HOT|COOL NO. 4/2023 "Technology and Sustainability"


Heliac solar panels generate heat using large lenses that focus sunlight the same way magnifying glasses do. This allows the solution to meet the heat demand even in district heating (DH) networks requiring output temperatures up to 130°C. In fact, the panels may deliver 160°C if needed. The solar field heats pressurised water in a closed loop deliver- ing the generated heat to the DH system via a heat exchanger connected to a storage tank installed at a peak load station. Integrating into the network via the storage tank makes it easy to control both the output and adjust the existing heat pro- duction to balance demand and supply. The property of the pressurised water is the same as what is used in the DH pipes, i.e., without the use of glycol. Avoiding glycol eliminates environmental risks and also improves the water’s viscosity, thereby slightly reducing the pumping pow- er needed. Instead, to counter the risk of freezing, the solar field circulates the return water in its pipes. This is cheaper

By Jakob Jensen, Commercial Director, Heliac

A full-scale, 1.6 MW solar field is in operation in Hørsholm, Den- mark. It produces an estimated 1,400 MWh of heat annually for the local DH network operated by the company Norfors. Norfors’ primary heat production is based on waste incinera- tion. Norfors supplies households in five municipalities north of Copenhagen with DH. Integrated into one of Norfors’ storage tanks, the solar field re- ceives DH return water at 40°C and heats it again to 90°C-110°C before returning it to the network. The specific temperature is adjusted according to the network’s demand which typically runs on higher temperatures in the winter than in the sum- mer.

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