Abstract

The challenge in solar energy today is not the cost of photovoltaics (PVs) electricity generation, already competing with fossil fuel prices, but rather utility-scale energy storage costs. Alternatively, low cost thermal energy storage (TES) exists, but relies on expensive concentrated solar power (CSP). A photovoltaic/thermal (PV/T) technology, able to efficiently unify PV conversion and TES, may usher in the era of efficient base-load renewable power plants. Spectral splitting, one PV/T option where inefficient photons for PV conversion are redirected and thermally utilized, is economically limited by the low yield of each generator. Operating PVs at high temperatures while utilizing the thermalization induced heat for the thermal cycle is another possibility; yet, while conceptually supporting full utilization of solar thermal and free energy, it too is limited by PV efficiency reduction with temperature increase. Here we introduce the concept of luminescence solar power (LSP), where sunlight is absorbed in a photoluminescent (PL) absorber, followed by red-shifted PL emission matched to an adjacent PV band-edge. The PL absorber temperature rises due to thermalization, allowing spatial separation between heat and free-energy, for maximal harvesting of both. We solve the material challenge by experimentally demonstrating tailored luminescence with PL efficiency of up to 90% while operating at 600oC. At such high temperatures, LSP efficiency offers a 50% enhancement over conventional side-by-side PV/CSP efficiency under real-world conditions, leading to a potential reduction in solar energy storage levelized cost of electricity (LCOE) to below 3¢/kWh. Such a low LCOE complies with the 2030 SunShot goal, enabling future US solar energy production to reach 50%.

© 2019 IEEE

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