Solar Power for a Wood Shop?

Solar panels or a windmill can supplement your shop's electric usage, but you're not going to run big iron on it without the grid doing most of the work.. June 4, 2012

Does anyone have experience with either partially or fully converting their shop to run on solar power? I have a full set of tools - CNC router, panel saw, edge bander, etc., and currently pay about $15k a year in electricity. With some of the rebates I'm wondering if it is feasible to convert.

Forum Responses
(Business and Management Forum)
From contributor Z:
We have a client who converted his house to solar power. Although he did receive some good rebates and tax breaks he couldn't get off the grid because the panels didn't create enough power to support his commercial kitchen. If you put panels on the roof and the parking lot and hopped on a bike connected to a generator you probably couldn't get the CNC through the startup process. There has been a recent breakthrough in solar panel technology that will allow a single leaf (4"x4") to generate as much power as today's standard layout (800sqft) but that probably won't be available for three to five years. Plus, don't forget that you need space for the converters and batteries.

From contributor H:
We have a 9.8 kw photo voltaic system on our building.

From contributor U:
I have been considering solar for when I make my next shop move. I have enough property to relocate close to my home and I can then stop leasing. My neighbor just went solar with their house, so I am getting some good insight into the realities of making this work. My first effort was to switch my heating and cooling over to a hybrid geothermal (open loop) system.

It did not work on my house, but I can see where it will work on my new shop. My shop will be around 2500sf, so a large portion of my utilities is heat and A/C. I am starting to see in my situation I can at least do a partial system combining solar with geothermal to cut down on my utilities. I just cannot afford to pay up front for a complete system, but if I can cut my bill significantly, I can reinvest any savings to increasing my solar capacity. Since I am building, I can face my building to maximize sun exposure which is a big consideration, unless you have open ground for placing solar panels.

From contributor A:
We run our shop and cabin off the same off-grid solar system. It is a 24 volt system and we currently have around $45k (including $5k in a generator) into it and it basically will run our house but the shop has to be supplemented by the generator. That's for the best batteries out there (Rolls), two inverters to run 220, 1ten solar panels, a small wind generator, charge controller, and a system controller. We love it, but we still have to spend money on the fuel for the gen set. Yes, we could buy more panels but I've found that even in the high mountain desert we get too many days that we are either fogged in, clouded in, snow, rain, etc. that solar can be unreliable.

We've been on the system for four years. It takes everything our system has (and it's a very good system) to start up my dual drum sander. I can't just go start it up, I have to sequence several switches inside the sanders control panel in order for it to fire up (think the movie Apollo 13 trying to conserve energy) and I have to go inside and say to my family "okay I'm using the sander so no water" so the well pump doesn't come on.

I can say for a one man shop it can be a rewarding (even if itís trying) thing to do. There's no way you are firing up a CNC, vac press, etc., off solar without spending at least quarter of a million upfront on your system. I'm way out there, a one man shop who doesn't ever want to grow (I tried that and it wasn't for me) and I'm also trying to prep for a one in four chance the country collapses, so for me it was worth it but I wouldn't recommend it for someone who wasn't in a similar situation.

From contributor H:
The size of the photo voltaic system needed to run a CNC router depends upon the CNC. I would have to agree that a huge and costly system would be required to run any of the heavy iron machine with 30 to 40 hp regenerative blowers. On the other end of the spectrum though is something like simple ShopBot machines that would easily run on a system like ours. We run our 5x10 CNT Motion machine with a 10hp HSD spindle with no problem, although I will confess I haven't examined the electrical meter for power flow direction when the router is running at 1P.M. during peak sun on a clear day.

From contributor A:
Your panels aren't running the machine, they are simply bringing in DC power that is then converted to AC. You can do it because you aren't off grid. You are simply somewhat supplementing your grid-tie in power. Trust me the inverters to run even a Shopbot machine and vac system off of a totally off grid machine will cost you an arm and a leg. The start-up amps on that are tremendous.

From contributor U:
Contributor A - is the wind generator worth having? How much of the 45k went to the wind source? I do not see any wind turbines in my area, nor do I believe that we have enough wind in my area to even consider this as an energy source. My initial goal is not to get off grid, but to cut my utilities by half or more. We were shocked that just through being more conservative we cut our bill by 1/3 at home. I can see putting $25-30k into a solar start up, I just could not swing 45. By building my own shop, I plan to cut my overhead by $400 a month, but only after a two year period when I eat the building cost on the front end.

From contributor H:
To contributor A: You're right. If I'd just done a little math I would have seen we couldn't run our 10 hp spindle CNC on our system without a lot of support from the grid. Our 9.8kw system will only produce around 41 amps (9800w / 240v = 40.83a) at peak output (around 1P.M., clear sky, mid-July). Since our 10hp spindle draws around 7000 watts (not even counting significantly higher start-up draw) we aren't going to be running that under load along with our 5hp vacuum pump and our 5hp dust collector. You're right that the power just isn't there and I appreciate your making me think it through.

I do believe that a ShopBot class CNC with a small spindle (or Porter Cable router), a vac pod hold down system with a much smaller rotary vane pump than ours (we've successfully used as small as a 3/4 hp pump) and around a 3hp dust collector should start and run even on a small PV system such as ours. You might have to sequentially start the motors to pull it off due to start up draw but I suspect it would work. I base this on what I know I can run from my 5000 watt generator. With state and federal incentives our system cost less than $40,000.

With regard to your comment that it would take a 1/4-million dollar system to run a CNC I think this shows it can be done for a lot less, but probably only with a budget level CNC and the very large tax and rebate incentives that were in place when we installed our system.

From contributor H:
Now, the next phase of the discussion is based on the above comments in reality being somewhat theoretical. While I think that my 9.8 kw system could run a small ShopBot class router it would take a sunny day to do so, maybe even only mid-day in the summer when we have the strongest output from our five degree tilt system. This means that to run that machine at less than peak output times, or on cloudy days or at night I would still have to use grid power. This is the major short coming of solar panels.

To be able to run that small CNC any time would take a non-grid tied system with battery storage. I have no experience here but suspect it would take an extremely large bank of 12v batteries to be able to supply an inverter with enough power to satisfy the requirements of even a small CNC. Although I guess you could look at the Prius and compare the power requirements of a car and the battery they use to what a router would draw. Does anyone have experience on this side of the PV question?

From contributor A:
I can tell you for a fact that a 5000 watt gen set isn't even coming close to starting up that Shopbot, let alone the vac system and dust collection. Again it doesn't matter how many solar panels you have, that's only the supply you have to consider converting that DC power over to AC. Let's say you have a huge solar panel array and huge electrical needs, think to large 5" PVC pipes with a 3/4" PVC coupler (I know this coupler doesn't exist, but imagine). The coupler is the inverter and it is incredibly expensive.

I will tell you that for my 24" dual drum sander it draws 340 dc amps at start-up (70 dc when running) and I can just barely pull that off my inverters for start-up. My 5500 watt Honda gen set will put out about 80 dc amps. So if I want to run my sander for long periods of time (not off my battery bank) I must start it on the battery's inverters and then throw four switches at absolutely the same time in order to get the genset power to bypass the inverters and feed to the sander with it not missing even a half second of power.

You can run things because you are tied to the grid. Off course all of these problems are solved if you have a very large 20kw gen set that can be called on when demand is high (next on our list of items to get), but you are still paying for are not saving money.

Let me say this. I love my solar system, but I'm way out there and I'm about as independent as there is. So with that said, solar is incredibly expensive and the return is agonizingly slow. Trust me if this wasn't the case there'd be more of it out there. Unless you are in a similar situation (or have similar beliefs about what could be happening in this country) I'd recommend you spend your money elsewhere. You could take the same $40,000 or whatever you want to invest and invest it and you'd make more than you would on the savings from your solar system.

The wind generator is a small one (supposed to put out 30 amp hours a month). If you don't know what an amp hour is don't even consider purchasing solar until you've done about 80 hours more of research. The big ones (as big as you or I can buy) are supposed to put out 3000 amp hours, so while I don't have experience with one of those I can honestly say I wish I would have saved my $1000 on the wind generator unless of course you figure it's a great conversation starter! We do have wind generators not too far from us, but for these machines you have to be in a very windy area. If you don't consistently have 10 mph winds (and I don't mean blows for a little while every day, but all the time), they aren't for you. They are only for those located in just the right areas.

From contributor H:
To contributor A: Without the tax and rebate incentives none of the "serious" installation I know of would have happened. Even with these incentives the payback is on the order of nine to twelve years. I was told eight to nine but at current electricity rates it is easily twelve years. Now with natural gas being readily available due to the newer extraction techniques it looks like electricity rates will stay relative stable for the foreseeable future, which means longer payback of course.

I am located in northeast CT on a direct line between NYC and Boston, a very developed area. As such I had to justify the investment one way or another because even nine years is a pretty long payback period on an investment. I did it because I like the idea of making my own power so for me it was as much a personal statement as a long term investment. Without the incentives though I never could have justified it. Even with the incentives I had to consider the fact that it adds to the market value of my property in order to feel it was the right thing to do.

From contributor U:
Iíve been doing the research, but I still have plenty to learn. Not much local assistance here, my neighbor has to import techs from 2 1/2 hours away. I appreciate hearing these comments from someone with hands on experience. Half of my research time has been spent digging through the sales on solar that is so common these days.

I also agree that I could pay a lot of years light bills for the upfront cost of solar power, based at current rates, but these rates will not stay the same. If I was doing this for one or the other, my house or my shop, I probably would not consider it. I believe I can benefit more when I get my shop next to my house.

From contributor O:
If you assume they have a payback period of 12 years and will last 20 you're receiving about 5.5% return on your investment. Not a very good investment for a small company - but not ridiculous if it gives you personal satisfaction. I've sniffed around on this for my house off and on (don't get any tax credits in my state) so it's never made economic sense for me. One thing I have noticed is the packaged/installed deals are quite a bit more expensive than putting the whole thing together yourself. Installing yourself doesn't seem like it would be overly difficult but I would probably want to pay an electrician a couple hundred bucks to hook it to the grid.

Taxes might be something to consider also. If you do it for your business you can depreciate the panels but the electrical savings become, in effect, taxable (lowered expenses). If you do it for your house you would have to pay with after-tax dollars and wouldn't be able to depreciate the system but the gains would be after-tax savings. Also, the tax assessor might try to increase your property value by whatever the panels cost and increase your property tax by whatever your property tax rate is. I expect this would happen for either your home or your business.

From contributor A:
I bought my system halfway hooked up. By that I mean they hooked up all the controllers, inverters, etc. on a 3'x4' master board that hangs on the wall (it was shipped to me this way). It was then my responsibility to hook up my 12 two volt batteries (that way 250 lbs each) to each other and the panel, and hook in the solar panels (very easy), wind gen set, and gen set. Everything is labeled and if you can wire your shop or house (maybe not pass code, but things are operational and not a fire or electrical hazard) then you could hook this up.

From contributor T:
Is there such a thing as a solar power DIY kit or can the components be purchased separately? I don't like the idea of paying third party installation costs when we could do it ourselves. I would get it commissioned by an electrician who would connect it to the mains. I would like to try it on a small scale for several years before investing heavily.

From contributor A:
Please do not go purchasing something here, something there, and then try and make it all work. It's not like house wiring where everything is designed to be single (or commercial three) phase 220/110v. You are literally talking about 48v, 24v, 12v, 6v off grid, grid tie, and etc.

From contributor D:
I second that opinion Contributor A. Unless you really know what you are doing, don't attempt to do it yourself. You will end up paying more in the long run and probably end up disappointed with the results. There are too many disparate elements to pull together to make a successful system.