Austrians built a Solar House Prototype called "Gemini".

The cylindric building is turning with the sun to optimize the solar energy created from the solar panels on the large glass areas.
The 20 ton house turns 180 degrees during the day and turns back during the night.
To keep the house warm during the night automatic isolation panels slide over the glass areas.
The prototype house was in a test phase over the last 2 years. 2004 serveral "Gemini" houses will be built, but without the turning. To complicated to maintain and the improvement seem not to be worth the hassle to maintain the mechanics of turning a 20 ton building every day.

Project Description in German ( Translated in English by Google )