(46b) Increased Stability of a Power Grid by Energy Storage of Cryogenic Carbon Capture

Increased concern over the trend of CO₂ emissions has led to several research studies for developing carbon capture technologies [1-6]. The main concern with carbon capture technologies is the energy consumption of the process, especially during peak electricity demand hours. Cryogenic carbon capture (CCC) is a technology that is under development to separate carbon dioxide by desublimation of CO₂from flue gas [7]. This technology consumes less energy than leading alternatives and provides rapidly responding energy storage potential that can stabilize changes in demand and fully utilize intermittent renewable supply. With energy storage of the CCC process, energy consumption of the capture process can be effectively shifted to periods when electricity demand is lower. Energy is then recovered from the storage system during peak hours. Energy recovery consists of: (1) reduced electricity consumption of the refrigeration compressors and (2) power generation in a gas turbine from the re-gasified natural gas refrigerant. The energy storage of the CCC process is shown in this study to positively impact the reliability and stability of a power grid. The current practice to achieve a reliable power grid is to have spinning reserves. Consequently, when demand increases or some of the power units unexpectedly go offline, the spinning reserves almost instantaneously come online. Because this happens occasionally, the spinning reserves have very low capacity factors, which in turn leads to very high average cost of power generation. Additionally, many spinning reserves are simple cycle gas turbines or diesel generators that have low efficiency or high fuel costs, respectively, compared to alternative power generation systems. It should also be emphasized that some of the spinning reserves are always online, regardless of the grid demand. Thus, the rapid increase in cost of power for the last increment of a cost versus cumulative grid operating capacity always exists, no matter what the power demand, and is attributed to the power production from spinning reserves. The energy storage portion of the CCC process, however, can effectively become the spinning reserve of the power grid by adjusting the parasitic load quickly to accommodate the dispatch schedule of the grid.

Previous work demonstrates the impact of energy storage on a single generation unit including the shift in the electricity consumption peak time for the CCC process [8-11]. This investigation studies the impact of energy storage portion of cryogenic carbon capture on the stability of a power grid. Load and generating plant data from 2010 is considered for the analysis of the Texas interconnection (ERCOT). ERCOT includes 96.5 GW of installed capacity with 5, 81, and 10.5 GW from nuclear, fossil fuels, and renewables, respectively. This grid-scale system is optimized using a mixed integer nonlinear programming solver (KNITRO) with GAMS on the NEOS Server. Historical data is used in this study, but data is manipulated to represent an event such as significantly high demand data or outage of a large generation unit over several time steps. It is observed that when a power generation unit goes offline, or a significant increase in the demand is anticipated, energy storage of cryogenic carbon capture adjusts the parasitic load in time to accommodate the dispatch schedule of the grid. In addition, power production from a gas turbine in which the fuel source is from the energy storage is also observed when an event occurs. Adjustment of the parasitic load of the CCC process and power production from the gas turbine result in reduced need for electricity generation from spinning reserves. Results show significant savings with energy storage of the CCC process compared to spinning reserves. Energy storage also results a more stable power grid by avoiding some potential brown-out scenarios due to sudden loss of a single generation unit or transmission line. Energy storage of cryogenic carbon capture also facilitates the transition from the current power grid systems to smart grids with larger contribution from renewable power sources [11]. In addition, management of the electricity load on the supplier side, achieved by energy storage, has the potential to be used throughout the year in which is an advantage over the residential demand response [11, 12]. The importance of such multi-functional plants significantly increases when the restrictive regulations for CO₂emissions become effective [13-14].

References:

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[3] S. M. Cohen, G. T. Rochelle, M. E. Webber, Optimizing post-combustion CO₂capture in response to volatile electricity prices, International Journal of Greenhouse Gas Control 8 (2012) 180-195.

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[7] Sustainable Energy Solutions Company, http://sesinnovation.com/

[8] S. M. Safdarnejad, J. D. Hedengren, L. L. Baxter, L. Kennington, Investigating the impact of cryogenic carbon capture on the performance of power plants, Proceedings of the American Control Conference (ACC),Chicago, IL, 2015.

[9] S. M. Safdarnejad, J. D. Hedengren, L. L. Baxter, Plant-level dynamic optimization of cryogenic carbon capture with conventional and renewable power sources, Applied Energy 149 (2015) 354-366.

[10] S. M. Safdarnejad, J. D. Hedengren, N. R. Lewis, E. L. Haseltine, Initialization strategies for optimization of dynamic systems, Computers & Chemical Engineering 78 (2015) 39-50..

[11] S. M. Safdarnejad, J. D. Hedengren, L. L. Baxter, Effect of Cryogenic Carbon Capture (CCC) on Smart Power Grids, Proceedings of the American Institute of Chemical Engineers (AIChE), Austin, TX, 2015.

[12] http://www.enernoc.com/our-resources/term-pages/what-is-demand-side-mana....

[13] Clean Power Plan enforced by EPA, Article 2013-28668, https://www.federalregister.gov/articles/

[14] Clean Power Plan enforced by EPA, http://www2.epa.gov/carbon-pollution-standards/fact-sheet-clean-power-pl...