Solar powered A/C

[mrpincher]

Interesting discussion and thanks to all participants for your insights and knowledge. I am a teachable noob, one who can be easily led off into the wilderness.

It would be helpful to us on the sidelines if the total cost of these systems would be posted somewhere in the thread. Realistically, I have both technical limitations and financial limitations. It would be nice to know if total solar within my reach. $10,000 maybe $20,000 not possible. Again, please continue sharing your insights and knowledge.

[john61ct]

A fool's errand is an idiom for impractical, so difficult may as well be impossible.

No insult intended.

All LI chemistries but LFP are extremely risky wrt thermal runaway. Inherent in the chemistry.

Tesla puts lots of fire-prevention gear in place with its vehicles.

The battery modules removed from all that infrastructure just are not safe IMO to use for House storage.

Heck they're not even that safe inside a Tesla, as recent events and subsequent investigations have shown.

The large prismatic LFP cells from CALB, Winston GBS are the only safe and practical way to go but by the time you're done putting in BMS functionality 6-7x as expensive as quality deep cycle lead.

I don't see the battery weight/space issue to be a critical issue here anyway, solution in search of a problem.

Powering your aircon directly off a quiet little genny when the direct solar is not enough, is so cheap that there really isn't a good reason to bother with a huge bank that isn't going to do anything but help time-shift your runtime a couple / few hours anyway.

Best of all is just following the 60's, we've gone to all this trouble to be mobile. . .

[Ronnie]

I am here to learn about what others have done. Even if it pushes the limits, and even if I may not do it. I would love to NOT have a genny. Solar seems more and more viable these days. So those who have done a/c with solar, please more info. Right now it is out of reach for me, however in time maybe not, so I want to know all I can. After all it starts with a dream, then we find ways to make the dream come true.

[Twigg]

For many of us, there is no plug-and-play, or even mix-and-match system available for us to do this reliably.

However, some of the best threads are those where the participants are pushing the boundaries, and I applaud you.

[Whatthefak]

I've seen a few people running mini splits on solar, none in a mobile application, but it's not impossible.
I know it's out of my price range right now, but I would love to do it!
The idea of not buying fuel for a generator is nice.

I'm not sure why it's time shifting to run ac on a battery bank. If you have an efficient unit a decent insulation job and the kwh it should handle itself

[Twigg]

Originally Posted by Whatthefak

I've seen a few people running mini splits on solar, none in a mobile application, but it's not impossible.
I know it's out of my price range right now, but I would love to do it!
The idea of not buying fuel for a generator is nice.

I'm not sure why it's time shifting to run ac on a battery bank. If you have an efficient unit a decent insulation job and the kwh it should handle itself

All well and good in theory.

IN practise a bus is not as well-insulated as a house and is subject to wide fluctuations in internal temperature. We insulate to make the problem more manageable, not to eliminate it.

Where we might add 6" of spray foam to a home, for an R-Value of around 35, we get 2" in a bus.

Few people fit either the required amount of solar, or big enough battery banks and inverters to run it all. Doing so is horribly expensive and beyond what most consider to be money well spent. Especially when state parks are readily available with at least 30 amp hook-ups.

It's cheaper by thousands of dollars to run a small inverter generator, than it is to fit 3 to 5 kW of solar and the associated equipment.

Some do it, most don't.

[Whatthefak]

Originally Posted by Twigg

All well and good in theory.

IN practise a bus is not as well-insulated as a house and is subject to wide fluctuations in internal temperature. We insulate to make the problem more manageable, not to eliminate it.

Where we might add 6" of spray foam to a home, for an R-Value of around 35, we get 2" in a bus.

Few people fit either the required amount of solar, or big enough battery banks and inverters to run it all. Doing so is horribly expensive and beyond what most consider to be money well spent. Especially when state parks are readily available with at least 30 amp hook-ups.

It's cheaper by thousands of dollars to run a small inverter generator, than it is to fit 3 to 5 kW of solar and the associated equipment.

Some do it, most don't.

I agree it's beyond what I have to spend, I was just say it is doable, it's harder in a bus but it's done in homes and if you have the cash and motivation it can be done if someone really wanted to.
It's not just a time shift of when you run your Genny. Obviously there are limitations and you need a healthy budget but to tell people it can't be done just isn't true. If someone with more money and motivation to be off grid than me wants to do it, I really would love to see it. It's always cool to see someone do something that wasn't an option 10-15 years ago

[Twigg]

Originally Posted by Whatthefak

I agree it's beyond what I have to spend, I was just say it is doable, it's harder in a bus but it's done in homes and if you have the cash and motivation it can be done if someone really wanted to.
It's not just a time shift of when you run your Genny. Obviously there are limitations and you need a healthy budget but to tell people it can't be done just isn't true. If someone with more money and motivation to be off grid than me wants to do it, I really would love to see it. It's always cool to see someone do something that wasn't an option 10-15 years ago

The point about the "time-shift" comment was that unless the solar system can accommodate all of the power needs of the AC and everything else, you will still need external battery charging.

Normally, you'd run the genny at the same time as the AC (during the day, when it's hot), but with decent solar and big batteries you could run the AC for a good few hours just on that, but still need the genny at a different time.

[Whatthefak]

Seems to me if you loaded 40' of bus roof with new 300w panels you would have a stupid amount of power to play with.

That would be pricey, I know

[Twigg]

Originally Posted by Whatthefak

Seems to me if you loaded 40' of bus roof with new 300w panels you would have a stupid amount of power to play with.

That would be pricey, I know

... and it doesn't stop at the panels. You have the charge controllers and a battery bank capable of storing all that energy.

[Whatthefak]

Originally Posted by Twigg

... and it doesn't stop at the panels. You have the charge controllers and a battery bank capable of storing all that energy.

Agreed, I have no illusions that it'd be simple and cheap.

It's a complicated expensive mission, but not impossible

[john61ct]

Originally Posted by Twigg

The point about the "time-shift" comment was that unless the solar system can accommodate all of the power needs of the AC and everything else, you will still need external battery charging.

Normally, you'd run the genny at the same time as the AC (during the day, when it's hot), but with decent solar and big batteries you could run the AC for a good few hours just on that, but still need the genny at a different time.

Yes, pretty much.

Power put back into a bank - whether it comes from solar or a genny - has to equal the power taken out, plus 8-15%.

So, say your little aircon unit is very efficient and averages 600W in use.

While the sun is shining brightly, you could support that from say 1000W of solar, but that's without recharging batteries.

For every hour you run that aircon outside of peak sunshine hours, say you need 100AH of batteries, which in lead weighs 50+ lbs and costs $150.

So 12 hours' storage worth is 600# to carry and costs $1600 every few years.

And that's just storage. You 60AH*12hrs=720AH worth of energy needs to get put back into the bank.

Yes in ideal solar conditions, maybe an entire roof full of solar might be able to do so, sometimes. But when the weather isn't ideal, a genny will be needed to make up the difference.

Understand, I am in no way saying all this is impossible.

I'm saying most people will find it more **practical** to scale back their expectations, and / or simple move their dwelling to cooler altitudes/latitudes when it gets too hot for their comfort.

And all the rough numbers above are for very small and efficient units, not what you would need for most buses with windows left in place.

Anyone attempting this will get a **very** fast ROI on very thick tightly installed insulation, say 4" especially in the floor.

Might even be practical to seek out a reefer truck to convert rather than a bus.

[Whatthefak]

That is about the weight and price I figured on for my battery bank, and I'm not really planning on running ac much if at all, and I plan on a generator.

Unless I can snag a bout load of li on the cheap, which I doubt

[aaronsb]

I think it's just totally going to be up to whatever someone wants to do, practical or not.


Here's what we've got:

🗸 3 inches of insulation on walls and ceiling
🗸 5 inches of insulation on floor
🗸 double pane windows
🗸 152 square feet of solar panels
🗸 bigass lithium battery
🗸 bigass hybrid split phase inverters
🗸 mppt solar controller
🗸 battery safety: fire supression, thermal management, charge management
🗸 22 seer minisplit A/C units

Even when you model moderate to crappy insolation, the numbers distinctly go from time shifting a supplemental generator to simply time shifting solar harvest, which is exactly what we wanted.

Originally Posted by john61ct

Yes, pretty much.

Power put back into a bank - whether it comes from solar or a genny - has to equal the power taken out, plus 8-15%.

So, say your little aircon unit is very efficient and averages 600W in use.

While the sun is shining brightly, you could support that from say 1000W of solar, but that's without recharging batteries.

For every hour you run that aircon outside of peak sunshine hours, say you need 100AH of batteries, which in lead weighs 50+ lbs and costs $150.

So 12 hours' storage worth is 600# to carry and costs $1600 every few years.

And that's just storage. You 60AH*12hrs=720AH worth of energy needs to get put back into the bank.

Yes in ideal solar conditions, maybe an entire roof full of solar might be able to do so, sometimes. But when the weather isn't ideal, a genny will be needed to make up the difference.

Understand, I am in no way saying all this is impossible.

I'm saying most people will find it more **practical** to scale back their expectations, and / or simple move their dwelling to cooler altitudes/latitudes when it gets too hot for their comfort.

And all the rough numbers above are for very small and efficient units, not what you would need for most buses with windows left in place.

Anyone attempting this will get a **very** fast ROI on very thick tightly installed insulation, say 4" especially in the floor.

Might even be practical to seek out a reefer truck to convert rather than a bus.

[Twigg]

Originally Posted by aaronsb

Even when you model moderate to crappy insolation, the numbers distinctly go from time shifting a supplemental generator to simply time shifting solar harvest, which is exactly what we wanted.

If you can make this work, that would be awesome.

We will want a full write-up, with pics and all the equipment used ... That would help anyone following in your footsteps, enormously.

[john61ct]

Yes entirely doable with that sort of budget and commitment.

Maybe not cooling the whole bus all night off the bank with a 30° temp differential, but certainly closer to S&B comfort expectations while off-grid.

An LFP bank with a powerful DC gennie running for an hour twice a day would also get there, and combining both approaches would be ideal.

Given my own budget limitations, I'll follow the 60's.

[nanoplane]

I'm putting solar and mini split in my bus conversion right now..

I have 20 x 100W, flexible panels on the roof (about $150 each).
2 x midnite solar charge controllers (about $500) each
4 x 200AH AGM batteries (about $350) each.
1 x 3kW AIMS inverter / charger (about $800)
plus about $1k of wire and fuses and breakers and switches..

I'm rather ambitious...
I'm installing a 9K BTU inverter mini split system that flat out uses about 800W.

my refrigerator uses only 70W when it runs.. I expect overall, probably average 1/2 that on a daily basis.

Cooking consists of an induction cooktop (2KW max) and an inverter Microwave.

Haven't got everything hooked up yet, but...

[Twigg]

Very clean looking installation.

[kazetsukai]

Solar AC was a requirement for me, but I guess I'm not a "normal" bus converter... I kind of like electrical work, and in my design I've divided my electrical into 4 separate (isolated) Tiers.

Tier 1 is the 12V bus electrical. Aside from gutting all the unnecessary junk, I'm leaving this alone. Negative is grounded to the chassis as from the factory.

Tier 2 is my workhorse, it consists of 6x 100W Renogy panels mounted to the passenger-side of the bus, with 4x 100Ah 12V AGM batteries for 12V DC. I'm converting most of my electronics to use DC power supplies, all my lighting and automation is 12V. Pure DC, no inverter. I use a 40A Renogy MPPT charge controller for the panels. The system floats is not grounded to chassis).

Tier 3 is the big one I'm working on right now. 3kw of panels planned for the roof, 20kWh+ in Tesla batteries, and a Victon Energy 100A MPPT charge controller. This is for my 24V DC, 110V and 220V AC runs. I was planning on 220V for the mini split(s) and an electric dryer. May share negative (DC) with Tier 2, idk.

Tier 4 is automation. Everything is controlled by computer via relays.... The idea is, when I'm in the pilot seat, I don't want to have to get up for _anything_. I want to be able to see, and control- the state of everything in the bus from anywhere in, around, or away from, the bus via a screen with a browser.

Sounds complicated, but its actually simplified my electrical runs- I run any physical switches separately from the power to the appliance.

Anyway, I'm not approaching solar from a cost-effectiveness standpoint, I'm approaching it from a functionality/requirements standpoint. I don't want to run a generator, ever, I'd like be able to run the AC for a little while each day, and I want my clothes dry and warm. Not hard. I estimate cost for the whole system around $8k. Say what you want, to me the no-hassle solar is way preferable to the alternative.

[john61ct]

To me it's silly to be overly dogmatic about a genny, especially if you're planning on living off-grid for long periods of time.

A cheap almost-silent fuel-sipping little inverter genny can really come in handy, even if you use it only 20 hours in a year.

It gives you the flexibility to camp deep in a dark forest rather than always having to park out in full-sun spots. Or spend the winter in northern latitudes when insolation rates are cut by 80%.

And more importantly, it will ensure your expensive bank gets back to 100% Full at least a few times per week, even in suboptimal weather conditions.

Which is **critical** to batt longevity.

Being dogmatic "never burn fossil fuel" will require wasting a lot of money on that last 20-40% of solar and carrying a lot of dead lead weight around both of which you won't need 95% of the time.

And replacing that too-big bank much more frequently than you'd need to with the genny.

All of the above is true even if you only consume 100AH per day.

Putting ANY DC-powered aircon into the picture makes it all 100x more true.