Next-gen power generation

Two power plant designs, one nuclear the other gas-fired, offer a tantalizing look at a safe, emissions-free future.

The “all of the above” strategy—maybe you’ve heard of it. That’s the approach that acknowledges that every type of power generation has something to offer. You might also say it acknowledges that every type of power generation has something wrong with it.

Coal spews pollutants like mercury into the atmosphere. Nuclear is prohibitively expensive to build. Hydro disrupts fish migration. Natural gas produces CO2, albeit much less than coal. Wind and solar have intermittency issues.

But what would you say about a nuclear plant that was cost-competitive with natural gas and also dramatically reduced radioactive waste? Or a gas-fired, even coal-fired, power plant that produced zero emissions… of anything?

Sound too good to be true? Maybe, but that’s precisely what two new power generation schemes offer.

Cheap, safe and clean

The former was recently described in an article published in the MIT Technology Review. The reactor, which as yet exists only in computer simulations, uses thorium-based fuel and helium as a coolant instead of water and operates at higher temperatures.

This in turn allows it—again, in theory—to achieve greater than 50 percent efficiency. Today’s reactors, by contrast, only get to around 32 percent on average.

General Atomics, which is now looking for funding from the US Department of Energy to develop the design, plans to build smaller plants that the company says will cut the cost of the produced electricity by 40 percent, though that claim has raised some eyebrows among nuclear experts.

The company also touts the plant’s superior safety. First, the company says its reaction process produces up to 80 percent less nuclear waste than conventional plants. And in the event of a power failure (see Fukushima), the reactor would be capable of shutting down and cooling off entirely on its own. This thanks to the use of advanced ceramics that won’t melt even in the presence of extremely high temperatures.

This is all very exciting but there is another new power plant in the making that is equally intriguing. And it might even see widespread adoption in our lifetime.

But wait there’s more

In June of 2012, Toshiba announced it was working as part of a consortium on a revolutionary new power plant design that makes CO2 part of the process (and a saleable output), rather than a waste product that has to be separated from exhaust gasses at considerable expense.

Fast forward to July 2013 and the group announced it was in final testing of the critical combustor component and expects a demonstration plant to be up and running in 2015. A full-scale plant is slated for 2017. (Modern Power Systems has a great breakdown of all the technical and economic particulars if you’re interested in that sort of thing.)

The design uses CO2 as a working fluid in a closed loop similar to today’s steam turbines, and burns the input fuel—natural gas or even gasified coal—in a pure oxygen environment. The result is heat, more CO2, and water.  That’s it.

The super-heated CO2 coming out of the combustor drives a turbine before cooling and returning to the combustor. The excess CO2 is separated out along with the water. The excess CO2 is of very high quality and, importantly, emerges at high pressure suitable for immediate transfer to a pipeline for use in enhanced oil recovery or other applications.

Toshiba estimates the efficiency of the gas version of its design to come in at 58.9 percent and the coal version at 51.4 percent.  That’s far better than today’s most efficient plants of either type, which have no CO2 capture whatsoever.

It’s worth noting that these figures are based on existing technology for the air separator (which supplies the oxygen to the combustor) and compressor units that keep the CO2 at high pressure. The “gross efficiency” of the plant (i.e., with the “parasitic load” of the air separator, compressors and other plant equipment) is pegged at 82.7 percent and 74.9 percent respectively for the gas and coal flavors. That means that there is considerable room to run as the efficiency of the supporting equipment improves.

The bottom line is that Toshiba thinks its new power plant will produce electricity at a cost somewhere around 40 percent less than today’s most efficient fossil fuel plants while taking the problem (CO2) and making it part of the solution.

“Now how much would you pay?!”

The question that comes at the end of classic TV infomercials is appropriate here because as exciting as the Toshiba and General Atomics plants are, they will eventually have to compete in real-world power markets.

Admittedly, the thorium reactor is probably decades away from commercial viability whereas the CO2-driven turbine is being built now—with commercially available components. Still, both technologies represent a quantum shift in power generation. Each has the potential to radically improve the sustainability of our energy supply, perhaps more than any single advance since Edison flipped the switch at Pearl Street Station.

Image credit: bagalute via a creative commons license on Flickr