Extended emission footprint analysis of dispatchable gas-based power generation technologies with exhaust aftertreatment technologies

Abstract

The mitigation of climate change poses severe pressure on the rapid replacement of conventional power generation technologies by renewables. Due to the inherent volatility of renewable power generation technologies, dispatchable power generation units, such as gas turbines (GT) and gas-based reciprocating internal combustion engines (RICE), must be operated to maintain grid stability. While RICE are equipped with exhaust aftertreatment (EAT) technologies as standard to meet regulatory emission limits, this may also become important for GT in the near future. The present study therefore investigates the influence of EAT on emissions, taking into account oxidation catalysts (OC) and selective catalytic reduction (SCR) catalysts. Single-cycle power plant configurations for both technologies are studied under different operation scenarios, with emphasis on start-ups and partial load operation. Emissions are assessed as “generated mass per electrical output” (g=kWhel), considering both greenhouse gases and local pollutants. To holistically assess the environmental footprint, emissions are converted into impact categories such as Global Warming Potential (GWP), Respiratory Inorganics (RI), Photochemical Ozone Formation (POF) and Human Toxicity Potential (HTP). The increasing variability of operation demands of gas-based power generation technologies leads to a significant increase of emissions and environmental impact without EAT, highlighting the overall need for EAT systems to meet regulatory limits in the future. Both technologies show a significant reduction in the environmental impact factors (RI: > 46 %, POF: > 87 %, HTP: > 86 %) with EAT deployment in all load profile scenarios. With CO2 largely unaffected by EAT, RICE has a lower GWP100 than GT for all load scenarios (-2.6 to -11.4 %) because of the higher average plant efficiency. Due to their modularity, RICE plants can be operated over most of the plant load range without excessive emissions, whereas GT plants are limited to operation above 30 %.