Milestones: Power-to-heat

Power-to-heat (PtH) - this is the keyword for the use of wind power that would otherwise have to be curtailed. It sometimes happens that more green electricity is produced than can be put to use on site or transported further. With power-to-heat plants, the electricity can be converted into heat and then used for district heating or hot water supply. 50Hertz is active in the field of PtH together with various local partners: several projects are already in operation, and further plants are under construction or in the planning stage. For example, the starting signal was given in Halle (Saale) at the beginning of 2023: Together with the Stadtwerke Halle subsidiary EVH GmbH, 50Hertz is building a power-to-heat plant with a capacity of 40 megawatts (MW).

Two birds with one stone

With an output of 80 megawatts, it is calculated that 27,000 Hamburg households can be supplied with green district heating in the future. Up to 100,000 tons of CO2 can be saved per year by using the plant. Stefan Kapferer, CEO of 50Hertz: "The heating sector faces enormous challenges in decarbonization. At the same time, it happens more and more oft that more renewable electricity is generated than consumed. With the PtH plant in Wedel, we are therefore killing two birds with one stone: on the one hand, it contributes to the decarbonization of the heat supply and, on the other hand, it strengthens the system security of the power supply overall. At 50Hertz, we are convinced of the concept of 'using instead of curtailing'."

Mr. Hodurek, the contract with Stadtwerke Halle has been signed, the seventh PtH project has thus been sealed, and others are on the horizon. What role does power-to-heat play on 50Hertz's path towards 100 percent renewables?  

With growing shares of renewable electricity from wind and solar, the need for balancing solutions increases in order to use the energy sensibly in times of overproduction. In order to secure supply at all times and at the same time use as much as possible of every kilowatt hour of electricity generated and that can be produced, converting electricity into thermal energy is a very sensible approach. Under the impression of high amounts of deregulation, the legislator created the prerequisite with the 2017 amendment to the law to implement measures to herald the heat transition, because heat generation from renewable electricity will play an important role in the replacement of fossil fuels in the future. 50Hertz decided early on to tap the potential of power-to-heat and to become active here together with partners. As a result, we were able to put three PtH plants into operation as early as 2021.

Power-to-heat comes in different forms. In addition to heat pumps, the classic heat generation via electrode boilers used in our projects, which has been tried and tested and for which experience has been available for decades, plays an important role. This means that we are also indirectly providing start-up assistance for the building sector - i.e. property heating. This is cross-sector climate neutrality at the initiative of the electricity sector.

What lessons have been learned from the first projects that have already been implemented in the follow-up projects?

We already learned a lot. It starts with the actual project, when instead of an electricity generation plant there is now an electricity consumer in the distribution network. Up to now, the power generation plants have supplied electricity to many consumers in addition to the heat customers. If these are switched off, more electricity has to be drawn from higher network levels. The power plant itself has also contributed to voltage maintenance and frequency stability, but the power-to-heat plant cannot do that out of the blue. In this case, it must be checked in advance together with the distribution system operator whether it also meets safety requirements, and if necessary, the project must be adapted.

This continues with the integration of the plants into the control processes. Processes and standards that are taken for granted in the transmission grid and by large power plant operators must first be implemented here in close cooperation with our partners. This takes time and means effort on both sides.

Finally, we learned a lot about how interlinked the sectors already are when it comes to legal issues. After all, there is a lot to consider when using surplus electricity to supply heat due to extensive European and national regulations.