How it Works: Emission-Free Natural Gas Power

Natural gas generators make up the largest share of overall power generation capacity in the United States. What if we could create power from this natural fuel source in a way that’s more carbon-friendly? One Oxy Low Carbon Ventures partner initiative is making this vision a reality.

Power generation is a major contributor to U.S. carbon dioxide emissions. And more than half of our current emissions come from natural gas. In a natural gas power plant, fuel is burned in hot, compressed air to spin the blades of a turbine. The turbine’s shaft turns a generator which produces electricity. In a combined-cycle power plant, the turbine’s exhaust is also captured to create steam that runs an additional turbine within the system.

There are approximately 1,850 natural gas plants in the United States. These facilities emit around 117 pounds of CO2 per million British thermal units (Btus) of energy. As far as fossil fuels go, this is the cleanest fuel source. Burning anthracite (a type of coal), for example, creates an average of 228.6 pounds of CO2 per million Btus. Still, meeting CO2 reduction goals will mean rethinking how we approach conventional power generation facilities.

Enter the Allam-Fetvedt Cycle

Oxy Low Carbon Ventures partner NET Power has developed an approach that can take a natural gas facility’s emissions from 117 pounds per million Btus to zero. That’s right: zero. This innovation was made possible by something called the Allam-Fetvedt Cycle, or just the “Allam Cycle” for short.

This new type of power cycle pushes supercritical CO2, rather than steam or air, through the unit’s turbine in a way that creates a closed-loop system. Supercritical liquids are kept at a pressure and temperature that changes the physical properties of the fluid. In the case of CO2, its supercritical state has the density of a liquid but flows like a gas. This system is designed to have absolutely no CO2 emissions.

Unlike a conventional gas turbine, the Allam Cycle also burns pure oxygen rather than air. This is normally unfeasibly expensive, since oxygen costs a lot to make. But since systems using the Allam Cycle recuperate most of their CO2 into the combustor, oxygen requirements are actually pretty low. These facilities require 80x less acreage than conventional natural gas power generation. When you put it all together you have an efficient, reliable power cycle with zero emissions.

Renewable energy sources, such as solar and wind, are inherently intermittent. This means no power is generated at night, or when the wind does not blow. NET Power can provide reliable, emissions-free, and efficient power generation 24 hours a day, 7 days a week, 365 days a year. It also requires much less land —by a factor of over 200!

Products, Not Pollution

While this system emits no CO2, it does create contained CO2 that’s ready for transport or usage. Rather than being released to the atmosphere as a greenhouse gas, this CO2 can be sequestered or used as an industrial feedstock. CO2 can be used to make all kinds of things including carbon fiber, building materials, plastics, concrete, coatings, fertilizer, methanol, graphene and more. It can even be used in a Carbon Neutral Production process to produce carbon-neutral oil and gas.

And this isn’t a theory. NET Power’s approach to carbon-neutral power generation is up and running with a 50MW demo plant that’s currently operating in La Porte, Texas. NET Power’s vision and innovation brings practical new potential to energy and industrial companies as they explore ways to balance operational and financial imperatives with CO2 emission reduction goals. And when paired with concepts such as our new Clean Campus, NET Power plants have the potential to help businesses transition to carbon neutrality without operational or financial disruption.

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