The sea off the coast of the northern-Swedish town of Sundsvall is often covered with ice in the winter. But that does not stop it being full of heat – heat that can be exploited. And that is what they do at Permobil AB, makers of world renowned electric wheelchairs.
When people talk of heat pumps they generally refer either to ground source energy obtained via boreholes, or systems that use pipes laid in shallow ground. However, a heat pump just needs a few degrees of heat – where that heat comes from is a secondary consideration. At Permobils factory in Sundsvall, the heat comes from a cold sea – the Baltic Sea.
No less than ten loops of piping, each 500 m long, have been laid out at a depth of 15 – 20 m in the sea close to the Sundsvall factory.
These five kilometres of pipe are connected to four NIBE Fighter 1310 pumps, each with a capacity of 30 kW. The system provides heating for offices, warehouses and production units with a total floor space of 3,300 m².
“I installed my first water source heating system back in 1981”, NIBE regional manager, Tommy Landin, remembers.
“It’s a pity more people don’t use it, the investment costs are much lower than when you have to drill or dig. All you have to do is go out in a boat and lay the pipes down, with weights every second metre to keep the loops on the seabed.”
One big advantage with marine source heat is that it is always there. Even where the sea is frozen over it is warmer than the ground in the winter. You only need to go down a couple of metres to find water at 4°C, and that is more than enough to power a heat exchange pump, even pumps of this size.
Permobil’s system has been in operation since 2002.
“When we installed the system we put together three existing buildings, and at the same time added a new industrial building with a floor area of 850 m²”, explains Hans Engman, managing director of Permobil Produktion.
“That means that we can’t compare directly with the old figures, but the new system is extremely powerful, and we only need “top-up” power a few hours every year. On top of that, it’s very reliable – it’s been running for four years, and in that time we haven’t had a single disturbance.”