Economic evaluation of a novel fuel-saver hybrid combining a solar receiver with a combustor for a solar power tower

The novel concept of a hybrid receiver–combustor, HRC, is presented, in which the functions of a solar-receiver and a combustor are combined into a single device. An economic assessment of this concept is then performed for a solar power tower electricity generating plant employing molten salt technology, to evaluate the conditions under which an economic benefit can be derived. The HRC is compared with an equivalent well-known concept of Solar Gas Hybrid, SGH, with otherwise of identical specifications, for both 1h and 13h of thermal storage capacity and also with an equivalent stand alone solar power tower, SPT, and a gas-only boiler. All hybrid configurations are designed to provide 100% of the electrical demand continuously, i.e. to operate in the fuel-saver mode. Costs of each configuration are compared for a constant size of power block and also for a constant size of heliostat field using a consistent and well established cost-estimating methodology. On the assumption that the HRC achieves the same combustion efficiency as the boiler for twice the capital cost of a solar receiver, the HRC is found to reduce both the overall capital cost and the levelized cost of generating electricity relative to the equivalent hybrid. The benefit is attributed to the increased sharing of infrastructure and to allowing a slightly smaller heliostat field size for the case of the same size of power block. The HRC has the additional benefit of reduced operation and maintenance due to reduced thermal cycling and of reduced thermal shock, although these are not included here owing to a lack of data with which to evaluate it reliably.