When the mercury drops, farmers may soon have a new tool to protect their valuable crops.
Adapting technology originally developed to detect and identify aircraft, the tech company Raytheon has developed a device that delivers radar waves to stop crops from freezing.
"This is essentially a radar that doesn't detect anything," said Larry Farrier, a project manager who helped develop the Tempwave crop warming system. "Tempwave delivers energy to the crops, which is absorbed, and freezing is prevented."
Currently farmers have several options to protect crops like apples, oranges and other fruit. Large fans can mix warm air across the crops. Sprinkler systems can surround fruit with a protective layer of ice. As a last resort farmers can start bonfires and then circulate the hot air past freezing crops to prevent individual cells in the fruit from freezing and bursting.
To test the Tempwave's effectiveness at warming crops, Raytheon, working with a large citrus grower, Paramount Citrus, recently tested the Tempwave system on a quarter acre plot of naval oranges near Visalia, Calif.
During the course of several nights the temperature in the orange grove dropped to 28 degrees Fahrenheit. Raytheon's team placed one Tempwave antenna, about 30 feet tall and bulb-shaped, on each corner of the four acre plot and let them run through the night.
Without any system to warm the fruit, the oranges would have frozen and become unsellable. The naval oranges made it thought the night unscathed.
Each of the four antennae emit low powered radar waves tuned specifically to water molecules. Much like a microwave, the radar waves cause water molecules to vibrate and heat up just enough to keep them from freezing. The radio waves are relatively low energy are completely safe for humans to work around, says Farrier.
"We aren't trying to keep the fruit at room temperature here," said Farrier. "We are just trying to shine enough energy on them so they don't freeze."
This winter's test was small scale. In a full-scale system one antenna would provide enough energy to heat one acre, instead of four antenna for one-fourth an acre.
Farrier says that while the Tempwave system provides just enough energy to stop it from freezing, it's completely safe for humans to work around.
"I was in the field during the experiment and it was a cold morning," said Farrier. "I was hoping I would be warmed up and I wasn't."
Raytheon hasn't announced a firm price yet, although Farrier says that Tempwave will be competitive with other crop protection systems, somewhere between $2,000 and $3,000 an antenna.
The price is essential, says Paramount Citrus president David Krause, who while involved with the trials hasn't decided if he will purchase the system yet.
"The technology provides us with a novel way to protect crops in a more environmentally and cost effective manner," said Krause. "The alternative is to use electricity to pump water, burning fuel to drive propellers, or to just burn fuel to raise the temperature, which can damage crops and is costly."
Tempwave might reduce the fuel cost of orchards another, more indirect way as well. Last year Raytheon developed a similar heating system using radio waves that would heat oil locked inside shale, making it easier to retrieve. Raytheon sold the oil heating system to Schlumberger, an oil field services company.
Among other civilian applications, Raytheon engineers are also investigating whether radio wave heating could be used to incubate chicken embryos inexpensively, instead of using traditional heat lamps.
"We are trying to look at world problems, and see if we can adapt core Raytheon technology to develops solutions that can address those problems," said Farrier