Danish district heating company reduce heat loss by 25% with a low temperature zone

The situation

Gentofte and Gladsaxe have one of the fastest growing district heating networks in Denmark. Situated in the northern part of Denmark’s capital city of Copenhagen, the municipalities have a mix of commercial buildings, high-rise residential buildings and single-family homes.

Johan Sølvhøj Heinesen had been looking for a way to lower the temperature in parts of the system. “We have old district heating networks, where the supply temperature is close to 110 degrees Celsius during cold winters,” he says, whereas 65 degrees Celsius is enough for the single-family housing areas.

As a result, we lose a lot of heat,” he says. “The high temperature shortens the lifetime of our pipes, and it may cause operational problems in our installations.” Thus, the district heating company was looking for a way to lower the supply temperature in sections of the network while keeping it higher in the rest of it.

They tried building their own low temperature zone at a local hospital. “We gained quite a lot of operational experience,” says Johan, adding that it was an expensive investment. “The payback period on our homemade solution will be about 20 years.” As a result, he was looking for something cheaper and simpler. And if it could be hidden away underground without boxes or containers above ground, even better. “For a long time, I’ve been looking for an easy solution – plug and play, supplied by the industry – ready to put in the ground, so you wouldn’t see anything.”

The solution

Grundfos delivered what Johan was looking for: an iGRID Temperature Zone, complemented with monitoring and control. “There’s a small electrical cabinet on a street corner, and there’s a manhole covering a pump and other technical components,” he says. “In addition, we have a solution that’s financially better than what I expected.”

The iGRID Temperature Zone is a mixing loop that uses a shunt pump diverting some of the water from the return pipe and pumping it back into the supply line, thus lowering the supply temperature. By monitoring the critical parts of the heat network with pit measure points, the mixing loop adjusts temperature to meet the exact consumer need on a real-time basis, lowering the heat losses even further and continually improving comfort. “We reduce our heat loss in the network considerably – an save a lot of money,” says Technical Manager Magnus Justesen. “By installing this shunt, we expect to save up to 25% of our heat loss in the zone. And we expect the payback period to be three to five years.” He adds that in district heating, this time for return on investment is considered extremely good.

Part of what he appreciates about the solution is its user-friendliness. “The Grundfos pumps allow for an easy setup of control parameters,” Magnus says. “We don’t have to use a PLC to control our pumps. Everything is built into the pump. It works very well.”.

"Grundfos has supplied remote monitoring and control of our low temperature area,” he adds. “They’ve installed a number of measurement points, so we can monitor pressure and temperature in the critical parts of the system.” That means the company can lower the supply temperature even further and use the solution for peak shaving by raising the temperature in the morning and lowering it later after the morning peak, he adds.

The outcome

Johan Sølvhøj Heinesen says, “I’d say this is the future of district heating. We need lower temperatures in the heat network. And we need to be able to utilise lower temperatures in our homes. 

This is a small solution right here. But by doing this, we lower the energy consumption in our area. We lower the return temperature, which means lower temperature to the power stations and the waste incinerator – and so that means better utilisation of energy. It has a positive effect all the way through the system.”

“When we reduce the temperature, we reduce CO2 emissions considerably”, concludes Magnus Justesen.