Abstract
Solar thermal, thermoelectric, and thermophotovoltaic (TPV) systems have high maximum theoretical efficiencies; experimental systems fall short because of losses by selective solar absorbers and TPV selective emitters. To improve these critical components, we study a class of materials known as cermets. While our approach is completely general, the most promising cermet candidate combines nanoparticles of silica and tungsten. We find that 4-layer silica-tungsten cermet selective solar absorbers can achieve thermal transfer efficiencies of 84.3% at 400 K, and 75.59% at 1000 K, exceeding comparable literature values. Three layer silica-tungsten cermets can also be used as selective emitters for InGaAsSb-based thermophotovoltaic systems, with projected overall system energy conversion efficiencies of 10.66% at 1000 K using realistic design parameters. The marginal benefit of adding more than 4 cermet layers is small (less than 0.26%, relative).
Highlights
Solar thermal, solar thermoelectrics, and solar thermophotovoltaics (TPV) offer three potentially high-efficiency paths for converting sunlight into electricity
We examined the basic physical mechanism for the operation of selective absorbers and emitters based on cermets
We explored a wide range of metals and dielectric materials that could be employed in fabricating a high-performance design, and suggested a combination of tungsten and silica is optimal
Summary
Solar thermoelectrics, and solar thermophotovoltaics (TPV) offer three potentially high-efficiency paths for converting sunlight into electricity. In the case of solar TPV, as illustrated, the selective absorber is thermally coupled to a selective emitter, which thermally radiates onto a nearby TPV cell capable of converting photons above the TPV bandgap energy directly into electricity [5,6,7,8]. The advantage of these approaches over traditional solar photovoltaics (PV) is that they can avoid two major sources of PV loss: thermalization of high-energy photons and reflection of lowenergy photons. A substantial amount of loss has been observed to occur both in selective solar absorbers as well as selective emitters, under conditions of low concentration or high operating temperatures [10]
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