Steinbeis experts provide scientific support for new multifunctional heat storage
At the end of September, the water was turned on at the nearly completed multifunctional heat storage built by the municipal utility company of Hennigsdorf in northern Brandenburg. Over the course of the next five weeks, the huge 24-meter-high steel tower was filled with five million liters of water. With the heat storage up and running, 80% of the heat supplied to the Hennigsdorf municipal utility company’s heating network will be carbon-neutral. The project is a blueprint for many other similarly sized towns. Since 2016, the team at the (Solites) has been providing scientific support for the municipal utility company’s efforts to establish a sustainable heat supply for its district heating.
The multifunctional heat storage ensures that heat is always available to the Hennigsdorf network whenever it is needed. Heat is prevented from escaping by a 40-centimeter-thick insulation layer coupled with trapezoidal sheet insulation. Municipal utility company CEO Christoph Schneider explains why this five million euro investment is so important: “As heating providers, we are faced with the challenge of making our district heating system carbon-neutral by 2045.” Hennigsdorf’s “Wärmedrehscheibe” heating hub project aims to progressively decarbonize the town’s district heating system. 60% of the heat supplied is already carbon-neutral. “With our multifunctional heat storage, we hope to increase the proportion of renewable heat in the network to 80%.”
Hennigsdorf leads the way
Magdalena Berberich is a Steinbeis Entrepreneur at the Steinbeis Research Center Solites in Stuttgart, which is providing the municipal utility company with scientific support for the project’s implementation. According to her, Hennigsdorf is very much at the forefront of sustainable heating projects in Germany. “By the end of the year, this will be the first town in Germany with an 80% renewable heating supply. This puts Hennigsdorf well ahead of its peers and makes the ‘heating hub’ approach a blueprint for many other similarly sized towns.”
Policymakers were fulsome in their praise at the multifunctional thermal storage facility’s official opening. Michael Kellner, Parliamentary State Secretary to the Federal Minister for Economic Affairs and Climate Action, congratulated the town council and municipal utility company for having started to think about a future renewable heating supply from an early stage. “Here in eastern Germany, we have a fantastic resource available to us, in our existing district heating networks”, said Kellner.
He added that this resource is especially large in Hennigsdorf, where 80% of buildings are heated via the district heating network. “If we also manage to convert existing heating networks in other locations to renewable energy, the opportunity is there for us to achieve a very rapid climate impact.”
The heat storage allows the municipal utility company to store surplus renewable heat so that it can subsequently be used when needed, in other words at times when demand is particularly high. This helps to reduce the use of fossil fuels.
Technical director and authorized representative of the municipal utility company, Stefan Dallorso, explains how it works in practice: “Once the storage tower has been filled with water, we can start using it to store waste heat from the adjacent steel and rolling mill’s rolling process. A heat exchanger transfers the energy from the hot flue gas to the water, heating it up.” Thanks to water’s good thermal properties and the storage tower’s external insulation, very little heat is lost during storage. “By decoupling the time when the heat is produced from the time when it’s utilized, we can use the stored heat whenever it’s needed.”
Multifunctional thermal storage facilities can store heat from different sources and distribute it to consumers as required. “For instance, we can also store heat from our biomass cogeneration plant here”, says Dallorso. Especially during the warmer times of year, when the heat produced by the biomass cogeneration plant from renewable woodchips heat provides a way of reducing the amount of heat derived from fossil fuels.
A water circuit with added value
Magdalena Berberich highlights the innovative use of a water circuit with integrated storage. “To ensure efficient operation, the water temperature is different at different levels of the storage tower. The hottest water is at the top, where its temperature can reach a maximum of 98 °C. This is the temperature required for the district heating network. The temperature of the water right at the bottom is 55 °C – this is the return temperature.” Hydraulically speaking, the multifunctional heat storage forms part of two circuits. “The district heating water heated to a maximum of 98 °C by the waste heat from the steel mill goes into the upper part of the storage tower. Meanwhile, 55 °C water flows out from the bottom of the tower to the steel mill, where it is reheated and subsequently fed back into the storage facility.” The “Nord II” boilerhouse is located on the other side of the site. “When the heating network calls for heat, hot water is drawn from the top of the storage tower and fed into the network. At the same time, the bottom pipe feeds the 55 °C return water back into the tower”, explains Berberich. The multifunctional thermal storage facility can supply an additional 13,400 MWh/a of renewable heat to the district heating network. And it’s not just the climate and environment that benefit from the facility – the municipal utility company’s district heating customers also stand to gain. “Renewable energy helps us to keep prices stable, even during uncertain times”, says CEO Christoph Schneider, who promises to continue using the available resources to deliver affordable heating in the future, too.
Contact
Dr. Kathleen Köhler (author)
Freelance author/editor
Magdalena Berberich
Steinbeis Entrepreneur
Steinbeis Research Center for Solar and Sustainable Thermal Energy Systems (Solites) (Stuttgart)
www.solites.de