Integrating lithium-ion and thermal batteries with heat pumps for enhanced photovoltaic self-consumption

A promising solution to fully decarbonize the energy consumption of buildings consists of hybridizing solar PV installation with lithium-ion (Li-ion) batteries and heat pumps. However, the high capital cost per unit of energy storage of Li-ion batteries often results in systems with relatively small storage capacities, leading to low selfconsumption ratios. Thermal batteries with power generation capacity, such as Power-to-heat-to-power storage (PHPS), leverage the significantly lower cost of thermal energy storage to increase the overall storage capacity of the system. In addition, PHPS systems generate heat as a by-product during the energy conversion, which can be used directly in the building to supply its heating demand. The goal of this study is to assess the profitability of integrating PHPS systems with heat pumps and Li-ion batteries. A techno-economic analysis, based on a fully-electrified building, demonstrates that the hybridization of PHPS and Li-ion batteries yields the lowest levelized cost of consumed energy, regardless of the coefficient of performance (COP) of the heat pump. This hybrid configuration takes advantage of the lower cost of the energy subsystem of PHPS, which is mostly used for baseload power generation (long duration discharge), and the higher efficiency and lower cost of power capacity of Li-ion batteries, which are optimized for peak power generation (short-duration discharge). Under the assumptions of this study, hybrid solution reduces the levelized cost of consumed energy by 7 % compared to a system relying solely on Li-ion batteries, while simultaneously increasing PV self-consumption by up to 20 %.