An Adsorption-Compression Cold Thermal Energy Storage System (ACCESS)

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The cooling sector currently consumes around 14% of the UK's electricity and emits around 10% of the UK's greenhouse gases. Global electricity demand for space cooling alone is forecast to triple by 2050. Moreover, as air temperature increases, the cooling demand increases, but a refrigerator's Coefficient of Performance decreases. This results in a time mismatch between a refrigerator's efficient operation and peak cooling demand over a day. Clearly, this problem will deteriorate over the coming decades. Indeed, research by UKERC recently reported that cooling sector will cause a 7 GW peak power demand to the grid by 2050 in the UK. A solution is to employ cold thermal energy storage, which allows much more flexible refrigeration operation, thereby resulting in improved refrigeration efficiency and reduced peak power demand. Large-scale deployment of cold thermal energy storage could dramatically reduce this peak demand, mitigating its impact to the grid. Moreover, the UK curtails large amounts of wind power due to network constraints. For example, over 3.6TWh of wind energy in total was curtailed on 75% of days in 2020. Therefore, through flattening energy demand, cold thermal energy storage technology provides a means to use off-peak wind power to charge cold thermal energy storage for peak daytime cooling demand. This project, based on the proposed novel adsorption-compression thermodynamic cycle, aims to develop an innovative hybrid technology for both refrigeration and cold thermal energy storage at sub-zero temperatures. The resultant cold thermal energy storage system is fully integrated within the refrigerator and potentially has significantly higher power density and energy density than current technologies, providing a disruptive new solution for large scale cold thermal energy storage. The developed technology can utilise off-peak or curtailed electricity to shave the peak power demand of large refrigeration plants and district cooling networks, and thus mitigates the impacts of the cooling sector on the grid and also reduces operational costs.