Oppsal is well suited for district heating, as it has a high population density and some large housing cooperatives, many of which have older oil-fired installations. The old heating installations are not particularly environmentally friendly, and this in an era where investments in heating installations are being reviewed, whether with a view to full renovation or replacement with alternative energy sources. Many of the housing cooperatives considered alternative solutions, but increased demand for district heating from residents, high security of supply and lower local pollution tipped the balance in favour of district heating when the new main pipeline from Klemetsrud to the centre enabled Oppsal to be connected to the district heating grid in 2009.
However, the height difference from the main grid has thrown up a number of challenges. The Oppsal plateau is situated around 150 metres above sea level, which is somewhat higher than the main pipeline which runs past Østensjøvannet. To avoid the pressure in the pipeline network becoming too great, a special heat exchanger was constructed, through which the water is led, with the result that there are two independent circuits.
The Oppsal, Fuglemyra, Vetlandsveien, Skøyenåsen, Solhøgda and Oppsaljordet housing cooperatives, which together have an annual energy consumption of around 20 GWh, will be connected in 2012. “Twinned” Oppsal school and Vetland school, and Oppsal centre, have already been connected, while on the edge of Oppsal, district heating is being delivered to Manglerud school.
As in other places, in Oppsal district heating routes are being constructed using insulated steel pipes designed to withstand temperatures of 140° C and pressure of more than 20 bar, which is two to three times higher than the pressure in water pipes. This in turn imposes stringent performance requirements.