A Cost‐Performance Analysis of a Sodium Heat Engine for Distributed Concentrating Solar Power

Abstract A sodium thermal electrochemical converter (Na‐TEC) generates electricity directly from heat through isothermal expansion of sodium ions across a beta″‐alumina solid‐electrolyte. This heat engine has been considered for use with conventional concentrating solar power (CSP) systems before. However, unlike previous single‐stage devices, the improved design uses two stages with an interstage reheat, allowing more economical and efficient conversion up to 29% at a hot side temperature of 850 °C. Herein, a cost‐performance analysis for this improved design assesses opportunities for distributed‐CSP in the context of micro‐combined heat and power systems. A high‐level techno‐economic analysis (TEA) is presented that explores four scenarios where a Na‐TEC is used as the heat engine for a distributed‐CSP system. Overnight capital cost and levelized cost of electricity (LCOE) are estimated for a system lifetime of 30 years, revealing that overnight capital costs in a range from $3.57 to $17.71 per W_e are feasible, which equate to LCOEs from 6.9 to 17.2 cents kWh_e⁻¹. This analysis makes a significant contribution by concurrently quantifying the efficiency and unit costs for a range of multistage configurations, and demonstrating that a Na‐TEC may be a promising alternative to Stirling engines for distributed‐CSP systems at residential scale of 1–5 kW_e.