Methods for Rejecting Daytime Waste Heat to Outer Space
One need go no further than the ﬁrst paragraph of any article on solar energy technology to confront the mind-boggling scale of the available energy resource. The deployment of solar technology has experienced incredible growth in the past decade. This deployment has been dominated by single-junction silicon photovoltaic (PV) technology. These devices are characterized by a single bandgap, which is unable to convert a signiﬁcant fraction of the incident solar spectrum. The Shockley-Queisser efﬁciency limit for single bandgap silicon PV devices is 32.2%, accounting both thermal losses of photons below and greatly above the bandgap and radiative recombination losses, and deployed systems experience a much lower conversion efﬁciency. Besides conversion efﬁciency, another barrier to ever-increasing solar penetration is the lack of cost-effective grid-scale electricity storage technologies, since storage is necessary for solar electricity to be available overnight or during extended periods of clouds.