Decarbonisation Technology - November 2022

Heat pump Transition grid losses Hydrogen Electrolyser & Transport Electrical heater Transition grid losses

Driver Motor “COP”

1 kWh

0.95 kWh electricity

2-4 kWh usable heat

0.6 kWh

0.7 kWh H 2

1 kWh

Combustion in boiler

0.95 kWh electricity

0.95 kWh heat

1 kWh

Use in direct heater

Table 1 Efficiency comparison in terms of heat transformation (hydrogen vs heat pumps vs electrical heater)

wastewater from a sewage treatment plant which acts as the heat source, while the heat sink is the urban district heating system. The systems have thermal outputs of over 60 MW per unit. Furthermore, two Atlas Copco Gas and Process heat pumps installed in Stockholm’s heating network, each with 40 MW thermal output, save 90,000 metric tons of CO₂ emissions annually (compared to the previous use of heating oil). To achieve a comparable saving in road traffic, it would mean that the average Swedish gasoline- powered car would have to drive 500 million fewer kilometres every year. Conversion to energy circular economy From the many application segments in which heat pumps are used, five stand out: the production of paper, food, chemicals/ petrochemicals, the aforementioned district heating, and more general manufacturing where heat is required. The required heat for these is

typically between 80 and 250°C. At the same time, low-temperature waste heat is available in all production plants, which is rejected via cooling towers. From an energy point of view, this conventional use of heat is an open process that can be converted into an energy circular economy using a heat pump. But it is not just in the realm of industrial production where heat pumps are employed. In fact, there are more heat sources that are readily available, which may not be immediately recognisable as such: municipal sewage treatment plants, and hydrogen electrolysis

Figure 4 An integrally geared compressor deployed as an industrial heat pump in a district heating system, using cleaned sewage water as a heat source in Stockholm, Sweden

Figure 3 One of the world’s first large-scale heat pump installations, in Switzerland in 1938 (Photo credit: Baudirektion Kanton Zurich, Switzerland, 2007)