Make every kilowatt count: Modeling solar power integration with thermal storage and heating electrification

Abstract

Solar photovoltaic (PV) power is expected to supply a large share of renewable electricity in future energy systems. However, scaling up solar PV in isolation is insufficient to achieve net-zero targets due to challenges such as supply variability, demand-supply mismatch, and grid constraints. Additional measures like heating electrification, storage, flexibility, and local energy management are needed. While most studies either focus on individual case studies or aggregate the national energy system into a single entity, this work combines municipality-level resolution with a nationwide assessment. Using an hourly multi-energy system model, we simulate the energy systems of 2131 Swiss municipalities to assess the impact of solar PV expansion with and without complementary measures. Alongside PV expansion, we study the effects of replacing 50% of fossil-based heating with heat pumps (HP) and implementing thermal energy storage (TES) sized up to 20% of annual heat demand. At the national scale, emissions decrease by 40%, and the renewable share increases from 43% to 66%. The largest improvements result from replacing fossil heaters with HPs, which lower emissions and absorb additional PV generation. TES further increases renewable utilization by shifting HP demand to periods of high PV yield. At the municipal scale, the impact of each measure depends strongly on existing PV capacity and demand profiles. In municipalities with high PV implementation, HP and TES deliver larger benefits than further PV expansion alone. The findings show that PV expansion must be combined with system integration measures to achieve substantial emission reductions and higher renewable supply.