Space power generation

In the near future, thermionic energy converter will be a more promising device for space power generation. To this end, a solar heated thermionic energy converter has been developed by applying functionally graded materials (FGM) to the electrode. It is majorly composed of a W/Re-FGM emitter, a NbOx collector, and a TiC/Mo-FGM solar receiver. 

The isotope Cm is the largest contributor to the alpha activity of irradiated uranium fuel from power reactors. It is an important source of the 2n + 2 decay chain in the high4evel wastes from fuel reprocessing. The alpha activity of Cm results in an internal heat-generation rate of 120 W/g of pure Cm. Separated Cm, prepared by the neutron irradiation of Am, provides a useful alternative for a thermoelectric source and for radionuclide batteries when relatively high outputs are desired over short periods of the order of its half-Ufe of 163 days. For example, a space power generator denoted as SNAP-11 contained 7.5 g of Cm and produced 20 W of thermoelectric power. Cm is also the decay source of Pu, which is used as a longer-lived radioisotope heat source. 

A comprehensive analysis of much of the data for dilute gas-solid suspension was reported by Pfeffer et al. [248]. Correlations for both heat transfer coefficient and friction factor were developed. These investigators presented a feasibility study of using suspensions as the working fluid in a Brayton space power generation cycle [249]. A subsequent presentation of design information and guide to the literature is given by Depew and Kramer [250]. 

R. Pfeffer, S. Rossetti, and S. Lieblein, The Use of a Dilute Gas-Solid Suspension as the Working Fluid in a Single Loop Brayton Space Power Generation Cycle, AIChE Paper 49c, AIChE, New York, presented at 1967 national meeting. 

There are four principal ways ia which biomass is used as a reaewable eaergy resource. The first, and most common, is as a fuel used directiy for space and process heat and for cooking. The second is as a fuel for electric power generation. The third is by gasification iato a fuel used oa the site. The fourth is by coaversioa iato a Hquid fuel that provides the portabiUty aeeded for transportatioa and other mobile appHcations of energy. Figure 7 shows the varied pathways which can be followed to convert biomass feedstocks to useful fuels or electricity. 

Thermoelectric devices represent niche markets, but as economic and environmental conditions continue to change, they appear poised to advance into more common use. Thermoelectric power generators are in use in many areas, including sateUites, deep-space probes, remote-area weather stations, undersea navigational devices, military and remote-area communications, and cathodic protection. 

Perhaps the ultimate combined appliances, which are currently under development, will he microturbines or fuel cell power generators used as small-scale co-generation systems. These would supply not only electricity, but space and water heating as well. 

Boilers may be used for domestic hot water heating, space heating, waste heat, or chemical recovery. They also may be used for mechanical work, electrical power generation, cogeneration, and innumerable industrial process applications using direct (live) steam or indirect steam (e.g., coil heated) processes. Both FT and WT designs are commonly employed for heat-recovery applications. 

Industrial boilers are employed over a wide range of applications, from large power-generating units with sophisticated control systems, which maximize efficiency, to small low-pressure units for space or process heating, which emphasize simpficity and low capital cost. Although their usual primary function is to provide energy in the form of steam, in some applications steam generation is incidental to a process objective, e.g., a chemical recovery unit in the paper industry. 

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