What if there were an electric generating plant that burned fossil fuels but emitted no carbon dioxide? Is that something the world would be interested in? Yes, we know, CleanTechinca peeps. It would be better if we all made our own renewable energy from solar panels and stored it in batteries installed on our property, but that’s a bit of a Utopian vision at the moment. Before the future gets here in all its glory, a lot of natural gas is going to be consumed to make electricity. Why not burn it in a way that adds no carbon dioxide to the atmosphere?
Impossible, you say? Not really, according to the people behind NET Power, which has just completed a demonstration plant outside Houston. They are testing new technology that uses natural gas to generate electricity but captures 100% of the resulting carbon dioxide. Others have tried the same thing, but the electricity they generate winds up costing more than electricity from a conventional natural gas facility. NET Power says its process is cost-competitive with electricity from a traditional gas-fired plant. “We’ve designed a power plant that is cheaper and cleaner,” Chief Executive Officer Bill Brown tells Bloomberg. “Imagine that, when you have economics driving a solution rather than policy aspirations.”
The NET Power system is very different from a conventional gas-fired generating station. Instead of using steam to power a turbine, NET Power uses pressurized CO2, which increases efficiency while keeping the CO2 contained. Any excess carbon dioxide not needed to operate the plant can be sold to generate some positive cash flow. It is in used for making some plastics, chemicals, and building materials, but it is used primarily for enhanced oil recovery. By injecting it under pressure deep underground, it helps force trapped oil and gas to the surface.
According to Quartz, this is how the NET Power system works:
“In a small turbine, a combustor burns natural gas and pure oxygen—producing only carbon dioxide and water—in a chamber that’s already full of supercritical carbon dioxide at high pressure and temperature. That’s no small feat; it’s like trying to light a match while someone else is doing their best to put it out with an extinguisher. The combustion produces additional carbon dioxide, some water, and lots of heat. This hot, high-pressured mixture is then passed through a gas turbine, where the pressure turns a shaft to generate electricity.
“The slightly cooled mixture exits the turbine, then is separated into parts. The necessary amount of carbon dioxide is compressed to become supercritical again and added back to the initial chamber, keeping a steady amount of the gas circulating through the system. The remaining, pure stream of CO2 can be buried underground. And the (clean) water is dumped. The heat transfer in this process is so efficient that for each unit of energy trapped in natural gas, the Allam cycle produces 0.8 units of electricity (compared to 0.6 units produced in the most advanced natural-gas power plants).”
Bill Brown doesn’t see using the captured carbon dioxide to liberate more fossil fuels as contrary to the company’s mission. “The problem is not to keep it in the ground,” he says. “The problem is to keep it out of the air.” Continuing to use fossil fuels is fine, in other words, as long as they’re only burned in NET Power facilities. Rodney Allam, the British engineer who invented the core technology, sees it as a necessary compromise while renewables get up to speed. “We have to realize that the energy from renewables will only provide a small portion of the total world requirement for energy,” he said. “So unless we solve this problem of emission control and the burning of fossil fuels, we won’t have a sustainable future.”
The pilot plant will start out making a modest 25 megawatts of electricity and slowly ramp up to 50 megawatts. If all goes according to plan, it could be generating 300 megawatts of zero carbon power within a few years. Think of the NET Power plan like hybrid or plug-in hybrid vehicles. True, they are not as kind to the Earth and its atmosphere as battery electrics, but if they result in significantly fewer carbon emissions from the transportation sector, that’s a net gain for us all. Despite the extraordinary progress made by renewables in recent years, 80% of the world’s electricity still comes from non-renewable sources, so NET Power could represent a big step forward.
Now if someone could figure out how to get natural gas out of the ground without polluting groundwater and putting all those nasty methane emissions into the atmosphere, the NET Power system would really be a reason to cheer.
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