Showing papers on "Solar energy published in 1986"

Simple Solar Spectral Model for Direct and Diffuse Irradiance on Horizontal and Tilted Planes at the Earth's Surface for Cloudless Atmospheres

Abstract: In a previous work, we described a simple model for calculating direct normal and diffuse horizontal spectral solar irradiance for cloudless sky conditions. In this paper, we present a new simple model (SPCTRAL2) that incorporates improvements to the simple model approach and an algorithm for calculating spectral irradiance on tilted surfaces. The model was developed using comparisons with rigorous radiative transfer codes and limited outdoor measurements. SPCTRAL2 produces terrestrial spectra between 0.3 and 4.0 μm with a resolution of approximately 10 nm. Inputs to the model include the solar zenith angle, the collector tilt angle, atmospheric turbidity, the amount of precipitable water vapor and ozone, surface pressure, and ground albedo. A major goal of this work is to provide researchers with the capability to calculate spectral irradiance for different atmospheric conditions and different solar collector geometries using microcomputers.

27.5-percent silicon concentrator solar cells

Abstract: Recent advances in silicon solar cells using the backside point-contact configuration have been extended resulting in 27.5-percent efficiencies at 10 W/cm2(100 suns, 24°C), making these the most efficient solar cells reported to date. The one-sun efficiencies under an AM1.5 spectrum normalized to 100 mW/cm2are 22 percent at 24°C based on the design area of the concentrator cell. The improvements reported here are largely due to the incorporation of optical light trapping to enhance the absorption of weakly absorbed near bandgap light. These results approach the projected efficiencies for a mature technology which are 23-24 percent at one sun and 29 percent in the 100-350-sun (10-35 W/ cm2) range.

Design of an experimental solar-powered, solid-adsorption ice maker

Abstract: Purely thermal heat pumps can be devised with adsorbate/solid adsorbent pairs, for example for refrigeration purposes. As each cycle consists of two periods, i.e., heating/desorption/condensation and cooling/adsorption/evaporation, this mode of operation is well-suited to solar energy. After experiments with the Zeolite/Water pair, a solar-powered ice maker was designed with the Activated Carbon/Methanol pair, and a prototype was built in Orsay. The solar collectors (6 m/sup 2/) contain, on the whole, 130 kg of A.C., the condensers are air-cooled, and the evaporator has a net production of 30-35 kg of ice per sunny day. The ice is easily removed, and in principle the machine could be automatically operated. The net solar C.O.P. is 0.12, which makes this machine one of the most efficient solar ice makers.

Energy savings with trees

Abstract: In conventional buildings, trees increase, decrease, or have little effect on energy use depending on general climate, building type, tree species, and tree location. Tree arrangements that save energy provide shade primarily for east and west walls and roofs and wind protection from the direction of prevailing winter winds. Particularly for buildings specially designed to use solar energy and those with solar collectors. it is important to place tree crowns so they do not block sun from collectors and south walls. But conventional houses also benefit from winter sun. Deciduous trees provide better year-round shade than conifers, but do reduce solar energy significantly even without leaves. In winter, reductions in solar energy on south walls by a deciduous tree may be greater than reductions by the same tree in summer. Hence, growth rate and crown shape are important criteria in selecting shade trees, and the placement of trees around the house is important. A summary of research data suggests that the maximum potential annual effect of trees on energy use in conventional houses Is about 20 to 25% compared to the same house in the open.

The limiting efficiency of silicon solar cells under concentrated sunlight

Abstract: The intrinsic limits on the energy conversion efficiency of silicon solar cells when used under concentrated sunlight are calculated. It is shown that Auger recombination processes are even more important under concentrated sunlight than nonconcentrated sunlight. However, light trapping can be far more effective under concentrated light due to the better defined direction of incident light. As a result of these effects, the limiting efficiency lies in tile 36-37-percent range regardless of concentration ratio compared to the limiting value of 29.8 percent for a nonconcentrating cell with isotropic response.

20% efficiency silicon solar cells

Abstract: Further improvements in crystalline silicon solar cell performance have been obtained by combining the high levels of surface recombination control demonstrated in earlier passivated emitter solar cells with an improved optical approach. This approach involves the use of microgrooved surfaces which retain the advantages of pyramidally textured surfaces while avoiding some disadvantages of the latter. The approach results in a 5–6% improvement in cell short‐circuit current density for cells fabricated on 0.1 and 0.2 Ω cm ( p type) substrates. This results in an energy conversion efficiency for these devices above 20% under standard terrestrial test conditions (AM1.5, 100 mW/cm2) for the first time.

Starting and Steady-State Characteristics of DC Motors Powered by Solar Cell Generators

Abstract: The performance of dc motors (series, separately-excited, and shunt motors) powered by a solar cell generator and loaded by two different types of loads, one a constant load and one a ventilator load, were analyzed with respect to the transient (starting) and steady state operation. Direct current motors are employed in photovoltaic water pumping systems; therefore, the understanding of the system operation and the matching of the system components (solar cells, dc motor type, and load type) are important factors of the system design. Since the solar cell generator in a nonlinear and time-dependent power supply with an output that varies with the insolation (hourly and daily), the performance characteristics of the dc motor are different when supplied by a solar cell generator than when supplied by a conventional constant voltage source. The transient solution was obtained by using an available computer program - SUPER SCEPTRE. The separately - excited (or permanent magnet) motor with a ventilator load was found to be the most suitable for the solar cell generator. The series motor is quite acceptable, but the shunt motor gives poor performance. In all cases the ventilator load is more compatible with the solar cell generator than with the constant load.

Self-contained renewable energy system

Abstract: An integrated power system is located adjacent a body of saline water. The power system includes a solar powered and a wind driven engine. Desalinization and electrolysis of the water is provided. The system produces carbon dioxide and hydrogen which are used to generate methanol. The methanol can be used as a fuel to drive a combustion engine.

Photovoltaic cell cover for use with a primary optical concentrator in a solar energy collector

Abstract: A solar energy collector including a primary optical concentrator, one or more solar cells and an improved solar cell cover design is provided. Each of the solar cells includes a flexible cell cover which significantly reduces optical losses due to gridline obscuration of active cell area and also due to reflection from the cover itself. The cover comprises an optically clear, flexible material, such as a silicone polymer, placed over the illuminated surface of each solar cell, with prisms formed on the outer surface of the cover such that incident sunlight is refracted by the prisms onto active cell area rather than partially onto non-active gridlines or conducting elements. Each of the prisms has a predetermined shape depending on the type of primary optical concentrator used in the solar energy collector.

Efficient solar energy conversion with CuInS2

Abstract: The high absorptivity associated with a direct energy gap in the optimum range for solar-energy conversion makes CuInS2 a particularly promising material for efficient solar-energy conversion1. Achieved solar-to-electrical conversion efficiencies have been limited to ∼6% (refs 2–8). We report here a new heterogeneous poly crystalline n-CuInS2 based semiconductor which has yielded conversion efficiencies of 9.7% in an electrochemical cell. The high photoactivity is also evident in a Schottky barrier solar cell configuration. The origin of the improved efficiency is attributed to impurity scavenging by In spheres resulting from a modified vapour/liquid/solid (VLS) growth process9–11 and the influence of the acidic iodine iodide electrolyte on the cell performances.

Laser Patterning Method for Integrated Type a-Si Solar Cell Submodules

Abstract: A laser patterning method was investigated as a fabrication method for integrated-type amorphous-silicon (a-Si) solar cell submodules. A three-dimensional thermal analysis of a multilayer structure was performed to determine the selective scribing conditions for each layer of an a-Si solar cell. The optimum laser power densities calculated from a three-dimensional thermal analysis were confirmed by the experiments. It was found that not only transparent conductive oxide and a-Si films, but also the metal electrodes of the integrated-type a-Si solar cell submodule were selectively scribed. The total output power of an a-Si solar cell submodule patterned by optimum laser-power densities was 9% higher than that achieved by a conventional patterning method.

Amorphous solar cell

Abstract: A solar cell of high transducing efficiency is provided in the form of a multi-cell laminated construction having n-type light receiving layers. A non-doped layer of the cell on the incident light side has an energy-gap higher than that of the lower cells.

Mercury cadmium telluride solar cell with 10. 6% efficiency

Abstract: Cd‐rich mercury cadmium telluride (MCT) is a promising material for thin‐film solar cell applications. In this letter we present data on the deposition of MCT films by a simple electroplating technique and report on the highest efficiency polycrystalline MCT thin‐film solar cell to date, which has an efficiency of 10.6% under AM1.5 illumination.

Solar energy power system

Abstract: A power system for use in converting solar energy into stored energy available as output power capable of operating diverse types of power-driven units, such as electric generators, air conditioners, etc. The power system includes solar heat collector means, a compressor system and power storage means. The solar collector system utilizes the sun's rays to heat a liquid medium, such as a refrigerant or halogen, and convert it into a gas, with the expanded gas being delivered to the compressor system whereby it effects operation of large motor means. The large motor means is integrally connected to a substantially smaller motor means operable to pressurize a compressor gas in accordance with the principle of hydraulic pressurization. The combination of the large and small motor means allows the pressure of the solar heated medium to greatly magnify the pressure developed on the compressor gas, which is transferred to the power storage system. Control means is operatively associated with the large and small motor means and operable to adjust the ratio of pressurization in response to temperature and/or pressure changes in the solar heat collector means. Appropriate valve means, valve operating means and recycling condensors are operatively associated with the compressor system and the solar collector for effecting a continued operation of the power system.

The Distribution of Concentrated Solar Radiation in Paraboloidal Collectors

Abstract: A procedure is presented for calculating the distribution of concentrated flux in paraboloidal solar collectors and is applied to idealized and practical cases. This procedure is based on the firmly established concepts of the flux integral and radiant intensity but is implemented by simple geometrical constructions involving infinitesimal pyramids based on the reflecting surface. This procedure yields a formulation well suited for numerical evaluation.

Physics, technology, and use of photovoltaics

Abstract: Photovoltaic solar energy conversion is a field that has been researched since the 1950s and which now offers one of the most promising methods for dealing with our future energy needs. It is hoped that by the 1990s, manufacturing costs will have decreased sufficiently enough to make photovoltaics an economical, large-scale source of energy. This text deals with all aspects of the subject, introducing the reader to the physics of photovoltaic solar energy conversion with general considerations applying to all types of cells. This is followed by consideration of the device physics of the most important types including crystalline silicon cells and various thin-film structures. Much of the book is devoted to the technology of the different cells, and gives a basis from which the reader should be able to compare the different solar cell technologies and also to design photovoltaic systems. It concludes with discussions on testing of solar cells and modules, photovoltaic systems and existing applications.

Renewable Energy Technologies: Their Applications in Developing Countries

Abstract: This book provides a valuable overview of the prospects for new and renewable energy technologies and their possible role in energy planning in developing countries. Contents include: biomass energy; production; conversion; utilisation; biomass engines and biomass fuels; solar energy systems; wind energy systems; and hydro energy systems.

Simplified Calculation of Solar Cell Temperatures in Terrestrial Photovoltaic Arrays

Abstract: A simplified algorithm to predict the average steady-state temperature of the solar cells in a photovoltaic array has been developed. The methodology can be applied to arrays on the roof (or walls) of buildings as well as on the ground. It is intended primarily for residential buildings, although it can be used for any type of building, and considers all four-array mounting systems (rack, stand-off, direct, and integral). Input parameters in this development include weather (insolation, ambient temperature, wind speed, humidity, and sky cloud cover), as well as building construction and operation characteristics. The photovoltaic array's geometrical, optical, and thermal properties are used in the analysis as well. Natural or forced convection under the solar panels and/or in the building attic below can also be accounted for by this model. The model has been partially verified against limited measured data and found to be in very good agreement for wind speeds of 1m/s or more.

A simulation model for solar thin-layer drying process

Abstract: A mathematical formulation of the physical process of solar drying based on conventional heat and mass transfer equations is presented. The model Includes: a a technique of estimating the solar radiation on a south-facing tilted panel using the meteorological and geographical parameters for a typical location; b the procedures for obtaining the thermal performance of a solar air-heater for a flat-plate flow-over-absorber design; c an analysis of the drying process based on the Lewis analogy and the Equilibrium Moisture Content concept. Results predicted by the simulation model are presented.