GE’s key to clean power: natural gas


General Electric (s GE) is a major wind turbine maker and has announced big plans in the past year to tackle the solar market. But it may be the company’s strategy to expand its natural gas power plant equipment business that could be a really significant driver of clean power.

Earlier this week, GE announced a buyer, MetCap Energy Investments, for a natural gas power plant designed to integrate solar energy from eSolar into its production. The hybrid approach saves natural gas use while gaining the emission-reduction benefits of using a renewable source. The design represents the beginning of GE’s long-term plan to modify its power plant designs to use an increasing amount of renewable fuels to generate electricity.

GE is already a giant in the fossil fuel power plant business, so it can use its resources and large customer base to promote these hybrid power plants. This hybrid power plant strategy could be even more effective in promoting renewable electricity generation than any plan to sell stand-alone solar or wind farm equipment.

“When we think longer term, sort of 2050- ish, we really can see a future when the fuel we are using in combined cycle power plants is predominantly renewable,” said Paul Browning, the CEO of thermal products at GE Energy, during a press conference in Italy this week.

Browning was referring to the use of eSolar’s concentrating solar thermal technology, which uses a field of mirrors to beam sunlight onto a tower where a water tank sits. The concentrated sunlight heats up the water to hundreds of degrees Celsius and generates steam, which is then piped to run a turbine and generator to produce electricity. GE is pairing this technology with the new FlexEfficiency 50 combined cycle power plant design that it unveiled two weeks ago. The company is investing in eSolar and licensing eSolar’s technology.

The pairing makes sense, because both solar and natural gas power plants rely on steam turbines and generators to produce electricity. A stand-alone combined cycle power plant feeds natural gas to the gas turbine to generate electricity, a process that produces heat as a byproduct. This heat would just be wasted in a simple cycle power plant that uses only a gas turbine.

But in a combined cycle power plant, heat is captured to produce steam, which then goes to a steam turbine–generator to produce even more electricity. Combined cycle power plants are therefore even more efficient, because they produce more electricity with the same amount of natural gas.

GE isn’t only interested in solar steam production. The company is looking at how it can use eSolar’s technology to produce compressed air at high temperatures, Browning said.

“We can imagine a future where we use [eSolar’s] high-temperature capability to produce high-temperature compressed air, which then goes to the combustor of our gas turbine rather than our steam turbine,” Browning said. “If we can do that, then we can change the game in terms of renewable content in a combined cycle power plan. There are many other ways we can look at this new capability.”

For now, GE is marketing the solar steam equipment along with FlexEfficiency 50. MetCap’s project will install a 530 MW plant in Turkey that includes 50 MW of solar and 22 MW of wind (using GE’s wind turbines). FlexEfficiency 50 by itself can convert 61 percent of the energy in natural gas into electricity. Adding solar and wind will push the efficiency up to 69 percent for the MetCap project and a few percentage points more in other locations, Browning said. The MetCap project will be built at an elevation of about 3,600 feet, and that elevation can cause the natural gas turbine to lose a little efficiency, Browning said.

The plant will cost €400 million, said Celal Metin, MetCap’s chairman, during the press conference. Adding solar will cost more power, of course, but doing so will reduce the use of natural gas. Those fuel savings are attractive to those who expect the price for natural gas, which is a finite resource, to go up in the long run.

Mixing solar and fossil fuel generation isn’t a new concept, but the solar energy component has been added years after the fossil fuel power plants have been operating. FPL erected a 75 MW solar energy plant next to its natural gas power plant in Florida last year.

Photo courtesy of GE



I like this idea, but does it make economic sense? One of the challenges with natural gas combined cycle plants is because they require so much more capital equipment than a traditional direct fired plant (coal or nat gas). Natural gas prices have to be sufficiently high to be economically interesting to invest in that capacity over the conventional types (which is why the nat gas lobby has no real legs and why Jim Cramer’s please go unheard – coal is cheaper than nat gas on a $/BTU basis so why use it for conventional plants let alone build expensive new ones?). How would also adding CSP to that equation make the power cheaper/easier? I’m glad GE’s continuing to show innovations. This is something that they need to make work.

Ucilia Wang

I’m sure you know that you can’t just look at the current price of coal v. natural gas to decide whether a hybrid power plant makes sense. A power plant is meant to operate for decades, so you have to take that into account when you calculate the long-term costs (equipment, construction, operation and maintenance). There is a global effort to tighten emissions rules. Yes, it’s slow going, but if you are a power company, you have to look down the road and decide whether building more coal-fired power plants will actually cost you more money in the long run because you’ll have to add a bunch of technologies to cut emissions and comply with government regulations. Complying with government rules takes a lot of money. Adding solar may or may not lead to cheaper power — there are the fuel-saving and lower-emission benefits. A power plant owner will have to come up with their own values for those two items and decide if it’s all worth it.

Ucilia Wang

I should add that renewable energy gets government subsidies in North America, Europe and Asia. So they cut a good chunk out of the overall costs.

Samer Zureikat

The challenge of using CSP to generate high-temperature compressed air for use in a gas turbine has more to do with the receiver than the heliostats. eSolar did not design a receiver and only attempted to build a better heliostat field. I’m not sure how GE’s eSolar deal will help them move their gas turbine technology in the direction stated.

Ucilia Wang

You need to achieve high temperatures, and heliostats play a big role — how the mirrors focus, tilt and track the sun. Parabolic trough, for example, cannot achieve the same high temperatures because the shape of the parabolic mirrors yields a lower concentration ratio.

Samer Zureikat

Exactly, Ucilia. There are no commercial receivers today that can withstand the high temperatures that can be achieved through point concentration using heliostats. GE would be better off investing in receiver R&D than eSolar’s heliostat business.

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