Optimum combination of diesel and concentrating solar in remote area power generation using supercritical CO2 turbines

Abstract

Electrification of remote communities is a great challenge worldwide. Their reliance on economically and environmentally unfavourable diesel generators makes these communities attractive target markets for renewables. Concentrating solar thermal (CST) plants operating on supercritical CO2 (s-CO2) Brayton power cycles have been proposed for their high efficiency, compactness, compatibility with natural air-cooling, and capability of being built at a small size without significant efficiency penalties. Thermal energy storage (TES) technology can mitigate intermittency problems. This study aims to identify the optimal configuration of hybrid CST and diesel generation (DG) for different types of remote locations based on annual simulations involving key system design features including solar multiple, TES size, and CST size. One novelty in this study is the inclusion of actual weather information and load demand profiles for selected potential locations. Another is that a realistic economic model for s-CO2 power blocks for small to medium sizes, based on accurate cost data, is presented. More importantly, a realistic representation of the s-CO2 turbine, which includes isentropic efficiencies varying at off-design conditions, is used. This facilitates a study into the effects that the inclusion of realistic off-design turbine information has on the thermodynamic and techno-economic performances of the system. This is done by comparing the simulation results with results obtained using a conventional method that uses a constant turbine efficiency. This paper presents the optimal system configurations offering the lowest levelised cost of energy (LCOE) obtained using three-variable exhaustive search optimisation. The results show that the system is an economically favourable option and provides substantial environmental benefits.