Svein Tønnessen is the Chairman of the Board of Directors of St. Olavs vei 20 in Lund in Kristiansand. The 67 apartments here were former municipal nursing homes that have now been sold and converted into a housing association.
When we learned about energy consumption, we went back. We had to do something, says Tonsin.
There was a backlog of maintenance work.
Old 60 watt lamps were running in the common areas around the clock. They were replaced by LED lights with motion sensors. Dark doors were replaced, and apartments were ventilated by heat recovery. And not least: they decided to take advantage of the heat of the sun.
Not great stuff
– Here’s the glory, it’s no big deal, says CEO Sven Tonesen.
It displays a solar collector of approximately 10 square meters. It consists of glass tubes with a liquid inside. They are connected to each other and capture energy from the sun and light. The liquid is transferred to the basement where it releases heat to the hot water tanks. Then it is sent back to get new heat.
Even on a cloudy day like this, it’s hot to pick up.
– Perhaps the temperature is 12-13 degrees that the sun or the light and our Lord give us, says Sven Tonsen.
heat the water
Water heaters were ready for replacement even before homes were converted into condominiums.
– There were two rust steel cans and only one was working. They had to be replaced, says Svein Tønnessen.
This made it natural to think of solar heating. When they decided, the plumber installed six large hot water tanks. The first two are double. This means that they contain both liquid from the solar collector on the surface and water to be heated by it. There is no electric heating in the cabinets.
Heat is sent from the roof to it and cooled water from the waterworks is heated. After staying in the “solar heat tanks”, the water goes to the electric water heaters. The water there is heated up to 70 degrees.
The benefit is the difference between cold water, which often maintains a temperature of 6-7 degrees, and the temperature of water when it is preheated by the sun. On this cloudy day of October, the thermometer shows 18 degrees. So the gain is 11-12 degrees.
up to 60 degrees
There is no problem in summer until the water temperature reaches 60 degrees. We prefer not to make it warmer. Then we heat it up to 70 degrees to take out the bacteria. After that the gain is 60 degrees, Tonesen says.
– But how effective is a solar collector in the coldest and darkest winter?
It is clear that cold has a negative effect on the plant. But it is the light that gives the effect. So I’ve never gone downstairs here and seen a gain that was at least 8-10 degrees lower.
– So it’s not just a sun and summer phenomenon?
– No, that’s what surprised me the most; Also how effective is this at the time of year when it’s cold and there is little sun.
Energy consumption more than half
Svein Tønnessen is also the Chairman of the Board of Directors of another housing association in Kristiansand that he can compare to.
Both housing associations have communal hot water tanks in the basement, in both places the boilers are fairly new and there are meters for water and electricity consumption in both places.
The difference is the solar collector system, which only the St. Olavs vei 20.
The electric-heated housing assembly uses only 28.3 kWh of water to heat 1,000 liters of water. in St. Olavs vei 20, only 11.6 kW is needed for the same. This is an average over the year.
– Solar collecting system reduces electricity consumption for water heating by 59%. Svein Tønnessen says it’s a lot of fun.
Recommended where you use a lot of water
The solar collector system cost the Housing Association 280,000 NOK.
– We calculated a six-year repayment period for the electricity price, which was in 2018 and 2019.
– Now the price of electricity is twice that price?
Yes, we may stop at a four-year repayment period. But the price of electricity should not be as high as it is now.
Christian Zachariassen in Sørlandet boligbyggelag believes that solar collector systems can be recommended for all buildings where a lot of hot water is used.
– It should be very suitable for swimming pools, gyms, laundry halls, schools and nursing homes. And of course also waterborne homes, says Christian Zachariassen.
Can be used all over the country
There is a little more energy gained from the sun in Kristiansand than in Tromsø, but this difference is not decisive. That’s the view of Bjorn Thorod, who leads the solar energy business at consultancy Multiconsult.
What determines profitability is the cost of construction and the price of energy. It is not solar radiation that determines profitability, Thorod says.
He points out that in Svalbard, where there is little sun, but also very high energy prices, solar energy is now profitable. Now it is most profitable in southern Norway because electricity prices are very high there.
—But we can use it on roofs, walls, and facades across the country, says Thorod.
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