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The city of Luleå is growing and the municipality is looking to build a new urban area for about 5 000
people in an old air military area called Kronan. The concept is to build a green residential area, but
no details have been decided yet.
Usually the space heating in the Swedish cities is supplied by a municipal district heating system.
Luleå takes advantage of the gases generated in the local coke and steel plants. Using these gases as
fuel in a co-generation plant, which is connected to Luleå’s district heating system, means that the
Luleå community has the cheapest district heating in Sweden (Luleå Kommun, 2014). The heat
produced by these gases can easily supply the heat demand when the temperature is above -10oC,
but when it is colder than -10oC additional energy is required and there are different plants to
provide it. This extra energy comes from electricity and oil. In total, heat from the waste gases covers
about 90 % of the district heating.Moreover, the steel plant works the whole year while space heating demand depends on the
weather. When there is no demand, the heat generated in the plant is mostly dumped into the
Bothnian Bay, which means a significant waste of energy.
This project studies the possibility to store this waste heat in summer in order to supply space
heating to the new residential area. This storage procedure is possible using a borehole thermal
energy storage and the optimum parameters depend on the energy price.
The storage cost estimated is between 34 and 41 MSEK , with a payback of 7 to 9 years and it is able
to supply 14 GWh/year during the winter months fulfilling the heat demand for the new
neighborhood. The energy efficiency of the storage is above 75% from the fifth year of operation,
which means barely 18GWh of waste heat will be used to supply the district heating. |
