As much as it was the merit of the solar collector field, it has no less value to the accumulation tank. It was possible to store the thermal energy from the wood chip boilers in the accumula- tion tank. It allowed us to produce the energy for the peak loads not to have to use other fuels. The total power of the wood chip boilers and flue gas condensers are a bit smaller than the peak load for the thermal energy of the city. The accumulation tank produces thermal energy in the time slots when the load is smaller and stores the difference between the produced ener- gy and the load. For example, at night, when the load is small, it is possible to make more energy than needed. The difference goes to the accumulation tank, and in the morning, when the load reaches its peak, the required difference, that wood chip boilers with flue gas condensers can’t cover, is taken from the accumulation tank, which is filled up during the night. An accumulation tank is an excellent piece of equipment, which is essential for solar thermal systems. But it also facil- itates work for other technologies, as in the above example. During periods of maintenance of boilers, it is possible to fill the storage tank and not use fossil fuels at the time of stopping. Cooperation between solar collectors and panels The latest project from November 2021 of implementing a 110-kW solar panel field will cover the need for electricity that needs the solar collector field. This will allow producing ther- mal energy next summer without using any external energy sources. Electricity is required to ensure the solar collectors’ function of circulation pumps.
understand how it works and its benefits. We are also trying to share production data at every opportunity so that everyone who wants to know and familiarize themselves with solar technologies can do it. Performance has been excellent. In the first full year, when the solar collector field was on the agenda, it produced in total 11’088 MWh, approximately 19% of the total annual thermal energy demand in Salaspils city. The rest was made by wood chip boilers (59%), flue gas con- densers (12%), and to cover the peaks – by natural gas (10%). After the first year, Salaspils Siltums experts researched how good the performance of the 1 m 2 solar collector is. The results were surprisingly good - 1 m 2 of solar collector annually pro- duces 511,6 kWh of thermal energy. The yearly sum of global irradiation is appr. 1150 kWh/m 2 , which means that the effi- ciency of the collectors was almost 45%. A significant amount of thermal energy from solar collectors is produced in 7 months of the year. From April to Septem- ber, solar collectors made at least 1’000 MWh each month, and in March, it was very close – 989 MWh. The most productive month was May, when 1824 MWh were produced. Compared to 2021, the overall produced energy has decreased – 10’023 MWh. The main reason is that the spring, August, and September were much colder than last year and cloudier. However, June and July were very sunny, and the collector field was quite productive – in June were 2’154 MWh produced, but in July were 2’200 MWh produced. So Salaspils Siltums produced all demanded thermal energy only from renewable energy resources from April till the mid- dle of August. It looks like no fossil fuels will be used to cover the demand of the city during autumn.
The whole project allowed a price reduction of thermal energy for the citizens of Salaspils city by 12,7%.
Now in writing, the heat price is 48,2 EUR/MWh, independent of the natural gas market fluctuations. Green production is not only environmentally friendly but also beneficial for thermal energy producers.
Production scheme
For further information please contact: Roberts Kaķis, roberts@salaspilssiltums.lv
18 HOTCOOL no.4 2021
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