REALITY: Modern wireless technologies
Owners of cell phones, television remote controls, smart car keys and devices with phone, e-mail and web access have in the past generally been willing to trade their wireless devices' moderate degree of unreliability in exchange for an enormous payback in convenience. In contrast, industrial firms and government departments have long shown resistance to replacing wired sensors and controls with wireless communication networks because of a widespread perception—some say a myth—that wireless technologies are fundamentally unreliable.
Few are more familiar with this myth than Wayne Manges, an electrical engineer at Oak Ridge National Laboratory. In 1996 he began writing about advances in wireless sensor technology in articles published in Sensors, Wireless and other trade magazines. In the same year he co-chaired a workshop at ORNL on the potential of industrial wireless technology.
In 1998 the National Academy of Sciences published a report based on the workshop talks. The report concludes that wireless sensors and controls present an opportunity to save energy, reduce emissions and enable more efficient use of raw materials. The compatibility of these potential benefits with the Department of Energy's industrial technology missions led DOE to develop a strategy designed to convince U.S. industries with large energy consumption to adopt wireless technology.
In 2007 three U.S. companies—Honeywell, Eaton and General Electric—along with three foreign companies began marketing wireless sensor-and-control technologies to industrial customers such as those that produce therapeutic drugs and petrochemicals. In 2008 the number of companies that are fabricators and purchasers of wireless sensors has sharply increased. These accelerating shifts in supply and demand are evidence of a growing confidence that wireless technology is perceived to be reliable.
Manges in some respects serves as a visionary, missionary, adviser, storyteller and reality check for wireless technology. With regard to reliability, he likes to tell the story of Steven Chen, president of 3ETI, who considered the U.S. Navy a promising market for wireless technology because cables on ships are heavy and costly. Chen called Manges and requested a demonstration on a Navy ship of ORNL's single-chip wireless sensor, a technology designed and fabricated using internal funding from ORNL's Laboratory Directed Research and Development program.
Manges and colleague Michael Moore drove to Jacksonville, Florida, and boarded the USS The Sullivans, a guided missile destroyer. The two researchers conducted a demonstration designed to show naval officers that a wireless chip can work reliably on a ship.
When several officers learned the purpose of the test, Manges heard them say, "This is a metal ship, and radio cannot work on a metal ship." The ORNL researchers smiled pleasantly and entered the engine room to conduct the first test.
"Our sensor chip was able to measure the temperature in the engine room and transmit the data reliably up to the third deck," Manges says. "A wireless signal sneaked up a catwalk connecting the decks to a computer on the top deck."
When Manges and Moore took the sensor chip to the ship's computer room, the commanding officer expressed doubt that the sensor could transmit a temperature signal because of the metal in the large computers and electromagnetic interference. "We were able to make and send sensor measurements of temperatures behind computer cabinets and elsewhere in the room because the signal bounces around the room and finds its way out," Manges explains.
"We tried one more test of the wireless sensor inside a metal room with a metal door. Mike Moore left the room and took the sensor down the hall. We were able to read the hall temperature on a computer inside the metal room 20 feet away."
While it is true that radio signals cannot penetrate metal doors, it is also true that radio waves can sail through rubber gaskets used on ship doors to keep out water. "Our sensor radio uses spread spectrum signals that find their way out through door gaskets," Manges says, noting that spread spectrum technology was invented partly by Hedy Lamarr, the movie actress.
The commanding officer explains to Manges that using wireless sensors and controls to automate room temperature measurements and control the ship's temperature so it never exceeds 80°F would allow him to reassign the sailor charged with gathering and recording these measurements.
As a result of the successful ORNL demo, Navy officers looked for a supplier of wireless sensor and control networks. Their search led them to Steven Chen's company, 3ETI.
The lingering reliability myth of wireless technology includes the belief that a turned-on cell phone can shut down a wirelessly automated factory. Such an event is possible only if installers of a wireless network do not follow explicit standards. Manges chairs the committee that is developing the international standard for wireless automation.
Wireless technology is also plagued by the misconception that wireless sensors and controls cost more than conventional wired devices. Asia's construction boom has contributed to a quadrupling of the cost of copper wire. Likewise, the labor cost for installing wire has risen sharply. These costs, however, are only part of the story.
A Honeywell researcher recently told Manges about a customer whose company purchased a wireless tank level sensor for its ethanol refinery and experienced a return on investment in only 24 hours.
"This ethanol plant was having trouble with its wired tank level sensor because ethanol can corrode metallic electrical contacts," Manges says. "Honeywell installed a wireless tank level sensor and, by the end of the first day, when the wired one failed to halt the flow of ethanol into the tank, the wireless sensor sent a "stop" radio signal to the operator, preventing a costly ethanol spill."
Mounting evidence suggests that wireless technologies can help industry save energy and conserve materials. For years Manges has been extolling the potential of wireless sensor-and-control networks for helping industry and government agencies save energy and money while conserving materials and reducing health-threatening and climate-altering emissions to the environment.
"The simplest and cheapest way to save energy in most industrial plants with electric motors is to outfit each motor with a suite of inexpensive temperature, acoustic, magnetic and vibration sensors," says Manges. "These sensors will tell plant operators when a motor is overheating or vibrating too much or is otherwise near failure."
Most companies do not install wired instruments on their motors. For decades they have simply replaced their motors every two years under the assumption that they will soon wear out. This costly practice can lower productivity and waste useful materials in motors that might have lasted much longer.
"When electric motors waste energy, they give off heat," Manges says. "A wireless heat sensor can alert the operator that a particular motor is overloaded or has an electrical short."
Manges recommends that companies install cheap temperature sensors on their motors for condition-based maintenance. "Maintenance personnel should replace a piece of hardware based on its condition, not time of service," he says.
The U.S. nuclear power industry has become an "early adopter" of wireless technology, largely because wiring nuclear plants can cost as much as $2,000/ft. The Comanche Peak Nuclear Power Plant outside Dallas, Texas, currently boasts the world's largest network of industrial wireless sensors. The Nuclear Regulatory Commission looks to ORNL for guidance on the installation of wireless technologies in nuclear power plants.
In contrast with other myths that take a long time to develop and even longer to disprove, the myth that wireless technology is unreliable should be dispelled almost as quickly as it was formed. —Carolyn Krause
Web site provided by Oak Ridge National Laboratory's Communications and External Relations