DESY's particle accelerators are very energy-hungry. Not only acceleration, but above all deflection by large magnets consumes large amounts of electricity. And although the superconducting accelerators FLASH and European XFEL are highly efficient thanks to their technology, they have to be cooled down to two degrees above absolute zero – the helium liquefaction necessary for this also swallows up energy. All in all, DESY needs about as much electricity as a small district in Hamburg.

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The waste heat recycling system at DESY: the accelerators and their support systems on campus can be used to warm the entire campus. So far a third of the campus is heated in this way.

“A large part of our consumed electricity is ultimately converted into heat. But we need the energy to be able to do our research. Soon we will completely recycle this surplus residual heat for heating buildings,” Denise Völker, sustainability manager at DESY, explains the concept. For this purpose, cooling systems from accelerators and computer centres are to be connected to a kind of local heating network and supply the DESY heating systems. This is already happening with the waste heat from helium liquefaction, which is used to heat about a third of the Hamburg campus. The problem: While the cooling water from helium liquefaction is very warm at around 75 degrees and has been able to be fed into the heating system without any problems for quite some time, the temperature of the cooling water that comes directly from the accelerators is much lower – it is around 35 degrees.

“This allows the underfloor heating to operate well in well-insulated buildings,” says Völker, “but in our old existing buildings with radiators we need higher flow temperatures.” Therefore, for example, the cooling circuit of the PETRA III accelerator, which was previously cooled in hybrid dry coolers on the air, is to be connected to a huge heat pump that raises the heat from the cooling water to higher temperatures. “This is done with electricity again, fortunately green electricity in our case, but afterwards we can then also use the accelerator waste heat across the board,” explains Völker. And with great potential: DESY will be able to heat itself almost completely and would only have to resort to district heating in exceptional cases. The calculated savings are more than 500,000 euros per year. The investment of a good two million euros for the heat pump, building and all connections would therefore have paid for itself after about four years.

A longer-term part of the project is the direct use of low-temperature waste heat, which is possible in new buildings. For this purpose, a low-temperature heating network is being set up on the DESY campus in Bahrenfeld, which can supply the new buildings and the DESYUM visitor centre in particular. Surface heating systems are planned in these buildings, which will make it possible to use the waste heat without having to raise the temperature. “In the south of the campus, we are also planning a connection to a local heating network, which we could later use to supply Science City Hamburg Bahrenfeld, which is currently being planned,” says Denise Völker. “So in the long term, not only research will benefit greatly from the operation of our accelerators, but also our neighbourhood.”

At the DESY site in Zeuthen, the use of waste heat for heating and hot water supply is also planned - here, however, it will not come from accelerators, but from the computer centre. A good 800,000 euros will be invested in this project, which will be completed this year. The estimated annual savings are over 300,000 euros. This is not a drop in the ocean, says Denise Völker: “It would be ideal if we could set up sustainability projects in such a way that we put the money saved into new energy efficiency and renovation projects. Then the improvement of our environmental balance would pay for itself in the long run.”

More information:

Energy management at DESY (only in German): https://nachhaltigkeit.desy.de/energiemanagement/index_ger.html

First DESY sustainability report: https://nachhaltigkeit.desy.de/sustainability_report/index_eng.html