Can you imagine being able to produce enough water in the Sahara to grow crops there? Can you imagine harnessing sufficient quantities of solar power to supply electricity to cities in Africa and cities in Europe? Can you imagine producing a sustainable bio-fuel that doesn’t impact on world food supplies? Charlie Paton, Michael Pawlyn and Bill Watts can and what’s more they can imagine all these happening in the same place at the same time.
This week this trio of visionaries launched the Sahara Forest Project: their proposal to combine two innovative technologies, Concentrated Solar Power (CSP) and Seawater Greenhouses, to produce renewable energy, water and food in an area of desert known to be one of the hottest places on earth.
Multitasking renewable solutions
It has often been said that there will be no one solution to solving the climate crisis and all those issues that surround it, such as energy sources, food prices and water supply. We need a portfolio of technologies to help us to combat these advancing problems. The Sahara Forest Project is one of the first projects we’ve seen that proposes not only to combine technologies to optimise performance and production, but also aims to tackle all of the serious challenges mentioned above. It is a bold and ambitious plan that, if realised, could have a powerful positive impact not only for the Sahara region, but also for Europe and the rest of the world.
The most exciting aspect of the Sahara Forest Project is not specifically the use of these technologies. We’ve read about Seawater Greenhouses and Concentrated Solar Power and how they’re being used to great effect. It is the fact that they are being used together in the same place, to support each other and optimize their operating capacities to produce energy and water and by proxy vegetation.
This sense of collaboration is echoed in the team of people behind the proposal: an inventor – Charlie Paton, creator of the Seawater Greenhouse; an architect – Michael Pawlyn of Exploration Architecture, previously of Grimshaw and the lead architect on the iconic Eden Project; an engineer – Bill Watts of Max Fordham & Partners, an engineering firm that focuses on energy efficient systems for the built environment. These three men have brought their considerable expertise together to create a truly innovative proposal.
Illustration of greenhouses having a similar effect on the climate as a region of forest, yet providing a net input of water vapour from the sea.
What does a Seawater Greenhouse do?
The Seawater Greenhouse was designed to address the problem of irrigating crops in arid coastal regions by evaporating seawater and condensing it into fresh water. This helps to reverse the trend of desertification created by normal industrial greenhouses, which can use up to five times more water to irrigate crops than the respective region’s average annual rainfall. The system works by mimicking the natural hydrological cycle where seawater heated by the sun, evaporates, cools down to form clouds and returns to the earth as rain, fog or dew.
What does Concentrated Solar Power do?
CSP is currently seen as one of the most exciting and powerful ways of harnessing the sun’s energy to create power. Like the Seawater Greenhouse, CSP works well in hot arid areas where the sun is at its most powerful. The sun’s rays, collected through reflecting mirrors, are used to heat water which then produces steam to power turbines. Examples currently working are Nevada Solar 1 near Las Vegas, and the solar tower in Barstow California. It has been proposed that the energy created by CSP in the Sahara could be transported to Europe with minimal loss via high voltage DC power lines.
Sketch showing long ‘hedge’ of Seawater Greenhouses oriented towards the wind. Photo of Solar Power Tower in Barstow, California
How will the Sahara Forest Project work?
These CSP / Seawater Greenhouse technologies will work together at a location some distance from the north coast of Africa, hopefully at a point below sea level which will reduce or potentially eliminate the costs of pumping seawater. The scheme has been designed as a ‘hedge’ of greenhouses providing a windbreak and shelter for the outdoor planting. CSP arrays will be placed at intervals along the greenhouse ‘hedge’. The greenhouses produce five time more fresh water than needed for the plants inside. This surplus will be used to irrigate the planted orchards and the Jatrophra crop, which can be turned into bio-fuel for transportation and other needs.
The Sahara Forest Project team tell us that the innovative interaction between the two technologies helps each to function more efficiently:
1.CSP systems need water for cleaning the mirrors and for the generation of steam to drive the turbines which the greenhouses can provide.
2.The Greenhouse evaporators make very efficient dust traps (as do plants that are growing outside) which benefits the CSP since the mirrors stay cleaner and therefore operate more efficiently.
3. In solar thermal power plants, only about 25% of the collected solar energy is converted into electricity. If combined with sea water another 50% of the collected energy, normally released as heat, can be used for desalination. This way, up to 85% of the collected solar energy can be used.
In conclusion the Sahara Forest Project works on many levels. By combining the benefits of Concentrated Solar Power and Seawater Greenhouses the design team has vastly scaled up the positive outputs of renewable energy, food production and fresh water supply. Furthermore they tell us that “the scheme would also have the restorative effect of returning areas of desert to forested land and sequestering substantial quantities of atmospheric carbon in new plant growth and reactivated soils.” Surely this is a perfect example of the potential power of human and technological collaboration.