and carbon credit (CC) earning by the photovoltaic cells of mono-crystalline silicon in a definite module, largely used in West Bengal, India. In addition, the quantity of silicon required for the preparation of this module as well as its equivalent amount of carbon dioxide generation during the extraction from quartzite sand by the Czocharlski' technique has been calculated. This analysis is based on the experimental and theoretical performance of the system. The study reveals that, on considering average light intensity (4.5 kWh) for 10h/day, the power output of this solar module is 0.60 kWh/m 2 /day. CC earned is computed as 0.33 tonnes/MWh/year, under West Bengal climatic condition as per the norms of the Kyoto protocol. For obtaining 11.86 kg of silicon, which is the raw material of soar cell used in this study, the amount of CO 2 production is calculated as 8.70 kg/MWh/year. Considering 35 kg CO 2 /MWh as reference, this amount of CO 2 production corresponds to 25% of the total carbon footprint.

Description: In this study, analysis studies of the first and second law of thermodynamics are carried out for vapor compressed refrigeration systems using an alternative refrigerant HFO-1234yf to HFC-134a. No important differences between cycle efficiencies were observed for both refrigerants. However, the exergy destruction rate of the compressor obtained with HFO-1234yf is lower than that calculated for R-134a. According to the exergy and energy analysis results obtained with this study, it can be evaluated that HFO-1234yf is a good alternative to R-134a. If the safety requirements (flammability problem of the refrigerant) have been satisfied refrigeration systems charged with HFO-1234yf, this alternative refrigerant can be commonly used in the systems.

Description: Water is one of the earth's most abundant resources, covering about three-quarters of the planet's surface. Yet, there is an acute shortage of potable water in many countries, especially in Africa and the Middle East region. The reason for this apparent contradiction is, of course, that ~97.5% of the earth's water is salt water in the oceans and only 2.5% is fresh water in ground water, lakes and rivers and this supplies most human and animal needs. Tackling the water scarcity problem must involve better and more economic ways of desalinating seawater. This article presents a comprehensive review of water desalination systems, whether operated by conventional energy or renewable energy, to convert saline water into fresh water. These systems comprise the thermal phase change and membrane processes, in addition to some alternative processes. Thermal processes include the multistage flash, multiple effects boiling and vapour compression, cogeneration and solar distillation, while the membrane processes include reverse osmosis, electrodialysis and membrane distillation. It also covers the integration into desalination systems of potential renewable energy resources, including solar energy, wind and geothermal energy. Such systems are increasingly attractive in the Middle East and Africa, areas suffering from shortages of fresh water but where solar energy is plentiful and where operational and maintenance costs are low. The advantages and disadvantages, including the economic and environmental aspects, of these desalination systems are presented.

Description: Proton exchange membrane fuel cells are widely employed in micro-combined heat and power cogeneration (micro-CHP) systems and the feed to them should be essentially free of CO. CO preferential oxidation is an effective method for deeply removal of the CO content in synthesis gas. A series of Pt/-Al 2 O 3 catalysts are made and tested for their CO cleaning capabilities. The catalyst is prepared from chloroplatinic acid and -Al 2 O 3 powder by normal or ultrasonic impregnation. Catalyst performance is investigated in a micro-reactor system. Effects of Pt loading, ultrasonic processing, CO space velocity, oxygen to CO ratio and reaction temperature on catalyst performance are studied. A CO preferential reactor for a kilowatt-scale CHP system is designed and tested. A special catalyst loading pattern is tried to maintain a uniform bed temperature distribution and high CO conversion. A CO concentration of 〈10 ppm is achieved when the CO concentration in the gas feed is 0.45%.

Description: In this article, the performances of a walk-in air cooler working with R22 and its substitute R422D are experimentally studied. To define a full comparison on the performance characteristics of R22 and R422D, both an energetic and an exergetic analyses are proposed. The experimental investigation was carried out considering four levels of refrigeration capacity: 920, 1340, 1925 and 2250 W. All tests were run at steady-state conditions and by keeping the value of the external air temperature equal to 22°C. The experimental analysis allowed the determination of the COP, the exergetic efficiency, the exergy flow destroyed in each component and other variables characterizing the working of the plant. The results demonstrated that COP of R422D is, on average, 20% lower than that of R22. Furthermore, for plant whose condenser is air cooled, R422D could lead to increase the fan speed or to adopt bigger blowers.

Description: According to the constructal area–point heat conduction model, the thermal current in the high-conductive path increases only at conjunction points. If the optimum number of the lower order constructs which formed higher order constructs is finite, the number of the conjunction points is finite and the thermal current in the high-conductive path increases discretely. The cross-section of the high-conductive path should be adapted to the change of the thermal current through it. The area–point heat conduction problem is re-optimized based on entransy dissipation rate minimization using a discrete variable cross-section conducting path. The optimization process confirms that the mean temperature difference will decrease by resembling constructs which is expected by the constructal theory. Constructing the next assemble by a four optimization unit and making the high-conductive path cross-section scale by 2:1 will decrease the mean temperature difference regularly at an interval of two assembly levels, and the mean temperature difference will approach a constant. Optimization results show that the minimum mean temperature difference of the ninth assembly level decreases further by 2.84% compared with the optimization result without the premise of an optimized last-order construct.

Description: Taking into account the heat resistance losses between the heat reservoirs and the working fluid, irreversible compression and expansion losses in the compressors and the turbine, pressure drop losses in the piping and finite thermal capacity rate properties of the heat reservoirs, a real, intercooled, regenerated gas-turbine cogeneration plant model is established using finite-time thermodynamics. The finite-time exergoeconomic performance of the plant is studied by taking the dimensionless profit rate as the optimization objective. Analytical formulae about the dimensionless profit rate and exergy efficiency are derived. By numerical examples, the two cases with fixed and variable total pressure ratios are discussed, and meanwhile the effects of the cycle parameters on the performance of the plant are analyzed. The relationship of the dimensionless profit rate versus exergy efficiency is investigated, and the characteristic curve is found to be loop shaped. Finally, it is found that there exists an optimal consumer temperature that leads to a double-maximum dimensionless profit rate.

Description: In this study, an experimental investigation of temperature distribution and efficiencies in conventional solar pond (SP) and integrated SP (ISP) systems is presented. Several temperature-measuring sensors connected to a data acquisition system are used to measure the temperature changes with respect to time and position. In addition, the monthly stored energies of SP and ISP are determined. The maximum and the minimum energy efficiencies of the SP and ISP are observed for the months of August as 28.41 and 33.55% and January as 8.28 and 9.48%, respectively. These then confirm that the SP storage efficiency can be increased by integrating the system with solar collectors.

Description: This paper describes the outcomes of a research project that investigates sustainable heating and cooling solutions for retail applications using a carbon dioxide (CO 2 ) natural refrigerant (R744) for food refrigeration. The paper presents the findings from an applied research study on a booster CO 2 (R744) system with high and medium temperature heat recovery. The paper includes a description of the conceptual design and a computer model along with its validation based on some experimental results. The energy consumption and carbon emission reduction are investigated using this novel system based on an existing supermarket as a case study.

Description: Homotopy perturbation method is a novel approach that provides an approximate analytical solution to differential equations in the form of an infinite power series. In this work, homotopy perturbation method has been used to evaluate temperature distribution, efficiency and effectiveness of straight fins exposed to convection. The fin efficiency and the fin effectiveness have been obtained as a function of thermogeometric fin parameter. The results have revealed that the homotopy perturbation method is a very effective and practical approach for a rapid assessment of physical systems. The resulting correlation equations can assist thermal design engineers for designing of straight fins with both constant and temperature-dependent thermal conductivity.

Description: A recent spurt in the universal interest to study alternatives to the conventional DX refrigeration systems and use of natural refrigerants as secondary fluids has been visible. This investigation presents a comparative analysis between carbon dioxide and other working fluids for use in forced circulation-type secondary loops suitable for various refrigeration and air conditioning applications. The comparison is made on the basis of equal heat transfer rate, frictional pressure drop per unit length, temperature drop/rise of secondary fluid and mean temperature difference between the secondary fluid and heat exchanger tube wall. Employing friction factor and heat transfer correlations, equations are obtained for diameter ratio, area ratio, mass ratio and pumping power ratio. Results show that employing carbon dioxide in place of other conventional secondary fluids except water leads to compact and lightweight heat exchangers, despite the high-pressure operation of carbon dioxide-based loops. The pumping power required is much smaller as well in case of carbon dioxide compared with all other fluids for the wide range of operating temperatures. Though results are presented here for the case of cooling only, calculations indicate similar trends for the heating configuration as well. Carbon dioxide appears to be an excellent secondary fluid for a wide range of refrigeration and air conditioning applications and it could turn out to be a disruptive technology for such applications in view of its benign environmental footprint.

Description: The heat pump market in the UK has grown rapidly over the last few years. Performance analyses of vertical ground-loop heat exchanger configurations have been widely carried out using both numerical modelling and experiments. However, research findings and design recommendations on horizontal slinky-loop and vertical slinky-loop heat exchangers are far fewer compared with those for vertical ground-loop heat exchanger configurations, especially where the long-term operation of the systems is concerned. The paper presents the results obtained from a numerical simulation for the horizontal slinky-loop and vertical slinky-loop heat exchangers of a ground-source heat pump system. A three-dimensional numerical heat transfer model was developed to study the thermal performance of various heat exchanger configurations. The influence of the loop pitch (loop spacing) and the depth of a vertical slinky-loop installation were investigated and the thermal performance and excavation work required for the horizontal and vertical slinky-loop heat exchangers were compared. The influence of the installation depth for vertical slinky-loop configurations was also investigated. The results of this study show that the influence of the installation depth of the vertical slinky-loop heat exchanger on the thermal performance of the system is small. The maximum difference in the thermal performance between the vertical and horizontal slinky-loop heat exchangers with the same loop diameter and loop pitch is less than 5%.

Description: This article investigates the yearly operation of a building-integrated micro-cogeneration system through transient simulations; both energy and economic performance of the proposed system are analyzed and compared with those of a conventional system based on separate energy production in order to assess the potential savings. The energy comparison is carried out in terms of primary energy with respect to the specific Italian electricity mix; the economic analysis is performed by considering both the operating and capital costs, with the energy unit costs as well as the incentives for supporting the cogeneration technology evaluated according to the Italian scenario.

Description: An atrium is a great glassed volume on a building that allows the light to enter within it. Its border location between indoor and outdoor implies that the environmental conditions like solar radiation, ventilation and heat energy appear intensified, turning them into spaces with a great environmental potential. However, in Santiago, these spaces have been designed imitating the aesthetic of buildings suited for colder climates. This has resulted in the fact that atrium buildings are often known by their low comfort standards and excessive cooling demands. The aim of this article is to answer in which way some design considerations on atrium buildings can maximize their energy saving potential in the Mediterranean climate of Santiago Chile. This is carried out with software Tas, which allows us to simulate the effect on thermal demand over a theoretical atrium building when changing three glazing types, three ventilation regimes and three solar protections forms; resulting in 27 iterations that reveal the more environmentally efficient combinations.

Description: Compared with the traditional refrigerants, a solar ejector cooling system using R236fa was developed. Based on the established computation model, the operating performance of the ejector cooling system was simulated. Combined with the numerical computation, an experimental study on the system using R236fa, R141b and R123 was carried out. The experimental conditions were evaporator temperature (5–10°C), condenser temperature (30–36°C) and generator temperature (82–94°C). It was found that with refrigerant R236fa the optimum Coefficient of Performance (COP) (=0.413) of the ejector cooling system and the optimum overall COP (=0.243) of the solar ejector cooling system could be obtained.

Description: Finite-time thermodynamics is applied to establish a real intercooled regenerated gas turbine cogeneration plant model in Part 1 of this article and the profit rate performance of the plant is researched using finite-time exergoeconomic analysis. In this part, the optimization of finite-time exergoeconomic performance of the plant is performed by optimizing the intercooling pressure ratio and the heat conductance distributions among the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator together, and it is found that the optimal heat conductance distribution of the regenerator is zero. When the heat conductance distribution of the regenerator is fixed, the results show that there exists an optimal intercooling pressure ratio and a group of optimal heat conductance distributions among the other four heat exchangers, which leads to a maximum dimensionless profit rate for the fixed total pressure ratio. When the total pressure ratio is variable, a double-maximum dimensionless profit rate is obtained. The characteristics of the double-maximum dimensionless profit rate, the corresponding exergetic efficiency, heat conductance distributions and total pressure ratio versus some main design parameters are analyzed in detail. Finally, it is found that the dimensionless profit rate has a thrice-maximum value with respect to the thermal capacitance rate matching between the working fluid and the heat reservoir.

Description: An analysis of the effects that groundwater flow has on the thermal regime created by a ground source energy system is presented. The change in the development of the sub-surface thermal regime caused by a groundwater flow across a site, relative to a scenario where groundwater flow does not exist, is examined. Analysis is performed using bespoke finite-element formulations of both single- and multi-borehole systems. The results of this work show that even a modest groundwater flow across a site can lead to a significant change in the development of the sub-surface thermal regime.

Description: The main purpose of this paper is to present an evaluation of the in-use energy performance of the Richard Feilden House student accommodation at Queen Mary University, London, UK. The building was completed and occupied in October 2007 and the study was conducted over a 2-year period (January 2008–December 2009). Analysis of the energy audit carried out as part of the study is presented in this paper. The findings suggest that the energy performance of the Richard Feilden House student accommodation is in accordance with its design intent and better than the Good Practice Benchmarks. High levels of insulation, thermal mass, ventilation heat recovery, decentralised electric heating, a greater reliance on internal heat gains for space heating and a proactive building management approach have contributed to this success. However, strategies similar to those adopted by the Passivhaus Standards will be required if future targets of low-carbon buildings are to be met. Currently, there is limited knowledge on the in-use energy performance of student housing in the UK, and while the findings from this study can be helpful for benchmark comparison, more such studies of this building types in the UK are required.

Description: A re-analysis of the ‘tree-shaped network’ constructal method for triangular-shaped electronics is presented. The high effective conduction channel distribution has been re-optimized by using a triangular elemental area, without the premise that the new-order assembly construct must be assembled by the optimized last-order construct. A more optimal construct with triangular elemental area is obtained, and when the thermal conductivity and the proportion of the two heat conduction materials are constants, the limit of the minimum heat resistance with the triangular elemental area is derived. All these conclusions can be used as a guide for engineering applications.

Description: Rooftop photovoltaic (PV) systems can be readily deployed on industrial halls with a relatively large rooftop area. The feed-in tariff above the base price of electricity is offered in many countries to subsidize the high initial investment of PV systems. To fully capitalize the benefit of the feed-in tariff, the investigation of the actual performance of PV systems under case-specific conditions is very important. With building energy simulation, this paper explores the cost–benefit of implementing PV systems of different capacities for a few different cases of industrial halls. The impact of various economic parameters is also investigated.

Description: Recently, the Palestinian energy authority has approved a renewable energy policy to resolve the electricity problem caused by the Palestinian-Israeli energy dispute. Based on this, clear technical aspects in regards to renewable energy systems must enforced. In this research, a renewable energy system consisting of a PV and a wind energy source is proposed to be connected to Nablus city electricity grid. The proposed system is optimally designed taking into consideration maximum system productivity and inverter size. Two evaluating factors are used to optimally choose the configuration of the proposed system namely final yield factor (FY) and capacity factor (CF). As for the inverter, a liner programming optimization is performed to find out the optimum inverter sizing ratio (the rated power of the energy source to the rated power of the inverter). The results show that the use of PV energy sources is more feasible as compared to wind energy sources in Nablus. Therefore, a grid-connected system consisting of PV array only as an energy source is recommended. Moreover, the optimum sizing ratio of the inverter in the proposed system is 1.42.

Description: In the present work, a computational fluid dynamics analysis has been carried out for analysing heat transfer from a longitudinal fin with step change. For the aforementioned problem, heat is transferred by conduction through the fin along its length and dissipated from the fin surface via natural convection to the ambient and thermal radiation to the surrounding. For a given volume or mass, the total amount of heat dissipated from the fin surface, fin effectiveness and fin efficiency have been determined for two novel fin profiles and the results have been compared with that of conventional rectangular fin (CRF). Numerical calculations have been carried out for five different cases. It has been concluded that novel fin configurations dissipate more heat and produce higher fin efficiency than the CRF profile. The rectangular fin with single-step change has been found to be the most efficient fin profile in terms of maximum heat loss and fin efficiency. The optimum fin dissipated ~3.4% more heat and provided 2% higher efficiency than the CRF profile. Some recommendations have been made about the potential application areas of proposed fin configurations.

Description: In the present study, energetic and exergetic analyses of a transcritical nitrous oxide (N 2 O) heat pump cycle are carried out on the basis of the optimization of discharge pressure. A simulation code was developed to study cycle performances for the given design and operating parameters. This code was integrated with the thermodynamic property subroutine ‘N 2 OPROP’ to estimate the thermodynamic properties of N 2 O in subcritical and supercritical regions. Variation trends of optimal parameters for an N 2 O system are similar to those of a CO 2 system. However, the N 2 O cycle exhibits higher cooling COP, lower compressor pressure ratio and lower discharge pressure and temperature, and higher second-law efficiency than those of CO 2 -based systems. An N 2 O system is inferior in terms of volumetric cooling capacity compared with a transcritical CO 2 system. The maximum exergy loss is observed in the throttle valve (expansion valve) as in the case of a CO 2 transcritical system due to low critical temperature.

Description: Double-skin façades (DSF) are considered an innovative energy efficient technique that gained an increasing interest worldwide. The aim of this article is to perform a parametric study for the DSFs’ configuration in hot climatic conditions. The parameters under investigation are the ventilation rate, the shading requirements and the cavity dimensions. A newly erected building with surface area of 18 500 m 2 is considered as the basis for the parametric study. The building is monitored and simulated using Energy Plus. The parametric analysis showed that the ventilation rate in the DSFs’ configuration is of a major importance especially during the cooling season. The lack of adequate ventilation increases the cooling demands and deteriorates the DSF's effectiveness. Finally, the integration of shading in the overall construction, especially the external ones, results to 24% annual energy conservation.

Description: The power and efficiency of the open regenerative cycle of an externally fired micro gas turbine power plant without blade cooling with pressure drop irreversibilities are optimized based on the model established using thermodynamic optimization theory in Part 1 of this article by adjusting the mass flow rate (or the distribution of pressure losses along the flow path). It is shown that there are optimal air mass flow rates (or the distribution of pressure losses along the flow path) which maximize the net power output, and the maximum has an additional maximum with respect to the compressor pressure ratio. When the optimization is performed with the constraints of the fixed fuel flow and the plant size, the net power output and the thermal conversion efficiency of the cycle can be maximized again by properly allocating the fixed flow area among the compressor inlet and the power turbine outlet. The numerical examples show the effects of the design parameters on the power output and heat conversion efficiency and that both the power output and conversion efficiency increase with the increase in the effectiveness of the regenerator, which is different from the open cycle regenerator gas turbine power plant.

Description: Produced water is a complex mixture of organic and inorganic compounds and the largest volume of by-product generated during oil and gas recovery operations. The potential of oilfield produced water to be a source of fresh water for water-stressed oil-producing countries and the increasing environmental concerns in addition to stringent legislations on produced water discharge into the environment have made produced water management a significant part of the oil and gas business. This article reviews current technologies for the management of produced water, examines how electrochemical techniques may be used in these areas and compares the prospects for future development. It suggests that treatment technologies based on electrochemistry could be the future of produced water management, since produced water is a potential electrolyte because it has a relatively good conductivity. It also explains that by applying photoelectrochemistry, water electrolysis, fuel cell and electrodeposition, electrochemical engineering could achieve energy storage, production of clean water and recovery of valuable metals from produced water with minimal or no negative impact on the environment.