District heating briefly explained

Illustration district heating

District heating is a separate energy system that forms a natural part of the energy supply for towns and cities and densely populated areas.

Statkraft is a European leader within renewable energy and focuses on further development of district heating in the Nordic region.

Because the heat distribution takes place locally, district heating is likely to be developed in close collaboration with local authorities and end users.

Principle for district heating

District heating involves the heating  of water. In practice a district heating plant can be linked to a central heating system that supplies one or several buildings with hot water. The hot water circulates between the heat production plant and the customer in insulated underground steel pipes. The pipes are often laid together with other infrastructure such as telecommunication lines and electricity cables, and experience average heat losses of around π ten percent.

Customers use the water to provide heating through under-floor heating π or radiators, and to heat tap water. A number of different energy sources are used to generate district heating.

These include waste, biofuel, heat pumps, landfill gas, natural gas, propane/ butane gas, electricity and fuel oil. Several different energy sources can be used at the same time in a single district heating system. This results in a stable and flexible supply of heat to the customers. If a particular energy source is unavailable for a period of time, another source can be used to heat the water that is distributed to the customers.

Expressions such as base load and peak load are often used in connection with district heating, where the base load is likely to consist of waste or biofuel, and the peak load of oil or gas. The base load is the cheapest energy source. However, major variations in capacity requirements over the course of a year mean that a peak load is required, which is generally a more expensive energy source. A peak load is also required in order to guarantee security of supply.

In Trondheim energy waste represents the largest and most important energy source as well as the base load for the district heating system. Bioenergy represents the main heating source at Statkraft’s Swedish plants.

Impact on the environment

District heating based on renewable energy sources has a positive environmental effect as this form of heating can replace less environmental friendly heating such as fuel oil or electricity based on non renewable energysources. Waterborne heat creates a good indoor climate. The circulating water has a temperature of π between 50-80°C, and there are no problems with dust combustion and electromagnetic fields.