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U. Maryland and Redox Power partnering to commercialize low-temperature solid oxide fuel cells for distributed generation and transportation

Redox Power’s 25 kW “Cube” sitting outside a conference room. Click to enlarge.

University of Maryland researchers have partnered with Redox Power Systems LLC to commercialize low-temperature solid oxide fuel cell (LT-SOFC) technology for distributed generation—and ultimately transportation—applications at about one-tenth the cost and one-tenth the size of current commercial fuel cell systems.

The fuel cells, based upon patented technology developed by professor Eric Wachsman, director of the University of Maryland Energy Research Center (UMERC) in the A. James Clark School of Engineering, are the foundation of a system being commercialized by Redox that provides safe, efficient, reliable, uninterrupted power, on–site and optionally off the grid, at a price competitive with current energy sources.

Proton exchange membrane fuel cells (PEMFCs) require hydrogen fueling, because they are based on proton conducting electrolytes. However, solid oxide fuel cells (SOFCs) can oxidize any fuel, because the electrolyte transports an oxygen ion, Wachsman noted in a 2011 paper in Science exploring LT-SOFCs.

An SOFC has three major components: two porous electrodes (cathode and anode) separated by a solid oxygen ion (O2–) conducting electrolyte. At the cathode, oxygen is reduced and the resulting O2– ions are transported through the electrolyte lattice to the anode where they react with gaseous fuel, yielding heat, H2O, and (in the case of hydrocarbon fuels) CO2, and releasing electrons to the external circuit.

Among the technologies available to convert hydrocarbon-based resources (which include not only fossil fuels but also, potentially, biomass and municipal solid waste) to electricity, SOFCs are unique in their potential efficiency. For stand-alone applications, SOFC chemical to electrical efficiency is 45 to 65%, based on the lower heating value (LHV) of the fuel, which is twice that of an internal combustion (IC) engine’s ability to convert chemical energy to mechanical work. In a combined cycle, there are numerous combined heat and power (CHP) applications using SOFC systems, which have the potential to achieve efficiencies of >85% LHV.

Unfortunately, government policy, the popular press, and many scientific publications have focused on fuel cells as part of a broader hydrogen economy, thereby relegating fuel cells to a “future energy” solution due to the need for a required overhaul of our current hydrocarbon-fueling infrastructure. Although this may be true for PEMFCs, SOFCs have the advantage of fuel flexibility that allows them to be used on our existing hydrocarbon fuel infrastructure while simultaneously providing efficiency gains (and corresponding CO2 emission reductions).

—Wachsman and Lee (2011)

University of Maryland Professor Eric Wachsman describes how solid oxide fuel cells work.

The PowerSERG 2-80, also called “The Cube”, connects to a natural gas line and electrochemically converts methane to electricity. The initial breakthrough in the PowerSERG is in the fuel cells, which Wachsman has improved to produce more power at a lower temperature. More power means fewer cells to do the work of larger power generation systems, enabling the devices to be much smaller. Also, lower operating temperatures allow for the use of conventional materials in The Cube, driving costs down significantly.

Conventional solid oxide fuel cells operate as high as 950 °C to run effectively. At this high temperature, the system can’t be easily turned on and off, performance degrades, and the balance of the system requires expensive, high-temperature alloys that drive up prices.

Wachsman decreased the operating temperature of solid oxide fuel cells to 650 °C, with future reductions projected to be as low as 300 degrees. At these lower temperatures, the system can turn on much more rapidly and operate with greater reliability, allowing The Cube to be built with conventional stainless steel parts rather than expensive alloys.

Schematic diagrams of structure of high-performance LT-SOFCs from low magnification (stack) to high magnification (nano/micro-structured electrodes). Functionally graded bismuth oxide (Electrolyte 1) / ceria (Electrolyte 2) bi-layered electrolytes effectively reduce ohmic polarization at lower temperatures. Carefully controlled nanostructured electrodes by infiltration provide highly extended reaction sites compensating exponentially reduced oxygen reaction kinetics at cathode and allow use of hydrocarbon fuels at anode at reduced temperatures. Source: Wachsman and Lee (2011). Click to enlarge.

In addition to lowering the operating temperature, Wachsman and his students and colleagues over the course of 25 years developed fuel cells that generate ten times the power at these lower temperatures than anything else on the market, cutting the system’s cost by a factor of ten. Power density is > 2W/cm2.

As part of the optimization, Wachsman developed dual-layer electrolytes using new materials and significantly improved the anode so it can withstand cycling.

Over a 25-year time period, we have achieved major advances in both the composition of fuel cell materials and the micro and nanostructure of those materials. Putting these together has resulted in a cell that has an extremely high power density, on the order of two watts per square centimeter.

—Eric Wachsman

The first-generation Cube runs off natural gas, but it can generate power from a variety of fuel sources, including propane, gasoline, biofuel and hydrogen.

Redox Chief Technology Officer Bryan Blackburn presents the PowerSERG 2-80 “Cube”.

Redox plans to release The Cube in 2014. The first version will be configured to 25 kilowatts, which can comfortably power a gas station, moderately sized grocery store or small shopping plaza. Additional power offerings will follow. Using different-sized fuel cell stacks, the company can offer The Cube at 5 kW, to provide always-on electricity for an average American home, or up to 80 kW in one system.

In the future, Redox plans to produce fuel cell systems for automobiles, which the company claims could triple gas mileage.


  • Eric D. Wachsman and Kang Taek Lee (2011) Lowering the Temperature of Solid Oxide Fuel Cells. Science Vol. 334 no. 6058 pp. 935-939 doi: 10.1126/science.1204090



That'll do.

Additional points to note from the videos:
The specific power is 3kw/kg

The volume of the illustrated 25kw cube has been shrunk by 60%.

It will be interesting to see how the anti-fuel cell brigade manage to diss this! ;-)
Probably simply by dismissing it as speculative, when they have infinite credulity for any amount of cost reduction and energy density increases in batteries!


Additional information on this technologies application to transport:

'Wachsman’s fuel cells currently operate at 650 ⁰C, and his goal is to bring that down to 350 ⁰C for use in cars. Insulating the fuel cells isn’t difficult since they’re small—a fuel cell stack big enough to power a car would only need to be 10 centimeters on a side. High temperatures are a bigger problem because they make it necessary to use expensive, heat-resistant materials within the device, and because heating the cell to operating temperatures takes a long time. By bringing the temperatures down, Wachsman can use cheaper materials and decrease the amount of time it takes the cell to start.
Even with these advances, the fuel cell wouldn’t come on instantly, and turning it on and off with every short trip in the car would cause a lot of wear and tear, reducing its lifetime. Instead, it would be paired with a battery pack, as a combustion engine is in the Volt, Wachsman says. The fuel cell could then run more steadily, serving to keep the battery topped without providing bursts of acceleration.'

So think SuperVolt, and no need for hydrogen infrastructure, but the smoothness and quietness of an electric car at all times, plus of course phenomenal petrol consumption efficiency at ranges greater than the battery can handle.

I would suggest that the optimum size of the battery pack would also likely to be lower, perhaps 7-8kwh, so further reducing weight and cost.


DM: the critisisms typically launched at fuels cells has more to do with PEM cells and the "hydrogen" economy which makes no sense. That said, who amongst the federal funding agencies was ever funding work to lower SOFC operating temperatures? It was a common misconception that the temperature needed to be maintained at about 800C to get on anode reforming. It seemed obvious to many that the material issues associated with 800C operations were substantial and that one way to overcome this was a lower operating temperature. I personally think this is a great strategy, but I would still make the battery about 20kwh. But heck, instead of dictating a single specific strategy why not allow the consumer to choose based on their typical usage. I'd say 7-8kwh would be fine for an urbanite, while the suburbs dweller would benefit from the larger battery.


Without checking the funding in detail, it seems likely that the University where much of this work took place benefited from DOE funding in one way or another.

I'm not sure why you should think that suburban drivers would want a bigger battery.
As long as it is big enough to make up for the stated deficiencies of the fuel cell, then it provides power at a lot better than the average efficiency of the US grid, especially after transmission losses.
So there is no point in burning NG at a central station, converting it to electricity, transmitting it, then storing it in a battery with losses at every point in the system.

In addition in areas with cold winters not only are batteries less efficient, but they don''t have the surplus heat that you can use by using NG on board.

The only ones who might prefer a more battery intensive vehicle would be those with their own solar arrays.
Mind you, at the latitude of the US that should be a fair few people by that time, as for vehicular use they still have the not insubstantial challenge of reducing the operating temperature to around 300C.

I'd guess production cars using this technology are at least 10 years out.

It is clear though that the money spent on fuel cells is far from wasted, as stationary uses alone justify every cent ever spent on every fuel cell technology, with very large increases in efficiency of fuel use, reduced CO2 etc enabled in this way.

I favour broad approaches to technological investment, rather than trying to pick winners too early.

Nick Lyons

Very cool technology. I foresee home CHP systems, immune to power outages (unless the gas supply is disrupted somehow, a much less common occurrence), providing power cheaper than the grid along with hot water and space heating.



"In the future, Redox plans to produce fuel cell systems for automobiles, which the company claims could triple gas mileage."..

AKA no new H2 infrastructure is a different kind of animal, but again - only the market place or highway will tell.

This fourth decade of taxpayer R&D grants/eleventh year of the Bush hydrogen[kill battery EVs] Initiative still has no fuel cell cars for public sale.


DM, because electricity will always be cheaper than fuel.


Your not choosing a winner when it's obvious who the winner is, your just recognizing the reality. I mean jeez, that's an old fossil energy warnings there. Next your going to tell me the batteries could blow up.



Decreasing battery power to 7 kWh will not make sence since battery shall support power as well otherwise supercaps shall be used and that complicates everything.
Would be good to have 30 kW gasoline FC (no hydrogen) as range extender. Question will be price, size, operating hours and reliability.
I do npt believe in distributed ireland power generation and power grid dismantling. By distributing on grid not dispachable solar or wind power generation just increaseng retail power prise to to generation and grid backup increase. This I know for sure.


Isn't this just a repackaged Bloom Box? Seriously - is there anything new here?


The electricity does not appear by magic.
It is largely the result of burning fossil fuel, often NG.
It is a lot more efficient to use the NG in this to produce electricity than burn it elsewhere then transmit it.

It will be interesting to see how the anti-fuel cell brigade manage to diss this! ;-)

This is about what I was hoping to see, to get rid of the ICEV.  Seriously.

BK4 nailed the objections:  this SOFC does not require hydrogen, so all the problems of hydrogen production and infrastructure just disappear.  An SOFC can burn LPG, methanol, ammonia or methane as well as clean gasoline.  Equip it with the appropriate fuel system and a traction battery for cold-starting and surge power, and you're good to go.  It would work pretty well as a PHEV, too.

I'm not sure why you should think that suburban drivers would want a bigger battery.

Because PHEV operation allows much greater displacement of delivered fuel, and greater flexibility of energy supply can only be a good thing.  If there's one thing people should know it's that if a large-scale energy source can't easily be used for anything else, it gets made into electricity.

there is no point in burning NG at a central station, converting it to electricity, transmitting it, then storing it in a battery with losses at every point in the system.

You have a point there.  However, using a 3 kW SOFC to heat your house and DHW while charging your car still makes a lot of sense. ;-)

I foresee home CHP systems, immune to power outages (unless the gas supply is disrupted somehow, a much less common occurrence), providing power cheaper than the grid along with hot water and space heating.

I don't see that happening where it really needs to.  If I have my figures right, delivered NG prices have spiked as high as $30/mmBTU in the New England region.  That's 17¢/kWh FUEL cost at 60% efficiency.  The grid is still going to be a good deal, especially if it's nuclear-fed.  The good thing about this SOFC is that it can be started more or less on demand, rather than having to be kept hot against need.


You are confusing power with energy.
The battery I suggest might be about the right size would be 7-8kwh, but the power output is way higher - that's kw, not kwh.
So the Audi A3 plug in hybrid for instance has 75kw, but a battery pack of 8.8kwh:

That sort of set up should work fine with something like this fuel cell, assuming they ever make the 300C version.


At 45-65% efficiency, this is better than the grid, certainly after transmission losses.
Not counting taxation, and assuming gallon equivalent prices of around $1 less than petrol, but three times greater efficiency as per the article, then you are talking 4-5 cents/miles.
You can go a heck of a lot of miles on that before it is worthwhile getting a bigger battery than you have to.

As I said though, this doesn't apply if you have your own solar array, when it would be worthwhile getting a bigger battery.
Of course, in strictly financial terms, a smaller solar array would still work out cheaper, but most people won't be bothered about that.

A bigger caveat is that they are nowhere near getting down to an operating temperature of 300C which they need for cars, and it may never happen.

Nearer term for vehicles, ACAL still has the advantage:

That would still need a hydrogen build out, but I really don't see that as a big deal.

This is great news in any case though, as vast amounts of power can be saved by co-generating electricity in the home.


When the 'delivered fuel' is natural gas, which is far less lossy in transmission than electricity, I can't see the problem.

Taking natural gas at around $1 gallon equivalent cheaper than petrol, and allowing for the claimed 3 times better efficiency, this will cost for the average car something like 4-5 cents/mile.
You can travel an awful lot of miles for the price of a bigger battery pack than you have to have.

As I said though, this does not apply to those with their own solar arrays, who will no doubt prefer to charge their cars that way, as people simply will not think in terms of the foregone interest on buying a larger solar array than they would otherwise need.

The real objection though is that they may never hit the 300C temp they need from this for vehicular use.

Nearer term, ACALs ultra-durable fuel cell seems the better bet, although of course it uses hydrogen.
I can't regard building a hydrogen infrastructure as the show stopper many can.

In any case, this is to be celebrated, as it looks as though it will enable enormous energy savings by enabling CHP in the home and in factories.

Kit P

“It will be interesting to see how the anti-fuel cell brigade manage to diss this! ”

Wait for it, wait for it!

And the cost is?

Roger Pham

The H2 infrastructure can be phased in gradually. First, convert the fleet and home FC-CHP to NG, but using H2-compatible piping and valves. Then, gradually feed into the NG supply piping and depot with H2 made from surplus solar, wind, nuclear, and biomass energy. This low-temp SOFC is great as a bridge toward a full 100% H2 economy.

Many high-tech advanced countries such as Japan, Germany, France, England, etc have no indigenous NG reserve and must rely on imported NG. Thus, they should have strong incentive to start preparing for an eventual H2 economy and infrastructure, to start harnessing domestic energy from solar, wind, and nuclear energy.


Just so.
If you have a natural gas station and a distributed model of supply is chosen, then as long as you have adequate space reforming can be done on site.
Germany and Italy both have of the order of 1,000 natural gas stations.

In addition, estimates of the roll-out costs for hydrogen infrastructure do not take account of the replacement costs for existing petrol pumps.
New legislation for the ventilation and prevention of leakage in tanks mean that replacement costs will be in the same ball park as the installation of a hydrogen pump in the US.
Since hydrogen provides around 2-3 times the mileage per gallon equivalent of petrol, then clearly although the reduction in the number of pumps needed will not go down that much, less will be required.

So once initial excess costs in setting up early pumps are covered, there would seem to be limited additional costs compared to maintaining the present petrol infrastructure, if indeed there is any additional cost at all.

SOFC would be nice if it can be done though.
For a start liquid fuels don't need an expensive high pressure tank.

william g irwin

It seems to me that H2 has 2 basic problems, high pressure storage w/compressors etc, and/or transmission and distribution. I've always thought that more local H2 generation could partially solve the distribution problem, but injecting increased amounts of H2 into the NG pipelines can make sense. I worry about the NG pipeline infrastructure as it ages, and the notorious ability of H2 to leak through pipe seals etc. Maybe converting H2 into methane or similar makes sense to allow existing pipeline delivery.
At any rate, this SOFC has the potential to be a game changer. The lower the operating temp, the more practical it becomes. I picture a REASONABLE priced <5kw unit as a grid attached home power source for regular use and emergency backup. Depending on size and weight, it has significant potential mobile applications too. I'm not sure how well it works as a flex fuel device, but it seems to have a lot more potential than other fuel cells discussed here.
Overall, great news - keep at it!


You do not want to put hydrogen into a 60 year old natural gas main, hydrogen makes metal brittle. Just turn natural gas into methanol at the fueling station, you have good distribution with that. Methanol can be reformed on the vehicle to run high temp PEM or lower temp SOFCs.



I had a massive European study linked somewhere on the effects of hydrogen in pipelines, which I can't locate.
However, this US study seems to cover the essentials:

New lines using hydrogen are not really a problem, as we have extensive experience in designing and using them for industrial purposes.
Leakage is higher but can be kept to acceptable limits.

In legacy NG pipelines hydrogen will be in admixtures, and a analysis and upgrading is needed according to how heavy the mix is in hydrogen.

In practise they will start with small admixtures, and upgrading will be a very gradual process.

Between blending hydrogen into existing NG pipelines and on site reforming the new pipes needed is manageable.


The problem with any "gradual" shift from piped CH4 to piped H2 is stoichiometry.  It takes 4 times the volume of H2 as CH4.  How many times would metering jets have to be replaced... and how many explosions would occur, when hydrogen leaked through avenues that are methane-tight?

Just keep the grid.  Use methane-burning SOFCs as peaking and backup generators.  Generate the methane from rotting garbage or whatever.



Irritatingly, I can't find the bookmarks for it at all, and googling is not helping as it often doesn't for German information.
It is probably different and easier to find if you are a German speaker, which I am not.
However, gradual introduction is just what they are doing, to use both biogas and spare electricity from renewables, stranded wind and excess solar.

However, I have dug out this analysis for the US:
'Relatively low concentrations of hydrogen, 5%–15% by volume, appear to be feasible with very few modifications to existing pipeline systems or end-use appliances. However, this assessment of feasibility will vary from location to location.
Higher concentrations introduce additional challenges and required modifications.
Preliminary cost estimates suggest that hydrogen could be
extracted economically at pressure regulation stations. For a station with a pressure drop from 300 to 30 psi, we estimate an extraction cost ranging from $0.3–$1.3 per kg hydrogen for a 10% hydrogen blend, depending upon the capacity and recovery rate.' (pg31)


Just keep the grid. Use methane-burning SOFCs as peaking and backup generators. Generate the methane from rotting garbage or whatever.

Don't forget that rotting garbage also produces CO2 - which can be combined with Davemart's hydrogen to synthesize even more methane. So even if you do generate H2 you still don't need to mix it, as is, into a CNG pipeline.

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