Power play: MEMS-based energy monitoring comes of age


Sensors, software protocols have reached a point of maturity where real world rollouts are finally feasible

By Jo McIntyre

Various technological developments related to monitoring operations within electric grids, industrial plants and commercial buildings have converged recently to make more sophisticated sensor networks possible.

Refined IEEE wireless communication standards for sending data, and falling prices on sensors have brought costs down far enough to get products into the marketplace. And mesh networking has developed enough to allow for continuous connections and reconfiguration around broken or blocked paths, so a network can still operate even when a node breaks down or a connection goes bad. The next step is to monitor usage at the residential or even appliance level and transmit that data to the electric grid.

The power generation industry also needs to be able to regulate renewable energy inputs into the grids, says Dan Rastler, technical leader of the distributed energy resources program at the Electric Power Research Institute, or EPRI, based in Palo Alto, Calif.

The Institute has long applied new technologies to the power generation and utility industries to manage distribution systems. Today, EPRI is trying to integrate sensors into technologies for load control of, for example, air conditioning systems transmitting data through wireless or fiber optic systems.

“As we see more expansion of distributed power and renewables, like photovoltaics, we’ll need to have more capability to provide information to the service network,” Rastler says.

Harry Roman, former emerging technology and transfer consultant at PSE&G and a longtime proponent of sensor networks, displays a MEMS acoustic sensor. Photo by John Madere
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Public Service Electric & Gas (PSE&G) in New Jersey is also incorporating some of the new technology into its operations.

On July 4 this year, PSE&G received a patent on MEMS-actuated fiber optic-based acoustic emission sensors, two to five microns in size, to monitor transformers, and is developing similar technologies for cables and power lines.

“We have to think about how to overlay a system onto what exists to improve its operation,” says John Del Monaco, manager of emerging technology and transfer at PSE&G.

“We’re focused on incorporating sensors into our system and getting information back, all done in real-time, to understand what’s happening in the system.” He said the company is striving to make its existing infrastructure work as a “smart and reliable utility.”

PSE&G has installed a prototype sensor system in a 230kV-to-13kV transformer, which steps bulk energy transmission voltage down to primary distribution voltage.

The company monitors data from the sensor, which is installed in an eight-inch probe that goes into transformer oil. The probe measures certain frequencies in acoustic emissions and compares that data to data from existing acoustic sensors outside the transformer.

PSE&G is working on another sensor that will monitor relay settings, water levels, pre- and post-fault conditions, transformer oil temperatures, moisture and ambient temperature.

With their research partner, New Jersey Institute of Technology, PSE&G is also developing temperature sensors that will be on transmission lines, looking for problems in splices, and transmitting information wirelessly to a company location.

Farther into the future is a project designed to understand information for network protectors for the company’s distribution system. Information will be sent to division locations via a fiber optic network. This is a joint project envisioned being done with a manufacturer and EPRI. Other areas under development are communication devices to transmit data back to division locations, and the software to interpret the data.

To address what could be a burgeoning market, several manufacturers are already making sensor network products. For example, in mid-October, Emerson Process Management and Dust Networks announced that the division will use Dust Networks’ time synchronized mesh protocol as the communications technology to run Emerson’s new in-plant wireless field networks.

Dust Networks’ approach to mesh networking connects monitoring and control systems with sensors, actuators and other devices that interact with the physical world. Illustration courtesy of Dust Networks
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Emerson Process Management is a division of St. Louis-based Emerson. The company has fluid level, temperature and acoustic sensors, built specifically for the process control industry, including oil fields and refineries, as well as companies monitoring switching stations and power plants.

After three years of evaluations, Emerson now has supply systems ready for mainstream manufacturing use. Features include a rugged design for industrial environments, vibration resistance and an industrial temperature range of -40 to +85 degrees Celsius.

Dust Networks, based in Hayward, Calif., makes low-power wireless sensor networking systems facilitated by their mesh protocol. Rob Conant, co-founder and vice president of business development for Dust, said a key change in the industry has been agreement on the IEEE 802.15.4 radio standard for low power radio signals.

“I think that ultimately what will happen will be more effective monitoring and control,” Conant says. “This technology reduces the cost of collecting data by a factor of ten.”

Another technological development, Conant said, is more extensive predictive maintenance. By monitoring vibrations in motors, pumps, generators and turbines, he said, one can see failures developing and prevent unplanned downtime.

These technologies are converging as costs come down, especially wireless technology. “It has happened in the past couple of years, but it’s just coming into end user products right now,” Conant said.

T.J. Glauthier, an EPRI alum, is a member of the strategic advisory board formed by EnerNOC Inc., a Boston-based company that makes demand response and energy management products. He is working on renewable energy and issues related to climate change.

EnerNOC products enable energy users and suppliers, system operators, and utilities to manage distributed energy resources with network operations centers for online monitoring and control of power usage at remote sites.

“Economists argued years ago that this made sense, but we didn’t have online communications before,” Glauthier says. “EnerNOC is working with IBM, grocery stores (and) hospitals to help them reduce power in non-crucial ways like lighting or air conditioning.”

The role for MEMS sensors may be in some of these applications - to cut back lighting some, but not all, he said. “What we’re going to find is that the sensors will allow us to go to another level - monitoring usage or temperature very carefully. Sensors need to be cheap, effective, reliable.”

Kurt Yeager, another EPRI alum, is now leading a study on energy policy and climate change for the World Energy Council. He is working with Bob Galvin, the former chairman of Motorola, on the Galvin Electricity Initiative.

They are seeking to develop so-called micro-grids that incorporate advanced electronic control systems to go between consumers and the grid to raise quality and reliability of bulk power by moderating the power in the micro-grids. Micro-grids use electricity from the bulk power system and also can operate independently of the bulk power system with whatever renewable power sources they have available, like photovoltaics.

Yeager says that while it’s hard to incorporate renewable energy into the electric grid system, sensors and controls using MEMS technology are at the heart of networking systems that can facilitate a change.

“They are all micro-controls,” Yeager says. “(They are) the brains of the system. The first step is to put in sensors that can detect disturbances before they happen, to take corrective action. That’s driving the sensor revolution today.”