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Showing papers in "Renewable & Sustainable Energy Reviews in 2008"


Journal ArticleDOI
TL;DR: In this paper, the main characteristics of different electricity storage techniques and their field of application (permanent or portable, long- or short-term storage, maximum power required, etc.).
Abstract: Electricity generated from renewable sources, which has shown remarkable growth worldwide, can rarely provide immediate response to demand as these sources do not deliver a regular supply easily adjustable to consumption needs. Thus, the growth of this decentralized production means greater network load stability problems and requires energy storage, generally using lead batteries, as a potential solution. However, lead batteries cannot withstand high cycling rates, nor can they store large amounts of energy in a small volume. That is why other types of storage technologies are being developed and implemented. This has led to the emergence of storage as a crucial element in the management of energy from renewable sources, allowing energy to be released into the grid during peak hours when it is more valuable. The work described in this paper highlights the need to store energy in order to strengthen power networks and maintain load levels. There are various types of storage methods, some of which are already in use, while others are still in development. We have taken a look at the main characteristics of the different electricity storage techniques and their field of application (permanent or portable, long- or short-term storage, maximum power required, etc.). These characteristics will serve to make comparisons in order to determine the most appropriate technique for each type of application.

1,822 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the potential for such integrated systems in the stationary and portable power market in response to the critical need for a cleaner energy technology, which will also contribute to the amelioration of environmental conditions by replacing conventional fuels with renewable energies that produce no air pollution or greenhouse gases.
Abstract: Globally, buildings are responsible for approximately 40% of the total world annual energy consumption. Most of this energy is for the provision of lighting, heating, cooling, and air conditioning. Increasing awareness of the environmental impact of CO2 and NOx emissions and CFCs triggered a renewed interest in environmentally friendly cooling, and heating technologies. Under the 1997 Montreal Protocol, governments agreed to phase out chemicals used as refrigerants that have the potential to destroy stratospheric ozone. It was therefore considered desirable to reduce energy consumption and decrease the rate of depletion of world energy reserves and pollution of the environment. One way of reducing building energy consumption is to design building, which are more economical in their use of energy for heating, lighting, cooling, ventilation and hot water supply. Passive measures, particularly natural or hybrid ventilation rather than air-conditioning, can dramatically reduce primary energy consumption. However, exploitation of renewable energy in buildings and agricultural greenhouses can, also, significantly contribute towards reducing dependency on fossil fuels. Therefore, promoting innovative renewable applications and reinforcing the renewable energy market will contribute to preservation of the ecosystem by reducing emissions at local and global levels. This will also contribute to the amelioration of environmental conditions by replacing conventional fuels with renewable energies that produce no air pollution or greenhouse gases. The provision of good indoor environmental quality while achieving energy and cost-efficient operation of the heating, ventilating and air-conditioning (HVAC) plants in buildings represents a multi-variant problem. The comfort of building occupants is dependent on many environmental parameters including air speed, temperature, relative humidity and quality in addition to lighting and noise. The overall objective is to provide a high level of building performance (BP), which can be defined as indoor environmental quality (IEQ), energy efficiency (EE) and cost efficiency (CE). • Indoor environmental quality is the perceived condition of comfort that building occupants experience due to the physical and psychological conditions to which they are exposed by their surroundings. The main physical parameters affecting IEQ are air speed, temperature, relative humidity and quality. • Energy efficiency is related to the provision of the desired environmental conditions while consuming the minimal quantity of energy. • Cost efficiency is the financial expenditure on energy relative to the level of environmental comfort and productivity that the building occupants attained. The overall cost efficiency can be improved by improving the indoor environmental quality and the energy efficiency of a building. This article discusses the potential for such integrated systems in the stationary and portable power market in response to the critical need for a cleaner energy technology. Anticipated patterns of future energy use and consequent environmental impacts (acid precipitation, ozone depletion and the greenhouse effect or global warming) are comprehensively discussed in this paper. Throughout the theme several issues relating to renewable energies, environment and sustainable development are examined from both current and future perspectives.

1,578 citations


Journal ArticleDOI
TL;DR: In this article, the authors review past and future trends in sludge handling, focusing mainly at thermal processes (e.g. pyrolysis, wet oxidation, gasification) and the utilization of sewage sludge in cement manufacture as a co-fuel.
Abstract: The European Union has made progress in dealing with municipal wastewater in individual countries and as a corporate entity. However, it intends to make still further and substantial progress over the next 15 years. Currently, the most widely available options in the EU are the agriculture utilization, the waste disposal sites, the land reclamation and restoration, the incineration and other novel uses. The selection of an option on a local basis reflects local or national, cultural, historical, geographical, legal, political and economic circumstances. The degree of flexibility varies from country to country. In any case sludge treatment and disposal should always be considered as an integral part of treatment of wastewater. There is a wide range of other uses for sludge, which exploit its energy or chemical content, namely the thermal processes. The present paper sought to review past and future trends in sludge handling, focusing mainly at thermal processes (e.g. pyrolysis, wet oxidation, gasification) and the utilization of sewage sludge in cement manufacture as a co-fuel.

1,242 citations


Journal ArticleDOI
TL;DR: In this article, a review of pyrolysis has been presented, where various types of pyrotechnics have been discussed in detail including slow, fast, flash and catalytic processes.
Abstract: Demand for energy and its resources, is increasing every day due to the rapid outgrowth of population and urbanization. As the major conventional energy resources like coal, petroleum and natural gas are at the verge of getting extinct, biomass can be considered as one of the promising environment friendly renewable energy options. Different thermo-chemical conversion processes that include combustion, gasification, liquefaction, hydrogenation and pyrolysis, have been used to convert the biomass into various energy products. Although pyrolysis is still under developing stage but during current energy scenario, pyrolysis has received special attention as it can convert biomass directly into solid, liquid and gaseous products by thermal decomposition of biomass in absence of oxygen. In this review article, the focus has been made on pyrolysis while other conventional processes have been discussed in brief. For having better insight, various types of pyrolysis processes have been discussed in detail including slow, fast, flash and catalytic pyrolysis processes. Besides biomass resources and constituents, the composition and uses of pyrolysis products have been discussed in detail. This review article aim to focus on various operational parameters, viz. temperature and particle size of biomass and product yields using various types of biomasses.

1,061 citations


Journal ArticleDOI
TL;DR: In this article, a review of available latent heat thermal energy storage technologies is presented, including material, encapsulation, heat transfer, applications and new phase change material (PCM) technology innovation.
Abstract: Thermal energy storage has recently attracted increasing interest related to thermal applications such as space and water heating, waste heat utilization, cooling and air-conditioning. Energy storage is essential whenever there is a mismatch between the supply and consumption of energy. Use of phase change material (PCM) capsules assembled as a packed bed is one of the important methods that has been proposed to achieve the objective of high storage density with higher efficiency. A proper designing of the thermal energy storage systems using PCMs requires quantitative information about heat transfer and phase change processes in PCM. This paper reviews the development of available latent heat thermal energy storage technologies. The different aspects of storage such as material, encapsulation, heat transfer, applications and new PCM technology innovation have been carried out.

782 citations


Journal ArticleDOI
Arif Hepbasli1
TL;DR: In this article, a comprehensive review of the exergetic analysis and performance evaluation of a wide range of renewable energy resources (RERs) for the first time to the best of the author's knowledge is presented.
Abstract: Energy resources and their utilization intimately relate to sustainable development. In attaining sustainable development, increasing the energy efficiencies of processes utilizing sustainable energy resources plays an important role. The utilization of renewable energy offers a wide range of exceptional benefits. There is also a link between exergy and sustainable development. A sustainable energy system may be regarded as a cost-efficient, reliable, and environmentally friendly energy system that effectively utilizes local resources and networks. Exergy analysis has been widely used in the design, simulation and performance evaluation of energy systems. The present study comprehensively reviews exergetic analysis and performance evaluation of a wide range of renewable energy resources (RERs) for the first time to the best of the author's knowledge. In this regard, general relations (i.e., energy, exergy, entropy and exergy balance equations along with exergy efficiency, exergetic improvement potential rate and some thermodynamic parameters, such as fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor) used in the analysis are presented first. Next, exergetically analyzed and evaluated RERs include (a) solar energy systems; (a1) solar collector applications such as solar water heating systems, solar space heating and cooling, solar refrigeration, solar cookers, industrial process heat, solar desalination systems and solar thermal power plants), (a2) photovoltaics (PVs) and (a3) hybrid (PV/thermal) solar collectors, (b) wind energy systems, (c) geothermal energy systems, (c1) direct utilization (district heating, geothermal or ground-source heat pumps, greenhouses and drying) and (c2) indirect utilization (geothermal power plants), (d) biomass, (e) other renewable energy systems, and (f) country based RERs. Studies conducted on these RERs are then compared with the previously ones in tabulated forms, while the Grassmann (or exergy flow) diagrams, which are a very useful representation of exergy flows and losses, for some RERs are given. Finally, the conclusions are presented. It is expected that this comprehensive study will be very beneficial to everyone involved or interested in the exergetic design, simulation, analysis and performance assessment of RERs.

777 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe methodologies to model hybrid renewable energy systems (HRES) components, HRES designs and their evaluation and highlight the issues related to penetration of these energy systems in the present distribution network.
Abstract: Hybrid renewable energy systems (HRES) are becoming popular for remote area power generation applications due to advances in renewable energy technologies and subsequent rise in prices of petroleum products. Economic aspects of these technologies are sufficiently promising to include them in developing power generation capacity for developing countries. Research and development efforts in solar, wind, and other renewable energy technologies are required to continue for, improving their performance, establishing techniques for accurately predicting their output and reliably integrating them with other conventional generating sources. The paper describes methodologies to model HRES components, HRES designs and their evaluation. The trends in HRES design show that the hybrid PV/wind energy systems are becoming gaining popular. The issues related to penetration of these energy systems in the present distribution network are highlighted.

775 citations


Journal ArticleDOI
TL;DR: In this article, the authors reviewed the researches and studies on MG technology and the operation of MG and the MG in the market environment, and also described the MG's performance in the real world.
Abstract: The distributed energy resources (DER) comprise several technologies, such as diesel engines, micro turbines, fuel cells, photovoltaic, small wind turbines, etc. The coordinated operation and control of DER together with controllable loads and storage devices, such as flywheels, energy capacitors and batteries are central to the concept of MicroGrid (MG). MG can operate interconnected to the main distribution grid, or in an islanded mode. This paper reviews the researches and studies on MG technology. The operation of MG and the MG in the market environment are also described in the paper.

763 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the literatures pertaining to tar reduction or destruction methods during biomass gasification/pyrolysis and classified them into five main groups: mechanism methods, self-modification, thermal cracking, catalyst cracking and plasma methods.
Abstract: Biomass is an important primary energy source as well as renewable energy source. As the most promising biomass utilization method, gasification/pyrolysis produces not only useful fuel gases, char and chemicals, but also some byproducts like fly ash, NOx, SO2 and tar. Tar in the product gases will condense at low temperature, and lead to clogged or blockage in fuel lines, filters and engines. Moreover, too much tar in product gases will reduce the utilization efficiency of biomass. Therefore, the reduction or decomposition of tar in biomass derived fuel gases is one of the biggest obstacles in its utilization for power generation. In this paper, we review the literatures pertaining to tar reduction or destruction methods during biomass gasification/pyrolysis. On the basis of their characteristics, the current tar reduction or destruction methods can be broadly divided into five main groups: mechanism methods, self-modification, thermal cracking, catalyst cracking and plasma methods.

733 citations


Journal ArticleDOI
TL;DR: A detailed literature-based review of ground-source heat pump technology, concentrating on loops, ground systems, and looks more briefly at applications and costs and benefits is provided in this paper. But, despite potential environmental problems, geothermal heat pumps pose little if any serious environmental risk when best management practices are applied during the installation, operation, and decommissioning of these systems.
Abstract: Ground-source or geothermal heat pumps are a highly efficient, renewable energy technology for space heating and cooling. This technology relies on the fact that, at depth, the Earth has a relatively constant temperature, warmer than the air in winter and cooler than the air in summer. A geothermal heat pump can transfer heat stored in the Earth into a building during the winter, and transfer heat out of the building during the summer. Special geologic conditions, such as hot springs, are not needed for successful application of geothermal heat pumps. Ground-source heat pumps (GSHPs) are receiving increasing interest because of their potential to reduce primary energy consumption and thus reduce emissions of greenhouse gases. The technology is well established in North America and parts of Europe, but is at the demonstration stage in the UK. This article provides a detailed literature-based review of ground-source heat pump technology, concentrating on loops, ground systems, and looks more briefly at applications and costs and benefits. It concludes with the prospects for GSHP in the UK. It is concluded that, despite potential environmental problems, geothermal heat pumps pose little if any serious environmental risk when best management practices are applied during the installation, operation, and decommissioning of these systems.

661 citations


Journal ArticleDOI
TL;DR: This paper makes a brief review on 30 years of history of the wind power short-term prediction, since the first ideas and sketches to the actual state of the art on models and tools, giving emphasis to the most significant proposals and developments.
Abstract: This paper makes a brief review on 30 years of history of the wind power short-term prediction, since the first ideas and sketches on the theme to the actual state of the art on models and tools, giving emphasis to the most significant proposals and developments. The two principal lines of thought on short-term prediction (mathematical and physical) are indistinctly treated here and comparisons between models and tools are avoided, mainly because, on the one hand, a standard for a measure of performance is still not adopted and, on the other hand, it is very important that the data are exactly the same in order to compare two models (this fact makes it almost impossible to carry out a quantitative comparison between a huge number of models and methods). In place of a quantitative description, a qualitative approach is preferred for this review, remarking the contribution (and innovative aspect) of each model. On the basis of the review, some topics for future research are pointed out.

Journal ArticleDOI
TL;DR: In this paper, the authors present a concise and up-to-date picture of the present status of oil palm industry enhancing sustainable and renewable energy, and identify the prospects of Malaysian oil palm Industry towards utilization of palm oil as a source of renewable energy.
Abstract: Malaysia is currently the world's largest producer and exporter of palm oil. Malaysia produces about 47% of the world's supply of palm oil. Malaysia also accounts the highest percentage of global vegetable oils and fats trade in year 2005. Besides producing oils and fats, at present there is a continuous increasing interest concerning oil palm renewable energy. One of the major attentions is bio-diesel from palm oil. Bio-diesel implementation in Malaysia is important because of environmental protection and energy supply security reasons. This palm oil bio-diesel is biodegradable, non-toxic, and has significantly fewer emissions than petroleum-based diesel (petro-diesel) when burned. In addition to this oil, palm is also a well-known plant for its other sources of renewable energy, for example huge quantities of biomass by-products are developed to produce value added products such as methane gas, bio-plastic, organic acids, bio-compost, ply-wood, activated carbon, and animal feedstock. Even waste effluent; palm oil mill effluent (POME) has been converted to produce energy. Oil palm has created many opportunities and social benefits for the locals. In the above perspective, the objective of the present work is to give a concise and up-to-date picture of the present status of oil palm industry enhancing sustainable and renewable energy. This work also aims to identify the prospects of Malaysian oil palm industry towards utilization of oil palm as a source of renewable energy.

Journal ArticleDOI
TL;DR: An overview of this research is presented in this paper, both in terms of an historic overview of research projects and in the form of a thematic overview, addressing the different research issues for PVT.
Abstract: Over the last 30 years, a large amount of research on PV-Thermal (PVT) collectors has been carried out. An overview of this research is presented, both in terms of an historic overview of research projects and in the form of a thematic overview, addressing the different research issues for PVT.

Journal ArticleDOI
TL;DR: A wide variety of processes are available for hydrogen production from gaseous or liquid fuels They differ according to the nature of the primary fuel used (ammonia, methanol, ethanol), and to the chemical reactions involved (decomposition, steam reforming, partial oxidation, electrolysis, gasification) as discussed by the authors.
Abstract: A wide variety of processes are available for hydrogen production from gaseous or liquid fuels They differ according to the nature of the primary fuel used (ammonia, methanol, ethanol, gaseous or liquid hydrocarbons, water) and to the chemical reactions involved (decomposition, steam reforming, partial oxidation, electrolysis, gasification) As recent technology progress makes hydrogen a realistic long-term energy option with little or no pollution, developments of new methods for its production and improvement of conventional technology are important This paper analyzes the recent development of hydrogen production technologies followed by an overview of conventional and renewable energy sources and a discussion about enviro-economic aspects for hydrogen production methods The results show that although renewable energy resources cannot entirely satisfy the energy demand but electrolysis associated with solar energy, wind power, hydropower and biomass are available renewable sources for significant hydrogen production

Journal ArticleDOI
TL;DR: In this paper, three different wind turbines are considered; the horizontal axis wind turbine and two different concepts of vertical axis wind turbines; the Darrieus turbine and the H-rotor, and a case study is presented where three different turbines are compared to each other.
Abstract: Every year the number of installed wind power plants in the world increases. The horizontal axis wind turbine is the most common type of turbine but there exist other types. Here, three different wind turbines are considered; the horizontal axis wind turbine and two different concepts of vertical axis wind turbines; the Darrieus turbine and the H-rotor. This paper aims at making a comparative study of these three different wind turbines from the most important aspects including structural dynamics, control systems, maintenance, manufacturing and electrical equipment. A case study is presented where three different turbines are compared to each other. Furthermore, a study of blade areas for different turbines is presented. The vertical axis wind turbine appears to be advantageous to the horizontal axis wind turbine in several aspects.

Journal ArticleDOI
TL;DR: In this paper, the authors investigate fuel characteristics of biodiesel and its production in European Union and find that biodiesel fuel can be made from new or used vegetable oils and animal fats, which are non-toxic, biodegradable, renewable resources.
Abstract: The purpose of this work is to investigate fuel characteristics of biodiesel and its production in European Union. Biodiesel fuel can be made from new or used vegetable oils and animal fats, which are non-toxic, biodegradable, renewable resources. The vegetable oil fuels were not acceptable because they were more expensive than petroleum fuels. Biodiesel has become more attractive recently because of its environmental benefits. With recent increases in petroleum prices and uncertainties concerning petroleum availability, there is renewed interest in vegetable oil fuels for diesel engines. In Europe the most important biofuel is biodiesel. In the European Union biodiesel is the by far biggest biofuel and represents 82% of the biofuel production. Biodiesel production for 2003 in EU-25 was 1,504,000 tons.

Journal ArticleDOI
TL;DR: In this article, the problems associated with the selection of a phase change material (PCM) and the various methods used to contain them for space heating and cooling applications are discussed.
Abstract: Efficient and economical technology that can be used to store large amounts of heat or cold in a definite volume is the subject of research for a long time. Thermal storage plays an important role in building energy conservation, which is greatly assisted by the incorporation of latent heat storage (LHS) in building products. LHS in a phase change material (PCM) is very attractive because of its high storage density with small temperature swing. It has been demonstrated that for the development of a latent heat storage system (LHTS) in a building fabric, the choice of the PCM plays an important role in addition to heat transfer mechanism in the PCM. Thermal energy storage in the walls, ceiling and floor of buildings may be enhanced by encapsulating or embedding suitable PCMs within these surfaces. They can either capture solar energy directly or thermal energy through natural convection. Increasing the thermal storage capacity of a building can increase human comfort by decreasing the frequency of internal air temperature swings so that the indoor air temperature is closer to the desired temperature for a longer period of time. This paper aims to gather the information from the earlier works on the developments of PCM's incorporation in building, the problems associated with the selection of PCM and the various methods used to contain them for space heating and cooling applications.

Journal ArticleDOI
TL;DR: In this article, the main aerodynamic models that have been used for performance prediction and design of straight-bladed Darrieus-type VAWTs are presented. But, the authors did not discuss the performance of these models.
Abstract: Since ancient past humans have attempted to harness the wind energy through diversified means and vertical axis wind turbines (VAWTs) were one of the major equipment to achieve that. In this modern time, there is resurgence of interests regarding VAWTs as numerous universities and research institutions have carried out extensive research activities and developed numerous designs based on several aerodynamic computational models. These models are crucial for deducing optimum design parameters and also for predicting the performance before fabricating the VAWT. In this review, the authors have attempted to compile the main aerodynamic models that have been used for performance prediction and design of straight-bladed Darrieus-type VAWT. It has been found out that at present the most widely used models are the double-multiple streamtube model, Vortex model and the Cascade model. Each of these three models has its strengths and weaknesses which are discussed in this paper.

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the production and utilisation of liquids from the thermal processing of biomass and related materials to substitute for synthetic phenol and formaldehyde in phenol formaldehyde resins.
Abstract: This review covers the production and utilisation of liquids from the thermal processing of biomass and related materials to substitute for synthetic phenol and formaldehyde in phenol formaldehyde resins. These resins are primarily employed in the manufacture of wood panels such as plywood, MDF, particle-board and OSB. The most important thermal conversion methods for this purpose are fast pyrolysis and vacuum pyrolysis, pressure liquefaction and phenolysis. Many feedstocks have been tested for their suitability as sources of phenolics including hard and softwoods, bark and residual lignins. Resins have been prepared utilising either the whole liquid product, or a phenolics enriched fraction obtained after fractional condensation or further processing, such as solvent extraction. None of the phenolics production and fractionation techniques covered in this review are believed to allow substitution of 100% of the phenol content of the resin without impacting its effectiveness compared to commercial formulations based on petroleum derived phenol. This survey shows that considerable progress has been made towards reaching the goal of a price competitive renewable resin, but that further research is required to meet the twin challenges of low renewable resin cost and satisfactory quality requirements. Particular areas of concern are wood panel press times, variability of renewable resin properties, odour, lack of reactive sites compared to phenol and potential for increased emissions of volatile organic compounds.

Journal ArticleDOI
TL;DR: In this paper, the impact of four key institutional variables is examined and put into a scheme of a set of potential hypothesis about their inter-relationships, including planning systems; financial support mechanisms; landscape protection organizations and patterns of ownership of wind power.
Abstract: This paper aims to understand different outcomes of implementation of wind power deployment programmes. Geographical variables such as quantity of wind resources are in themselves insufficient to explain patterns of implementation of wind power. To enhance the review of the factors affecting wind power deployment we also made a systematic comparison of six country cases: Denmark, Spain, Germany, Scotland, the Netherlands, and England/Wales. The impact of four key institutional variables is examined and put into a scheme of a set of potential hypothesis about their inter-relationships. These are influenced by different national traditions: planning systems; financial support mechanisms; landscape protection organisations and patterns of ownership of wind power. (1) Planning systems, which favour wind power are essential, and in all cases national planning policies generally intend to support wind power development, but planning institutions show a wide variety with clear differences in implementation results. (2) Systems of financial support are also a sine qua non for development but they also vary in their effectiveness across country and time in the study. Robust and consistent support regimes in Denmark, Germany and Spain have speeded developments. (3) Landscape protection organisations vary in strength in a range between England/Wales (very strong and influential) to Spain (non-existent). Strong and effective opposition to wind developments is always primarily rooted in landscape values. (4) Local ownership patterns coincide with higher rates of wind power deployment than remote, corporate ownership. Local involvement recruits conditional support for projects and is related to traditions of energy activism. Such traditions are strongest in Denmark and Germany and weakest in Spain, England/Wales and Scotland.

Journal ArticleDOI
TL;DR: In this article, the main technical challenges associated with the integration of wind power into power systems are discussed, including effects of wind energy on the power system, the power systems operating cost, power quality, power imbalances, power system dynamics, and impacts on transmission planning.
Abstract: Wind power is going through a very rapid development. It is among the fastest growing power sources in the world, the technology is being developed rapidly and wind power is supplying significant shares of the energy in large regions. The integration of wind power in the power system is now an issue in order to optimize the utilization of the resource and to continue the high rate of installation of wind generating capacity, which is necessary so as to achieve the goals of sustainability and security of supply. This paper presents the main technical challenges that are associated with the integration of wind power into power systems. These challenges include effects of wind power on the power system, the power system operating cost, power quality, power imbalances, power system dynamics, and impacts on transmission planning. The main conclusion is that wind power's impacts on system operating costs are small at low wind penetrations (about 5% or less). At higher wind penetrations, the impact will be higher, although current results suggest the impact remains moderate with penetrations approaching 20%. In addition, the paper presents the technology and expectations of wind forecasting as well as cases where wind power curtailment could arise. Future research directions for a better understanding of the factors influencing the increased integration of wind power into power systems are also provided.

Journal ArticleDOI
TL;DR: A detailed review of the past efforts taken for the development of the Stirling cycle engine and techniques used for engine analysis can be found in this article, where it is seen that for successful operation of engine system with good efficiency a careful design of heat exchangers, proper selection of drive mechanism and engine configuration is essential.
Abstract: The performance of Stirling engines meets the demands of the efficient use of energy and environmental security and therefore they are the subject of much current interest. Hence, the development and investigation of Stirling engine have come to the attention of many scientific institutes and commercial companies. The Stirling engine is both practically and theoretically a significant device, its practical virtue is simple, reliable and safe which was recognized for a full century following its invention by Robert Stirling in 1816. The engine operates on a closed thermodynamic cycle, which is reversible. Today Stirling cycle-based systems are in commercial use as a heat pump, cryogenic refrigeration and air liquefaction. As a prime mover, Stirling cycles remain the subject of research and development efforts. The objective of this paper is to provide fundamental information and present a detailed review of the past efforts taken for the development of the Stirling cycle engine and techniques used for engine analysis. A number of attempts have been made by researches to build and improve the performance of Stirling engines. It is seen that for successful operation of engine system with good efficiency a careful design of heat exchangers, proper selection of drive mechanism and engine configuration is essential. The study indicates that a Stirling cycle engine working with relatively low temperature with air of helium as working fluid is potentially attractive engines of the future, especially solar-powered low-temperature differential Stirling engines with vertical, double acting, and gamma configuration.

Journal ArticleDOI
TL;DR: In this paper, the working principle of adsorption heat pumps, recent studies on advanced cycles, developments in adsorbent-adsorbate pairs and design of ad-orbent beds are described.
Abstract: Adsorption heat pumps have considerably sparked attentions in recent years. The present paper covers the working principle of adsorption heat pumps, recent studies on advanced cycles, developments in adsorbent–adsorbate pairs and design of adsorbent beds. The adsorbent–adsorbate pair features for in order to be employed in the adsorption heat pumps are described. The adsorption heat pumps are compared with the vapor compression and absorption heat pumps. The problems and troubles of adsorption heat pumps are classified and researches to overcome the difficulties are discussed.

Journal ArticleDOI
TL;DR: In this article, two types of models are mainly discussed, on the basis of first law and second law of thermodynamics, and their important characteristics of different models and their assumptions used are presented and discussed, the experimental validation of some models are also presented.
Abstract: Mathematical modeling of a latent heat thermal energy storage system (LHTES) was used for the optimum material selection and to assist in the optimal designing of the systems. In this paper, two types of models are mainly discussed, on the basis of first law and second law of thermodynamics. The important characteristics of different models and their assumptions used are presented and discussed, the experimental validation of some models are also presented.

Journal ArticleDOI
TL;DR: In this paper, the effect of various parameters such as temperature, catalyst activity and biomass /steam ratio has been discussed in view of gas yield pattern and physicochemical properties of hydrogen and its uses.
Abstract: As the demand of energy is growing faster due to society up gradation and rapid industrialization, renewable energy sources hold promise for the future energy resources in developed and third world developing countries. In contrast to conventional energy sources, non-conventional energy sources like wind, sunlight, water, and biomass have been used as renewable energy sources since ancient times. Worldwide research and energy policy are focusing towards the hydrogen economy. Hydrogen is considered as a forecast to become major source of energy in the future. Hydrogen production plays an important role in development of economy. As biomass is abundant, clean and renewable, production of hydrogen from biomass is one of the promising approaches. Present review article focuses to highlight various thermo-chemical processes for conversion of biomass into hydrogen rich gas. Effect of various parameters such as temperature, catalyst activity and biomass /steam ratio has been discussed in view of gas yield pattern in addition to physicochemical properties of hydrogen and its uses.

Journal ArticleDOI
TL;DR: In this article, an integrated theoretical framework is proposed to analyze the impact of renewable energy on local sustainability, which can be empirically applied to identify these benefits in different territories, and can be used to identify the benefits in each region.
Abstract: Renewable energy sources (RES) have a large potential to contribute to the sustainable development (SD) of specific territories by providing them with a wide variety of socioeconomic and environmental benefits. However, the existing literature has put much emphasis on the environmental benefits (including the reduction of global and local pollutants), while socioeconomic impacts have not received a comparable attention. These include diversification of energy supply, enhanced regional and rural development opportunities, creation of a domestic industry and employment opportunities. With the exception of the diversification and security of energy supply, these benefits have usually been mentioned, but their analysis has been too general (i.e., mostly at the national level) and a focus on the regional and, even more so, the local level, has been lacking. At most, studies provide scattered evidence of some of those regional and local benefits, but without an integrated conceptual framework to analyse them. This paper tries to make a contribution in this regard by developing an integrated theoretical framework which allows a comprehensive analysis of the impact of renewable energy on local sustainability and which can be empirically applied to identify these benefits in different territories.

Journal ArticleDOI
TL;DR: A literature review of use of biodiesel fuel for compression ignition engines is presented in this article, based on the reports of about 50 scientists including (some manufacturers and agencies) who published their results between 1900 and 2005.
Abstract: This article is a literature review of use of biodiesel fuel for compression ignition engines. This study is based on the reports of about 50 scientists including (some manufacturers and agencies) who published their results between 1900 and 2005. The scientists and researchers conducted the test, using different types of raw and refined oils. These experiments with raw biodiesel as fuel did not show the satisfactory results, when they used the raw biodiesel. The fuel showed injector coking and piston ring sticking. Some of the scientists mixed with methanol or ethanol in presence of KOH or NaOH and then filtered and washed. The process is called transeterfication and is used to degum, dewax and to remove triglycerides from the vegetable oils. Transeterfication decreases the viscosity, density and flash point of the fuel. The results obtained, by using such oils in compression ignition engines as fuel, were satisfactory only for short term. A vast majority of scientists mixed the transesterified biodiesel oil with diesel with different ratios. When tested in long run, blends of the oil above 20% (B20) caused maintenance problems and even sometimes damaged the engine. Some authors reported success in using vegetable oils as diesel fuel extenders in blends of more than 20% even in long-term studies. The main conclusion derived by the researchers is that coking is a potentially serious problem with the use of unmodified vegetable biodiesel. However, the refined, chemically processed and degumed vegetable oil mixed with diesel can be used to run compression ignition engine for longer duration. It was reported that there was a slight decrease in brake power and a slight increase in fuel consumption. However, the lubricant properties of the biodiesel are better than diesel, which can help to increase the engine life. Moreover, the biodiesel fuel is environment friendly, produces much less NOx and HC and absolutely no Sox and no increase in CO2 at global level.

Journal ArticleDOI
TL;DR: In this article, the authors evaluate the energy and the environmental performances of the electricity production of a wind farm and compare the impacts related to all the phases of the wind farm construction and operation to the environmental benefits due to the green electricity generation during its useful life.
Abstract: Renewable energy sources are often presented as “ clean ”. A more correct definition is that they are “cleaner” than ones based on fossil fuel conversion. When the energy consumption and the environmental impacts related to the plant's life-cycle are considered, a more comprehensive assessment of these technologies can be carried out. This paper aims to evaluate the energy and the environmental performances of the electricity production of a wind farm. The impacts related to all the phases of the wind farm construction and operation have been compared to the environmental benefits due to the “green” electricity generation during its useful life. In other terms, the goal is to trace the ecoprofile of the production of 1 kWh of electricity. A life cycle assessment (LCA) has been performed based on data related to an Italian wind farm: production and deliver of energy and raw materials, components manufacturing, transports, installation, maintenance, disassembly and disposal have been analysed. The attention focused to those life cycle steps generally neglected or not adequately investigated as installation, civil works and maintenance. The results can be assumed as representative of the Italian context and they can represent a further incentive to the diffusion of wind farms. In fact, the environmental performances of the wind farm have been compared to other power energy generation systems. The results showed a great environmental convenience of the inquired technology.

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TL;DR: In this paper, a knowledge-based review for expansion (commercialisation) of biomass-derived fuel (biofuel) through improved understanding of its economics in Africa is provided, and recommendations to overcome the technological and non-technological hurdles to market penetration of biofuels are discussed.
Abstract: Diversification of energy sources, agricultural activities and a higher percentage of locally produced energy are goals that can be satisfied by biofuels Biofuels such as biogas, biodiesel, and bioethanol may be easier to commercialise than other alternative fuels, considering performance, infrastructure and other factors Lack of a good understanding and application of key concepts of cost estimation—a key to successful project which impacts both the project profitability and influences the technical solutions—is a foremost barrier to its commercialisation in Africa, despite the availability of biomass resources A plethora of other generic technological and non-technological constrictions has been identified to also hinder biofuels adoption and development Understanding the economics of biofuel industry is, therefore, crucial in realising eventual commercialisation This article provides knowledge-based review for expansion (commercialisation) of biomass-derived fuel (biofuel) through improved understanding of its economics in Africa In addition, recommendations to overcome the technological and non-technological hurdles to market penetration of biofuels are discussed

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TL;DR: In this article, an environmental decision support system (EDSS) was proposed for selecting optimal sites for grid-connected photovoltaic power plants, taking into account environment, orography, location, and climate factors.
Abstract: Today's environmental policies are largely devoted to fostering the development and implementation in Europe of renewable energy technologies, such as grid-connected photovoltaic solar energy, which are being actively promoted by European Union countries. This article describes an environmental decision-support system (EDSS) for selecting optimal sites for grid-connected photovoltaic power plants. This system combines multicriteria analysis and the analytic hierarchy process with geographical information systems (GIS) technology and at the same time takes into account environment, orography, location, and climate factors.