Comments on: Supercritical Carbon Dioxide Turbine

By: Philip Ngai

Philip Ngai — Sun, 17 Apr 2016 20:50:30 +0000

A GE H series gas turbine is a component of a combined-cycle application, with a gas turbine and a separate steam turbine. GE makes separate Steam turbine families like ST-D600, D400, D200 etc. The Supercritical Carbon Dioxide Turbine in this article would replace the steam turbine. A combined-cycle plant with a GE H series gas turbine driving a Supercritical Carbon Dioxide Turbine would likely be over 61% efficient.

https://powergen.gepower.com/products/steam-turbines.html

By: Scipio Americanus

Scipio Americanus — Fri, 15 Apr 2016 12:52:47 +0000

I think responsiveness is the big plus here, combined maybe with the simplicity of a single-loop system versus multiple. Less plumbing is usually a good thing, even if it’s more challenging plumbing to get right the first time.

By: David Foster

David Foster — Fri, 15 Apr 2016 12:16:50 +0000

"Steam-based systems are typically in the mid-40 percent (efficiency) range." This is true, but plants that aim for maximum efficiency aren't pure steam; they are combined-cycle, with a gas turbine and a steam turbine, which is fed by waste heat from the gas turbine. GE's own "H" series combined-cycle turbines are quoted at efficiencies of 61%. So presumably the CO2 turbine is intended for situations where a first-stage gas turbine is infeasible, or the physical size of a combined-cycle system would be excessive. Maybe faster start-up time as well.

By: Mikeski

Mikeski — Thu, 14 Apr 2016 19:20:08 +0000

Apparent typo, now fixed at the link: “scale it to 33 megawatts”, not just “watts”.

(Though I could see someone trying to make a system requiring 700C CO2 that only dumps out 33 watts, just for the geek cred.)

By: Bob Sykes

Bob Sykes — Wed, 13 Apr 2016 11:11:59 +0000

Thanks. I should have read the link.

By: Scipio Americanus

Scipio Americanus — Tue, 12 Apr 2016 21:41:09 +0000

Depending on how I’m interpreting your statement, Bob, that might not be a sensible question. In a gas turbine power-plant the turbine is the power source itself: NatGas is burned, turning a turbine which is coupled to a generator. The system is a Brayton cycle.

The system above isn’t a power source like the turbine in the above-mentioned power-plant, but as a component in a Rankine cycle system where an external heat source is used to move a working fluid (in this case super-critical CO2). Examples are coal or nuclear power-plants where the energy source merely provides heat. Usually that heat generates steam that runs a turbine. The turbine spins a generator just like in the NatGas plant.

In modern power-plants, Rankine and Brayton cycles are roughly similar in efficiency, and have interlocking strengths and weaknesses.

By: Bob Sykes

Bob Sykes — Tue, 12 Apr 2016 21:27:30 +0000

How does this compare to natural gas fueled turbines? I bet the cost per kWh is higher.