By using available and abundant resources, one can make sensitive ecosystems greener and more productive. Innovative methods and solutions can turn profits in the world’s most deprived areas.
Extreme deserts cover over a third of the Earth’s land area. They are harsh and unpredictable environments, where the lack and uneven availability of water makes it difficult or impossible to farm. They are also sensitive – careless logging and depletion of soils in dry areas is associated with a constant risk of soil erosion and further desertification. Yet, these areas are home to more than 10 percent of the world’s population, many of who are among the poorest. But deserts are also rich in two unique resources: sun and space.
Thermal solar power
A technique that takes advantage of this is thermal solar (Concentrated Solar Power, CSP), which means that sunlight is concentrated and runs a heat engine. The low cloud formation in combination with the amount of unused land makes an attractive location for such installations.
Thus far, the predominant focus has been to use light to heat water pipes, and store the energy. Water is then evaporated through a heat exchanger, before the energy is finally converted into electricity via a steam turbine.
Another form of thermal solar power is a wide field covered with rotating, computer-controlled mirrors, called heliostats, which continuously track the sun’s movement, and direct the heat to a solar tower. The sunlight is concentrated in this way from the field’s entire surface to a single point.
Oil has previously been used as a heating media, but the hope in the future is to yield even higher temperatures with molten salts or liquid sodium.
An alternative and efficient way to use the heat is to directly power Stirling engines. There are two Swedish companies at the forefront of these applications, such as Cleanergy and Ripasso Energy, which developed the Kockums Stirling engines and adapted them for solar power applications.
Water is key
If the desert is recaptured, it must bloom. Desert planting is not a new idea, but a limiting factor is the availability of water. Water is not scarce in an absolute sense – however, there is a local shortage of clean drinking water, especially where it’s needed most. So-called seawater greenhouses are intended to be placed in dry areas.
The concept is to pass seawater through an evaporator. It then passes the greenhouse roof where it is heated by the sun that acts as a second evaporator. It is then condensed into fresh water by cooled incoming seawater. The fresh water is used for irrigation.
Synergies provides hope for the future
Perhaps the most interesting of synergies, from a future perspective, is what can be attained by allowing multiple technologies to work together for robust solutions.
One promising example is the Sahara Forest Project, a project that is looking for opportunities to combine the right solar thermal and seawater greenhouses.
The thermal solar power plant pumps water to the greenhouse, and in return clean water is made for cleaning and cooling. Waste heat from the process can also contribute to desalting. There are plans to surround the greenhouses with hardy outdoor cultivation to take advantage of the humid microclimate created. The incoming salt water can also be fed in via cultivation ponds, where microalgae and their residues can provide biomass as a fertilizer.
The Norway-based Bellona Foundation is supporting the project. Pilot plants have been set up in Jordan and Qatar, in collaboration with Norwegian and Jordanian authorities, and fertilizer companies Yara and Qafco.
DESERTEC is another visionary project that is seeking ways to produce renewable energy in desert areas. The idea is to provide solar power from the Sahara for example to Europe via high voltage power cables laid under the Mediterranean.
Providing the world’s growing population with food, clean water and renewable energy is perhaps the biggest challenge the world faces. When renewable energy is used to desalinate water and vegetate the desert, critical problems such as water scarcity, dependence on fossil fuels and food security, can maybe be solved. There are many problems to solve along the way, but the future of the desert looks brighter.
The article was published in April 2013