04.07.2022, Berlin: Eine moderne Hochtemperatur-Wärmepumpe steht bei dem ·Richtfest· in der Vattenfall-Kältezentrale. Die Pumpe verwertet die in der dortigen Kältezentrale entstehende, überschüssige Abwärme, hebt diese auf ein höheres Temperaturniveau und speist sie ins Berliner Stadtwärmenetz ein. Foto: Monika Skolimowska/dpa +++ dpa-Bildfunk +++

The heart of the new system is the compressor – with its massive cover it is reminiscent of a diving robot. Here, the gaseous refrigerant is compressed so that it heats up considerably and then transfers its heat to a water cycle. The result is water with a temperature of up to 120 degrees to supply 3,000 Berlin households with heating in winter. In summer it is even enough for the hot water needs of 30,000 households.

We are talking about a new high-temperature heat pump that is being built in Vattenfall’s cooling center on Stresemannstraße – the topping-out ceremony was celebrated on Monday. In the future, the heat pump will upcycle the waste heat from the refrigeration compressors, which previously simply escaped into the environment, i.e. heat it up further and feed it into the district heating network.

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In this way, 55 gigawatt hours of heat can be generated per year while saving 3.2 million cubic meters of natural gas and 120,000 cubic meters of cooling water. A project made for the energy transition – if it actually works. Commercially available heat pumps just barely manage to heat a single-family house.

The plant is scheduled to go into operation next winter. Planning and construction of the pilot plant cost 7.8 million euros; The Federal Ministry of Economics and Climate Protection will pay 40 percent of this sum. Siemens Energy is essentially responsible for the technical processes.

The larger components of the XXL heat pump are already in a cleared area of ​​the cooling center. They are to be connected to one another and the control technology installed over the summer. A three-year monitoring phase to test the system begins in November.

“Heat will be the next big thing,” said Tanja Wielgoß, board member of Vattenfall Wärme Berlin AG. So far, the cooling center at Potsdamer Platz has focused on the opposite. Customers such as the Philharmonie or the neighboring Federal Ministry for the Environment receive six degrees cold water to cool the rooms in summer. An important service that customers appreciate, says Wielgoß. She had heard from the Philharmoniker that they no longer had to tune their instruments as often.

According to Vattenfall, a total of 12,000 offices, 1,000 apartments and various cultural institutions are supplied with cold. The cooling center is celebrating its 25th anniversary this year. The waste heat from the cooling systems dissipates for just as long – also, as a Vattenfall technician revealed, because it wasn’t worth looking for alternatives for a long time given the low energy costs. “Necessity drives innovation.” However, it was not only the Ukraine war that triggered the corresponding emergency.

Since 2016, Vattenfall engineers have been looking for solutions to use waste heat sensibly. While it is relatively easy to generate climate-neutral electricity today, the implementation of the energy transition in heat production is much more difficult, explained Christian Bruch, CEO of Siemens Energy AG, at the presentation of the system.

“Half of the primary energy consumption is heat. Closing chains, energy efficiency, is extremely important,” said Bruch. The fact that water with a flexible temperature level is used for district heating in Berlin – 80 degrees hot in summer, up to 120 degrees in winter – is “unusual” and therefore a special challenge when configuring a heat pump.

Their secret is a “new type of coolant” that still has to prove itself in practice. After all, it must not decompose despite the high pressure and temperature fluctuations in the closed circuit.

“Projects like this still have a risk,” explained Wolfgang Langen, Ministerialrat in the Federal Ministry of Economics. “A lot can still happen when it comes to upscaling.” Nevertheless, the project won funding in competition with many others.

If there is a foreseeable shortage of natural gas, the pump will probably not achieve decisive savings. Vattenfall generates electricity and heat in gas-fired power plants and sells natural gas to its customers. If necessary, some gas-fired power plants could switch to other energy sources, said Wielgoß on the sidelines of the event.

Because the combined heat and power plants are very efficient, she believes “that we can continue for a very long time”. There is “a plan in the drawer” for all scenarios. The industrial customers, who receive 30 percent of the power plant output, would have to “switch off themselves” anyway in the event of a gas emergency.