530kW air source heating capacity for Basel

In 2018, Basel City energy provider IWB installed two custom-made, high-temperature air/water source heat pumps from CTA, with a total heating capacity of 530 kW, in the St Jakob heating network. These replaced a natural gas-powered combined heat and power unit (CHP) and contributed to the further reduction of CO2 emissions from the heat supply in Basel.

The St Jakob heating network supplies, amongst other locations, the St Jakob football stadium in Basel, the St Jakob public pool and the St Jakobshalle.

Via the St Jakob network, IWB provides the St Jakob football stadium in Basel, the St Jakob public pool and the St Jakobshalle with heating. Where international tennis stars thrill the audience at the Swiss Indoors every autumn, IWB produces heat one floor below, stores it in a 42 m3 storage unit and delivers it to various consumers in the neighbourhood via a heating network.

Optimal accessibility for heating and servicing

Hot water from the air

IWB used the full renovation of the St Jakobshalle to further improve the carbon footprint of the heating network. At the beginning of 2018, the existing CHP in the heating centre of the St Jakobshalle was replaced with two air/water source heat pumps from CTA. The two identical units each deliver a heat capacity of up to 265 kW. Each heat pump is equipped with four compressors that enable demand-driven operation.

Two 11-metre-long air coolers stand on the roof of the hall. These extract energy from the air, with which the heat pumps can produce a hot water supply of temperatures up to 70°C, depending on the operating point. This energy is then transferred to the heat accumulator, from which the various consumers can then draw their heat. The accumulator is also the source of the heat for the hot water that the stars of FC Basel 1893 and international tennis players use to shower.

During summer, the heat pumps completely cover the hot water consumption of the consumers connected to it. At an ambient air temperature as low as 5°C—the average temperature in Basel is 10°C—the units produce 70°C hot water.

The heat pumps continue to produce usable heat even at an ambient air temperature of less than 5°C (and as low as -5°C)—even though, at 55°C, it can only be used for mild hot water return heating. During winter, two gas boilers, which are available for operation during the winter months and for peak loads in the heating centre, take over the residual heating to up to 80°C.


In brief

  • 530 kW (2 × 265 kW)

  • Up to 70°C hot water supply

Smart alternative for renewable energy sources

The air/water source heat pumps in the St Jakobshalle impressively demonstrate the potential of green heat generation “from the air”, if neither groundwater nor a geothermal probe field are an option as a renewable energy source. CTA’s experience shows that air as a source of heat is becoming more and more popular, particularly in the 200 to 2,000 kW output range. This applies to both heat pump solutions that cover overall heating requirements (monovalent generation) and to systems using additional heat generation for peak demand (bivalent generation). Also gaining ground are systems using natural refrigerants, such as propane or ammonia (NH3), which are designed to meet individual requirements.


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