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

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In Dronninglund, Denmark, unused land has been utilized for cost savings and a greener world

In Dronninglund, Denmark, unused land has been utilized for cost savings and a greener world


When the 40-year-old oil boiler needed replacement, Dronninglund District Heating used the occasion to rethink the installations and to decide which installation would serve the district heating plant most effectively in the future. With assistance from the advisers they quickly concluded that a replacement of a part of the fossil fuels with solar thermal energy would make sense – economically as well as environmentally. Even the worst-case scenario would not make the prices rise over a period of 25 years. In itself, this equals security and cost savings, when compared to the expected increase in fossil fuel prices in the same time period.

Arcon-Sunmark was chosen as the supplier after an extensive EU procurement process and a detailed assessment of the competitors’ competences. And the management at Dronninglund District Heating Plant does not regret making that decision.


The total installation consists of a 37,573 m2 solar heating system and a seasonal pit heat storage – a hole in the ground filled with 62,000 m3 of water. During the summer, the plant actually produces 10 times the demand for heat per day. Hence the excess heat can be stored and used when the sun has less power. That makes it possible for us to cover 50% of the annual heat demand with solar thermal energy (100% from May to October). During the winter, they also use natural gas and bio oil. Moreover, it turned out that there is less heat loss in the storage than expected, so that is very positive too.


Finding the space for a large-scale solar thermal plant can be difficult. In Dronninglund, the plant has been situated about three kilometers outside of town, and having the plant located outside of the city’s inhabited areas works really well. Here there is enough space and a more stable underground. The installation is designed to have a lifespan of at least 25 years, during which the energy prices will be known. If the plant outlives this period, further cost savings await.

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