Large-scale heat pumps: Applications, performance, economic feasibility and industrial integration

Abstract Heat pumps can recover and upgrade industrial waste heat using renewable electricity, creating an essential technological lever to decarbonise thermal processes. High profitability requirements, unfavourable electricity-gas price ratios, and a lack of awareness of meaningful application possibilities among stakeholders from consultants and decision-makers, in both politics and companies, hinder further market penetration. To address these barriers, this review classifies 155 case studies of large-scale heat pumps to identify suitable characteristics that favour implementation. Unit operations, like utility water heating for cleaning purposes, process bath heating, drying, and thermal preservation processes, are identified as suitable processes that can be supplied with market-available heat pump technologies. These operations fall inside the current technology limits: > 50 kW heating capacity, up to 160 °C output temperature, and temperature lifts up to 95 K. COP regression models describe the efficiency of industrial water/water heat pumps, and recently also of HPs for drying and steam-generation purposes within a coefficient of determination of 0.87–0.96. These models form the basis for enhanced integration and economic assessment. Generalised results can be captured in the form of an universal nomogram to graphically evaluate ecological and economic break-even temperature lifts for heat pump integration concepts (i.e. between 26.5 K and 43 K temperature lift for an average price ratio of electricity to natural gas of 3.5 in Europe).