Fig. 1: Statistical data on global energy consumption and waste heat, and illustrative example of a high-temperature heat-pump energy chain.
From: Emerging opportunities for high-temperature solid-state and gas-cycle heat pumps
a, Industrial heating share in terms of global energy consumption. The overall share is broken down by temperature ranges corresponding to different industrial processes. The energy source share used for industrial heating is shown, and it comprises renewable energy sources (RES), natural gas, oil and coal. Data are compiled from ref. 1. b, Global waste heat share with respect to global energy consumption and the proportion across different temperature ranges. Data are compiled from refs. 2,3. c, Performance figures of merit for different operating parameters of the evaluated technologies: heating coefficient of performance (ratio of the heating power to the power input to the device) COP as a function of the heat sink temperature and temperature difference between the heat source and heat sink for different second-law efficiencies (note: COPheating Carnot = TH/(TH − TC), COPheating = η2ndCOPheating Carnot). d, Our view of the future second-law efficiency and heating power for the evaluated technologies for thermoacoustic and for mechanical Stirling13,15,18,64,73,78,79,82, Brayton gas cycle16,43,47,48,92, caloric24,28,29,97, thermoelectric20,36,58,59,60,61 and vapour compression9,98,99 devices.
