Seasonal Thermal Energy Storage – A Major Breakthrough for Solar Heating


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Large-scale solar heating solutions for district heating, process heat and buildings with major energy requirements

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High performance solar thermal collectors and an enormous pit heat storage facility make the heat from the sun last all year round - e.g. in Vojens, Marstal, Gram and Dronninglund in Denmark. The pits cover up to 50% of the annual heating consumption

When the radiant light and heat from the sun peaks, the need for district heating is at its lowest – and when we really need the district heating, the solar energy is not easily harvested. This has always been the factor, limiting solar coverage to 20-25%, when considering solar heating for district heating, but now a solution has been found in cold Denmark. The world’s largest solar heating plants for district heating now cover up to 50% of their heat consumption – thanks to the combination of high performance solar thermal collectors and an enormous pit heat storage.

The World’s largest solar thermal plant for district heating

Ambitions have been high and in order to find a solution that would cover up to half of the consumption required by the heating station, it was necessary to think big. In Dronninglund, 35,000 m2 solar collectors have been installed on the area provided for the purpose. However, it turned out that Arcon-Sunmark solar collectors could be situated so closely together that there was room for additional 2,275 m2. This made the installation not only the largest in Denmark, but the world’s largest solar thermal installation for district heating at the time of installation.

Seasonal storage makes the heat last. The challenge is how to store the heat for colder times. Heating stations quite often have a storage tank containing approx. 1,000 m2, but the pit heat storage in Dronninglund contains a total of 60,000 m3 and in Vojens even 200.000 m3. With the pit heat storage the challenge is turned into an advantage: The summer surplus heat is utilized for 90 degree hot water in the huge seasonal storage. And with the huge quantities of hot water in stock, the district heating consumers may gain from the solar heat well into the winter.

If you want to learn more about Pit Heat Storage please contact Arcon-Sunmark.

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