Tweaking the Solar Generators

The first full day of Thanks for Nothing has come and gone – and we have once again survived without some of the conveniences of a modern society.  Amazing. 
Annie enjoying dinner by candle light in front of the wood fire.
Annie enjoying dinner by candle light in front of the wood fire.
My role on the first day was largely technical.  As mentioned, we are trying out our solar generators – trying to test them and push them to their limits.  Well, right off the bat we found some limits.

We built three units.  The small unit, complete with a 400 watt inverter, a 35 amp-hour battery and all the other bits and bobs that make it work seems to be doing its assigned job just fine. In fact, I am connected to it as I write this.  For more than a day it has managed to supply power to my laptop, printer, cordless telephone and lamp (see, a complete office if your office consists only of a laptop, printer, telephone and lamp).  

We used the laptop all day – plus watched two movies on it during the evening (actually documentaries – so we are still pure and righteous).  We have also been listening to the radio over the internet on the laptop.   Some day we might actually stream music and join the modern world more completely.  As I type this, the unit just gave out a squawk that it was at the end of its juice.  So 24-hours seems to be the limit on this unit.  That will probably get you through most power outages.

The middle unit is, as you would imagine, a bit bigger.  It has a 750 watt inverter and a 110 amp-hour battery.  We determined to use this for the refrigerator, as our LG fridge only draws about 165 watts when running, I figured this would be more than enough.  But we have learned something about inverters (and motors).  

When the refrigerator kicks on (and this applies to any appliance with a motor), it draws a bit more energy in the first few seconds of operation (a surge).  Our inverter is supposed to handle this, rated to up to 1500 watts for a few seconds, but happier if only providing 750 watts or less on a continuous basis.  

We found that when the refrigerator tried to kick on, the inverter would indicate it was overloaded (even though it was well below its rated limit).  It would do this four or five times, then chug away happy as could be.  I worried that all this might be putting a strain on our refrigerator – so we moved the bigger unit in to take over.

The large unit has a 2,000 watt inverter and a 225 amp-hour battery bank.  The refrigerator is really happy with this unit.  We need to do a bit more testing, but it looks like there needs to be a lot of headroom in inverter capacity when working with motors – much more than the rated watts of the unit might suggest.

So we are off and running, settling into the slower pace of Thanks for Nothing month.  Dinner must be anticipated well in advance and cooked on the wood stove.  It is eaten by candlelight, which is never a bad thing.
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Jay

Jay and Annie Warmke run a sustainability center in southern Ohio that features an Earthship (a passive solar home made of tires and garbage), straw bale buildings, various critters and more. Find out all about it at www.bluerockstation.com

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