Showing papers on "Solar power published in 1988"

Modeling and simulation of spacecraft power systems

Abstract: Modeling of a complete spacecraft power processing system is presented, using the Boeing EASYS software. Component models are developed, and several system models including a solar array switching system, a partially shunted solar system, and cosmic background explorer (COBE) system are simulated. The modes of operation of the power system, such as shunt mode, battery-charge mode, and battery-discharge mode, are simulated for a complete orbit cycle. >

Method and apparatus for powering electrical and electronic consuming devices with solar energy

Abstract: In order to provide the required electric power uninterruptedly to an electrical or electronic consuming device (M) powered by solar cells (1, 2, 3, 4), the supply of power to the consuming device must be assured even under inadequate illumination conditions and/or during brief failures of the solar collector (S), an electronic system is proposed wherein a control circuit (RK) is provided between the solar collector (S), the consuming device (M), and an electrical energy storage device (C1). The control circuit (RK) functions at least as a connecting and commutating switching device which, subject to the priority of maintaining the operational readiness of the consuming device (M); provides various interconnections of the solar collector (S), the storage device (C1), and the consuming device (M). The control circuit (RK) makes these various connections in dependence on (1) the voltage (U S ) at the solar collector (S), (2) the voltage (U M ) required for operation of the consuming device (M), and (3) the state of charge of the storage device (C1). In this way, it is possible to maintain desired conditions (i.e., operation of the consuming device) during brief failures of the solar collector (S) when the illumination is inadequate. At the same time a situation can be avoided wherein the consuming device (M) can only receive adequate electric power after the capacitor (C1) has been charged to the specified operating voltage (U M ) of the consuming device by the solar collector (S). Thus, the invention makes it possible to avoid the drawbacks of previously known solar power delivery circuits and at the same time enables optimum utilization of the incident light as an energy source for electrical consuming devices.

Output power and efficiency upper bound of real solar heat engines

Abstract: SYNOPSIS Maximum power and efficiency at the maximum power of an irreversible solar heat engine are treated. When time is explicitly considered in the energy exchanges between the solar heat engine and its surroundings, it is found that there is a bound on the efficiency of the real solar heat engine at the maximum power condition. This bound can guide the evaluation of existing solar power generating systems or influence design of future solar heat engines.

Power systems for production, construction, life support, and operations in space

Abstract: As one looks to man's future in space it becomes obvious that unprecedented amounts of power are required for the exploration, colonization, and exploitation of space. Activities envisioned include interplanetary travel and LEO to GEO transport using electric propulsion, Earth and lunar observatories, advance space stations, free-flying manufacturing platforms, communications platforms, and eventually evolutionary lunar and Mars bases. These latter bases would start as camps with modest power requirements (kWes) and evolve to large bases as manufacturing, food production, and life support materials are developed from lunar raw materials. These latter activities require very robust power supplies (MWes). The advanced power system technologies being pursued by NASA to fulfill these future needs are described. Technologies discussed will include nuclear, photovoltaic, and solar dynamic space power systems, including energy storage, power conditioning, power transmission, and thermal management. The state-of-the-art and gains to be made by technology advancements will be discussed. Mission requirements for a variety of applications (LEO, GEO, lunar, and Martian) will be treated, and data for power systems ranging from a few kilowatts to megawatt power systems will be represented. In addition the space power technologies being initiated under NASA's new Civilian Space Technology Initiative (CSTI) and Space Leadership Planning Group Activities will be discussed.

Solar seating bench

Abstract: A bench with a warmed-up seat and back has always been the wish of many people. In the invention of the solar seating bench, a seat has been provided which constantly releases heat and thus offers man and animal a place to rest. The solar seating bench can 1a. be warmed by the sun's rays or b. be heated by daylight using solar power, 2. be supplied with heat by connection to the electrical network. Re 1a The seat and back consist of high-grade steel sheet. By means of the sun's rays, heating up takes place. The heat is stored by a water-filled plastic container situated directly below the high-grade steel sheet. 1b If no insolation takes place, an electric current is generated by means of a solar module situated above the back. The current is stored in a solar battery and released to the seat. 3. If the energy from 1a and 1b does not suffice to warm the seat, the current can be drawn from the network. With the solar seating bench, an ideal place to sit, constantly giving off the required heat in summer as well as winter, has been created.

Design of a solar power satellite for construction from lunar materials

Abstract: Conception d'un satellite-centrale solaire en materiaux solaires. Demonstration en laboratoire des techniques de traitement chimique necessaires a l'obtention des materiaux de construction a partir du sol lunaire ainsi que de la catapulte electromagnetique. Cette conception ne necessite que 1% de masse provenant de la Terre

A study of the reliability of Stirling engines for distributed receiver systems

Abstract: The objective of this study was to examine the reliability of existing and improved Stirling engine concepts for dispersed solar dish/electric applications in the 25--50 kW/sub e/ range. Five current kinematic Stirling engine designs have the capability to meet or exceed the 32% system efficiency goal of the DOE Solar Thermal Program. Experience with the Vanguard Solar-Dish/Stirling Engine module demonstrated that the 32% efficiency goal is realistic, but that improved Stirling engine reliability is necessary for successful implementation of dispersed solar power systems. A review of historical Stirling engine data illustrated that the three major reliability issues with kinematic Stirling engines are the piston-rod seals, engine hot parts and power control/drive systems. A specific kinematic engine concept that appears to have the potential for meeting the 50,000-hour operating lifetime requirement of solar power systems has a pressurized crankcase to reduce piston-rod seal problems, an indirectly heated hot-end section using heat pipes to smooth out temperature gradients in the heater tubes, and a variable-angle swashplate for power control. Further development efforts are required to establish reliability and validate performance goals of these engine concepts. 30 refs., 13 figs., 8 tabs.

Fan arrangement for battery and solar operation

Abstract: Fan arrangement for vehicles, which can be operated optionally with DC voltage from the on-board battery or with solar power from a solar panel arranged on or in the vehicle, with a fan motor designed for battery operation, with a fan wheel adapted to the fan motor in terms of power and with an air-guide system installed in a fixed manner. Arranged in the region of the fan wheel is a further supplementary motor designed for solar operation, the torque-delivering shaft ends of the two motors are coaxially opposite one another at a small spacing, the fan wheel is mounted rotatably on both shaft ends, and arranged between the fan wheel and the shaft ends is in each case a free-wheeling clutch which connects the motor driving at the time to the fan wheel in a rotationally fixed manner.

Power to the outback (remote-area power generation)

Abstract: Continuous electricity supply for people in remote areas has always presented a problem. This has certainly been the case in the geographically diverse continent of Australia, where central grid electricity supply to all consumers is economically impossible. The author shows that the alternative source of electricity is small-scale private generation. He demonstrates that, with capital costs falling, remote power generation is progressing beyond the traditional unsupported diesel set, with renewable sources (including solar, wind and hydroelectric power) becoming economically viable. >

Thermal storage systems - present status and trends

Abstract: Recent progress in solar thermal storage developments and applications is made evident by the presentation of various modern projects: central solar heating plants with seasonal storage, high temperature heat storage with composite (phase changing) materials, long term energy storage via heterogeneous (condensed state - gas) chemical reactions. Storage performance is setting bounds to the solar multiple which is an essential design parameter for the operation economics of solar power plants. The storage multiple which pays attention to the persistencies of unfavorable solar weather conditions is found to be an important design parameter.

Heat transfer modeling of the IEA/SSPS (International Energy Agency/Small Solar Power Systems) volumetric receiver

Abstract: A wire-pack volumetric receiver was tested in 1987 in Almeria, Spain, by the International Energy Agency/Small Solar Power Systems (IEA/SSPS). Although the experiment goal was strictly proof-of-concept and was not receiver characterization, modeling efforts were initiated to help understand the experimental results. The steady-state performance and comparisons to experimental data are presented. The model allows an absorber design to be thermally characterized and optimized based on solar energy transfer characteristics and temperature distributions in the receiver. Model predictions of receiver power and efficiency are generally higher than the test results (operational modifications are believed to have produced nonideal conditions), but trends are consistent with experimental data. 12 refs., 5 figs.

Data from the Sun

Abstract: The authors plan to implement an insolation data collection system in connection with a solar-energy research program of a local electric utility company. The system will be implemented in two independent parts. The hardware for the first part will consist of an IBM PC-compatible microcomputer equipped with a Metrabyte Dash-16 data acquisition system. The data acquisition hardware will be connected to five pyranometers. The five collection stations will be placed so as to simulate an actual solar power panel. The desired end-product of this data is the effect of cloud cover on solar power generation systems. The second part of the project begins by designing solar-energy data collection units, four of which will be located throughout Kansas. The data will be used to evaluate the various locations' potentials with respect to solar power production. >

Studies on solar powered 3 phase MOSFET inverter

Abstract: The authors describe the developmental studies of a MOSFET-based three-phase inverter, operating from a 400 W photovoltaic power source. Many different drive circuits were tested and their limitations were studied. A three-phase MOSFET inverter was built and tested with an induction motor pump as a load. The inverter uses a pulsewidth-modulation technique to minimize the harmonic contents of the output waveform. A special purpose IC, HEF 4752, is used as a controller. The problem of obtaining a simple power supply for the electronic circuit is discussed, as the system operates from a 165 V (at an open-circuit voltage of 200 V) solar power source (without batteries). >

Photovoltaic power systems for ultra low volume pesticide applicators in tropical agriculture

Abstract: The use of solar power with rechargeable nickel cadmium batteries offers a cost effective solution to the problems of pesticide applicator power supply. With the advent of low cost amorphous silicon photovoltaics, both battery pack and charger can be obtained at costs commensurate with the capital costs of ultra low volume (ULV) applicators. This paper examines the historical development of ULV sprayers and the economics of power sources. Options for the practical use of solar rechargers and the preliminary results of field trials are presented.

Preliminary assessment of combined thermal photochemical processes for solar fuel production and solar energy storage

Abstract: A comparison of systems using combined thermal/photochemical processes versus thermal and photochemical systems is presented. Two methods using solar power through combined thermal/photochemical processes are also presented: (1) the equilibrium NO 2 ⇌ NO + 1/2 O 2 driven photolitically and/or thermally to the right side; and (2) the Cl 2 /Ag cycle for water splitting. Theoretical efficiencies of both processes are calculated based on available data. Results of this preliminary study are: • Potentially, high interest exists in developing systems using both direct and diffuse sunlight components in combined thermal/photochemical processes: these systems could reduce solar facility storage requirements, thus improving annual availability. • Theoretical round-trip solar/thermal efficiency of the NO 2 /NO,O 2 system based on global radiation (direct+diffuse) is ≥ 27%; higher than that of a CRS or DCS (24% and 14%, respectively) on the same basis. • The Cl 2 /Ag thermal/photochemical water splitting cycle at T=340°C shows a theoretical conversion efficiency solar/equivalent H 2 energy 16% higher than hydrogen photo-production methods at ambient temperature (1-3%) (Borgarello, 1986). The following conclusions can be drawn from this preliminary assessment: • Use of combined photochemical/thermal process is potentially interesting in solar power use where radiation could be split out. • The proposed system seems interesting due to its potential to improve solar power efficiency. Nevertheless, experimental studies are required to determine their real feasibility, reliability, and efficiency in different operative modes and at the same time determine the safety, toxicity, and induced absorption problems which may arise. • The NO 2 /NO,O 2 system (≥27% overall yearly efficiency based on global radiation) could use diffuse radiation. This could reduce solar facility storage requirements, and improve the overall plant availability.