Turning CO2 Capture On and Off in Response to Electric Grid Demand: A Baseline Analysis of Emissions and Economics
- 17 May 2010
- journal article
- Published by ASME International in Journal of Energy Resources Technology
- Vol. 132 (2), 021003
- https://doi.org/10.1115/1.4001573
Abstract
Coal consumption accounted for 36% of America’s emissions in 2005, yet because coal is a relatively inexpensive, widely available, and politically secure fuel, its use is projected to grow in the coming decades (USEIA, 2007, “World Carbon Dioxide Emissions From the Use of Fossil Fuels,” International Energy Annual 2005, http://www.eia.doe.gov/emeu/iea/carbon.html). In order for coal to contribute to the U.S. energy mix without detriment to an environmentally acceptable future, implementation of carbon capture and sequestration (CCS) technology is critical. Techno-economic studies establish the large expense of CCS due to substantial energy requirements and capital costs. However, such analyses typically ignore operating dynamics in response to diurnal and seasonal variations in electricity demand and pricing, and they assume that capture systems operate continuously at high removal and permanently consume a large portion of gross plant generation capacity. In contrast, this study uses an electric grid-level dynamic framework to consider the possibility of turning capture systems off during peak electricity demands to regain generation capacity lost to capture energy requirements. This practice eliminates the need to build additional generation capacity to make up for capture energy requirements, and it might allow plant operators to benefit from selling more electricity during high price time periods. Post-combustion absorption and stripping is a leading capture technology that, unlike many other capture methods, is particularly suited for flexible or on/off operation. This study presents a case study on the Electric Reliability Council of Texas (ERCOT) electric grid that estimates capture utilization, system-level costs, and emissions associated with different strategies of using on/off capture on all coal-fired plants in the ERCOT grid in order to satisfy peak electricity demand. It compares base cases of no capture and “always on” capture with scenarios where capture is turned off during: (1) peak demand hours every day of the year, (2) the entire season of peak system demand, and (3) system peak demand hours only on seasonal peak demand days. By eliminating the need for new capacity to replace output lost to capture energy requirements, flexible capture could save billions of dollars in capital costs. Since capture systems remain on for most of the year, flexible capture still achieves substantial emissions reductions.
Keywords
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