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General Atomics, under the Baseload CSP FOA, demonstrated the engineering feasibility of using a sulfur-based thermochemical cycle to store heat from a CSP plant and support baseload power generation.


There were three main project objectives under this award:

  • Study the sulfur generating disproportionation reaction and develop it into a practical engineering process step.
  • Carry out preliminary process components design and experimental validation. The engineering data will be used for process integration between the CSP plant, the sulfur processing and storage plant, and the electricity generation unit.
  • Demonstrate the economics and safety of a CSP plant integrated with sulfur storage.
Sulfur-based TES can compensate for diurnal and seasonal insolation fluctuations.


General Atomics developed a better thermal energy storage approach using a thermochemical cycle to convert solar energy into chemical bonds. In this case, the high temperature heat released via a change in the oxidation (combustion) state of the storage medium can be used to drive a gas turbine. This scheme does not rely on temperature gradient for heat recovery, and thus, solar heat can be stored indefinitely in the chemical bonds of the storage medium.


This project demonstrated the feasibility and economics of a CSP plant integrated with sulfur-based thermochemical storage. Key technical hurdles were addressed in this project, as the research team:

  • Defined the thermodynamic limits of SO2 disproportionation;
  • Greatly enhanced the SO2 disproportionation rate through the use of a catalyst and demonstrated pathways for its recovery and reuse; 
  • Established a scale up solar-receiver reactor design using on sun testing and modeling data;
  • Defined a path forward to obtain a robust decomposition catalyst;
  • Carried out a FMEA to demonstrate the safety of the proposed plant concept;
  • Designed a process flowsheet based on experimental and design data; and
  • Demonstrated the economic competiveness of the proposed concept.

A storage cost of $2/kWhth was obtained. The levelized cost of energy (LCOE) for the baseline conceptual sulfur TES process using a combined power cycle was determined to be at $0.087/kWhe. For a Rankine cycle, the LCOE was calculated to be in the range of $0.13-0.15/kWhe, similar to molten salt based system. 

Final Report

Wong, Bunsen. Sulfur Based Thermochemical Heat Storage for Baseload Concentrated Solar Power Generation. No. DE-EE0003588 (2014). doi: 10.2172/1165341 

Publications, Patents, and Awards

  • Wong, B., Thomey, D., Brown, L., Roeb, M., Buckingham, R., & Sattler, C. "Sulfur based thermochemical energy storage for concentrated solar power." ASME 2013 7th International Conference on Energy Sustainability collocated with the ASME 2013 Heat Transfer Summer Conference and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. doi: 10.1115/ES2013-18283 

  • R. Buckingham, B. Wong, L. Brown, C. Sattler, F. Schaube, and A. Woerner. "Metal Oxide Based Thermochemical Energy Storage for Concentrated Solar Power–Thermodynamics and Parasitic Loads for Packed Bed Reactors," Proceedings of 16th Annual SolarPACES Conference, Granada, Spain, 2010.

Learn about other DOE competitive awards for concentrating solar power research that are in progress.