Thermal Energy Storage

Nordell has since 1979 been working on seasonal storage of thermal energy at Luleå University of Technology (LTU). His thesis "Borehole Heat Store Design Optimization, 1994" summarizes experience of the world´s first large-scale borehole heat store, constructed at Luleå University of Technology in 1982. This research started with the long-term aim to store solar heat of the summer for space heating during the winter. In more recent years seasonal storage of cold for space cooling during the summer was also included.

Sweden has been very active in the development of the borehole storage technology, both theoretically and practically. It has now spread to increasingly more countries. The most common system is energy wells for heating of single-family houses.

Today there are about 300,000 such systems in Sweden, which cover 15% of all heating in Sweden. The growth is about 30,000 systems per year and it is estimated that such systems will cover 30% of all heating in Sweden in the year of 2010.

During the last decade a few hundred large scale systems have also been constructed. These larger systems are often used for both heating and cooling of commercial and public buildings.