In a move designed to ease a growing backlog of residential solar photovoltaic system installations, Hawaiian Electric Co. is preparing to issue revised guidelines that will allow more PV systems to be installed in areas on Oahu already saturated with solar panels if the systems meet certain technical specifications.
The new guidelines will update the interconnection rules put in place by HECO last fall in response to its concerns that excessive amounts of solar energy being generated by rooftop systems could have adverse effects on the utility’s electric grid in highly saturated neighborhoods, a HECO executive said at a legislative hearing Thursday.
The old guidelines issued Sept. 6 were criticized by solar energy industry representatives as being unnecessarily restrictive, resulting in a sharp slowdown in PV installations. Building permits issued for PV systems fell on Oahu for eight consecutive months from May through December on a year-over-year basis, according to data from the Honolulu Department of Planning and Permitting.
Scott Seu, HECO’s vice president for energy resources and operations, said the revised rules are an attempt by the utility to open up the grid to more PV without compromising safety or reliability.
"We wanted to define some options — what we call technical mitigation options — to address a situation on a neighborhood circuit when there is so much energy being generated at certain times of the day by PV systems that electricity is actually flowing backwards into the substation," Seu testified at a hearing held by the House Committee on Energy and Environmental Protection. Power flows backward into a substation when there is more electricity being produced by rooftop PV systems in a particular neighborhood than the entire neighborhood is consuming.
Seu said HECO would issue the new technical standards "this week," but he did not elaborate further. He also said he could not comment on the specifics of the guidelines until they were officially released.
HECO officials are most concerned with circuits where the amount of electricity being generated by PV panels is 100 percent or more of the electricity being consumed on the circuit at certain times during daylight hours. HECO refers to that threshold as 100 percent of daytime minimum load.
When HECO issued its guidelines in September, 54 of its 416 circuits on Oahu had PV generation that was at or above 100 percent of daytime minimum load. Since then the number of circuits at or above the threshold has grown to 105.
Leslie Cole-Brooks, executive director of the Hawaii Solar Energy Association, said it was her understanding that HECO’s new technical standards for saturated circuits recognize, in part, the ability of PV systems to automatically disconnect from the grid when a neighborhood circuit becomes overloaded with solar-generated electricity. That function is carried out by PV system inverters, which are designed to respond to voltage spikes.
Cole-Brooks said HECO’s new technical standards apparently will specify the speed at which inverters need to be able to disconnect from the circuit in the event of a voltage spike.
"Having technical specifications is not the solution, but it moves the ball forward a bit," she said.
Mark Duda, president of the Hawaii PV coalition, welcomed HECO’s effort.
"We’re optimistic that this solution will allow more customers who have been waiting, for in many cases months, to interconnect their PV systems," Duda said. "It shows that when you focus on actual technical issues instead of unspecified concerns that we can work together to resolve these interconnection challenges."
Demand for PV systems has continued to fall this year. Through the first three weeks of January, Honolulu’s total number of residential PV permits issued was 502, a 27.7 percent decrease from the previous year.
