More-Reliable Power Grids
Combining nanotechnology with wireless sensor networks could provide a cost-effective solution to widespread power failures.
The power grid is, for the most part, built on antiquated technology. When transformers and other equipment are installed, they are expected to work for about 40 years, replaced only when they fail. Additionally, components of the grid–from substations, to transformers, to circuit breakers in homes–can’t signal to the local utility companies when damaged. This makes some power failures a surprise, and it protracts the fixing process, as utility workers need to physically identify the place where equipment is damaged.
To try to make a better grid, researchers at the University at Buffalo (UB), in New York, are investigating ways to retrofit the present-day infrastructure with some new technology and communication systems. They suspect that the recent advances in nano-sensor technology and wireless networks could be key to providing an inexpensive and efficient way to monitor grid health and help repair damage more quickly.
The idea is to disperse sensors with integrated processors and wireless capabilities throughout the grid, says W. James Sarjeant, chair of the electrical-engineering department at UB. The chip would be about the size of a pinhead, he says. The tiny devices wouldn’t need to be built into the equipment, he adds, but would simply be placed near it so that they could pick up electromagnetic signals. As the sensors collect information, the onboard processor would churn through the data, and transceivers would send and receive data to and from other sensor nodes, or a central station.
Sarjeant and his interdisciplinary team are considering building their nano sensors out of conventional semiconductor material such as silicon, gallium arsenide, or gallium nitride. This way, says Jonathan Bird, professor of electrical engineering at UB, the sensors would be compatible with existing micro-fabrication technology. Also, he says, various types of sensors could be fabricated on the same chip.
In particular, the researchers suspect that a class of sensors called “quantum point contacts” could be a potential candidate for their system. They’ve shown that quantum point contacts can be used as compact nano-scale circuits that filter out particular electrical frequencies. This function could be useful because power equipment sometimes emits subtle yet distinctive electromagnetic signatures prior to breaking. The researchers are currently testing if their nano-scale circuits can effectively filter out the junk signals to help detect the signatures that precede the breakdown of insulating materials in grid components.
Another type of sensor that the researchers are exploring is called a nano hall-effect transducer. This device could sensitively detect variations in the magnetic fields generated by the system. When electric current runs through a power line, a magnetic field proportional to that current is produced near the line. If the sensor detects fluctuations in the magnetic field near a power line, this could indicate a problem.
The key to all of these sensors, says Bird, is that they only need to be placed in the vicinity of the components in a power system. This allows the researchers to “sensitively monitor the state of the power system without the need to tap into it directly,” he says. This is advantageous because directly accessing the grid could be expensive and time-consuming.
But sensing electrical signatures and magnetic fields are only part of the monitoring technology. Communication between sensing devices is also important. The researchers hope to employ the sort of wireless technology used in ad-hoc networks (see “Souped-Up Mesh Networks”) so that the sensors themselves can adjust to each other’s status if one is running low on power, for instance, to more effectively monitor the entire grid. “The advantage to this is that if an element fails, or a portion of the [sensor] grid malfunctions, the entire network will reconfigure to keep monitoring the grid,” says Bird.
Currently, there are other technologies, all much larger than the proposed UB system, that are being explored to monitor power grids, says Don von Dollen, program manager for the Electric Power Research Institute, in Palo Alto, CA. But the technology that will ultimately gain widespread adoption is the one that is the most cost-effective, he says. “It all comes down to price.”
Within the past few years, there have been advances in the fields of data processing, sensor technology, and communication–all necessary aspects of making a grid monitoring system technologically reliable and economically feasible. Research on micro sensors and wireless sensors, von Dollen says, is “an exciting area because there’s an awful lot of potential.”
The UB researchers expect to have a prototype nano-scale sensor system within about five years, with a larger-system version coming in a few years, says Sarjeant. While the promise of nanotechnology is great, it is still a relatively new technology that’s only received serious research attention for about 10 years, says Martin Moskovits, professor of chemistry and biochemistry at the University of California, in Santa Barbara.
He notes that much of this new grid monitoring project will probably be “very exciting fundamental research,” and practical issues will most likely need to be resolved as the work progresses. However, Moskovits believes it’s worth it. “The grid affects so many of our lives,” he says, “it’s an excellent place to put effort.”