A general method to analyze the thermal performance of multi-cavity concentrating solar power receivers

Concentrating solar power (CSP) with thermal energy storage has potential to provide grid-scale, on-demand, dispatchable renewable energy. As higher solar receiver output temperatures are necessary for higher thermal cycle efficiency, current CSP research is focused on high outlet temperature and high efficiency receivers. The objective of this study is to provide a simplified model to analyze the thermal efficiency of multi-cavity concentrating solar power receivers. The model calculates an optimal aperture flux that maximizes the local efficiency, constrained by a maximum receiver working temperature. Using this flux, the thermal efficiency, receiver temperature, and heat transfer fluid (HTF) temperature are calculated based upon an optimized flux distribution. The model also provides receiver design and HTF heat transfer requirements to achieve the necessary overall thermal efficiency. From the results, possible HTFs can be investigated to determine which ones are feasible. A case study was performed on a multi-cavity tube receiver design to demonstrate the use of the model. The case study receiver design had an effective absorptivity of 99.8%, and was modeled with conservative values for thermal constraints. It was found that a HTF with a minimum convection coefficient between 250 and 500 W m⁻² K⁻¹, depending on the convective heat transfer to the environment, is necessary to achieve a thermal efficiency greater than 90% for the receiver. The general model can provide a design guideline for attainable thermal efficiencies of multi-cavity concentrating solar power receivers given thermal constraints and heat transfer conditions.