Post by cye on Mar 15, 2011 15:59:52 GMT -5
Pete (from Galloway, Scotland) asked me whether the 12v dc 6 watt pumps (that most of us here seem to use) will run directly off a solar pv panel. Well the recommended practice when running the pump off PV is to rig the PV up to trickle charge a battery and then run the pump and controller off the battery. But Pete doesn't want to use a battery and controller as he only wants the pump to help out (kickstart) the thermosyphon on his homebuilt radiator-type solar water heating panels.
Anyway, I have happen to have just one 9w peak pv panel so I thought I'd check it out when the sun peeked out between the clouds in the late afternoon today. I should say that wasn't expecting too much because I know 9w peak isn't enough but thought I'd give it a try and record the results.
I took a short video clip of the pump running on PV, but it's too big a file for this forum , so I've uploaded the video clip to the solarco-op.net website instead. You'll get the link to the clip at the very bottom of the following downloads page:
www.solarco-op.net/downloads.htm
You can see it's fairly direct but weak late afternoon sunlight (we're not quite yet into Spring). The panel surprisingly managed to maintain 8.8V across the pump while the pump was running. The pump's operating voltage range is officially 9v-14v. As you can see the pump was working fine, but what you can't see is that when the sun went back in behind the clouds again the pump stopped dead!
Probably what's required here in this climate is something along the lines of a 20w peak pv panel, and probably a bit more again if you want pumping in cloudy spring/autumn conditions.
A 20w PV panel is only a 20w peak rating, and peak sunlight is rarely obtained. I've heard people say to use a 30-40% adjustment factor for pv peak ratings to get an average output.
Pete, if you're reading this, I'm hoping if you are going to experiment with running this type of pump off a pv panel, that you'll let us know how you get along, and perhaps maybe even post up some pictures here of your homebuilt panel setup?
Anyway, I have happen to have just one 9w peak pv panel so I thought I'd check it out when the sun peeked out between the clouds in the late afternoon today. I should say that wasn't expecting too much because I know 9w peak isn't enough but thought I'd give it a try and record the results.
I took a short video clip of the pump running on PV, but it's too big a file for this forum , so I've uploaded the video clip to the solarco-op.net website instead. You'll get the link to the clip at the very bottom of the following downloads page:
www.solarco-op.net/downloads.htm
You can see it's fairly direct but weak late afternoon sunlight (we're not quite yet into Spring). The panel surprisingly managed to maintain 8.8V across the pump while the pump was running. The pump's operating voltage range is officially 9v-14v. As you can see the pump was working fine, but what you can't see is that when the sun went back in behind the clouds again the pump stopped dead!
Probably what's required here in this climate is something along the lines of a 20w peak pv panel, and probably a bit more again if you want pumping in cloudy spring/autumn conditions.
A 20w PV panel is only a 20w peak rating, and peak sunlight is rarely obtained. I've heard people say to use a 30-40% adjustment factor for pv peak ratings to get an average output.
Pete, if you're reading this, I'm hoping if you are going to experiment with running this type of pump off a pv panel, that you'll let us know how you get along, and perhaps maybe even post up some pictures here of your homebuilt panel setup?