Solar PV System for Workshop

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Becca58
Becca58 Registered Users Posts: 3
Hi, I'm new here. I've been fascinated with solar for decades and even done a couple of tiny projects with them, and now the opportunity has come up to use it for a bigger project. I thought I knew what I needed to do, but the more research I've done, the more confused I seem to be making myself. So I thought I'd find a forum and ask folks who've done this sort of thing before for their expertise.

Here's the project:

We're going to get a shed to use as both outdoor storage and as a workshop. Getting electricity to it from the house to run our Shopsmith clone (a Totalshop) as well as lights (LED) and a window air conditioner would be dicey, so we've decided to go solar with it.

I've estimated the appliances to be about 600 watts: 500-550 for the air conditioner, 15 for the Totalshop, and 10 for the lighting (LED lights), and some left over for "breathing room". So now I have to size things, and the online calculators are giving different numbers. Basically I think I need a 125W polycrystalline panel (two 70W would also do), a charge controller - how big? for X batteries (I'd prefer to go 12V; all in series for better current?) and then an inverter. I think a 700-1kW inverter would do. But again, this is just what I have gleaned in my research and I'm not convinced that I have things correct at all.

Oh: we'd be using the workshop about an hour a day, maybe two, on average; maybe three out of seven days. This is only an average, though; some days we'll use it more, some days less. And, if the grid for the house went down, I'll want to be able to run a cord to my deep freeze.

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar PV System for Workshop

    Welcome to the forum.

    Can I say "rethink this"?

    Here's why:
    Shopsmith draws a very large amount of power as I recall. I don't know how you got 15 Watts; an ordinary circular saw draws 100X that. Air conditioner is another big power demand. By the time you've built an off-grid system capable of even starting those things you could pay to have the grid power run to the place.

    One 125 Watt panel? No chance. That won't even provide enough power for the lights. 1kW inverter? Will drop dead when the A/C tries to start.

    You probably won't believe me, so go buy a Kill-A-Watt meter and take some readings. See how much these things really use both at the moment (Watts) and over typical usage time (Watt hours). You will be surprised. Probably appalled.
  • Becca58
    Becca58 Registered Users Posts: 3
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    Re: Solar PV System for Workshop

    According to Shopsmith's page [ here ]:

    Amperage
    Mark 7 Model: 15A at 120V, 7A at 240V
    Mark V Models: 13.5 amps

    So that's where I come up with 15 amps for the Shopsmith. The air conditioner hasn't been purchased as yet, but the specs I've found says about 550 Watts. They don't specify the startup surge rating.

    Educate me, please.

    Edited to add: There's my math fault; 15 A at 120 V is 1800 Watts. *sigh*
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Solar PV System for Workshop

    That makes more sense.

    And as you can see needing to supply 1800 Watts is a whole other problem.

    You'll have a difficult time finding start-up surge info; manufacturers don't talk about it much and the Kill-A-Watt can't grab it. It requires a fairly expensive meter to measure. Rest assured it's been done around here, and the result are nasty.

    There's a lot of info about this sort of thing in the Energy Use & Conservation section: http://forum.solar-electric.com/forumdisplay.php?11-Energy-Use-amp-Conservation
    It's a lot of reading, but their A/C tests, refrigerator test, and tool test (somewhere) in there.
  • Becca58
    Becca58 Registered Users Posts: 3
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    Re: Solar PV System for Workshop
    There's a lot of info about this sort of thing in the Energy Use & Conservation section: http://forum.solar-electric.com/forumdisplay.php?11-Energy-Use-amp-Conservation
    It's a lot of reading, but their A/C tests, refrigerator test, and tool test (somewhere) in there.

    Off to do some reading, then. Thank you!