The Premise


The deserts are growing everyday. Footby foot we lose habitat that is already trying to cope with thepressures of human development. Desertification is a global problem,and the remoteness of the condition belies its caustic effect onglobal economic stability and peace. The famines it causes andeconomic disparity that it perpetuates has a negative impact on even'first world' countries. Fueling the process are a slew of humanactivities that range from poor irrigation and agricultural practicesto just plain overpopulation. The solution to these issues has beenthe focus of international agencies and massive efforts from diversesectors of society, and continues to elude us all.
We may not have the luxury of time toresolve this and many other man-made environmental crises.
If the solution to the causes areignored by an uncooperative global society then why not take theissue on individually


Therefore the plan is simple, audaciouseven. We literally stop the desert from expanding.

The Plan


Sand, mostly Silicone Dioxide, is oneof the most placid substances on earth. It is simple and nonvolatile,and yet it has a tremendously destructive capacity. Dust stormsravage entire countries and can be easily seen from space. It is thismovement of sand that exacerbates the human-caused depletion ofvegetation, and therefore desertification. If sand weren't so fine,it wouldn't be able to wash over vulnerable landscapes. The planthen, is to alter the sand- to vitrify it into a more cogent mass,even gravel would suffice to reduce the enormous volume of sand thatis spreading.


Vitrification of desert sand happens innature. Lightning strikes produce fulgurite and meteor impactsproduce pieces like tektite. These natural occurrences require highamounts of energy to melt and fuse the sand, approximately1500°-2000°C.There is an abundance of available solar energy in most deserts, andin the Sahara particularly. It just needs to be harnessed.


In the late 1940's Felix Trombedeveloped a construct called the Solar Furnace. It uses mirrors toconcentrate solar energy to high temperatures. As a result of the1970's energy crises, large scale examples were built. The furnace atOdeillo in Southern France can reach temperatures of up to 3500°C.


More recently, as the 'green' movementreceived broader appeal through the early aughts, engineers developed similar technology, called concentrated solar powertowers. Like solar furnaces they are mechanical edifices thatconcentrate solar energy. These however, use the energy to produceelectricity.
Massive projects are alreadycommercially operational. This technology exists.

The Design


In order to vitrify desert sand, thosetwo technologies must be combined. Having large swathes of landcovered by heliostats prevents the energy from being focused on theground. Therefore the higher you build the smaller the footprint. Notonly would there be more desert exposure, but the height of the focusextends its range. Verticality is critical to the functionality ofthis design.


Commonly, solar furnaces have an arrayof heliostats that feed a parabolic mirror that focuses heat onto itsstatic target. Because this design seeks to have a roaming target,the system differs. A large-scale primary vertical mirror arraycollects the adequate amount of energy. This is focused onto asmaller mirror array (affixed to a separate tower) that configuresthe ray angles for a tertiary mirror which achieves the desiredtarget location. Similarly to ground-based heliostats, the verticalmirror arrays are mechanized for solar tracking.


The mirrors are sensitive to surfaceabrasion and their delicate machinery can be damaged by loose sand,especially during dust storms. For that reason they must be shieldedand yet still retain their flexibility. A multi-layer insulationsimilar to that used for satellites is the perfect material for thetask. As a building skin it has enough slack to deflect to wind loadsassociated with tall structures. It's insulation conditions againstdesert heat and can withstand extreme temperatures in case of adangerous malfunction.


In operation, this system would easilyproduce enough heat to continually vitrify and therefore coagulatesand, throughout the year. The roaming target of the arrays wouldform trails and patches of larger fused sand; and possibly eventuallystart to reshape the terrain.


That brings us back to a big question.Which desert is being halted?

The Desert


Because of its sandy composition andthe abundance of solar energy in the Sahara Desert, the design couldbe most easily implemented there. Some of the most extreme rates ofdesertification and most directly affected populations are in thisregion as well.
Picking a site may seem a challenge fora project like this, since a single development attempts to take onan area that is vast in comparison. Yet, one location is almostimmediately ideal from a glance at a satellite map.
There is a desert pass where trailingdunes can be seen pouring out into central Chad, fueling theencroachment of endangered Sahel ecosystems to the South.
The location is the pass between theTibesti Mountains and the Ennedi Plateau, where the Bodele jetstreamfires dune after dune from the Jef Jef El Kebir into the Erg ofDjourab. It is considered to be the Borkou region of Chad, and thechallenge of finding the names of these places speaks to the area'sremoteness.
Remoteness is a good thing whenbuilding a potentially dangerous construct. Not only are there lesspeople and property to endanger but it's vacancy signifies the lackof ecosystems that could be disrupted as well. There is no point insaving a jungle, so to speak, if an equally endangered species iseradicated.
This erg is a sea of dunes, completelydesolate and home to some of the fewest organisms on Earth. The onlybreak in the rolling sands are pinnacles of sandstone the quietlyerode day by day.


Between the blinding brilliance of thedaytime sand and the crooked heights of sandstone,
perhaps the form of this design mirrorsthe landscape not too dissimilarly to how it mirrors the Sun's rays.