10.3 Space to Earth Demonstration 10.3.1 Project Description The general objective of a space to Earth demonstration is four-fold. Firstly, to demonstrate an environmentally safe energy source for future use. Secondly to explore the atmosphere and ecological effects of power beaming. Thirdly, to see if solar power beaming can be cost-effective and fourthly to demonstrate the technical feasibility of collecting beamed power. The goal of the following sections is to highlight how a demonstration program for beaming power from space to ground can be achieved, with the following high level planning and cost constraints: • Time scale: the program should be realized within 10 years. • Cost target: the overall cost of such a program should not exceed $800 M. These two constraints will mainly drive the system. Indeed, the near-term schedule means for instance that no revolutionary technological step nor spectacular improvement is expected to occur. In addition, the cost allocation quickly leads to the conclusion that a simple system shall be built, i.e one automatic satellite launched by a single launcher (no assembly in space, no maintenance nor astronaut intervention). A spacecraft in a sun-synchronous orbit beaming at 35 GHz will be the major cost, using $600 M plus $80 M for the launch. The advantage of this concept is that once the spacecraft is in orbit, we have the flexibility to beam to any part of the world and the services of the spacecraft could be used by any buyer. The mission envisioned was to supply isolate areas for local use, staying within the limits of a reduced scale demonstration. Antarctica was originally discussed as a possible site for space to Earth power beaming. A closer look presented here and in the following technical sections reveal several doubts about using this location at this time except for scientific experimentation. One possibility would be to use Antarctica as the primary site for atmosphere testing and possible ground-based testing with sensors placed to measure the amount of energy reaching the ground to theoretically determine how much energy could be collected if a rectenna was built. A small-scale rectenna could be built instead in a desert to show that we can collect the power even though at this stage it will be very little, a maximum of 200 mW/m2. This location could also serve as another data point for atmospheric testing. The following sections further explore the possibility of using Antarctica as a site for a space to Earth power beaming demonstration. The motivation is primarily an environmental one and so the issues will be discussed from that perspective. Regardless of final location, a similar analysis applies. Problems With Current Energy Sources Increasingly there have been efforts by many national and international organizations to move away from non-renewable energy sources such as fossil fuels. This includes the effort to reduce the CO2 levels being released into the atmosphere contributing to depletion of the ozone layer and the greenhouse effect. One problem is that many developing countries and remote locations do not have the resources to meet their increasing energy needs as well as develop new energy sources, thus compromising global energy goals. A major hope of a space solar power program would be to provide power to areas in need of more energy and also an alternative source of energy. Antarctica was considered as one possible site for a space to Earth demonstration because of the great need there for an alternative energy source. Currently, oil is brought into Antarctica by tankers at high delivery cost. Low temperatures reaching -85°C make biodegradation nearly impossible, raising a problem with normal waste management and increasing the environmental damage through oil spill pollution. Another possible location would be a desert such as the Arizona desert in the U.S. This would serve as a model for a remote location where energy is also expensive, or a developing country, where wood and coal may be the primary sources of energy contributing to environmental pollution and deforestation Because of its sparse ecology and relatively low power needs, Antarctica seems to be a prime candidate for a space to Earth power beaming demonstration. It is considered to be a huge desert as its non coastal regions receive only 5 cm of precipitation per year. The terrestrial living organisms consist mostly of birds and some plants, mostly lichens. Seven countries have territorial claims in Antarctica and the power loads are some of the poorest economically in addition to being orders of magnitude lower than almost any other populated areas [Dalby, 1992].
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