Too Good To Be True? Carbon Capture 'Game Changer' Raises Hopes And Questions

A potential breakthrough technology is being tested in Houston—a new kind of natural-gas power plant that captures and reuses what normally goes up the smokestack: carbon dioxide, heat, and water.
If it works, NET Power’s natural-gas plant promises no carbon emissions and no water use—it produces water instead—and this is the clincher: it promises to produce electricity at a cost competitive with existing power plants.
But the concept endured another kind of test last week in Chicago: the scrutiny of a roomful of academics, many of whom raised questions about how and whether the plant will work.
“What are the potential challenges and roadblocks for this?" a woman asked NET Power CEO Bill Brown at the University of Chicago on Wednesday. "It sounds almost a little bit too good to be true.”
“You know, this is the problem with us,” Brown replied. “We were this too-good-to-be-true technology. In fact, people wouldn’t return phone calls in the early stages; they would just say, ‘You can’t do this.’ Then when people actually model it—at this point, hundreds of Ph.D. students have modeled this, energy companies have modeled this, they’ve done what is called heat-mass balance models—so yes, I agree with you, too good to be true. Sometimes that’s what every breakthrough starts out as.”
Backed by Exelon, Toshiba and CB&I, the NET Power concept captures the carbon dioxide that traditional plants spew into the atmosphere. It uses that CO2 under pressure, when the gas acquires some of the qualities of a liquid, to capture heat from the plant. This "supercritical" CO2 replaces the water traditional power plants use as a coolant and as steam to drive their turbines.
In NET Power’s plant, some of that CO2, heated to 720º C, returns to the combustion chamber to boost the combustion of more gas. Some CO2 is captured for commercial markets, where it can be used to carbonate soda pop, to decaffeinate coffee and tea, to make building materials, or to enhance oil and gas extraction from fossil-fuel wells.
That last possibility raised more questions in Chicago. If it’s used to enhanced oil and gas recovery, asked the physicist Robert Rosner, a former Argonne director, won’t that result in more carbon emissions elsewhere?
No, Brown replied, because for every carbon atom extracted from the ground as oil or gas, two will be stored underground as compressed CO2. Brown contends there is an opportunity to sequester 1.1 trillion tons of CO2 through this method of enhanced oil recovery (EOR).
“How important is being able to sell the CO2 for EOR to your overall business model?” asked Sam Ori, executive director of the Energy Policy Institute at Chicago, which sponsored Brown’s visit.
“It’s a piece of it,” Brown said. “Our goal is to make this CO2 either sequestrable in the ground” or sequestrable in products.
Economist Michael Greenstone—EPIC’s director—questioned whether Net Power’s concept assumes a certain demand for carbon dioxide.
“Here’s what I’m still struggling with,” Greenstone said. “How much do you guys need to be paid per ton of CO2 to cost competitive with a natural gas combined cycle plant?”
“Zero,” Brown said.
"If you get zero from the gas you could sell into the grid?” Greenstone pressed.
“We could sell into the grid. I wouldn’t say plant numbers 1-29, but plant number 30, we’re there.”
Right now, Brown said, a NET Power plant can compete wherever there’s a price on carbon, such as in Europe, without having to sell any CO2. Where there is no carbon price, he said, the NET Power plant will still become competitive, through economies of scale, after 30 plants have been built.
But the sale of the products it produces—not only CO2 but also water, nitrogen and argon—can make it competitive immediately, he said.
“If we have CO2 at $10 a ton that’s economic for everything.”
CO2 has traditionally sold for $9-$36 per ton, according to the Global CCS Institute, but NET Power plants would presumably alter that number by increasing supply. So the NET Power economics are still on paper. Brown expects the 50 megawatt Houston demonstration plant to prove its mettle this year, and the first 300 MW commercial plant to be running by 2021.
“If it plays out as advertised, it could be an actual game changer,” said energy researcher Jesse Jenkins in a profile of the concept in the MIT Technology Review.
I asked a researcher who has championed renewable energy solutions, Rice University Professor Daniel Cohan, for his view of NET Power. Is he concerned NET Power could lead to more fossil-fuel use and therefore more carbon emissions? I found out that Brown had also visited Cohan’s classroom.
“NET Power is the first carbon capture concept that, if it works as intended, would be a triple win for climate, environment, and cost," Cohan told me in a Twitter message. "Other carbon-capture efforts use huge amounts of energy, so they require more coal mining or natural gas drilling and the costs and environmental damage that comes with it. Net Power claims that they'll be able to generate power from natural gas just as affordable and efficiently as state-of-the-art traditional power plants.
“The question is whether this will work out as hoped. My understanding is that they're not actually going to capture their carbon in this demonstration plant. And it still remains to be seen how costs will scale to larger plants.”
NET Power plants potentially could serve as flexible backup plants for wind and solar as those sources grow, Cohan said, and they could displace coal plants and less efficient natural-gas plants—that is, if they prove as affordable as promised.
So all eyes are on NET Power’s demonstration plant. After Brown’s public appearance at Chicago, I interviewed him for Off the Charts, EPIC’s podcast, for which I serve as host. I asked Brown when he was going to flip the switch on the Houston demonstration plant.
"We’re flipping various switches right now," he said. "We’re in the process of commissioning all this and testing some of the components. It’s like anything new, we’ll be flipping switches for several months. And when we’re comfortable that we’ve gotten to the place where we can do, in effect, a design freeze on the full-scale plant, that’s when we’ll let the world know that we now have enough information that will allow us to build this on a full-scale basis, and we’re going to go out and put something in the ground for 2021."