Terraforming the Sahara

Dealing with the Sunlight

Sunlight in the desert can be both an enemy and a friend. In one sense it is a prime cause of elevated temperatures, and to expose flora and fauna to the desert sun for extended periods of time can be deadly. Yet on the other hand, the sun can be used to generate energy and can be shielded with the most primitive of technologies. A system of levels might be called for, where solar power systems occupy the upper level, and a secondary level receives partial or indirect sunlight which can feed plants, followed perhaps by lower levels which can be inhabited by more suburban activities.

Using Solar Energy

Solar technologies are a spectrum of mechanisms, from the energy efficient to the inexpensive per square meter. It is the second that we must prefer, in that we have a lot of area to cover and must do so in simplest manner possible. A semi-reflective mylar film or mylar covered glass which can be focused on centralized power conversion units is my preferred model. And as some of the light is transmitted, this would be available for crops and such.

One problem is how high to elevate the reflectors. Locating them at ground level is cheapest, but defeats the goal of having an ecosystem underneath. A height of two to three meters is optimal, in that it would allow for the coming and going of humans, however the cost of support structure is one that must factored in. A hybrid configuration which would have large areas at a lower height (say one meter), accessible but not convenient to humans, and then access passageways of two to three meters seems more practical.

Another problem is their geometry - that is, the angle of each segment and the location of the focus points. A popular and inexpensive lense, called a Fresnel Lense, is one which from a distance is flat, but that grooves have been cut at various angles to simulate the curvature of concave or convex lense. A similar approach can be taken with reflectors, so that the paths of the reflected sunlight meet at points where it can be processed into a more useful form.

Man-made Shade

As anyone who has walked around an outdoor mall in Southern California can tell you, shade makes for a pleasant afternoon. The Spanish Missions, built of adobe, had an architecture which was both open and shaded. For plants, a little shade can make the difference between roasting to a crisp and flourishing.

Most man-made shade is going to be derived from poles, towers, and buildings. Durability is vitally important, as you don't want to lose it in the first major storm. How close to the ground the sun screen is also an issue - the higher it is, the more average shade it casts but also the more susceptible it is to the wind and the weather. Suspended sails or nets might be used, or the shade might be made of bricks, concrete, metals, or even wood. Local materials will be preferred because of cost and transport.