Efficiency improvement in CO2 capture solvent regeneration using a load leveling electricity to thermal energy absorption strategy

The proposed technology improves power plant efficiency by load leveling, reducing cost and energy demand for the CO2 capture process. The technology is particularly relevant to baseload coal combustion power plants, providing the core of Kentucky's energy infrastructure. Typically, during valley demand the baseload plant reduces output from optimum efficiency. However, during peak demand an alternate, intermittent power supply (typically a simple cycle gas turbine) is brought online to ensure customer demands are met. Load leveling enables optimal baseload plant efficiency at all times. Described here is a technology that returns excess energy produced during valley demand back to the plant as thermal energy during peak demand. Advantageously, the heat generated could be used to regenerate a CO2 capture solvent. This would reduce the plant parasitic load from the carbon capture technology allowing this electricity to be supplied to the customer. The method maximizes efficiency of the coal combustion plant, maximizes the use of coal as a low cost readily available fuel source, and minimizes cost to build and maintain peak production capacity. The technology also reduces cost for CO2 capture since less investment is needed in makeup power to meet peak demand, as much as 30% reduction in net plant output is used for CO2 capture. Load leveling is accomplished here by using an energy absorption system that can be used to capture electrons from baseload coal power plants during periods of valley demand. The technology utilizes molten salt solution electrolysis allowing high stored energy density. The process will be capable of expelling thermal energy (when the potential is removed) which would be used to provide steam for power plant processes during peak electricity demand. A high temperature process (500 °C) could provide heat to the feedwater heater to reduce steam extraction. More importantly, a lower temperature steam (150 °C) generated using this method could be used to regenerate CO2 capture solvents. The working electrolysis cell consists of an anode, a cathode, and an electrolyte. The cell does not require a salt bridge or separation membrane which greatly reduces the cost, increases the simplicity, and increases the safety (intrinsically safe as maximum heat is design heat, unlike a battery. The key advantages over other methods are the potential high efficiency (> 95%) and energy density (not limited by surface area). A possible example of the chemical reactions to enable the process would consist of a lead cathode with a carbon (non-reactive) anode. The electrolyte is a molten Zn2+ solution. During excess electricity production the electrochemical cell will have a voltage applied to oxidize the lead (Eo = -0.13) at the cathode and reduce the zinc (Eo = -0.76) at the anode. Once the potential is removed the reaction spontaneously forms Zn2+ and lead metal. Preliminary calculations predict a specific energy and energy density of 168 Wh/kg and 468 Wh/L respectively. This would yield a significant improvement compared to a Zinc-Bromide flow battery (50Wh/kg and 40 Wh/L), which most closely compares to the described technology.