Wireless Power Transmission via Solar Power Satellite
Published on Feb 12, 2016
A major problem facing Planet Earth is provision of an adequate supply of clean energy. It has been that we face "...three simultaneous challenges -- population growth, resource consumption, and environmental degradation -- all converging particularly in the matter of sustainable energy supply."
It is widely agreed that our current energy practices will not provide for all the world's peoples in an adequate way and still leave our Earth with a livable environment. Hence, a major task for the new century will be to develop sustainable and environmentally friendly sources of energy.
Projections of future energy needs over this new century show an increase by a factor of at least two and one Half, perhaps by as much as a factor of five. All of the scenarios from reference 3 indicate continuing use of fossil sources, nuclear, and large hydro. However, the greatest increases come from "new renewables" and all scenarios show extensive use of these sources by 2050. Indeed, the projections indicate that the amount of energy derived from new renewables by 2050 will exceed that presently provided by oil and gas combined. This would imply a major change in the world's energy infrastructure. It will be a Herculean task to acquire this projected amount of energy. This author asserts that there are really only a few good options for meeting the additional energy needs of the new cen
Projections of future energy needs over this new century show an increase by a factor of at least two and one Half, perhaps by as much as a factor of five. All of the scenarios from reference 3 indicate continuing use of fossil sources, nuclear, and large hydro. However, the greatest increases come from "new renewables" and all scenarios show extensive use of these sources by 2050. Indeed, the projections indicate that the amount of energy derived from new renewables by 2050 will exceed that presently provided by oil and gas combined. This would imply a major change in the world's energy infrastructure.
It will be a Herculean task to acquire this projected amount of energy. This author asserts that there are really only a few good options for meeting the additional energy needs of the new century in an environmentally acceptable way.One of the so-called new renewables on which major reliance is almost certain to be placed is solar power. Solar power captured on the Earth is familiar to all. However, an alternative approach to exploiting solar power is to capture it in space and convey it to the Earth by wireless means.
As with terrestrial capture, Space Solar Power (SSP) provides a source that is virtually carbon-free and sustainable. As will be described later, the power-collecting platforms would most likely operate in geosynchronous orbit where they would be illuminated 24 hours a day (except for short eclipse periods around the equinoxes). Thus, unlike systems for the terrestrial capture of solar, a space-based system would not be limited by the vagaries of the day-night cycle. Furthermore, if the transmission frequency is properly chosen, delivery of power can be carried out essentially independent of weather conditions. Thus Space Solar Power could provide base load electricity
The vision of achieving WPT on a global scale was proposed over 100 years ago when Nikola Tesla first started experiments with WPT, culminating with the construction of a tower for WPT on Long Island, New York, in the early 1900s. Tesla's objective was to develop the technology for transmitting electricity to anywhere in the world without wires. He filed several patents describing wireless power transmitters and receivers. However, his knowledge of electrical phenomena was largely empirical and he did not achieve his objective of WPT, although he was awarded the patent for wireless radio in 1940.
The development of WPT was not effectively pursued until the 1960s when the U.S. Air Force funded the development of a microwave-powered helicopter platform. A successful demonstration of a microwave beam-riding helicopter was performed in 1965. This demonstration proved that a WPT system could be constructed and that effective microwave generators and receivers could be developed for efficient conversion of microwaves into DC electricity.
The growing interest in solar energy conversion methods and solar energy applications in the 1960s and the limitations for producing cost-effective base load power caused by adverse weather conditions and diurnal changes led to the solar power satellite concept in 1968 as a means to convert solar energy with solar cell arrays into electricity and feed it to a microwave generator forming part of a planar, phased-array antenna. In geosynchronous orbit, the antenna would direct a microwave beam of very low power density precisely to one or more receiving antennas at desired locations on Earth. At a receiving antenna, the microwave energy would be safely and very efficiently reconvened into electricity and then transmitted to users
Two types of WPT:
1) Ground based power transmission
2) Space based power transmission
But Space-based power transmission is preferred over Ground-based power transmission.
Ground is (obviously) cheaper per noontime watt, but:
• Space gets full power 24 hours a day
– 3X or more Watt-hours per day per peak watt
– No storage required for nighttime power
• Space gets full power 7 days a week – no cloudy days
• Space gets full power 52 weeks a year
– No long winter nights, no storms, no cloudy seasons
• Space delivers power where it’s needed
– Best ground solar sites (deserts) are rarely near users
• Space takes up less, well, space
– Rectennas are 1/3 to 1/10 the area of ground arrays
– Rectennas can share land with farming or other uses
Solar power from the satellite is sent to Earth using a microwave transmitter. This transmission is transmitted to the relevant position via an antenna. The transmission is transmitted through space and atmosphere and received on earth by an antenna called the rectenna. Recent developments suggest using laser by using recently developed solid state lasers allow efficient transfer of power. A range of 10% to 20% efficiency within a few years can be attained, but further experimentation still required taking into consideration the possible hazards that it could cause to the eyes.
In comparison to laser transmission microwave transmission is more developed, has high efficiency up to 85%, beams is far below the lethal levels of concentration even for a prolonged exposure. The microwave transmission designed has the power level well below the international safety standard (Frequency 2.45 GHz microwave beam). The electric current generated from the photovoltaic cells is passed through a magnetron which converts the electric current to electromagnetic waves. This electromagnetic wave is passed through a waveguide which shapes the characteristics of the electromagnetic wave.
Effectiveness of Wireless Power Transmission (WPT) depends on many parameters. Only a part of WPT system is discussed below, which includes radiating and receiving antennas and the environment between them. The wave beam is expanded proportionately to the propagation distance and a flow power density is increased inversely proportional to the square of this distance. However the WPT has some peculiarities, which will be mentioned here. WPT systems require transmitting almost whole power that is radiated by the transmitting side. So, the useful result is the power quantity at the receiving antenna, but not the value of field amplitude as it is usually required. Efficiency of WPT systems is the ratio of energy flow, which is intercepted by receiving antenna to the whole radiating energy.
Field distribution on the receiving antenna usually is uniform because its size is small comparatively to the width of the beam. For WPT systems this distribution isn’t uniform. It has a taper form and it depends on the field distribution on the transmitting antenna.
For increasing of the energy concentration on the receiving antenna the phase distribution on the radiating antenna has usually a spherical form with the center in the point on crossing of the receiving plate and the radiating axis. Radiating antenna of the WPT systems usually has a taper distribution of the field. This distribution allows to increase the efficiency and to decrease the field out of the receiving antenna.
The efficiency of energy transmission is expressed by the functional Λ2. To increase Λ the field distribution on radiating aperture is made as a tapered distribution. High value of Λ is supposed to be in the majority of known projects of the WPT systems.
However, the effectiveness of the WPT system is defined not only by the value of Λ. It is also determined by the rectangularity of the field distribution on the radiating aperture, the rectangular distribution factor in the theory of antennas is usually called the surface utilization factor χ. The meaning of these two parameters Λ and χ is discrepant because to increase Λ2 it is necessary to have the field falling down to edges, but to increase χ it is necessary to have a uniform field.
• Unlimited energy resource
• Energy delivered anywhere in the world
• Zero fuel cost
• Zero CO2 emission
• Minimum long-range environmental impact
• Solar radiation can be more efficiently collected in space
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