A techno-economic comparison between piston steam engines as dispatchable power generation systems for renewable energy with concentrated solar harvesting and thermal storage against solar photovoltaics with battery storage

Abstract

Given its abundance and distribution, solar electricity is clearly the power source of the future. Solar photovoltaics is currently the favoured electricity production technology but high battery costs limit its use as a truly dispatchable solution. Solar thermal electricity, with higher production costs but lower heat storage costs, is an important alternative. In this work we have compared solar thermal and solar photovoltaic renewable energy systems head to head: using simulations with our own models and the latest information from literature. The solar thermal system uses a Uniflow Piston Steam Engine for electricity production. The analysis incorporates the daily variance in electricity demand in the form of the CAISO duck curve. To supply off grid demand, if natural gas driven engines produce electricity at $0.134/kWh, photovoltaics with battery storage can supply it at 0.159 $/kWh (0.107 $/kWh best case) and solar thermal with piston steam engines can supply at 0.144–0.167 $/kWh at current prices. If solar concentrator prices drop to $75/m2-aperture, as seems promising, solar thermal can supply dispatchable electricity at 0.091–0.103 $/kWh. In view of the declining interest in solar thermal electricity, this is a valuable contribution to the conversation about the relative merits of the two technologies.