Fossil Fuel Power Plant vs. Fuel Cell Power Plant

[chicopee]

The overall efficiency of Fossil Fuel Power Plants is low and to this date I can not understand the inept position of Utility Companies for not constructing Fuel Cell generators. Such construction would again put the USA in the fore front of technology. What is holding back research and development in this field afterall fuel cell experiments have started way back I think to the 19th century. Inputs are greatly appreciated.

 

[kenvlach]

I haven't done any analysis, but to get the response started, will give some thoughts:

Fuel cell plants are probably inevitable if energy costs rise and pollutant emissions levels get decreased, but we're not there yet. It seems a bit odd that Honda & others are selling fuel cell powered cars & buses (on a limited, money-losing basis) in California

http://www.cafcp.org/about_member_auto.html

since fuel cells are ideal for continuous, stationary power source

Coal is cheap,
the US hasn't adopted the Kyoto accord re CO₂,
the EPA isn't requiring BACT for mercury & other emissions,
Bechtel is good at building fossil fuel-fired plants,
cooling water is (usually) cheap and thermal pollution of the environment is usually ignored,
fuel cells don't easily scale up because of CTE problems with seals for corrosive electrolytes,
pure fuels are (usually) required to avoid fouling,
(my guess) initial cost is higher,
and politics (lobbying) is involved.

But, I see that the big boys BP + GE are going to mass produce hydrogen via water gas shift reaction, with CO₂ sequestration, so this could be fuel cell-enabling (H₂ is the ideal fuel for fuel cells):

http://www.latimes.com/business/pri...1,2130768.story?coll=la-headlines-pe-business

[note: only available for a limited time, so download if you want to save]

P.S. There is a fuel cell forum, but not many MechE's venture there:
Hydrogen and related fuel cell engineering Forum
forum804

 

[moltenmetal]

chicopee:

If the source of energy in the first place is fossil fuel, using a hydrogen fuelcell in a powerplant at the present time is pretty much pointless from an energetic standpoint. Forget about the capital cost implications!

You need to look at the overall efficiency of any process, rather than merely looking at a segregated part like the heat engine or the fuelcell. And you need to look at the real rather than the theoretical efficiencies of all the steps, taking into account the useful, beneficial products of each step. Though a fuelcell is not a heat engine and is not limited by Carnot efficiency, it is still a real machine, subject to other real-world considerations. The design of a fuelcell becomes a number of trade-offs of efficiency versus lifetime, function or cost, just like for all other real machines.

Converting fossil fuels to synthesis gas (CO and hydrogen) and then using the water gas shift reaction to react water and CO to make more hydrogen: that is established technology. Mature technology, unlikely to improve enormously in the next hundred years. As it stands, reforming fossil fuels to hydrogen is still a lossy process from an energetic standpoint. It's also a capital-intensive process: it takes large, expensive equipment to carry it out. The smaller you make these reformers, the lossier they get.

Converting fossil fuels to hydrogen of sufficient purity to operate a proton exchange membrane fuelcell long-term is a VERY lossy process. PEM fuelcells are sensitive to carbon monoxide even at low concentrations. The only way to deal with this problem at present is to either waste fuel by bleeding it off in a purge stream or to do a very scrupulous (and energy-wasteful) job of purifying the feed hydrogen to remove CO- or both.

Add to that the energetic cost of mining and refining the platinum these fuelcells need to function, and you get a real lifecycle cost problem.

To make the energetics look better, people touting fuelcells start talking about heat integration. They find ways to make use of the waste heat generated during reformation and by the fuelcell and by burning the "tailgas" etc. But if you do the same job of utilizing the waste heat from a conventional power plant, the energetics there don't look nearly as horrible either. If the intent is to generate both electricity AND low-grade heat, a conventional power plant can be made quite efficient without the need to build an expensive hydrogen reformer at the front end.

Where fuelcells shine is when the source of energy is electricity generated from renewable sources. Once you have electricity, you can make hydrogen by electrolyzing water with comparative efficiency- but again, not with 100% efficiency. This only makes sense if you can make beneficial industrial use of the product oxygen, which accounts for a good portion of the energy input. Unless you can use the oxygen, there are more efficient ways of storing energy for stationary power plants than using hydrogen as a storage medium. Hydrogen suffers from numerous problems as a storage medium for energy, not least of which being its tiny energy density per unit volume. Capital cost for storage facilities becomes enormous, and the temptation to waste yet more energy to compress the hydrogen for storage tends to take over.

The problem is simply this: energy is too cheap, and the monetary cost of dumping CO2 and other contaminants to the atmosphere is zero. Until these two problems are dealt with, the economic equation will continue to yield energy solutions that are bad for the planet as a whole. Remove these two obstacles and the options for energy generation AND wiser use of energy become enormous. That's a future I personally would like to see.

 

[metengr]

There are advanced fossil fuel technologies that can be utilized to achieve significantly reduced gas (including carbon dioxide) and particulate emissions and improved cycle efficiency. Like most utilities, building of a new, central power station is a lot more difficult under today's political and social climate. Today, decisions are made by return on investment and profit margins.

If anything, I see a real resurgence in nuclear power over the next 5 years. I am of the opinion to spread the wealth and have multiple resources of energy.

 

[chicopee]

Yes I am of the same opinion with you Metengr. I know that United Technology has been in the fuel cell research and development for several decades, yet their efforts does not seem to have made much impact with Utility Companies, so there must be some reason. Dont get me wrong U.T. is applying fuel cell technology in several areas and go thru great length to protect their investment from our "across pacific" neighbors, yet after about 40 years of R.& D. I still see little evidence of that in the public domain. Why??

 

[kenvlach]

chicopee, seems that your title was wrong. Fossil fuel-fuel cell hybrid plants, using both thermal heat from coal gasification and hydrogen-powered fuel cells, seem promising for the future (& employment of engineers!). Takes into account moltenmetal's comments on efficiency losses if only using the hydrogen.

Gasification Technology R&D

http://www.fossil.energy.gov/programs/powersystems/gasification/index.html

"...
In a typical coal combustion plant...only a third of the energy value of coal is actually converted into electricity by most combustion plants; the rest is lost as waste heat.

A coal gasification power plant, however, typically gets dual duty from the gases it produces. First, the coal gases, cleaned of impurities, are fired in a gas turbine - much like natural gas - to generate one source of electricity. The hot exhaust of the gas turbine is then used to generate steam for use in a more conventional steam turbine-generator...fuel efficiency of a coal gasification power plant in this type of combined cycle can be boosted to 50 percent or more.

Future concepts that incorporate a fuel cell or a fuel cell-gas turbine hybrid could achieve efficiencies nearly twice today's typical coal combustion plants. If any of the remaining waste heat can be channeled into process steam or heat, perhaps for nearby factories or district heating plants, the overall fuel use efficiency of future gasification plants could reach 70 to 80 percent.
{my emphasis}
..."
As to a nuclear energy resurgence as predicted by metengr, it's 1) a NIMBY problem and 2) less likely in the US & China, which have lots of coal. Success in clean coal technologies (see FutureGen synopsis and list of sponsors listed below) will perhaps limit growth in nuclear.

A political factor which may aid nuclear energy -- It might aid in keeping nuclear materials from terrorists. I recall that Russia (& maybe Ukraine) have decommisioned warhead material that the US is buying and converting to reactor fuel, but conversion capacity and funds are limited, so at present rate will take until 2015 or later.

A technical & political factor which may help nuclear energy is use of the transmutation process to reduce the amount of longterm radioactive waste. Highly radioactive components of spent fuel from current plants can be separated out to make new fuel rods, which via neutron irradiation become less radiactive elements -- the reverse of breeder reactors for creating warhead material. Info from Nuclear Wastes -- Technologies for Separation and Transmutation, National Research Coucil (1996). Expect that there has been further progress.

FutureGen - Tomorrow's Pollution-Free Power Plant

http://www.fossil.energy.gov/programs/powersystems/futuregen/index.html

"FutureGen is an initiative to build the world's first integrated sequestration and hydrogen production research power plant. The $1 billion dollar project is intended to create the world's first zero-emissions fossil fuel plant. When operational, the prototype will be the cleanest fossil fuel fired power plant in the world...."

FutureGen Advances April 21, 2006

http://home.earthlink.net/~cevent/4-21-06_gen_advances.html

"...FutureGen will cost about $962 million. Of that, the coal industry will pony up $250 million while foreign governments -- China, India and Korea are all involved -- will contribute $80 million. The U.S. government will cover the roughly $700 million balance...
The FutureGen Industrial Alliance is a coalition representing some of the world's largest coal companies and electric utilities that are partnering with the Energy Department to design, build and operate the plant. They include American Electric Power and Southern Co. as well as Peabody Energy and Consol Energy. Meanwhile, the China Huaneng Group, the largest energy company in China, has joined the group..."

FutureGen Alliance Announces Final Candidate Host Sites

http://www.futuregenalliance.org/news/releases/pr_7-25-06.pdf

"WASHINGTON, DC, July 25- The FutureGen Alliance today announced its short list of candidate sites for a $1 billion first-of-its-kind, near-zero emissions coal-fueled power plant following an extensive technical review. Of the 12 competing sites in seven states, the Alliance concluded that four sites are best suited to host the FutureGen facility. These sites are:
?? Mattoon, IL
?? Tuscola, IL
?? Heart of Brazos near Jewett, TX
?? Odessa, TX
..."

 

[chicopee]

Kenvlach-You know how these discussions go; they never seem to take a straight path.

 

[kenvlach]

Yep, politics & jobs & lobbying & profits & NIMBY can matter more than the science & engineering.