Comparison of different safety concepts for evaluation of molten salt receivers

Abstract

Solar power tower plants are a promising technology for renewable energy supply, because of their base load capability. Nevertheless, this type of power plant is in competition with various other technologies. In order to ensure the competitiveness of power tower plants, there are several approaches to reduce investment and operating costs. Huge amounts of these costs are defined in the lifetime calculation of the solar receiver. For this purpose, based on ASME BPVC Section III Division 5 (Nuclear Code), a number of safety concepts have been developed in the last decades, which are adapted to solar applications using reduced conservatism. However, a generally established approach has not yet been developed. Therefore, this study introduces a novel approach that makes it possible to directly compare the different safety concepts on the level of permissible strains and stresses. The comparison with these so-called interaction maps illustrates the range of variation of the allowable strains (factor of 1.5) and stresses (factor of 2.2), depending on the applied safety concept. Ultimately, a preferred method is identified that is both easy to apply, since it relies on generally available material data, and economically advantageous compared to the approach defined in the Nuclear Code. Additionally, it is demonstrated that the interaction maps can also be used for preliminary design of the receiver components. A change of the absorber material from the currently used nickel-based alloys to the significantly more cost-effective stainless steels offers options for an economically advantageous design, especially in the regions of low receiver temperatures. Introduction