The New Gas Revolution That Could Make Renewable Energy Obsolete

  • Date: 31/07/19
  • James Conca, Forbes

If the Net Zero power plant performs as expected this is a real game changer for natural gas. Since the United States is sitting on more natural gas than any country in the world, and it’s getting cheaper to get it out of the ground, this is no small game to change.

An actual game changing technology is being demonstrated as we sit in our air-conditioned abodes reading this. And it is being demonstrated by North Carolina–based Net Power at a new plant in La Porte, Texas.

NET Power’s 50 MWth Demonstration Plant in La Porte, Texas.  NET POWER

The process involves burning fossil fuel with oxygen instead of air to generate electricity without emitting any carbon dioxide (CO2). Not using air also avoids generating NOx, the main atmospheric and health contaminant emitted from gas plants.

Included in a group of technologies known as carbon capture and sequestration (CCS), zero-emission fossil fuel plants have been a dream never realized in practice, as it always seems to cost a lot, adding between 5¢ and 10¢ per kWh. This is probably because most attempts just add on another step after the traditional electricity generation steps, almost as an afterthought.

Some fossil fuel plants have tried, and failed, the most famous one recently being the $7.5 billion coal power plant in Kemper, Mississippi.

But this new technology completely changes the steps and the approach from the ground up. It is based on the Allam Cycle, a new, high-pressure, oxy-fuel, supercritical CO2 cycle that generates low-cost electricity from fossil fuels while producing near-zero air emissions.

All CO2 that is generated by the cycle is produced as a high-pressure, pipeline-ready by-product for use in enhanced oil recovery and industrial processes, or that can be sequestered underground in tight geologic formations where it will not get out to the atmosphere for millions of years.

The Allam Cycle also means the power plant is a lot smaller and can be sited in more areas than older plants can.

The Allam Cycle of Net Power’s new zero-emission natural gas plant. NET POWER

This 50 MW Texas plant is demonstrating that the technology works, especially to investors. So the project has some heavy hitters as partners – Exelon Generation will operate the plant, the infrastructure firm CB&I will provide engineering and construction, 8 Rivers Capital, Net Power’s parent will provide continuing technology development, and Toshiba will develop the key components, particularly its new CO2-turbine.

Most power plants rely on thermal power cycles for energy production. These systems create heat by burning fossil fuel using the oxygen in air. In coal plants, this takes place in a large boiler, where coal is burned and water is boiled to create high pressure steam.  This high-pressure steam then expands through a steam turbine, creating power.

In combined cycle gas turbine power plants, natural gas or coal syngas is burned in a combustor with compressed air. The heated gases then expand and drive a gas turbine. The turbine exhaust is extremely hot, so it is subsequently used to boil water to create high pressure steam and drive a steam turbine, thereby combining cycles. In both systems, aqueous steam is essential to the process as a working fluid.

Not so in an Allum Cycle plant like Net Power’s. At their Texas demonstration plant, the natural gas is burned with a mixture of hot CO2 and oxygen, known as oxy-combustion. The resulting working fluid is a mix of high-pressure CO2 and water, which is subsequently expanded through a turbine and then cooled in a heat exchanger (a recuperator).

This is key. The turbine is not turned with steam, but with CO2. 

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