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TERI Information Digest on Energy and Environment
Year : 2002, Volume : 1, Issue : 1
First page : ( 28) Last page : ( 34)
Print ISSN : 0972-6721.

Solar energy

 


[52]Capacity reliability impacts of photovoltaic power sources
Chowdhury AA. 2001Solar PV (photovoltaic) power plants are power sources whose output depends on natural factors that are statistically interdependent with the load. PV plants have significant characteristics; their power outputs are not dispatchable by the system operators. Utility dispatchers have virtually no control with regard to the amount of power available from PV plants at any instant. This kind of energy resource presents problems for a utility system planner in the computation of reliability and worth when this resource becomes integrated with a utility supply system. This paper presents a method and energy based models for assessing the impacts of PV electric power plants upon a utility supply system. It has been observed that at higher penetrations, the effects of fluctuating energy begin to dominate and the higher availability of PV units are overshadowed by energy fluctuations. The system EENS is very sensitive to changes in the amount of PV power and the amount of sunlight per year. Addition of non-dispatchable sources to a grid increases the requirements for both load following and spinning reserve capacity. If the PV sources are dispersed, their outputs will tend to even out the effects of microclimates and short-term fluctuations. The optimum PV power penetration level depends on an overall treatment that includes diverse factors such as cost per unit of electric energy, size of the system, regional opportunity to use non-dispatchable sources to best advantage and also on social and/or environmental preferences to alternatives.
(5 figures, 4 tables, 10 references)
Journal of the Institution of Engineers82:189–194
MidAmerican Energy Company,
Davenport, Iowa 52801, USA

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[53]Literature review on solar adsorption technologies for ice-making and air-conditioning purposes and recent developments in solar technology
Dieng AO and Wang RZ. 2001The use of solar adsorption systems for purposes of refrigeration and air-conditioning are gaining importance recently as they are non-polluting, energy saving and require low maintenance. However, some crucial points in the development of adsorption systems still exist and they are those associated to the low specific power of the machine and the investment costs. Research activities to solve these crucial points are increasing. This paper provides fundamental understanding of the solar adsorption systems and gives useful guidelines regarding design parameters of adsorbent bed reactors, and the applicability of solar adsorption both in air-conditioning and refrigeration. The use of adsorption chillers is gaining importance on account of their ability to utilize low temperature energy by converting waste heat or solar energy into a chilling capacity as low as 5 °C with minor maintenance costs.
(10 figures, 5 tables, 55 references)
Renewable and Sustainable Energy Reviews5(4):313–342
Institute of refrigeration and cryogencis,
Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China,
<amadou_dieng@hotmail.com>

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[54]Off-season cultivation of capsicums in a solar greenhouse
Ghosal MK and Tiwari GN. 2001The use of solar energy for growing capsicums, in pots and in the ground, has been studied under a controlled environment in a solar greenhouse and in an open field. Cooling arrangements (natural, forced convection, shading, evaporative cooling) and heating methods (ground air collector, movable insulation during the night) have been employed during the pre-winter and winter periods, respectively, to maintain the protected environment in the greenhouse. The effects of a north brick wall and the use of movable insulation during the night in the winter months to reduce the heat loss from the greenhouse have been incorporated to study the efficacy of the greenhouse. The results show that the yield of capsicum in the greenhouse is almost doubled when compared with the crops in an open field.
(5 figures, 5 tables, 13 references)
International Journal of Ambient Energy22(4):189–197
Centre for Energy Studies,
Indian Institute of Technology, Hauz Khas, New Delhi - 110 016, India
<gntiwari@ces.iitd.ernet.in>

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[55]Solar pond operated R134a based vapour absorption heat transformer for process heat generation
Murugesan SN, Saravanan R, Renganarayanan S, Mohamed KP. 2002Solar ponds provide an inexpensive means for the collection and storage of heat between 50-80 °C. They can be utilized efficiently for process heat generation if suitable vapour absorption heat transfer is used to upgrade the heat. In this paper, a ther-modynamic analysis of a vapour absorption heat transfer is presented. This uses R134a (1, 1, 1, 2 - tetrafluroethane) as refrigerant and organic fluids DMAC (dimethyl acetamide) and DMETEG (dimethylether tetraethyleneglycol) as absorbents. Variations in performance parameters CoP (coefficient of performance), circulation ratio, (second law efficiency) with the following operating parameters have been studied: (1) absorber, generator, evaporator and condenser temperatures, and (2) effectiveness of the heat exchangers. The results show that, for high temperature lift, R134a-DMAC has superior performance compared to R134a-DMETEG.
(11 figures, 1 table, 18 references)
International Journal of Ambient Energy22(3):155–161
Director,
Institute for Energy Studies, Anna University, Chennai - 600 025, India
<renga@annauniv.edu>

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[56]Heat and mass transfer coefficients in a four-tray solar crop drying system
Anwar SI and Tiwari GN. 2001In this paper a thermal analysis has been undertaken for a four-tray solar crop drying system (direct-cum-indirect type). The analysis considers basic energy balance equations. The magnitudes of different heat and mass transfer coefficients affecting moisture removal have been determined. The fourth order Runge-Kutta method had been used to solve four coupled differential equations for obtaining different temperatures and thus heat transfer coefficients and the moisture removal pattern. It has been observed that (1) the evaporative heat transfer coefficient plays the dominant role in the process of mass transfer, i.e. moisture removal, and (2) the temperature of crops kept in different trays and operating heat transfer coefficients are affected by collector length and the mass flow rate of drying air.
(14 figures, 1 table, 11 references)
International Journal of Ambient Energy22(1):48–54
Centre for Energy Studies,
Indian Institute of Technology, Hauz Khas, New Delhi - 110 015, India
<gntiwari@ces.iitd.ernet.in>

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[57]Highly insulating aerogel glazing for solar energy usage
Reim M, Beck A, Korner W, Petricevic R, et al. 2002A newly developed aerogel glazing for solar energy usage is described in this paper. Granular silica aerogels have been integrated into highly-insulating translucent glazing. To avoid settlement of the silica aerogel granules, which often occurred in earlier glazing concepts and even caused destruction to the glazing, the granules were sandwiched between a double skin sheet made of PMMA (polymethylmethacrylate) The sheet was mounted between low e-coated glass panes. To optimize the thermal insulation, krypton was used as a filling gas. The newly constructed glazing showed outstanding insulation performance with a U-value below 0.5 W/m2K, a thickness of only 50 mm, and its superior daylighting properties. If compared to the triple pane window and an opaque insulation the aerogel glazing mounted into a north oriented facade shows lowest thermal losses.
(1 figure, 5 tables, 13 references)
Solar Energy72(1):21–29
Bavarian Center for Applied Energy Research,
ZAE Bayern e V, Am Hubland, 97074 Wurzburg, Germany
<reim@zae.uni- wuerzburg.de>

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[58]Natural convection solar dryer with biomass back-up heater
Bena B and Fuller RJ. 2002One of the main disadvantages of the solar drier has been its inability to process crops under poor weather conditions and during the night. Combining a suitable biomass back-up heating system with natural convection solar dryer can improve the efficiency of the solar dryers. In this paper, a simple biomass burner, which can be made with easily available materials, tools and skills, has been demonstrated in combination with a Brace direct type solar dryer. Certain key design features of the burner contributed to produce an acceptable thermal efficiency. These features include the thermal mass on the top surface of the drum, an internal baffle plate to lengthen the exhaust gas exit path and a variable air inlet valve. However, it is believed that further improvements in the performance of both dryer and burner could be achieved through further modifications, which include (1) using two layers glazing to reduce the thermal losses from the cabinet, (2) increasing the flue diameter to increase the flow of air through the burner, (3) increasing the thickness of the central area of the thermal mass to reduce the differences in drying temperatures in the cabinet, (4) diverting the flue through the drying chamber to utilize more of the heat from the exhaust gases.
(8 figures, 2 tables, 11 references)
Solar Energy72(1):75–83
International Technologies Centre,
Faculty of Engineering, The University of Melbourne, Melbourne, Victoria 3052, Australia
<bobf@devtech.unimelb.edu.au>

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[59]Energetics of a community size solar cooker
Kaushik SC, Hasan SM, Gandhi MK, Saluja AK. 2001The renewable energy systems can only be commercialized if they are technologically appropriate, financially viable, environmentally sustainable and energetically feasible, i.e. the energy yield ratio (the ratio of total output to the total input energy) must always be greater than unity. In this paper, simple energetics of a community size solar cooker has been carried out on the basis of process analysis method. The energy yield ratio of the solar cooker is found to be greater than unity and hence this solar cooker can be said commercially viable and can be recommended for mass utilization.
(3 tables, 4 references)
Energy Opportunities16(4):11–16
Centre for Energy Studies,
Indian Institute of Technology, Hauz Khas, New Delhi - 110 016, India

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[60]Long-term stability of dye-sensitized solar cells
Hinsch A, Kroon JM, Kern R, Uhlendorf I, et al. 2001Accelerated ageing tests on large numbers of nc-DSC (nanocrystalline dye-sensitized solar cells) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long-term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long-term stability of nc-DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile-based solvents. (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 hrs at 60 °C without light soaking. (2) After 900 hours ageing at 85 °C, a decrease of 30% in maximum power has been observed. (3) After 3400 hours of combined thermal stress and continuous light soaking (45 °C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. The authors have the impression that long-term stability of dye-sensitized solar cells is not an intrinsic problem of the technology, but can be improved further by better understanding of the degradation mechanisms and chemical balancing of the electrolyte components.
(11 figures, 3 tables, 15 references)
Progress in Photovoltaics: Research and Applications9(6):425–438
Fraunhofer Institute for Solar Energy Systems,
Oltmannsstrasse 22, D-79100, Freiburg, Germany
<hinesh@ise.fhg.de>

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[61]Solar-powered systems for cooling, dehumidification and air-conditioning
Grossman G. 2002This paper describes current trends in solar-powered air conditioning, which has seen renewed interest in recent years due to the growing awareness of global warming and other environmental problems. Closed-cycle heat-powered cooling devices are based mainly on absorption chillers, a proven technology employing LiBr-water as the working fluid pair. Recent developments in gas-fired systems of this type make available double-and triple-effect chillers with considerably higher CoP than their single-effect counterparts, which makes it possible to reduce the amount of solar heat required per kW of cooling. These systems require, however, high-temperature solar collectors. The principles of multi-staging absorption systems are described. An economic comparison is provided which shows the total system cost to be dominated by the solar part of the system. At current prices, the high CoP, high temperature alternative is still more costly than the low temperature one. Open-cycle desiccant systems employing either solid or liquid sorbents are described. While the main thrust in research on novel closed-cycle absorption systems has been toward increasing the operating temperature in order to improve efficiency through multi-staging, open-cycle absorption and desiccant systems have been developed for use with low temperature heat sources such as flat plate solar collectors. A novel open-cycle DER system is described, which makes it possible to use the solar heat at relatively low temperatures, for producing both chilled and cold water, dehumidified air in variable quantities, as required by the load.
(6 figures, 1 table, 25 references)
Solar Energy72(1):53–62
Faculty of Mechanical Engineering,
Technion- Israel Institute of Technology, Technion City, Haifa 32000, Israel
<mergr01@tx.technion.ac.il>

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[62]A high-efficiency triple cycle for solar power generation
Kribus A. 2002Solar thermal electricity generation by solar-driven combined cycle is the current state-of-the-art concept, with sunlight concentration ratio of a few thousands, temperatures of about 1000-1300 °C, and overall annual average conversion efficiency of about 20%. A possible next step in this trend is presented in this paper: a solar triple cycle, with a high temperature magneto-hydro-dynamic generator and two additional cycles in series. This triple cycle is powered by solar heat at temperatures around 2000 °C and solar concentration of about 10 000. The overall peak conversion efficiency of the solar triple cycle is shown to be significantly higher than the solar combined cycle scheme. The sensitivity of this result to several system parameters and the technological feasibility of the solar triple cycle are also discussed in this paper.
(7 figures, 2 tables, 22 references)
Solar Energy72(1):1–11
Environmental Sciences and Energy Research Department,
Weizmann Institute of Science, Rehovot 76100, Israel
<nvi.kribus@weizmann.nc.il>

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[63]Modelling and performance of a forced flow solar collector/regenerator using liquid desiccant
Alizadeh S and Saman WY. 2002A model was developed in this study to predict the thermal performance of a forced parallel flow solar collector/regenerator and a parametric analysis was carried out to find out the effect of the system variables and climatic conditions on the performance. From the performance predictions presented in this work, it was determined that the water evaporation rate from the weak solution depends on regenerator length, solution mass flow rate and concentration, air Reynolds number, and the climatic conditions. Furthermore, it was found that for the regenerator operating conditions, wind velocity does not have any effect on the system performance. Another important controlling parameter was found to be the ratio of the solution to air mass flow rate. The regenerator performance could also be improved to a large extent by preheating the air and the solution.
(15 figures, 12 references)
Solar Energy72(2):143–154
Sustainable Energy Centre,
University of South Australia, School of Mechanical Engineering, Level Campus, Mawson Lakes, SA5095, Australia
<shahab_alizadeh@hotmail.com>

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[64]Solar absorption cooling with low grade heat source - a strategy of development in south China
Sumathy K, Huang ZC, and Li ZF. 2002Based on the successful experiences of operating a solar-powered cooling system in south China, to facilitate the practical development of solar cooling system, a low driving temperature strategy of solar cooling development was proposed. A new model of two-stage lithium bromide absorption chiller has been developed and test results had indicated that it is particularly advantageous for solar energy application. Two-stage chiller can be driven by hot water of temperature from 75-60 °C, which can be easily provided by conventional solar hot water systems. As a result, there is a real possibility to integrate the cooling function with the existing conventional solar hot water system to make the system efficient and cost effective. A practical integrated solar cooling and heating system with a 100 kW two-stage absorption chiller has been constructed for demonstration. The preliminary operation results are encouraging and it is hoped that with the development of low temperature driven two-stage chiller technology, solar cooling application would develop more rapidly and practically.
(7 figures, 4 tables, 12 references)
Solar Energy72(2):155–165
Department of Mechanical Engineering,
The University of Hong Kong, Hong Kong
<ksumathy@hkucc.hku.hk>

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[65]Modelling and performance of a copolymer solar water heating collector
Cristofari C, Notton G, Poggi P, Louche A. 2002Thermal behaviour, with regard to radiative and wind conditions, of a solar collector using a copolymer material 'polycarbonate' has been studied in this paper. A model for solar water heating installation has been developed and the influence of various parameters such as thickness of insulation, fluid flow rate, fluid layer thickness, and wind speed have been studied. The optimized system has an insulation of 2 cm, a thickness of 1 cm for fluid layer and works with a collector flow rate of 2.65 X 10­3 kg/m2/s. Such a system presents a yearly mean efficiency of about 49% with a wind speed of 5 m/s. The utilization of a copolymer for the total design of a copolymer for the total design of the solar collector has the advantage of reducing the weight by more than half in comparison with a traditional collector using essentially metals with similar performances. Nevertheless, the presented results are only theoretical and explanatory and in future work must be done to develop this collector and verify all these simulation results.
(11 figures, 3 tables, 23 references)
Solar Energy72(2):99–112
Universite de Corse,
Centre de Recherches 'EnergieetSystemes', U.R.A. CNRS 2053, Route des Sanguinaires, F-20000 Ajaccio, France
<cristofa@univ-corse.fr>

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[66]Comparison between a simple solar collector accumulator and a conventional accumulator
Fasulo A, Follari J, and Barral J. 2001In regions where solar radiation is abundant, it is possible to obtain domestic hot water by means of simple integral collector accumulator systems, which are less expensive than the classical flat plate active systems. The experimental assessment of two solar accumulator collector systems yielding 300 litres of hot water daily is reported in this paper. Daily diurnal global efficiency and nocturnal thermal losses have been systematically determined over a 5-month period, from austral summer to austral winter. The results of these systems were compared with the results obtained from a high quality thermosyphon solar system composed of a flat plate collector and its corresponding insulated storage tank, tested at the same time. The experiments were carried out by measuring the climatic variables, temperatures in different parts of the collectors, and mass flow rates of water, during the test days. Based on these measurements, the behavior of the systems was analysed by comparing exit temperatures, heat losses, and delivered useful energy. An economic evaluation was made considering the investment time recovery through the savings the system could provide working with different conventional sources of energy. The systems proved to work efficiently, although some improvements should be made on the semitransparent thermal insulation in order to enhance its winter performance.
(6 figures, 5 tables, 19 references)
Solar Energy71(6):389–401
University National of San Luis,
Chacabuco y Pedernera, 5700 San Luis, Argentina
<afasulo@unsl.edu.ar>

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[67]Reliability evaluation of solar photovoltaic arrays
Gautam NK, and Kaushika ND. 2002The operational lifetime of large solar PV arrays is investigated using the probability theory for the assessment of reliability. Arrays based on the following three solar cell interconnection schemes have been considered: (1) simple SP (series-parallel) array; (2) TCT (total-crossed-tied) array, which is obtained from the SP array by connecting ties across each row of junctions; and (3) BL (bridge-linked) array in which all cells are interconnected in bridge rectifier fashion. To evaluate the reliability of the BL configuration, the cut-set technique is used. Computational results based on arrays consisting of (720 X 20) solar cells indicate that the operational life of an array is almost doubled by the introduction of cross ties (TCL or BL Schemes) in the array. The operational lifetime can be further increased by ~30% by modularized networks based on TCT and BL configurations. However, these results are based on a theoretical analysis and not on measured efficiency and life expectancy of solar cells.
(13 figures, 20 references)
Solar Energy72(2):129–141
Centre for Energy Studies,
Indian Institute of Technology, Hauz Khas, New Delhi - 110 016, India
<ndkaushika@yahoo.com>

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[68]Estimating surface solar radiation from upper-air humidity
Yang K and Koike T. 2002The estimation of surface solar irradiance from humidity is very important for land surface process modelling and weather forecasting. This paper has proposed a simple global solar radiation model and compared it with the other four models. In the new model, a parameter similar to sunshine duration is proposed to indicate clearness of the sky, through which global solar radiation under cloudy skies is related to that under clear skies. The parameter is estimated from the relative humidity profile in three atmospheric sublayers. To show the applicability in Japan, the present model was compared with three simple radiation models used in numerical weather prediction systems — RAMS (Regional Atmospheric Modeling System), ARPS (Advanced Regional Prediction System), and MMS (Mesoscal Modeling System). The study indicates that the present model gives the best estimation to hourly-mean solar irradiance, and MMS radiation model performs moderately well, but RAMS and ARPS generally overestimate solar radiation.
(5 figures, 2 tables, 17 references)
Solar Energy72(2):177–186
River Laboratory,
Department of Civil Engineering, University of Tokyo, Horgo 7–3–1, Bunkyo-ku, Tokyo 113 8656, Japan
<yangk@hydra.t.u-tokyo.ac.jp>

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