Early exploration and development The first exploratory geothermal wells in
Kapoho were drilled in 1961–62.
Hawaii Geothermal Project In the 1970s, the Hawaii Geothermal Project was formed to conduct federal and state-funded research. In 2016 the plant's owners were found to be in violation of U.S.
Environmental Protection Agency standards regarding
hydrogen sulfide releases and was fined $76,500 for two incidents in 2013. Additional concerns and opposition to the plant were raised by
Native Hawaiians, who viewed all forms of volcanic activity as
demigod Pele manifestations. They declared geothermal wells and energy production to be a desecration. As quoted in
Nature, the team said it was possibly the first time that "the actual process of differentiation of continental-type rock from primitive ocean basalt has been observed
in situ". In 2015, HELCO announced that Ormat was the winner of a bid to add 25 MW of geothermal generating capacity in the Puna district.
Lava damage and closure in 2018 On May 3, 2018, earth fissures opened inside and around the
Leilani Estates subdivision near the PGV plant, following hundreds of earthquakes over the first two days of May. Concerns of possible toxic hydrogen sulfide gas releases and explosions at the geothermal power facility led to preemptive equipment shutdowns and inventorying its stockpile of highly-flammable
pentane. Earthquake frequency began increasing and the first cracks appeared in Leilani Estates on May 1–2; the plant was taken off-line approximately three hours after it received the first report that lava had begun to flow on May 3. All pentane stored at PGV, approximately , was removed by the morning of May 10. Over the following weeks, the wells were stabilized with cold water—the weight of the water was sufficient to prevent steam from rising—and allow them to be plugged. One well, KS-14, possibly super-heated from close proximity to magma, could not be quenched and was filled with
drilling mud in an attempt to stabilize it. The wells were then sealed with metallic plugs, which arrived at the site on May 22, that PGV officials claimed could withstand lava. Tom Travis of the Hawaii Emergency Management Agency, claimed that he researched and was unable to find any precedent for lava overrunning a geothermal well that had been shut down like the wells at PGV. The PGV team had spoken with scientists in Iceland who have operated wells within lava fields and provided insights into how lava might affect the wellhead. Capped KS-5 and KS-6 wells were inundated by the lava from fissures 7 and 21 on May 27 and 28. The event was the first time lava had covered a geothermal well. On May 30 a substation and a warehouse containing a drilling rig were overrun and destroyed by molten rock, cutting the main access road to the facility. A third well was inundated thereafter. Despite the shutdown, Hawaii Electric Light did not expect
blackouts on the Big Island to be caused by insufficient power generation as older, diesel-fueled generators were brought on-line. The plant resumed reduced operations in November 2020. The plan, called the Repower Project, has a goal of 46 MW in Phase 1 and then to 60 MW in Phase 2, and would implement the increase in power generation by replacing 12 operating power-generating units with as many as four upgraded power-generating units, operating on the existing grounds of the current facility. PGV published an
Environmental Impact Statement Preparation Notice on the July 23, 2022 edition of “The Environmental Notice”. In February 2024, it was announced that a new power purchase agreement was obtained, allowing a maximum of 46 MW and a minimum of 30 MW. This would be achieved by replacing old units with three new units within three years. ==Kapoho Geothermal Reservoir== PGV is located in the East Rift Zone of the
Kīlauea volcano, which forms part of
Hawaii Island. The geothermal energy reservoir there is known as the Kapoho Geothermal Reservoir. The geothermal energy potential of the East Rift Zone is estimated to exceed 200 MW. The geothermal reservoir is contained within basaltic rock and relies on the permeability of two major fracture systems. Both fracture systems have large openings, recorded by the drop of drillbits for up to . ==Facilities==