Concentrated solar thermalProject Improving Solar-Thermal Receivers for Reduced Heat Loss
This project focussed on improving the performance of tubular molten salt receivers, which have been the preferred receivers for several large-scale systems such as the Gemasolar, Crescent Dunes and Noor III solar towers.
In concentrating solar power (CSP), the receiver is the part of the system where concentrated sunlight is absorbed and converted to heat, which in turn heats up a working fluid that is being pumped through the receiver. This fluid conveys the thermal energy to the rest of the system, where it can be stored and eventually used to produce electricity or to provide heat to other kinds of industrial processes.
This project focussed on improving the performance of tubular molten salt receivers, which have been the preferred receivers for several large-scale systems such as the Gemasolar, Crescent Dunes and Noor III solar towers. The properties of the molten salt material are such that the temperature range is limited to 290–565°C, and the flux incident on the receiver tubes cannot exceed certain limits due to excessive thermal stresses in the tubes, and chemical degradation of the salt material.
In this project, a concept to overcome the flux limits in molten salt receivers was proposed. The concept was to rearrange the banks of tubes that make up the solar-thermal receiver into ‘bladed’ structure, similar to a louvred window. This configuration allows a much larger tube surface area to be squeezed into a specified receiver aperture area, hence allowing a much higher aperture flux for a given tube-surface flux limit. A bladed structure would be modular, in contrast with cavity receiver designs that are more commonly considered, and could be repeated many times across a large receiver without resulting in an excessively large size. The bladed structure would also have improved light-trapping properties, and decreased convective heat loss, due to the cavity-like structures that would impede the flow of air over the hottest parts of the structure.