The economic potential for increasing efficiency has already largely been exhausted in many conventional industrial processes. Furthermore, all of the technical potential needs to be tapped in the future. Above all, it is important to reduce primary heat demand by optimising or converting processes and preventing heat loss, e.g. through optimal insulation, because: heat that does not need to be produced in the first place has the best carbon footprint. Beyond that, “unavoidable” waste heat can be utilised in a variety of ways. For example, factories and businesses can use it directly for preheating processes, to heat premises and to heat water. Alternatively, it can also be fed into a local or district heating network and thus made available to external parties, for example a local business, or to heat buildings in urban districts.
Converting to electricity is also possible. If the temperature of the waste heat is too low to utilise, it can be increased using heat pumps, for example. Waste heat utilisation offers great potential for climate protection since nearly half of the energy used to generate heat is still currently being lost as dissipated heat. A recent analysis of potential by the North Rhine-Westphalia Agency for Nature, Environment and Consumer Protection assumes 88 to 96 terawatt-hours of technically available waste heat per year in NRW, of which around half (44 to 48 terawatt-hours) is reckoned to be technically usable – this would equate to a CO2 reduction of up to 13 million tonnes per year. When developing the much-discussed prospective hydrogen infrastructure, further waste heat sources can be expected, particularly from electrolysers.