Systems integration of concentrator photovoltaics and thermoelectrics for enhanced energy harvesting

Abstract

Alongside other photovoltaic technologies, Concentrator photovoltaics (CPV) capitalise on the recent progress for high-efficiency III:V based multi-junction photovoltaic cells, combining them with low cost optics for increased power production. Thermoelectrics are semiconductor devices that can act as solid-state heat pumps (Peltier mode) or to generate electrical power from temperature differentials (Seebeck effect). In this work, new designs for the integration of a thermoelectric module within a CPV cell receiver were proposed and substantiated as a reliable and accurate temperature control platform. The thermoelectric was used for accurate and repeatable cooling, exhibiting high temporal-thermal sensitivity. Testing was done under varying irradiance and temperature conditions. A novel Closed Loop Integrated Cooler (CLIC) technique was tested, demonstrated and validated as a useful experimental metrology tool for measuring sub-degree cell temperature within hybrid devices using the material properties of the thermoelectric module. Proof-of-concept circuitry and a LabVIEW based deployment of the technique were designed built and characterised. The technique was able to detect thermal anomalies and fluctuations present when undertaking an I-V curve, something otherwise infeasible with a standard k or t-type thermocouple. A full CPV-TE hybrid module with primary and secondary optical elements (POE-SOE-CPV-TE) was built using a further optimised receiver design and tested on-sun for evaluation under outdoor operation conditions in southern Spain. A unique TE-based “self-soldering” process was investigated to improve manufacture repeatability, reproducibility and minimise thermal resistance. A manually-tracked gyroscopic test rig was designed, built and used to gain valuable outdoor baseline comparison data for a commercially available CPV module and a Heterojunction Intrinsic Thinlayer (HIT) flat plate panel with the POE-SOE-CPV-TE hybrid device. An energetic break-even between the power consumed by the TE and the power gain of the CPV cell from induced temperature change was experimentally measured. This work demonstrated the unique functionalities a thermoelectric device can improve CPV power generation. The potential of a TEM to improve CPV power generation through active cooling was highlighted and quantified