Experimental investigation on thermal performance of cavity receiver integrated with short-term thermal energy storage for a solar parabolic dish concentrator

Solar parabolic dish collectors are widely used for solar thermal energy conversion for various medium- and high-temperature applications. One of the problems being faced by the receivers of parabolic dish collectors is the short-time non-availability of solar radiation because of cloud cover. This affects the useful output and also results in a sudden change in the receiver temperature, which induces thermal stress in it. Hence receiver with short-term thermal energy storage is attempted to tackle this issue. A hemispherical cavity receiver is developed with a double-layered wall, and the space between the two layers is filled with a salt bath composed of a eutectic mixture of NaNO3 and KNO3 as phase change material. The heat transfer fluid flows through the copper tubes that are coiled in the gap between the two layers. The phase change material surrounds the copper tubes and acts as a storage as well as a heat transfer medium. Experimental results show that the integration of the storage medium to the receiver has a good impact on the thermal output, even during irregular radiation input conditions. The receiver has attained a net energy efficiency of 31.4% for an average irradiance of 561 Wm(-2).