Comparing post-combustion CO2 capture operation at retrofitted coal-fired power plants in the Texas and Great Britainelectric grids

Abstract

This work analyses the carbon dioxide (CO2) capture system operation within the Electric Reliability Council ofTexas (ERCOT) and Great Britain (GB) electric grids using a previouslydeveloped first-order hourly electricity dispatch and pricing model. The gridsare compared in their 2006 configuration with the addition of coal-basedCO2 capture retrofits and emissions penalties from 0 to 100 US dollars per metric ton ofCO2 (USD/tCO2).CO2 capture flexibility is investigated by comparing inflexibleCO2 capture systems to flexible ones that can choose between full- and zero-loadCO2 capture depending on which operating mode has lower costs or higher profits. Comparing thesetwo grids is interesting because they have similar installed capacity and peak demand, andboth are isolated electricity systems with competitive wholesale electricity markets. However,differences in capacity mix, demand patterns, and fuel markets produce diverging behaviours ofCO2 captureat coal-fired power plants. Coal-fired facilities are primarily base load in ERCOT for a large rangeof CO2 prices but are comparably later in the dispatch order in GB and consequentlyoften supply intermediate load. As a result, the ability to captureCO2 is more important for ensuring dispatch of coal-fired facilities in GB than in ERCOT whenCO2 prices are high. In GB, higher overall coal prices mean thatCO2 prices must be slightly higher than in ERCOT before the emissions savings ofCO2 capture offset capture energy costs. However, onceCO2 capture is economical,operating CO2 capture on half the coal fleet in each grid achieves greater emissions reductionsin GB because the total coal-based capacity is 6 GW greater than in ERCOT.The market characteristics studied suggest greater opportunity for flexibleCO2 capture to improve operating profits in ERCOT, but profit improvements can be offset by aflexibility cost penalty.