Showing papers on "Solar power published in 1975"

Efficient CuInSe2/CdS solar cells

Abstract: We report the preparation of a CuInSe2/CdS heterojunction solar cell having a solar power conversion efficiency of 12% measured on a clear day in New Jersey (∼92‐mW/cm2 solar intensity).

p−InP/n−CdS solar cells and photovoltaic detectors

Abstract: We have prepared p−InP/n−CdS heterodiode photovoltaic detectors with a uniform quantum efficiency of ∼70% for wavelengths between 550 and 910 nm. On a cloudy day in New Jersey, (53 mW/cm2) solar power conversion efficiencies of 12.5% have been measured on cells provided with antireflection coatings.

Space Colonies and Energy Supply to the Earth

Abstract: It is pointed out that a space manufacturing facility may be economically more effective than alternative industries on the earth for the construction of products which are to be used in geosynchronous or higher orbits. The suggestion is made to construct solar power stations at a space colony and relocate them in geosynchronous orbit to supply energy to the earth. Attention is given to energy problems and approaches for solving them, taking into account environmental effects and economic factors. Economic aspects of space manufacturing are discussed in some detail.

Orbiting solar power station

Abstract: The invention described herein is an orbiting solar powered, energy collecting, storage and transmitting station. Initially, a large array of solar cells collects and transforms radiant solar energy into moderate amounts of electrical current. This electrical current is fed into a large superconducting coil where it is gradually built up to very high values. The electrical energy is thereby converted and stored in the resulting magnetic field. This magnetic energy is extracted by drawing off the current at very high rates and used to energize a laser or microwave generator for wireless power transmission. Since the discharge of the superconducting coil can proceed at rates many times greater than the charging rate, the resulting beamed power can, over short time intervals, be many times greater than the rate of solar radiation falling on the solar array. Alternatively, the energy can be stored gradually in rotating flywheels for fast rate beaming.

Integrated Power/Attitude Control System (IPACS)

Abstract: An integrated power and attitude control system (IPACS) for spacecraft is described. The system utilizes energy wheels for electrical energy storage as well as attitude control. Results from the feasibility studies of this concept are summarized and indicate potential weight and cost savings up to 30% over conventional power and control systems. The IP ACS advantage is particularly significant for the longer duration missions which have a large number of energy charge-discharge cycles and higher power requirements. A system for a shuttle-launched Research and Applications Module (RAM) free-flying observatory spacecraft is described. The system utilizes three gimbaled, control, and energy-momentum gyros in a planar array. Each gyro unit is rated at 2.4 kw and delivers 1095 w-hr of energy while maintaining control angular momentum above 1115 N-m-sec. Dynamic response of combined power and control functions was evaluated by digital simulations which included significant nonlinearities and a symmetrical energy distribution law. Simulation data indicate that spacecraft attitude control response is similar to that achieved without the superposition of energy wheel speed changes and is essentially uncoupled from that of the faster power control loop. Both power and control dynamics are well regulated. A NUMBER of spacecraft designs have been develxmoped for the missions of the shuttle era. Most of these require subsystems with lifetimes of 5-7 yr to meet cost effectiveness goals. Pointing requirements below 0.25° are common, with specific scientific missions requiring experiment pointing to 1 arc sec. Momentum storage devices normally are used to provide control torques for long-life missions where control thruster propellant weights and valve life test costs prove excessive. The choice of momentum storage is reinforced, or even required, in several missions where mass expulsion contaminants are prohibited by experiment viewing requirements or where fine pointing stability and slewing is required. The significant impact of the long-life requirement on the electrical power system design is in the sizing of components rather than in the type of system selected. This is because nearly all systems postulated utilize solar arrays for electrical power generation and secondary batteries for electrochemical energy storage. The batteries prove to be the heaviest components of advanced spacecraft solar power systems. The weight of the batteries is determined by the rated energy densities and their inherent characteristic of decreasing life with increased depth-of-discharge and charge-discharge rate. Thus, for a specific energy storage requirement, the designer's major option for increasing battery life is that of increasing the size or number of battery cells thereby decreasing the depth of discharge. As a result, batteries and their controllers commonly constitute 30-40% of an electrical power system weight. Developments of recent years1'2 have shown that flywheels designed to store energy can provide higher energy densities than can be expected from several conventional spacecraft electrochemical devices. In spacecraft applications, parity in energy density between the energy wheel and battery subsystems may result in significant advantage to the energy wheel system. This is because many spacecraft designs currently employ flywheels in momentum storage attitude control systems which approximate the weight of energy wheels.

Solar Power via Satellite

Abstract: The possibilities for using satellite solar power stations for large-scale power generation on earth, converting solar energy into microwave energy, transmitting it to the earth’s surface, and transforming it into electricity have recently been explored. The current state of technology and the necessary developments for accomplishing the four functions, i.e., collection of solar energy, conversion to and transmission of microwaves and rectification to DC on the ground, are reviewed. The requirements for flight control, earth-to-orbit transportation, and orbital assembly are discussed. Environmental issues, including impact of waste heat release, water injection into the upper atmosphere by space vehicle exhaust, noise pollution, and location of antenna sites are listed. Biological effects and radio frequency interference are explored. The time frame for accomplishing the operational system is outlined.

Solar energy: the physics of the greenhouse effect.

Abstract: For practical reasons, it is likely that low-temperature solar collectors have a more immediate future than high-temperature or photovoltaic generation of electricity. This paper discusses the physics of bare and covered flat-plate collectors. The greenhouse effect is the result of reducing convection to the point that radiation trapping becomes important. Nevertheless, at collector temperatures within 20-30 degrees C of ambient, convection from the collector surface is so important that a special absorber with low ir emissivity may be no more efficient than a good, black absorber. At higher temperatures, selective absorbers are desirable. In the low temperature range, collection efficiency can be kept well over 80%, but falls rapidly with increasing collector temperature. This suggests that solar power may see early application in conjunction with heat pumps for heating and air conditioning.

Geosynchronous satellite solar power

Abstract: Since a solar array in space will receive up to 15 times as much solar energy as the same array on the ground, it is advantageous to consider geosynchronous orbital solar power plants. Two designs are considered, with cost estimates and transportation considerations. One is a large photovoltaic solar array and the other is a large solar thermal power plant using paraboloidal concentrators, a Brayton cycle engine and a turbogenerator (the efficiency of this system is calculated at 36 percent, which is considerably higher than that of the solar cell array). The power is transmitted to an earth rectenna station by microwave transmission. Various design, power transmission, transportation, surviving, control, and possible, but unlikely, health hazard details are given. Projected possible power stations and cost schedules are included. (LTN)

A theory of concentrators of solar energy on a central receiver for electric power generation

Abstract: The modeling of the performance of large-area solar concentrators for central receiver power plants is formulated using a continuum field representation of ideal heliostat arrays that accounts for two governing factors: the law of reflection of light rays imposes steering constraints on mirror orientations; the proximity of mirrors creates shadow effects by blocking the incident and/or reflected solar radiation. The results of a steering analysis which develops the space-time characteristics of heliostats and of a shadow analysis which determines the local effectiveness of mirrors in reflecting solar energy to a central point are combined to obtain in closed analytical form the global characteristics of circular concentrators. These characteristics which appear as time profiles for mirror orientations, for effective concentration areas (i.e., reflected solar flux), and for concentration ratios, establish theoretical limits of performance against which actual or realistic solar power systems can be compared and assessed.

Sea Thermal Power as a Hydrogen and Methanol Generator

Abstract: Power is the major ingredient for making hydrogen and/or methanol, fresh water, and valuable minerals. The most abundant inexhaustible and least expensive source of power is from the thermal temperature differences in the ocean. The sun maintains the temperature differences in the ocean which is the largest natural collector and reservoir of solar energy. The cost of power to synthesize other fuels will be lower with sea solar power plants than by fossil, nuclear, or any other proposed method.

Closed Brayton Cycle Turbines for Satellite Solar Power Stations

Abstract: This paper discusses the construction problem of putting together a large power satellite employing turbine power generation. Various levels of technology have been discussed for power satellites; our current baseline is a near-term technology system. In other words, we think we know how to develop all the elements with only modest extensions of today’s state of the art. Our purpose was to analyze the cost and economics of this system, and see how close it comes to being competitive with alternate sources.

Energy and physics

Abstract: Discussions of energy in all its forms and aspects were to be found at the third general conference of the European Physical Society 'Energy and physics'. Thus, in addition to the more definitely physical sessions covering cosmology, plasmas, high energy particles and thermodynamics there were others more tightly linked to the immediate issues of our time on such subjects as geothermal and solar power, fission/fusion comparisons, environmental safety and degradation, future trends in energy consumption and strategies for the maintenance of energy supplies.

For solar power: Sunny days ahead? The future of sun-derived electric power is clouded by budgetary constraints, institutional and public inertia, and poor incentives

Abstract: The future of sun-derived electric power is clouded by budgetary constraints, institutional and public inertia, and poor incentives.

An Extension of the Haefele-Manne Model for Assessing Strategies for a Transition from Fossil Fuel to Nuclear and Solar Alternatives

Abstract: This paper reports on an extension of the Haefele-Manne model that assesses energy supply strategies for a transition from fossil fuel to nuclear and solar alternatives, and illustrates several optimized strategies. The expanded model solves the problem of how the electricity, petroleum-and-gas, and hydrogen produced by eight possible energy supplying alternatives (two fossil, three nuclear, two solar and one auxiliary) can be allocated to each of the three demand sectors (residential and commercial; industrial; transport) over a 100-year planning horizon, by using a ten-year period formulation. Relevant data for calculation are based on the Aerospace Corporation study for solar technologies, the NASA Systems Design Institute study for hydrogen technologies, and the Haefele-Manne study for fossil fuels and nuclear technologies. Since there are some uncertainties about these data, sensitivity analyses were carried out on the capital cost of solar power stations and on the fuel cost of coal.