Novel thin film thermophotovoltaic system

Abstract

We describe a novel design of a thermophotovoltaic (TPV) system based on thin film photocells. The radiation source is a selective emitter made from Yb 2O 3, which allows the use of photocells with a band gap between 1.0 and 1.2 eV. Thin film solar cell materials like microcrystalline Si or Cu(In,Ga)Se 2 (CIGS) can in principle be used for such a system. So far, a special CIGS TPV photocell is not available, but the requirements to the cell for an application in a TPV system, like suitable band gap, small series resistance, flexibility and superstrate configuration, were separately achieved in lab-scale photocells. The proposed thin film TPV system is cylindrically symmetric and consists of a monolithic CIGS photocell module at the outer surface of a glass tube. Due to a direct contact of the whole rear side of the cell with a cooling water film, an efficient cell cooling is achievable. Complicated cooling water plumbing is not necessary. A drastic cost reduction is expected compared to TPV systems that use conventional crystalline Si photocells. Numerical simulations of the novel CIGS TPV system based on an existing system with Si photocells and CIGS photocell parameters from the literature result in a system efficiency of up to 4% without recuperator. We suggest an application of our proposed system for electrically self-powered residential heating systems. For that, a system efficiency of 1–2% is sufficient, so surplus electricity can be supplied into the house grid for external consumption.