Showing papers in "Renewable & Sustainable Energy Reviews in 2001"
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TL;DR: In this article, the authors present various applications of neural networks mainly in renewable energy problems in a thematic rather than a chronological or any other order, which clearly suggest that artificial neural networks can be used for modelling in other fields of renewable energy production and use.
Abstract: Artificial neural networks are widely accepted as a technology offering an alternative way to tackle complex and ill-defined problems. They can learn from examples, are fault tolerant in the sense that they are able to handle noisy and incomplete data, are able to deal with non-linear problems and, once trained, can perform prediction and generalisation at high speed. They have been used in diverse applications in control, robotics, pattern recognition, forecasting, medicine, power systems, manufacturing, optimisation, signal processing and social/psychological sciences. They are particularly useful in system modelling such as in implementing complex mappings and system identification. This paper presents various applications of neural networks mainly in renewable energy problems in a thematic rather than a chronological or any other order. Artificial neural networks have been used by the author in the field of solar energy; for modelling and design of a solar steam generating plant, for the estimation of a parabolic trough collector intercept factor and local concentration ratio and for the modelling and performance prediction of solar water heating systems. They have also been used for the estimation of heating loads of buildings, for the prediction of air flow in a naturally ventilated test room and for the prediction of the energy consumption of a passive solar building. In all those models a multiple hidden layer architecture has been used. Errors reported in these models are well within acceptable limits, which clearly suggest that artificial neural networks can be used for modelling in other fields of renewable energy production and use. The work of other researchers in the field of renewable energy and other energy systems is also reported. This includes the use of artificial neural networks in solar radiation and wind speed prediction, photovoltaic systems, building services systems and load forecasting and prediction.
1,016 citations
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TL;DR: A literature review on absorption refrigeration technology is provided in this paper, where a number of research options such as various types of absorption refrigerator systems, research on working fluids, and improvement of absorption processes are discussed.
Abstract: This paper provides a literature review on absorption refrigeration technology. A number of research options such as various types of absorption refrigeration systems, research on working fluids, and improvement of absorption processes are discussed.
752 citations
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TL;DR: In this article, a comparison of the renewable energy sources (data from the UN World Energy Assessment Report) shows the current electrical energy cost to be 2-10 US¢/kWh for geothermal and hydro, 5-13 US¢ /kWh, 515-15 US¢ ) for biomass, 25-125 US¢ Ω(Ω/kW ) for solar photovoltaic and 12-18 US � /kW for solar thermal electricity.
Abstract: Geothermal energy for electricity generation has been produced commercially since 1913, and for four decades on the scale of hundreds of MW both for electricity generation and direct use. The utilization has increased rapidly during the last three decades. In 2000, geothermal resources have been identified in over 80 countries and there are quantified records of geothermal utilization in 58 countries in the world. The worldwide use of geothermal energy amounts to 49 TWh/a of electricity and 53 TWh/a for direct use. Electricity is produced with geothermal steam in 21 countries spread over all continents. Five countries obtain 10–22% of their electricity from geothermal energy. Only a small fraction of the geothermal potential has been developed so far, and there is ample space for an accelerated use of geothermal energy both for electricity generation and direct applications. A comparison of the renewable energy sources (data from the UN World Energy Assessment Report) shows the current electrical energy cost to be 2–10 US¢/kWh for geothermal and hydro, 5–13 US¢/kWh for wind, 5–15 US¢/kWh for biomass, 25–125 US¢/kWh for solar photovoltaic and 12–18 US¢/kWh for solar thermal electricity. Of the total electricity production from renewables of 2826 TWh in 1998, 92% came from hydropower, 5.5% from biomass, 1.6% from geothermal and 0.6% from wind. Solar electricity contributed 0.05% and tidal 0.02%. Comparing four “new” renewable energy sources (geothermal, wind, solar and tidal), shows 70% of the electricity generated by the four to come from geothermal with only 42% of the total installed capacity. Wind energy contributes 27% of the electricity, but has 52% of the installed capacity. Solar energy produces 2% of the electricity and tidal energy 1%. Biomass constitutes 93% of the total direct heat production from renewables, geothermal 5%, and solar heating 2%. Heat production from renewables is commercially competitive with conventional energy sources. The current cost of direct heat from biomass is 1–5 US¢/kWh, geothermal 0.5–5 US¢/kWh, and solar heating 3–20 US¢/kWh. Geothermal energy, with its proven technology and abundant resources, can make a significant contribution towards reducing the emission of greenhouse gases.
422 citations
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TL;DR: In this article, the authors provide fundamental understandings of the solar adsorption systems and give useful guidelines regarding designs parameters of adsorbent bed reactors, and the applicability of solar ad-sorption both in air-conditioning and refrigeration with the improvement of the coefficient of performance.
Abstract: The primary objective of this review is to provide fundamental understandings of the solar adsorption systems and to give useful guidelines regarding designs parameters of adsorbent bed reactors,and the applicability ofsolar adsorption both in air-conditioning and refrigeration with the improvement of the coefficient of performance. Solar adsorption heat pump and refrigeration devices are of significance to meet the needs for cooling requirements such as air-conditioning and ice-making and medical or food preservation in remote areas. They are also noiseless, non-corrosive and environmentally friendly. For these reasons the research activities in this sector are still increasing to solve the crucial points that make these systems not yet ready to compete with the well-known vapor compression system. There is an increasing interest in the development and use of adsorption chillers due to their various economic and impressive environmental benefits, enabling solar energy or waste heat to be used for applications such as district networks and cogeneration plants. Compared to adsorption systems that require heat sources with temperatures above 100°C (zeolite–water systems, activated carbon–methanol systems) or conventional compressor chillers, a silica gel/water adsorption refrigerator uses waste heat with temperature below 100°C. This creates new possibilities for utilizing low temperature energy.
211 citations
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TL;DR: In this paper, a three scenario analysis has been adopted to examine the future prospects of biogas in Nigeria, a country which is fossil fuels rich and an oil exporting nation, in order to contain the uncertainty usually associated with structural transformation of the economy typical of a developing country like Nigeria.
Abstract: Industrial revolution brought coal, a fossil fuel, to the forefront of the global energy scene. This was later overtaken by another fossil fuel, crude oil; and natural gas is trying fast to take over the dominant role in the world energy supply mix. The increasing world-wide awareness and concern about the environmental impacts of fossil fuels coupled with the oil price shocks of the early 1970s and late 1980s, and likely future price hikes, have lent enormous weight to a switch to renewable energy sources. This paper therefore looks at biogas (renewable) energy use in Nigeria, a country which is fossil fuels rich and an oil exporting nation. In order to contain the uncertainty usually associated with structural transformation of the economy typical of a developing country like Nigeria, a three scenario analysis has been adopted to examine the future prospects of biogas in the country. While a generated energy from biogas would range between 5.0–171.0×1012 J in the period 2000–2030 under a moderate ambitious biogas technology programme, some constraints may hinder this realization. These include economic, technical and socio–cultural constraints. Recommendations to overcome these constraints and make biogas technology penetrate even more than already projected into the rural communities and poor urban households have been suggested. Part of the envisaged benefits of biogas use to the national economy includes the avoidable CO2 emissions. If biogas displaces kerosene, at least between 357–60,952 tons of CO2 per annum would be avoided.
200 citations
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TL;DR: In this paper, the authors present an evaluation of a number of research projects in terms of their technical and economical performance and feasibility, and discuss the various lessons that have been learned through the operation and maintenance of these projects, and consider the various reasons underlying either their success or failure.
Abstract: Since the mid-seventies Saudi Arabia has been at the forefront of research and development into solar energy. For example, two major international joint research and development (R&D) programs were funded, in cooperation with the United States of America and the Federal Republic of Germany, aimed at developing renewable energy technology and demonstrating its applications by designing and installing several pilot projects. After more than 20 years of research and development it now becomes essential to evaluate these R&D activities in order to determine their benefits to the scientific community, the country, and society in general. This paper therefore presents an evaluation of a number of research projects in terms of their technical and economical performance and feasibility. The paper also discusses the various lessons that have been learned through the operation and maintenance of these projects, and considers the various reasons underlying either their success or failure.
141 citations
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TL;DR: Wang et al. as discussed by the authors developed and tested several prototype adsorption refrigeration systems, typical examples are continuous heat regenerative ad-sorption ice maker using spiral plate adsorbers, adsorsption heat pump using novel heat exchanger as adsorsbers, solar powered ad-a-sion ice maker, solar-powered hybrid system of water heater and ad-orption refrigerator, waste heat driven air conditioning system for automobiles.
Abstract: The research work on adsorption refrigeration in Shanghai Jiao Tong University (SJTU) started in 1993, various adsorption refrigeration cycles have been investigated, such as continuous heat recovery cycle, mass recovery cycle, thermal wave cycle, convective thermal wave cycle, cascade multi effect cycle, hybrid heating and cooling cycle etc. Several prototype adsorption refrigeration systems have been developed and tested, typical examples are continuous heat regenerative adsorption ice maker using spiral plate adsorbers, adsorption heat pump using novel heat exchanger as adsorbers, solar powered adsorption ice maker, solar powered hybrid system of water heater and adsorption refrigerator, waste heat driven air conditioning system for automobiles. Reasonable experimental results have been obtained, it was found that with a heat source temperature of 100°C, the refrigerator can obtain specific refrigeration power for 5.2 kg-ice/day per kg activated carbon in one adsorber, the heat pump can reach a specific cooling power for more than 150 W/kg-adsorbent with a COP close to 0.5, the adsorption solar ice maker yields 5–7 kg-ice per day per square meter solar collector, the hybrid solar water heater and ice maker is capable of heating 60 kg water up to about 90°C and meanwhile yields ice making about 5 kg per day with a 2 m 2 solar collector. The adsorption mechanisms of adsorption refrigeration pairs and also the thermo-physical properties have been also studied in SJTU, which are very helpful for adsorption refrigeration researches. This paper shows the various aspects researched in SJTU.
128 citations
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TL;DR: In this article, the authors describe the merits and demerits of various proposed electrochemical systems for electric cars, namely the storage batteries, fuel cells and electrochemical supercapacitors, and determine the power and energy requirements of a modern car.
Abstract: Road transportation, as an important requirement of modern society, is presently hindered by restrictions in emission legislations as well as the availability of petroleum fuels, and as a consequence, the fuel cost. For nearly 270 years, we burned our fossil cache and have come to within a generation of exhausting the liquid part of it. Besides, to reduce the greenhouse gases, and to obey the environmental laws of most countries, it would be necessary to replace a significant number of the petroleum-fueled internal-combustion-engine vehicles (ICEVs) with electric cars in the near future. In this article, we briefly describe the merits and demerits of various proposed electrochemical systems for electric cars, namely the storage batteries, fuel cells and electrochemical supercapacitors, and determine the power and energy requirements of a modern car. We conclude that a viable electric car could be operated with a 50 kW polymer-electrolyte fuel cell stack to provide power for cruising and climbing, coupled in parallel with a 30 kW supercapacitor and/or battery bank to deliver additional short-term burst-power during acceleration.
77 citations
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TL;DR: In this paper, the authors evaluated solar thermal systems in economic terms in comparison with energy equivalent systems such as diesel, LPG, fuel 1500 and natural gas, and eight successful applications of solar thermal system in Greek industry are presented.
Abstract: Industrial solar thermal installations of the 1980s had to face problems of poor quality and high maintenance requirements. During the 1990s the situation began to change and today in Greece there exist installations which are both economically attractive and offer significant energy saving and environmental benefits. Good potential for applications of solar thermal systems exist in sectors such as agrofood, textiles, chemicals and beverages. In this paper these systems are evaluated in economic terms in comparison with energy equivalent systems such as diesel, LPG, fuel 1500 and natural gas. The development of local solar thermal markets is described and eight successful applications of solar thermal systems in Greek industry are presented.
72 citations
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TL;DR: In this paper, a direct approach for the determination of aerodynamic performance characteristics of horizontal axis wind turbines is presented, based on Glauert's solution of an ideal windmill along with an exact trigonometric function method, analytical closed form equations are derived and given for preliminary determination of the optimum chord and twist distributions.
Abstract: This paper presents a direct approach for the determination of aerodynamic performance characteristics of horizontal axis wind turbines. Based on Glauert's solution of an ideal windmill along with an exact trigonometric function method, analytical closed form equations are derived and given for preliminary determination of the optimum chord and twist distributions. The variation of the angle of attack of the relative wind along blade span is then obtained directly from a unique equation for a known rotor size and refined blade geometry. A case study including the analysis of an existing turbine model is given and results are discussed and compared with those obtained by other investigators. It is shown that the approach used in this study is efficient and saves much of the computational time as compared with the commonly used iterative procedures.
44 citations
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TL;DR: In this article, the authors present a technique for forecasting future scenarios based on a set of projected inputs for the target year along with a projected set of technical coefficients, which are arrived at either through a regression of historical data or based on socioeconomic conditions of the study area as brought out by State or District level statistical data or through a primary survey.
Abstract: The paper presents a technique for forecasting future scenarios. The forecast is based on a set of projected inputs for the target year along with a projected set of technical coefficients. The projected inputs and the technical coefficients are arrived at either through a regression of historical data or based on socio-economic conditions of the study area as brought out by State or District level statistical data or through a primary survey. For some variables, the best farm method was also employed for projections. The application of the method is illustrated by projecting a plausible scenario for the rural segment of Kanyakumari District for the year 1995. This paper also presents the application of scenario approach to micro level planning via impact analysis of various control parameters. The advantage of scenario analysis for micro level planning is discussed and scenarios for analyzing the impact of (1) replacing field crop by plantation crop, (2) introducing energy plantation, (3) introducing fuel efficient stoves, (4) increasing fertilizer price, (5) increased fertilizer application, (6) increased population growth, (7) drought conditions, (8) decreased fuelwood availability, have been developed and discussed for arriving at plausible recommendations for energy resource generation and optimum usage of available energy resources in a given rural system under various conditions.
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TL;DR: Simplified models, performance correlations and rigorous simulation models have been identified as alternative techniques for the prediction and characterisation of the performance of natural-circulation solar energy water heaters as discussed by the authors.
Abstract: Simplified models, performance correlations and rigorous simulation models are identified as alternative techniques for the prediction and characterisation of the performance of natural-circulation solar energy water heaters. The features of particular examples of each approach are described. In their different appropriate contexts, each technique is shown to provide good agreement with measured system behaviour. A more general role in practical system design is foreseen for rigorous detailed simulation. Models have been used primarily for generic research optimisations.
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TL;DR: In this paper, the present status of research, development and manufacturing for photovoltaics in Japan based on the Japanese New Sunshine Program conducted by the Ministry of International Trade and Industry (MITI) and the New Energy and Industrial Technology Development Organization (NEDO).
Abstract: This paper reviews the present status of research, development and manufacturing for photovoltaics (PV) in Japan based on the Japanese New Sunshine Program conducted by the Ministry of International Trade and Industry (MITI) and the New Energy and Industrial Technology Development Organization (NEDO). In particular, the status of research and development on high-efficiency and low-cost crystalline silicon, thin-film silicon and Group II–VI compound solar cells and modules, and super high-efficiency Group III–V compound solar cells, is presented. In addition, Japanese government programs to promote solar houses, wherein 18,000 PV systems were installed on Japanese houses in 1999, are also demonstrated. Future prospects for PV technologies, such as silicon material, thin-film and module technologies, concentrator systems and new application fields, are discussed.
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TL;DR: The potential harnessing of tidal power has moved, spurred on by the recurring oil crises, from the back-to-front-burner, again. as mentioned in this paper provides a review of China's efforts in that domain based on several sources and trips to China and Japan.
Abstract: The potential harnessing of tidal power has moved, spurred on by the recurring oil crises, from the back- to the front-burner, again. Concerns over global warming seem to point to an absolute and urgent necessity to limit the burning of fossil fuels. China has huge reserves of coal and they are used on a very large scale to provide heating and energy. The replacement of that source of power is not to be expected in the near future, but China has been looking for several decades at alternative sources. The ocean is one of them. The paper does not aim at comprehensiveness but attempts to provide a review of China's efforts in that domain based on several sources and trips to China and Japan.
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TL;DR: In this paper, the first wind measurements evaluated in conformity with EU standards were made in the centre of Hungary in the hilly region on the bank of the river Danube near Dunaujvaros.
Abstract: The main theme of this article is the economics of wind energy investment in Hungary. The first wind measurements evaluated in conformity with EU standards were made in the centre of Hungary. The first wind turbine installation was planned in the hilly region on the bank of the river Danube near Dunaujvaros. The local wind regime was described with on site measurements and calculations as the first step. The wind speed measurements were carried out from the beginning of 1999. The wind resource is favourable in this part of the country. The results and the feasibility study indicate that the wind power plant installation is feasible and would achieve financial payback of the investment in case of governmental support. Local tower production for local installation has also been investigated.