Uruguayan engineer reaps the fruits of success

Published 2008

Overnight frost can destroy, in a few hours, a crop of fruit grown in orchards over a period of months. Such losses are devastating for those growing fruit trees on a large scale. But a machine invented and manufactured by 1998 Associate Laureate Rafael Guarga, of Uruguay, is providing a solution in orchards on several continents.

Orchardists around the world spend millions of dollars to protect crops from unusually severe or erratically late frosts. In general, the time-honoured way to protect an orchard has involved heaters, irrigation or horizontal axle fans mounted on towers, or combinations of these methods. Another method is the mobile option whereby tractors pull combined heat-and-wind machines around orchards on chilly nights.

None of these methods is cheap to run, and the noise of high-power fans running through the night with or without the tractor is an increasing cause of disputes between orchardists and their residential neighbours. As a result of this, in one part of New Zealand, for example, orchardists and grape-growers wanting to install frost protection are now faced with highly onerous approval conditions, imposed by the local government.

When successive nights of severe frosts hit southern and central California in January 2007, local orchardists thought they were prepared to prevent disaster. Citrus fruits, avocados and strawberries worth hundreds of millions of dollars were at risk, but about 14,000 wind machines were poised to protect them. However, the supplies of propane needed to run 12,000 of these machines ran low or, in many areas, ran out, even with delivery drivers receiving emergency exemptions to safety limits on the hours they could spend on the road.

Governor Arnold Schwarzenegger conferred disaster area status on 10 counties, and the losses to the citrus industry alone were estimated at around US$1 billion.

The disaster focused attention on the quiet, low-energy alternative in frost control – expelling upwards the still, cold air where frost forms, using a large, slow-moving fan mounted inside what looks like a squat vertical chimney. The Selective Inverted Sink (SIS) system, as it is known, is the brainchild of Uruguayan hydro-mechanical engineer Rafael Guarga, who had made his name initially blowing air bubbles into the misbehaving turbines of a Mexican hydroelectric power station.

Dr Guarga, as much a scientist as an engineer, likes to keep one foot in the laboratory and one in the field. “The interaction between theory and careful experimentation has always strongly attracted me,” he said. “I also like to work on the problem in front of me.”

In Mexico, where he was studying for his doctorate, the problem was that the hydroelectric turbines ran roughly under certain flow conditions, shortening their effective life and limiting electricity production. Guarga identified the theoretical deficiency behind the design fault and helped suggest the solution – to blow pressurized air into the water stream entering the turbines. A grateful Mexico conferred a major science and technology award on him in 1982.

On his return to Uruguay, Dr Guarga found a different problem to focus on, the significant economic issue of fruit losses from late frosts. Many a still night taking temperatures in the orchards followed, while Dr Guarga and his small team developed an understanding of how cold air layers formed, how they flowed over the topography and where they settled. In the early 1990s, this combination of theory and practice informed the development of the SIS, which selectively removes the settled cold layer of air, allowing layers of warmer air to take its place.

Dr Guarga, the Rector of Uruguay University from 1998 to 2006, set up the Frost Protection Corporation (FPC) to perfect and market this most environmentally benign of frost-control systems. “At present, FPC is an enterprise valued at about US$1.3 million, 12 people are working in it, and it conducts frost risk studies in orchards and achieves frost control by applying the SIS technology,” he says. “Since it started operations as an enterprise, the equivalent of 1,225 average-size SIS installations have been sold, and all of them are still operating.”

California Central Valley orchardist Mike Jackson says that when he came across the “Have frost problems?” sign at an agricultural show in 2002, “I went running because I have $10 million in fruit to protect.” Like many growers in the area, he uses every form of frost protection available, from wind machines on tall towers to propane-powered tractor arrays, but he praises his SIS installations – “three of the largest models” – for their capacity to drain the cold air from hollows. “They are good for a degree-and-a-half to two degrees difference,” he explains. “It is quite impressive, they can drag air from half a mile away. We’ve been very happy with them – they are cheap to run and they don’t need a lot of attention.”

Asked how he did in January’s big freeze, Jackson just laughs. “We have stone fruit, so in January the colder the better for us. I worry about frosts in March and April.” But the surrounding citrus growers “were hurt pretty bad”.

Not surprisingly, a California SIS distributor reports a modest boom in inquiries. “We’ve mainly supplied SIS installations for vines and stone fruits,” says Susie Hammersmith. “We are now getting a lot of inquiries from citrus and avocado growers.”

Frost protection, of any sort, can only do so much, however. Derek Keopl, manager of an orange orchard – equipped with an SIS – in Orange County, California, reports in a surprisingly upbeat way that “everything froze” in January. “It was just so cold,” he declares. But his SIS installations do well during more routine frosts without causing audible or visual disturbance to the local business model combining fruit growing and cattle-ranching with upmarket property development.

Hammersmith agrees that sometimes it was not possible to save the fruit, but says that for many growers “tree protection is even more important”.

Guarga explains that, based in “a small country such as Uruguay with no known technological tradition”, commercialising any invention can be challenging.

"The Rolex Award was very important in the successful development of the SIS System as it helped spread the news about the invention and the reliability of its technology,” he says. “SIS is a radical innovation compared with preexisting technologies in frost control, and the Rolex Award helped build a trustworthy image of this technology.”

“I believe that the world success of the SIS System has been important to Uruguay, which has traditionally exported unmanufactured goods like meat, wool and rice, with little incorporation of national added value.

“A change has started as Uruguay has turned into the leading exporter of software in the region, and the SIS experience shows it could go far beyond this if young, Uruguayan scientists and well trained engineers dedicate themselves to the development of incremental and radical innovations in agro-industrial applications.”

SIS installations have been established in Argentina, Chile, the United States, New Zealand, Australia, Spain and South Africa. And Uruguay, of course, where a trial was launched in November to keep an air force base free of fog. The experiment is part of Dr Guarga’s quest to find new applications for the technology in dealing with other problems of still, cold air. As well as fog control for airports and highways, he sees potential applications with temperature control in greenhouses and the dispersion of odours and pollution that settle on some small towns and communities.

“If it is related to the stratification of the air, it will often be the case that the problem is contained in the coldest layer lowest to the ground,” Guarga explains. “If the fog or the smell or the pollution dissipates when the sun comes up or it is windy, it is a sign that it may be possible to use a technology like SIS to displace the layer of air that is the medium for the problem.”

Phil Dickie

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