Earlier this year, researchers in Iceland found a new way to transform the heat generated by volcanic magma into electricity. The advancement could be especially valuable in Iceland, a country that has capitalized on its unique geology to derive a quarter of its electricity production and around 90 percent of household heating from geothermal energy.

And it’s just the latest innovation in a series of geothermal energy breakthroughs dating back a century to the first geothermal power generation in Italy in 1906. As these advancements continue, geothermal energy is clearly becoming a major renewable energy source waiting to be tapped — one that’s literally sitting beneath our feet.

“The worldwide market is moving towards double-digit growth,” said Karl Gawell, executive director of the Geothermal Energy Association (GEA) during the organization’s recent International Geothermal Showcase in Washington, DC. “There’s lots of exciting things going on. Several years ago there were projects in 24 countries, this year almost 700 projects are under development in 76 countries across the globe.”

When it isn’t drawing on magma-heated steam, geothermal energy is generated by water heated in underground geothermal reservoirs to create steam and turn an electricity-generating turbine. The hotter the ground, the hotter the resource and the more energy can be generated. Iceland lies on two major fault lines and is one of the most tectonically active places on Earth, making it an obvious geothermal hot spot. The aim of many of the recent technological advances is to generate geothermal power economically from lower subterranean heat levels found around the planet.

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A geothermal borehole in Iceland. CREDIT: flickr/lydur skulason

Modern geothermal generation is surprisingly helpful for meeting climate change goals, even in comparison to renewable sources like wind and solar. The very best geothermal plants generate as few greenhouse gas emissions as hydroelectric plants and less than solar photovoltaics over their complete life-cycle, according to a study by Argonne National Laboratory. Combine this with the fact that the U.S. Geological Survey estimates that the untapped geothermal resource in the U.S. is between 100 and 500 gigawatts, and the emissions savings could really start to add up, both domestically and globally where the resource is much larger.

A geothermal reservoir is a heated body of water trapped underground in cracks and porous rock. These reservoirs are extremely powerful; when the water isn’t trapped, it manifests itself on the surface as hot springs or geysers. To develop electricity from geothermal resources, wells are drilled into geothermal reservoirs. Over time, the water or steam pressure can become depleted, at which point outside resources can be pumped back into the reservoir to recharge it.

A century ago, coal-powered electricity was just emerging as a valuable commodity. Today, with coal’s value undercut by a number of health and environmental factors, geothermal is one of the renewable sources primed to replace that power in the global energy market. With greenhouse gases rising just as sharply as energy production, climate change is creating a similar global push for a paradigm shift to clean, sustainable sources in the electricity sector. In all this, geothermal has a powerful role to play. Unlike intermittent renewable power sources, such as wind and solar, geothermal can provide consistent energy 24-hours a day, making it an appealing baseload replacement for coal and nuclear power that are responsible for keeping the power supply stable and reliable.

The Western Frontier

In the western U.S., geothermal prospects are on the rise, especially in Nevada and California. California already has the largest geothermal field in the world, the Geysers, which contains 22 geothermal power plants amid 45-square miles in the Mayacamas Mountains north of San Francisco. According to Calpine, the largest geothermal power producer in the U.S. and operator of most of the Geysers plants, geothermal satisfies nearly 60 percent of the average electricity demand in the coastal region between the Golden Gate Bridge to the Oregon border. Calpine’s Geysers operation consists of 333 steam wells and 60 injection wells, which require fluid that can be heated and turned into steam. The average well depth is 8,500 feet, with the deepest well being over two miles deep at 12,900 feet.

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A Calpine geothermal power plant, part of The Geysers in CA. CREDIT: flickr/geo thermal

In Nevada, a state known for its abundance of federal land — used by interested parties ranging from rogue cattle grazers to eager gold prospectors — geothermal is joining the ranks of wind, solar, biomass, and hydropower as a renewable natural resource that can be deployed to the grid.

“Geothermal is pretty plentiful here in northern Nevada,” Faye Anderson, northern communications manager for NV Energy, told ThinkProgress. “As a baseload source it is competitive even with fossil fuels.”

According to Faye, NV Energy is exceeding its 18 percent renewable energy requirement for 2013-14 as stipulated by Nevada’s Renewable Portfolio Standard (RPS). Currently, renewable energy accounts for about 20 percent of the power NV Energy provides its customers in southern Nevada and almost 35 percent in northern Nevada. Geothermal provides about nine percent of the total northern Nevada demand. As a public utility serving several million Nevadans and tourists, NW Energy doesn’t build or operate any geothermal plants, rather it has signed power purchase agreements with existing plants since 1983.

Ormat Technologies, based in Reno, Nevada, is one of the companies providing the geothermal expertise to help facilitate this renewable energy shift in the West. While Ormat provides geothermal energy to NV Energy, the company is also branching out into other regions and markets. Earlier this year, a new 16-megawatt geothermal facility, the Don A. Campbell Geothermal Power Plant, started sending power across state lines to Los Angeles using NV Energy’s new One Nevada Transmission Line. That’s not the only unique thing about the plant — it’s also working with relatively cool rock.

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CREDIT: Union of Concerned Scientists

“With a low resource temperature of approximately 260 degrees Fahrenheit, the first for a utility-scale project, this plant is a great innovation and a technological leap forward,” said Bob Sullivan, VP of business development at Ormat, during the International Geothermal Showcase. Sullivan said that this technology, now proven, will open the door to other geothermal reservoirs previously considered risky or uneconomical.

The Don A. Campbell plant is a binary cycle geothermal plant. It uses low temperature geothermal resources, which also happen to be the most abundant. It can generate electricity using water from 194° F to 347° F by routing it through an above-ground heat exchanger, which then heats another fluid such as pentafluoropropane that boils at a lower temperature than water, that turns into steam and spins a turbine. All of the produced geothermal water is injected back into the reservoir. This is quite an evolution from the original geothermal electricity projects over 100 years ago which used steam directly from the ground to turn turbines.

Behind The Scenes

While electricity-generating geothermal technology is advancing, the bulk of the time and cost expended goes to exploration and drilling for the resource. Recent advances in oil and gas drilling, which can translate over to geothermal sensing, exploration and drilling techniques, are helping to facilitate innovation in the area. However, developers say a lot of the uncertainty around geothermal in the U.S., and part of the reason it hasn’t grown much in recent years, is due to the unreliable nature of the Production Tax Credit (PTC) and Investment Tax Credit (ITC).

“The way the PTC and ITC have been done for years in the U.S. has sub-optimized development of all renewable resources, including geothermal,” Craig Mataczynski, CEO of Gradient Resources and GEA board president, said at the GEA Showcase. “While wind and solar projects can develop in a year or two, often fitting into the PTC or ITC periods, geothermal has a five or 10 year development cycle and it’s hard to know whether that incentive will be extended and will exist when it’s time to bring the project online.”

Not only has the on-again, off-again nature of the tax credits caused financiers to forego projects or to overextend prematurely on projects that run into difficulty, it has also had far more deeply-entrenched impacts, according to Mataczynski.

“The worst effect of all this is that there has never really been, in recent history, the development of an industry,” Mataczynski said of geothermal energy. “It’s allowed projects ready to go to be built, but as far as developing an industry and bringing in new technologies and methods of drilling to reduce costs, those haven’t come to market which has kept our prices up.”

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CREDIT: National Renewable Energy Laboratory

Financing isn’t the only challenge inherent in developing a geothermal energy industry. Geothermal plants require water to produce steam or heat another fluid to turn the turbines and if they aren’t supplemented, geothermal reservoirs can run dry. This can be a challenge for operators, particularly in the drought-stricken West. There are ways of dealing with the water need sustainably, however. Ormat cools its geothermal fluid after running it through the turbine and injects it back into the underground reservoir to be reheated and reused. The Geysers in California use wastewater injection to provide around 20 million gallons of reclaimed water per day to supplement the original steam pressure.

Developers have continued to focus on the promise of geothermal power, however, and keep pursuing technological innovations to increase efficiency and bring down costs. One example of this can be seen in another geothermal plant in Nevada, currently in the process of adding a Concentrated Solar Power (CSP) system to a geothermal power station that is already paired with a 26 megawatt solar photovoltaic facility.

The Stillwater geothermal power station will be the first geothermal plant to be coupled with a CSP facility, showing the potential for geothermal plants to link up with other renewable energy sources and share resources, infrastructure, and transmission lines, which reduces the cost and overall environmental impact of the projects. This is important because in the West, sprawling solar and wind plants can have negative impacts on local wildlife; siting them alongside geothermal could ameliorate that tension.

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Part of the hybrid solar-geothermal Stillwater power plant in Nevada. CREDIT: Geo Thermal

And because geothermal energy is not intermittent like wind or solar power, which generate when the wind blows or sun shines, it can fill the role that has long been played by fossil fuels and serve as a baseload power source. That not only helps to lower emissions but provides needed stability to the electric grid.

“Right now the power grid stays very stable because there are machines spinning very fast with lots of inertia that can absorb disruptions to the system,” Sullivan said in describing how geothermal fits into the mix. “If we take all the big machines off with coal and nuclear and replace with PV, nothing is spinning. The grid has the potential to become very unstable.”

Sullivan said that California is making a major investment in energy storage to try and deal with a higher reliance on solar and low-inertia wind turbines. Geothermal can help offset some of this investment more cheaply than storage technologies right now, and in doing so can actually facilitate more renewables. “Geothermal enables higher technologies and it meets climate change goals in doing so,” said Sullivan. “There is a big piece of pie out there for renewables, plenty for everyone, they just need to be valued properly.”

Geothermal plants also don’t need the additional peaking capacity backup that many wind and solar plants need, which can involve having gas power available to guarantee a certain level of power at all times. Those in the geothermal business want this added value to be incorporated into Requests For Proposals and other instances where different renewable projects are under consideration so that geothermal plants can win more bids.

Pacific Gas and Electric, one of the largest electric utilities in the country, is grappling with just this question as it aims to meet California’s 33 percent Renewable Portfolio Standard (RPS) by 2020.

“As PG&E moves towards meeting this goal, higher levels of renewable energy will be coming online in a short time frame,” Denny Boyles, external communications representative at PG&E, told ThinkProgress. “This has underscored the need for new flexible capacity to accommodate expected load along with the growing level of intermittent resources. Projects that are able to provide that flexibility are valued accordingly.”

Boyles said that geothermal contributed nearly 3,700 gigawatts in 2013 for PG&E, nearly five percent of their retail sales.

The International Showcase

Internationally, the geothermal industry is growing much faster than in the U.S. The GEA report released at the recent showcase found that there were almost 700 projects under development in dozens of countries across the globe. With the international power market booming, geothermal showed a sustained growth rate of around five percent, while “U.S. growth was flat because of policy barriers, gridlock at the federal level, low natural gas prices and inadequate transmission infrastructure.”

Mataczynski put it similarly. “The reason geothermal is doing well internationally is that it competes with other energy sources on a pure cost basis. People aren’t doing it because they are altruistic and it’s good for the environment — which it is — they are doing it because it provides the lowest cost alternative form of energy that they need to drive the economy and improve their standard of living.”

Commercial light bulbs may have been invented over a century ago, but millions of people still lack the electricity to turn them on. Also a century after being invented, geothermal power may finally be poised to help make that switch.