Sunfab in Hudiksvall

Ground source heat pumps with 22 boreholes save 150,000 litres of oil a year

The hydraulics company Sunfab, based in the northern Swedish town of Hudiksvall, has invested hugely in ground source heat pump technology – for both heating and cooling. The company’s premises comprise some 2,500 m² of offices and other areas, plus 6000 m² of factory space – all of which is now heated, and cooled, by one of the country’s biggest ground source heat pump systems.

Before installing their ground source energy system, the Sunfab company was burning 100,000 litres of oil every year to heat their premises in Hudiksvall. Their oil bill would have been even higher, had it not been for the fact that the twenty-five machines in the factory were generating surplus heat to the tune of 20 kW each – that’s 500 kW in total! With the extension to their premises that has now been made, Sunfab would have seen their oil requirements soaring to 150,000 litres. What is more, the expanded capacity brought with it another problem: large amounts of heat that needed disposing of.

Energiventilation AB designed a tailor-made solution to deal with both the heating and cooling requirements of the factory, using heat-pumps from NIBE and no fewer than twenty-two boreholes. It has taken nearly two years to go from the drawing-board to the installation and operation of the system, at a cost of over €1,000,000.

The system now heating the factory complex is technologically highly advanced. Five 40 kW NIBE Fighter 1320 pumps produce a total of 200 kW of heat – energy which the cooling medium (brine) in the system’s piping collects from twenty-two boreholes! The system represents a saving of roughly 100,000 litres of oil every year. That’s good enough as it is – but what is really elegant is that the boreholes do not only extract heat energy from the rock into which they are drilled.

Using a water-based system, over-heated air from the factory is piped down into the boreholes that each contains four loops, instead of the usual two. Something that gives a fifty per cent higher cooling capacity.

‘It’s fair to say we’ve put together a pretty intricate solution’, says Bo Rönnestrand, project manager for the installation of Sunfab’s system. ‘Fans in the production areas blow the hot air across pipes containing water at a lower temperature. These are called cooling baffles, and are cooled, via heat exchange units, by the cooling medium in the borehole loops. The cold water in the baffles might have a temperature of about fourteen to sixteen degrees, but on its way back its temperature might have risen to as much as twenty degrees. This is then lowered again by the cold form the bore-holes e t c.

There is, in other words, an ingenious flexibility to the system: in the summer, when the premises do not need to be heated, this surplus heat is led down into the boreholes, where it accumulates, gradually warming the rock. This warmth can then be exploited in the winter. During the cold part of the year, the over-heated air from the factory is not led back underground, but is instead channelled directly into the heat pumps which provide the rest of the premises with heating.

‘Instead of water entering at between zero and two degrees, in this system it’s entering at between fifteen and twenty degrees’, explains Bo. ‘That means much greater efficiency from the heat pumps, and very low heating costs.’

So, using NIBE heat pumps, Sunfab and Energiventilation have succeeded in cooling a large factory which produces a lot of surplus heat, without having to install a separate cooling system. And they have done so with a system that uses minimal amounts of energy, for both heating and cooling.

‘In Spain they call heat pumps climate machines’, says Tommy Landin at NIBE. ‘It’s about time we started using the same expression in Sweden, too.’