The worlds greatest solar collector plant

The world’s greatest solar collector plant is placed in Marstal on Ærø in Sydfyn in Denmark. It is 18 365 m2 big, and it covers 30% of Marstal’s district heating needs. From the 1 of May to the 1 of November Marstal city’s consumption is 100 % covered with the solar collectors.

The whole idea of a Solar Collector Plant started in 1993 when the local swimming bath had economic problems, and Marstal District Heating wanted to find more environmental friendly fuel. In 1994 they placed a 75 m2 solar collector on the roof of the swimming bath, and they found out that the solar collector was very useful.

In 1996 Marstal District Heating decided to place 8000 m2 of solar collectors on a field near the district heat works.

The solar collectors are black, they are turned against south, and the slope is 30 to 40 degrees. In each solar collector there is a pipe system, and in these pipe systems the water circulates through. The water visits 10 solar collectors before it reaches the houses.

When the sun is shining they have managed to control the temperature of the water, so it is 70-72°C.

Because the employees in Marstal District Heating have worked so hard, they have managed to reduce the electricity consumption of the pumps with 75%.

The solar collector plant was increased in 1999 and again in 2003. In all the solar collector plant was increased with 9000 m2. More consumers were also connected to Marstal District Heating, so the increase was necessary.

Every year Marstal District Heating saves consumption on 820.000 litres of oil and that is 2.200 tons of CO2 that the nature will be saved for each year.

In the sunny weather in the summer 2003, just after the increase of the solar collector plant, Marstal District Heating ran into problems. The new solar collectors actually got too productive and they employees needed to think of a solution. The problem was that the water started to run out through the safety valves because it reached the boiling point. So the solar collectors were painted with white shadow pasta – some kind of white paint, which dims the effect of the sun.

When the solution with white shadow pasta didn’t work well anymore they started to pump the water through the solar collectors again to cool in the night. This method worked much better than the shadow pasta and it is still used today when the water gets too hot.

In 1996 Marstal District Heating established a big steel tank to save the heat water. It contains 2100 m3 of water, which is the same as Marstal´s consumption in 3 to 5 days.

As an experiment they established a 3500 m3 store in 1998 but they needed more store capacity and because of that they excavated a 6, 5 metres deep pond, which contains 10.000 m3 of water.

Marstal District Heating says that they will explore the opportunities with environmental friendly district heating operation. And each year they share their experiences with the 2000 visitors from all over the world.