RENO, NV—On an uncharacteristically rainy day in western Nevada, a small tour bus of journalists rumbled past security gates at the Ormat Steamboat Complex in Washoe County. We were there to learn about geothermal power, a renewable energy resource produced by transferring heat from underground rocks up to power plants.

Most people think of Iceland when they think of geothermal power. On that island, approximately 90 percent of homes are heated by geothermal energy. But some 12 gigawatts of geothermal power are generated worldwide, and the US is one of the largest producers of it, generating nearly 3.4 gigawatts in 2013.

Ormat’s Steamboat Complex is within the Reno city limits, and it’s made up of seven smaller plants that collectively generate 78 megawatts of power. A typical coal-fired power plant can generate around 660 megawatts of power, so Ormat’s 78 megawatts are not a lot by comparison. But when compared to other renewables, geothermal has some advantages.

“The darling in California is solar, in Texas it’s wind, but both of those are intermittent power sources,” Bob Sullivan, an Ormat vice president, told the group. “Geothermal is a base load source, and as such it’s not subject to spikes in prices.”



Geothermal energy advocates are quick to point out that when the Sun isn’t shining and the wind isn’t blowing, geothermal facilities can be brought online “in under an hour” as one worker explained to me. Coal-fired plants, on the other hand, have long and costly ramp-up times. Doug Hollett, a program director for the US Department of Energy (DOE) Geothermal Technologies Office, told a round table on Tuesday that the ramp-up issue can be seen in California. The state has been a leader in renewable energy, but it will have to deal with intermittency if it wants to incorporate more renewables into the grid.

“Because of the changing grid, there’s an increasing need and value for resources that are flexible, that can be dispatched to deal with the intermittency issue and the peaking of solar during the day, so California is faced with huge ramp rates in the morning down as solar peaks up and then also in the evening up as solar goes down. And geothermal is capable of providing all of these things. Right now it’s not valued in the marketplace, but the discussion that’s ongoing is to value it."

So why is this discussion about the value of geothermal energy happening now? Part of it has to do with technology, and part of it has to do with perception.

"10 years ago everybody said you won’t see much power from Ormat,” Karl Gawell, executive director of the Geothermal Energy Association, told Ars. “But new technologies are making more power possible.”

In consumer tech terms, the “new technologies” that Gawell references are anything but new. One notable advance occurred in the late '80s, when researchers and entrepreneurs started implementing what is called a binary cycle in geothermal plants. That system allows power plant operators to generate electricity at geothermal wells with lower temperatures.

In a binary system, hot geothermal fluid is pumped up out of the ground from a production well into a tank that contains a separate and secondary fluid, called a "working fluid," that has a lower boiling point than water, like pentane or butane. The surrounding water heats the secondary fluid and vaporizes it. The vapor powers a turbine connected to a generator.

As the fluid cools, it recycles back into the tank, and as the steam from the geothermal well cools back into water, it’s pumped back into an injection well in the ground. It will eventually trickle back into the production well and restart the cycle. With this method, little water is lost, and the power plant is able to maintain pressure underground.

Ormat’s Steamboat complex is a good example of the use of newer tech; it powers its turbines despite pumping water out at between 300 and 320 degrees Fahrenheit. By contrast, flash steam plants, which are still the most common type of geothermal plant today, usually require ground water above 360 degrees Fahrenheit. “People think of geothermal tech as old, but it isn’t,” Gawell added. "It’s very new.”

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Hollett noted that the DOE spends "a lot of effort and a lot of investment on technical barriers, the goal of which is to make development of new geothermal resources increasingly competitive with all other energy sources. So we’re invested across the full gamut, really, of geothermal… there’s hydrothermal resources, enhanced geothermal, low temperature, co-production.”

Being able to use geothermal activity at less-than-ideal temperatures has done well for Ormat. The company bought and consolidated the seven scattered geothermal plants in 2004, and today it supplies power to the entire residential portion of the city of Reno.

Not a gravy train

As Gawell tells it, "Geothermal was dead in the '90s,” and he admits that it’s still a small industry. In 1993, Nevada only generated 150 megawatts of geothermal power. With the help of some measures passed by the state in the late '90s, however, investment started flowing in from a few key companies. Today, Nevada has tripled its geothermal capacity, with Ormat providing 200 megawatts to the state. That’s not an awful lot compared to traditional power sources, but it’s a start.

Still, without government help, geothermal energy as an industry has a tendency for stagnation. The risk involved in drilling a geothermal well is much higher than it is to build a solar or wind farm in a place where it’s usually sunny or windy. At the same time, the monetary reward for drilling and striking geothermal activity is often less than you'd see from drilling and finding, say, natural gas.

“There's no surface manifestation for geothermal usually,” lamented Gawell. “It’s a blind resource.”

He continued, "oil and gas relies on seismology, but for geothermal you’re looking for an intersection of hard rock, heat, and existing fractures.” When you find those, getting the wells in place can still be tough because geothermal activity is best in granitic systems, so it can be harder to drill down. With oil, drilling is easier because the rock is generally softer.

That could explain a lot of the trouble with the technology, called Enhanced Geothermal Systems (EGS), too. EGS, which tries to harvest geothermal energy from hot rock that does not naturally have the right fractures or water supply, has often been touted as the answer to the tepid growth of the geothermal industry. But Gawell himself called it a “tough business,” one that hasn’t seen any real success aside from a few government-funded projects. For now, the industry seems to be setting its sights on increasing efficiencies through the use of different working fluids and finding ways to develop sub-standard resources.



The power of the Earth meets the power of the Sun

One way of making the heat from the Earth hotter is by adding the power of the Sun. Later in the day, our group arrived at the Stillwater Solar Geothermal Hybrid power plant in Fallon, Nevada. In the coming months, energy company Enel Green Power will christen a field of mirrors that will reflect the heat from the Sun into pipes full of geothermal water to get it up to 390 degrees Fahrenheit.

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Even before this solar thermal addition, the Stillwater plant had a field of 89,000 photovoltaic (PV) solar panels that were also supplying energy to the city of Fallon in conjunction with the geothermal plant. (Solar thermal power is different from PV solar in that the Sun’s energy is used to heat a fluid that will create the energy; PV solar cells generate electricity directly by using photons to excite electrons.) The plant has been an example of how solar and geothermal can work together to boost power output and solve the intermittency of solar. According to Bill Price, vice president of engineering and construction at Enel, the small community of Fallon is 100 percent renewable, and the rest of the energy is distributed by NV Energy, a state public utility.

The combination of solar thermal power and geothermal heat is a novel one. As Price explained, "We took one branch of our geothermal output with lower pressure, and we use that branch to heat it to a higher temperature. We add more energy to what will become electricity.”

In building the addition to the existing geothermal plant, "Golden Rule number one was don’t affect the geothermal,” Price continued. "So the [system’s] design is something that boosts, but doesn’t have a long-term impact, on that system. There were a lot of things we didn’t do, because the system would lose pressure” or experience some other negative effect.

Together, the geothermal and solar thermal fields will produce 35 megawatts of electricity, and Enel’s solar PV field will produce 26 megawatts for a total of 61 megawatts.

Enel’s hybrid plant may be a model for other companies in the future. Terry Page, the director of regulatory affairs innovation at Enel, told a Tuesday round table, “We’re seeing some renewed interest in geothermal recently in California... In California, with the wind and solar resources, there’s a significant shortfall when the Sun goes down or the wind doesn’t blow.” Luckily, California is also estimated to have a lot of land that may be concealing geothermal activity.

The path won’t be easy, and not everyone is certain it will be lucrative. But Karl Gawell wants to make it happen. “It’s quite clear that the next five years are going to be critical for the geothermal industry,” he said at the industry round table on Thursday. "Can we not just sustain the growth that we’ve had but can we really make that step out into a new growth curve for the industry?”