I have a 400amp 3-phase service to my shop. Has anyone tried running a service like this by solar power? We machine primarly between 8am-5pm (daylight hours) and most of the new homeowner systems are connected to the grid. I think that not only would it be benificial to the enviroment, but also to my wallet. Solar pays off in 8-10 years (home system) and it seams as though many people are trying to buy from so called GREEN companies.
Whats your spin?

I have a 400amp 3-phase service to my shop. Has anyone tried running a service like this by solar power? We machine primarly between 8am-5pm (daylight hours) and most of the new homeowner systems are connected to the grid. I think that not only would it be benificial to the enviroment, but also to my wallet. Solar pays off in 8-10 years (home system) and it seams as though many people are trying to buy from so called GREEN companies.
Whats your spin?

You don't give a voltage but if it is 240 then your service is 166 kVA.

Solar power is DC so you would need to synthesize your 3 phase with an inverter which will probably be about 95% efficient so you will need at least 175 kilowatts going in to get your 166 out.

Noonday sun puts about 1 kilowatt on the ground per square yard on a clear day.

Photovoltaic panels are not more than 15% efficient so from one square yard under the clear noonday sky you get about .15 kilowatts which means for your 175 kW you need at least 1,167 square yards or 10,500 square feet.

But the sun is only at the zenith at noon and at either end of the day the energy arriving at the surface is reduced because the sun is low in the sky and your panels are not directly illuminated.

You could build an enormous tracking system but it might be just as cheap to double the area of the panels and leave them sitting still so now you need 21,000 square feet.

Have you priced photovoltaic panels? Have you priced a 175kVA three phase inverter?

I am not sure it would be benificial to your wallet.

Thank you for the input. I only have about 7000 sqft of roof on which I could mount such a system. The best I would be able to hope for (using your formula) would be an offset of my current electric bill. Even on the home systems that I have explored its not very cost effective until you figure in the State of NJ contribution, the Federal energy credits, and the small tax incentives. At this point I think I need to find out if the Grants and incentives are available to businesses.

Solar pays off in 8-10 years (home system)

And how long before you have to replace the system? Any degradation in efficiency during life due to dust or aging?

From what the Home instalers are telling me the system is good for 25 years. However it is degrading from the time of install.
I have a fair size shop (7500 sq ft), but I am in a residential area, so other types of energy (windmill, bio-diesel generator) wont be allowed by the city. Maybe solar has not progressed enough as of now to make it a good alternative.

From what the Home installers are telling me the system is good for 25 years...

I would take this with a large pinch of salt.

What about a natural gas powered generator system? There is not very much that it is possible to do if you want to try and operate more efficiently but I think one possibility is a co-generation system running on natural gas.

With this you generate electricity for running machines and use the waste heat for building heat. The efficiency of a genset running on natural gas is maybe 20 to 25%; that is you get that amount of electrical energy out while the remainder is dissipated as heat. If you need heat to warm the building with cogeneration you get it as a byproduct of generating your electricity.

You don't have to generate all your electrical needs, just offset as much as possible.

First thing you need to do, is find out if your electric company will make it on you, to get them to buy back your excess power. Some areas have laws, if not forget it.

You sell it back on the weekends. You use it, plus a little energy from the grid on the weekdays. You won't offset your entire electric bill, but with the right grants and tax breaks, you could at least make your company a little greener looking.

But, I suspect is will cost a lot more than just buying power off the grid. Geof's number are right on. Personally, I'd just keep my eyes open for a little longer. There's some tremendous scientific advancements being made in solar, I could see average efficiency climbing by 50%, and cost going down, in the next 5 years.

Wade

We have a 30KW pv on our shop roof ( 214 modules, about 3500 sf)powers 8 cnc's, grinders, drillpresses, welders etc. and our home.

Dear naytep,

Excellent advice by previous posters.

My two cents...

insulate your premises and forget about PV

Best wishes,

Martin

Just to drop my two cents. I read a national geographic article a few months ago that dealt with nano technology. Supposedly they are applying nano tech to solar panels and under lab conditions the solar panels are 3-4 times more efficient. The inherent problem of course is cost. It is not economically viable to use this technology in the real world yet, but in 15-20 years, who knows.

I think that I will wait it out a couple of more years. I just saw a show the other night on alternative energy. According to the show the current cost for PV is about $2.10 per watt. They were talking about cells that are printed on plastic sheet. These cells are formable, less directionally sensitive and the cost in 2010 is expected to be less than $0.20 per watt. I would feel like an ass if I blew $100gs on a system that I could buy for $20gs in 2 years. I think the time is coming, but its not here yet.

I agree with you there. On a slightly different subject. Our building sits next to a large pond/small lake which we use to cool and heat our building with. With tax incentives and grants, it paid for itself overnight, plus our a/c in the summer costs next to nothing.