VEKS (transmission company for the Western suburbs of Copenhagen), is facilitating the optimization of electricity production in the Copenhagen area and is used in the local distribution DH network for peak shaving, yielding significant environmental and economic benefits. The PTES in Høje Taastrup received the Global District Energy Climate Awards in the Sector Coupling category during the Euroheat & Power Summit on 14-15 November 2023 in Brussels, Belgium. Figure 4: The concept of seasonal storage can be illus- trated with the mismatch between solar thermal energy production, which peaks during the summer, when the heat demand is lowest: an LTES can then be used to store large amounts of heat during the mismatch period to be reused later during the year (hence the term “seasonal” storage).
Figure 3: The main types of LTES technologies can store heat or cold in water or the subsurface
heat should be suitable for discharge into District Heating networks, maintaining temperatures between 50°C and 100°C. These technologies offer versatility, serving as daily, seasonal, or multifunctional thermal energy storage adapted to various heat sources and load profiles..
Pit Thermal Energy Storage (PTES): Denmark’s Innovative Solution
Denmark has emerged as a pioneer in Pit Thermal Energy Storage (PTES), particularly in combination with Solar District Heating (SDH) for seasonal storage. PTES, now utilized for short-term thermal storage in district heating networks, holds immense promise for decarbonizing the heating sector. The PTES project in Høje Taastrup, Denmark, illustrates this new use of the PTES technology, showcasing substantial fuel savings and CO2 emissions reductions. This 70,000 m3 PTES, owned by Høje Taastrup District Heating and
The list of PTES implemented by Danish Companies and consultancies can be seen in Table 1:
Looking Ahead: Accelerating the uptake of LTES. According to a recent study by Aalborg University, the extension of DH to reduce fossil fuel imports and consumption has tremendous potential, for instance, to use the large amounts of available waste and geothermal heat. “District Heating is the
Country
Project
Size
Heat capacity
Year commissioned
DK
DTU
500 m³
1983
DK
Ottrupgaard
1'500 m³
43.5 MWh
1995
DK
Marstal Sunstore 2
10'000 m³
638 MWh
2003
DK
Marstal Sunstore 4
75'000 m³
6'960 MWh
2012
DK
Dronninglund
60'000 m³
5'500 MWh
2013
DK
Gram
122'000 m³
11'300 MWh
2014
DK
Vojens
203'000 m³
18'800 MWh
2015
DK
Toftlund
85'000 m³
6'500 MWh
2017
CN
Tibet
15'000 m³
1'000 MWh
2018
DK
Høje-Taastrup
70'000 m³
3'300 MWh
2023
Table 1: Historical table of PTES development in Denmark or initiated by Danish companies and consultancies. The last line is the only storage that is not used as seasonal storage for solar thermal heat.
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