03-31-2011, 03:36 AM
I've commented on this before (http://www.punaweb.org/Forum/topic.asp?TOPIC_ID=8380&whichpage=6), but the main purpose of batteries, in my opinion, in a residential PV installation is to get you through the night and, secondly, to cushion very gray days. The purpose of the generator is to feed the batteries at night, handle very gray days and occasional heavy loads. If you commonly need to run a generator during the day the solar panel installation is inadequate for your power draw or you designed it that way. Usually a money versus life style issue.
That said, a 25kw generator seems huge overkill unless you are planning large power draws (a/c, big refrigerator) and you are looking at the solar panels only as supplement. Your system is almost 3x our 2.6kw system (3-3.5kw typical daily draw), but I can easily charge our eight L-16 batteries with our 3kw Honda in a few hours in the evening even though we are watching TV and only on battery power. Our original set of twelve batteries was also easily charged by a 6500 contractor style generator. The generator previous to the Honda was a 6.5kw Chinese propane machine, about $1000. Propane was selected for one major reason. Since we only used the generator occasionally the fuel never got stale or collected moisture. A plus was that the machine was much cleaner to operate and maintain than a gas or diesel. The portability of the Honda turned out to be very useful for us at the nursery and it's being used for a lot more than charging batteries now.
White Cloud Nursery
www.whitecloudnursery.com
"If you think education is expensive, wait until you see how much stupid costs"
That said, a 25kw generator seems huge overkill unless you are planning large power draws (a/c, big refrigerator) and you are looking at the solar panels only as supplement. Your system is almost 3x our 2.6kw system (3-3.5kw typical daily draw), but I can easily charge our eight L-16 batteries with our 3kw Honda in a few hours in the evening even though we are watching TV and only on battery power. Our original set of twelve batteries was also easily charged by a 6500 contractor style generator. The generator previous to the Honda was a 6.5kw Chinese propane machine, about $1000. Propane was selected for one major reason. Since we only used the generator occasionally the fuel never got stale or collected moisture. A plus was that the machine was much cleaner to operate and maintain than a gas or diesel. The portability of the Honda turned out to be very useful for us at the nursery and it's being used for a lot more than charging batteries now.
White Cloud Nursery
www.whitecloudnursery.com
"If you think education is expensive, wait until you see how much stupid costs"