Big box stores could ditch the grid, use natural gas fuel cells instead

Big box stores could ditch the grid, use natural gas fuel cells instead
Natural gas powered solid oxide fuel cells, located at the point of use to produce electricity for facilities the size of big box stores, could provide economic and environmental benefits, with additional research, according to new study. Credit: Pacific Northwest National Laboratory

Large facilities like big box stores or hospitals could keep the lights on by using a fuel cell that runs off the natural gas that already flows in pipelines below most city streets.

Instead of drawing electricity from the power grid, facilities could use -powered cells to lower their electric costs, increase power reliability, reduce , and maybe even offset costs by selling excess -generated power back to the power grid. Such an energy future could be possible—assuming fuel cell lifespans are improved and enough systems are produced to reach economies of scale—according to a cost-benefit analysis published in the journal Fuel Cells.

If such advances are made, researchers at the Department of Energy's Pacific Northwest National Laboratory conclude natural gas solid oxide fuel cells could play a significant role in meeting future energy demand. The technology could help meet the 10 percent increase in electricity the nation will need in the next decade. That estimate, by the U.S. Energy Information Administration, will require 68 gigawatts more generating capacity.

PNNL's study focused on distributed generation, where fuel cells are located right at the individual facilities they power. This is different than the traditional central generation approach to energy, where large power plants are often located far away from end users.

Instead of burning fuel like combustion engines, solid oxide fuel cells oxidize it electrochemically. Each cell is made of ceramic materials, which form three layers - an anode, a cathode and a solid electrolyte, much like a battery. Multiple cells must be assembled into a fuel cell stack to achieve the desired power output.

Solid oxide fuel cells are inherently highly efficient in converting fossil fuels to electrical energy and PNNL's unique system design, which includes anode recycling, steam reforming, and pressurization, advances the technology even further.

"On the anode side of the fuel cell, we recycle waste heat in a steam reformer to squeeze even more energy out of the fuel - about 25 percent more chemical energy compared to typical solid oxide fuel systems," said Larry Chick a materials engineer at PNNL. "The stack operates under high pressure - about the equivalent of being 230 feet under water. That increases the power density, which reduces the size of the stack by about 60 percent and lowers the fuel cell's overall cost significantly."

The researchers based their cost modeling study on a small-scale solid oxide fuel cell system designed, built, and tested at PNNL and a larger conceptual system of 270 kilowatts, which is enough to power a large retail facility or light industry. Cost estimates are expressed in 2012 dollars.

The study showed that for the same power output, a natural gas fuel cell would cost almost one-third less to build than a centralized natural gas combined cycle plant.

"We were intentionally conservative as we calculated the cost of both building and operating natural gas solid oxide fuel cells and other types of generation," said PNNL economist Mark Weimar. "For instance, in comparing the to a 400 megawatt natural gas combined cycle plant, we assumed that the larger, central generation plant would pay cheaper wholesale prices for natural gas compared to smaller, distributed generation fuel cells, which we estimated would pay retail or almost double the wholesale cost."

The authors report that if stack life improvements are made and mass manufacturing is achieved, natural gas solid oxide fuel cells can be cost-competitive with natural gas combined cycle plants, which are projected to generate electricity at a total cost of 6.5 cents per KWh. They calculated natural gas fuel cells would have a total electricity cost of 8.2 cents per kWh.

When researchers factored in the additional benefits of distributed generation, it brought the cost down to 5.3 cents per kWh. Those benefits stem from the fact that fuel cells don't have the extra costs and power losses associated with transmission and distribution power lines that central power plants experience.

Higher efficiency, lower emissions

The high efficiency of natural gas fuel cells means fewer greenhouse gas emissions as well. The PNNL prototype showed 56 percent electrical conversion efficiency compared to 32 percent from conventional coal plants and 53 percent from natural gas combined cycle plants. The study shows that the natural gas fuel cell system would produce 15 percent less carbon dioxide per kWh than a modern natural gas combined cycle power plant.

Additionally, since a distributed generation natural gas fuel cell system would be installed on site, some of the heat from the fuel cell could be used to heat water or interior spaces. If just 20 percent of the fuel cell heat replaced the use of grid electricity for heating, then the fuel cell system would produce 22 percent less carbon dioxide than large-scale natural gas combined cycle plants tied to the grid.

Currently, fuel cell stacks last only about two years. Over time, as the fuel and oxygen are constantly being pumped in and run over the catalyst in the cells, the chemicals start to degrade and the system starts to wear down. The study noted fuel cell stacks would need to last six to eight years to be competitive, and uses a15-year lifespan in the study's cost comparison table.

With additional research, the limited stack life can be overcome," Chick said. "It's a matter of conducting reliability testing on integrated systems and using advanced characterization techniques to figure out what is degrading the performance of the stacks over time. The Department of Energy's Solid Oxide Fuel Cell program has been achieving targeted improvements over the last decade, so things are moving in the right direction."


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More information: Chick, L., Weimar, M., Whyatt, G. and Powell, M. (2015), The Case for Natural Gas Fueled Solid Oxide Fuel Cell Power Systems for Distributed Generation. Fuel Cells, 15: 49-60. DOI: 10.1002/fuce.201400103
Journal information: Fuel Cells

Citation: Big box stores could ditch the grid, use natural gas fuel cells instead (2015, March 4) retrieved 20 July 2019 from https://phys.org/news/2015-03-big-ditch-grid-natural-gas.html
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Mar 04, 2015
This study comes from proponents of fuel cell power and it is clear, after reading the article, that this technology has a long way to go before it can be expected to power 'big box stores.' I remember, in the 1960's, hearing how fuel cells would soon be a major power source.

The proposed cells operate at high temperatures and pressures. In this case these cells don't result in any dramatic reduction of CO2 release from their fossil fuel source as compared to other fuel cells that are fueled from H2 derived from water.

It would be ashame if the dream of water exhaust fuel cells was bent to just create another way of oxidizing the fossil fuel methane.

Mar 04, 2015
The writer needs to go and do some more research too. There are quite a few natural gas power systems using big engines and generators out there. The excess heat is normally used in the heating and cooling systems of the buildings involved. Many of those systems are much more than 53 percent efficient when all the uses of the heat and power are factored in. Those fuel cells are going to have to last 15 years or more (like the study wants) if they expect companies to spend the money to install them.

Mar 04, 2015
I want a nat gas, or propane PEM fuel cell for my house and car. No chitzy battery charger either, the car cell needs to be 400k/w or larger (same output as my gasoline fueled V8).

Mar 04, 2015
While this sounds great on the surface I'd offer a couple of observations. To start with, stack life is currently two years due to contamination but the article notes at the end that commercial viability requires a stack life of 15 years. The stack life problem is not new and I'm not sure it;s easily solved when natural gas is used instead of pure hydrogen. Second, in order to be competitive with a natural gas plant the fuel cell has to have a capital cost well below $2,000/kW (closer to $1,000/kW in Texas) yet Bloom boxes (a commercially available fuel cell system that got lots of favorable press several years ago) cost more than $7,000/kW.

Fuel cells may make sense in certain specialized applications or where businesses are willing to spend lots of money to make a statement, but it's going to be a very long time before they become affordable for most homes and businesses.

Mar 05, 2015
The proposed cells operate at high temperatures and pressures. In this case these cells don't result in any dramatic reduction of CO2 release from their fossil fuel source as compared to other fuel cells that are fueled from H2 derived from water.


The interesting prospect is that the natural gas grid can tolerate up to a third of hydrogen in the mixture, which can be produced by various renewable means.

Biomass can be gasified into syngas, and further refined into methane, methane can be produced directly out of bacterial fermenting, excess electricity can be turned into methane in power-to-gas synthesis - there's an infrastructure that readily accepts renewable energy inputs and solves the massive storage problem as a built-in feature.

The electric grid infrastructure does none of that.

(same output as my gasoline fueled V8).


Your car doesn't actually reach 400 kW except under very specific operating conditions.

Mar 05, 2015
Utilities will likely be opposed to customers who use much electricity to self-generate.

The Mirage Casino in Las Vegas threatened to do this many years ago when the utility was going to raise its rates.


Mar 05, 2015
Except extracting H2 out of H2O requires energy and a fair amount of it.

Mar 05, 2015
This is not a new thing. I can recall ads for Bloom fuel cells more than 20 years ago.

It would have been great if these people had worked a bit harder on the fuel cell catalysts. See http://phys.org/n...uel.html

I too like the idea of using Natural Gas fuel cells to power businesses and neighborhoods. It could be surprisingly efficient, especially when you consider that there isn't nearly as much transmission loss. And no, it doesn't have the carbon neutrality that we'd all like to see, but it is still an improvement over what we're doing now. Let's not make a better solution the victim of a nonexistent theoretical "best" solution (whatever that might be).

Mar 08, 2015
@ackEllisTahoe
Second, in order to be competitive with a natural gas plant the fuel cell has to have a capital cost well below $2,000/kW (closer to $1,000/kW in Texas) yet Bloom boxes (a commercially available fuel cell system that got lots of favorable press several years ago) cost more than $7,000/kW.
Thats a very good point, and there are other forms of energy that may be even more appealing. Photo-voltaic (PV) solar panels are now below a $1/watt (I've even seen them as low as $0.47/watt). THe payback time a a PV system can be as little as a 3 years.

For natural gas, you will always have the cost of fuel + the maintenance of the fuel-cell etc.


Mar 09, 2015
Photo-voltaic (PV) solar panels are now below a $1/watt (I've even seen them as low as $0.47/watt). THe payback time a a PV system can be as little as a 3 years.


That's per peak Watt, not average Watt.

The true cost per average is between 7x and 14x higher as you go south to north - from San-Fransisco to New York, or Madrid to Berlin. With your figures, that corresponds to between $3.30...$6.60 per Watt.

And I assume that's for some eBay/Alibaba panels you're supposed to install and maintain yourself, so the labor costs aren't counted in.

For natural gas, you will always have the cost of fuel + the maintenance of the fuel-cell etc.


And for solar you have cleaning costs and replacing damaged or failed panels. Cleaning is especially important, because individual shaded cells sink power and heat up from the current provided by other cells, which can lead to damage and early failure.

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