The Sahara Forest Project (SFP) pilot facility in Qatar has ‘exceeded expectations,’ proving that seawater-cooled greenhouses can be highly productive in desert conditions.
Using greenhouses to grow crops in the desert has previously incurred huge costs in terms of energy and water consumption, as well as capital and operating investment.
An international collaboration between a number of designers and technologists, with engineering provided by UK firm Max Fordham, has now created a facility which instead grows food using sustainable levels of energy and water by making use of solar power and sea brine.
The seawater-cooled greenhouse has proven to be highly productive, enabling year-round cultivation of high-value vegetable crops even in desert conditions. By using sea water to provide evaporative cooling and humidification, the crops’ water requirements and carbon footprint are minimized while yields are maximized.
The seawater cooling system supports production of high-quality vegetables throughout the Qatari summer, and reduces freshwater usage to less than half that of comparable greenhouses in the region.
The yields are competitive with those in commercial operations in Europe. Current yields indicate three crops a year will produce at least 75 kilograms per square metre and that significantly higher yields can be achieved in a commercial set-up.
CSP is used for electricity and heat generation. Through the positioning of mirrors, the sun’s energy is concentrated to produce heat which generates the steam to drive a turbine. This in turn enables a generator to produce electricity.
A collection of technologies and practices for establishing external vegetation in arid environments, such as evaporative hedges, are also being implemented. The hedges provide evaporative cooling and humidification to areas downwind of their position.
These humidified spaces will provide an area for outdoor vegetation, letting plants take advantage of the cooler, more humid, and wind-sheltered environment provided by the hedges, thus making it possible to grow a wider range of crops than would normally prevail in open conditions.
The successful integration of the solar and desalination technologies indicates that this confluence of technologies will work at larger scale. Synergies between the greenhouse and evaporative hedges also provide wet-cooling efficiencies without the need for cooling towers.
The external evaporative hedges were found to provide cooling of up to 10 degrees for agricultural crops and desert re-vegetation. Vegetable and grain crops even grow outdoors throughout the year and useful desert plants rapidly flourished when cultivated with small quantities of water and nutrients.
The saltwater infrastructure also makes possible many concept extensions. Salt was produced as the end result of the saltwater value chain in large evaporative ponds. Algae with the potential for commercial cultivation displayed strong tolerance to heat and high evaporation rates.
Halophytes useful as fodder or bioenergy grew successfully on pure seawater throughout the summer, and innovative saltwater irrigation systems operated without clogging or corrosion.
“Good greenhouse performance and yields year-round, thriving outdoor crops and characterizations of the integrated Sahara Forest Project system confirm the robustness and suitability of the design for large-scale commercial operation in desert environments," said Joakim Hauge, CEO of The Sahara Forest Project. "This creates commercial opportunities for the near-term production of competitive products and enhanced profitability with future economies of scale."
The pilot operations have verified the viability of profitable large scale greenhouse production in Qatar. Just eight hectares of greenhouse production SFP would match the yearly import of cucumbers while 60 hectares would equal the yearly import of cucumbers, tomatoes, peppers, and aubergines to Qatar.