Solar John in Wyoming with Automatic Solar Shutters

OK, this is a solar John, not a solar home, but it tackles one of the challenging problems for direct gain solar homes  -- how do you control the heat loss from the large south facing windows without making the owners open and close insulating shutters or shades twice a day?

This is a rest stop on I25 in Wyoming.   It has a large south facing glazed area for passive solar heat gain.  To control heat loss at night, it has a very clever set of automatic insulating shutters what open when the sun shines and close when there is no sun.

Wyoming has 19 of these solar rest areas.




This sign explains how the solar features work.  It included passive gain through large south facing glazing panels.

To me, the most unique feature is the automatic insulating shutters that open when the sun is shining and close at night or when the sun is not shining.  So, without any effort on the part of the occupants, the system gains heat when the sun is shining, but also avoids the large heat loss that goes with large glazed areas.


The picture above shows the large automated, insulating shutters from the inside.

The shutters appear to use set of cylinders to power the opening and closing.  In this scheme, the cylinders work in pairs.  One cylinder is on the sunny side of the shade, and the other on the shady side.  They are connected by a tube.  When the sun warms the sunny side cylinder, it vaporizes some of the fluid in the cylinder and this pushes fluid out of the sunny side cylinder, and through the tube into the shady side cylinder.  The shift in weight causes the shutter to open.  

When the sun goes away, the fluid returns to the the sunny side cylinder, and the shutter closes.

The fluid in the cylinders has to be one that will vaporize and condense at the right temperatures.  Freon used to the choice before it was recognized as an ozone depleting gas -- there are other ozone friendly fluids now days.

At least that's what I think is going on -- if you know different, please let me know.

I believe that Zomeworks makes (or used to make) a product similar to this, but was not able to find it on their site.

Some more pictures of the shutters and cylinders:


Here is a little more on them A Guide to WYDOT Rest Areas

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Gary March 15, 2011