100% renewable district heating

Example of SUNSTORE2

The SUNSTORE2 was a project to enlarge the solar collector area of the original plant with approximately 10,000 m2 and add pit heat storage, to enable the solar collector plant to cover 30% of the town’s yearly thermal energy consumption.

The project had the following objectives and results:

  1. The design of a pit heat storage to be constructed at less than 67 EUR/m3 at a size exceeding 10,000 m3 and less than 30 EUR/m3 at a size exceeding 50,000 m3 (price level 2001). 

    The result was, that the 10,000 m3 pit heat storage in Marstal was constructed at 67 EUR/m3 and using the same prices/unit a 100,000 m3 storage can be constructed at 31 EUR/m3 (price level 2004)

  2. The design of a ground mounted flat-plate collector with an efficiency improvement of at least 10% without a corresponding increase in the price. 

    The result was an efficiency improvement of 19% and a 5% higher price. Thus the cost efficiency was 13% better.

  3. Demonstrate a 10,000 m3 pit heat storage with floating cover and a 10,000 m2 solar collector field including demonstration of different flat plate and focusing solar collectors. 

    The 10,000 m3 pit heat storage was built and six different solar collectors are demonstrated.

  4. Integration of solar heating with a 30% solar fraction in a conventional district heating system. Price of energy 0.045 EUR/kWh. 

    In Marstal 8,019 m2 of new ARCON-HT collectors and 10,000 m3 pit heat storage was established for less than EUR 2.28 million. The production is around 3,800 MWh/year. If the financial costs are 6.7%/year, the heat price is 0.04 EUR/kWh. The plant has covered 28% of the total energy production in both 2007 and 2008.

After the SUNSTORE2-project, the solar plant Marstal Fjernvarme now covers the heat demand nearly 100 % in the 3 summer months. The number of clients connected to the district heating system is today 1,460 and district heating covers 95% of the heat consumption in Marstal. The SUNSTORE 4 project makes it possible to connect Ommel, a small village, with another 120 clients.