L-16s like higher voltages [RE-wrenches]

Eric Smiley Eric_Smiley at bcit.ca
Thu Jan 17 12:27:06 PST 2002


Good points Phil.

>a fossil fueled generator is ideal for bulk
>charging at high C rates, and the array charge at the lower C rate
necessary
>for finish charging.

That's how it was explained to me years ago, and I still thing it's the
right thing to do.

>a 50-80% discharge every cycle (that's
>every night, folks), and replace a small bank more often.  I can't
quite
>commit to going that extreme, but I took his information to heart.

It does sound extreme. How do we find the best compromise between
frequent replacments due to deep cycles (small battery) and frequent
replacments due to undercharging (large battery)?

In theory, oversizing a battery to keep the cycles shallow will prolong
battery life. But this means the PV array cannot provide a good charge
rate and running the generator is critical to achieving long battery
life.

Maybe that works in commercial apps, but in residential systems, as Phil
pointed out, people may not want to (and may be proud not to) run the
generator. Thus the batteries cycle repeatedly below 100 percent,
reducing their capacity/life.

Finding the optimum combination of generator run time (fuel cost,
generator maintenance costs) battery size and PV array size to minimize
costs is not trivial. Then you add the human factors ...

Optimizing for cost with computer models tends to produce designs with
significant generator run time, unless the fuel costs are particularly
high.

Eric Smiley - Project Leader
Photovoltaic Energy Applied Research
BCIT Technology Centre

phone: 604.432.8657    fax: 604.436.0286
esmiley at bcit.ca             www.tc.bcit.ca

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