Technology: Solar Heating

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Solar collectors for district heating, Snedsted, Denmark. Photo by INFORSE-Europe.

Solar Heating for District Heating

Solar heating is a popular technology for heating and hot water. In some countries, as Denmark and Austria, it is also popular for smaller and medium-sized district heating systems, using large solar heating modules, 2 * 6 m. For district heating, solar can supply 5-10% of the heat demand without heat storages and 15-30% with heat storages in Ukraine. A few Danish plants have large seasonal heat storages that can store the heat from summer to winter and then the solar heating can cover 50% or more of the heat demand. The seasonal storage tanks are usually insulated artificial ponds with heat resistant plastic liners and with insulation at the top and sides.

The fluid in the solar collectors is usually water with enough propylene as anti-frost agent to ensure no freezing during the coldest nights. The solar circuit is separated from the water in the storage tanks and in the district heating system with heat exchangers.

For district heating, the solar collectors are usually placed in solar fields on concrete blocks with grass in-between and a network of tubes underground to circulate the fluid.

Examples

Hedensted District Heating

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Photo: Solar collector and sheep that keep the grass low at Hedensted District Heating. Photo by: Hedensted District Heatiing.

In the town of Hedensted with 12,000 inhabitants, the district heating company inaugurated a solar heat plant with 11,000 m2 of solar collectors in 2019 to cover 14% of annual heat demand for the part of town connected to district heating.

Marstal District Heating

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In the town of Marstal with 2,200 inhabitants, the district heating company inaugurated a solar heating plant with 8000 m2 of solar collectors in 1996 to cover 13-15% of the heat demand. The has been extended in 2012 to 33,300 m2 solar collectors and a heat storage as an insulated pond with 75,000 m3 of hot water. The solar provides 50% of the heat demand of Marstal. Some adjacent villages are also connected to the district heating system.

Technical parameters

  • Size: typical 10,000 m2 solar collector and 2000 m3 water tank as day-night (diurnal) storage, but plants can be more than 10 times larger.
  • Efficiency depends on temperatures of fluid and ambient temperature. For typical flat plate collectors for solar heating can be efficiency of 55% in summer and 35% in winter with 75’C forward and 40’C return temperatures of fluid.
  • Yield: 500 – 750 kWh/m2 solar collector in Ukraine climate (low value in North, high value in South), with monthly variation from 10-20 kWh/month in December – January to 85-110 kWh/month June-August.
    Photo 4
    Figure: Example of yield in Odesa, annual yield 750 kWh/m2.
  • Lifetime: Technical lifetime 30 years
  • Space requirements. Including storage, technical buildings etc., the land area needed is around three times the area of the solar collectors. For a plant with 10,000 m2 of solar collectors, this is 30,000 m2 of land.

Financial parameters

  • Nominal investment:
    • for plants 10,000 – 50,000 m2 excluding storage, use 250,000 € + 167 €/m2;
    • for day-night storage of 0,2 m3/m2 solar collector: 60 €/m3 0 12 €/m2 solar collector
      (these prices for typical for Denmark. Prices in Ukraine will be similar, but with large production in Ukraine, prices can be lower).
  • Fixed O&M: 0,04 €/m2
  • Variable O&M: Electricity cost for 3,1 kWh/MWh heat
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Example for economy of plant of 10,000 m2 in Kyiv and Odesa.

Sources for information

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Cases
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