Showing papers on "Solar power published in 1994"

Integration of Distributed Generation in the Power System

Abstract: Distributed Generation (DG) reduces the amount of energy lost in transmitting electricity because the electricity is generated very near where it is used. This book introduces systematic and transparent methods for quantifying the impact of DG on the power grid. It emphasizes systematic and transparent calculation methods, allowing for a quantification of the amount of DG that can be integrated at a certain location of the grid or in the grid as a whole. It also provides an overview of the different energy sources, with emphasis on wind power, solar power and combined heat and power in the power grid.

Maximum power point tracking for low power photovoltaic solar panels

Abstract: A maximum power point tracker unit is developed for the optimum coupling of photovoltaic panels (PVP) to the batteries and load through a controlled DC-DC power converter (chopper). The system consists of three main units: (i) the photovoltaic panels that convert solar power to electricity; (ii) a chopper which couples the power of PVP to the load or batteries at a constant voltage; and (iii) maximum power point (MPP) computing unit that determines the set point of the chopper to keep the panel voltage at a maximum power transfer (MPT) condition. The tracking of the MPP for low power PVP (50 W-1 kW) is feasible only when the power consumption of the tracking unit is lower than the increase of the output power that they provide. The developed and tested circuit consumes only 40 mW, and therefore is suitable even for low power applications down to 50 W. The tracking unit performs MPP computation periodically through analog computing stages. The computation mode requires 20 mA from the /spl plusmn/5 V source for a 50 ms period. In the control and sleep mode, the consumption falls down to 4 mA. The developed unit regulates the panel output voltage at its optimum value in the control mode. The modes are switched by a timing circuit. The sleep mode is initiated when maximum PVP output power of the existent illumination level drops to a preset value, which cannot balance the losses of the chopper and the consumption of the MPP tracker unit. >

Renewable energy : economic and environmental issues

Abstract: This article analyzes the potential of various renewable or solar energy technologies to supply the United States with its future energy needs. Diverse renewable technologies are assessed in terms of their land requirements, environmental benefits and risks, economic costs, and a comparison of their advantages. In addition a projection of the amount of energy that could be supplied by solar energy is made. Topics covered include: assessment of renewable energy technologies; biomass energy systems; liquid fuels; ethanol; methanol; hydrogen; hydroelectric systems; wind power; photovoltaics; solar thermal conversion systems; passive heating and cooling of buildings; comparing solar power to coal and nuclear power; transition to solar energy and other alternatives. 84 refs.

Solar-gas combined cycle electrical generating system

Abstract: A design of a power plant which uses hydrocarbon fuels in conjunction with solar power to produce electricity. The power plant consists of an array of heliostats for concentrating sunlight on a central solar receiver. The heat energy thus gathered is used to create steam which runs a steam turbine. Steam to run the steam turbine can alternately or modularly be obtained from the exhaust gas of a turbo-burner and fuel added to a furnace. The solar energy gathered may be stored as hot fluid in a thermal storage tank or used immediately in the power plant. A thermal shield may be employed over the solar central receiver to insulate the solar central receiver, provide leak and fire protection and shield the solar central receiver from solar radiation.

A new PWM inverter for photovoltaic power generation system

Abstract: In this paper, the authors propose a novel multi-step PWM inverter for a solar power generation system. The circuit configuration is constructed by adding a bi-directional switch to the conventional bridge type inverter circuit using the isolated DC power supply for which the solar cell is very suitable. The new type of PWM inverter presented has many features such as good output waveform, small size of filter, low switching losses, and low acoustic noise. In this paper the authors describe the circuit configuration, control method and the characteristics of the system, and they also investigate the relation between the inverter and the solar cell characteristics. Finally, some simulation results and experimental results are shown. >

Method of manufacturing high efficiency, broad bandwidth, volume holographic elements and solar concentrators for use therewith

Abstract: An improved method of manufacturing holographic elements for solar concentrator, which is a necessity for the future of viable low cost solar power. Utilizing extremely high relative humidity levels during the fabrication of holographic plates, exposing the holographic plate to electromagnetic radiation at particular humidity levels, and having a relative angle between recording beams during exposure makes it possible to fabricate high efficiency holographic elements that diffract over a broad bandwidth. These high efficiency, broad bandwidth holographic elements are most effective in certain solar concentrating systems.

Solar energy : lessons from the Pacific Island experience

Abstract: The successful experience of the Pacific islands in using and maintaining solar photovoltaic systems (PV) indicates that such systems could come to play a substantial role in the electrification of rural areas in many developing countries In particular, the Pacific island experience suggests that present-technology household-sized PV systems can provide reliable power at costs less than those of the more commonly used diesel systems in small, remote villages for consumers with a limited number of appliances It also suggests that the long-term success of solar PV programs will depend on the establishment of effective institutional approaches for maintaining the systems, and it indicates that ownership and maintenance of the systems by utilities appears to be the soundest option In the Pacific islands, solar PV programs encountered a variety of difficulties in their early phases Most of the early systems suffered from technical deficiencies - stemming primarily from unreliable controllers, batteries, and appliances rather than the PV panels themselves The lesson drawn is that systems must be appropriately designed, use reliable even if initially high-cost components, and be properly installed and adequately maintained Tuvalu provides a case study illustrating the potential effectiveness of solar PV systems in remote areas for rural electrification under appropriate institutional arrangements A comparison of solar PV and diesel systems on the basis of life-cycle costs of providing the final services that the customer desires for a number of years shows that the life-cycle costs of solar PV systems are marginally lower than those of diesel systems for households in remote rural areas The difference in overall costs is about 1 to 14 percent, with the higher savings applicable to households with low energy consumption and lower savings applicable to households with higher energy consumption

Wireless solar entertainment system

Abstract: This invention comprises a consumer electronics entertainment system with a transmitter and a wireless headphone receiver with matching frequency reception. It is particularly adapted for use by joggers, runners, walkers picnickers, sunbathers or other mobile users. The invention entails a transmission integrated solar powered cassette radio or CD ROM player or other portable consumer electronics entertainment device with a built in low range low power transmitter and wireless headphones that also operate on solar power with automatically solar charged back up battery that never needs replacement.

Solar powered pumping system

Abstract: A solar water pumping system for home use utilizing amorphous solar panels and circuitry for maintaining proper power to the system. Three reference voltages in combination with switching circuitry achieve this purpose by constantly monitoring input and output voltages and allowing a non-discontinuous switching between solar power and battery power.

Viking 23-zero emissions in the city, range and performance on the freeway

Abstract: The design team for Viking 23 decided that a solar electric, parallel hybrid vehicle would be a realistic replacement for today's car. A range of up to 100 Km at an average urban speed of 50 kph in zero emission mode was set as a goal. An attempt will be made to do this with no power drawn from the existing electric power grid by utilizing solar cells to charge the battery. For inter-city use a target range of 500 km at an average speed of 100 kph was set. The parallel configuration was chosen because mechanical drive-line efficiency is greater than that possible for a series hybrid. One disadvantage of a parallel hybrid is that a larger more powerful internal combustion (IC) engine is required for hill climbing and maximum performance than would be needed for the series configuration. On the other hand, no large generator is needed to collect the IC engine power to charge the battery and run the electric motors.

Diagnostic system for solar cell

Abstract: PURPOSE: To obtain a diagnostic system for solar cell in which a solar power generation system can be diagnosed and recovered from failure instantly while reducing the amount of maintenance work at the time of maintenance/inspection on the maintenance company side and lowering of power generation due to a shade can be grasped on the user side along with the failure of unit solar cell part (module, cell) and a countermeasure can be taken immediately. CONSTITUTION: The diagnostic system for solar cell comprises solar cell arrays 8 in a solar power generation system, a pilot module M-1 different from the solar cell array 8, and a diagnostic section 37 for producing an output characteristic curve model of the solar cell array 8 from the output characteristic curve of the pilot module M-1 and comparing the output characteristic curve model with the output characteristic curve of the solar cell array 8 to diagnose abnormality of the solar array 8.

A photovoltaic maximum power tracking using neural networks

Abstract: The paper presents laboratory implementation of a photovoltaic artificial neural network (ANN) based maximum power tracking controller. The control objective is to track the maximum available solar power in a photovoltaic array interfaced to an electric utility grid via a line-commutated inverter. The inverse dynamic characteristics of this interface scheme is identified via off-line training using a multi-layer perceptron type neural network. The ANN output is used as the control signal to vary the line-commutated inverter firing control angle, hence track the available maximum solar power. The weights of the ANN are also updated by a novel on-line training algorithm which utilizes the on-line power mismatch error. This ensures on-line maximum solar power tracking. The proposed controller is compared with a well tuned conventional proportional plus integral controller to validate its effectiveness. >

Environmental durability issues for solar power systems in low earth orbit

Abstract: Space solar power systems for use in the low Earth orbit (LEO) environment experience a variety of harsh environmental conditions. Materials used for solar power generation in LEO need to be durable to environmental threats such as atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeoroid and debris impact. Another threat to LEO solar power performance is due to contamination from other spacecraft components. This paper gives an overview of these LEO environmental issues as they relate to space solar power system materials. Issues addressed include atomic oxygen erosion of organic materials, atomic oxygen undercutting of protective coatings, UV darkening of ceramics, UV embrittlement of Teflon, effects of thermal cycling on organic composites, and contamination due to silicone and organic materials. Specific examples of samples from the Long Duration Exposure Facility (LDEF) and materials returned from the first servicing mission of the Hubble Space Telescope (HST) are presented. Issues concerning ground laboratory facilities which simulate the LEO environment are discussed along with ground-to-space correlation issues.

Solar energy answer to rural power in Africa

Abstract: In Kenya, more rural households get their electricity from solar energy than through the Government's rural electrification program. The spread of the photovoltaic systems has been recent, rapid and market driven. The author looks at the economics of this thriving market.

Applications of Brayton cycle technology to space power

Abstract: The Closed Brayton Cycle (CBC) power conversion cycle can be used with a wide range of heat sources for space power applications. These heat sources include solar concentrator, radioisotope, and reactor. With a solar concentrator, a solar dynamic ground demonstration test using existing Brayton components is being assembled for testing at NASA Lewis Research Center (LeRC). This 2-kWe system has a turbine inlet temperature of 1015 K and is a complete end-to-end simulation of the Space Station Freedom solar dynamic design. With a radioisotope heat source, a 1-kWe Dynamic Isotope Power System (DIPS) is under development using an existing turboalternator compressor (TAC) for testing at the same NASA-LeRC facility. This DIPS unit is being developed as a replacement to Radioisotopic Thermoelectric Generators (RTGs) to conserve the Pu-238 supply for interplanetary exploration. With a reactor heat source, many studies have been performed coupling the SP-100 reactor with a Brayton power conversion cycle. Applications for this reactor/CBC system include global communications satellites and electric propulsion for interplanetary exploration. applications. The CBC consists of a heater, turboalternator compressor (TAC), cooler, and recuperator. A mixture of He and Xe is used as the working fluid in the CBC system. The He provides superior heat transfer characteristics in the heater, cooler, and recuperator. The Xe adjusts the molecular weight to provide superior aerodynamic performance for maximized turbine and compressor efficiency. Cycle studies are performed to select the optimum He/Xe molecular weight or He to Xe mixture ratio. The following presents the characteristics and advantages of using the CBC for space power applications, CBC development status, characteristics and applications of the CBC with each of the heat sources, and finally performance projections. >

Solar power generator using cooled photovoltaic modules

Abstract: The generator includes a solar energy collection system with a curved mirror (10) that is positioned to receive the rays of the sun (11). A solar energy cell (13) is positioned at the focal point of the mirror. Angled reflector panels (22) project from the cell and direct the rays within the range of the mirror. The solar energy cell is filled (16) with a cooling fluid that is circulated by a pump (21) through a tank (20).

Solar powered water pumping station for use in remote locations such as semi-arid zones

Abstract: The pumping station (1) driven by solar power comprises photovoltaic panels (2) to transform solar energy into direct current, at least one pump (3) driven by an AC motor (4) and an inverter (5) converting the direct current from the photovoltaic panels to alternating current for the motor. The station also includes a controller (8) to quantify and record parameters representing the station usage. This controller stops the inverter and therefore the motor when these parameters meet certain criteria. The inverter, directly connected to the photovoltaic panels and the controller, stops when there is any storage or transformation of electrical energy. The controller measures parameters chosen from the flow rate of the pump(s), the water pressure in the pipes, the amount of sunshine and the temperature. It contains a sub-assembly which records events and the measured parameters to ease maintenance and to establish a history of the station's operation. The controller is fed electricity directly from the photovoltaic panels and is integrated with the electronics regulating the inverter. Credit allocated for using the station is a function of the length of operation of the station or of the amount of water pump. The inverter is controlled by transfer of given parameters between an external device (10) and the controller. This external device is an information terminal from a maintenance agent or a telecommunications system.

Roof material for solar power generation and its work execution method

Abstract: PURPOSE: To facilitate laying-wiring work or the like by sticking a light shielding material having a recess-projection surface to a surface of a power generation effective part of a roof material for solar power generation. CONSTITUTION: A solar roofing 1 is provided with a superposing marging part 12 in the width direction of a base material and a power generation effective part 11 composed of solar tiles, and in the power generation effective part 11, the plural solar tiles 3 having a photoelectric transfer function are juxtaposed on a roofing base material 2, and are covered with a surface protective material 4 after electric wiring is performed between them, and are formed in an integral sheet shape by passing these through a heated roller. It is smoothed by using a copolymer film or the like as the surface protective material 4, and a light shilding film 5 is separably stuck to a part existing on the power generation effective part 11 among this surface, and its surface is formed as a recess-projection surface 51 by embossing finish. A light shilding material stuck to a surface of the power generation effective part checks power generation of a photoelectric transfer element in solar roofing installing work, and protects an operator from an electric shock, and a recess-projection on a surface secures a scaffold of the operator.

Inverter and solar power generation system using it

Abstract: PURPOSE: To reduce harmonic noise (distortion) produced when an inverter outputs a small current and, at the same time, to reduce the loss of the inverter or low-order harmonic distortion produced when the inverter outputs a large current. CONSTITUTION: In an inverter 2-5 which converts input DC power Vdcldc into output AC power VacIac and supplies the AC power VacIac to a load 7, the reactance of an output low-pass filter 5 is changed in accordance with the output current Iac of a power converter. COPYRIGHT: (C)1996,JPO

Solar power generating device and power generating method

Abstract: PURPOSE: To store energy with a simple facility by converting sunlight energy into electric energy with a solar battery, driving a compressor with a motor, storing compressed air in a pressure tank, and again converting the pressure energy into electric energy with a turbine and a power generator CONSTITUTION: Sunlight energy is converted into electric energy by a solar battery 2, the obtained DC current is rectified and voltage-controlled by a thyristor 3 and a capacitor 4, and it is converted into the AC output by an inverter 5 and fed to a motor 6 A compressor 7 is driven by the motor 6 to generate compressed air, and the compressed air is stored in a pressure tank 8 as pressure energy The compressed air is taken out as required to drive a turbine 9, and electric power is generated by a power generator 10 operated by the turbine 9 The obtained electric power is fed to a power controller 11, and the power generation capacity of the power generator 10 is adjusted by the power controller 11 COPYRIGHT: (C)1995,JPO

Optical Waveguide Solar Energy System for Lunar Material Processing

Abstract: This paper summarizes a study of the optical waveguide (OW) solar energy system for lunar material processing. In the OW solar energy system, solar radiation is collected by the concentrator and transferred to an OW transmission line consisting of low-loss optical fibers and related optical components. The OW line transmits the high intensity solar radiation to the thermal reactor of the lunar material processing plant. Based on the results discussed in this paper we conclude that the OW solar energy system is a viable concept which can effectively utilize solar energy for lunar material processing.

Solar energy mapping by using cloud images received from GMS

Abstract: Solar energy maps that indicate the wide-ranging spatial distribution of solar irradiation are required by the researchers of the solar power systems. However, the irradiation measurement networks at ground level are not enough to obtain reliable information of the solar energy distribution in the world. On the other hand, geostationary meteorological satellites (GMS) have provided the images of cloud fields over the whole surface of the Earth. The main cause of an irregular change in the irradiation at the ground level is effect of the clouds; therefore, methods for estimating the irradiation by using the GMS images may be very useful. The solar irradiation for 14 sites in Japan was estimated by a semi-physical model developed by the authors. The RMS errors, averaged over 14 stations, were 0.0804 kWh/m/sup 2/ for hourly estimates, 0.534 kWh/m/sup 2/ for daily estimates and 7.14 kWh/m/sup 2/ for monthly estimates. There were little regional differences of estimate accuracy. An example of solar energy maps for Eastern Asia in 1992 is presented.

Co-generation system

Abstract: PURPOSE: To utilize energy from the standpoint of both the user and supplier of the energy effectively by combining three kinds of power sources, namely, the commercial power supply system, solar power generation and a generator using fuel, and using the power sources. CONSTITUTION: If the power load 15 the amount of generated power of solar power generator 1 and if thermal load 17 the amount of power the solar power generator 1, and thermal load 17 >= the amount of discharged heat recovered from the generator 3 when the powers of the solar power generator 1 and the generator 3 are supplied, the power generated in the generator 3 and the power generated in the solar power generator 1 are supplied to the power load.

Power from space -- can it compete?

Abstract: The world faces a serious energy problem. Two major aspects are: 1) current energy practices are damaging to the environment of the earth, and 2) the provision of energy to the Developing Countries in inadequate for effective economic development. The implementation of renewable energy resources, including the importation of solar power from space, can help relieve the first of these situations. However, the adoption of such sources wille, if present trends continue, not take plade rapidly enough to avert significant further environmental damage. A useful step to spur the adoption of such sources would be the inclusion in energy pricing of the costs of external and environmental effects. Such an inclusion would reflect the environmental-friendly nature of renewable sources as compared with lost other sources. The credibility of economical importation of solar energy from space has improved in recent years because of advances in the efficiency of photovoltaic cells and in the capacity to manufacture such cells. However, the viability of power importation is strongly dependent on the costs of transport to orbit. When such costs have been substantially reduced, power importation from space will initially serve niche markets where the current cost of energy is high. Wide-scale implementation could, in time, aid the needs of the Developing Countries where energy prices are high and relatively few choices are available

Energetischer Vergleich von Kraftwerken

Abstract: Cumulated energy expenditures are determined for two non-regenerative and for three regenerative power station types and are used for the calculation of energetic characteristic values harvest factor and amortization time, as well as a quality factor in respect of the CO 2 -production. The results indicate ― despite partly very provisional figures ― clear advantages of the «established» coal and nuclear power stations compared to all the other investigated power station types. Wind power stations and solar collectors for hot-water supply'are in a kind of intermediate position, whilst photo-voltaic solar power stations (based on mono-crystalline silicon cells) end up by far the worst