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Author: metallurge Add to my Favorite Fools Ignore this person (you won't see their posts anymore) Number: of 748914  
Subject: Re: OT: Fuel Cells for remote site Date: 3/28/2001 2:38 PM
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<Sorry for the repetition of my whole last posting, but it's relevant... --Metallurge>

SeattlePioneer writes,

You'd better size that based on your peak seasonal loads, not the year around average. If you don't have air conditioning, the peak load is usually in the wintertime, and a winter time bill will be for twice or more the average power level used throughout the year. That one KW fuel cell made be a perpetual brownout during the winter months since it and the battery supplements will be underpowered for average household
usage.

...to which duggg replies,

That's an excellent point.

...to which I (metallurge) say,

Well, what you're both forgetting is that a 1kW PEM fuel cell produces about 1.2 kW in usable heat, besides the electricity. This heat can be used for hot water, and environmental heating. If you have a use for the heat, the overall efficiency of a PEM fuel cell rises from the 40% electrical efficiency to more like 70+% overall.

...to which SeattlePioneer then replies,

OK, put it in the living room and we'll all snuggle up to it! What do we do in the summer, though?

..to which I (metallurge) respond,

Actually, I'll probably locate mine outside and use a heat exchanger, but I guess if you want to put yours in your living room...

If you look back to your original statement, you were talking about sizing a fuel cell to match peak demand, which you thought would be in the winter. Since fuel cells produce excess heat which is easy to use for things like water and space heating, clearly the peak season for a fuel cell is going to be summertime. In my HVAC ignorance, I'm going to cautiously assert that you can in fact use heat to power an air conditioner, but at low efficiency. You could also use an evaporative cooler. Or you could use a battery bank to store the excess fuel cell output at night for use during the hottest part of the day. Or just use a bigger-than-1kW fuel cell to handle the bigger-than-1kW load. I don't see anything in what you've said that is a showstopper. The bottom line is that when you're paying for electrical capacity, whether it's by way of a fuel cell, generator, or anything else, it pays to try hard to minimize peaks in usage.

To diverge a little from the original subject, when you're on-grid with a fuel cell, in 30 states, you can to some degree or another sell excess electrical production back to the utility, just like the solar and wind power folks can do. Or, use the electrical grid as your storage device in the air conditioning example. Size the fuel cell for average monthly usage. Feed electricity into the grid at night, spinning the meter backwards. Draw needed excess capacity from the grid later during your peak demand, spinning the meter forwards.

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