06-04-2011, 09:53 AM
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ABSTRACT
The search for a new, safe and stable renewable energy source led to the idea of building a power station in space which transmits electricity to Earth. The concept of Solar Power Satellites (SPS) was invented by Glaser in 1968.Research is still going on in this field and NASA is planning to implement one by 2040. SPS converts solar energy into microwaves and transmit it to a receiving antenna on Earth for conversion to electric power. The key technology needed to enable the future feasibility of SPS is Microwave Power Transmission.
SPS would be a massive structure with an area of about 56 sq.m and would, weigh about 30,000 to 50,000 metric ton. Estimated cost is about $74 billion and would take about 30 years for its construction. In order to reduce the projected cost of a SPS suggestions are made to employ extraterrestrial resources for its construction. This reduces the transportation requirements of such a massive structure. However the realization of SPS concept holds great promises for solving energy crisis.
INTRODUCTION
The new millennium has introduced increased pressure for finding new renewable energy sources. The exponential increase in population has led to the global crisis such as global warming, environmental pollution and change and rapid decrease of fossil reservoirs. Also the demand of electric power increases at a much higher pace than other energy demands as the world is industrialized and computerized. Under these circumstances, research has been carried out to look into the possibility of building a power station in space to transmit electricity to Earth by way of radio waves-the Solar Power Satellites. Solar Power Satellites(SPS) converts solar energy in to micro waves and sends that microwaves in to a beam to a receiving antenna on the Earth for conversion to ordinary electricity.SPS is a clean, large-scale, stable electric power source. Solar Power Satellites is known by a variety of other names such as Satellite Power System, Space Power Station, Space Power System, Solar Power Station, Space Solar Power Station etc.[1].One of the key technologies needed to enable the future feasibility of SPS is that of Microwave Wireless Power Transmission.WPT is based on the energy transfer capacity of microwave beam i.e,energy can be transmitted by a well focused microwave beam. Advances in Phased array antennas and rectennas have provided the building blocks for a realizable WPT system [2].
WHY SPS
Increasing global energy demand is likely to continue for many decades. Renewable energy is a compelling approach “ both philosophically and in engineering terms. However, many renewable energy sources are limited in their ability to affordably provide the base load power required for global industrial development and prosperity, because of inherent land and water requirements. The burning of fossil fuels resulted in an abrupt decrease in their .it also led to the green house effect and many other environmental problems. Nuclear power seems to be an answer for global warming, but concerns about terrorist attacks on Earth bound nuclear power plants have intensified environmentalist opposition to nuclear power. Moreover, switching on to the natural fission reactor, the sun, yields energy with no waste products. Earth based solar panels receives only a part of the solar energy. It will be affected by the day & night effect and other factors such as clouds. So it is desirable to place the solar panel in the space itself, where, the solar energy is collected and converted in to electricity which is then converted to a highly directed microwave beam for transmission. This microwave beam, which can be directed to any desired location on Earth surface, can be collected and then converted back to electricity. This concept is more advantageous than conventional methods. Also the microwave energy, chosen for transmission, can pass unimpeded through clouds and precipitations.
SPS “THE BACKGROUND
The concept of a large SPS that would be placed in geostationary orbit was invented by Peter Glaser in 1968 [1].The SPS concept was examined extensively during the late 1970s by the U.S Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA). The DOE-NASA put forward the SPS Reference System Concept in 1979 [2]. The central feature of this concept was the creation of a large scale power infrastructure in space, consisting of about 60 SPS, delivering a total of about 300GW.But, as a result of the huge price tag, lack of evolutionary concept and the subsiding energy crisis in 1980-1981, all U.S SPS efforts were terminated with a view to re-asses the concept after about ten years. During this time international interest in SPS emerged which led to WPT experiments in Japan.
RECENT NASA EFFORTS
Fresh look Study
During 1995-96, NASA conducted a re-examination of the technologies, system concepts of SPS systems [2],[3].The principal objective of this ËœFresh Look Studyâ„¢ was to determine whether a SPS and associated systems could be defined. The Fresh Look Study concluded that the prospects for power from space were more technically viable than they had been earlier.
SSP Concept Definition Study
During 1998, NASA conducted the SSP Concept Definition Study which was a focused one year effort that tested the results of the previous Fresh Look Study. A principal product of the efforts was the definition of a family of strategic R&T road maps for the possible development of SSP technologies.
SSP Exploratory and Research Technology Program
In 2000, NASA conducted the SERT Program which further defined new system concepts. The SERT Program comprised of three complementary elements:
¢ System studies and analysis
Analysis of SSP systems and architecture concepts to address the economic viability as well as environmental issue assessments.
¢ SSP Research and technology
Focused on the exploratory research to identify system concepts and establish technical viability
¢ SPS technology demonstration
Initial small scale demonstration of key SSP concepts and / or components using related system / technologies.
SPS-A GENERAL IDEA
Solar Power Satellites would be located in the geosynchronous orbit. The difference between existing satellites and SPS is that an SPS would generate more power-much more power than it requires for its own operation.
The solar energy collected by an SPS would be converted into electricity, then into microwaves. The microwaves would be beamed to the Earthâ„¢s surface, where they would be received and converted back into electricity by a large array of devices known as rectifying antenna or rectenna.(Rectification is the process by which alternating electrical current ,such as that induced by a microwave beam , is converted to direct current). This direct current can then be converted to 50 or 60 Hz alternating current
Each SPS would have been massive; measuring 10.5 km long and 5.3 km wide or with an average area of 56 sq.km.The surface of each satellite would have been covered with 400 million solar cells. The transmitting antenna on the satellite would have been about 1 km in diameter and the receiving antenna on the Earthâ„¢s surface would have been about 10 km in diameter [5].The SPS would weigh more than 50,000 tons.
The reason that the SPS must be so large has to do with the physics of power beaming. The smaller the transmitter array, the larger the angle of divergence of the transmitted beam. A highly divergent beam will spread out over a large area, and may be too weak to activate the rectenna.In order to obtain a sufficiently concentrated beam; a great deal of power must be collected and fed into a large transmitter array.
ABSTRACT
The search for a new, safe and stable renewable energy source led to the idea of building a power station in space which transmits electricity to Earth. The concept of Solar Power Satellites (SPS) was invented by Glaser in 1968.Research is still going on in this field and NASA is planning to implement one by 2040. SPS converts solar energy into microwaves and transmit it to a receiving antenna on Earth for conversion to electric power. The key technology needed to enable the future feasibility of SPS is Microwave Power Transmission.
SPS would be a massive structure with an area of about 56 sq.m and would, weigh about 30,000 to 50,000 metric ton. Estimated cost is about $74 billion and would take about 30 years for its construction. In order to reduce the projected cost of a SPS suggestions are made to employ extraterrestrial resources for its construction. This reduces the transportation requirements of such a massive structure. However the realization of SPS concept holds great promises for solving energy crisis.
INTRODUCTION
The new millennium has introduced increased pressure for finding new renewable energy sources. The exponential increase in population has led to the global crisis such as global warming, environmental pollution and change and rapid decrease of fossil reservoirs. Also the demand of electric power increases at a much higher pace than other energy demands as the world is industrialized and computerized. Under these circumstances, research has been carried out to look into the possibility of building a power station in space to transmit electricity to Earth by way of radio waves-the Solar Power Satellites. Solar Power Satellites(SPS) converts solar energy in to micro waves and sends that microwaves in to a beam to a receiving antenna on the Earth for conversion to ordinary electricity.SPS is a clean, large-scale, stable electric power source. Solar Power Satellites is known by a variety of other names such as Satellite Power System, Space Power Station, Space Power System, Solar Power Station, Space Solar Power Station etc.[1].One of the key technologies needed to enable the future feasibility of SPS is that of Microwave Wireless Power Transmission.WPT is based on the energy transfer capacity of microwave beam i.e,energy can be transmitted by a well focused microwave beam. Advances in Phased array antennas and rectennas have provided the building blocks for a realizable WPT system [2].
WHY SPS
Increasing global energy demand is likely to continue for many decades. Renewable energy is a compelling approach “ both philosophically and in engineering terms. However, many renewable energy sources are limited in their ability to affordably provide the base load power required for global industrial development and prosperity, because of inherent land and water requirements. The burning of fossil fuels resulted in an abrupt decrease in their .it also led to the green house effect and many other environmental problems. Nuclear power seems to be an answer for global warming, but concerns about terrorist attacks on Earth bound nuclear power plants have intensified environmentalist opposition to nuclear power. Moreover, switching on to the natural fission reactor, the sun, yields energy with no waste products. Earth based solar panels receives only a part of the solar energy. It will be affected by the day & night effect and other factors such as clouds. So it is desirable to place the solar panel in the space itself, where, the solar energy is collected and converted in to electricity which is then converted to a highly directed microwave beam for transmission. This microwave beam, which can be directed to any desired location on Earth surface, can be collected and then converted back to electricity. This concept is more advantageous than conventional methods. Also the microwave energy, chosen for transmission, can pass unimpeded through clouds and precipitations.
SPS “THE BACKGROUND
The concept of a large SPS that would be placed in geostationary orbit was invented by Peter Glaser in 1968 [1].The SPS concept was examined extensively during the late 1970s by the U.S Department of Energy (DOE) and the National Aeronautics and Space Administration (NASA). The DOE-NASA put forward the SPS Reference System Concept in 1979 [2]. The central feature of this concept was the creation of a large scale power infrastructure in space, consisting of about 60 SPS, delivering a total of about 300GW.But, as a result of the huge price tag, lack of evolutionary concept and the subsiding energy crisis in 1980-1981, all U.S SPS efforts were terminated with a view to re-asses the concept after about ten years. During this time international interest in SPS emerged which led to WPT experiments in Japan.
RECENT NASA EFFORTS
Fresh look Study
During 1995-96, NASA conducted a re-examination of the technologies, system concepts of SPS systems [2],[3].The principal objective of this ËœFresh Look Studyâ„¢ was to determine whether a SPS and associated systems could be defined. The Fresh Look Study concluded that the prospects for power from space were more technically viable than they had been earlier.
SSP Concept Definition Study
During 1998, NASA conducted the SSP Concept Definition Study which was a focused one year effort that tested the results of the previous Fresh Look Study. A principal product of the efforts was the definition of a family of strategic R&T road maps for the possible development of SSP technologies.
SSP Exploratory and Research Technology Program
In 2000, NASA conducted the SERT Program which further defined new system concepts. The SERT Program comprised of three complementary elements:
¢ System studies and analysis
Analysis of SSP systems and architecture concepts to address the economic viability as well as environmental issue assessments.
¢ SSP Research and technology
Focused on the exploratory research to identify system concepts and establish technical viability
¢ SPS technology demonstration
Initial small scale demonstration of key SSP concepts and / or components using related system / technologies.
SPS-A GENERAL IDEA
Solar Power Satellites would be located in the geosynchronous orbit. The difference between existing satellites and SPS is that an SPS would generate more power-much more power than it requires for its own operation.
The solar energy collected by an SPS would be converted into electricity, then into microwaves. The microwaves would be beamed to the Earthâ„¢s surface, where they would be received and converted back into electricity by a large array of devices known as rectifying antenna or rectenna.(Rectification is the process by which alternating electrical current ,such as that induced by a microwave beam , is converted to direct current). This direct current can then be converted to 50 or 60 Hz alternating current
Each SPS would have been massive; measuring 10.5 km long and 5.3 km wide or with an average area of 56 sq.km.The surface of each satellite would have been covered with 400 million solar cells. The transmitting antenna on the satellite would have been about 1 km in diameter and the receiving antenna on the Earthâ„¢s surface would have been about 10 km in diameter [5].The SPS would weigh more than 50,000 tons.
The reason that the SPS must be so large has to do with the physics of power beaming. The smaller the transmitter array, the larger the angle of divergence of the transmitted beam. A highly divergent beam will spread out over a large area, and may be too weak to activate the rectenna.In order to obtain a sufficiently concentrated beam; a great deal of power must be collected and fed into a large transmitter array.
