Too much solar can be a problem for utilities.
… Following California standards, Hawaii’s electricity regulator, the Public Utilities Commission, has set a threshold dictating that, once local [solar] power generation reaches 15 percent of the peak electricity typically found on a circuit, Hawaiian Electric can require an expensive study gauging what additional rooftop projects would do to energy reliability. And the utility has not been shy in mandating these reports.
The studies are an open-ended expense, costing thousands of dollars for a large home, and, on average, $45,000 for a commercial installation, said Mark Duda, a solar developer and president of the Hawaii Solar Energy Association (HSEA).
In many instances, this threshold has served as a cap to solar development. Without it, Duda estimates that the number of his commercial customers would have at least doubled.
“Historically, if you had to do the study, people would just say forget it,” Duda said.
The story is not so straightforward, however. Hawaiian Electric has at times allowed rooftop solar penetration higher than 15 percent, noted Darren Pai, a company spokesman.
“On many circuits we’ve taken a look at the specific configuration of the circuit and allowed higher amounts of [solar] integration without doing interconnection studies,” Pai said. “We’re trying to enable as many [solar] installations as possible without creating more hurdles for our customers.”
Still, many communities find themselves near the limit of what can be installed.
Even after regulators raised the study trigger from 10 percent to 15 percent last year, 72 of the islands’ more than 700 circuits remain at the threshold. Utility maps laying out the circuits, with the 15 percent regions painted red, make it seem the islands are starting to come down with chickenpox.
The situation is especially dire in Molokai and Lanai, two of Hawaii’s smaller islands, according to Mangelsdorf, the solar developer, who works on both islands. “Molokai, for example, within the next six to 12 months will be effectively closed down,” he said.
Intense competition for limited space is driving down costs, and some companies, seeking a quick profit, are doing shoddy installation work, he added. Barring an increase in the 15 percent rule, the solar industry is in dire straits.
“We’re going to see a winnowing,” Mangelsdorf said.
While they may seem capricious to developers, the solar limits are not arbitrary.
Like most utilities, Hawaiian Electric has deep-seated concerns about maintaining the stability of electricity to all its customers. To understand why, imagine the evening news after a damaging storm. Even before the news anchor mentions how many people died, they will list how many are without power. After even a momentary disruption, utilities will hear a chorus of complaints from their customers, Delaware’s Hegedus said.
“Utilities know that,” he said, “and so they’re extremely compulsive about reliability.”
One way this compulsion has manifested itself is the 15 percent rule. At its core, the rule is not solely about rooftop solar. It applies to any electricity a household could connect to the grid, from a gas generator to the modular nuclear reactor your neighbors must be using to power their stereo. Any of these power sources are out of the utility’s control, and the electricity they send back into the grid could have mysterious effects.
A tangible example of this unpredictability is voltage, the steady electrical signal — 120 volts in the United States — that electronic gadgets are designed to operate on. Move outside a 5 percent range of 120 volts and devices start to fry. The utility, however, only sets voltage at its substations, and the voltage decreases as it strides along a circuit, a walk carefully calculated by the company.
Add rooftop solar into this equation and it gets tricky, NREL’s Kroposki said. “They may raise voltage above the nominal limits,” he said. “And the utility can’t [stop] that.”
Reliability concerns are fair, Earthjustice’s Moriwake said. But the 15 percent rule is not based in science. It is a rule of thumb, he said, “yet a lot of people take it as gospel.”
“It’s a conservative assumption of a conservative assumption,” he said.
Indeed, the 15 percent rule is a bit of a mongrel, created mostly to allay safety concerns but adapted to reliability rules, Kroposki said. Put simply, it began as a way of preventing utility workers and the public from electrocution.
Regulators had concerns that local electricity generation could create, in a poetic turn of bureaucratise, “unintentional islands,” electrical wires that remained live after the power company had shut off its centralized source. Inadvertently fed by local producers, these charged wires, perhaps toppled by a storm, could threaten the public or emergency crews sent to repair the problem.
To stave off the formation of these islands, regulators have sought to have more centralized than local power available on the grid. It’s a “rule of thumb” that the minimum amount of electricity on the grid is one-third the peak. Round that third down to 30 percent and divide it in half, for safety’s sake, and out springs the 15 percent rule.
It was an engineer’s estimate. “Utilities assumed they wouldn’t see high penetrations of distributed generation,” Kroposki said. “So this rule wouldn’t really affect people.”
There are reasons to suspect the 15 percent rule is too conservative. Minimum electricity use during the day, when solar is relevant, is much higher than at night. New solar panels automatically cut off from the grid when centralized power goes down, preventing islands. And there are numerous examples of circuits operating well beyond 15 percent penetration, Kroposki said…