Tower of Power: The World’s First Wind-Solar-Natural Gas Plant0

GE Works

Progressive thinkers like Amory Lovins of the Rocky Mountain Institute have said for some time that one way to decrease uncertainty in our national power grid is to add more “distributed generation,” which means more sources of wind and solar power, closer to where the power generated is being used. By clustering different sources of energy, less is wasted through transmission, and it may be easier for switching operators to respond to instantaneous changes.

Now, for the first time, a large-scale power project will embody this distributed generation by incorporating wind, solar, and natural gas at the same facility. The pilot 530-megawatt plant is scheduled for completion in Karaman, Turkey by 2015. It will be built by Turkish firm MetCap Energy Investments and will feature a 22-megawatt GE wind farm, a 50-megawatt eSolar “power tower” solar thermal system, and FlexEfficiency gas turbines also from GE.

This project combines two renewable technologies and natural gas in the same power plant.

GE has dubbed the project the first “Integrated Renewables Combined Cycle” system, and if all goes well, it may be a harbinger of more integrated projects to come.

Paul Browning, chief of GE Energy’s thermal products division, said in a statement, “This project combines two renewable technologies and natural gas in the same power plant and demonstrates the benefits it can offer to power the future grid. Integrated renewable combined cycle power represents a significant growth opportunity for GE Energy.”

Shortly before the ambitious Karaman project was announced, GE and MetCap Energy both purchased stakes in eSolar, a Pasadena, California-based startup led by tech entrepreneur Bill Gross. eSolar had been working on advanced algorithms and imaging technology to boost the efficiency of the classic solar thermal power plant.

Efficiency wins the day

Natural gas has long been an important complement to renewable energy sources like wind, solar, and biofuel facilities. Natural gas burns cleanly and gas turbines are fast and flexible, so they can be quickly turned up or down—varying the amount of power produced in moments. This “switchability” can supplement more intermittent power affected by subtle changes in the wind or sky.

In eSolar’s model, thousands of relatively small mirrors called heliostats are tightly controlled to focus the sun’s power on a boiler that sits atop a tower. As with other solar thermal plants, all that focused heat turns the water into steam, which drives an electricity-generating turbine. In some models, oil or salt is used instead of water in the boiler. But eSolar’s design is particularly efficient, in part because it allows the water to be boiled at a temperature 200 degrees higher than older parabolic mirror systems.

Also unlike most solar thermal plants to date, eSolar’s model is highly modular, and is based on groups of small mirrors focused on relatively short towers. Want more power? Add another module of mirrors and a tower.

Our secret sauce is in our software.

Dale Rogers, eSolar’s senior vice president of projects, called the company’s strategy a “paradigm shift.” Rogers said, “These concentrated solar technologies have been around since the early 1980s, and since then a general consensus evolved to move toward a single tower, a single receiver, and a single field of mirrors. From an economic perspective that made sense for a lot of reasons because people wanted to leverage economies of scale. But there are challenges if you limit yourself to a single tower.”

Rogers explained that a single-tower design necessitates a high tower, which presents its own engineering challenges and drives up capital costs. It also can bump up against zoning or airspace restrictions, and can engender more resistance from surrounding communities. Rogers added that larger systems require larger receivers, which in turn get significantly more complex, and therefore expensive and subject to breakage. He added that, historically, people didn’t want to deal with smaller heliostats because they didn’t want to clean and control them. “Our secret sauce is in our software,” he said.

Expansion for the future

In 2009, eSolar demonstrated a 5-megawatt solar thermal project in the desert northeast of Los Angeles, and looked to build larger plants across California. However, as Todd Woody reported in Forbes, the company was unable to secure federal loan guarantees, and the deal fell through.

Bill Gross told Woody that the experience prompted him to seek larger corporate partners, and to focus on licensing their technology. So they teamed up with GE and MetCap, and the first result is the planned integrated facility in Turkey. Greasing the wheels, Turkey provides a subsidy of 10 euro cents per kilowatt-hour for renewables. With natural gas twice as expensive in Turkey as in the U.S., there is even more incentive to decrease the amount burned.

GE is also looking to demonstrate its new FlexEfficiency 50 gas turbine system, which the company hopes will see early adoption in Europe and Asia. A product of ecomagination, the FlexEfficiency 50 is a new single-shaft design that integrates a gas turbine, steam turbine, and generator with digital controls. In the plant, natural gas is burned in a jet engine to drive a generator, and the exhaust gases are used to make steam to turn a steam turbine, which also drives a generator. That integrated Heat Recovery Steam Generator (HRSG) improves performance, facilitates rapid starts of less than 30 minutes, and reduces energy costs.

The 510-megawatt, block-size FlexEfficiency 50 plant is said to have a turnkey design and an expected baseload efficiency of more than 61 percent. It can churn out greater than 50 MW a minute, while maintaining emissions guarantees. GE says the technology saves 12,700 metric tons of CO2 per year and 10 metric tons of NOx per year, compared with prior technologies.

5,000 mirrors the size of big TV sets will focus on a 250-foot tall eSolar tower.

Paul Browning of GE said, “When we look at the long-term future of power generation, we see the importance of integrating natural gas and renewable energy sources in new and innovative ways to provide energy that is cleaner, more cost effective, and more reliable.”

Mirror, mirror on the “tall”

In the combined facility in Turkey, 25,000 mirrors the size of big TV sets will focus on a 250-foot tall eSolar tower. (For comparison’s sake, past solar thermal projects had towers as high as 700 feet.) Steam produced in the boiler will be piped directly to the FlexEfficiency’s steam turbine, to offset the need for natural gas. By taking advantage of that turbine, it eliminates the need for a separate generator. Power from the nearby wind turbines will help run the plant, with excess feeding into the grid.

GE says the Karaman plant will be 69 percent efficient, though future developments could be even better (this ignores the local wind and sun that does not get converted to electricity, under the assumption that these resources are “free”).  Most natural gas plants have an efficiency ranging between 30 and 50 percent.

According to Rogers, adding the eSolar component makes it a “hybrid, almost bolt-on solution.” Looking toward the future, he added, “We can go into combined cycle facilities, and add solar as an already proven technology. You can think of it as a fuel saver; anytime the sun is shining you have the opportunity to burn less gas. When clouds come by you can turn up the gas. Whether the sun is shining or not, you can maintain the same output.”

In April, GE also announced that it would build the United States’ largest solar panel factory, though the location wasn’t revealed. It’s another sign that GE is serious about renewables and serious about competing with the established manufacturers of the Far East.