Solar Energy Laboratory Research Articles

Research and development of evaluation technology of photovoltaic power systems

Abstract A sizing method of photovoltaic power systems is presented by using the measured quantitative efficiency and parameters in order to determine the optimum capacity of the units. A number of experimental units (total capacity 112 kW) including 5 stand-alone, 2 water pumping, and 8 grid-connected systems were constructed at the Hamamatsu Solar Energy Laboratory of the Japan Quality Assurance Organization (JQA), to simulate several types of systems. Here the parameters can be analyzed and evaluated on the basis of the data gathered from these systems. An evaluation technology of photovoltaic power systems is being developed, through the construction and data acquisition of PV power systems of various patterns, and through identification and formulation of design parameters, as well as establishment of database and simulation techniques.

Optimum conditions for a solar still and its use for a greenhouse using the nutrient film technique

A study was made on optimizing conditions in solar distillation units for increasing the yield of purified saline or brackish waters for agricultural user in a greenhouse. Two identical solar still units located at the Solar Energy Laboratory of the American University in Cairo were used to study the effect of water depth, water color, reflectors, a floating surface and addition of charcoal pieces. Using one unit as a reference unit and the other as a test unit, optimum water depth was found to be 3 cm; production increased by 39% using a red dye and 70% with a black dye. Use of reflectors was found to enhance productivity by 68%. The optimum density and thickness of floating surfaces (black sponge sheets) was 20 kg/m 3 and 3 mm thick with a productivity factor of 140%. After testing the effect of each parameter individually, the optimum parameters were combined and tested together. The productivity factor was found to be 211% using black dye, a reflector and adding large charcoal pieces. The solar still unit was mounted on a greenhouse and the integrated system tested using the Nutrient Film Technique. The distilled water output was adequate for the greenhouse agriculture and drinking water.

Analysis of the performance of direct gain systems in Alexandria, Egypt

The present paper presents an analysis of the performance of the direct gain systems using the weather data of Alexandria, Egypt (latitude 31.2°). The weather data file of Alexandria contains monthly average values of daily radiation on a horizontal surface, clearness index, ambient temperature, wind speed and relative humidity. Since TRNSYS needs hourly values of the previous parameters, the weather data generator developed at the Solar Energy Laboratory at Madison-Wisconsin is used to generate hourly data from the monthly average data available for Alexandria. TRNSYS is a transient simulation program developed at the University of Wisconsin-Madison. A numerical model is used to calculate the energy flows across the window to the building. The window model is then incorporated into TRNSYS to determine the thermal performance of the direct gain systems. The effect of the number of glazing, the building capacitance, and the night insulation resistance on the direct gain systems performance is studied. Finally, a comparison between the performance of the direct gain system and the collector-storage wall composed of concrete is carried out.

Development of a CPC with low thermal losses

Presented here is an energy balance of a compound parabolic concentrator (CPC) of 0.5 m 2 surface area, built with parabolas made of glass, in the Solar Energy Laboratory of Universidad Nacional de San Luis. Firstly, the total thermal losses of the CPC are determined experimentally and then their conductive, convective and radiative components are found, for temperatures between 60 and 150°C. With the purpose of appreciating better the effects of the last two kinds of losses, use is made of different receivers. With each of them the performance of the CPC operating under solar radiation is measured and then the energy balance is carried out. On the basis of the results obtained with the first CPC, a second was constructed with low thermal losses. For this, the cover of dull black paint on the receiver was replaced by a selective surface—black chrome on dull nickel—which has an absorptance of 0.9 (for 0.2 μ m ⩽ λ ⩽ 2 μ m) and an emittance, ϵ = 0.2 for λ ⩾ 2 μ m. Furthermore, a study of the trajectory of the rays in the interior of the CPC is carried out and the best transversal profile for an anticonvective surface, to be place 2.5 cm above the receiver, is determined. The first results that were obtained are presented here, for losses and effectiveness. A valuable improvement in the performance of the device can be noticed. In the best CPC an efficiency η equal to 0.16 is obtained for a mean temperature of 126°C for the fluid in the collector and an ambient temperature of 11°C.

F-Chart: Predictions and Measurements

Research Papers f-Chart: Predictions and Measurements J. A. Duffie, J. A. Duffie Solar Energy Laboratory, University of Wisconsin-Madison, Madison, Wis. 53706 Search for other works by this author on: This Site PubMed Google Scholar J. W. Mitchell J. W. Mitchell Solar Energy Laboratory, University of Wisconsin-Madison, Madison, Wis. 53706 Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information J. A. Duffie Solar Energy Laboratory, University of Wisconsin-Madison, Madison, Wis. 53706 J. W. Mitchell Solar Energy Laboratory, University of Wisconsin-Madison, Madison, Wis. 53706 J. Sol. Energy Eng. Feb 1983, 105(1): 3-9 (7 pages) https://doi.org/10.1115/1.3266344 Published Online: February 1, 1983 Article history Received: March 26, 1982 Online: November 11, 2009

Update on the solar power system and component research program

System analysis and component design leading to an early solar thermal power plant demonstration are the two major activities of the ongoing Solar Power System and Component Research Program being performed by the Martin Marietta/Georgia Tech team and collaborating organizations under sponsorship of National Science Foundation Grant GI-41305. Preliminary design configuration features of the point design 100-MWe solar energy/conversion power system and user applications for the direct solar/hydroelectric installations are presented. The 405-acre (1·64 km 2) plant consists of a central power station surrounded by eight solar energy collection/concentration/conversion fields, which supply the required 1250 psi, 950°F (510°C) superheated steam for turbine generator operation. Boiler and superheater assemblies in each field are mounted on a 400-ft (121·9-m) high tower at the center of the southern border of the field. In each field, 1840 mirrors perform the collection/concentration function with a single reflection of the solar energy. The user application analysis examines the potential contribution of the 100-MWe plant to a southwestern utility based on the local demand and solar weather patterns of 1973. An overview of the component testing for a bench model boiler/superheater and associated turbine generator being planned in collaboration with the Centre Nationale de la Recherche Scientifique solar energy laboratory at Odeillo. France, is presented.

Theory and experience with solar stills in Chile

A brief history of solar stills in Chile is presented. Theoretical studies of solar stills in that country are described. These deal with efficiency, thermal balance, thermal intertia, thermal capacity, thermal conductance, thermal lag and distillation lag with regard to solar irradiation maximum, and time constant. Chilean solar still designs with evaporating trays of wood, metal, cement, and plastic, and evaporating cloths of various designs have been tested by the authors. Tests were made with glass and plastic covers in the Solar Energy Laboratory of the Universidad Santa Maria (Valparaiso) and in the Atacama Desert (Quillagua). Their purpose was to make theoretical predictions of still characteristics under different environmental conditions.

Solar energy, its conversion and utilization

This paper briefly presents a summary of solar energy research, comments on the need for continuing these studies, and describes the activities of the University of Florida Solar Energy Laboratory. These activities include converting solar energy to more practical forms of power, and devising ways to produce it in the fewest possible steps by the simplest means. The devices developed are used in the University of Florida Solar House with its Solar-Electric Car and solar-heated swimming pool.

A convenient graphical method of evaluating field of view obstructions for cosine response detectors

The paper presents the results of tests carried out during the spring of 1962 at the Yellott Solar Energy Laboratory to determine the suitability of commercially available silicon photovoltaic cells for use in solar radiometers. Since the short-circuit current of the silicon cell has been shown to exhibit linear variation with varying intensity of incident radiation, this quantity was measured for six cells, selected at random, under widely varying temperatures, under both tungsten illumination and solar radiation. Over the range of temperatures likely to be encountered in solar radiometry (40 to 160 degrees F), the short-circuit current varied from 10 to 15 percent, under tungsten illumination. Under natural sunlight, the maximum variation was 6.3 percent. By measuring the millivolt drop across a small resistance, instead of determining the short-circuit current directly with a milliammeter, temperature compensation is shown to be adequately accomplished by the use of a thermistor and a Manganin wire shunting resistance, which are maintained at the temperature of the cell.The effect upon the cell coefficient of solar altitude, in terms of deviation from the cosine response and air mass effect, was then investigated, using a silicon cell radiometer which could serve both as a pyrheliometer and as a pyranometer. It was found that, for solar altitudes above 60 degrees, no correction for cosine deviation or air mass effect is necessary. For lower solar altitudes, these factors must be taken into consideration by determining the coefficient at varying solar altitudes, through calibration against a standard thermopile-type instrument.A day-long comparison of the output of a silicon cell pyranometer with the output of an Eppley 180-degree horizontal pyrheliometer showed an agreement in total radiation within 1 percent. It is concluded that, with proper calibration and adequate attention to the effects caused by solar altitude, a temperature-compensated silicon-cell pyrheliometer can be used with confidence to measure direct, total, and diffuse solar radiation with an accuracy of at least ±3 percent.

Closed-cycle, solar, hot-air engines Part 2—A [formula omitted]-Hp, pressurized engine

This paper discusses the latest closed-cycle engine in the development of small solar engines being carried out at the Solar Energy Laboratory of the University of Florida. It describes the design and construction of the engine, gives the performance efficiency of the engine and demonstrates how pressurization improves the power output of the engine.

A study of a solar air conditioner : Duffre, J. A., R. Chung, G. O. G. Löf, Solar Energy Laboratory, University of Wisconsin Mechanical Engineering, August 1963, 5 pgs incl 5 illus.

This paper proposes the use of porous matrices as the heat-absorbing media in air-cooled solar collectors. Because heat-transfer and fluid-friction data have been obtained on slit-and-expanded aluminum-foil matrices, this type is particularly discussed. Porous matrices absorb solar radiation in depth, and when arranged in a parallel-flow system, their upper surface areas are subjected to cool air, so that the upper losses are minimized. They also have high heat-transfer area/volume ratios. A matrix collector is also inexpensive and simple. An analysis of heat-transfer and fluid-friction characteristics of such a collector indicates an efficiency higher than that of flat-plate collectors, and friction losses that are much lower.

Selective radiation properties of particulate coatings : Williams, D. A., and T. A. Lappin and J. A. Duffie, Solar Energy Laboratory, Univ. of Wisconsin, Madison, Wisconsin, Journal of Engineering for Power, July, 1963, 8 pgs.

The SMall Explorer for Solar Eruptions (SMESE) mission is a microsatellite proposed by France and China. The payload of SMESE consists of three packages: LYOT (a Lyman α imager and a Lyman α coronagraph), DESIR (an Infra-Red Telescope working at 35–80 and 100–250 μm), and HEBS (a High-Energy Burst Spectrometer working in X- and γ-rays).The status of research on flares and coronal mass ejections is briefly reviewed in the context of on-going missions such as SOHO, TRACE and RHESSI. The scientific objectives and the profile of the mission are described. With a launch around 2012–2013, SMESE will provide a unique tool for detecting and understanding eruptions (flares and coronal mass ejections) close to the maximum phase of activity.

A study of a solar air conditioner : Duffie, J. A., R. Chung, and G. O. G. Löf, Solar Energy Laboratory, University of Wisconsin, Madison, Wisconsin Mechanical Engineering, 85, No. 8, August, 1963, 4 p.

An environmental control system utilizing solar energy would generally be more cost-effective if it were used to provide both heating and cooling requirements in the building it serves. Various solar powered heating systems have been tested extensively, but solar powered air-conditioners have received little more than short-term demonstration attention. This paper reviews past efforts in the field of solar powered air-conditioning systems with the absorption pair of lithium bromide and water. A number of attempts have been made by researchers to improve the performance of the solar applied air-conditioning (chiller) subsystems. It is seen that the generator inlet temperature of the chiller is the most important parameter in the design and fabrication of a solar powered air-conditioning system. While collector choice, system design and arrangement are other impacting factors for the system operation.

Simple instruments for the assessments of daily solar radiation intensity : Heywood, Harold, United Nations Conference on New Sources of Energy, Rome, 1961, 7 p.

The paper presents the results of tests carried out during the spring of 1962 at the Yellott Solar Energy Laboratory to determine the suitability of commercially available silicon photovoltaic cells for use in solar radiometers. Since the short-circuit current of the silicon cell has been shown to exhibit linear variation with varying intensity of incident radiation, this quantity was measured for six cells, selected at random, under widely varying temperatures, under both tungsten illumination and solar radiation. Over the range of temperatures likely to be encountered in solar radiometry (40 to 160 degrees F), the short-circuit current varied from 10 to 15 percent, under tungsten illumination. Under natural sunlight, the maximum variation was 6.3 percent. By measuring the millivolt drop across a small resistance, instead of determining the short-circuit current directly with a milliammeter, temperature compensation is shown to be adequately accomplished by the use of a thermistor and a Manganin wire shunting resistance, which are maintained at the temperature of the cell.The effect upon the cell coefficient of solar altitude, in terms of deviation from the cosine response and air mass effect, was then investigated, using a silicon cell radiometer which could serve both as a pyrheliometer and as a pyranometer. It was found that, for solar altitudes above 60 degrees, no correction for cosine deviation or air mass effect is necessary. For lower solar altitudes, these factors must be taken into consideration by determining the coefficient at varying solar altitudes, through calibration against a standard thermopile-type instrument.A day-long comparison of the output of a silicon cell pyranometer with the output of an Eppley 180-degree horizontal pyrheliometer showed an agreement in total radiation within 1 percent. It is concluded that, with proper calibration and adequate attention to the effects caused by solar altitude, a temperature-compensated silicon-cell pyrheliometer can be used with confidence to measure direct, total, and diffuse solar radiation with an accuracy of at least ±3 percent.

Measurement of direct, diffuse, and total solar radiation with silicon photovoltaic cells

Abstract The paper presents the results of tests carried out during the spring of 1962 at the Yellott Solar Energy Laboratory to determine the suitability of commercially available silicon photovoltaic cells for use in solar radiometers. Since the short-circuit current of the silicon cell has been shown to exhibit linear variation with varying intensity of incident radiation, this quantity was measured for six cells, selected at random, under widely varying temperatures, under both tungsten illumination and solar radiation. Over the range of temperatures likely to be encountered in solar radiometry (40 to 160 degrees F), the short-circuit current varied from 10 to 15 percent, under tungsten illumination. Under natural sunlight, the maximum variation was 6.3 percent. By measuring the millivolt drop across a small resistance, instead of determining the short-circuit current directly with a milliammeter, temperature compensation is shown to be adequately accomplished by the use of a thermistor and a Manganin wire shunting resistance, which are maintained at the temperature of the cell. The effect upon the cell coefficient of solar altitude, in terms of deviation from the cosine response and air mass effect, was then investigated, using a silicon cell radiometer which could serve both as a pyrheliometer and as a pyranometer. It was found that, for solar altitudes above 60 degrees, no correction for cosine deviation or air mass effect is necessary. For lower solar altitudes, these factors must be taken into consideration by determining the coefficient at varying solar altitudes, through calibration against a standard thermopile-type instrument. A day-long comparison of the output of a silicon cell pyranometer with the output of an Eppley 180-degree horizontal pyrheliometer showed an agreement in total radiation within 1 percent. It is concluded that, with proper calibration and adequate attention to the effects caused by solar altitude, a temperature-compensated silicon-cell pyrheliometer can be used with confidence to measure direct, total, and diffuse solar radiation with an accuracy of at least ±3 percent.

A general description of the solar energy laboratory and its initial research program

A general description of the solar energy laboratory and its initial research program