solar power station in an inclined low earth orbit can be complemented best with hydroelectric energy. For a solar power station in geostationary orbit again hydroelectric energy fits best. Figure 2.6 Assessment of Mix of Power Sources Direct Heat Production (Non Electric) Traditionally heat generation is the major and most important use of energy in many regions. In this section only the direct conversion of primary energy into heat is regarded (e.g. not electric heating). Heat energy can be subdivided into room heating and heat for industrial processes. Physically spoken heat is a “low value energy” therefore it can be generated from every form of energy at an efficiency rate of practically 100%. Therefore it is effective to generate heat directly from the primary source instead of conversion with a low efficiency rate in-between. This is the reason it is mainly generated by burning processes of fossil fuels like coal, gas or oil. Solar collectors are finding increasing use for direct heat production. They are water (or liquid) cooled systems and are usually installed on rooftops. Since the output temperatures do not have to be very high for room heating, it is a simple and inexpensive system. This might become the first economical application of solar energy. The heat conversion can take place at the individual user (house) or centralized. Centralized heating has the following advantages: • More effort can be put into optimization of the burning process, maintenance of the system and into cleaning of exhaust gasses. • Expensive technologies can be used like geothermal energy, garbage burning, coupling with electricity production or even decentralized nuclear heat production. Remote heating systems use thermal insulated pipe systems to distribute the heat to the user. The disadvantages of remote heat stem are the high cost of the pipe system and its high energy losses for long pipes (in East Germany these losses accounted to 40% to 50%). In regions where electric power is available in abundance electric heating for houses is used to a large extent. 2.2.3 Cost of Terrestrial Energy This section provides a cost target for evaluating the economic viability of the space solar power program. It will be a moving target because the price of energy will change as energy resources become depleted, world energy demand increases, and world politics change. The absolute upper bound to terrestrial energy costs can be determined by estimating the cost of energy in a hydrogen energy economy with virtually unlimited supply. This scenario assumes hydrogen is produced by steam refining of methane, electrolysis of water, or refining methanol using solar energy. Current cost of 70,000 standard cubic feet of gaseous hydrogen is $15k using conventional energy sources for production. Solar energy is currently about twice as expensive so a projected cost of $30k per 70,000
RkJQdWJsaXNoZXIy MTU5NjU0Mg==