Garden innovations - geodesic greenhouses

If you've been to the Eden Project, you know what I'm talking about, but did you know that you can have a geodesic (or dome) greenhouse in your garden? And it's not just a gimmick. The Eden Project is built in a geodesic dome for a very good reason - a dome is an energy efficient structure that creates an optimum space for plant growth.

The other reason this is a true innovation is that all the new geodesics on the market are solar, and they rely on solar energy for both heating and cooling. This means they are able to extend the growing season without the use of large amounts of fossil fuel.

The dome in winter:

The principle of winter growth is to try and capture the heat of the sun during the day and store it inside the greenhouse so that it can be used to slow down the heat loss at night. This gives a higher ambient (air) overnight temperature, to allow year-round growth.

During the day when the interior to the greenhouse is hot, most geodesic greenhouses use an under soil heating system which is usually photovoltaic panel that creates electricity to drive the fan, which blows hot air through ducts buried in the floor underneath the growing beds. This soil heating system is entirely free of cost. It's not the only way to conserve heat though. The second way is to store solar energy inside the greenhouse in a large water tank which stores solar energy by absorbing the sun's rays. This works because winter sun shines on the dark metal tank, which absorbs heat all day long and at night releases this heat back into the greenhouse structure. Finally, geodesics have a smaller glass area per pane and a better edge insulation, so frost finds it hard to penetrating under the wall of the dome. Most designs now claim they require only heat required by a conventional greenhouse structure.

The dome in summer:

In the summer all greenhouses get hot. Traditional greenhouses usually have vents and many have a ceiling or exhaust fan to cool the structure.

Geodesics too have vents, but they are solar powered consisting of an activator which opens the vents at a pre-determined temperature controlled often by a cylinder of wax or gas, which expands when the greenhouse gets hot. Many domes have an exhaust fan too, often powered by a solar panel. Finally, the water tank helps keeps the dome cool - solar cooling is highly effective if there is a large amount of water, normally 1000 gallons and above. In domes this is often used as a water garden for aquatic plants and fish.

Garden innovation geodesic greenhouse photograph by sylvar, used under a creative commons attribution licence.