New networks take nature’s pulse

Outdoor advances such as low-power chips and tiny solar panels let computers get a breath of fresh air.

Courtesy of Mark Holler/Camalie Vineyards
Nature tech: Camalie Vineyards owner Mark Holler (left), a former Intel technologist, plays with a device that measures leaf-water potential, as manager Ramon Pulido looks on. The yellow node mounted atop a highway stake (top left corner) wirelessly transmits data to the vineyard headquarters.
Courtesy of Mark Holler/Camalie Vineyards
Wireless: A sensor network node at Camalie Vineyards helps measure ground moisture.

The hand-sized yellow objects poking up among the lush canopies at Camalie Vineyards aren’t a new variety of monster grape. They’re electronic devices that can sense soil moisture.

Viticulturist Mark Holler says these wireless sensors sprinkled throughout the leaves help him manage the high cost of irrigation and improve his yield.

“Wireless sensor networks extend the Internet ... out into the environment,” says Mr. Holler, a retired Intel technologist who owns and runs the 4.4-acre vineyard in Napa, Calif.

While the networks won’t necessarily make someone a better vintner, they do have a practical side: During the 2007 drought in California, Holler figures the technology saved him several thousand dollars in water costs.

Electronics weren’t originally outdoor friendly. Rain and dust wreak havoc on computer circuits. Cables and power problems snarled early attempts at open-air networks. But as Wi-Fi and solar panels grew more popular, inventors started looking outside. Now, power-sipping wireless sensor networks are cropping up in more and more outdoor venues.

In Antarctica and California’s Sierra Nevada mountain range, they measure snowpack. On volcanoes in Ecuador, they sense tremors. In Australia, they track invasive cane toads. And in Cambridge, Mass., they sit atop buildings and street lights to monitor weather changes and air pollution.

“The potential is unfathomable,” says Kirsten West, principal analyst at West Technology Research Solutions in Mountain View, Calif. With no wires to hold back innovation, “you don’t have to worry about the physical network.”

Already a $120 million market, networked outdoor sensors will benefit from a boom in low-power microchips. Ms. West estimates that demand for the latest chips will grow 34-fold to $680,000 by 2013.

“The market is still relatively small, but the pieces are all there,” says David Culler, a wireless sensor network pioneer and computer science professor at the University of California at Berkeley.

The networks that originated in university labs like his are now reliable enough that they have moved into mainstream uses in homes, buildings, factories, and the environment. The industry still needs established standards to assure that networks can talk to each other and longer battery life to keep them running.

The improvements to outdoor technology have been readily evident at Camalie Vineyards. Only a few years ago, Holler was wrapping each device’s circuit board in aluminum foil to protect them from rain, dust, and ultraviolet rays. The makeshift electronics looked better at scaring off crows than sending data. Now, he buys the circuitry snugly sealed inside yellow plastic cases, each topped with a small solar panel that can recharge the batteries.

With limits to battery power, it’s also important to conserve energy use in the wireless network.

“The sensors are automatically power-managed by our device,” says Mike Horton, president of Crossbow Technology of San Jose, Calif., which makes the solar-powered eKo sensors that Holler uses.

Soil, temperature, and other conditions can vary across the vineyard, so Holler has set up 32 network stations or nodes. Each has the eKo circuit board mounted atop a six-foot post and wired to three sensors buried in the soil at depths of one, two, and three feet.

The sensors measure soil moisture every 10 minutes and relay that information to the eKo device, which, in turn, transmits the information via wireless radio signals to and from other nodes in the vineyard. The information travels from the wireless sensor network in the vineyard to an Internet gateway and then to Holler’s office computer.

“The technology works, is robust, and puts data on the Internet quickly,” says Holler.

The sensor network has a self-organizing feature, meaning each network node talks to the nearest node with the strongest signal. If one node fails, the next strongest signal is picked up so the network keeps working. He says the information from the sensor network has let him use less water, stress the vines less, irrigate properly, and get better quality grapes.

To date, sensor networks are being used with high-value crops like fruits, nuts, and nursery plants. A recent survey of 36 vintners and farmers in the US found that more than half already use wireless sensors and about a third plan to get new applications over the next 18 months, according to ON World, a wireless research company in San Diego. Uses include monitoring soil temperature and moisture, sensing how fertilizers dissipate, and detecting pests or mold.

Because sensor networks are wireless, they are being put in far-flung places, including on volcanoes. Matt Welsh, associate professor of computer science at Harvard University’s Sensor Networks Laboratory in Cambridge, Mass., has put test networks on several volcanoes in Ecuador to detect seismic and acoustic signals so scientists can better understand how volcanoes work.

One of the challenges was the tough physical landscape. The volcanoes regularly shook or spewed rock – at one time shearing off an equipment antenna. The sensor network was able to collect mounds of data that told researchers what the volcano was doing.

“The things we are doing with volcanoes could apply to collecting high-resolution signals such as on a bridge or during an earthquake,” says Mr. Welsh. “There are potential commercial applications in oil and gas field exploration.”

He sees much broader uses for wireless sensor networks. “The technology is on the brink of getting widespread adoption,” he says.

In a few years, sensor networks could be in the same place the Internet is now, Welsh says.

“Sensor networks could be enmeshed in the fabric of the world to do monitoring in all kinds of places where you can’t do it now.”

New sensors tap power from trees
The thought of trekking across Antarctica or through an expansive vineyard to change a wireless sensor’s batteries isn’t too appealing. To avoid such trips, researchers are looking to harness the energy of everything from building vibrations to tree chemistry to keep their devices running as long a possible.

“There is an emerging trend toward power harvesting,” says Sam Lucero, an analyst at ABI Research in Scottsdale, Ariz.

The Massachusetts Institute of Technology in Cambridge, Mass., has tapped trees to power sensors that could predict and track forest fires and potentially detect threats such as radioactive materials at US borders.

Each sensor has a battery that can be slowly recharged using the small amount of electricity generated by a chemical imbalance between the tree and the soil in which it grows.

The wireless sensor network is being developed by Voltree Power of Canton, Mass., and is to be tested this spring on a 10-acre lot provided by the US Forest Service.

Germany’s EnOcean makes wireless sensors without batteries. The sensors are powered by their surroundings such as energy from vibrations, rotations, pressure, light, and temperature changes. For example, vibrations can be converted into electrical energy by flexing crystals that have a property known as piezoelectricity.

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