Saturday, 6 December 2014

Can Solar Thermal Desalination Make Sustainable Agriculture Possible?

The jury is still out on solar thermal, which is certainly efficient but has its critics because of its costs, both financial and ecological. The International Energy Association (IEA) is still bullish about its future, and projects such as the Solana Generating Station in Arizona show potential. Large projects such as Masdar’s Shams 1 and California’s Ivanpah have scored plenty of attention, but the rapidly decreasing price of solar panels has made PV more attractive for large projects. But solar thermal technology could have promise for agriculture. At a time when many are pondering how we are going to feed nine billion people by 2050, new projects underway are leveraging solar thermal desalination technology to cleanse water and grow crops in water-stressed regions.
Sundrop Farms, based in Port Augusta, Australia, believes it has a solution. The company claims it is the only such company in the world that can build and operate greenhouses in areas that severely lack fresh water, arable land, or access to the electrical grid. In order to bring food closer to cities, “Sundrop Systems” turn energy from the sun and seawater into freshwater for irrigation, power for greenhouses and climate control to heat and cool crops as needed. Nutrients that end up as by-products from the desalination process can also be converted into fertilizer that in turn can be used within the greenhouse. In a way, one could describe this as a closed-loop system for growing food. The ability to grow food in places like brownfield sites or in areas where the climate is too harsh for agriculture, or even horticulture, could make this a more sustainable way to produce food—if it can become cost competitive. Sundrop Farms and its main investor, the American private equity firm KKR, have not publicly revealed any figures about the cost of these projects or whether they seek financial incentives from local governments.
Nevertheless, as more countries and municipalities consider desalination to meet their ever-growing water needs, alternatives to current desalination technologies are needed. Desalination using conventional fossil fuels leaves its own sizable carbon footprint, and the process is also expensive and leaves municipalities and businesses vulnerable to volatile prices. Solar desalination shows some promise, but is still several years off from becoming truly scalable. But Sundrop Farms’ application for farms could have potential.
Port Augusta, located in an arid region in South Australia, could become the perfect laboratory exploring solar thermal’s viability for agriculture. The town receives only about 10 inches of water (25 cm) of water annually—much of Australia has suffered even more as the country has coped with severe droughts for several years. Sundrop Farms and KKR are investing in a 20 hectare (49 acres) facility that will produce 15 million kilograms (33 million pounds) of vegetables and other tomatoes—which both companies say will produce 100 more times food than the current greenhouse onsite. According to a Factiva search, 11,000 parabolic mirrors will redirect sunlight on a 115 meter (327 feet) tall tower, which in turn will create steam that will power turbines and then provide energy for the mega-greenhouse. The project also promises 200 jobs, a solid economic boost in this town of 13,000 people.
If the project succeeds, Sundrop Farms has its crosshairs on new markets in the United States and Middle East. With the growing mantra to “buy local” catching on in the U.S.—often in communities where large-scale agriculture is not possible—do not be surprised if this is a technology we see in more cities in a decade. And as California and other states cope with an extended drought, seawater will take a more active role in irrigation with freshwater and groundwater supplies close to being tapped out.
A similar solar thermal project launched earlier this year in another water-stressed region.WaterFX, a California start-up, has built a solar thermal-powered desalination plant in the San Joaquin Valley that cleans saline drainage water and turns into freshwater for irrigation. The 6,500 square foot facility can produce eight gallons of safe and clean water a minute, and plans are underway to expand the plant so it can produce 2,200 acre-feet of water annually. Pilot programs are also on the drawing board in Chile, which is also has a large agricultural sector and has its own water challenges.
With 70 to 80 percent of the world’s freshwater devoted to farming, society will have to make some tough choices in the coming decades as we use water faster than it can be replenished. Technologies coming from companies such as Sundrop Farms at the very least will motivate other clean technology entrepreneurs to find new ways to harvest water and grow crops for an ever more crowded world—sustainably.

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