Fresh water is scarce worldwide and growing scarcer. This adds even more importance to the achievement of Sundrop Farms, working in South Australia, to accomplish an impressive agricultural feat: using solar desalinization to produce vegetables in the desert.
A 75m line of motorised parabolic mirrors that follow the sun all day focuses its heat on a pipe containing a sealed-in supply of oil. The hot oil in turn heats nearby tanks of seawater pumped up from a few metres below ground – the shore is only 100m away. The oil brings the seawater up to 160C and steam from this drives turbines providing electricity. Some of the hot water from the process heats the greenhouse through the cold desert nights, while the rest is fed into a desalination plant that produces the 10,000 litres of fresh water a day needed to keep the plants happy. The water the grower gets is pure and ready for the perfect mix of nutrients to be added. The air in the greenhouse is kept humid and cool by trickling water over a wall of honeycombed cardboard evaporative pads through which air is driven by wind and fans. The system is hi-tech all the way; the greenhouse is in a remote spot, but the grower, a hyper-enthusiastic 27-year-old Canadian, Dave Pratt, can rather delightfully control all the growing conditions for his tonnes of crops from an iPhone app if he's out on the town – or even home in Ontario.The project is not without controversy. The originator of the process, Charlie Paton, objected to some of the techniques being used by Sundrop and received an undisclosed ex-gratia settlement for cutting ties last February.
The article captures Charlie Paton's parting words:
"We will absolutely keep on at this in our own way," he says, "but I don't really feel that proprietary about it. The heart of the technology is actually a bit of soggy cardboard. You can't patent or protect the idea of evaporative cooling. The idea of using seawater to do that absolutely was a major breakthrough, but again, you can't patent it. The main thing is that it's us that's still picking up the plaudits, and I think that makes Philipp really angry."In this case, the purely commercial ethic and altruistic ideals operate on entirely different levels. Only by bringing these two viewpoints into closer alignment can the true benefits of this achievement be realized on a global basis.