A new system developed at the Massachusetts Institute of Technology (MIT) can monitor the behavior of electric devices within a building, a factory – and even a 270-foot Coast Guard cutter.
Through a series of tests in late 2018, MIT researchers and Coast Guard members tracked 20 different motors and devices on the Boston-based “USCGC Spencer” ship.
Without requiring any cutting or splicing of wires, the energy monitor uses a sensor that is simply attached to the outside of an electrical wire at a single point.
From the one location, the system senses the adjacent wire’s current. By analyzing tiny, unique fluctuations in the voltage and current flow, the system detects a kind of distinctive “signature” for each motor, pump, or piece of equipment in the circuit.
The sensor’s readings are then monitored on a NILM, or non-intrusive load monitoring, dashboard. The interface provides analysis tools for energy scorekeeping, fault detection, and operating state – a “three-legged stool,” according to lead researcher and MIT professor of electrical engineering Steven Leeb.
The signatures demonstrate when devices are on, sitting idle, or – in the case of the USCGC Spencer – faulty and in need of maintenance.
MIT’s sensors demonstrated that an anomalous amount of power was being drawn by a component of the ship’s main diesel engines: a jacket water heater.
“The ship is complicated,” said Professor Leeb . “It’s magnificently run and maintained, but nobody is going to be able to spot everything.”
Once the protective metal covers were removed from the heaters, the team saw smoke, severe corrosion, and broken insulation.
The advanced warning allowed the Coast Guard to procure and replace the jacket water heaters during an in-port maintenance period.
The MIT-developed technology is especially valuable for relatively small, contained electrical systems, said Leeb, such as those serving a small ship, building, or factory with a limited number of devices to monitor.
The system itself does not require an Internet connection, and can therefore be isolated and secured from tampering and data theft.
Professor Leeb spoke with Tech Briefs about the “three-legged” system, and how its detection of anomalies can be helpful to more than just crewmembers at sea.
Tech Briefs: Take us through the system. What does it look like, and what’s being implemented?
Prof. Steven Leeb: It’s basically something the size of a shoebox that sits next to the electrical panel on the ship. It uses current and voltage sensors to monitor the power feed to two of the main panels in the engine room. That displays information – computed by the box’s signal processing and math algorithms – on a touchscreen display for the crew to see what’s going on.
Tech Briefs: What kinds of problems is this system best designed to spot?
Prof. Leeb: It’s a three-legged stool. It’s for automatic watch-standing on the Coast Guard cutter. It’s for energy scorekeeping, to figure out what energy is being consumed by loads. And maybe the most important application is for condition-based maintenance, to be able to go back and look at the loads that were operating and see whether they were healthy or not.
Tech Briefs: Take us through the Coast Guard cutter test.
Prof. Leeb: Our system is monitoring 20 of the critical loads that support propulsion and electrical generation on the ship.
Basically, through that power monitoring system, we were able to help them find a pretty serious failure in one of the pieces of equipment with the main propulsion engine. A thermal heater had corroded to the point where it wasn’t operating anymore and was electrically not sound.
The problem that it found is a great example of something that’s very difficult to find almost any other way. It’s with a device on the engine that’s sort of immersed in the engine fluids. It’s not an easy thing to check. The Coast Guard really runs their gear well. The crew is spectacular. Even so, there are still things that are very difficult to check or find.
Tech Briefs: What are the traditional options for monitoring energy, and how does your system improve upon those methods?
Prof. Leeb: The non-intrusive system is designed to be a single-point install. Therefore, it’s easy to install, and it’s not a lot of equipment. It goes where the electric utility service meter, for example, might have been in a house.
Strictly from the measurements, it makes an aggregate point. It’s able to tell you the operating schedule, and possibly the health of all the loads downstream – so if there’s 20 loads following it on the panel, it will watch all of them.
It looks in detail, at high frequency, of power signal traces, and associates them with models of what those loads are. The models are used to recognize when the load is operating, as well as figure out when it’s not operating correctly.
Tech Briefs: What was the response from the Coast Guard?
Prof. Leeb: They were pretty excited. One of the Coast Guard officers, who is actually doing his graduate work at MIT, received a commendation from the Coast Guard.
What I think excited them about it is it’s basically like getting another sense, another way to look at the situation in the engine room that’s a different dimension from the way they’re used to looking at it. And it lets them see new things.
Tech Briefs: Where do you envision this system being most useful?
Prof. Leeb: Anywhere where there’s a mission-critical application. It could be an industry floor, a commercial building, a transportation system like a ship – anything where it’s important to you that it works well, stays up, and can’t afford to fail. This has been a particularly exciting platform for making sure that we can find additional indicators above and beyond what you may already have that’ll help you keep things going.
Tech Briefs: What is most exciting to you about this system and its possibilities?
Prof. Leeb: Obviously any time you can help people, that’s a pretty big deal for an engineer. If we built something that people want to use, or makes their lives better, that’s about the end of the line for an engineer.
The research team also included graduate students Daisy Green, Jennifer Switzer, Thomas Kane, and Peer Lindahl at MIT; Gregory Bredariol of the U.S. Coast Guard; and John Donnal of the U.S. Naval Academy in Annapolis, Maryland. The research was funded by the U.S. Navy’s Office of Naval Research NEPTUNE project, through the MIT Energy Initiative.
What do you think? Where else do you see this energy monitor being used? Share your comments and questions below.