Showing papers on "Solar power published in 1984"

Estimating convective energy losses from solar central receivers

Abstract: This report outlines a method for estimating the total convective energy loss from a receiver of a solar central receiver power plant. Two types of receivers are considered in detail: a cylindrical, external-type receiver and a cavity-type receiver. The method is intended to provide the designer with a tool for estimating the total convective energy loss that is based on current knowledge of convective heat transfer from receivers to the environment and that is adaptable to new information as it becomes available. The current knowledge consists of information from two recent large-scale experiments, as well as information already in the literature. Also outlined is a method for estimating the uncertainty in the convective loss estimates. Sample estimations of the total convective energy loss and the uncertainties in those convective energy loss estimates for the external receiver of the 10 MWe Solar Thermal Central Receiver Plant (Barstow, California) and the cavity receiver of the International Energy Agency Small Solar Power Systems Project (Almeria, Spain) are included in the appendices.

Solar-rapid rail mass transit system

Abstract: A solar-powered rapid transit system is provided, which travels suspended above ground along a horizontal rail, supported by vertical/horizontal supports. The guide rail is basically a parallelogram, with five inner surfaces. It can be configured as either an overhead monorail system, or a birail system. The rail car is attached to and suspended from such rail by power transmission and support shafts, each of which attaches to a wheel box that fits into the horizontal guide rail. Power is transmitted to the wheels in each wheel box from several electric motors by a series of pulleys and belts in a unique configuration. Such wheels then propel the rail car or cars, which can be connected in series, down the rail. Power for electric motors is supplied by rectangular solar panels supported by vertical supports attached to the roof of each rail car, which extend several feet above the rail car and guide rails. Hinges allow the solar panels to pivot in the direction of the sun, to receive optimum sunlight for power generation. Storage batteries mounted atop each rail car would store generated solar power for night operation and periods when optimal sunlight is unavailable. An electronic sensor rod extending from each wheel box to a groove in the inner surface of the rail picks up system control signals and auxiliary power supplied by a municipal power utility from such groove.

Bidirectional control system for energy flow in solar powered flywheel

Abstract: An energy storage system for a spacecraft is provided which employs a solar powered flywheel arrangement including a motor-generator which, in different operating modes, drives the flywheel and is driven thereby. A control circuit, including a threshold comparator, senses the output of a solar energy converter, and when a threshold voltage is exceeded thereby indicating the availability of solar power for the spacecraft loads, activates a speed control loop including the motor-generator so as to accelerate the flywheel to a constant speed and thereby store mechanical energy, while also supplying energy from the solar converter to the loads. Under circumstances where solar energy is not available and thus the threshold voltage is not exceeded, the control circuit deactivates the speed control loop and activates a voltage control loop that provides for operation of the motor as a generator so that mechanical energy from the flywheel is converted into electrical energy for supply to the spacecraft loads.

Solar-powered/fuel-assisted rankine cycle power and cooling system: sensitivity analysis

Abstract: The subject of this analysis is a solar power/cooling system based on a novel hybrid steam Rankine cycle. Steam is generated by the use of solar energy collected at about 100/sup 0/C, and it is then superheated to about 600/sup 0/C in a fossil-fuel-fired superheater. The addition of about 20-26 percent of energy as fuel doubles the power cycle's efficiency as compared to organic fluid Rankine cycles operating at similar collector temperatures. A sensitivity analysis of the system's performance to the size and type of its components was performed by a transient (hourly) computer simulation over the month of August in two representative climatic regions (Washington, D.C. and Phoenix, Ariz.), and led to the description of a system configuration which provides optimal energy performance. The newly designed turbine's predicted efficiency is seen to be essentially invariant with system configuration, and has a monthly average value of about 73 percent.

Solar-Powered/Fuel-Assisted Rankine-Cycle Power and Cooling-System: Simulation Method and Seasonal Performance

Abstract: The subject of this analysis is a solar cooling system based on a novel hybrid steam Rankine cycle. Steam is generated by the use of solar energy collected at about 100/sup 0/C, and it is then superheated to about 600/sup 0/C in a fossil-fuel-fired superheater. The addition of about 20-26 percent of fuel doubles the power cycle's efficiencyas compared to organic Rankine cycles operating at similar collector temperatures. A comprehensive computer program was developed to analyze the operation and performance of the entire power/cooling system. Transient simulation was performed on an hourly basis over a cooling season in two representative climatic regions (Washington, D.C. and Phoenix, Ariz.). One of the conclusions is that the seasonal system COP is 0.82 for the design configuration and that the use of watercooled condensers and flat-plate collectors of higher efficiency increases this value to 1.35.

The Themis Program and the 2500-KW Themis Solar Power Station at Targasonne

Abstract: Following the first oil crisis, the French Agency for Energy Conservation (A.E.E.) setup in 1975, devoted its time and efforts towards saving energy both in industry and in housing. This effort was expanded by our government in 1978, when the French solar energy authority, known as COMES, was created: it concentrated on R and D pertaining to new and renewable energy. Early this year, these two agencies were merged together to create the French Agency for the Management of Energy (FAME), which includes geothermal and heat distribution networks. This decision now gives the French government the tool to implement a very ambitious and diversified program, calling at the same time on energy conservation and on new and renewable energies development. An important part of the R and D program set up by FAME is the thermodynamic conversion program. On one side, the program devotes itself to the development of components and systems, among them the THEK program which deals with parabolic dishes. These could be used not only for heat generation purposes or electricity generation but also in stand alone systems, for example to refrigerate and conserve fish, a useful application in the developing countries. On the other side, themore » program calls for the implementation of pilot plants in order to experiment with these components and thermodynamic cycles. Such a pilot plant is nearing completion near Ajaccio in Corsica, and is due for operation early next year. Partial tests have already been run. It was a distributed collector parabolic trough array and a Rankine cycle turbine.« less

Solar Power for Telecommunications - The Last Decade

Abstract: A decade ago, solar photovoltaics were considered an expensive and exotic alternative, only to be used for a few very specialised applications. Today, solar is seen as a conventional power supply, preferred for most rural and remote communication sites where commercial mains power is unavailable. This paper deals with Telecom Australia's experience with solar power through the years and will discuss the design philosophy used, and where Telecom Australia plans to go in the future in the solar photovoltaic field.

Central Receiver System (CRS) in the Small Solar Power Systems Project (SSPS) of the International Energy Agency (IEA)

Abstract: Attention is given to the design features and performance of the Small Solar Power Systems Project's Central Receiver System (CRS). The heliostat field used has a total reflective surface of 3655 sq m and focuses the irradiated power on an aperture plane of 9.2 sq m atop the tower. The cavity-type receiver is rated at 2840 kW at design conditions, of which 88.3 percent is absorbed by the liquid sodium heat transfer fluid as it is heated from 275 to 530 C. The major part of the CRS's Rankine power conversion cycle is a five-stage steam motor with two preheaters. Attention is given to CRS program funding responsibilities and development milestone chronology.

Model for the economic assessment of solar power plants

Abstract: Economic evaluations of central receiver system plants of 10, 30, and 100 MW and of a distributed collector system plant of 10 MW were performed based on projected data sets. A study on the appropriateness of different calculation methods is included. As cost calculation methods primarily the annuity method and the life cycle costs methods were taken as a basis.

Solar Thermal Power Towers

Abstract: The solar thermal central receiver technology, known as solar power towers, is rapidly evolving to a state of near-term energy availability for electrical power generation and industrial process heat applications. The systems consist of field arrays of heliostat reflectors, a central receiver boiler, short term thermal storage devices, and either turbine-generators or heat exchangers. Fluid temperatures up to 550°C are currently achievable, and technology developments are underway to reach 1100°C. Six solar power towers are now under construction or in test operation in five countries around the world.

Storage temperature of salt-gradient solar pond

Abstract: A solar pond may be used as a large area collector and for the storage of solar energy. The salt-gradient solar pond is a body of saline water in which the concentration increases with depth. This density gradient inhibits thermal convection, with the result that solar radiation reaching the lower region is trapped and the temperature is raised. A method to estimate the storage temperature variation in the pond is described. The storage temperature is estimated by a numerical analysis using meteorological observation data with a time interval of one hour. In this analysis, the following effects are considered: the heat transfer from the pond to the surrounding ground, the change of salt-gradient due to the diffusion of salt, and the local occurrence of thermal convection. The results of the simulation are compared with data obtained by the writer. The study is based on a condition without heat extraction from the pond.

Metal Sulfides in Photovoltaic, Photoelectrochemical and Solar Biological Energy Conversion

Abstract: Crystallized metal compounds of sulfur are gaining increasing importance in various rapidly developing areas of solar energy conversion. One reason is that many metal sulfides form semiconductors with energy gaps well suited for the capture of solar energy. Several photovoltaic and photoelectrochemical solar cells with good energy conversion efficiencies have already been tested using CdS, Cu 2 S, CuInS 2 , MoS 2 and other sulfides. For the photoelectrolysis of water into hydrogen and oxygen semiconducting materials are being developed which permit light-induced hole reactions via valence energy bands derived from transition metal d-states. Sulfur compounds of transition metals (PtS 2 , RuS 2 , Ru 1-x Fe x S 2 ) constitute the first useful materials for oxygen evolution from water using low energy photons. In this case advantage is taken of the favourable property of sulfur as a metal ligand which permits efficient d-d interaction resulting in adequate d-d splitting and reasonably broad d-state energy bands. A third property of metal sulfides interesting for solar energy conversion is their ability to store chemical energy and to serve as an energy source for autotrophic bacteria (Thiobacilli). When metal sulfides are generated from their oxidation products (metal sulfates) by means of solar power using high pressure thermal and photoelectrochemical techniques, they can be used to grow bacterial biomass. Experimental and theoretical studies suggest that such an artificial solar biomass production could be far more energy-efficient than natural photosynthesis, besides of permitting the use of infertile and arid land on which compact and largely automatic installations would generate proteins, carbohydrates and lipids for energy and food with a remarkable economy of water consumption. Several aspects of sulfur chemistry with respect to mechanism of solar energy conversion are still unexplored and deserve detailed investigations.

Hawaii's goal: energy self-sufficiency

Abstract: Hawaii is the state most vulnerable to dislocation in the global energy market, with more than 91% of its total energy coming into the state as imported oil-two thirds of which is foreign crude. This near-total dependence on seaborne petroleum is a paradox, since Hawaii has a wide variety of renewable energy resources which can serve as alternatives to oil. These renewable resources have the potential of being less polluting than conventional energy supplies and so are consistent with Hawaii’s concern for the quality of life. For the past decade Hawaii has been engaged in a comprehensive program of resource assessment, research, development, demonstration, and commercialization of its indigenous energy resources: direct solar, wind, biomass, ocean thermal, geothermal. Sufficient progress has been made to date with a number of these energy alternatives, so that Hawaii should be able to maintain its momentum toward achieving energy self-sufficiency—even in the face of drastic reductions in federal support for renewable energy research, development and demonstration and the present declining cost of oil.

Recent Advances in Design of Low Cost Film Concentrator and Low Pressure Free Piston Stirling Engines for Solar Power

Abstract: The free piston Stirling-linear alternator was shown to be scalable to power levels of tens of kilowatts in a form which is simple, efficient, long lived and relatively inexpensive. It avoids entirely the vexing problem of high pressure shaft, and its control requirements are not severe nor do they represent a significant threat to durability. Linear alternators have demonstrated high efficiency and moderate weight, and are capable of delivering 3 phase power from single machines without great increases of cost or complexity. There remains no apparent impediments to the commercial exploitation of the free piston engine for solar electric power generation.

Design of Direct Solar Floors and Practical Results

Abstract: Classical solar space heating systems by flat collectors exhibit high costs and poor rehiability. A new concept, “DIRECT SOLAR FLOORS” (in abreviate “D.S.F.”) offers a drastic improvement from this condition: it consists merely of a direct coupling of collectors to a classical heating floor, without any external storage. The floor, which ensures simultaneously heat storage, regulation and space heating has to be thicker than usual. We expose the main features of this system, our theoretical modelling and the conclusions for behaviour and rules of sizing for DSF. A practical example is described and measured performances are discussed. D.S.F. appears as a very powerfull space heating system of low cost, high thermal yields and improved reliability.

Stirling Module Development Overview

Abstract: The solar parabolic dish Stirling engine electrically generating module consists of a solar collector coupled to a Stirling engine powered electrical generator. The module is designed to convert solar power to electrical power in parallel with numerous identical units coupled to an electrical utility power grid. The power conversion assembly generates up to 25 kilowatts at 480 volts potential/3 phase/alternating current. Piston rings and seals with gas leakage have not occurred, however, operator failures resulted in two burnt out receivers, while material fatigue resulted in a broken piston rod between the piston rod seal and cap seal.

Test and Modelization of a Greenhouse Using Low Temperature Heating

Abstract: An analyses of measured data taken from a heated greenhouse in Geneva discloses the following results: The installed thermal screens allow a reduction of the energy consumption of 44% during the night. A first simple static model gives a good estimation of the night requirements in agreement with the measurements. Due to the low fraction of solar energy stored in the ground, the nightly heat demand is linearly linked with the outside temperature. On the contrary, during daytime, the solar contribution is important and highly variable, for this reason the above representation is meaningless. However an appropriated representation can be found by plotting the dayly energy consumption against the ratio of the average solar power over the temperature difference between the inside and the outside. This description is the ground work of a simplified method for evaluating the monthly mean consumption of a greenhouse. The measured useable solar energy depends strongly upon the month. On average, the useable solar energy amounts to about 23% of the incident solar energy. Solar gains cover approximately 22% of the total heat losses. Due to protective screens, the influence of the wind is relatively small during the night and slightly stronger during the day.

Communal Solar Photovoltaic Systems for Rural Areas

Abstract: Small photovoltaic solar power systems were introduced for the first time in rural Egypt in the small village of Basaisa, Al-Sharkiya Governorate, on November 4th 1977. The systems and their application in such a small rural community are discussed in relation to rural energy, PV system technology, reliability, operation and maintenance, initial cost, people's participation and response and the social impact. Solar powered communal TV set, few audiovisuals, emergency light, and irrigation pumps are in satisfactory operation at the village. Other systems are planned. It was found necessary to develop micro-organizations at the village level; a sort of energy cooperative to: a) manage the new technologies introduced and sustain the on-going activities based on them, b) integrate the different activities for a positive and comprehensive development, c) generate funds needed to maintain, repair, and replace, if necessary, the systems in use. Based on about 5 years of field experience, one can conclude that such small communal solar photovoltaic systems provide a realistic energy option for small villages, not only in Egypt, but also in similar rural communities elsewhere.