CO2 emission assessment of the geothermal power station Los Humeros, Mexico

Abstract

This work presents the estimation of the CO2eq emissions of the geothermal power station in Los Humeros, Mexico. The calculation takes the emissions of the CO2 contained on the extracted geothermal brine plus the CO2 footprint by the power station construction. The carbon footprint estimation is based on technical reports generated by the owner company. It considers all the commissioning activities and also the operational phase of the power plant, which is assumed to span a lifetime of 30 years. The results indicate a total emission from 442 to 568 gCO2eq/kWhel. Of these emissions 9 to 12% are contributed indirectly by the power station construction whereas 88 to 91% are released directly during operations due to the natural content of CO2 in the steam. When comparing the results with the natural discharge of CO2 in the production area, the emissions of CO2eq is 10 times faster. Solutions are proposed to reduce the footprint of CO2eq per kWhel. In the short term the use of all the installed capacity in the field reduces the footprint by 25%. Another option is to use closed cycle technology with a binary power station instead of the single-flash power plants. This showed 82% reduction of CO2eq emissions; accompanied by a reduction of electricity production by 16% due to the lower conversion efficiency.