The first thing you notice is the smell. It sneaks up, overwhelming the senses. The acrid odor is immediately identifiable as sulfur — a familiar, yet still unpleasant, scent of rotting eggs.
That stench stems from the four Northern California Power Agency geothermal power plants located in an area called The Geysers. The plant continuously supplies Lodi with 12 megawatts of renewable energy, which is about a tenth of the city's needs during a 90-degree day, or a quarter of the city's nighttime use.
The Geysers is the largest naturally occurring steam field that is harvested for energy in the world, said Geothermal Facilities Manager Kevin Cunningham.
The landscape has a lake of magma under highly fractured granite rock. The small cracks allow moisture to seep in, and when it is heated by the magma, it turns into steam.
But human contributions focused on renewable energy also make the plant unique.
"I think we're the only people in the world that can say we are geothermal, solar and hydro all mixed into the same organization," Cunningham said.
'It's not space-age technology'
High in the Mayacamas Mountains, the two NCPA plants are almost 50 miles north of Napa by highway and smack-dab in the middle of nowhere.
Both plants have two power generation units in each of them. The rest of the 19 units in The Geysers are owned by Calpine, an independent electricity company.
The wells for the 23 plants at The Geysers are scattered throughout 40,000 acres — stretching from Sonoma to Lake counties.
Steam spewing from the natural geysers in the mountains is captured, and green pipes weave up and down the hills guiding it to the NCPA power plants. The steam then rotates a turbine, which is hooked up to a generator. From there, the energy is released to power lines, which connect to one of PG&E's transmission lines, transporting the energy to cities.
"There's no combustion turbines, there's no reactors, there's no boilers — everything is clean," said Steve Enedy, steam field superintendent. "The steam comes right out of the ground, and it was created by Mother Nature. … It's heat left over from the volcanic processes just over a million years ago."
Once the steam has powered the turbine, NCPA removes certain gases and runs them through a chemical process, turning the hydrogen sulfide into elemental sulfur, which is then collected and sold later.
The rest of the steam is converted back into water and placed into a large cooling tower that funnels the water through to bring the temperature down from 140 degrees Fahrenheit.
The plant then reinjects the water into the geysers to replenish them.
"It's not space-age technology," Enedy said. "It's old power plant technology applied to this geothermal fuel, and that's what's innovative."
The Starship Enterprise
It may not be space-age technology, but it sure looks like it.
The drone of the turbines and the whir of machinery, sounding at times like a steam engine, quickly makes it impossible to talk in the plant. Workers communicate through a series of well-known hand signals while wearing earplugs.
Above the power plant, Bill Cude stands in an office that looks like something out of a science-fiction movie: Giant computer screens with a multitude of video feeds crowd the room, and the walls are covered in gauges and switches.
Having access to the turbines, the pumps, the geysers and everything in between, Cude, who has been in the business for 28 years, is essentially the head honcho at the plant.
Describing the plant as the Starship Enterprise, Cude even monitors the plant's solar power. NCPA added its first solar field 18 months ago, with another installation last October.
The electricity is used to pump treated wastewater from Lake County and Santa Rosa, which is then injected back into the wells in order to replenish the geysers.
The newer panels come complete with technology called single-axis tracking that allows them to pivot, following the sun across the sky.
In total, those same panels span 20.5 acres, generating 1.9 megawatts of solar energy — enough to power almost 1,860 homes.
Expected to last 20 years, the panels were paid for in part by the California Solar Initiative, which offers incentives and rebates to companies who install solar power.
The panels operate using photovoltaic cells, which capture the sunlight, creating a direct current similar to the one found in a battery. That current is then converted within the solar cell to generate an alternating current — the energy we use to power our houses.
Not only does NCPA work with solar and geothermal, but they also generate hydroelectric power. When water is injected back into the wells, it can drop to as much as 12,000 feet. The falling water rotates yet another turbine, creating energy to power at least some of the plants' operations.
The underground turbine is the only one of its kind and part of a project that NCPA hopes to expand upon.
Preserving The Geysers
The drive up to the plants is a twisty ride, the road meandering through the sleepy towns of St. Helena and Calistoga. On days when the clouds roll in and the wind dies down, nearby communities sometimes can smell the egg-like odors.
"It's called hydrogen sulfide; it's a noxious gas," Enedy said. "It's naturally occurring in the steam itself. (The hydrogen sulfide) is in small quantities … but it just smells bad."
The large collection of sulfur was originally discovered in the 1920s, when the original families who settled in the mountains saw steam coming from the ground. The settlers drilled into the granite to make shallow wells for resorts.
Investors then decided they would try to harness the steam to make power. The first power plant owned by PG&E opened in 1960. While three more opened in the '60s, the plants did not start proliferating until the 1970s when there was more of a focus on renewable energy.
A whole slew of companies rushed to the mountains to open up power plants, and by the 1980s, the amount of steam rapidly declined.
"We poked too many holes," Cunningham said. "There were too many operators and not enough efficiencies."
Two dozen companies started selling off their plants, until Calpine and NCPA remained the sole operators in the area.
In the early '90s, NCPA started pumping wastewater from Lake County to reinject into the geysers, replenishing them. The plant also reinjects water after siphoning off the steam.
But more water is withdrawn than put back in. NCPA takes out 40 million gallons in steam a day, but only puts 30 million back in.
NCPA hopes to secure more water to keep the geysers going.
"We have never recovered from that decline," Cunningham said. "What we did was stop the decline."
He pointed out that the resource is valuable because if the power plants take care of The Geysers, they will remain a significant source of energy.
"I don't think it's fair to say 'infinite,'" Cunningham said. "But the steam is still going to be there long after we are gone and need that resource."