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| South glazing on solar Rest Area in Wyoming |
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| Placard showing all the solar features of the rest area. |
The rest areas have bunch of solar features (see placard just above), but the one that caught my eye was the fully automatic thermal shutters.
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| The automatic shutters. |
It has always been a bit of a problem in passive solar homes with lots of south facing glazing that while the south windows pick up a lot of useful heat when the sun is shining, they lose a lot heat when its not shining. While there is normally still a good net gain even with the large night time losses, its still a big improvment in performance if some kind of insulating shade or shutter can be used to reduce heat loss at night. The problem is that many people are just not up for raising and lower shades or shutters twice a day.
These very simple and automated shutters would be one way to take care of the problem. The shutters apparently use a set of two cylinders to do the work. One cylinder is mounted on the sunny side of the shutter and the other on the shady side. The two cylinders are connected by a tube. There is some fluid inside the system that partially fills one of the cylinders. When the sun is shining, some of the fluid in the sun facing cylinder vaporizes which drives the rest of the fluid from the sun side cylinder to the shade side cylinder. The shutters are carefully balanced with their center of gravity very close to the point the shutters pivot about. So, the transfer of the fluid from the sun side to the shade sides shifts the center of gravity enough so that the shutter pivot open. When the sun goes away, the opposite happens. Simple and clever.
A few more pictures and details here...
Have you got any ideas for automated window insulating devices? -- please leave a comment.
Gary