Small Solar System for Mountains

[Nikg736]

We have a property in the mountains that seems to have power outages relatively frequently. Instead of getting a generator, I was kicking around the idea of installing a small solar system with battery storage. Much more environmentally friendly, might be used to reduce energy bill even when power is on, potentially eligible for some nice tax breaks. I'd also be looking to get some used components like panels and batteries (probably from Battery Hookup) to further reduce cost and environmental impact.
I'm sure some threads exist about sizing a system, so I will look for those (unless somebody wants to throw a few in as a response).
Main question otherwise is how to set things up to disconnect from the utility company and run on the solar/battery system? I'd want to be able to do this whether the power is out or if the mains are live and energized in order to make the most of reducing electrical consumption. Wouldn't be looking to sell power back to the utility (which I don't thin they allow in my area anyway). I'm thinking there must be some kind of simple way to disconnect the panel from the mains and switch it to solar/battery. Also, is there a simple way to set something up to run solar/battery as much as possible then automatically switch to the main power when that system is depleted to a certain level? Some kind of smart control?
Thanks

 

[leolvang]

The commonly used solution is to use a hybrid inverter and and a critical load panel in addition to the house panel. When the grid is off, the system is on battery, and you can not expecting the battery to energize every load in the house, just the critical load. If the battery voltage goes lower than setting, but the grid is back, the system can switch back to line mode and charge the battery.

 

[AnarchyJet]

The cost of used equipment is not eligible for the tax break. Your use case probably will never make financial sense compared to a generator. Who cares do it anyway...yeah solar!

 

[timselectric]

What you want is an off grid AIO. (all In One)
Everything you need is included in these units. Just add solar panels and batteries. It's input can come from your main service panel (grid). And it's output can feed a separate sub panel.
Move whatever loads you want. Into the new sub panel.
The AIO can automatically switch between grid and inverter/ battery/ solar.

 

[MTM98290]

About what.lattitude are you at? Winter can be difficult without lots of panels, If you have the room I would go ahead and install more than you think you need.

Having a connection to the grid is good for weak solar periods and at times of high demand. If a grid outage were to happen while batteries were low you still could need a backup means of recharging. A 20 LB propane tank is equivalent to 100 12v 100ah batteries so it does offer a lot of backup capability.

We have a 4500w inverter generator that runs on propane. It uses very little and burns very clean. I can put my hand in front of muffler outlet then immediately smell my hand and can detect no odor at all, trying this with any other generator I have owned would make me sick.

That being said it is really nice when it is quiet and all of your energy is being delivered by solar. Not having to spend money for fuel that may or may not be available when needed is great too.

 

[Nikg736]

The commonly used solution is to use a hybrid inverter and and a critical load panel in addition to the house panel. When the grid is off, the system is on battery, and you can not expecting the battery to energize every load in the house, just the critical load. If the battery voltage goes lower than setting, but the grid is back, the system can switch back to line mode and charge the battery.

What you want is an off grid AIO. (all In One)
Everything you need is included in these units. Just add solar panels and batteries. It's input can come from your main service panel (grid). And it's output can feed a separate sub panel.
Move whatever loads you want. Into the new sub panel.
The AIO can automatically switch between grid and inverter/ battery/ solar.

It sounds like you are both describing the same thing. I'm thinking these "all in one" systems are basically a box with a charge controller, an inverter and some kind of smart switch that automatically switches from grid to battery/solar when it senses grid is on or off. Correct?

Can one make an "all in one" better/cheaper from scratch, or is it better just to buy something pre-made?
Any suggestions on brands or vendors to buy from or stay away from? Is this an Amazon, eBay, Aliexpress type of purchase?

 

[Nikg736]

The cost of used equipment is not eligible for the tax break. Your use case probably will never make financial sense compared to a generator. Who cares do it anyway...yeah solar!

That being said it is really nice when it is quiet and all of your energy is being delivered by solar. Not having to spend money for fuel that may or may not be available when needed is great too.

Too bad not eligible for the tax credits, but I would do it anyway. No noise, little to no maintenance and reducing environmental impact take priority over cost for this particular application. And, yes, I would shoot to oversize the system a bit. The property is near Asheville NC, so it would get a pretty healthy dose of sun. And there is a south-facing slope that would be perfect for ground-level panels.

 

[timselectric]

It sounds like you are both describing the same thing. I'm thinking these "all in one" systems are basically a box with a charge controller, an inverter and some kind of smart switch that automatically switches from grid to battery/solar when it senses grid is on or off. Correct?

Not quite.
Grid-tied - turns all solar energy into AC power and sends it to your service panel. To be used or exported to the grid.
Off grid - take the solar energy and sends it to a battery storage system. And it can either be used or stored for later use.
AIO- is an All In One unit that has a SCC (Solar Charge Controller), AC charger, inverter, and transfer switch. All In One enclosure.
Hybrid - is a combination of Grid-tied and off grid.

Can one make an "all in one" better/cheaper from scratch, or is it better just to buy something pre-made?

From scratch, as in building the Electronics on PC boards, yourself? And putting them in your own enclosues?
Maybe
That's way beyond most peoples ability.
But an AIO is much cheaper than buying all of the separate (pre-made) devices. Installing them and connecting them together.

 

[Rednecktek]

Blurb time!

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

1: Power audit! This will give you some important information on how big your inverter needs to be as well as how much battery capacity you'll need. There is a link in the FAQ section (I think, or someone here will post it shortly) so fill in the blanks and see what it comes up with. You'll probably need some sort of Kill-A-Watt to get accurate measurements. Are you going to be running a 12v system? 24v system? 48v system? What are the specs on your solar panels? VoC? Vmp? Being as this is a new build, throw together a wish list of what you want and estimate on the high side.

2: Where do you live? Speccing out a system for Scotland is a LOT different numbers than Arizona due to the amount of light you actually get. Someone here can post the link to the PVwatts.com or JCR Solar Uber-Sun-Hours calculator sites to help figure out how much you'll have to work with. That will be a box in the Power Audit form.

3: Parts list: You don't need a make & model list, just a parts list to start from for reference. You'll need an inverter, a MPPT charge controller, fuses, shunt, buck converter, batteries, wire, etc. Once you have a basic list it can be fine tuned to make & models after that. If you're looking at the All-In-Ones check for correct voltage outputs (120v or 240v Split Phase for North America, 220v Single Phase for European type areas) and make sure it has enough capacity for a little bit of growth and fudge factor.

4: Budget!: Steak is great but doesn't mean anything if your wallet says hamburger. Figure out what you're able to spend now vs what you'll have to cheap out on now and upgrade later.

5: Tape measure! Figure out where you're going to stick all the stuff you'll need. A dozen 3000AH batteries sounds great until you're sleeping on the floor because there's no room left for a bed. Is there a compartment that can house all this stuff? Will the server rack batteries fit? Are you going to have to make space? Physics can be pretty unforgiving.

6: Pencil out what you think you need and throw it at us so we can tell you what you've missed (because we ALL miss stuff the first go-round ) and help figure out which parts and pieces you're going to want to get.

Well that's the thing about solar systems, there is no 1-Size-Fits-All answer. Your system will need to be designed to fit YOUR needs. When you design and built the system, it's not going to be the perfect system for me, or Will or 12vInstall or anyone else, but it Will be the right system for You and that's the goal.

Don't panic on the Power Audit, you'll actually be doing that a few times. When you do the first pass put in ALL the Things that you might want. AirCon? Sure. Jacuzzi? Why not. MargaritaMaster-9000? Go for it.

The second pass will be the "I Absolutely Need This To Survive" list that isn't going to have much on there.

The third pass will be the "This is what is realistic" audit that you'll use to design the rest of the system.

The Power Audit is going to tell you 3 primary things: 1: How big does your inverter need to be to power your loads? 2: How much battery bank do you need to last $N number of days with krappy weather? and 3: How much solar panel will I need to install to refill those batteries in a 4 hour day (the average usable sun hours rule-of-thumb).

Once you know what you Want and what you Need and what your budget can Afford there will be somewhere in that Venn diagram where those three things meet.

After that, THEN you can start looking at parts.

Yes, it's a long drawn out process, but it's worth it in the end. Not every house has the exact same floorplan, not every vehicle is the same make & model, and not every solar system is designed the same.

 

[Nikg736]

Not quite.
Grid-tied - turns all solar energy into AC power and sends it to your service panel. To be used or exported to the grid.
Off grid - take the solar energy and sends it to a battery storage system. And it can either be used or stored for later use.
AIO- is an All In One unit that has a SCC (Solar Charge Controller), AC charger, inverter, and transfer switch. All In One enclosure.
Hybrid - is a combination of Grid-tied and off grid.

Got it - I don't want grid-tied. Only want solar to feed essential house panel, never back to grid (which I don't even know if they allow here or not)

But an AIO is much cheaper than buying all of the separate (pre-made) devices. Installing them and connecting them together.

I didn't describe my intent very well. From scratch I meant buy the separate components and hook them together. I didn't mean to imply that I would be designing and soldering boards for inverters, SCC etc. I thought maybe buying a separate SCC, inverter and switch would be cheaper and more easily customized than having to go with whatever is commercially available

Blurb time!

Well, I'll start the default answer to these questions and we can work from there. Here's you To-Do list:

Thanks for all the info in your reply. At this stage the system would mostly be meant to run basics...fridge, microwave, some lights...that's probably about it. Maybe 24-48hrs maximum. So the system wouldn't need to be all that big. However, I do have room to upsize in the future as there is a basement with 9ft ceiling that has at least 50-100sq ft that could be dedicated to equipment.

I think a good starting point to determine sizing is assume fridge is running 75% of the day at maybe 400w and then just make sure enough wattage is available to run microwave (1000w) and a few hundred watts of lighting (we have all LED) and some simple low-power stuff like phone chargers. I've seen some 2400-3000w AIO units and thought that would be drastically under-sizing things, but now that I listed out the meager demands for this project I'm thinking that might be just fine. With fridge and microwave running that would leave another 1000-1500W for lights and other stuff. Could probably get away with TV, computer etc.

Here's my thoughts on the calculations for a 24hr outage:
Fridge = 400w x (.75x24)hr = 7,200wh
Microwave = 1000w x 0.5hr = 500wh
Other "stuff" = 500w x 12hr = 6000wh
TOTAL = 13,700wh (let's just round to 14kwh)

I'm not sure whether it is better to run 12, 24, 36 or 48v, but here are a few calculations for battery capacity assuming LFP chemistry:
14kwh/12v = 1166ah so let's just say 1200ah, so 4s12p of 100ah cells or 4s4p of 300ah cells
14kwh/48v = 291 so lets just say 300ah, so 16s3p of 100ah cells or 16s1p of 300ah cells

I'm sure there are losses in the system for efficiency etc, but the above calculations would basically assume total darkness for the entire 24hr period with no help from the solar panels. So assuming there is about maybe 600w - 800w of solar (two panels at 300w-400w each) and at least some sunlight during the 24hr period, then perhaps these numbers work out.

Do the above calculations seem to make general sense, or am I really off here?

Also, any recommendations for AIO units? Ones that are good? Those to avoid? Best place to buy/acquire?

For solar panels I'd scrounge FB Marketplace/Craigslist for used/refurbished unless somebody else has a good source.
For batteries I'd probably look at auctions at Battery Hookup because used cells at 80-90% capacity from an auction would still be 1/2-1/4 the price of new. I've got plenty of space, so even if I got 18-20kwh of "rated" battery capacity that produced 14-16kwh actual then that would be fine.

I don't really have a budget in mind, this is more something that if cost is reasonable enough that I would do it.
*3000w AIO = $500?
*Solar = $300 (I've gotten some before for this price, currently see 400w used panels for $150 each)
*Battery Storage = $1k-$2k (BH right now has brand new cells testing at over 300ah at $450 for 4 of them, so $1800 new. Might be able to snag a random auction for half that cost)
*Misc wires, connectors, breakers, mounting for panels, etc -- $400-$600?

Reasonable estimate = $2500?

Now that I look at the costs, I'm wondering if getting more solar and less battery would be more cost effective? I could get 3 of the 400w panels for same price as 300ah battery storage. Using 4 panels instead of 2 only adds $300 of cost but might allow for reducing battery cost by $400-$900.

 

[timselectric]

I didn't describe my intent very well. From scratch I meant buy the separate components and hook them together. I didn't mean to imply that I would be designing and soldering boards for inverters, SCC etc. I thought maybe buying a separate SCC, inverter and switch would be cheaper and more easily customized than having to go with whatever is commercially available

Understood.
Cheaper, no.
More customizable, yes.

 

[Rednecktek]

Quick pop in here,

An MPP or Growatt 48v AIO is a good option, they're reliable and well regarded. Go to Watts247.com for best results. They're also cheaper than buying the components.

600-800w of solar is too small. As a reference I have a 3kw AIO with 2400w of panel and some days were still a net loss on production VS used power. Panels are the cheapest part of a system so go as big as you can fit. Better to have too much power available in summer than not enough the rest of the year. 800w at 4 hours is only 3200wh and your battery is 14000wh, so 5 days to recharge if you don't use any power yourself.

Get as much battery as you can afford, you'll need it later.

Do you have any 240v needs like aircon or well pump or anything? That's a different inverter than a single 120v output. Both are available at 48v so plan accordingly right out the gate.

 

[Nikg736]

OK, so sounds like maybe 4-6 panels would be a bare minimum.
And as far as battery, I'd probably just keep my eyes on auctions and get as much LFP capacity for the buck as possible. It'll be in a basement, so doesn't need to be pretty or new, just needs to work and have a decent amount of charge cycles left

Is this what I need? Is this an AIO? The description says European only though

Clearance PIP-5048MKX 5kw Solar inverter 48v (European 230vac ONLY Not Split phase) 100A MPPT HIGH PV input 500V – Not returnable / TW support only – Watts247 Wholesale

watts247.com

The HVAC is heat pump and probably uses about 3k watts on it's own. Although that would be great, its well beyond the scope of what I would want to support. Well pump on the other hand...maybe.

 

[Rednecktek]

That 5048 is 240v european, you can't use it for american power without transformers and such. The 6048 should be 120/240 american power. The 6548 is also a well regarded 120v american unit. If you're going to need 240v for a well pump or HVAC unit, look at the 6048 or the EG4 6000xp unit. It'll give you 30a on each 120v leg and 60a on 240v for your big consumers.

 

[timselectric]

the EG4 6000xp unit. It'll give you 30a on each 120v leg and 60a on 240v for your big consumers.

I think that you are quoting the pass through amperage.

 

[Rednecktek]

I think that you are quoting the pass through amperage.

Nope, on the 6000xp it can put out 3kw on each leg of 120v, and 6000w total between the 2 legs whether it's coming from the grid pass through or the batteries.

Or at least that's how it's described and demonstrated by Will.

 

[timselectric]

Nope, on the 6000xp it can put out 3kw on each leg of 120v, and 6000w total between the 2 legs whether it's coming from the grid pass through or the batteries.

Or at least that's how it's described and demonstrated by Will.

Check the math.
6000w ÷ 240v = 25a

 

[Rednecktek]

My understanding of the video from Will was 3kw on L1 and 3kw on L2 for a total of 6kw.

@Will Prowse , you available to straighten us out on this one? Is my crack habit flaring up or am I following this correctly?

 

[timselectric]

My understanding of the video from Will was 3kw on L1 and 3kw on L2 for a total of 6kw.

That's correct.
Which is 25a, any way you figure it.

 

[Will Prowse]

My understanding of the video from Will was 3kw on L1 and 3kw on L2 for a total of 6kw.

@Will Prowse , you available to straighten us out on this one? Is my crack habit flaring up or am I following this correctly?

Yeah that's correct. Tim's right