How to study the feasibility of space solar power. The tendency of engineers working on space projects is to design to maximize performance with little regard to cost. This is not the fault of the engineers, but rather the mode they are encouraged to work in when space projects are government sponsored. And one certainly can’t fault an engineer for maximizing performance and designing to the customers specifications. Even our current project of building a cost model for space solar power is based largely on going around and asking aerospace engineers for component costs. What we need to do is to design a space solar power system that can be installed for $2 to $4 per Watt while still meeting the needs of the customers. This mode of design challenges engineers to really think hard and leads to innovation. Not only must we have low cost PV, but also low cost balance of systems (structure, transmitter and control systems). Before commercial funds could be obtained to finance a space solar power plant, demonstration systems would have to be built with government funding. Government funding should come largely from countries who have serious customers. After demos had been done, we would need to get some serious customers signed up, if a commercial plant was to be built Market development should be given equal priority to technical systems development (maybe more!) So, it is not only the cost per kWh we have to consider. If capital costs are too high, it will be impossible to obtain financing, even if the cost per kWh over 20 years is low. Another important goal is to get the SSP up and running within a year or 2 of obtaining financing. There are two main reasons for this. 1) The cost of money will be high for such a risky project and 2) the competition might beat you on price if you don’t get going quickly. SSPs are often discussed as systems that should be built to last 20 years. In this era of rapid advances is PV and other solar energy system components, it might be smarter to build an SSP that can evolve over 20 years. For example a “power tower” arrangement would allow for the replacement of degraded PV with new, higher efficiency PV. Such an upgrade would allow the SSP power company to sell more power with the same basic SSP. This may even be necessary, given the competition. For a development program, plan it to take 2 years. If it is not possible to have a demo of SSP ready in two years, then the problems are probably not technical Typical problems include lack of commitment of funding agencies and hence dribble of funding, no reasonable launch opportunities, no market identified, and so on. To keep development costs low, we need to use existing technology, or very close to it. The bottom line is that it is reasonable to develop a demonstration space solar power system, provided that a large part of the effort is devoted to developing the market (finding customers) and the demo SSP is designed to meet a cost goal as well as a performance goal Comparisons Comparison #1 PV + reservoir storage To get to the bottom line of how space solar power might compare to terrestrial solar power, I’ll show how much PV, land and dollars it would take to supply 5 gigawatts to a large city. A large city (or industrializing region) needs a large amount of power most of the day. We already know that an SSP in geosynchronous orbit could supply 5 gigawatts 24 hours per day (120 GWh or 1.2E8 kWh) using a 1 km transmitter and 10 km rectenna.
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