Wednesday, November 24, 2010

Examples of Earth Charging

24 Nov'10: Here are two notable examples,
IKEA store in Tempere, Finland, the 37,500 sqm store will be heated from the ground, 60 200m deep boreholes, to be used for cooling the building in summer, and for drawing heat in winter. The article focuses on the technology of drilling through such deep rock, so I am not sure if they also use solar panels in summer. But commercial buildings produce a lot of internal heat from lighting and other internal gains, so if this is stored underground it's better than just blowing it into the atmosphere.

Xolar's roof
(image from their PDF document)
Xolar Group, Eberstalzell in Upper Austria, are a company making solar hot water systems so they are obliged to get it right in their new headquarters. It's a 21,900 sqm building that will eventually be totally passively heated and cooled. They have a huge number of solar thermal panels on the roof to provide thermal energy. The building is nearly airtight, so heat recovery is possible.
The perimeter of the building below ground is deep insulating walls, and they are charging the ground below with heat. The solar panels are charging the ground and the target temperature is 22ยบ. For the first seven years, they are using 3 biomass (wood pellet) boilers to maintain the rate of charging through the winter. After 7 yrs, the ground should be at a steady state, where regular solar input can keep the ground topped up, so the biomass boilers can be disconnected and sold.
They are aiming ultimately to run the building at 10 kWh/m2/annum, less than the Passivhaus standard of 15. There is a very large buffer tank of water at the heart of this, and the thermostats decide whether to use biomass or solar heat, depending on the season.
The article says that in Upper Austria, 32 percent of gross energy consumption is provided by renewable energy sources, biomass being 13% (I guess a large part is hydroelectric).
See also, PDF document.
PS thanks to a friend on the Navitron forum for alerting me to these.

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