Solar power for the shop

Factual Questions
1

I have a small workshop in my back yard which unfortunately doesn’t have power. I was planning to have an electrician run power out there from my garage, but I am sure that will be an expensive project. I was wondering if there might be a solar-powered option. I have a small forge there that I would like to power with a hair dryer (I don’t need the heat, just the blower). This will be run through a rheostat for air control. I would also like to power a shop fan and possibly an angle grinder or a hand drill. Is there a relatively inexpensive solar solution to my power needs?

Thanks,
Rob

2

Unfortunately, in the long run, just having an electrician run a wire out is probably going to be the cheapest solution.

For solar, your best bet would be to have an array of solar panels charge up a battery, then use an inverter to power your shop equipment. If this is only for occasional short term use then you might be able to get away with a reasonably priced solar panel, and your battery wouldn’t have to be huge. If you plan on working longer hours in your shop, though, you are going to need quite a few solar panels and you’ll probably need a bank of batteries.

You can get angle grinders and drills that run off of battery power. Charge them in your house and use them in your shop. That would reduce the power requirements since all you would need is the blower. A solar panel, a car battery, and an inverter might be enough for that. How big of a fan do you need?

3

I agree with engineer_comp_geek about the high cost to do what you propose with solar.

How far apart are the buildings? The loads you’re considering wouldn’t over tax an extension cord would it? Though I’m basing my experience on 230V, 115V will require twice the current; won’t 115V cords have heavier conductors to counter?

I regularly run 45 metres of extension cord to power stuff like a 100mm grinder, heat gun or 600W drill without noticing poor performance. Though I use what you’d call “Contractor grade” leads (expensive).

When we were building our cowshed, the arc welder was run through a light duty 30 metre lead. Of course the welding was only galv water pipe rails or concrete mesh. That was fun in the rain :rolleyes:

4

Even if you don’t overload the extension cord you could overload the outlet it’s attached to. Plus there are the usual tripping and shorting dangers that occur frequently when they are overused. If you look at the electrical safety statistics from most countries you’ll be dismayed at the number of fires attributed to extension cords. They are made for temporary use only and some are barely acceptable for that.

I think you should hire an electrician to wire the shop and defray some of the cost by digging the trench yourself. Codes vary by region on how deep to dig and whether mechanical protection is required but it’ll be done right and will be reliable. If you do go with an extension cord at least buy a good one.

5

If you go with an exrension cord make it at least a 12/3 cord and check the condition of the cord as you use for deterioration.

6

My roomie the blacksmith has a foot powered blower on her forge … she doesnt seem to feel the need for power=)

foot powered with a flywheel

hand cranked antique

7

My father just finished building his “yard barn” in their back yard. He had a couple of solar panels on it, a battery, etc. It’s enough to plug in the leaf blower or run a light while he’s in there (not sure what else he can do… that’s all he’s mentioned so far). Plus, he gets government rebates for installing “green” energy. It’ll also save a bit in the long run.

Check with your city/state and see if they offer tax rebates for solar panels. My parents have them not only on the yard barn, but on the house. Between the rebates and the energy savings, the panels have only one or two more years before they’ve paid themselves off. (my parents have had them on for just over 3 years.) After that, it’s free energy!

8

To clarify, the forge itself isn’t electric, is it? Because there’s no way in Hell[sup]*[/sup] that you’re going to run a forge on solar power
*Well, OK, you might be able to do it in Hell, but there’s no way in Earth you’d be able to pull it off.

9

I’d think you wouldn’t get much sunlight in Hell.

10

According to this site, you’d do better to try and run your forge in Heaven.

11

I’d seen the refutation based on the pressure of Hell before, but nobody ever seems to question the assumption that Heaven has the same albedo as Earth. Does anyone happen to know what the albedo of pearl is?

runcible spoon, are you saying that Hell is where the sun don’t shine? That explains why people are always saying that! :wink:

12

I couldn’t find anything for pearl, but wiki says that cloud albedo ranges from 10% to 90%. Nasa saysthat average Earth albedo is around 30%, but also that generally cloud cover is going to warm up the area below it, and cool off the area above, so, depending on whether Heaven is multi-level, we could be talking more than three times as much albedo effect than Earth.

13

An electric forge? I am going out on a limb and say he is using coal or propane. I happen to have both. It is much easier to have a fan blowing than using a hand or foot pedals.

As already said, it all depends how long your going to be out in the shop and using electricity. I say get a few estimates and get an electrician run the wire.

14

Well, I am just a hobbyist and I rarely spend more than a couple of hours in the shop. It is a charcoal fired forge run right now by a double bellows which I made too small and doesn’t work that well. The fan for cooling the shop is a box fan about 2 feet by 2 feet. I would only occasionally be running a drill or whatever off an outlet. Would a small solar panel connected to a battery and an inverter do the trick? I have run an extension cord out there, but doing so requires me to lock up the dog and I don’t want to have to do that every time I work.

Thanks,
Rob

15

Well it might work, if it’s only a couple of hours. Is it every day you’re using it?

Guessing some numbers
Fan 200 watts/hour
hair dryer fan 50 watts/hour
600 W drill for 10 minutes/hour = 100watts/hour
600 W grinder for 10 minutes/hour= 100watts/hour

So your talking 450W/hour which is 37.5 amps from a 12V battery, but as an inverter is about 80% efficient, it’s more like 47 amps. That’s a pretty major continuous load for a car battery. A 100 A/hr (not CCA) battery would be near enough totally drained over your 2 hour period, which isn’t good for it’s life. I’ve long ago tossed my text books but iirc max discharge of a lead acid battery ought to be to the 70-80% point, so a 100 A/hr battery is only good for say 25 A/hrs, so you’ll need 4 in //. As you’re not Government owned, so there’s no accountability to voters, 2 100A/hr batteries in // ought to give a goodly number of 50% discharge cycles.

As we’re talking about 2 batteries, you might consider a 24V system as the discharge current will be half, which is less hard on the batteries and will keep the terminal voltage a bit higher.

To charge, using a 120W panel, a data book shows a Pmax of 6.74A. To supply 100A/hrs will take well over 15 hours due to charging losses, say 20 hours? To charge a 24V system, 2 60W panels in series will give the same ~20 hours.

It’ll take longer anyway as the panel’s only pointed directly at the sun for a portion of the day.

Now if you’re only in your shed once a week, a smaller panel will work.

A charge controller is needed too.

Or forget the solar panel, and wheelbarrow the batteries back to the house and charge them with a decent multistage charger (bulk, equalise, float).

If your load’s a lot less, then the whole outfit gets smaller of course.

It’s been 25 years since I learned this stuff, so there might be some errors, which I’m sure will be pointed out :slight_smile:

16

Well, since you asked, Watts are already a per hour measure, so Watts/hr is either redundant or doesn’t make sense. I think you wanted just plain Watts. (a 600 W grinder at 10 minutes per hour will average 100 W). Amperes are also a per hour, so Amps/hr is similar; in this case I think you wanted Amp-hours.

As far as the substance goes, on a quick look I’m not sure that peak capacity might not be an issue, what with drills and grinders.