Modular energy center for green heat supply

14.04.2025

Source: E & M powernews

Stadtwerke Ulm/Neu-Ulm has built an energy center with a renewable heat share of 70 percent for a new development in Wullenstetten - with pellets and a CHP unit.

The new energy center for the new "Wohnen am Stadtpark" development in the Wullenstetten district of Senden (Bavaria) operates with a renewable share of more than 70 percent. This means that "the plant only needs gas at peak load times," said Mayor Claudia Schäfer-Rudolf on April 11. Stadtwerke Ulm/Neu-Ulm (SWU) and the city officially unveiled the new energy center. Interested citizens were also able to visit the plant. The next step will be the expansion of district heating in the town center of Senden, said the mayor.

"The energy center at Stadtpark makes an important contribution to reducing CO2 emissions and underlines the importance of modern, resource-saving technologies for a sustainable future," said Bernd Adolph, Managing Director of SWU Energie. "The residential area and the school center will also be connected to the Neu-Ulm/Senden district heating network in a few years."

At the moment, the local heating network is an isolated network. According to SWU, this was taken into account during the planning phase and is one reason why the control center was built in modules. This means that the individual elements of the generation systems and the system peripherals can be adapted, dismantled or moved to another location as required to conserve resources.

Modular container design

The modular design of the generation plant was also a key element that ensured that the extremely ambitious schedule, which aimed to commission the generation plant in October 2024, could be met. The total construction time was only around eight months.

At the heart of the plant are two wood pellet boilers, each with a thermal output of 350 kW. The pellet stores with a total volume of 40 tons are located above the boilers. The system is supplemented by a combined heat and power plant with a thermal output of 107 kW and an electrical output of 70 kW, a peak load boiler with 1,950 kW and buffer storage tanks with a capacity of 50 cubic meters.

A natural gas boiler was also installed to ensure a reliable heat supply even at peak load times or when individual generators fail. This innovative combination of different technologies is the result of the demanding requirements of the heat transition and represents a forward-looking solution. It also offers greater flexibility in generation than conventional, purely conventional generation plants due to the various energy sources available. Over 70 percent comes from renewable energies, i.e. from the pellet boilers. Around 20 percent comes from CHP and only a maximum of 10 percent comes from natural gas boilers.

When completed, the energy center will supply up to "350 residential units and the school center," explained SWU project manager Lisa Kienzle. With the peak load boiler, 100 percent supply security is also guaranteed despite the current island grid situation. The network is currently 4.3 kilometers long. Connection to the interconnected grid is also planned for 2026/2027.

SWU opted for a CHP solution for this new-build district because it is the most economical option. Kienzle: "Heat pumps were out of the question here because they would have required their own transformer station. This would have resulted in additional costs and construction time.

In total, SWU invested around 4 million euros in the energy center and the grid expansion. The utility received both a subsidy via the federal subsidy for efficient heating networks (BEW) and a subsidy for the CHP plant. The two pellet boilers were subsidized via BEW module 3. The CHP plant received operating cost funding and the buffer storage tanks received investment cost funding - both via the KWKG.

In this context, Adolph Bernd emphasized that a continuation of the funding programs is urgently needed for a further successful heat transition. "An expansion of district heating with a high proportion of renewable energies only works with subsidies."

Author: Heidi Roider