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Denmark’s first house with an energy surplus

11 November 2011

A pleasant indoor climate and no energy costs. This is a fact of life in the Zero+ house – the first home in Denmark that produces more power than it actually consumes. A family house that supplies its own heating and electricity – and even generates excess electricity. It may seem odd, but these are the facts when we’re talking about the Zero+ house in central Sønderborg, southern Denmark.

“At first it was a strange feeling to live in the house, because there were things in it which we had not tried before. But we like it very much now,” says Lone Midtgaard Wrang. Together with her husband, Tom Toft Kragh, and their one-year-old daughter, they own Denmark’s first Zero+ house. One of the things they had to get used to was that it is not necessary to open the windows.

The superbly insulated house is installed with a ventilation system with heat recovery, which ensures that half the air inside is replenished automatically every hour. ”We have a fantastic indoor climate. Living in this kind of house, you don’t ever see balls of fluff in the corners or mould in the bathroom. At the same time, it’s very allergy-friendly,” says a delighted Lone.

The house covers 200m2, is state-of-the-art and extremely comfortable, with a special combination of technologies that reduces its energy consumption. The technical solutions for most of the total heating and power supply are supplied by Danfoss. This includes the ventilation system with heat recovery (which sucks out the used air and circulates fresh air containing comfort heat), the ground-heat system and the energy-efficient heat pump that produces the necessary heat and utility water. The heat is emitted via fast-acting floor-heating, a SpeedUp system from Danfoss, which reacts and regulates the temperature in just 15 minutes.

The need for power is covered by 60m2 of solar cells mounted on the roof (via a Danfoss inverter, which transforms the sun rays into electricity). In the first year this produced 5,160 kWh, despite the fact that the solar cells were covered by snow for 2 ½ months this winter. Since the family has only spent 5,133 kWh, this left them with a surplus of 27 kWh from living in the house for one year.

“We have made it a sort of competition for us to monitor the power consumption, but we do not compromise on quality of life. We wash and tumble-dry as much as we usually do,” says Lone. The house is connected with Sydenergi’s local combined heat and power plant via the electricity network (Sydenergi is an energy supplier company in southern Denmark) but because the house normally has a surplus of electricity, the power consumed is not usually supplied by the company.

However, when the solar cell power production is too low to cover the consumption, the public electricity network does come into play. On the other hand, when the sun is shining and the solar cell system is working to its full capacity, the house actually transfers excess electricity to the network. Sydenergi’s remote reading of power meters gives the family the opportunity to monitor their consumption and make adjustments if consumption is on the increase.

The Zero+ low-energy house in Sønderborg is the housing of the future. The house is CO2-neutral and shows that there is a healthy economy to be had out of building houses that produce more energy than they consume. In the case of this house, it has been necessary to receive contributions from sponsors of the technical equipment but Lone Midtgaard Wrang and Tom Toft Kragh have no doubts; their house is the future.
They have attended a mini-course organised by Sydenergi to learn how to make optimum use of a low-energy house, but Lone says: “Honestly, there are only a few things we needed to get used to. Apart from that, we live a perfectly normal life – except for the fact that we save 2,687 Euros on our annual energy bill!” So far, the family has spent some of their power surplus on their electric lawn mower. Next on the agenda is probably buying an electric car, as soon as they become more common, which they can charge using the excess power. “In fact, car-use is probably the last area where we could still reduce our energy consumption,” says Lone.

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