Using supercapacitors to run a machine shop?

Hi all, new here and seeking help.

Let's assume that cost isn't an issue for a very hardcore enthusiast. There is a plan to create a machine shop that will be utilized part-time, working with steel and aluminium. About 20 hours per week plus perhaps a couple of hours of miscellaneous usage...

If we wanted to create a machine shop utilizing most of the basic tools - CNC, lathe, drill press, vertical/horizontal saw, vertical mill, compressor, welder, etc., along with heating and heavy computer usage...

And this shop is to be run by a massive array of solar panels and supercapacitors for energy storage. What amount of energy would need to be stored for roughly a week (20 hours of typical machine shop usage) of use?

It can be pretty ballpark with some extra energy added just in case.

We're planning on using 200 Watt-hour storage capacitors that are rated to run heavy electric transportation, figuring that this will be sufficient for the details above.

The only thing left is figuring out a ballpark estimate of how much energy storage is needed.

Any help would be appreciated - thanks!

Edit: Just realized how little those capacitors held. They discharge at over 700 KW though which is insane. Instead, we'll be using 13.5 KWh banks with 5 KW continuous discharge capability.

Or better yet

If anyone here could share how many KWh they use per month according to their bill (and specify how many hours the shop is used per week), that would be great. Also info about how many machines are running would be helpful. Thanks again

Bah. Skip all that nonsense and set yourself up with a pebble bed reactor ...

To put it shortly: no

The budget will be upwards of a few hundred thousand dollars for the power system alone. I just need some monthly KWh usage by machine shops and hours worked per week if anyone is willing to share.

Thanks again.

Look, you can do this yourself without much trouble.
1) Identify the machines the shop will use. Don't forget lighting and heating.
2) Look up the voltage and current requirements for each machine. Compute full-load Watts.
3) Estimate "duty cycle" for each machine. Equivalently, hours of use per week.
4) The next step is obvious simple arithmetic. Sum of (power times duty cycle) gives you Watt-Hours. Convert to Joules or whatever floats your supercapacitor bank boat.

What we CANNOT do for you is figure out what machines you will use, nor what their duty cycles will be. There is a huge difference in power demand between an old 1.5HP Bridgeport mill and a 20-30HP vertical milling center. There is a huge difference in duty cycle between an all manual shop where you use one machine at a time and spend more time in setup than in cutting, and a CNC production shop where you are running full shifts at nearly full load with pipelined operation through multiple machines concurrently.

You asked for a ballpark estimate, and you are entirely capable of coming up with that number yourself. We are in a poorer position than you are.

If you DON'T KNOW what machines your power system is going to be supporting, find out.

The other question is, why? Several hundred thousand in supercapacitors and solar panels would be FAR better spent elsewhere- machinery, tooling, employees, IP, raw materials, etc.

Are you trying to work "off the grid"? Mass production of goods is not what you might call an ideal application of 'off the grid' operations, as it tends to increase all your costs almost across the board. Transportation (raw materials being shipped in, finished products being shipped out) obviously setup and establishing the business in the first place (stretching return-on-investment out many years further down the road than under normal conditions) plus employee access, non-electrical utilities like water, sewer, telephone, etc.

I'm assuming the point of all this is to build a "showcase" company- where the company and it's product comes separately from the 'showcase' of the self-contained power system. In which case the power system is the product, in which case one of the very first things you need to be able to do is calculate a given home or operations power load.

If not, then what IS the point? One does not spend several hundred thousand for no good reason.

Doc.

Why indeed. I'd just use the grid, but the choice isn't mine. There's nothing to showcase or anything even close to that nature, but the funding is there and it's not my decision to use it in such a way.

I'm not sure if 5 KW is even enough discharge for the applications... 1 hp is like 700-something watts yeah? The consideration was Tesla Powerwalls which have 5 KW continuous discharge. I guess if there's two independent Powerwall systems, then they could run separate machine "nodes" at 5 KW each..

Not sure what the extent of machine usage will be either - the idea this guy has is in its (very) early stages, yet he wants this power system, so my best guess would be to compare it to a machine shop's KWh monthly usage vs. hours worked per month.

So again, if anyone has any numbers for KWh monthly usage for their machine shop and lets me know what machines are being used, that would be great so I could get some grasp of comparison.

You'd better talk to "the guy" and find out exactly what machinery he plans to use and whether it will be just him or more than one guy working at a time. Otherwise this whole mental exercise is a waste of time.

There will be around 4 part time engineers for the project/s. It will be up to the engineers to devise exactly what machinery will be needed. The problem is that the power system takes a bit of time to setup - therefore it needs to be done before the engineers are hired and working. It's a bit of a dilemma.

This is why I wanted to see if I could get some monthly KWh usage out of some machine shops; I figured it would be a decent way to at least start some kind of approximation.

Currently as it stands, the best I've come up with is 3 power nodes, each holding 27 KWh, with a max discharge of 7 KW and a continuous discharge of 5 KW. This would give us access to 3x5 KW discharge so that there would be no power bottleneck.

But again, I'd really appreciate it if anyone at a machine shop has some data to share: the monthly KWh usage, hours worked per week, and what machines typically run during work.

Thanks again, sorry for how absurd the post looks!

I have a basic VMC and lathe. Both CNC, pretty standard. Both are rated at 30KVA. Air compressor at about half that. They are both about 30hp CNC's. Just doing a bit of figuring as explained above times the amount of hours a month and you should at least have an idea.

I don't know nearly enough if how you are setting this up will be affected by the way CNC's use power. If you enter a cut, have the TSC hit, the coolant pump turn on, have the air compressor turn on all at once you are going to get a pretty large spike. I have a 50KVA transformer that handles it fine. YMMV

Not sure how to help other than to give you the ballpark of the machines max rated KVA draw and let you run the usage numbers based on how you want to use them.

I'm retired and run a home hobby shop just for my own entertainment, no product and no customers.

I've:

1.5 kW of lighting
CNC Lathe with a 27.5 kW spindle motor alone
CNC Milling machine taking about 5 kW
CNC Plasma table on a 5 kW feed
along with manual mill, lathe, grinders, hand drills etc

Your 5 kW draw wouldn't even start my machines up let alone run them.

Spend the money on a decent diesel generator set !

cetvxs said:

There will be around 4 part time engineers for the project/s. It will be up to the engineers to devise exactly what machinery will be needed. The problem is that the power system takes a bit of time to setup - therefore it needs to be done before the engineers are hired and working. It's a bit of a dilemma.

Click to expand...

-It's not a dilemma, it's the cart being before the horse.

Sorry. No, I get it, you're trying to come up with a ballpark figure, something to work with while the plan is in development. Understandable and prudent.

The problem is it's kind of a "how long is a piece of string?" type question. Some people here might have a single mill and lathe, and may only operate during banker's hours. Others may have 25 machines running three shifts and spitting out parts by the ton.

Jaxian brings up another point- your ancillaries will be a nontrivial load as well. Most of the machines will require compressed air. A single VMC and small lathe can get by with a home-shop 60 or 80 gallon upright. 25 machines running flat out will need closer to a 60HP setup- and the power draw will be even greater if you add in a refrigerated air dryer.

Lights- a small shop with three machines will need less lighting than a high-bay warehouse with thirty machines. Air conditioning- if you want accurate parts, you can't just open the doors and let the breeze blow through on a hot day. Again, five machines in a 600 square foot room won't take up anywhere near as much power as 25 machines in a 5000 square foot space.

I think you'd be better off getting some individual machine numbers- typically straight from the manufacturer- so you can "build a number" as needed. Oh, you only think we need two machines? Well, here's the draw for one, so we just double that. Oh, the plan changed and now we need eight machines? We take that single-machine number and multiply it by eight. Etcetera.

That would probably do you better than asking a guy in a different state, with a different number of different machines, running them all on utility power, on a different schedule, and using his numbers to estimate what you need.

Doc.

Ok heres some numbers for you, have been tracking my own power use, i have 1.7Kw of grid tied solar here, but do to sun shine it typically averages less than 1kw, it makes about 1800KWhrs a year total. About 10Kwhr on a good summers day, barely 1Kwhr on a bad winters days. Few people realize a solar panels ratings are at a given temp under a given illumination, In the real world when you have that illumination panel temp rises resistance goes up and you lose about 1/4 or so of ratings. You will only see peak ratings on a sunny cool day with a totally clear sky and enough wind it stays cool.

Tig, single phase 200Amps inverter, peaks at about 4Kw input, maybe a smidgen more. Being inverter at non arc times usage is sub 200 watts.

2hp inverter powered Bridgeport at idle sucks about 400watts, its hard to get it to dray much over 1kw in anything except heavy drilling or hard face milling.

Harrison 11" lathe much the same as the mill.

Interesting bit is the KWHr, sure the welders double, but all my products have short welds, think less than 2" of bead length lots sub 1". Ergo its rare using the welder to actually consume even close to 1Kwhr per hour. The lathe and mill its easy to clear that magic 1kwhr a hour rate.

A typical day will rarely see me use more than 8Kwhr of electric too, worst has been 12kwhrs of electric a day. thats including lighting of 8x 49W FHO T5 tubes, though according to my measurements they only suck about 400W total. Ergo about £3 a day which is kinda irreverent on the daily bills scheme of things, will easily use far more than that in cutters a day.

IMHO your chasing the wrong thing going super capacitors, far easier to just use a large multi KWH traction battery bank. If your running VFD drives you already have some capacitance there on the dc buss and you don't have the typical across line start surges to deal with if you have just a couple of seconds of ramp time programmed.

The house and shop here shares the solar panels, my main electric meter runs both ways and unwinds when im generating more than i use with the solar, house and shop combined for a good 6 months of the year over the summer period i will more or less have 0 day time electric bill. This is were your real problem bites, here in the months of November - February i will generate next to sweat FA, 1-2% of installed solar capacity is kinda the norm over the colder darker winter months, This is a problem your really going to have unless your near the equator, Im about 52 degrees north here, and it would be the same with my panels any were around the northern or southern hemisphere at that latitude.

This massive drop in generation is your real issue, To maintain the same winter supply as i have in the summer i would need a 8x larger array, its not even remotely sensible to look at enough storage to get the the winter period either.

Equally understand your 200Whr super capacitor is less energy storage than even a small car a battery, a 100Ah car - lesure battery is 1.2Kwhrs of storage, Having a battery bank the sizes you would need made of super capacitors would also add the issue of how you plan to fuse it, few fuse would even be remotely capable of safely braking the peak discharge amperage in a fault condition. Your talking serious fractions of a stick of TNT energy levels available in the event of a short, this is not about fire prevention but serious explosive arc flash issues.

Solar panels are also constant current devices, the best charges mean power point track the panels outputs then boost or buck this to charge the battery, this gives you a good 20+% more charge - actually power on a typical panels output than simply dumping it straight into a battery - capacitor bank. Far cheaper to use a off the shelf MPP charge controler with std batteries.

cetvxs said:

There will be around 4 part time engineers for the project/s.

Click to expand...

Then why are you asking here ?...

You hired the WRONG engineers.

DUH

Last time I checked, it worked out to 1.21 Gigawatts.

Capacitors are great for brief high current needs, both load and charging. Accelerating a bus perhaps. In terms of volumetric efficiency, they suck and always will. Electrostatic fields are a lousy way to store energy. You need electrochemical batteries or maybe a big flywheel system.

I applaud any attempt to find alternative energy sources and I think solar has a bright future (no pun intended). I think the key word here is future however. I am almost certain that efficiencies will increase dramatically but I think running a machine shop on solar and capacitors is currently a real crap shoot. I have to admit, I am ignorant of "super capacitors" but unless the basic principle of a capacitor has changed dramatically I would be building a blockhouse to store them. As Adama said they are great at delivering a crap load of current very quickly and if the dielectric breaks down then you could lose your shop.

I think you people are using a little too much of the stuff you just made legal.

TOM

We run 50% Solar. But it would never keep the shop going, it's benefit is simply offsetting the Monthly Electric bill.

Don't ask me specifics, because I'm not an Engineer. IDK.

R