diy solar

diy solar

Fun experiment...

Lt.Dan

Solar Wizard
Joined
Dec 25, 2020
Messages
3,528
Location
Tulare, Ca
Hey guys, I'm just running the numbers at work because I'm bored. Not going to actually go through with (unless it really really makes sense?)

Our shop has several 240v and 480v - 3 phase machines/equipment and we average about 6000-7000kwh/month. Our biggest load is a 40hp 480v 3 Phase motor that powers our waterjet. Our AVERAGE monthly bill is $2000-2200 at roughly $.34/kwh after fees etc.

What would be required to get us totally off grid? We work Mon-Fri, 7am to 4pm, so we dont need a huge battery bank to run at night/ when there is no sun.

With my limited knowledge, I'm only really familiar with MPP AIO units, but the MAX 8kw unit that MPP sells is parallelable up to 6 units, capable of 48kw of output, and a surge of 2x that for 5 seconds. They are also configurable to 208v 3 phase, and I'm assuming we would use a transformer to go from 208v to 480v?

We also own an empty dirt lot next to us that could become a decent little solar farm. I'm assuming 60-70kw array would be in order.

Please teach me! lol
 
6000-7000kwh/month.
We work Mon-Fri, 7am to 4pm,
Lets call this 22days for 6500kWh = 295kWh / day
You'd probably want to spread panels facing easish and westish to have constant power. Will also assume your power requirements are equal all day long (you use the water jet all day, consistently?)
I will split this into 2 arrays for 295kWh / 2 per array = 148kWh
148kWh / 5h peak per array = 29,600W array in each direction (60,000W total)

60,000W array / 15W/sqft = 4000sqft of solar densely packed.

If you found 400W panels:
60000W / 400W = 150 panels
If you found a really good deal, maybe $250/ panel thats $37,500 in panels alone. With racking ballpark $50k total.

Break even on panels alone, if you cut $2000 from your monthly electric bill:
$50,000 /($2000 x 12) = ~ 2 years

Any idea what your MPP AIO units cost and how many of them you will need?

148kWh / 9h work day = 16.4kW continuous if evenly spread across the day.
You mention they run 8kW so you would need at least 3 running. Not sure how much surge current these big motors would have.
 
I came to almost the same exact numbers as you. I was figuring 6 of the 8kw units, 2 units per phase. Better to have too much available power because I know the startup of the water jet is very intense, as well as our press brake hydraulic pump. When the press brake pump turns on you can hear all the wires inside the conduit rattle and all the lights dim lol. I believe it runs on 240v alone though.

Idk the price of them, but the LV6548s are ~$1500/ea, so I would figure $2000/ea for the 8kw. Thats $12k extra in cost. Payoff is maybe 3 years then?

Thats not a bad deal lol.
 
Can anybody recommend other inverters/scc? Maybe something that won't require a transformer or something?

We actually are in talks about building a bigger building and moving... won't be a bad time to implement this entire system... a ton of 500 watt panels on the roof, a seperatw air conditioned room just for the hardware etc. How exciting lol.
 
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