Performance and economic optimization of hybrid solar thermal and photovoltaic power plants with dynamic simulation

Energy storage is a critical determinant of grid stability under scenarios with a high percentage of renewables in the generation portfolio. Concentrating solar thermal power traditionally offers high capacity thermal energy storage (TES) on timescales up to 24 hours, while photovoltaics operate with comparatively better economy but are limited to direct injection into the grid during the daytime in the absence of mature, high throughput battery storage technology. Obtaining the advantages of both systems through hybridization has been proposed in the ARPA-E FOCUS program, and this work investigates the performance and cost trade-offs of updating existing CSP infrastructure to include superimposed spectral filtering and concentrating photovoltaics in a linear optical configuration. A numerical energy balance model for a retrofit parabolic trough collector is deployed in an hourly simulation using plant characteristics and typical meteorological year (TMY) data for a location of interest. Design features including PV band pass filtering, operating temperature, and primary optics intercept are varied for an optimization of levelized cost of electricity. A case study for the US southwest illustrates the potential for performance enhancement relative to a CSP baseline via increased photovoltaic output (>30%), and favourable financial returns in comparison to greenfield PV plant development (with installed specific costs <1.5 USD/W), that preserves the advantages for grid operators of maintaining the dispatchability of TES.