District Heating and Cooling
District heating is a heating system consisting of a pipe network, filled with hot water, and heat sources (from residual heat or a heating plant). The hot water is circulated by pumps, from the heating plant to the client and back again to the heating plant. A heat exchanger at the customer transfers the heat from the district heating network to the building’s own heating and hot water systems. The return water continues out through the return pipe and is pumped back to the heating plant, where it again is heated. The temperature of supply water ranges from 65 to 120 degrees and return between 25-75 degrees. The most common methods of producing hot water for a district heating system are waste heat, heat pump, combustion, electric boiler.
District cooling uses the same principles as district heating. To cool the customers’ air, cold water is being distributed in a pipe network to the properties’ ventilation systems. The water temperature is approximately 6 degrees Celsius when it reaches the customers and the return water is approximately 16 degrees Celsius. To produce district cooling the most common methods are free cooling (cold water from lakes, seas or other waterways), absorption cooling (uses a heat source to produce cold) and heat pumps (produce heat and cold at the same time).
Both district heating and district cooling have the benefit of scale and can use biofuels. For society in general district heating and district cooling offer major environmental benefits and allow for economic use of natural resources.
A district heating network allows for flexibility in choosing the fuel, which makes it possible to gradually switch to renewable resources.
The water in the district heating network can be heated in a heating plant…
…or the water in the district heating network can be heated by waste heat from waste incineration, industries, the underground etc.
The most common way to produce district cooling water is cold water from seas, lakes, rivers and other waterways.
Another possible/ complimentary way to produce district cooling is through absorption cooling – heat transformed to cold.
In absorption cooling, waste heat can be used as a resource for district cooling too.