A Hybrid Electric and Thermal Solar Receiver

Abstract

Solar energy offers a promising renewable energy source; however, it is expensive to store electricity from photovoltaics (PV), the most widely deployed solar electricity technology. Solar thermal energy technologies can be paired with inexpensive thermal storage, but are more expensive overall. We have developed a solar receiver that combines PV and solar thermal systems to efficiently convert solar radiation to electricity (to be used immediately) and thermal energy (to be stored and converted to electricity on demand). This paper describes the Hybrid Electric And Thermal Solar (HEATS) receiver and models its performance. An idealized model predicts high solar-to-electricity efficiency (35.2%) with high dispatchability (44.2% of electricity from thermal energy) at an operating temperature of 775 K. Modeling using measured performance values for HEATS subcomponents predicts 26.8% efficiency and 81% dispatchability with silicon PV and 28.5% efficiency and 76% dispatchability with gallium arsenide PV, both operating at 700 K. PV and solar thermal systems are the main methods for solar energy conversion. PV cannot utilize the entire solar spectrum, and it is expensive to store the generated electricity. Solar thermal systems convert sunlight to electricity using thermal energy as an intermediary, allowing the use of inexpensive thermal storage, but are more expensive than PV overall. Hybrid systems that convert some of the solar spectrum to electricity directly using PV and the rest to thermal energy can achieve higher efficiency than PV or solar thermal systems while allowing the use of thermal storage. Here, we introduce a stacked hybrid receiver design enabled by transparent aerogel and a spectrally selective light pipe. Modeling predicts a 35% solar-to-electricity conversion efficiency with further subcomponent improvement and >26% efficiency with the best subcomponent properties reported to date. Further development of this receiver could thus yield a high-efficiency option for solar energy conversion. We propose a Hybrid Electric And Thermal Solar (HEATS) receiver, which converts incident concentrated sunlight to both electricity and high-temperature thermal energy. Hybrid solar receivers that deliver electricity and thermal energy are promising because they can make better use of the entire solar spectrum than PV alone, and thermal energy can be stored inexpensively, allowing electricity generation when the solar resource is unavailable. The HEATS receiver is enabled by transparent silica aerogel and a spectrally selective light pipe.