UC Irvine

Proton exchange membrane electrolyzers (PEMEZ) are an attractive technology choice as the principal piece of equipment in power-to-gas (P2G), however their usage within the context of P2G has not yet been thoroughly investigated, and no pilot plants for power-to-gas with PEMEZ have as yet been realized in the United States. In this study, a PEM electrolyzer was modified to have dynamic dispatch capabilities, then subsequently operated and studied in detail as a part of the UC Irvine P2G demonstration. The system operated at sustained part load conditions and load followed variable renewable energy resources. Furthermore, the impact on emissions due to the addition of hydrogen to the high pressure natural gas fuel feed to the University of California Irvine (UCI) Central Plant’s combustion turbine is analyzed.

Solar PV load following was found to have minimal impact on system efficiency in producing hydrogen from electrolysis, however wind load following did result in sustained low load conditions that did impact system efficiency significantly. Reduced efficiency due to sustained low part load conditions could be circumvented by cycling PEMEZ off completely and starting up as the load signal reached the minimum effective point again. The effective compression of hydrogen electrochemically in the PEMEZ was demonstrated to nearly match the efficiency of ideal isothermal compression using a semi-empirical model developed from sustained part load operation testing of the PEMEZ.

Addition of hydrogen to the natural gas fired combustion turbine showed very little likelihood of impact on emissions of criteria pollutants (CO, NOx). A slightly significant correlation between reduction in natural gas usage, and by extension emissions of CO2, was noted.