H-D Electric Cooperative has long had an extensive demand response program, but last year it participated in a pilot project that took its load control efforts to a new level.
Clear Lake, South Dakota-based co-op served as a test bed for GridBallast, a controller that can detect differences in voltage and frequency and then quickly and automatically adjust load by turning on or off water heaters or other connected home devices or circuits.
Such capabilities are expected to become increasingly important as the amount of intermittent generation like solar and wind grows on the grid, leaving electric cooperatives and other utilities to manage fluctuations in generation that can occur with every passing bank of clouds or sudden change in the wind.
GridBallast is a research project led by NRECA and funded by the U.S. Department of Energy’s Advanced Research Project Agency-Energy (ARPA-E), created to develop low-cost load control devices that can operate independently to improve the stability and resiliency of the grid.
“They were looking ahead, and they were thinking about how, once the grid is majority renewable, you have less control over this generation, so how do you maintain order?” says David Pinney, NRECA’s lead on the project. “One thing you can use is load control.”
DOE estimates that by 2045, renewables will be the single largest generation source on the North American grid, doubling in the next 25 years. That growth will put new demands on smart grid management.
“As we’re headed toward huge amounts of renewables, more stability support from loads is going to be really attractive,” Pinney says.
Fast and autonomous
Load control is hardly a new idea, of course, and electric cooperatives have long been leaders in the area. More than 250 co-ops in 35 states use water heaters in demand management programs, and controllable HVAC systems and other electrical appliances and devices provide options as well.
But the ability of the GridBallast controllers to operate quickly and autonomously offers important advantages, Pinney says. It not only improves load management but reduces a system’s dependence on its communications network while also increasing security.
“It can operate faster because it’s autonomous,” Pinney says. “It’s also secure against communication failure and cyberattack because it doesn’t need to be on a network. It can be isolated. That’s the cybersecurity piece. And it’s resilient to communications failure because it doesn’t need to communicate.”
While electric cooperatives around the nation have invested heavily in communications infrastructure, “getting a high-quality network connection to every meter can be really tough, so we were interested in pursuing a solution that didn’t require great communications to work,” he says.
NRECA is working with Carnegie Mellon University, as well as Eaton and SparkMeter—both companies that focus on smart-grid products—on the GridBallast research project. SparkMeter built a controller that can be placed on other residential circuits; Eaton developed controllers for water heaters, which were placed in the homes of 15 H-D Electric members for three months. They’re based on an existing Eaton device with software upgrades that provided new capabilities to sense and respond to changes in voltage and frequency. The upgraded controllers are now available commercially.
The key new feature is the ability to react to surges in power on the system by increasing load, a capability the company calls “GridBallast” mode, says Joe Childs, Eaton’s senior manager for distributed resources strategy.
Voltage and frequency
Co-ops and other electric utilities are used to thinking of load control as primarily a matter of shaving power use at times of peak demand. But as more distributed resources come online, the grid also will need to efficiently use peaks in generation that will occur when the sun is shining everywhere and the wind is blowing hard.
The GridBallast controller’s ability to sense over- and undervoltage and frequency allows it to respond to both demand and generation peaks and valleys, Pinney says.
“If there’s too much generation on the distribution system, voltage will swell too high. If there’s excessive load, voltage will sag too low,” he says. “Bad voltage levels can damage devices on the grid, and if it gets too bad, sometimes devices don’t work at all.”
The relationship is the same with frequency. Surplus generation pushes frequency higher, while a generation shortage pulls frequency lower. But Pinney points out that changes in voltage and frequency are indicative of very different situations.
“Voltage imbalances are very local, usually only within a couple of miles,” he says. “But frequency imbalance happens at the continent scale, so changes in frequency that are hundreds of miles away can affect frequency where you are.”
Frequency issues are the “really scary stability piece,” Pinney adds, because they can signal impending problems with the larger grid. “If frequency goes too far out of balance, generators have to start leaving the grid, and that can make the problem worse,” he says. “It becomes a cascading event. The big Northeast blackout of 2003, that’s how that happened.”
Meanwhile, data from the GridBallast device can help pinpoint and troubleshoot local voltage imbalances—for example, if there are unexpected consumer loads on a circuit, or a concentration of new solar installed in a neighborhood exceeds the co-op’s planning forecasts.
It can also provide a more complete picture of what’s happening on a co-op’s lines.
“The system sends back data every day, and the data it sends back tells the distribution engineer how many times the device activated, what were the frequency or voltage limits that it activated at, how long the event was, and the activity it took to respond,” Childs says. “It sends the information back over the co-op’s [advanced metering infrastructure] system.”
The controllers are installed between the customer’s breaker panel and the device they’re controlling.
“They sit on the power line of the device,” Childs explains. “They’re monitoring the circuit, and that’s how they’re measuring the voltage and frequency.”
GridBallast can give a minute-by-minute look at both voltage and frequency on a system. The controllers are also tunable, so consumers can choose how much of their demand is used to support grid stability.
Matt Hotzler, H-D Electric Cooperative’s CEO and general manager, says making sure the autonomous load control didn’t inconvenience the 15 trial participants was a priority for the cooperative. “We were leery. What if they started getting cold water?”
But the results were positive.
“We didn’t see any problems,” Hotzler says.
In addition to water heaters, Eaton believes energy-intensive hot tubs and pool pumps are among other devices that could be controlled without inconveniencing consumer-members, Childs says.
The greater insights into load that the controllers provide could be valuable for system management, Hotzler says, but he believes consumers’ desire to cut their own costs by participating in load control programs could be one of the biggest drivers to adopt devices like GridBallast.
“It’s certainly important right now for our rates and our members. I think that’s why we have such a good buy-in from our membership,” Hotzler says.
H-D Electric, which serves 3,600 meters in its largely rural territory in eastern South Dakota, has 2,150 water heaters in its load-control program. Those devices can be remotely controlled by H-D Electric’s G&T, East River Electric, headquartered in Madison.
The approach has worked well for managing peak load, Hotzler says, but as the grid continues to evolve, he can see the value of autonomous control.
“As distributed generation starts to come on a bit more, it probably will have a real role in stabilizing the system.”