Possible to power my shop totally off grid?

[rin67630]

RUC's agrarian shop is located in South Carolina, not in the Death Valley.
He didn't mention an air-conditioning equipment in his power balance neither.

 

[Hedges]

RUC's agrarian shop is located in South Carolina, not in the Death Valley.
He didn't mention an air-conditioning equipment in his power balance neither.

Touché

"Heat pump 4700 4500"

I took that to mean heating/cooling, and confused him with someone elsein a hot area.
If temperatures are moderate, outside (but out of the rain) is OK for Sunny Island.
If temperatures are below freezing, climate-controlled could be good for batteries.
Makes charging possible for Lithium, increases usable capacity for lead-acid.

And that's "either", not "neither"
(you should have said, "no" air-conditioning; then I would have let is slide)

 

[ruc]

The refrigerator surge I believe, because the 700W peak running is a resistive heating element. motor is only 200 to 400W.
Not so sure about well pump 4500. I would assume 5x 1600 for 8000W surge.
Garage door opener I don't believe 2350 running watts.
Air compressor, 8000W surge
Heat pump - what is the nameplate rating for refrigerator compressor? It may have resistance heating backup. If 4500 or 4700W is compressor running watts (believable for good sized system), then 20,000W or so surge.

2x Sunny Island would deliver 11,500W continuous from battery, 22 kW surge for 5 seconds.
Continuous power derates at higher temperature, down as low as 4400W at 140F, so good to install inside air conditioned space. (along with your batteries)

You can connect almost any amount of AC coupled Sunny Boy PV inverter, depending on how many Wh per day you need. Maximum with 2x SI6048 Sunny Island would be 4x Sunny Boy 7.7 kW for about 30 kW peak. With typical "maximum" PV panel array all oriented one direction, would produce 150 kWh/day in the summer. You could connect about 60 kW of PV panels with multiple orientations (Morning/Afternoon, or Summer Morning/Afternoon & Winter Noon) for more level power throughout the day and some clipping middle of the day, about 250 kWh/day.

If you have a generator, it will auto-start when batteries low, recharge, stop generator. That would let you have smaller battery and PV array. For instance, size battery bank for just one night instead of 3 days. That could be 1/6 or 1/12th as big, since most use is expected to be daytime.

Water heater should be enabled as a "dump load", to take excess PV production when nothing else needs power. Same for clothes dryer, but of course a clothesline is a practical alternative.

You could set up priority switching between major loads, if there is a problem supplying all at once. For instance, air compressor pressure control could be wired to interrupt heat pump thermostat. Both of those could interrupt well pump. Or, use a battery SoC signal to shed larger loads (Sunny Island has programmable relays for that), e.g. only run well pump at > 80% SoC.

With the maximum Sunny Boy PV configuration of twice the Sunny Island battery inverter, only half the power production can go to battery. The rest can be consumed as AC, or else production is curtailed.

Refrigerator doesn't need to run at night. A top freezer model lets cold air spill to the fridge. Smaller battery needed.

One reason I like AC coupled PV (besides highest efficiency for the grid-tied net metering which is most of my usage), is that battery can be arbitrarily small. I have programmed 80A (4kW) recharge rate, but have PV capacity several times that. During grid failure, my batteries recharge gradually in the morning and then float, while PV generated power is curtailed to supply that plus A/C and other loads. PV is much cheaper than batteries, so I waste excess production rather than trying to store more than one night's worth.

My system is similar to what I described except it has 4 Sunny Island for 23 kW from battery, half as much Sunny Boy. 20 kWh of AGM battery. My moderate climate doesn't need as many kWh for AC. Off-grid operation is infrequent, so AGM battery for 800 deep discharge cycles isn't used nightly, expect 10 year life.

I like the idea of a generator with auto start. That sounds like a good idea. I could definitely look at propane as a heating source. I think the heat pump would have about 8kw of heat strips. I can check to be sure.
It seems like the well pump is going to be the hardest thing to work. Would it be easier to set the well pump up as a stand alone system? I would rather not do that just to keep things simple, but if I have to I may consider it,

 

[rin67630]

You just need to define priorities, there is no need to run everything at the same time.
Make a list of what must not run 24/24. Night consumption from bateries are the cost driver #1.
The well pump does not need to run at night, does it?
The fridge possibly also not, if you have enough passive cold mass within (bottles of salt water are great for that).
Then consider an AC load balancer. Just to switch off what's not immediately needed.
Take in consideration that a heat-pump (the fridge, the air-con), possibly the well also, needs a grace time if switched off.

 

[Hedges]

I like the idea of a generator with auto start. That sounds like a good idea. I could definitely look at propane as a heating source. I think the heat pump would have about 8kw of heat strips. I can check to be sure.
It seems like the well pump is going to be the hardest thing to work. Would it be easier to set the well pump up as a stand alone system? I would rather not do that just to keep things simple, but if I have to I may consider it,

I think a single Sunny Island with suitably sized transformer for 120/240V would start and run the well pump. Two Sunny Island would be preferable, costs a bit more. About $5000 to buy 2x SI6048.

As rin67630 said, decide what to run only in the day, and what doesn't need to run at the same time.

You could wire some relay logic between controls, e.g. air compressor pressure switch, heat pump thermostat, well pump tank level switch. That would let one run at a time.
Alternatively, if Sunny Island(s) can handle the continuous load while batteries hold up, one of its relays could be programmed for 80% SoC, enabling those loads only when battery is well charged.

Size the PV array and AC coupled grid-tie inverters large enough, and loads will run during the day. PV production is simply curtailed to match load. It is cheaper to throw away excess PV production than to store it in batteries. Auto-start generator takes care of overcast times cheaper than large batteries. See if you can set up CHP, combined heat and power, where you capture waste heat from the generator for the house.

 

[ruc]

I'm still trying to figure this thing out. Since this is my garage/work shop, there will be days that I might not be there but a couple of hours. Then I might be there all day. Then I might not be there for two or three days. So I don't really know how to calculate the hours of usage.
Here is another question.....If I am not there for a few days and no power is being used, obviously the batteries would be fully charged, so what happens to the power produced by the panels?

 

[jasonhc73]

I'm still trying to figure this thing out. Since this is my garage/work shop, there will be days that I might not be there but a couple of hours. Then I might be there all day. Then I might not be there for two or three days. So I don't really know how to calculate the hours of usage.
Here is another question.....If I am not there for a few days and no power is being used, obviously the batteries would be fully charged, so what happens to the power produced by the panels?

Your batteries get charged, and then the inverter basically turns off the panels. They just sit there idle.

Go straight to SMA or any Top Tier name brand. Most consumer stuff is in the 5 to 15 KW range. It's very doable for your needs. SMA makes several 30, 4o, and 60 kW High Voltage inverters that are far more cost-effective than paralleling four or six Second Tier "residential" inverters.

Did you have any idea how much energy you need when it is dark? (How much battery? For me, I want at least 3x my entire day's need)

 

[ruc]

Your batteries get charged, and then the inverter basically turns off the panels. They just sit there idle.

Go straight to SMA or any Top Tier name brand. Most consumer stuff is in the 5 to 15 KW range. It's very doable for your needs. SMA makes several 30, 4o, and 60 kW High Voltage inverters that are far more cost-effective than paralleling four or six Second Tier "residential" inverters.

Did you have any idea how much energy you need when it is dark? (How much battery? For me, I want at least 3x my entire day's need)

I don't think I will need much at night. Probably would only be working until 9:00 or 10:00 PM or so, then go home.
For my battery calculations I would probably only need to allow for 1 day, I think.

 

[Rbertalotto]

Interesting thread......I would think a large, propane tank, running a large propane generator with all heat devices running off propane would be the way to go. A few years ago I built a 60,000 sq ft office building and researched using a propane turbine (jet engine) generator and backfeeding the grid with unused power. But timeline for the generator and overall maintenance just didn't add up. So I put two turbo charged, propane, 351 Cleveland V8s with 50Kw each on the roof for emergency power........

 

[ruc]

Interesting thread......I would think a large, propane tank, running a large propane generator with all heat devices running off propane would be the way to go. A few years ago I built a 60,000 sq ft office building and researched using a propane turbine (jet engine) generator and backfeeding the grid with unused power. But timeline for the generator and overall maintenance just didn't add up. So I put two turbo charged, propane, 351 Cleveland V8s with 50Kw each on the roof for emergency power........

WOW....My kind of man...2 turbocharged 351 Cleveland's. Now that is some serious horsepower !!

 

[Rbertalotto]

When we sold the building I wanted to climb up there and take them. They ran for one hour, every Monday for ten years.....520 hours total. The insurance company made me service them every 6 months. New Mobile One oil every 6 months and spark plugs and filters once a year. The oil only had 25 hours on it. We would take it and use it in our cars! Never used them in an emergency.......

 

[ruc]

When we sold the building I wanted to climb up there and take them. They ran for one hour, every Monday for ten years.....520 hours total. The insurance company made me service them every 6 months. New Mobile One oil every 6 months and spark plugs and filters once a year. The oil only had 25 hours on it. We would take it and use it in our cars! Never used them in an emergency.......

Great story !

 

[Jmac786]

I'm still trying to figure this thing out. Since this is my garage/work shop, there will be days that I might not be there but a couple of hours. Then I might be there all day. Then I might not be there for two or three days. So I don't really know how to calculate the hours of usage.

This is going to be a big deal in your design process. Do you work a regular 9-5 job? Night shift? Are you retired? Is this going to be more seasonal use?

For instance, if you work Monday-Friday and play in the shop on the weekends, then a large solar array might not be optimal. You could be better suited to go heavy on batteries (expensive) and light on panels (relatively cheap). A large PV array and an undersized battery bank isn’t going to work in this scenario if it rains all weekend.

 

[Hedges]

Batteries cost so much more than PV panels (about 10x the price, comparing $/kWh of battery life to $/kWh of PV amortized over a decade) that I'm inclined to over-panel and use-it-or-lose-it. PV panels cost $0.025/kWh, batteries $0.20/kWh or more.

As Jmac786 said, can't run PV direct to loads if the sun doesn't shine.
Are you willing to forego work on a rainy day?
Or how about a generator for those times?

I would suggest either:

Split-phase 120/240V, four Sunny Island 6048, 400 Ah (or more) 48V battery, Three or four Sunny Boy 7.7 kW PV inverters, each with 12kW to 20kW of PV panels in arrays aimed at 9:00 AM summer sun, 3:00 PM summer, Noon winter.

Current prices $2500 x 4 + $5000 + $2000 x 3 (or 4) + $5000 to $16000 (varies with brand and condition if used)

Or, 3-phase 120/208Y, 3 Sunny Island, 400 Ah or more, 3 Sunny Boy each with 12kW to 20 kW PV.

Generator would be either split-phase or 3-phase. You expect to consume 35 kWh over the day, so at least 5kW generator. Batteries hold 20 kWh (14 kWh usable), enough to smooth that out, and can take about 4 kW charging. 4x Sunny Island is 23 kW continuously, 28 kW for 30 minutes, 44 kW surge. 3x Sunny Island would be 3/4 of that. PV, when available, is added.

System cost $25k to $45k plus generator.

Enable loads like HVAC, water heater, air compressor and well pump only when battery SoC > 80%, or otherwise when surplus PV generation is available.

 

[ruc]

This is going to be a big deal in your design process. Do you work a regular 9-5 job? Night shift? Are you retired? Is this going to be more seasonal use?

For instance, if you work Monday-Friday and play in the shop on the weekends, then a large solar array might not be optimal. You could be better suited to go heavy on batteries (expensive) and light on panels (relatively cheap). A large PV array and an undersized battery bank isn’t going to work in this scenario if it rains all weekend.

I'm self employed, so I could be playing in the shop any time. That's what makes it tuff to figure out. Lots of time I would just be in there washing or detailing the cars and wouldn't need anything but lights. I do have a small office that I would like to have AC. Most of the time I don't need that much. But if I size it for the possible time that everything runs it will be expensive.
I really don't want to hook up to the grid, but I may not have a choice.

 

[ruc]

Batteries cost so much more than PV panels (about 10x the price, comparing $/kWh of battery life to $/kWh of PV amortized over a decade) that I'm inclined to over-panel and use-it-or-lose-it. PV panels cost $0.025/kWh, batteries $0.20/kWh or more.

As Jmac786 said, can't run PV direct to loads if the sun doesn't shine.
Are you willing to forego work on a rainy day?
Or how about a generator for those times?

I would suggest either:

Split-phase 120/240V, four Sunny Island 6048, 400 Ah (or more) 48V battery, Three or four Sunny Boy 7.7 kW PV inverters, each with 12kW to 20kW of PV panels in arrays aimed at 9:00 AM summer sun, 3:00 PM summer, Noon winter.

Current prices $2500 x 4 + $5000 + $2000 x 3 (or 4) + $5000 to $16000 (varies with brand and condition if used)

Or, 3-phase 120/208Y, 3 Sunny Island, 400 Ah or more, 3 Sunny Boy each with 12kW to 20 kW PV.

Generator would be either split-phase or 3-phase. You expect to consume 35 kWh over the day, so at least 5kW generator. Batteries hold 20 kWh (14 kWh usable), enough to smooth that out, and can take about 4 kW charging. 4x Sunny Island is 23 kW continuously, 28 kW for 30 minutes, 44 kW surge. 3x Sunny Island would be 3/4 of that. PV, when available, is added.

System cost $25k to $45k plus generator.

Enable loads like HVAC, water heater, air compressor and well pump only when battery SoC > 80%, or otherwise when surplus PV generation is available.

Hedges,
I like the idea of a generator to help. The generator could be used to help with the well pump and the air compressor.
I am a total newbe so that makes it hard for me to understand, but with a split phase system do you mean that there would be one solar system for 120V and a separate one for the 240V stuff, or would one system handle both?
Now when you mention the 3 phase system, you really blew my mind. how does that work? I thought 3 phase was for commercial. I once owned a carwash and the pumps were 3 phase with VDF which would ramp up and down as needed.













I once owned a carwash and the pumps were 3 phase VFD.

 

[Hedges]

"Split Phase" refers to the typical US household configuration of 120V for small appliances, 240V for big.
A center-tapped 240V transformer has the "neutral" center tap grounded. You can take 120V off either leg to ground, or 240V from both legs.
Split-phase load centers are cheaper.

Because each Sunny Island is 120V single phase, several can be linked together with a data cable, and the can be programmed for either 120/240 split phase or 120/208Y 3-phase. Sunny Boy PV inverter connects across either 240V or 208V.

That would run 3-phase motors directly. They would jump to full speed as fast as they could.
VFD can be connected to either 240V or 208Y. Better with 208Y because then it doesn't have to smooth ripple with capacitors.
VFD will give gradual ramp-up, no surge.

I had a problem with a 2 HP VFD on my pool pump when running off-grid with Sunny Boy 10000TLUS connected, the Sunny Boy gave an error.
It is a "transformerless" type. The new 7.7 kW Sunny Boy are transformerless as well. I'm swapping for an older transformer type 5000US.


Put generator on the AC input of Sunny Island. It will send a one-wire signal to start the generator when batteries get low. But that may rarely happen. Probably just let Sunny Island drive pump and air compressor. But it could be useful to have those shut off when too many other loads are running, or batteries are low. Battery state of charge can control a relay in Sunny Island. I'm not sure the best way to detect surplus PV. I know it is signaled by a shift from 60 Hz (increased frequency ramping from 61 Hz to 62 Hz tells Sunny Boy to ramp down production from 100% to 0%), but I haven't worked with any gizmos that use it to switch loads. I think 3rd party products are available. What I'd like is for VFD to linearly ramp up motors from 60.5 Hz 0% speed to 61 Hz 100% speed. Then it would regulate to just consume any surplus PV. Once it is at 100% if surplus remains, frequency would go above 61 Hz and Sunny Boy would then adjust production.

 

[ruc]

"Split Phase" refers to the typical US household configuration of 120V for small appliances, 240V for big.
A center-tapped 240V transformer has the "neutral" center tap grounded. You can take 120V off either leg to ground, or 240V from both legs.
Split-phase load centers are cheaper.

Because each Sunny Island is 120V single phase, several can be linked together with a data cable, and the can be programmed for either 120/240 split phase or 120/208Y 3-phase. Sunny Boy PV inverter connects across either 240V or 208V.

That would run 3-phase motors directly. They would jump to full speed as fast as they could.
VFD can be connected to either 240V or 208Y. Better with 208Y because then it doesn't have to smooth ripple with capacitors.
VFD will give gradual ramp-up, no surge.

I had a problem with a 2 HP VFD on my pool pump when running off-grid with Sunny Boy 10000TLUS connected, the Sunny Boy gave an error.
It is a "transformerless" type. The new 7.7 kW Sunny Boy are transformerless as well. I'm swapping for an older transformer type 5000US.


Put generator on the AC input of Sunny Island. It will send a one-wire signal to start the generator when batteries get low. But that may rarely happen. Probably just let Sunny Island drive pump and air compressor. But it could be useful to have those shut off when too many other loads are running, or batteries are low. Battery state of charge can control a relay in Sunny Island. I'm not sure the best way to detect surplus PV. I know it is signaled by a shift from 60 Hz (increased frequency ramping from 61 Hz to 62 Hz tells Sunny Boy to ramp down production from 100% to 0%), but I haven't worked with any gizmos that use it to switch loads. I think 3rd party products are available. What I'd like is for VFD to linearly ramp up motors from 60.5 Hz 0% speed to 61 Hz 100% speed. Then it would regulate to just consume any surplus PV. Once it is at 100% if surplus remains, frequency would go above 61 Hz and Sunny Boy would then adjust production.

This is going to be tuff. I don't know if I can do it.

 

[Hedges]

This is going to be tuff. I don't know if I can do it.

Can you install an electrical sub-panel, wire 120/240V circuits, put in a ground rod, connect wires to a motor that has instructions for both 120/240V?
That would cover most of the skills. If you understand volts, amps, watts, and "ampacity" or current rating of various gauge wire, those are the skills needed. If not you either have to learn or get someone with that knowledge of house wiring to do the electrical work.

Much of the labor is physically building racks and mounting PV panels.
My system is all metal conduit, so that was extra work. Most people use PVC.

There are all-in-one systems which are simpler - connect AC in, AC out, PV. But they wouldn't be large enough for you.
You can buy a "power panel" with several inverters pre-wired. That may be the way to go. With each inverter weighting 75 to 150 pounds, they may still be shipped separately, and you would have to hang each one on the panel, then connect wires in, wires out, and plug in a data cable.

I've seen panels for Outback that all the equipment mounted on.
For the larger SMA inverters, what I see is one box per inverter, which takes care of some wiring, but you still have to interconnect 3 or 4 of them:

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

 

[ruc]

Can you install an electrical sub-panel, wire 120/240V circuits, put in a ground rod, connect wires to a motor that has instructions for both 120/240V?
That would cover most of the skills. If you understand volts, amps, watts, and "ampacity" or current rating of various gauge wire, those are the skills needed. If not you either have to learn or get someone with that knowledge of house wiring to do the electrical work.

Much of the labor is physically building racks and mounting PV panels.
My system is all metal conduit, so that was extra work. Most people use PVC.

There are all-in-one systems which are simpler - connect AC in, AC out, PV. But they wouldn't be large enough for you.
You can buy a "power panel" with several inverters pre-wired. That may be the way to go. With each inverter weighting 75 to 150 pounds, they may still be shipped separately, and you would have to hang each one on the panel, then connect wires in, wires out, and plug in a data cable.

I've seen panels for Outback that all the equipment mounted on.
For the larger SMA inverters, what I see is one box per inverter, which takes care of some wiring, but you still have to interconnect 3 or 4 of them:

Category Products - MidNite Solar's

MidNite Solar Category Products.

www.midnitesolar.com

Yes...I can do all the "grunt" work, pull wires, and connect things up.
My problem is I am weak in understanding the electrical part. I know just enough to. probably get in trouble.
I also am having trouble getting my mind around understanding just what my needs will be and choosing the right equipment.

I have been looking at these auctions for the DC Solar mobile generator trailers. They have the Sunny Island equipment.
There is an auction going on now at Charlotte. The inspection day is tomorrow. That is about 1 hour away from me. I am thinking about going up there tomorrow and looking at them.
What are your thoughts on that?