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Record setting small-scale solid oxide fuel cell could power neighborhoods

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May 31, 2012

The highly efficient, small-scale SOFC system developed at PNNL features PNNL-developed mi...

The highly efficient, small-scale SOFC system developed at PNNL features PNNL-developed microchannel technology and two unusual processes, called external steam reforming and fuel recycling

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A new, small-scale solid oxide fuel cell (SOFC) system developed at the Department of Energy’s Pacific Northwest National Laboratory (DoE PNNL) could be used for household and neighborhood power generation. Fueled by methane, the system achieves an efficiency of up to 57 percent, improving on the 30 to 50 percent efficiencies seen previously in SOFC systems of similar size. The PNNL researchers say the pilot system they have built generates enough electricity to power the average American home, and can be scaled up to provide power for 50 to 250 homes.

Solid Oxide Fuel Cells

Like batteries, fuel cells use anodes, cathodes and electrolytes to produce electricity. But unlike most batteries, fuel cells can continuously produce electricity if provided with a constant fuel supply. Fuel cells are characterized by their electrolyte material, which in the case of SOFCs is a solid oxide or ceramic. Ceramic materials also form the anode and cathode which, along with the electrolyte, form three layers.

Air is pumped up against the cathode, which forms the outer layer, with oxygen from the air becoming a negatively charged ion where the cathode and the inner electrolyte layer meet. The negatively charged oxygen ion then moves through the electrolyte to reach the final anode layer where it reacts with a fuel to create electricity, as well as steam and carbon dioxide byproducts. SOFCs can run on different fuels, including natural gas, biogas, hydrogen, but the PNNL team chose methane - the primary component of natural gas - to fuel its new SOFC.

Because they are more efficient than other methods of electricity generation, including coal power plants, SOFCs consume less fuel and create less pollution to generate the same amount of electricity. Small-scale SOFCs also have the advantage of being able to be placed closer to where the electricity generated is consumed, reducing the amount of power that is lost when sent through transmission lines.

"Solid oxide fuels cells are a promising technology for providing clean, efficient energy. But, until now, most people have focused on larger systems that produce 1 megawatt of power or more and can replace traditional power plants," said Vincent Sprenkle, chief engineer of PNNL's solid oxide fuel cell development program. "However, this research shows that smaller solid oxide fuel cells that generate between 1 and 100 kilowatts of power are a viable option for highly efficient, localized power generation."

With the aim of designing a small system that was more than 50 percent efficient and could also be scaled up to produce electricity for neighborhoods, the PNNL team combined external steam reforming and fuel recycling with microchannel technology.

Steam reforming

Steam reforming involves mixing steam with the fuel so that they react to create carbon monoxide and hydrogen, which in turn reacts with oxygen at the fuel cell’s anode. Because this process requires heat that can cause uneven temperatures on the ceramic layers and lead to weakening and breakage of the fuel cell, the PNNL team used a heat exchanger to allow the initial reactions between steam and the fuel to be completed outside of the fuel cell in what is known as external steam reforming.

Heat exchangers consists of a wall made of a conductive material that separates the two gases. The hot exhaust that is expelled as a byproduct of the reaction inside the fuel cell is located on one side, while a cooler gas that is heading toward the fuel cell is located on the other. Heat from the hot gas moves through the wall to warm the incoming gas to temperatures needed for the reaction to take place inside the fuel cell.

Microchannel heat exchangers

But instead of having just one wall separating the two gases, the PNNL researchers created multiple walls using a series of tiny looping channels, narrower than a paperclip. These microchannel heat exchangers increase the surface area to allow more heat to be transferred, thereby increasing the efficiency of the system. The microchannel heat exchanger was also designed so that the gas moves through the looping channels with very little additional pressure.

Microchannels narrower than a paper clip are etched onto the heat exchanger’s shim, which ...

Steam Recycling

The PNNL system also recycles the exhaust coming from the anode, consisting of steam and heat byproducts, to maintain the steam reforming process. Not only does this recycling negate the need for an electrical device to heat water and create steam, it also means that the system is able to use up some of leftover fuel that wasn’t consumed the first time around.

The combination of external steam reforming and steam recycling and use of microchannel heat exchangers allow the system to use as little energy as possible with the end result being more net electricity production. In lab tests, the team say net efficiencies ranging from 48.2 percent at 2.2 kW, up to 56.6 percent at 1.7 kW. With a few more adjustments, the team believes they can raise the system’s efficiency to 60 percent.

With the average American home consuming roughly 2 kW or electricity, the pilot system could be used for household power generation. However, they also designed it so it could be scaled up to produce between 100 and 150 kW, which could provide enough electricity to power 50 to 100 homes. The PNNL team hope to see their research translate into just such a system that could be used by individual households or utilities.

The PNNL team’s small-scale SOFC is detailed in a paper published in the Journal of Power Sources.

Source: PNNL

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag.   All articles by Darren Quick
17 Comments

Has anyone ever heard of the BlueGen from the Australian based company Ceramic Fuel Cells Limited? They have a commercially available 2kW SOFC system. Boosting efficiencies over 60% electrical and >90% total.

I think that there should be an article about their technology, they are way ahead of other technologies....

Matthijs G
1st June, 2012 @ 12:10 am PDT

Matthijs G - u stole my thunder lol Blue Gen developed by CSIRO and being commercialised through a "retail" arm, Ceramic Fuel Cells Limited. http://www.cfcl.com.au/BlueGen/ This Australian FC is well tested through Europe and is close to upscaling.

RaVOLT
1st June, 2012 @ 12:34 am PDT

This looks really interesting. The only problem is that I'm currently paying around 1400 USD per year for household electricity. It will need to become a lot more efficient before it's an economic proposition. (Being self sustained an greener does sound good though.)

Francois Retief
1st June, 2012 @ 03:44 am PDT

That is definately one of the ways to go for alternative energy. They should just have mentioned the word "sewage" somewhere in the article as to indicate where the methane gas can possibly come from.

What is the life expectancy of such a system?

Riaanh
1st June, 2012 @ 04:41 am PDT

Why scale up and concentrate on home use... Leave it this size (or scale down) and put it in EV's instead of batteries. Turn Dairy Farms into gas stations.

GvillaThrilla
1st June, 2012 @ 06:26 am PDT

How big is a domestic unit? What does the article mean when it says that Americans consume 2kW of electricity? This is surely incorrect? How much Methane is consumed to produce 1kWh of electricity?

windykites1
1st June, 2012 @ 10:09 am PDT

As Riaanh asked what is the life expectancy of such a system plus how much does it cost compared to small scale steam, ICE or gas-turbine electrical generation. Both full life-cycle, and up front expense. It doesn't matter if it will cost less overall if you can not buy it in the first place.

How are they going to dispose of the carbon monoxide?

Slowburn
1st June, 2012 @ 12:22 pm PDT

I have been following the BlueGen as well. What I believe most important about this concept is it is a move away from centrally generated power,which if the stories I've read are accurate,could doom our high-tech civilization in the event of a bad solar geomagnetic storm ( see: http://spectrum.ieee.org/energy/the-smarter-grid/a-perfect-storm-of-planetary-proportions/0 ),which has occurred already on a small scale,or the efforts of terrorists.

michael_dowling
1st June, 2012 @ 02:37 pm PDT

like many articles the information stops short of giving cost information : what is the projected price of these units ? what is projected cost per kw ?

how do they compare to the Australian units ?

Vintech
1st June, 2012 @ 03:07 pm PDT

Didn't see any projected cost numbers. How much /W and /kwh?

Brian Hall
1st June, 2012 @ 04:27 pm PDT

To: Riaanh: Fuel cells are very sensitive to "poisons" such as sulphur compounds. Any "sewer gas" would have to be cleaned up a lot before use in the fuel cell.

GeoffG
1st June, 2012 @ 04:35 pm PDT

re; GeoffG

Methane from any source needs to be cleaned up for this.

Slowburn
1st June, 2012 @ 11:27 pm PDT

Practical information is lacking, such as expected life without service or replacement, cost of ownership or lease program, estimated fuel cost per KWH to compair to 'grid' based alternatives, etc...

It seems they still have to be grid based at least for incoming fuel. The solar/battery/inverter technology is still unbeatable for off grid applications in temperate climes, and will be until hydrogen collection from water becomes cheaper and more efficient.

John Hemingway Parkes
3rd June, 2012 @ 10:34 am PDT

The BlueGen is $40,000+ before installation and unless you have a methane digester and enough livestock to supply it you are still paying for fuel.

40K buys you a pretty serious solar set up, so for the moment it is a better option.

Reason
3rd June, 2012 @ 10:59 pm PDT

The beauty of the methane fired SOFC's is that they are arriving at the same time that the Coal Seam Gas technologies are being improved including green fracking. Imagine on every city block there was a CSG bore hole supplying methane to each SOFC equipped building in that block.

Lot's of cheap power. Way to go for economic recovery!

http://smarteconomy.typepad.com/smart_economy/2009/12/a-green-alternative-to-chemicalbased-hydraulic-fracturing-or-fracking-for-shale-gas-drillingcavitati.html

bernardpalmer
5th June, 2012 @ 05:21 am PDT

Bernard ... "green fracking"? Where in the world did you hear of that! I've never seen anything that isn't dirty and dangerous. "every city block there was a CSG bore hole supplying methane" and radon "to each SOFC equipped building in that block."

This SOFC apparently also produces "carbon dioxide byproducts" - that doesn't sound so clean!

Harriet Russell
5th June, 2012 @ 04:43 pm PDT

what is the weight of the SOFC .... i wonder, because 2kw makes for a pretty good electric scooter... i figure if they say its just for home use then it's pretty heavy! like more than 10 20 kg

Antony Stewart
7th June, 2012 @ 04:28 am PDT
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