05-04-2011, 12:21 PM
SUBMITTED BY:-
ANCHAL SRIVASTAVA
[attachment=11736]
SOLAR POWER SATELLITES
Space-based solar power (SBSP) (or historically space solar power (SSP)) is a system for the collection of solar power in space, for use on Earth. SBSP differs from the usual method of solar power collection in that the solar panels used to collect the energy would reside on a satellite in orbit, often referred to as a solar power satellite (SPS), rather than on Earth's surface. In space, collection of the Sun's energy is unaffected by the day/night cycle, weather, seasons, or the filtering effect of Earth's atmospheric gases.
The world Radiation Centre's 1985 standard extraterrestrial spectrum for solar irradiance is 1367 W/m2. The integrated total terrestrial solar irradiance is 950 W/m2. A major interest in SBSP stems from the length of time the solar collection panels can be exposed to a consistently high amount of solar radiation.
The collection of solar energy in space for use on Earth introduces the new problem of transmitting energy from the collection point, in space, to the place where the energy would be used, on Earth's surface. Since wires extending from Earth's surface to an orbiting satellite would be impractical, many SBSP designs have proposed the use of microwave beams for wireless power transmission. The collecting satellite would convert solar energy into electrical energy, which would then be used to power a microwave emitter directed at a collector on the Earth's surface.
INTRODUCTION
The SBSP concept, originally known as Satellite Solar Power System ("SSPS") was first described in November 1968. In 1973 Peter Glaser was granted U.S. patent number 3,781,647 for his method of transmitting power over long distances (e.g., from an SPS to the Earth's surface) using microwaves from a very large (up to one square kilometer) antenna on the satellite to a much larger one on the ground, now known as a rectenna.
Dr. Peter Glaser introduces the concept of a large solar power satellite system of square miles of solar collectors in high geosynchronous orbit (GEO is an orbit 36,000 km above the equator), for collection and conversion of sun's energy into an electromagnetic microwave beam to transmit usable energy to large receiving antennas (rectennas) on earth for distribution on the national electric power grid.
Dr. Peter Glaser was granted U.S. patent number 3,781,647 for his method of transmitting power over long distances (e.g., from an SPS to the Earth's surface) using microwaves from a very large (up to one square kilometer) antenna on the satellite to a much larger one on the ground, now known as a rectenna.
John Mankins of NASA testifies in the U.S. House "Large-scale SSP is a very complex integrated system of systems that requires numerous significant advances in current technology and capabilities. A technology roadmap has been developed that lays out potential paths for achieving all needed advances — albeit over several decades.
CONSTRUCTIONAL FEATURES (SPS)
Space-based solar power essentially consists of three parts:
1. a means of collecting solar power in space, for example via solar cells or a heat engine.
2. a means of transmitting power to earth, for example via microwave or laser.
3. a means of receiving power on earth, for example via a microwave antenna (rectenna).
The space-based portion will be in a freefall, vacuum environment and will not need to support itself against gravity other than relatively weak tidal stresses. It needs no protection from terrestrial wind or weather, but will have to cope with space-based hazards such as micrometeors and solar storms.
SOLAR ENERGY CONVERSION
Two basic methods of converting sunlight to electricity have been studied: photovoltaic (PV) conversion, and solar dynamic (SD) conversion.
Most analyses of solar power satellites have focused on photovoltaic conversion (commonly known as “solar cells”).
Photovoltaic conversion uses semiconductor cells (e.g., silicon or gallium arsenide) to directly convert photons into electrical power via a quantum mechanical mechanism. Photovoltaic cells are not perfect in practice, as material purity and processing issues during production affect performance; each has been progressively improved for some decades. Some new, thin-film approaches are less efficient (about 20% vs 35% for best in class in each case), but are much less expensive and generally lighter.
In an SPS implementation, photovoltaic cells will likely be rather different from the glass-pane protected solar cell panels familiar to many from current terrestrial use, since they will be optimized for weight, and will be designed to be tolerant to the space radiation environment (it turns out fortuitously, that thin film silicon solar panels are highly insensitive to ionising radiation), but will not need to be encapsulated against corrosion by the elements. They do not require the structural support required for terrestrial use, where the considerable gravity and wind loading imposes structural requirements on terrestrial implementations.
Wireless power transmission was proposed early on as a means to transfer energy from collection to the Earth's surface. The power could be transmitted as either microwave or laser radiation at a variety of frequencies depending on system design.
LASER POWER BEAMING EXPERIMENTS
A large-scale demonstration of power beaming is a necessary step to the development of solar power satellites.
Laser power beaming was envisioned by some at NASA as a stepping stone to further industrialization of space.
In the 1980’s researchers at NASA worked on the potential use of lasers for space-to-space power beaming, focusing primarily on the development of a solar-powered laser.
In 1989, it was suggested that power could also be usefully beamed by laser from Earth to space. In 1991 the SELENE project (Space Laser Energy) was begun, which included the study of laser power beaming for supplying power to a lunar base.
In 1988, the use of an Earth-based laser to power an electric thruster for space propulsion was proposed by Grant Logan, with technical details worked out in 1989. He proposed using diamond solar cells operating at six hundred degrees to convert ultraviolet laser light, a technology that has yet to be demonstrated even in the laboratory. His ideas were adapted to be more practical.
The SELENE program was a two-year research effort, but the cost of taking the concept to operational status was too high, and the official project was ended in 1993, before reaching a space-based demonstration.
ANCHAL SRIVASTAVA
[attachment=11736]
SOLAR POWER SATELLITES
Space-based solar power (SBSP) (or historically space solar power (SSP)) is a system for the collection of solar power in space, for use on Earth. SBSP differs from the usual method of solar power collection in that the solar panels used to collect the energy would reside on a satellite in orbit, often referred to as a solar power satellite (SPS), rather than on Earth's surface. In space, collection of the Sun's energy is unaffected by the day/night cycle, weather, seasons, or the filtering effect of Earth's atmospheric gases.
The world Radiation Centre's 1985 standard extraterrestrial spectrum for solar irradiance is 1367 W/m2. The integrated total terrestrial solar irradiance is 950 W/m2. A major interest in SBSP stems from the length of time the solar collection panels can be exposed to a consistently high amount of solar radiation.
The collection of solar energy in space for use on Earth introduces the new problem of transmitting energy from the collection point, in space, to the place where the energy would be used, on Earth's surface. Since wires extending from Earth's surface to an orbiting satellite would be impractical, many SBSP designs have proposed the use of microwave beams for wireless power transmission. The collecting satellite would convert solar energy into electrical energy, which would then be used to power a microwave emitter directed at a collector on the Earth's surface.
INTRODUCTION
The SBSP concept, originally known as Satellite Solar Power System ("SSPS") was first described in November 1968. In 1973 Peter Glaser was granted U.S. patent number 3,781,647 for his method of transmitting power over long distances (e.g., from an SPS to the Earth's surface) using microwaves from a very large (up to one square kilometer) antenna on the satellite to a much larger one on the ground, now known as a rectenna.
Dr. Peter Glaser introduces the concept of a large solar power satellite system of square miles of solar collectors in high geosynchronous orbit (GEO is an orbit 36,000 km above the equator), for collection and conversion of sun's energy into an electromagnetic microwave beam to transmit usable energy to large receiving antennas (rectennas) on earth for distribution on the national electric power grid.
Dr. Peter Glaser was granted U.S. patent number 3,781,647 for his method of transmitting power over long distances (e.g., from an SPS to the Earth's surface) using microwaves from a very large (up to one square kilometer) antenna on the satellite to a much larger one on the ground, now known as a rectenna.
John Mankins of NASA testifies in the U.S. House "Large-scale SSP is a very complex integrated system of systems that requires numerous significant advances in current technology and capabilities. A technology roadmap has been developed that lays out potential paths for achieving all needed advances — albeit over several decades.
CONSTRUCTIONAL FEATURES (SPS)
Space-based solar power essentially consists of three parts:
1. a means of collecting solar power in space, for example via solar cells or a heat engine.
2. a means of transmitting power to earth, for example via microwave or laser.
3. a means of receiving power on earth, for example via a microwave antenna (rectenna).
The space-based portion will be in a freefall, vacuum environment and will not need to support itself against gravity other than relatively weak tidal stresses. It needs no protection from terrestrial wind or weather, but will have to cope with space-based hazards such as micrometeors and solar storms.
SOLAR ENERGY CONVERSION
Two basic methods of converting sunlight to electricity have been studied: photovoltaic (PV) conversion, and solar dynamic (SD) conversion.
Most analyses of solar power satellites have focused on photovoltaic conversion (commonly known as “solar cells”).
Photovoltaic conversion uses semiconductor cells (e.g., silicon or gallium arsenide) to directly convert photons into electrical power via a quantum mechanical mechanism. Photovoltaic cells are not perfect in practice, as material purity and processing issues during production affect performance; each has been progressively improved for some decades. Some new, thin-film approaches are less efficient (about 20% vs 35% for best in class in each case), but are much less expensive and generally lighter.
In an SPS implementation, photovoltaic cells will likely be rather different from the glass-pane protected solar cell panels familiar to many from current terrestrial use, since they will be optimized for weight, and will be designed to be tolerant to the space radiation environment (it turns out fortuitously, that thin film silicon solar panels are highly insensitive to ionising radiation), but will not need to be encapsulated against corrosion by the elements. They do not require the structural support required for terrestrial use, where the considerable gravity and wind loading imposes structural requirements on terrestrial implementations.
Wireless power transmission was proposed early on as a means to transfer energy from collection to the Earth's surface. The power could be transmitted as either microwave or laser radiation at a variety of frequencies depending on system design.
LASER POWER BEAMING EXPERIMENTS
A large-scale demonstration of power beaming is a necessary step to the development of solar power satellites.
Laser power beaming was envisioned by some at NASA as a stepping stone to further industrialization of space.
In the 1980’s researchers at NASA worked on the potential use of lasers for space-to-space power beaming, focusing primarily on the development of a solar-powered laser.
In 1989, it was suggested that power could also be usefully beamed by laser from Earth to space. In 1991 the SELENE project (Space Laser Energy) was begun, which included the study of laser power beaming for supplying power to a lunar base.
In 1988, the use of an Earth-based laser to power an electric thruster for space propulsion was proposed by Grant Logan, with technical details worked out in 1989. He proposed using diamond solar cells operating at six hundred degrees to convert ultraviolet laser light, a technology that has yet to be demonstrated even in the laboratory. His ideas were adapted to be more practical.
The SELENE program was a two-year research effort, but the cost of taking the concept to operational status was too high, and the official project was ended in 1993, before reaching a space-based demonstration.
