Domestic thermal energy storage applications: What parameters should they focus on?

Abstract

Thermal energy storage (TES) is required to allow low-carbon heating to meet the mismatch in supply and demand from renewable generation, yet domestic TES has received low levels of adoption, mainly limited to hot water tanks. Current reviews and studies primarily focus on the comparison of storage materials neglecting the performances at a system level and analysis studies tend to solely look at hot water tanks, missing the key technology developments in thermal storage systems which are under development. Therefore, this paper investigates performance and cost variations of TES from material-level to system-level analysis and assesses impacts of emerging heat storage technologies. By simulating different types of TES materials and varied system integration options, a significant reduction in energy densities and increase in specific costs of TES systems were found compared to the material-level analysis. Direct electrical heating has much greater potential to integrate with TES from its high operating temperature with TES compared to heat pumps or solar thermal which are constrained to lower temperatures. TES properties are simulated in various scenarios in a domestic heating techno-economic framework. It was found that for heat pumps there is economically-limited potential for TES, even if very high energy densities are possible. In addition, the priority for TES coupling with heat pumps is low capital cost, although current high tariff rates due to the energy-crisis do improve economic viability of TES. On the other hand, with direct electrical heating, high energy density is the most valuable parameter for TES, as it allows significant quantity of demand to be shifted to very low-tariff times, in particular for low demand dwellings where negligible amounts of peak electricity could be required for heating.