CO₂ Thermosiphon for Competitive Geothermal Power Generation

Abstract

Engineered geothermal systems represent a significant unutilized energy source, with the potential to assist in meeting growing energy demands with clean, renewable energy. Traditional geothermal systems use water as the working fluid. An alternative working fluid is carbon dioxide which offers potential benefits including favorable thermodynamic and transport properties and the potential for sequestration. An important feature is that CO 2 does not dissolve mineral salts, and this will serve to reduce fouling and corrosion problems which afflict piping and surface equipment in conventional water cycles. Our modeling shows that a CO 2 -based power plant has net electricity production comparable to the traditional approach, but with a much simpler design, and demonstrates the comparative efficacy of CO 2 as a heat extraction and working fluid. While the economic viability of a CO 2 -based system remains to be proven, this analysis provides a starting point for more detailed thermodynamic and economic models of engineered geothermal systems power conversion utilizing CO 2 .