District Heating Customers Save Money

In Dronninglund, Denmark, an unused area of land has been utilised for cost savings and a greener world.

Cost savings

It all began when the 40-year-old oil boiler needed replacement. This was a good occasion to rethink the installations, and 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.

Key plant data

• Collector area (effective): 37,573 m2
• Number of solar collectors: 2,982
• Storage capacity: 62,000 m3
• Share of annual heat demand: app. 40%
• Calculated peak capacity: 26 MW
• Calculated annual production: 18,000 MWh

The heat is stored

The total installation consists of a 37,573 m2 solar heating plant 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 we can store the excess heat and use it 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, we also use natural gas and bio oil. Moreover, it turned out that there is less heat loss in the storage than we had expected, so that is very positive too,” Production Manager Johan Frey tells.

Location outside of town

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. Johan Frey tells:

“Having the plant located outside of the city’s inhabited areas works really well for us. Here, we have enough space and a more stable underground. It only costs one degree in heat loss transporting the heat, so in that respect it is definitely reasonable.”

The plant is financed with a fixed interest rate and 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.

Source & photos: Arcon Sunmark