First the latest news from Guinness World Records: The world’s most efficient combined-cycle power plant started producing electricity near the village of Bouchain in northern France today. The plant’s beating heart – an advanced GE gas turbine – can convert more than 62 percent of fuel energy into electricity. For the power-generation crowd, that’s like Neil Armstrong and Buzz Aldrin landing on the moon or Sir Roger Bannister breaking through the 4-minute-mile barrier.
But you should care, too. The turbine – called 9HA.01 in GE nomenclature – weighs as much as a fully loaded Boeing 747 and can generate the same amount of power needed to supply more than 680,000 French homes. It can go from zero to full throttle in less than half an hour, enabling the plant operator, EDF Energy, to quickly respond to changing demand and supply customers with power from intermittent sources of renewable energy such as wind and the sun.
It’s also very clean. GE calculated that when the turbine burns 3.3 tons of natural gas mixed with air – equivalent to 23 tanker trucks – out comes just 6.3 fluid ounces of pollution, a volume slightly larger than a half-can of soda.
That’s in part because the turbine operates at temperatures approaching the melting point of steel. GE engineers modeled the heat flows inside on a powerful supercomputer and used designs, materials and special thermal barrier coatings developed for jet engines to handle the temperature. The hot air comes out at a speed approaching a Category 5 hurricane – so fast it could fill the Goodyear Blimp in 10 seconds.
Without the thermal barrier coatings, the turbine “was basically like making a fireplace from wax,” says GE’s John Lammas, Chief Technology Officer for GE Power and Vice President of Gas Power Technology. Lammas is an English jet engine designer who helped create the new gas turbine. GE Reports sat down with Lammas to talk about the turbine. Here’s an edited version of their conversation.
GE Reports: Guinness World Records said that Bouchain is the world’s most efficient combined-cycle power plant. What does that mean?
John Lammas: It means that we use natural gas to generate electricity inside an ultra-efficient gas turbine and then capture the heat it produces, use it to boil water and make even more power inside a steam turbine.
GE Reports: What exactly is the world record?
John Lammas: The exact efficiency we measured was 62.22 percent. No one can go higher than that. The previous record holder came in at 61.5 percent using a non-GE gas turbine.
GER: Why is it meaningful?
JL: It can save you a lot of money. We calculated that a 1,000-megawatt power plant using a pair of HA turbines could save $50 million on fuel over 10 years by raising efficiency by 1 percent.
It generally takes about a decade of development to increase efficiency by 1 percent. It took us only 36 months to develop the HA turbine and about six years in total to get to where we are today with the Bouchain plant, and in this time, we went from less then 60 percent to more than 62 percent in efficiency. That’s just tremendous. We are already testing technologies that can get us to 65 percent.
GER: I want to hear about that, but first tell me about the Bouchain machine.
JL: It’s a combination of things. We are running at higher temperatures. We use advanced materials, better thermal barriers coatings and also more sophisticated cooling technology. The turbine also has incredible aerodynamics because of the curved shape of the blades, the aerofoils.
GER: You started out at GE as an aviation engineer. Did your background come in handy?
JL: Absolutely. The team that worked on the aerodynamics actually also works for GE Aviation. You hear the CEO [Jeff Immelt] talk about the GE Store, the sharing of know-how by businesses inside the company. This is a perfect example. We also borrowed compressor technology from GE Oil & Gas. Without them, we wouldn’t be able to move so fast. Remember, we built this machine in just three years.
GER: You also came from GE Aviation.
JL: Yes, I spent 20 years working for the business. While I was there, I was working on the GE90 jet engine, which is still the most powerful jet engine ever built. It powers many Boeing 777 jets and it’s also in Guinness World Records. I guess I’ve started a trend. [The GE90 also used to be the world’s largest engine, but GE Aviation just started testing the GE9X, which is larger and has the same diameter as Boeing 737’s fuselage.]
GER: After Bouchain, GE should send you to yet another business to complete a hat trick. The world’s most powerful locomotive may be in your wheelhouse, too. Still, what is it that makes the HA gas turbine so efficient?
JL: It’s basically how we manage the Brayton cycle. [In the 19th century, American engineer George Brayton used it to describe a heat engine working under constant pressure.] Like I said before, we use materials and designs that allow us to go to temperatures as high as 2,800 degrees Fahrenheit – close to the melting point of steel – and stay there for a long time. Up there, the Brayton cycle allows us to generate a lot of energy efficiently.
GER: This sounds pretty extreme.
JL: Yes, it does. It’s basically like running a jet engine at takeoff power during the entire flight. It presents a lot of engineering challenges tied to heat management.
GER: Tell us about it.
JL: It was basically like making a fireplace from wax. We use sophisticating cooling tunnels inside the hot section of the turbine to bleed in cool air and protect the blades. The cooling air is the reason they don’t melt. But more cooling air also means lower efficiency. That’s why we covered the components inside with special thermal barrier coatings. They slow the transfer the heat through the parts and allow us to minimize the amount of cooling air we have to use to achieve the same temperatures.
GER: What’s next for the turbine?
JL: We already started testing technologies that can help us reach 65 percent efficiency. We’ve developed a material called ceramic matrix composites (CMCs) that’s very light but also tough and heat resistant. GE Aviation is already using it inside jet engines and they built plant for mass-production of parts from CMCs. Our components are much larger, and we want to learn from them.
We are also using 3D printing to make more efficient cooling paths inside blades that we couldn’t produce before. Both CMCs and 3D printed parts will allow us to increase the firing temperature of the turbines. We also keep improving the aerodynamics and are looking at higher pressures and temperatures in the heat recovery part of the steam generator in the steam turbine to capture more of the gas turbine’s exhaust energy. Finally, we are using some of the world’s most powerful supercomputers to model the heat flows inside the turbines and operate the turbine in unsteady conditions. This will really allow us to take the next machine to the limits.