Modern heating for the Erich Kästner school in Merbeck

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Modern heating for the Erich Kästner school

After more than 40 years of use, the old system has reached the end of its useful life. Which two criteria are decisive in choosing the new system.

After 43 years, the oil-fired heating system of the Erich Kästner primary school in the Merbeck branch has had its day. As a rule, according to the city administration, such a system is based on an operational life of 25 to 30 years. Last September the building committee approved the installation of a new heating system after anomalies were found in the burner and the control unit during maintenance work.

Now city councilors have been faced with the question of which technology to install. Efficiency and climate protection were the decisive criteria. Fossil fuels and renewable energy sources were equally under discussion. Ultimately, it wasn’t a decision of either of us, but a decision of both.

The municipal building management department has considered three variants: a conventional gas heating system, a pure air-to-water heat pump and a bivalent system which covers the basic heat requirement via a heat pump and can provide higher thermal loads on cold days through an additional boiler gas. The administration classifies the latter variant as particularly efficient, but it is also more expensive because two heating systems have to be installed. With the exception of Bündnis 90 / Die Grünen, all parliamentary groups shared this point of view. The Left Party abstained from voting.

The new heating system must be used exclusively for space heating. Hot water for school and the open all day is generated completely decentralized via electrical devices at the taps. According to information from the Department of Education and Social Affairs, the showers of the local Merbeck sports club, which are currently still supplied with hot water, will be taken out of service later in the year, as the sports club will then put the showers in the its club house. The previous diesel heating system including tank is to be dismantled and the rooms in the basement must be used as storage rooms for the school.

Contrary to the majority of the Environment Committee, the Greens favored a pure air-to-water heat pump because of the good environmental balance. In justifying him, Marc Ostendorp also questioned the accuracy of the operational cost calculations that the administration had made to compare the three variants. He assumed a gas price of 10.1 cents and an electricity price of 28.2 cents per kilowatt hour. “At the moment, when energy prices are changing by leaps and bounds, such a profitability calculation is like looking into a crystal ball,” he said when asked by our editorial team. “If I don’t know the energy prices of the future, I can’t say exactly which variant is the cheapest,” says Ostendorp. “That is why the decision criterion of climate protection was decisive for us”.

In anticipation, the Greens had suggested examining the possibility of a geothermal heat pump. However, from the point of view of the municipal administration, the costs would be too high due to the necessary drilling depth. For the preferred variant with condensing boiler and air-water heat pump, total construction costs of 140,000 euros are estimated. The city wants to apply for a loan from the Federal Office for Economic Affairs and Export Control, which should be around 45,000 euros if approved. A budget of 205,000 euros is foreseen in the draft budget for 2022. A photovoltaic system could also be installed on the roof of the elementary school – as a supporting component for the heating. The city assumes the measure will have paid off after 26 years.

A pure air-to-water heat pump would have the best CO2 balance, as calculated by the administration. However, the system would have to be sized larger, which would lead to a “very unfavorable cost-benefit ratio”. The total estimated construction costs are almost 20,000 euros higher than those of the bivalent variant, the total costs expected after 15 years of activity exceed 35,000 euros.

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