Solar-assisted high-temperature heat pumps to achieve off-grid zero-carbon heating in industrial parks

Industrial heating constitutes over half of global energy use, posing a major barrier to deep decarbonization. Solar energy, as a flexible and cost-effective renewable source, is ideal for off-grid power and heat in industrial parks. This study constructs and evaluates four solar-assisted pathways for delivering industrial heating by electrified heating: i) water-based photovoltaic-thermal with electric boiler (PV/T-EB), ii) water-based PV/T with high-temperature heat pump (PV/T + HTHP), iii) PV/T-direct-expansion heat pump with HTHP (PV/T-DXHP + HTHP), and iv) PV-powered air-source heat pump with HTHP (PV-ASHP + HTHP). A techno-economic assessment considering local weather, heat demand and system costs was conducted for four representative cities: Birmingham, Shanghai, Mumbai, and Los Angeles. Results show that heat pump-based systems have 50–67 % lower levelized cost of heat (LCOH) compared to PV/T-EB. Global climate and economic boundary conditions guide the selection of specific SAHP solutions. Water-based PV/T-HTHP and PV-ASHP + HTHP show the lowest LCOH ($0.028–0.042/kWh) for 80–100 °C applications in sunny regions (equatorial regions), while PV/T-DXHP + HTHP system offers the highest COP and lowest LCOH (0.046–0.056 $/kWh) for 100–160 °C heating in moderate solar zones. Although PV/T-EB shows the highest LCOH under current cost conditions, it may become favorable by 2035 (with a projected 30 % cost reduction) in areas with poor solar resources for high-temperature (>140 °C) applications, where it can also achieve lower life-cycle CO₂ emissions compared to solar-assisted heat pump (SAHP) systems. For higher temperature processes (>200 °C), additional technologies beyond the scope of this study will be required. In summary, this article highlights the overall advantages of SAHPs in global heating scenarios within the 80–160 °C range by comparing SAHPs, EBs, and gas boilers (GBs) in terms of performance, economics, and carbon emissions, thereby providing a theoretical reference for addressing the decarbonization of ∼30 % of industrial heating demand.