Passive Solar using a Water Wall

Jack’s passive solar home with Solar PV

I have blogged before on my friend Jack’s passive solar home. He toured us last fall Bellingham, Washington: Passive Solar, PV and Solar Thermal home.

Passive solar, combined with a good heat sink (concrete, stone, masonry, water) creates one of the most cost-effective methods to heat and cool your home. With passive solar you have few moving parts or maintenance and use no mechanical devices. You let the earths natural forces work for you.

The elements of good passive solar consist of south-facing windows (northern hemisphere). The sun’s radiation passes through the windows and is absorbed by surfaces inside the (insulated) envelope of the home.

In Jack’s case this is a large wall of brick/concrete, polished with a deep colouring as well as concrete flooring. This is the thermal mass which acts as a heat sink, absorbing the sun’s heat during the day and letting heat off in the cooler evenings.

Jack’s concrete brick “thermal mass”

After the tour, we sat with Jack and he told us about a previous passive solar home he had built and lived in several years ago. This one had a water wall. A water wall is said to be an even more effective heat sink than masonry. Water can hold two and a half times more heat than concrete per volume.

This is not to be confused with a Trombe Wall, although the principle is the same. Jack’s water wall consisted of tubes that were one foot in diameter and eight feet high, an optimal heat sink.

Water walls are effective because they provide thermal mass and quicker heat exchange than concrete or masonry. They are said to have a 10 to 20 percent advantage over slightly larger masonry walls in moderate climates. In addition, energy savings in heating and cooling can be expected in the 70 to 90 percent range.

Sun-lite® Thermal Storage Tubes

It took a bit of looking to find an example of a water wall similar to  Jack’s, but I found some through the Solar-Components.com site. They look like they come from a 60’s Science Fiction movie, but according to Jack, you can’t beat the effectiveness. The Solar-Components site also shows drawings of a Direct Gain Water Wall and Controllable Passive.

Solar water walls have also been made out of other materials but these ones are made out of a clear fibreglass. They can be filled with dyed water to increase efficiency or for aesthetics. The example here has a blue dye inserted.

Don’t even think of putting fish in them as they wouldn’t be able to handle the temperature fluctuation.

Beam me up Scotty…

Cheers, your eco friend.