Fossil-fuel driven
100% CO emissions
Flue gases 10%
Waste heat 100%
Process heat 100%
Heat-pump driven
Process heat 100%
Waste heat 25%
0% - 33% CO emissions
Fossil fuel 110%
Vs
Steam boiler Process heat Fossil fuel
Process
(
(
=
= 90%
Example using a heat pump
COP (
(
Process heat Electric power
=
> 4.0
Valid for hydrogen as well if used as fuel gas
Process
Electric power 25%
Waste-heat recovery 75%
COP = Coe cient of performance
Figure 5 Efficiency comparison of heat transformation industrial heat pump vs fossil fuels
plants, for example, represent a continuous flow of low-temperature heat that can be made usable again. Moreover, new megawatt-scale electrolysers are being installed almost weekly in many places around the globe, representing a huge, untapped potential of low-grade waste heat. Example: chemical industry An example from the chemical industry highlights the possibility of smoothly integrating a heat pump into existing systems: In the industrial production of bioethanol, the ethanol/ water mixture obtained through fermentation is separated by a multistage distillation at approximately 80 to 100°C. The distillation column is usually heated with low-pressure steam generated from natural gas in a power
plant or boiler. The purified ethanol steam is then condensed in a water-cooled condenser and the heat is released into the environment via cooling towers. The heat from condensing the ethanol can be transferred into the circuit of a heat pump, and the heat from the distillation can be fed back in as usable heat. A temperature rise from 70°C to 110°C can result in a COP of 4, while thermal outputs of up to approximately 50 MW can be achieved for each machine. Example: hydrogen electrolysis No system has perfect efficiency, and this holds especially true for large-scale electrolysis in the production of green hydrogen. A typical hydrogen plant using modern electrolyser technology reaches efficiencies between 60 and
25% Waste heat
+
–
100% Renewable electricity
Electrolyser
75% Energy stored in H
Figure 6 Even the most advanced commercially available hydrogen electrolysers can turn only 75% of the input electricity into chemical energy in the form of hydrogen
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