Showing papers in "Renewable & Sustainable Energy Reviews in 2007"
TL;DR: In this article, the up-to-date development of the above-mentioned technologies applied to TiO 2 photocatalytic hydrogen production is reviewed, based on the studies reported in the literature, metal ion-implantation and dye sensitization are very effective methods to extend the activating spectrum to the visible range.
Abstract: Nano-sized TiO 2 photocatalytic water-splitting technology has great potential for low-cost, environmentally friendly solar-hydrogen production to support the future hydrogen economy. Presently, the solar-to-hydrogen energy conversion efficiency is too low for the technology to be economically sound. The main barriers are the rapid recombination of photo-generated electron/hole pairs as well as backward reaction and the poor activation of TiO 2 by visible light. In response to these deficiencies, many investigators have been conducting research with an emphasis on effective remediation methods. Some investigators studied the effects of addition of sacrificial reagents and carbonate salts to prohibit rapid recombination of electron/hole pairs and backward reactions. Other research focused on the enhancement of photocatalysis by modification of TiO 2 by means of metal loading, metal ion doping, dye sensitization, composite semiconductor, anion doping and metal ion-implantation. This paper aims to review the up-to-date development of the above-mentioned technologies applied to TiO 2 photocatalytic hydrogen production. Based on the studies reported in the literature, metal ion-implantation and dye sensitization are very effective methods to extend the activating spectrum to the visible range. Therefore, they play an important role in the development of efficient photocatalytic hydrogen production.
3,714 citations
TL;DR: In this paper, a review of the alternative technological methods that could be used to produce this fuel is made, and advantages and disadvantages of technologies are listed and for all of them a kinetics model is introduced.
Abstract: Biodiesel production is a very modern and technological area for researchers due to the relevance that it is winning everyday because of the increase in the petroleum price and the environmental advantages. In this work it is made a review of the alternative technological methods that could be used to produce this fuel. Different studies have been carried out using different oils as raw material, different alcohol (methanol, ethanol, buthanol) as well as different catalysts, homogeneous ones such as sodium hydroxide, potassium hydroxide, sulfuric acid and supercritical fluids, and heterogeneous ones such as lipases. In this work advantages and disadvantages of technologies are listed and for all of them a kinetics model is introduced.
1,323 citations
TL;DR: In this article, a review of the production of activated carbons from agricultural residues is presented, and the effects of various process parameters on the pyrolysis stage are reviewed.
Abstract: A review of the production of activated carbons from agricultural residues is presented. The effects of various process parameters on the pyrolysis stage are reviewed. Influences of activating conditions, physical and chemical, on the active carbon properties are discussed. Under certain process conditions several active carbons with BET surface areas, ranging between 250 and 2410 m 2 /g and pore volumes of 0.022 and 91.4 cm 3 /g, have been produced. A comparison in characteristics and uses of activated carbons from agricultural residues with those issued from tires, and commercial carbons, have been made. A review is carried out of the reaction kinetic modelling, applied to pyrolysis of agricultural wastes and activation of their pyrolytic char.
1,203 citations
TL;DR: In this paper, the state of the art of phase change materials (PCMs) for storing solar energy is discussed. But, prior to the large-scale practical application of this technology, it is necessary to resolve numerous problems at the research and development stage.
Abstract: The continuous increase in the level of greenhouse gas emissions and the climb in fuel prices are the main driving forces behind efforts to more effectively utilise various sources of renewable energy. In many parts of the world, direct solar radiation is considered to be one of the most prospective sources of energy. However, the large-scale utilisation of this form of energy is possible only if the effective technology for its storage can be developed with acceptable capital and running costs. One of prospective techniques of storing solar energy is the application of phase change materials (PCMs). Unfortunately, prior to the large-scale practical application of this technology, it is necessary to resolve numerous problems at the research and development stage. This paper looks at the current state of research in this particular field, with the main focus being on the assessment of the thermal properties of various PCMs, methods of heat transfer enhancement and design configurations of heat storage facilities to be used as a part of solar passive and active space heating systems, greenhouses and solar cooking.
1,173 citations
TL;DR: In this article, the authors presented an overview of the current and projected energy scene and presented the size of respective wind and solar farms that would be required for each of the five countries under discussion to meet their year 2020 energy demands.
Abstract: Energy is inevitable for human life and a secure and accessible supply of energy is crucial for the sustainability of modern societies. Continuation of the use of fossil fuels is set to face multiple challenges: depletion of fossil fuel reserves, global warming and other environmental concerns, geopolitical and military conflicts and of late, continued and significant fuel price rise. These problems indicate an unsustainable situation. Renewable energy is the solution to the growing energy challenges. Renewable energy resources such as solar, wind, biomass, and wave and tidal energy, are abundant, inexhaustible and environmentally friendly. This article provides an overview of the current and projected energy scene. Five countries, that presently have a significant impact on global energy situation, have been studied in this work. These include China, India, Russia, UK and USA. Together the present energy budget of these countries is roughly half that of the globe. Four of the above five countries that are discussed in this work—China, India, UK and USA are all net importers of energy and are heavily dependent on imports of fuel to sustain their energy demands. Their respective local oil reserves will only last 9, 6, 7 and 4 years, respectively. China, the emerging economy in the world, is however making exemplary development in renewable energy—in 2004 renewable energy in China grew by 25% against 7–9% growth in electricity demand. While in the same year, wind energy in China saw a growth of 35%. China is also leading the global solar thermal market as it has already installed solar collectors over 65 million square meters, accounting for more than 40% of the world's total collector area. This article quantifies the period of exhaustion of the current major energy sources, i.e. coal, oil, gas and nuclear fissile material. Projected demand for energy is also presented and a feasibility of switch over to renewable energy is discussed. The article also presents the size of respective wind- and solar farms that would be required for each of the five countries under discussion to meet their year 2020 energy demands. It has been found that to meet 50% of the total energy demands the proposed area for collection of solar and wind energy by means of ultra-large scale farms in fact will occupy a mere fraction of the available land and near-offshore area for the respective countries, e.g. a solar PV electricity farm of 61 km 2 for China represents 0.005% of the Gobi desert. Likewise, the 26 and 36 km 2 PV farm area, respectively, required for India and the US represents 0.01% and 0.014% land area of Rajasthan and Baja deserts. The above areas required for the farms may be further split to form a cluster of smaller energy farms.
1,082 citations
TL;DR: A comprehensive review of various possible methods for heating and cooling in buildings is discussed in this article, where the thermal performance of various types of systems like PCM trombe wall, PCM wallboards, and PCM shutters are presented.
Abstract: A comprehensive review of various possible methods for heating and cooling in buildings are discussed in this paper. The thermal performance of various types of systems like PCM trombe wall, PCM wallboards, PCM shutters, PCM building blocks, air-based heating systems, floor heating, ceiling boards, etc., is presented in this paper. All systems have good potential for heating and cooling in building through phase change materials and also very beneficial to reduce the energy demand of the buildings.
933 citations
TL;DR: In this article, the authors argue that public attitudes towards renewable energy are fundamentally different from attitudes towards wind farms and that feelings about equity and fairness appear the determinants of "backyard" motives, instead of selfishness.
Abstract: Public attitudes anywhere in Europe show moderate to strong support for the implementation of renewable energy. Nevertheless, planning wind power developments appears to be a complicated matter in most countries. The problems that have to be dealt with during decision making processes on the siting of wind turbines are usually referred to as mere ‘communication problems’. However, public attitudes towards wind power are fundamentally different from attitudes towards wind farms. This ‘gap’ causes misunderstandings about the nature of public support for renewables. In particular where planners easily assume support for renewables can be generated by information campaigns emphasising the environmental benefits, whereas opposition to renewable energy schemes can be explained by a selfish ‘not in my backyard’ attitude. Both explanations used by planners, authorities and, unfortunately, by many scholars, are falsified. Furthermore, policies that still take this ‘common knowledge’ for granted can have negative consequences for the implementation rates of renewables. Visual evaluation of the impact of wind power on landscape values is by far the dominant factor in explaining why some are opposed to wind power and others are supporting it. Moreover, feelings about equity and fairness appear the determinants of ‘backyard’ motives, instead of selfishness.
911 citations
TL;DR: In this article, the wind resources assessment models, site selection models and aerodynamic models including wake effect are reviewed and different performance and reliability evaluation models, various problems related to wind turbine components (blade, gearbox, generator and transformer) and grid for wind energy system have been discussed.
Abstract: Energy is an essential ingredient of socio-economic development and economic growth. Renewable energy sources like wind energy is indigenous and can help in reducing the dependency on fossil fuels. Wind is the indirect form of solar energy and is always being replenished by the sun. Wind is caused by differential heating of the earth's surface by the sun. It has been estimated that roughly 10 million MW of energy are continuously available in the earth's wind. Wind energy provides a variable and environmental friendly option and national energy security at a time when decreasing global reserves of fossil fuels threatens the long-term sustainability of global economy. This paper reviews the wind resources assessment models, site selection models and aerodynamic models including wake effect. The different existing performance and reliability evaluation models, various problems related to wind turbine components (blade, gearbox, generator and transformer) and grid for wind energy system have been discussed. This paper also reviews different techniques and loads for design, control systems and economics of wind energy conversion system.
908 citations
TL;DR: In this paper, the authors summarize recent developments in research on the heat transfer characteristics of nanofluids for the purpose of suggesting some possible reasons why the suspended nanoparticles can enhance the heat-transfer of conventional fluids and to provide a guide line or perspective for future research.
Abstract: Researches in heat transfer have been carried out over the previous several decades, leading to the development of the currently used heat transfer enhancement techniques. The use of additives is a technique applied to enhance the heat transfer performance of base fluids. Recently, as an innovative material, nanometer-sized particles have been used in suspension in conventional heat transfer fluids. The fluids with these solid-particle suspended in them are called ‘nanofluids’. The suspended metallic or nonmetallic nanoparticles change the transport properties and heat transfer characteristics of the base fluid. The aim of this review is to summarize recent developments in research on the heat transfer characteristics of nanofluids for the purpose of suggesting some possible reasons why the suspended nanoparticles can enhance the heat transfer of conventional fluids and to provide a guide line or perspective for future research.
709 citations
TL;DR: In this paper, the authors summarized the published subjects with respect to the forced convective heat transfer of the nanofluids both of experimental and numerical investigation, and they also evaluated the effective viscosity.
Abstract: A nanofluid is a suspension of ultrafine particles in a conventional base fluid which tremendously enhances the heat transfer characteristics of the original fluid. Furthermore, nanofluids are expected to be ideally suited in practical applications as their use incurs little or no penalty in pressure drop because the nanoparticles are ultrafine, therefore, appearing to behave more like a single-phase fluid than a solid–liquid mixture. About a decade ago, several published articles focused on measuring and determining the effective thermal conductivity of nanofluids, some also evaluated the effective viscosity. There are only a few published articles on deriving the forced convective heat transfer of nanofluids. The purpose of this article is to summarize the published subjects respect to the forced convective heat transfer of the nanofluids both of experimental and numerical investigation.
677 citations
TL;DR: In this paper, the authors describe various methods developed for aiding decision makers in reaching better decisions, including value measurement models, goal, aspiration and reference level models, and outranking models.
Abstract: Most decision making requires the consideration of several conflicting objectives. The term multiple criteria decision analysis (MCDA) describes various methods developed for aiding decision makers in reaching better decisions. Energy planning problems are complex problems with multiple decision makers and multiple criteria. Therefore, these problems are quite suited to the use of MCDA. A multitude of MCDA methods exists. These methods can be divided in three main groups; value measurement models, goal, aspiration and reference level models, and outranking models. Methods from all of these groups have been applied to energy planning problems, particularly in the evaluation of alternative electricity supply strategies. Each of the methods has its advantages and drawbacks. However, we cannot conclude that one method generally is better suited than the others for energy planning problems. A good alternative might be to apply more than one method, either in combination to make use of the strengths of both methods, or in parallel to get a broader decision basis for the decision maker. Until now, studies of MCDA in energy planning have most often considered energy networks with only one energy carrier. More advanced energy systems with multiple energy carriers have been neglected, even though this field ought to be suitable for use of MCDA due to its high complexity, many decision makers and many conflicting criteria.
TL;DR: In this article, the most significant experience in power generation from biomass liquids produced by fast pyrolysis processes is reviewed and R&D needs identified for each power plant technologies addressed are diesel engines, gas turbines, and natural gas/steam power plants.
Abstract: Power production from biomass derived pyrolysis liquids has been under development for the past few years. If technically successful, it would make decentralized bio-energy production possible. Several technologies and system components have been developed by academia, R&D organizations, and industrial companies in many countries. Much experience has been gained and many useful results published. The present work aims at reviewing the most significant experience in power generation from biomass liquids produced by fast pyrolysis processes. Power plant technologies addressed are diesel engines, gas turbines, and natural gas/steam power plants. Main results are reviewed and R&D needs identified for each technology. The analysis shows that even for the most promising solutions long-term demonstration has not yet been achieved. Pyrolysis liquid use in gas turbine plants and in co-firing mode in large power stations are technically most advanced. Recent work with diesel engines also appears quite promising.
TL;DR: In this article, the relative prospects and the competitive force of Proton Exchange Membrane Fuel Cells (PEMFCs) in transportation, residential power generation and portable computers are discussed.
Abstract: Proton exchange membrane fuel cells (PEMFCs) have recently passed the test or demonstration phase and have partially reached the commercialization stage due to the impressive worldwide research effort. Despite the currently promising achievements and the plausible prospects of PEMFCs, there are many challenges remaining that need to be overcome before PEMFCs can successfully and economically substitute for the various traditional energy systems. With the many promising research efforts in overcoming these challenges, the most important tools for the commercialization of PEMFCs will be the technical data and information from a real PEMFC application test. For these reasons, this paper introduces and discusses the remaining challenges and some of the latest research on the application test of PEMFC to real systems such as transportation, residential power generation and portable computers. In addition, this paper describes and summarizes the relative prospects and the competitive force of PEMFCs in these fields. These prospects primarily depend on stable and economical high-purity hydrogen supplies, the scale of application, the existence of more efficient competitive power sources and the social viewpoints such as the health and environment benefits as well as infrastructural aspects associated with traditional power supply and demand. The review shows that PEMFC have the most promising applications to buses, recreation vehicles, and lightweight vehicles. Without doubt, the technology for a stable supply of high-purity hydrogen along with the corresponding infrastructure is essential for the success of PEMFC in various application fields.
TL;DR: In this article, a flywheel over 10 kV has not been constructed, mainly due to isolation problems associated with high voltage, but also because of limitations in the power electronics and the predominant part of prior studies have been directed towards optimising mechanical issues whereas the electro technical part now seem to show great potential for improvement.
Abstract: For ages flywheels have been used to achieve smooth operation of machines. The early models where purely mechanical consisting of only a stone wheel attached to an axle. Nowadays flywheels are complex constructions where energy is stored mechanically and transferred to and from the flywheel by an integrated motor/generator. The stone wheel has been replaced by a steel or composite rotor and magnetic bearings have been introduced. Today flywheels are used as supplementary UPS storage at several industries world over. Future applications span a wide range including electric vehicles, intermediate storage for renewable energy generation and direct grid applications from power quality issues to offering an alternative to strengthening transmission. One of the key issues for viable flywheel construction is a high overall efficiency, hence a reduction of the total losses. By increasing the voltage, current losses are decreased and otherwise necessary transformer steps become redundant. So far flywheels over 10 kV have not been constructed, mainly due to isolation problems associated with high voltage, but also because of limitations in the power electronics. Recent progress in semi-conductor technology enables faster switching and lower costs. The predominant part of prior studies have been directed towards optimising mechanical issues whereas the electro technical part now seem to show great potential for improvement. An overview of flywheel technology and previous projects are presented and moreover a 200 kW flywheel using high voltage technology is simulated.
TL;DR: Wang et al. as discussed by the authors reviewed the present utilized technologies of straw in biomass energy, including improved stove, biogas, straw gasification and straw briquette, which are already commercialized and popularized in China.
Abstract: China is a big agricultural country and one of the most abundant straw resources in the world, producing more than 620 million tons of straw in 2002, and representing about 33–45% of energy consumption for livelihood in rural areas. Utilization of straw as energy with high efficiency and rationality not only meets the demands for energy as the economy grows, but also provide a basis for environmental protection and sustainable development of society in China. This paper reviews the present utilized technologies of straw in biomass energy, including improved stove, biogas, straw gasification and straw briquette, which are already commercialized and popularized in China. Other technologies, such as liquefaction, straw carbonization and bio-coal, are also presented. Based on the technology status and potential, the future research and development of straw in the biomass energy portfolio in China are proposed.
TL;DR: The main obstacles for large scale application, beside the high first cost, are the lack of practical experience and acquaintance among architects, builders and planners with the design, control and operation of these systems as mentioned in this paper.
Abstract: Summer air conditioning represents a growing market in buildings worldwide, with a particularly significant growth rate observed in European commercial and residential buildings. Heat-driven cooling technologies are available, which can be used in combination with solar thermal collectors to alleviate the burden caused by air conditioning on the electric utilities and the environment. Solar air conditioning has progressed considerably over the past years as a result of efforts toward environmental protection and new developments in components and systems, and significant experience has been gained from demonstration projects. The main obstacles for large scale application, beside the high first cost, are the lack of practical experience and acquaintance among architects, builders and planners with the design, control and operation of these systems. This paper describes the main results of the EU project SACE (Solar Air Conditioning in Europe), aimed to assess the state-of-the-art, future needs and overall prospects of solar cooling in Europe. A group of researchers from five countries has surveyed and analyzed over 50 solar-powered cooling projects in different climatic zones. The paper presents a short overview on the state-of-the-art and potential of solar-assisted cooling and air conditioning technologies. The results of the study, including a database of the surveyed projects, an evaluation of these projects on a uniform basis, an economic analysis tool, user guidelines and a multimedia tool—are presented. The potential energy savings and limitations of solar thermal air conditioning in comparison to conventional technologies are illustrated and discussed.
TL;DR: In this article, the authors give an overview of different decentralized energy models used worldwide, their approaches and their applications along with a few emerging energy models, and explain the need of DEP and shows how different types of energy planning and optimization models, supply demand models, regional models, resource models and neural models have been carried, adopted and applied at decentralized level.
Abstract: Energy planning is carried out at a centralized level using computer-based modeling. The centralized energy planning models and approaches have already been reviewed in literature. Decentralized energy planning (DEP) is a concept of recent origin with limited applications. Literature shows that different models are being developed and used worldwide. This paper gives an overview of different decentralized energy models used worldwide, their approaches and their applications along with a few emerging energy models. The central theme of the energy planning at decentralized level would be to prepare an area-based DEP to meet energy needs and development of alternate energy sources at least-cost to the economy and environment. Ecologically sound development of the region is possible when energy needs are integrated with the environmental concerns at the local and global levels. Taking into account these features, this paper explains the need of DEP and shows how different types of energy planning and optimization models, supply demand models, regional models, resource models and neural models have been carried, adopted and applied at decentralized level.
TL;DR: In this paper, the experimental introduction of biogas plants in Denmark since the 1970s is reviewed, and the authors argue that three factors have been important for the current status of Biogas Plants in Denmark: the Danish government applied a bottom-up strategy and stimulated interaction and learning between various social groups.
Abstract: With 20 centralised plants and over 35 farmscale plants, the digestion of manure and organic waste is a well established technological practice in Denmark. These plants did not emerge without a struggle. Moreover, no new centralised plants have been established since 1998 and the development of farmscale plants has slowed down. This article reviews the experimental introduction of biogas plants in Denmark since the 1970s. We argue that three factors have been important for the current status of biogas plants in Denmark. First, the Danish government applied a bottom-up strategy and stimulated interaction and learning between various social groups. Second, a dedicated social network and a long-term stimulation enabled a continuous development of biogas plants without interruptions until the late 1990s. Third, specific Danish circumstances have been beneficial, including policies for decentralised CHP, the existence of district heating systems, the implementation of energy taxes in the late 1980s and the preference of Danish farmers to cooperate in small communities. The current setback in biogas plants is mainly caused by a shift in energy and environmental policies and limited availability of organic waste.
TL;DR: A survey of solar-based driven thermoelectric technologies and their applications is presented in this paper, where a brief analysis of the environmental problems related to the use of conventional technologies and energy sources is presented and the benefits of using renewable energy systems are outlined.
Abstract: In this paper a survey of solar-based driven thermoelectric technologies and their applications is presented. Initially, a brief analysis of the environmental problems related to the use of conventional technologies and energy sources is presented and the benefits offered by thermoelectric technologies and renewable energy systems are outlined. The development history of solar-based thermoelectric technologies is introduced together with the discussion of the existing drawbacks of current systems. Typical applications of the solar-driven thermoelectric refrigeration and the solar-driven thermoelectric power generation are presented in order to show to the reader the extent of their applicability. The application areas described in this paper show that solar-driven thermoelectric technologies could be used in a wide variety of fields. They are attractive technologies that not only can serve the needs for refrigeration, air-conditioning applications and power generation, but also can meet demand for energy conservation and environment protection.
TL;DR: In this paper, the authors examined four mutually exclusive scenarios for the expansion of the Greek electricity system developed by official authorities and representing alternative views on meeting electricity demand and concluded that the scenario assuming the highest penetration of renewable energy sources is the best compromise configuration for the Greek power generation sector.
Abstract: This paper examines four mutually exclusive scenarios for the expansion of the Greek electricity system developed by official authorities and representing alternative views on meeting electricity demand. The aim is to encompass all positive and negative side-effects characterizing the electricity generation technologies assumed to participate in each scenario and emphasis is given to the particular role of renewable energy sources which represent a major differentiating factor between them. The calculation of economic, technical and environmental performances of the examined scenarios for the year 2010 shows that electricity planning is a complicated task since improvements in one policy target are accompanied by losses in others. In order to resolve this conflict, the scenarios are comparatively evaluated with two decision support techniques, multicriteria decision analysis and cost–benefit analysis, which are capable of broadening the strict boundaries of a financial analysis while avoiding intuitive solutions that are often applied in practice. Following the two completely different evaluation approaches, it is confirmed that the scenario assuming the highest penetration of renewable energy sources is the best compromise configuration for the Greek power generation sector.
TL;DR: In this article, the authors provide a thermo-analytical and physical-chemistry characterization of castor oil and biodiesel, and show that biodiesel data are very close to the volatilization temperatures of conventional diesel.
Abstract: The castor oil seed has 47–49% of oil. Biodiesel obtained from castor oil has a lower cost compared to the ones obtained from other oils, as due its solvability in alcohol transesterification occurs without heating. The use of biodiesel will allow a reduction on the consumption of petroleum-derived fuels minimizing the harmful effects on the environment. This work wants to provide a thermoanalytical and physical-chemistry characterization of castor oil and biodiesel. Biodiesel was obtained with methyl alcohol and characterized through several techniques. Gas chromatography indicated methyl ester content of 97.7%. The volatilization of biodiesel starts and finishes under inferior temperatures than the beginning and final volatilization temperatures of castor oil. Biodiesel data are very close to the volatilization temperatures of conventional diesel.
TL;DR: In this article, the authors have tried to broadly categorize the research work done so far on the basis of hydro plant model development and its controller design under different sections, and have found a substantial number of relevant research papers can be found on the plant modeling, design aspects of control methodologies and their performance study.
Abstract: The recent increased number of black outs in the power system has been largely due to growing competition and deregulation among the power industry. Power systems are complex nonlinear systems and often exhibit low frequency electro-mechanical oscillations due to insufficient damping caused by severe operating conditions. This needs an advanced modeling and control techniques for effective control of power plants. In case of hydroelectric plant the hydro turbine is a non-linear, non-stationary multivariable system whose characteristics vary significantly with the unpredictable load on it and this presents a difficulty in designing an efficient and reliable controller. A conservatively designed control fails to perform as expected. Keeping this in mind, hydro plant control is an application area with an interesting set of problems for control engineering people. Mainly some of these problems focus towards regulation of turbine with large load variation in the power system. These problems have not been adequately solved and continue to pose challenges to the control community. In this review paper, the authors have tried to broadly categorize the research work done so far on the basis of hydro plant model development and its controller design under different sections. A substantial number of relevant research papers can be found on the plant modeling, design aspects of control methodologies and their performance study.
TL;DR: In this article, the authors reviewed the studies conducted on the energy and exergy analysis of SAHPS systems in Turkey and around the world as of the end of December 2004.
Abstract: During the last decade, a number of studies have been conducted by various investigators in the design, modeling and testing of solar assisted heat pump systems (SAHPSs). This paper reviews the studies conducted on the energy and exergy analysis of SAHPS systems in Turkey and around the world as of the end of December 2004. The studies undertaken on the SAHPS systems are categorized into four groups as follows: (i) SAHPSs for water heating, (ii) SAHPSs with storage (conventional type) for space heating, (iii) SAHPSs with direct expansion for space heating, and (iv) Solar-assisted ground source heat pump greenhouse heating system (SAGSHPGHS). This paper investigates the studies on SAGSHPs, especially ground-source heat pumps, also known geothermal heat pumps, at the Turkish universities in more detail, by giving Turkey's solar energy potential.
TL;DR: In this paper, the authors used RetScreen software for energy production and economical assessment of a 5MW installed capacity photovoltaic-based grid connected power plant for electricity generation.
Abstract: This paper utilizes monthly average daily global solar radiation and sunshine duration data to study the distribution of radiation and sunshine duration over Saudi Arabia. The analysis also includes the renewable energy production and economical evaluation of a 5 MW installed capacity photovoltaic based grid connected power plant for electricity generation. The study utilizes RetScreen software for energy production and economical assessment. It is found that the global solar radiation varies between a minimum of 1.63 MWh/m2 yr–1 at Tabuk and a maximum of 2.56 MWh/m2 yr–1 at Bisha while the mean remained as 2.06 MWh/m2 yr–1. The duration of sunshine varied between 7.4 and 9.4 h with an overall mean of 8.89 h. The specific yield was found to vary from 211.5 to 319.0 kWh/m2 with a mean of 260.83 kWh/m2. The renewable energy produced each year from 5 MWp installed capacity plant was varied between 8196 and 12,360 MWh while the mean remained as 10,077 MWh/yr–1. The economical indicators like internal rate of return, the simple payback period, the years to positive cash flows, the net present value, the annual life cycle savings, the profitability index and the cost of renewable energy production showed that Bishah was the best site for PV based power plant development and Tabuk the worst. From environmental point of view, it was found that on an average an approximate quantity of 8182 ton of green house gases can be avoided entering into the local atmosphere each year.
TL;DR: In this paper, the authors have discussed the application of Geographical Information System (GIS) to map the renewable energy potential talukwise in Karnataka State, India, which is an administrative division in the federal set-up in India to implement developmental programmes like dissemination of biogas, improved stoves, etc.
Abstract: An energy resource that is renewed by nature and whose supply is not affected by the rate of consumption is often termed as renewable energy. The need to search for renewable, alternate and non-polluting sources of energy assumes top priority for self-reliance in the regional energy supply. This demands an estimat+ion of available energy resources spatially to evolve better management strategies for ensuring sustainability of resources. The spatial mapping of availability and demand of energy resources would help in the integrated regional energy planning through an appropriate energy supply–demand matching. This paper discusses the application of Geographical Information System (GIS) to map the renewable energy potential talukwise in Karnataka State, India. Taluk is an administrative division in the federal set-up in India to implement developmental programmes like dissemination of biogas, improved stoves, etc. Hence, this paper focuses talukwise mapping of renewable energy (solar, wind, bioenergy and small hydroenergy) potential for Karnataka using GIS. GIS helps in spatial and temporal analyses of the resources and demand and also aids as Decision Support System while implementing location-specific renewable energy technologies.
Regions suitable for tapping solar energy are mapped based on global solar radiation data, which provides a picture of the potential. Coastal taluks in Uttara Kannada have higher global solar radiation during summer $(6.31 kWh/m^2)$, monsoon $(4.16 kWh/m^2)$ and winter $(5.48 kWh/m^2)$. Mapping of regions suitable for tapping wind energy has been done based on wind velocity data, and it shows that Chikkodi taluk, Belgaum district, has higher potential during summer (6.06 m/s), monsoon (8.27 m/s) and winter (5.19 m/s). Mysore district has the maximum number of small hydropower plants with a capacity of 36 MW. Talukwise computation of bioenergy availability from agricultural residue, forest, horticulture, plantation and livestock indicates that Channagiri taluk in Shimoga district yields maximum bioenergy. The bioenergy status analysis shows that Siddapur taluk in Uttara Kannada district has the highest bioenergy status of 2.004 (ratio of bioresource availability and demand).
TL;DR: A review of the research state of art of the solar sorption (absorption and adsorption) refrigeration technologies is presented in this paper, where the application areas of these technologies are categorized by cooling temperature demand.
Abstract: In this paper, a review of the research state of art of the solar sorption (absorption and adsorption) refrigeration technologies is presented. After an introduction of basic principles, the development history and recent progress in solar sorption refrigeration technologies are reported. The application areas of these technologies are categorized by cooling temperature demand. It shows that solar-powered sorption refrigeration technologies are attractive alternatives that not only can serve the needs for air-conditioning, refrigeration, ice making and congelation purposes, but also can meet demand for energy conservation and environment protection. However, a lot of research work still needs to be done for large-scale applications in industry and for the replacement of conventional refrigeration machines.
TL;DR: In this article, the authors present a strategic planning process for the province of Jaen, a southern Spanish region whose economy is mainly based on olive agriculture, aiming at a major socioeconomic development.
Abstract: Strategic planning processes, which are commonly used as a tool for region development and territorial structuring, can be harnessed by politicians and public administrations, at the local level, to redesign the regional energy system and encourage renewable energy development and environmental preservation. In this sense, the province of Jaen, a southern Spanish region whose economy is mainly based on olive agriculture, has carried out its strategic plan aiming at a major socioeconomic development. Under the leadership of the provincial government and the University of Jaen, main provincial institutions joined to propose the elaboration of a participatory strategic plan for the whole province. Here, the elaboration of the energy part of the plan, which was directly focused on the exploitation of renewable resources, mainly solar and biomass energy, and which highlights the effectiveness of techniques from business management applied to a sustainable energy model design is presented. Renewable Energy development during the first years of plan execution is presented, and the impact of additional issues is discussed. It is concluded that, although multicriteria decision-making technologies (MCDA) are extensively used in energy planning, a different approach can be utilized to incorporate techniques from strategic analysis. Furthermore, SWOT (strengths, weaknesses, opportunities and threats) analysis has proved to be an effective tool and has constituted a suitable baseline to diagnose current problems and to sketch future action lines.
TL;DR: In this article, the authors argue that photovoltaics and renewable energies are growing at a much faster pace than the rest of the economy in Europe and worldwide and that renewable energy sources for the generation of heat and the use of environment friendly biofuels for the transport sector will become more and more important in the future.
Abstract: Photovoltaics and renewable energies are growing at a much faster pace than the rest of the economy in Europe and worldwide. This and the dramatic oil price increases in 2005 have led to a remarkable re-evaluation of the renewable energy sector by politics and financing institutions. Despite the fact that there are still discrepancies between the European Union and the USA, as to how to deal with climate change, renewable energies will play an important role for the implementation of the Kyoto Protocol and the worldwide introduction of tradable Green Certificates. Apart from the electricity sector, renewable energy sources for the generation of heat and the use of environment friendly biofuels for the transport sector will become more and more important in the future.
TL;DR: A review of electrohydrodynamic heat transfer enhancement can be found in this paper, where the authors present a guideline for the researcher in using EHD techniques for heat transfer enhancing.
Abstract: The heat transfer duty of heat exchangers can be improved by heat transfer enhancement techniques. In general, these techniques can be divided into two groups: active and passive techniques. The active techniques require external forces, e.g. electric field, acoustic or surface vibration etc. The passive techniques require fluid additives or special surface geometries. Electrohydrodynamic (EHD) techniques have been introduced as one of the types of active heat transfer enhancement techniques. This paper presents a review of research works on electrohydrodynamic heat transfer enhancement. This paper can be used as the first guideline for the researcher in using EHD techniques for heat transfer enhancement.
TL;DR: The main problems of the connection of wind farms to the grid are reviewed and how the grid codes must be adapted in order to integrate wind power generation capacity without affecting the quality and stability of the grid.
Abstract: The increase of the wind power penetration in the electrical grids of Denmark, Germany, Spain and other countries and regions is challenging the stability of the system. The subject of this paper is to review the main problems of the connection of wind farms to the grid and how the grid codes must be adapted in order to integrate wind power generation capacity without affecting the quality and stability of the grid. This paper also summarizes the grid codes that have already been modified to incorporate high levels of wind power.