Determination of energy storage scheme for hybrid photovoltaic-assisted heating system in residential buildings

Photovoltaic (PV)-assisted heating systems can meet residential electrical and thermal demands using heat storage (HS) or Li-ion battery (LB) storage. However, identifying the appropriate storage scheme under different solar-resource and building-load conditions remains challenging at the design stage. This study proposes a storage-selection framework integrating two indicators: the Available Irradiance-to-Power Load Ratio ( AIPL ), which characterizes the overall solar-resource availability relative to the building’s equivalent electrical demand, and the Electricity-to-Heat load ratio ( E2H ), which describes the electrical-thermal load structure. A multi-objective optimization model balancing economic cost and carbon emissions is developed, and its applicability is examined for five Chinese cities with different climatic conditions. The results show that HS is more competitive at relatively low AIPL , whereas LB becomes more competitive as AIPL increases. As E2H increases from 1:3 to 3:1, the critical AIPL decreases from 0.540 to 0.361, indicating an expanded applicability region for LB under electricity-predominated conditions. The five-city analysis reveals broadly consistent applicability patterns across the various climatic conditions. Sensitivity analysis further demonstrates that battery cost, heat pump performance, and objective-function weights influence the applicability boundary. The proposed AIPL-E2H indicators and solution framework support preliminary storage-scheme selection under different climatic conditions and building load structures.