Thermal battery with CO2 compression heat pump: Techno-economic optimization of a high-efficiency Smart Grid option for buildings

Increasing penetration levels of wind and solar power in the energy system call for the development of Smart Grid enabling technologies. As an alternative to expensive electro-chemical and mechanical storage options, the thermal energy demand in buildings offers a cost-effective option for intermittency-friendly electricity consumption patterns.Combining hot and cold thermal storages with new high-pressure compressor technology that allows for flexible and simultaneous production of useful heat and cooling, the paper introduces and investigates the high-efficiency thermal battery (TB) concept. In a proof-of-concept case study, the TB replaces an existing electric resistance heater used for hot water production and an electric compressor used for air refrigeration in a central air conditioning system. A mathematical model for least-cost unit dispatch is developed. Heat pump cycle components and thermal storages are designed and optimized. A general methodology is applied that allows for comparing the obtained results with other Smart Grid enabling options.It is found that the TB concept leads to improvements in the intermittency-friendliness of operation Rc (improves from −0.11 to 0.46), lower CO2 emissions (reduced to zero), and lower operational costs (reduced by 72%).The results indicate that TB may be the most cost-effective Smart Grid enabling option for supporting higher penetration levels of intermittent renewables in the energy system.

► We present a Smart Grid enabling concept for integrated heating and cooling supply
► The thermal battery combines a CO2 heat pump with hot and cold thermal storages
► We develop a mathematical model for economic unit dispatch
► We implement and apply the model for a proof-of-concept case study
► Significant benefits are found for intermittency-friendliness, costs, and emissions.