hybrid power systems vs combined cycles.

I know very little thermodynamics. I read today that California is going to put 4 acres of solar arrays in place to generate some 500MW of electricity. The conversion will be by Stirling cycle in an oil-barrel size container where gas will drive a crankshaft. If this is up your alley, maybe there is some future. Don't quote me on those figures.

j

I would not be looking to fuel cells in the near future. We have tested several ( in the ~3kW range) and they are all plagued with the same problem: short stack life. These units were running on lab grade Hydrogen and the stacks still die in 6 months or less. I don't think anyone is going to want to pay a fortune to replace fuel cells once a year (or less).

Charles Perry P.E.

Solar arrays,Stirling cycle, 500MW in an oil barrel size container? Somehow these don't add up. Assuming that 500 Mw can be concentrated in an oil barrel sized unit and assuming a hopeful 20% efficiency, then 400MW into that volume as waste heat would be quite spectacular, but short lived.

PEM cells? Who are the OEMs?

PEM and others. As for the OEMs; sorry, I am not at liberty to say. We get paid to test things and, more often than not, are prohibited from providing information to anyone other then the funder(s).

Short stack life is not a big secret. If you read technical publications, not the stupid newspapers (what idiots), you will find quite a lot written about it. PEMs are particularly sensitive to contamination of the stack, but other technologies have their problems also. Will the life increase? I would say yes, but not in the near term. Of course, if the Government was to throw tons of money at it, it would happen much quicker.

Charles Perry P.E.

I know about PEM FC's short stack lives... I was more interested in the players.

I haven't followed FCs very much in the past year. PEMs definitely operate at lower temps than others and are more versatile. I'm not sure how they will address the contamination problem; it's been its Achillies heel since the beginning. Bummer, so far they hold the most promise for consumer markets. I agree that they will eventually have longer lives and get cheaper as they come of the curve. You would think with all the public discontent over energy prices, there would be more money flowing into their R&D. Of course, the government has priorities other than cheap energy. A dollar spent it s penny earned??? Hell, it's only money.

Igor

One problem with the economies of fuel cells is "where do I get cheap hydrogen?" Using a reformer to get it from natural gas is not very attractive from envitronmental or cost perspectives (natural gas is expensive). Using any hydrocarbon means that you get CO2 as well as water vapor as a byproduct. I real, long term answer, in my opinion, is to use electricity generated by nuclear plants to make hydrogen. Then the hydrogen can be used to replace other portable fuels (gas, diesel, etc).

Charles Perry P.E.

Like most "low pollution" solutions, using natural gas just moves the problem elsewhere. Spent fuel disposal is the obvious problem with nuclear, but it may be the best solution overall.

Some basic numbers:

Gasoline: 9000 Wh/liter 13,500 Wh/Kg

Hydrogen: (STP) 2.7 Wh/liter 39,000 Wh/Kg

Hydrogen: (150 bar) 405 Wh/liter 39,000 Wh/Kg

So the problem is not only how you make hydrogen, but how you get it where it's used and how do you keep it there. With a 3-to-1 weight advantage there's room for some fancy containers!

Add batteries and/or fuel cells, and the complexity increases.

Ammonia? We sure as hell produce a lot of it and inexpensively I might add. Perhaps that might be a key in one of several steps in producing hydrogen. The infrastructure is already in place. So far as storing it on a vehicle, perhaps store it as a hydride and use catalysts to free the hydrogen on an as needed basis. It sure would keep things a lot safer. Anyway, I think this idea was kicked around a long time ago... 40s 50s???...not really sure what ever bacame of it.

Yep, and it's a good one. That, and perhaps in the future when new facilities are built, think in terms of energy centers. Build nuclear power plants specifically for large scale production of alternate fuels. If there is any surplus power, it can be sent to nearby factories, industrial parks, etc... If enough thought is given to the design, even the superheated water can be utilized as an energy source.

I thank all for the answers. Last, with new technologies I thought that fuell cells can convert hydrocarbures to electrcity immediatly starting from natural gas and not from hydrogen. This thinking was due to this summary of milestones of fuel cells by siemens:

Even if i come from the city of Alessandro Volta, I'm not good in chemistry and elettrochimic processes. :-)

Bye and thanks.

_mark schrieb:

Hello,

PNG means purified natural gas, but this gas goes first to a reformer which produces hydrogen which goes to the fuel cells.

Bye