Denmark at global front within solar heating

In recent years, the number of large solar heating systems for district heating in Denmark has more or less exploded.

Around the country, you increasingly see large solar heating plants generating sustainable heat for the Danes.

“A tremendous development has taken place over the past ten years as regards the efficiency and price of solar heating, and we have been involved all the way,” says Simon Furbo, Associate Professor and head of the Solar Heating research group at DTU Civil Engineering.

Solar heating plants

Solar heating plants are defined as solar heating systems with a solar collector area exceeding 500 m².

At the end of 2017, 296 solar heating plants operated throughout the world, 111 of which were located in Denmark.

According to the International Energy Agency (IEA), 75 per cent of the world’s total area allocated to solar heating plants is located in Denmark. This exceeds the combined areas of Germany, China, Austria and Saudi Arabia, the countries occupying the following slots on the list.

In other words, Denmark is the world’s solar heating hub.

“It’s crazy! It would be easier to understand if the figure was per capita, but that’s not the case. The development is even more incredible when you look at a world map of solar radiation, where Denmark is definitely nowhere near the top,” says Simon Furbo.

However, the situation is not as strange as it might sound. Denmark has a well-developed district heating system. 64 per cent of our buildings are connected to district heating systems, which furthermore operate at relatively low temperatures. This offers great opportunities for solar heating as a heating solution, because it also works best at low temperatures.

Another factor boosting the interest in solar heating is that many of the small CHP plants are under pressure due to lower electricity prices as a result of the increasing share filled by wind power, and they have trained their sights on solar heating.

“Solar heating has quite simply become a better and cheaper alternative to natural gas, for example,” says Simon Furbo and points out that the energy invested in producing and installing even the largest solar heating plants in Denmark is paid back within one year.

Increased credibility

The large number of solar heating plants in Denmark makes this the natural focus for the DTU researchers. The researchers’ activities are particularly aimed at making measurements and simulation models for large solar collector fields as well as calculating benefits and optimization of field designs.

For instance, a 27,000-m² system with CSP (Concentrating Solar Power) solar panels that use oil as the heat transfer medium, is being tested in Brønderslev, North Jutland.

DTU is developing simulation models for the system and monitoring its performance. This is done in collaboration with the Danish solar panel producer Aalborg CSP. According to Jes Donneborg, Divisional Director, this collaboration offers the company access to expertise while increasing its credibility towards customers.

“In Brønderslev, DTU itself creates the measurement data and presents them. This is a seal of approval for our own measurement data, which is extremely valuable to us,” explains Jes Donne Castle.

DTU researchers’ knowledge about solar heating is also used in more general contexts and projects such as energy planning and the development of international methods and standards.

Right now, they are working closely with researchers from 22 universities and institutions throughout Europe to create a scientific research method that makes it possible to make a fair comparison between solar heating produced using different energy technologies. DTU supplies calculations and analyses.

DTU Lyngby Campus hosts DTU’s test facilities for solar heating research. Photo: Büro Jantzen.

China looking to Lyngby

The DTU expertise within solar heating attracts a large number of international companies and experts to DTU in Lyngby. This applies particularly to researchers from China.

“The Chinese have discovered that we are the only ones in Denmark conducting research into solar heating. This means that we are almost constantly visited by Chinese researchers and PhD students funded by the Chinese Research Council. This is extremely interesting, because Danish technology for large solar heating plants is really starting to roll out in China. Things are moving at a high pace, especially in Tibet, which is in fact one of the sunniest areas in the world,” says Simon Furbo.

Evidently, solar heating is here to stay as a sustainable and affordable energy source. But solar heating still only covers around two per cent of our total heating demand. However, this will change radically in coming years, according to the DTU researcher. He points to an analysis from the Danish Solar Heating Association, which estimates that solar energy will cover 15 per cent of the Danish heating demand in 2030 and as much as 40 per cent by 2050.

“I’ve been working with solar heating for 40 years and have watched the price development. Technology keeps getting more affordable, systems are getting simpler, and experience is constantly growing. We are nowhere near a peak yet.”