 Recent advances in thermal-to-electric conversion technologies such as thermoelectrics and thermophotovoltaics have demonstrated the potential for achieving high-efficiency, solid-state electric generators that could convert thermal energy to electricity for future electric and hybrid electric military platforms. The efficiency by which heat can be converted to electricity is, of course, limited by the theoretical maximum efficiency of the Carnot cycle. Although the Carnot efficiencies drop as the temperature differences between hot and cold sides decrease, the theoretical maximum conversion efficiencies can range from a low of ~ 40 percent to a high of
~ 77 percent using thermal sources consistent with those found on various military platforms where available hot side temperatures can range from ~ 300 °C to 1000 °C. Unfortunately, state-of-the-art Direct Thermal to Electric Conversion (DTEC) technologies fall far short of Carnot conversion efficiencies and, in many cases, do not exhibit sufficient power densities to meet mission requirements for many commercial and defense applications. DARPA's Direct Thermal to Electric Conversion Program seeks to address revolutionary advancements to the state-of-the-art in DTEC technologies that would significantly reduce the gap between achievable conversion efficiencies and Carnot efficiencies.
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