The transition to low-temperature supply in district heating networks as well as the transition towards renewable heat sources require new technical solutions that allow the introduction of new actors in the district heating sector. These new actors are defined as prosumers that are both connected to the district heating network as consumers and can deliver heat to the network. In Høje-Taastrup Municipality, different prosumers are already connected or in the process to be connected to the district heating and cooling network.

Prosumers

The aim of Høje-Taastrup Municipality and Høje Taastrup District Heating of moving towards a green heating sector is based on the introduction of renewable sources in the heat production to reduce its environmental impact. The implementation of decentralized renewable heat sources in the DH network plays a main role in this green transition. Among the available solutions, it is possible to take advantage of the waste heat produced by large cooling systems, such as in shopping malls or data centers.

This new type of actors in the DH network are classified as “prosumers”, as they are connected to the DH network as heat consumers, but at the same time they can deliver heat to the network itself as well as deliver cooling to the district cooling network.

In Høje-Taastrup Municipality, there is a detailed plan to take advantage of this type of actors and introduce them in the network, where demand of cooling and heating can be fulfilled by these prosumers.

CITY2 shopping mall – connection of prosumer heat pump and district cooling

A model example of a good prosumer solution is located at the shopping mall called CITY2 in Høje-Taastrup, where a new heat pump system was installed between the end of 2020 and the beginning of 2021.

Thanks to the COOL DH project, the heat produced by the cooling system of CITY2 is now used by the new heat pump to supply the LTDH network in Østerby district and to Høje Taastrup C, as presented in the figure below. The system is mostly supplied by electricity from the photovoltaic system installed on the roof of the shopping mall (16,300 m² of PV panels). The new DH network in Østerby district was designed to ensure a temperature of 55°C on the supply side and 30°C on the return side, with the furthest user that will be supplied with 53°C and a flow of 1000 l/h.

Figure of the prosumer systems at CITY2 and Østerby district

The heat pump uses the return flow from the cooling system as heat source to heat up the DH water up to max 70°C, which is then partly used in CITY2, Høje Taastrup C and delivered to Østerby district at lower temperature. On the cold side, the heat pump provides part of the cooling load of the shopping center. Furthermore, the extra cooling load is used to supply the district cooling network.

Østerby district (159 houses) can be supplied either by the heat pump or by the traditional DH network, which can work as back-up solution. The same principle is applied to the heating system in CiTY2, which can be supplied from both the heat pump and the traditional DH network.

This prosumer solution can have a large replication potential in many other places, where a heat pump can be used to take advantage of the low-grade heat and at the same time cover part if the cooling load. In order to do that, new technologies and control systems are beginning to be available on the market.

More information:

Contact Uffe Schliess, Høje Taastrup Fjernvarme AMBA.

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