In Høje Taastrup, a suburb of Copenhagen, the local district heating company Høje- Taastrup District Heating Company (HTF) successfully supplies district cooling (DC) to companies and office buildings. The first DC plant has been in operation since 2016, and an energy center from 2017 has room for increased capacity.
By Uffe Schleiss, technical manager, Høje-Taastrup District Heating (HTF)
In 2014, HTF prepared a business plan for district cooling in the municipality’s central business area. Technically, it is a large heat pump plant with groundwater cooling (ATES – Aquifer Thermal Energy Storage) and a cooling accumulation tank.
However, the plan had to be quickly adjusted when Copenhagen’s Green Market (greenery and flowers) moved from Copenhagen to Høje Taastrup. Copenhagen Markets wanted district heating (DH) and a DC solution for 70 individual customers (shops) in the 67,000 square meters new building.
It became the first DC order in 2016 – with a DC network inside the building.
HTF invests in district cooling because:
- DC upgrades the district energy supply
- Synergy in providing cooling and heating to customers
- Energy and environmental benefits in the co-production of DH/DC
As it was a long way before the planned energy center, and as there was a need for low temperatures, HTF established a building with a heat pump (3.2 MW heat and 2 MW cooling) next to the Copenhagen Markets building. It can deliver a room temperature between 2 and 14o°C for the 70 individual zones/stalls.
A business opportunity
As an energy company focused on district heating, it was interesting, as a business opportunity, to combine DH and DC and thus utilize the heat created when water is cooled down. The solution for Copenhagen Markets would provide valuable experience for the upcoming DH/DC energy center supplying large production companies and office buildings in the business area around Høje Taastrup.
HTF provides cooling by a
MOBILE COOLING CENTER ON-SITE
It is vital to be ready at short notice when a customer needs cooling and is willing to invest in an individual refrigeration system. When established, the customer is hardly interested in district cooling until worn out and needs replacement.
A new energy center
Therefore, with a good insight into needs, design, and logistics, and help from Rambøll, HTF realized the project: A new energy center on Energivej in Høje Taastrup was in operation in March 2018. The basis for the new energy center was an agreement with three new district cooling customers: comfort cooling for an engineering company, an insurance company, and comfort cooling and cold storage for a hotel. Since then, another office building and a large shopping center connected to the energy center on Energivej, with a heat pump for 1 MW of cooling and 1.4 MW of heat. With the two new customers, the capacity is now almost fully utilized. But the center is designed for more heat pumps as the need arises. And the plan is, in the future, to connect the energy center and Copenhagen Markets.
One of the advantages of co-producing cooling and heating is to utilize the heat arising when cooling is produced – and vice versa. But, the need for cooling lies mainly in the hot season, where, conversely, there is not much need for heat. It was quite a challenge the first year when heat pumps failed due to the varying cooling needs, followed by lower supply security.
Optimized by ATES
The problem was resolved in 2019 when the ATES plant was established as part of the energy center on Energivej. With the ATES system, we can now produce winter heat without a simultaneous need for cooling. The heat pump cools the groundwater in the winter, so it has an extra-large capacity to supply most of the cooling in the summer. In this way, we optimize the process and make HTF independent of whether there is a simultaneous need for heating and cooling. Since the establishment of the ATES plant, the operation has been very stable. However, we have not clarified whether the geology meets our expectations regarding storing energy. We have yet to see if the water flow in the subsoil will affect the temperature when cooled down/heated up.
The main reasons for DC in HTF:
- The area around Høje Taastrup Central Station has great DC potential for existing and new companies and large office buildings.
- The synergy in co-producing DH and DC is evident economically and environmentally.
- The loss of energy co-producing DH and DC is significantly lower than produced separately with heat pumps and compressors.
- A promising future for DH/DC co-produced is limited only by a lack of public knowledge or prior cooling investments not yet refurbished.
- A lot of customer incentives like economy and reliability, no maintenance and no repair, user-friendly, free space, no harmful refrigerants in the building – and above all, lower CO2 emission, supporting the company’s green profile.