What size of Generator would I need...?

[upnortheast]

You would be buggered at least 6 months of the year when there aint a lot of sun.
Lets say you need 20KW solar panels to make enough power when the sun shines That`s at least £15k. + a massive pile of Batterys ??
Sounds bloody expensive for an unpredictable supply
Imagine how pee`d off you would be if you had just set up an important welding job and the batteries went flat.
Just buy a decent genny
Unless someone knows different

 

[Selectamatic]

You would be buggered at least 6 months of the year when there aint a lot of sun.
Lets say you need 20KW solar panels to make enough power when the sun shines That`s at least £15k. + a massive pile of Batterys ??
Sounds bloody expensive for an unpredictable supply
Imagine how pee`d off you would be if you had just set up an important welding job and the batteries went flat.
Just buy a decent genny
Unless someone knows different

Hmmmmmm...

The theory was, that a 12V tractor battery, a decent one, 120Ah or the like would power a man size inverter, converting the 12V to 240V.

All I would need is a ring main circuit, and a couple of circuits for lighting.

The solar panel would not be a massive thing, enough to keep the battery charged.

If a single battery was not sufficient, connect another to it, that should be plenty...?

Not being argumentative, I don't know much about the subject, but from what I see, perhaps it would work?

 

[upnortheast]

I`m not an expert, but how long does a tractor battery last if the tractor will not start, - soon goes flat

 

[multi power]

Hmmmmmm...

The theory was, that a 12V tractor battery, a decent one, 120Ah or the like would power a man size inverter, converting the 12V to 240V.

All I would need is a ring main circuit, and a couple of circuits for lighting.

The solar panel would not be a massive thing, enough to keep the battery charged.

If a single battery was not sufficient, connect another to it, that should be plenty...?

Not being argumentative, I don't know much about the subject, but from what I see, perhaps it would work?

I know someone who has a inverter connected to his van, think it needs 2 batteries but it's EXCELLENT, grinder, drill, kettle all running off it, not sure it would run a welder but I'm sure bigger ones are available, and not too dear either

 

[Pheasant Surprise]

Hmmmmmm...

The theory was, that a 12V tractor battery, a decent one, 120Ah or the like would power a man size inverter, converting the 12V to 240V.

All I would need is a ring main circuit, and a couple of circuits for lighting.

The solar panel would not be a massive thing, enough to keep the battery charged.

If a single battery was not sufficient, connect another to it, that should be plenty...?

Not being argumentative, I don't know much about the subject, but from what I see, perhaps it would work?

It's not that it won't work, it will, and very nicely, but you're probably underestimating how many panels and batteries you will need for it to be workable - especially with tools and motors which will draw power like you won't believe.

I've done this on a solar electric gate with 2 x 150 w panels providing the juice to 4 x 100 Ah batteries (deep cycle jobs). It's amazing in winter how little useable sun there is and how quickly the batteries get drawn down even with a relatively small constant current, but getting drawn 24x7.

You could make a hybrid system - battery-solar-generator. That might work better in that you don't always need to have the generator running to have mains power, but use it instead to charge up a big bank of batteries, when the panels can't keep up - or when you need a lot of power.

 

[upnortheast]

If you could figure out how much your Kw max demand and regular demand was then the sums to work out how much kit you need should not be too difficult. Would you expect to do more welding in winter etc

1st calc is how much power needs generating
2nd calc is how much needs to be stored

 

[upnortheast]

Very rough guide of panel output South facing. 55 degrees North no shade. All depends on cloud cover.
av Kw per week - 30Kw of panels
Jan 200
feb 200
mar 400
apr 700
may 900
june 800
jul 900
aug 800
sept 600
oct 400
nov 300
dec 200

 

[Pheasant Surprise]

Very rough guide of panel output South facing. 55 degrees North no shade. All depends on cloud cover.
av Kw per week - 30Kw of panels
Jan 200
feb 200
mar 400
apr 700
may 900
june 800
jul 900
aug 800
sept 600
oct 400
nov 300
dec 200

That's probably reasonably close to the mark - so over winter production is effectively 1/4 to 1/5th of summer production. Which tallies with what I've seen on my little standalone setup. Some weeks I wouldn't get any net charge, so to make up for it you need to over spec your storage capacity by 3 or 4 times, unless you watch the whole thing grind to a halt - batteries don't like being fully discharged either - so I'd calculate use based on 80% of rated Ah.

The more I think about using a standalone solar setup to power even a modest workshop, the more I think you will need a generator in the mix - even if simply to run the welder without taking all the juice out the batteries.

Without knowing the exact usage and running the calcs - I reckon you'd want at least 1 to 2 kW of panel power (remember a fifth of that yield in winter....if your lucky).

Then you need a hefty solar charge controller and either one large or several smaller inverters.

The things which need sizing are:

- the inverter output (in watts) to satisfy peak load
- battery storage capacity (how long do you need to run your peak and average loads) to and also voltage config (a 48v or 24v setup will lose less, than a 12v setup an also need smaller cables as the DC cables can be smaller)
- the gross panel power, which determines how quickly the charge to the batteries can be restored.

 

[multi power]

How about a small wind turbine as well?

 

[TripleSix]

If you're going solar with batteries I'd use 12/24v lighting rather than running the lighting through and inverter which occurs losses.

 

[carpenter1]

Is there any preference between 1500 rpm and 3000 rpm generators?

 

[TripleSix]

Only tends to be smaller petrol units that run at 3000?

 

[carpenter1]

I thought I saw some diesels running at 3000

 

[Pheasant Surprise]

Is there any preference between 1500 rpm and 3000 rpm generators?

Most bigger diesel sets will run at 1500 because it uses far less fuel, is quieter and the sets last longer.

3000 rpm is the preserve of cheaper standby and portable sets.

 

[upnortheast]

If you're going solar with batteries I'd use 12/24v lighting rather than running the lighting through and inverter which occurs losses.

The OP talks of drills, welders etc etc

 

[TripleSix]

The OP talks of drills, welders etc etc

Yes, you'll need an inverter for those.

But have 12v lighting.

 

[upnortheast]

Anyone fancy playing with these numbers
Lets say this workshop has a demand for 500 kw / month.
6000 kw/ year
30kw panels produce 27000 / year
So 8000kw (to give margin) needs 9kw panels
Summer months circa 900kw production
Winter months circa 240 kw production
What sort of battery system would it take to carry the summer surplus to winter ?
Is it possible ?
Or should he keep it simple & buy a genny ?

 

[carpenter1]

Most bigger diesel sets will run at 1500 because it uses far less fuel, is quieter and the sets last longer.

3000 rpm is the preserve of cheaper standby and portable sets.

so if you can find a smaller at 1500 you would buy it over a 3000.

 

[Pheasant Surprise]

so if you can find a smaller at 1500 you would buy it over a 3000.

Like for like (price, power, sound level, etc) generally yes I would prefer a 1500 rpm set over a 3000 rpm - unless there was something else in the spec or make (or price) that swung it. Horses for courses..

Can you give some more details of what sets you're considering?

 

[carpenter1]

i was looking for a 6kv diesel to power a remote yard and 2 sheds
only needs to power lights, compressor and grinder i think.

looking at older lister types

as i would prefer this over cheap Chinese