California is scrambling to prevent a repeat of deadly wildfires caused by the electrical grid, and Sunrun wants to help.
The home solar and storage installer argues in a report out today that these resources could be operated to reduce the odds of distribution wires coming into contact with other objects and sparking fires. Simultaneously, energy resources at homes and businesses make those customers less reliant on the wires and more resilient in the face of both planned and unplanned outages.
At its highest level, the argument holds that one way to reduce the risk of grid-caused fires is to invest in more of the products that Sunrun sells. But it's not claiming to be the only option — the logic applies to larger systems for schools, fire stations and businesses, which would fall to a broader ecosystem of companies to deliver.
"Customers are adopting behind-the-meter solar-plus-storage for their own resilience, but there’s an opportunity to coordinate with utilities," said Audrey Lee, vice president for energy services at Sunrun.
After back-to-back seasons of deadly conflagrations, California is looking for any ideas that can stop the grid from causing future fires. State officials are convening an inaugural Wildfire Technology Innovation Summit in Sacramento Wednesday to solicit answers.
Sunrun's report anticipates that conversation, while building on an earlier one. The company has long argued that distributed energy offers a favorable alternative to the centralized, capital-intensive electrical grid structure of yore. The catastrophic failure of that system in the face of wildfires, which drove utility Pacific Gas and Electric to bankruptcy, generated a new specific point to add to that long-simmering debate.
Fight the sag
To prevent the grid from causing fires, utilities have to worry about sag, the physical tendency of wires to drop closer to the ground when they heat up. When the lines sag, they can bump into other power lines or objects and cause sparks. Both hot weather and power flow contribute to sag.
This phenomenon is not the only cause of wildfires linked to the grid, but it played a role in 2017, for instance, as the source of the deadly Cascade Fire in Yuba County, according to Cal Fire.
One way to avoid the risk of sparking is to cut power to a circuit when the utility predicts a high risk of fire. This approach suffers two major problems: It disrupts service to homes and businesses, violating the utility's central duty of delivering electric power; and the prediction mechanism for fire risk is fallible, as seen in PG&E's decision not to de-energize in the runup to the massive 2018 Camp Fire.
Instead of shutting off power, Sunrun suggests, utilities could call on locally situated solar and batteries to pick up some of the load, reducing the amount of power flowing through a circuit that's getting too hot. This would support a dynamic approach to thermal limits, allowing utilities to tweak distribution operations based on changes in conditions without shutting things down completely.
Currently, no particular product or service exists to facilitate this. It would require the distribution utility to develop localized sensors to identify when a circuit is heading into the danger zone; then the utility would need to send commands to whatever third party owns or controls devices near that circuit. Presumably the third parties would want some form of compensation for this service.
This setup would resemble a virtual power plant, whereby disparate solar and battery systems get aggregated to deliver monetizable grid performance. That's what Lee's team specializes in. "Virtual distribution infrastructure" would just be pegged to measurably reducing sag in the wires, rather than a more typical capacity or demand response deliverable.
The paper acknowledges that solar and storage deployments haven't reached sufficient levels to deliver this service everywhere.
"However, increasing uptake in at-risk locations will open opportunities for these technologies to assist utilities in active network management to address fire risks in the future," it says.
This approach would need to work in concert with other strategies.
PG&E has said that one of its high-voltage transmission lines suffered an outage at a time and place close to where investigators say the Camp Fire began, and that an aerial patrol had revealed damage to a transmission tower in that area. The cause of that fire has not been officially determined, but a distribution-level solution wouldn't necessarily protect against problems at the transmission level.
Reduce reliance on wires
Distributed solar and batteries can can also help with systemwide wildfire prevention insofar as they lower reliance on conventional grid infrastructure.
Any company selling home batteries has invoked the resilience pitch, namely, that adding this technology to solar can keep the lights on when the grid goes dark. In the context of pre-emptive de-energization, this value proposition becomes much more concrete, at least in fire-prone regions.
Sunrun warns that de-energization should remain a "last line of defense" due to its disruption for customers, but if it happens, solar and storage can help. Using policy tools to get more solar and battery systems to customers in high-risk areas means they'll be better served if the grid gets shut off.
"We’re looking at the possibility of multiple de-energizations in the fire season," said Anne Hoskins, Sunrun's chief policy officer. "You really need to make sure there is some source of local power."
PG&E released a wildfire safety plan in February that largely focused on wires upgrades to improve safety. Its suggestions for customer-sited solutions included building preinstalled interconnection hubs to receive mobile generators, which would likely be powered by gas or diesel.
The utility also touted a single "resilience zone" pilot in Napa County, which will operate this year and could lead to additional installations at some point in the future.
Relying on fossil-fueled equipment for resilience would fly in the face of California's grid decarbonization plans, although it could be justified as a necessary response to emergency conditions. Waiting for a utility pilot to develop into a broader deployment could take years, whereas solar and storage installations take days.
"Right now we have an opportunity to rethink how we’re serving people who live in these more remote areas," Hoskins said. "The centralized system alone is not that sustainable, so we need to start supplementing it."
Customers are free to acquire solar and batteries for themselves, of course. Sunrun's proposal to incorporate these tools in state wildfire policy would serve to expedite that process and organize a network of disparate installations into something more useful for the system.