In February 2000, several chimney-like structures appeared in a walnut grove in Northern California. The owner of the 250-acre Shur Farms, Steve Hammersmith, had been told that by installing these devices he could protect his crop from late frosts. During the following spring, though he counted around six episodes of frost, the walnuts remained unharmed. It was the first time the crop had emerged unscathed in 18 years. So impressed was Hammersmith that he now represents the Uruguayan company that makes the chimneys, Frost Protection Corporation (FPC), in California.
Threat to Harvests
The brains and driving force behind the anti-frost chimneys is Rafael Guarga, a hydraulics engineer and rector of the State University of Uruguay. More than 10 years ago, having witnessed the devastation caused to citrus fruit crops in his own country by radiation frost, he developed the technology for what is today called the Selected Inverted Sink system (SIS) and later patented the device.
Radiation frost results from the radiation of heat from the earth’s surface during the night, when the air temperature at ground level drops beneath that a few metres higher. It can seriously damage crops, particularly during spring when plants are budding, and is a major cause of loss of income for fruit and vegetable growers. SIS consists of a sort of chimney two or three metres tall and usually built of canvas or steel sheets, with vents in its base. A motorised fan inside sucks up the cold, potentially frost-forming air lying near the ground and expels it hundreds of metres higher up, dispersing it with warmer air far above the treetops.
To date, Professor Guarga has developed two models — one powered by a 50-horsepower motor and a smaller, 15-horsepower version. Though the chimney and motor can be manufactured locally, the fan’s propeller continues to be constructed under his supervision in Uruguay. He has spent the last two years refining its design to improve the system’s overall efficiency — with dramatic results. The larger model now costs around US$12,000 in Uruguay, about a 50 per cent reduction since 1998.
Professor Guarga’s innovative device is cheaper to run than almost all other methods of frost protection. Hammersmith compares its operating costs with those of heaters, a popular alternative to the SIS. "It costs approximately US$30 per acre per hour to run a heater, compared to 15 cents per acre per hour for SIS," he calculates. Significantly, the fact that SIS can also be operated manually or by a tractor engine makes it especially accessible to farmers in developing countries. Another important selling point to growers everywhere, the cold-extracting chimney is, unlike other frost-reduction methods, environmentally friendly.
Seal of Approval
The efficacy of the award-winning SIS has already been independently verified by Uruguay’s National Institute of Agricultural Technology. Not satisfied with this, however, Professor Guarga has sought second opinions from the University of California, Davis and the Centre d’expérimentation fruits et légumes near Toulouse in France, which are currently carrying out assessments. Armed with the approval of these respected institutions, he hopes to market the system even more widely. In particular, he has his eye on the vineyards of California and Spain, where he believes SIS could revolutionise wine growing.
Professor Guarga attributes much of the invention’s success to the publicity he received from winning a Rolex Award in 1998. "The main impact is the acceptance of the system and its wider distribution," he reports. "Already, besides California and Uruguay, it is in operation in Argentina, Chile and France."
Keeping it Simple
In the past, adds Hammersmith, frost protection has been a hit-and-miss affair. SIS succeeds where other methods have failed because Professor Guarga has taken a scientific approach to the problem, and yet there is nothing complicated about it. Once people understand the process, they say, "Wow, it’s so simple it must work."
Published in 2001