Questions About Will Prouses Beginner Friendly 48v system on Youtube. Load and Panels?

[Cipriano]

Hello Everybody,

New to solar and to this website. I am looking at setting up a glamping site with a 20' shipping container. I am wondering if the WP recommended system in this link would meet my needs.

It uses a Growatt SPF3000 TL LVM-48p with a single rackmount LiFePO4 battery. My needs would be:

1. Midea 8000 btu AC - 750 watts. Most of the day
2. LED TV - 4-5 hours per day
3. Blu Ray player - 4-5 hours per day
4. Floor Lamp w/ 3 60 w bulbs. 4-5 hours per day.
5. Microwave - Several minutes per day
6. Hot Plate - Several minutes per day

What do you think, yes or no? And if it's yes, what do you think a good panel array to match up with that system. I would like to use the top of the container, which is 8x20.

Thanks in advance for any advice!

edit: my location is 84720 USA

 

[Al D]

If you don't have a plan to insulate the container, you're probably not going to have enough sunlight to run your AC as much as you'll need. Also, consider thermally isolating a space for you to cook.

The 750W AC will likely pull around a 5kW surge. A 3kW inverter will typically support up to a 6kW surge. You'd be cutting it close if you had the microwave or hotplate going at the same time your AC kicked on. If I recall, the midea AC is somewhat unique in its power usage. You might be fine once the AC is actually on. I'm not sure. Someone with more experience using that model AC can maybe speak to that.

Your microwave will likely draw around 1.1kW - 1.5kW while actually microwaving. I don't know what your hotplate is, but heating elements are usually high power devices. I wouldn't use both at the same time.

I would make sure your wires are properly rated for such high current draws. You certainly are better off with the 48V system - good choice there. Don't forget the circuit breakers for the alternating current side of things. Also, you shouldn't use household wire if you've got a 3kW supply unless you run multiple lines.

Definitely check the local codes for doing this properly.

 

[Cipriano]

I would make sure your wires are properly rated for such high current draws. You certainly are better off with the 48V system - good choice there. Don't forget the circuit breakers for the alternating current side of things. Also, you shouldn't use household wire if you've got a 3kW supply unless you run multiple lines.

Ah, so the extension cord trick hooked up to the growatt wouldn't work with all these devices? I remember WP saying the 12 gauge extension cord is limited to 2000 watts (I think). Maybe I should look at a generator?

 

[Al D]

I could be wrong, but I think most extension cords that are rated to handle more than 1800W will have a different plug. There's something called a Nema standard. I would imagine a 12 gauge cord would have a different Nema plug than the standard 14 gauge cord. That means you might not be able to use the higher rated cord in your inverter unless it has an outlet matching the Nema standard.

 

[Cipriano]

Okay, so I've decided to go with this WP recommended system. I will forgo the microwave and I won't run the AC the same time as any other device.

Could someone please recommend me a panel array that would work? Max voltage on the Growatt is150 but I probably want to keep under that by at least 10%. So like 135v max. I'm a minimalist so less is more (the fewer panels the better). But I could go with more lower watt panels if that is beneficial.

Thanks!

 

[Cipriano]

Anybody want to take a stab at recommending a panel array to maximize the system in the first post?

I've never purchased panels before so I need some ideas.

 

[Al D]

Anybody want to take a stab at recommending a panel array to maximize the system in the first post?

I've never purchased panels before so I need some ideas.

It's probably best if you start with what panels you can actually acquire. Then we can work with how many you'll need. People find out that the shipping on panels are quite expensive. Since your preference is having less panels, it's unlikely you'll want to buy enough to significantly distribute the cost of shipping.

Also, without an actual power budget, we're really just guessing as to how many panels you'll need. However, here is an upper limit for a 10 hour stay in the un-insulated metal box during the warm months:
10hrs x 750W Midea AC
5 hrs x 60W LED TV
5 hrs x 20W Blu ray player
5 hrs x 180W light bulbs
0.5 hrs x 1800W cooking apparatus
TOTAL: 9.7kWHrs

Considering the typical household panels produce between 300W and 400W, and assuming you have 6 hours of sun at your specified location, you would need around 3-4 panels.

Considerations:
- You have no insulation. Insulating would help reduce your power needs.
- You have not indicated your plan for the colder months. Heating will also be required and potentially uses more energy than your cooling.
- Winter months means lower sun angles and therefore less power production. You might do good to have an extra panel.
- Panels degrade over time and, usually, power budgets increase likewise. Consider the future uses of your system while you're still planning it.

 

[Cipriano]

... in the un-insulated metal box during the warm months:

You make it sound so appealing! ?

Seriously though, thanks for the response. On FB marketplace near me, these are for sale for 150 apiece. Do you think 4 of these would get me going? Is it the VMP or VOC voltage I need to add up?

 

[Al D]

You'll do good with 8 of these. They are only 220W panels. I would try to get them for around $100 a piece. Make an offer for $800 for 8 panels and see what comes of it.

Realizing I told you that shipping usually costs a significant portion of the panels, you might look online for some. Right now, an Amazon seller has 2 new Renogy 100W panels for $160. So that's 200W of brand new panels for $160 instead of 220W of used panels for $150. Nothing against used panels, but for such close margins, it might make better fiscal sense. Potentially there's a waranty for the new panels... Or, do what I would do and ask for a better price on the used ones ?

Use Vmp (and Imp) for figuring out practical usage. Use Voc (and Isc) for machine safety. For example, your charge controller has a max input voltage. Use the Voc rating for that. And remember, most or all of these ratings are based on temperature. They change as the temperature fluctuates. Give yourself at least a 10% margin if you get close to the limits.

Edit: to be clear, I'm not saying to go with the Amazon purchase (or do if you like). But you should use that information when you bargain the price down. And go a step further and do a 5 minute search for some online deals. See what you find. Just make sure the shipping is factored in.

 

[Shimmy]

I would say to plan on 4h/day of PV, and you likely need a minimum of two batteries. Also, get rid of the 60W bulbs and go LED. By my math you need at least 14 of the 220W panels you listed. (You really would be better off buying bigger new panels at that price.)

10kWh / 4h / 0.85 Conversion Efficiency / 0.22kW = 13.37 panels

The specs don't show the temperature correction factor for Voc. This is an important number if you get cold temperatures.

For a 150V MPPT you would need to limit to to ~3S strings of the 220W panels, or 2S with larger panels, so you end up with either 3S5P on 220W or 2S3P with a 420W or higher panel.

 

[Al D]

I would say to plan on 4h/day of PV

OP is in Utah, USA. Peak sun hours are higher than most other states. In the winter, it seems 4 hours is somewhat accurate. However, the summer sun should produce 6+. Since there is no real power budget, the ~10kWh assumption was an upper limit estimate.

I agree that more panels would be prudent. However OP prefers the minimalist lifestyle and therefore would be less inclined to acquire 14 panels. I also agree that larger watt panels would be beneficial. The panels shown are what is available currently in the area.

These are all good points that OP should reflect on before making a purchase.

 

[Cipriano]

Please correct me if I'm wrong, but the MPPT in the Growatt has a limit of 145voc. There's no way it could support the number of panels you guys are recommending.

 

[NEpowerandlight]

You'll do good with 8 of these. They are only 220W panels. I would try to get them for around $100 a piece. Make an offer for $800 for 8 panels and see what comes of it.

Realizing I told you that shipping usually costs a significant portion of the panels, you might look online for some. Right now, an Amazon seller has 2 new Renogy 100W panels for $160. So that's 200W of brand new panels for $160 instead of 220W of used panels for $150. Nothing against used panels, but for such close margins, it might make better fiscal sense. Potentially there's a waranty for the new panels... Or, do what I would do and ask for a better price on the used ones ?

Use Vmp (and Imp) for figuring out practical usage. Use Voc (and Isc) for machine safety. For example, your charge controller has a max input voltage. Use the Voc rating for that. And remember, most or all of these ratings are based on temperature. They change as the temperature fluctuates. Give yourself at least a 10% margin if you get close to the limits.

Edit: to be clear, I'm not saying to go with the Amazon purchase (or do if you like). But you should use that information when you bargain the price down. And go a step further and do a 5 minute search for some online deals. See what you find. Just make sure the shipping is factored in.

You can get new 100 watt Renogy panels right now on sale from Home Depot for $90 each or $81 each with the military discount.

The nice thing about buying them from Home Depot for pick up at your local store is free shipping, and you can inspect and reject any damaged panels at the pick up desk. That makes shipping and dealing with damaged panels so much easier than from what I have read of people's experiences. Free home delivery is also offered.

 

[Al D]

Please correct me if I'm wrong, but the MPPT in the Growatt has a limit of 145voc. There's no way it could support the number of panels you guys are recommending.

The unit can take up to 80A of current. You would wire your panels such that the Voc in series is less than 145V and the Isc in parallel is less than 80A. Also note that the total input power is 4.5kW so the combination of panels should be within that range.

The panels you mentioned can be wired in sets of 3S, 2S, or 1S safely. Putting them in a 4S configuration is riding the rails and technically exceeds the Voc limitations of your device. You can check the datasheet if the MPPT has the ability to handle such a voltage, but keep in mind, it's usually best to have a bit of breathing room anyway.