| Abstract |
Increased demand and requirements for sustainable geothermal operations in relation to gas emissions calls for a deep understanding of the primary criteria operators face when designing solutions. All geothermal fluids contain species that would be gases under certain temperatures and pressures. Such species, called non-condensable gas (NCG) include CO2, H2S, H2, N2, NH3, CH4. Some types of geothermal power plants don’t allow NCGs to evolve, thus do not vent or otherwise deal with NCG. Other types of plants have NCG that is in a gas phase. In these geothermal plants, NCG may be collected for use or other disposition (e.g., reinjection underground). This paper explains differences between types of geothermal power plants (e.g., condensing flash plants; back-pressure flash plants; binary plants), including their relative efficiencies, the situations under which each type is typically used, and relative costs. Then, the paper discusses how the type of plant affects disposition of the NCG. For example, collecting the NCG for use (or to eliminate venting) requires different considerations for the different types of geothermal power plants. The paper also reviews potential dispositions for NCG. For example, NCG could be re-injected back underground for sustainable operations. Alternately, species (e.g., CO2, H2S, perhaps H2) could be separated prior to venting the remaining NCG or sending the remainder elsewhere. The content should be useful for plant operators as well as those considering future geothermal developments. This paper is meant to contribute know-how from the IEA Geothermal Gas Management Task to enhance global research and geothermal development. |