15 Sep 2021
by IEA DHC

Excess heat recovery from data centre in Braunschweig, Germany

Veolia’s subsidiary BS|ENERGY is a local energy (electricity, heat, and gas) provider in Braunschweig, Germany. It operates an existing district heating network that spans the whole city. It is powered by high-efficiency coal and gas cogeneration plants.

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A local property developer requested district heating during the early planning phase of a new residential area. With the simultaneous construction of a new data centre in the adjacent parcel, Veolia identified this as an opportunity to develop an innovative network that would utilise the waste heat from the cooling system of the data centre. Extracting heat from the data centre reduces the need to cool the data centre and associated energy consumption accordingly.

To supply a newly built energy efficient housing area consisting of 600  housing units with a net floor of 48,000 m2 , the low temperature network will be used. The peak heat demand is estimated around 1.8 MW, and the base load will be covered by the waste heat recovery. The low temperature of the heat source, 25°C, requires a heat pump to increase the source temperature to a satisfactory level for the network. At the same time, keeping the temperature level of the DHN supply as low as possible is desired for high efficiency. A connection to the existing high temperature DHN of BS|ENERGY will also be provided, enabling flexibility and demand peak shaving.

Data centre operator transfers its waste heat to a cooling water cycle. The cooling water with a temperature of 25°C is forwarded outside of the data centre to the energy station.

The heat pump cools the cooling water to 18°C and uses the removed heat to raise the return temperature in the network to the required supply temperature of 70°C. The cooling water is now able to take up the excess heat again. Connection to the existing high temperature network enables demand peak shaving. The project received the 6th Global District Energy Climate Award in 2019 for the vision of a new, highly energy-efficient district energy system (Euro-heat, 2019).

Concerning pricing scheme, BS|ENERGY does not apply any diversification in terms of tariff on their customer base. No differentiation was applied to customers supplied from the traditional high-temperature district heating network. Pricing scheme is available at the BS|ENERGY homepage. In addition, a fibre optic internet access infrastructure is part of the package for all clients