architecture energy sustainability

Two ways to make a solar wall

We know about putting solar energy on our roofs. It’s less common to see vertical surfaces used to capture the energy of the sun, but the south facing wall of a large building is a huge solar opportunity. It doesn’t need any sophisticated technological solutions either. Since the future needs both, here are two different ways to create a solar wall, one low tech and one high tech.

First of all, the low tech version. During the 1960s French architects experimented with passive solar walls. They are created by placing a glass wall a few inches from a south-facing outer wall, so that heat is trapped in the gap. (I was reminded of this yesterday while walking through a very warm south-facing glass corridor at a school.)

trombe wall

Vents are added at the bottom of the wall and the top, so that warm air can be funneled into the building as cheap solar heating. It’s called a Trombe wall, and this appropriate technology solution can be incorporated into modern or traditional homes.

There are more sophisticated versions. You can add computer-controlled fans and thermostats. A company called SolarWall sells a related concept that provides solar heating for industrial buildings through smart wall cladding. I’ve also written about this solar heating company on Native American reserves, which retro-fits homes with a system that works on the same principles.

The high tech version of a solar wall is to clad it with solar panels. That’s something that is easy enough to do if heliatekyou’re designing a house from scratch. It’s harder to add afterwards because of the weight, and because it can look weird. But new solar film is likely to change that. One company that is already producing solar film is Heliatek. They produce very thin solar PV on a roll, which means it can be made at any size. It’s lightweight but durable, and it can be applied directly to the outside of buildings. It’s thin and transparent enough that it can even be applied to glass.

Heliatek film is still expensive, but it is commercially available, and prices are falling as production expands. It uses a fraction of the materials and the energy needed to produce traditional silicon based PV. Give it a few years, and it may well grace a wall or a window near you – more in the video below.

That’s two ways to create a solar wall. As a bonus third, you can also build solar hot water into a wall. Here’s an award-winning sustainable home from a few years that does it beautifully.

5 comments

  1. Good article. I think the trombe wall is not necessarily such a good idea. The main reason is that the thermal mass of the wall represents heat that doesn’t get into the building that is then radiated through the glazing to the environment at night. I think it is better to have a low-thermal-mass well-insulated back to the solar collector for this reason, and keep the thermal mass inside the building.

    I saw this very interesting paper recently about using reflectors to double the heat/light coming through windows and skylights. You or your readers might find it interesting.
    http://www.nmsea.org/Solar_Fiesta/Solar_Fiesta_2006/Tech_Sessions/Steve_Baer_Reflector_Shades.pdf

    (I saw it listed on builditsolar.com, which has lots of interesting projects, including many solar space heaters)

    Cheers, Angus

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