Economic impact of thermal energy storage on natural gas power with carbon capture in future electricity markets

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As policies evolve to reflect climate change goals, the use of fossil fuel power plants is expected to change. Many fossil fuel power plants may opt to incorporate carbon capture and storage (CCS) technologies in response to evolving emissions policies. Additionally, fossil plants may need to be operated flexibly to accommodate the growing concentration of renewable energy systems. Unfortunately, most CCS technologies are very expensive, and they impose a parasitic load on the power plant, thereby decreasing net power output and the ability to operate flexibly. This investigation evaluated the economic potential of using hot and cold thermal energy storage (TES) to supplement the peak power output and flexibility of a natural gas combined cycle (NGCC) power plant with CCS capabilities. The two TES subsystems (hot and cold) were charged during periods of relatively low electricity prices and discharged during NGCC operation: resistively heated hot TES to offset the CCS parasitic heat load and vapor compression cooled cold TES to chill the inlet air to the power plant. Thermodynamic models were created for the base NGCC + CCS power plant, the hot TES equipment, and the cold TES equipment, to determine key performance and cost parameters such as net power output, fuel consumption, emissions captured, capital costs, and operational costs. These parameters were then used to simulate the operation of the power plant with and without the TES technologies in accordance with fourteen electricity pricing structures predicted for different future electricity market scenarios. The difference in net present value (NPV) between the base NGCC + CCS power plant and power plant with the TES technologies was used as the primary economic metric in this analysis. The NPV benefit from increased revenue due to TES utilization was found to outweigh the NPV penalty from the additional capital costs. This economic result was attributed to the low cost of the TES equipment and the ability to charge the storages using cheap electricity from high levels of renewable output. The results have shown that hot TES increased NPV in 12 of 14 market scenarios while the cold TES increased NPV in 14 of 14 market scenarios. A combination of both hot and cold TES yielded the largest increases in NPV.