Published on Apr 02, 2024
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.
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 r ecently 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 ? 2 . To increase ? the field distribution on radiating aperture is made as a tapered distribution. High value of ? is supposed to be in the majority of known projects of the WPT systems.
The development and implementation of any new energy source present major challenges. And it is acknowledged that bringing about the use of Space Solar Power on the Earth may be particularly daunting because it is so different. The major challenges are perceived to be:
(1) The mismatch between the time horizon for the implementation of SSP and that for the expansion of conventional energy resources
(2) The fact that space power is intrinsically global, requiring enterprise models that give every player a suitable stake and adequate safeguards
(3) The potential for concerns over reliability, safety and environmental implications
(4) The need to obtain publicly-allocated resources outside the normal purview of the energy community
(5) The prevailing mind set which tends to view the future energy infrastructure as an extrapolation of the present one.
However great the challenges, it is important to enhance global energy systems so they work for all the people of the Earth. It is asserted that a prudent course would be to give serious attention to all plausible options and prepare to implement several if needed.
It is well understood that something as vast as the global energy system can change only slowly. In fact, it takes from 50 to 75 years for one source to lose dominance and be replaced by another. Even if it is recognized and agreed that a shift to different sources is needed, penetration would be slow.
The time horizon for implementing Space Solar Power will be at least a couple of decades. Current work being carried out in the US by the National Aeronautics and Space Administration (NASA) and in Japan by the Ministry of Economy, Trade and Industry (METI) indicate that demonstrations of space-to-ground transmission of power could come in the current decade and initial commercial power delivery in about 20 years. A significant contribution in terms of global energy would clearly take substantially longer. The challenge presented by this mismatch can be addressed in two ways:
First, governments will need to underwrite, to a major extent, the R&D needed to bring the enabling technologies to maturity. Governments have traditionally
supported R&D efforts as a spur to new economic activity. Examples can be found in the development of rail and air transport systems, computers and, most recently, the internet.
Second, a near-term involvement by the users (the electric utilities and their suppliers) should be promoted. It is very important for these prospective users to keep abreast of progress as the technology matures.
The global scope of Space Solar Power will present another significant challenge in terms of appropriate enterprise models that give every player a suitable stake and adequate safeguards. International cooperation in the energy area is commonplace and indeed the infrastructure for energy is highly interdependent around the world. Energy acquisition, distribution, and utilization tend to involve multiple countries and far-flung networks along which various forms of energy flow. Similarly, international collaboration has been important in major space ventures of which Space Solar Power would certainly be an example.
Briefly, there are several reasons for international collaboration. The most compelling are:
• The need for increased energy supplies is a global need
• The impact on the environment of present energy practices is a matter of worldwide concern
• International coordination in energy provisioning is common today and the interdependence will only grow in the future
• The needed technology is widely distributed and no one country has all the capability
• The large scale of Space Solar Power will require international financing
• International regulations control critical resources, specifically slots in geosynchronous orbit and appropriate transmission frequencies
• Recognition of Space Solar Power as a viable and safe approach to energy will require an international consensus.
• 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
• Launch costs
• Capital cost even given cheap launchers
• Would require a network of hundreds of satellites
• Possible health hazards
• The size of the antennas and rectennas
• Geosynchronous satellites would take up large sections of space
• Interference with communication satellites
Markets that will be made accessible with WPT will have a profound influence on global business activities and industry competitiveness. The following are examples of the future commercial opportunities of WPT:
1. Roadway powered electric vehicles for charging electric batteries with WPT from microwave generators embedded in the roadway while a vehicle is traveling at highway speed, thus eliminating stops to exchange or recharge batteries greatly extending travel range.
2. High-altitude, long-endurance aircraft maintained at a desired location for weeks or months at 20 km for communications and surveillance instead of satellites, at greatly reduced costs.
3. Power relay satellites to access remote energy sources by uncoupling primary electricity generation from terrestrial transmission lines (15). Power is transmitted from distant sites to geosynchronous orbit and then reflected to a receiver on Earth in a desired location.
4. Solar power satellites in low-Earth or geosynchronous orbit or on the Moon to supply terrestrial power demands on a global scale.
There is little doubt that the supply of energy must be increased dramatically in coming decades. Furthermore, it appears almost certain that there will be a shift toward renewable sources and that solar will be a major contributor. It is asserted that if the energy system of the world is to work for all its people and be adequately robust, there should be several options to develop in the pursuit of and expanded supply. While the option of Space Solar Power may seem futuristic at present, it is technologically feasible and, given appropriate conditions, can become economically viable. It is asserted that it should be among those options actively pursued over coming decades. The challenges to the implementation of Space Solar Power are significant, but then no major expansion of energy supply will be easy. These challenges need to be tackled vigorously by the space, energy and other communities.
Finally, it should be emphasized that if we fail to develop sustainable and clean energy sources and try to limp along by extrapolating present practices, the result is very likely to be thwarted development of economic opportunities for many of the Earth's people and, almost certainly, adverse changes to the planetary environment.
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