Possible Dream Crusher- Need Help w/ A/C & Solar Please!

[Wright]

Let me begin by saying I'm new here, so I am sorry if this question is very repetitive. I've done a little searching and can't seem to find the answer.

So I am looking to get into the skoolie game (emphasis on looking). I am planning out a budget and possibilities right now before pulling the trigger (it's been a long time dream of mine).

After doing some research, I am doubting I'm going to be able to pull this off.. for one reason... A/C. See, I live in south Texas, and am going to be living in the bus full-time with the majority of the time being here, so no A/C is not an option. (Energy consumption for everything else will be very little.. I'm trying to make things as minimal as possible.)

I want the bus to be off-grid and on solar powered only. I would also like for the solar cost to be around $2k (definitely not exceeding $3k) in order to fit my budget.

So what are my options here (if any)? What kind of A/C units should I be looking for? How effective will they be and what is the cost? And what kind of solar should I be looking for? And what is that cost? (Side Note: I would also not like to kill the batteries by letting them drop too low daily.)

Anything helps! This is pretty much the only hurdle between me and living my dream. Thank you guys, very nice community y'all have here! Hope to soon be apart of it!

(Forgot to mention a few things that would affect the A/C. I am planning on getting a large school bus, around 77 passengers. I am re-insulated the walls, floors, and ceiling. All windows will remain and be unblocked, but the back 5 feet will be a separate storage room.)

[superdave]

if your running ac its best to be on shore power. solar and air conditioning don't like each other. if you dream of being off grid you would need to nix the ac and move with the seasons.

[JDOnTheGo]

As superdave said, running AC from solar is "difficult". In this case, difficult translates to expensive. It can be done but requires a massive solar array and a massive battery bank - preferably lithium. Depending on your AC needs, the solar/battery cost could easily exceed $30k. In that scenario, a generator and fuel to run the AC often becomes much more palatable.

You've probably already considered it but are their options other than AC (if you must stay in the area)? Good insulation, shade (some sort of whole bus awning/shade thing), and air movement (fans) can help immensely. No doubt that a hot/humid night without AC in Houston would be a tough thing for me (but I move to higher ground when that happens).

[Wright]

Most months would be bearable, but the summer months would be impossible without A/C. I can't leave either because I'm still in college here. I may still go through with the project, but only use it on the weekends to travel to cooler places.

Would something like this (3600W generator) power my A/C on top of other needs? https://www.steadypower.com/products...ckage-%28RV%29
Are generators reliable as the only power source? Or would I also need some solar?

[cadillackid]

AIr-conditioning takes energy... 3600 watts could probably run a couple of soft-start camper-top units, and definitely could run a couple 110 volt mini split units..

one of the reasons I NEVER camp is because of my wish for A/C and heat... and it seems at skoolie events generators are frowned upon.. out in the sticks anyones best guess..

you COULD look for a bus that has a built in separate diesel engine that runs electricity and A/C... run that on the worst days and nights and solar for the rest...

Off-Grid Living usually means sacrifice or big $$$.. alas why im such an On-Grid person.. not that it cant be done but its not super easy..

-Christopher

[Chevydude01]

Depending on the size of the bus and how much you are willing to compromise to make your dreams come true, perhaps a good insulation job, a small A/C and a very small generator. It could work if you are far enough out that none complains about the noise. If you design your bus right, lets say you build some sort of walled off bedroom in the back section of the bus and had a small window type AC, maybe running that off of a genny would work to keep the sleeping section at temp or something so you are not trying to cool a whole bus, I don't know just throwing stuff out there. There are tons of ways to make a dream come true if you think it out and want it bad enough.

[jonnichols]

Originally Posted by cadillackid

... and it seems at skoolie events generators are frowned upon..

This is quite unfortunate

[EastCoastCB]

I'll be using genny power in my bus.
Hip factor means nothing to me!

[joeblack5]

I am a little more positive about solar and AC. On my 5 window bus I have space for 900 watt. So a full size could be 2500 watt or more
I think the $ 30K mentioned is about someone else doing it for you.
In my last thread with Elfie we picked up a Chevy Volt battery that holds 16 Kwh, for long life 12 kwh. I paid $ 900. see images.
3000 watt solar can cost less then $1500. weight less then 400 LBS
4 mppt Charge controller at about $ 150 / each
Wire and frames / material can all be had from the scrapyard.
your labor free.
A cheap new split 9000 btu is about $ 400.
A used one $ 150

A nice new silent generator is also not cheap but a used harbor freight one is about $35

I think it depends where you are coming from and yes if you require to keep your bus in a 105 F environment and the inside on 65F with 6 cloudy days in a row then you will have a problem.
Everything has its limitation so very good insulation, get rid of windows etc. is all required.

If you believe you can do it then you can and solar is very cheap and very very pleasant.

Later J

[family wagon]

Originally Posted by Chevydude01

Depending on the size of the bus and how much you are willing to compromise to make your dreams come true, perhaps a good insulation job, a small A/C and a very small generator. It could work if you are far enough out that none complains about the noise. If you design your bus right, lets say you build some sort of walled off bedroom in the back section of the bus and had a small window type AC, maybe running that off of a genny would work to keep the sleeping section at temp or something so you are not trying to cool a whole bus,

It'll probably take a combination of compromises, and this one is a good suggestion. If only a portion of the bus is A/C sanctuary that'll be easier in terms of equipment (dollars) than A/C cooling the whole bus. Good insulation, thermal mass, and air infiltration/exfiltration will be important too. Sunlight shining through windows = massive heat gain, glass has terrible insulating value, and school bus windows aren't going to have any significant sealing against air leakage, so think long and hard about keeping those. Maybe the remainder of the bus can be kept bearable with fans and shade.

[bubb, the real one]

Yep,
I have the cab of the bus closed off, the 5000 btu AC unit above the windshield, at 100 degrees outside it cools to about 85 with blacked out windows, at night with the help of a fan it cools the whole bus.

[joeblack5]

Thanks Bubb, That is great reference data. Just checked your build thread, any further progress? You did not seem to have further insulated the ceiling? Do you feel any different ceiling temperature where the solar panels are shading your roof?

Later J

[StoneGuard]

I haven't built yet, so take my input with a bucket of salt. However, I too want Solar based AC and actually researched that before I even found out about Skoolies. Without the need for an inverter they are more energy efficient. I contacted a couple of manufacturers for solar, DC powered AC and heat pumps and got some great replies. Here's a transcript of an email I sent with the replies inline. Their replies are within the ***:

My question is one of feasibility for installation on an RV. I'm already planning a large capacity solar array with tilts for the roof, so raw power shouldn't be an issue.

The main question is can the outdoor portion of the unit be installed in a low cargo compartment (possibly replacing my RV's outdoor kitchen)? I would open the cargo bay before operation to provide ventilation, but it would effectively be installed in a space with walls on 3 sides. I'd then run the lines to the indoor portion of the unit at a midway(ish) point in the RV. ***Most people that do this have the unit mounted on the back of the RV or bus. Sometime on the side. you have to have enough room around it (at least 12-18 inches) around the sides.***

Second question: What is the weight of the unit? That's a big factor for feasibility. ***The outdoor unit weighs 110lbs. Indoor is 40lbs.***

Third: Any particular concerns about recovering condensed water for filtration and use? That might allow me to kill two birds with one stone when camping way off the beaten trail. The drain hose from the indoor unit should drain outdoors. ***I haven’t heard of anyone collecting the water for use.***

Solar & DC Air Conditioners | 48v DC Solar & Telecom Air Conditioner Heat Pump | Off-Grid Air Conditioning

Complete systems with Panels and Batteries included start at $4k, but for Texas I'd suggest looking at the heavy duty system for $6,300. Note these are actually heat pumps, so provide both cooling *and* heating. They are not however ducted systems, so for max effectiveness you'll want to keep interior doors open etc.

Additionally, I'm waiting till later in 2017 then I'll re-research this, as there is some exciting new battery tech on the horizon, including mass produced (read: cheaper) Lithium battery bank options ideally suited to running AC off of solar.

Here's a link to the other company I heard back from, but their website is less helpfull: Solar Air Conditioner | Evacuated Vacuum Tubes | Green Energy Innovations

[joeblack5]

Today while I was repairing the AC compressor clutch I noticed that it would not be hard to rig up a second pulley that is connected to the clutch disc spline. Would not be to hard to run it of a DC motor and see how good or bad it works. The condensor and evaporator / compressor are calculated for much higher cooling capacity then required while stationary. I would imagine that COP would be pretty good when running on 1/4 capacity.
What I read is that the automotive AC compressors are on purpose designed to be inefficient at higher engine RPM.
Any how the proof of the pudding has to come from an experiment.


Later J

[joeblack5]

looked up the efficiency curve of ac compressors



these are used in small buses but you can find a graph for your compressor. You can see that at 1300 rpm the efficiency gets a little less.
So at 1000 rpm the green one (tm13) is at 500 watt shaft power and a cooling capacity of 2.2 kw that would equal 7500 btu/hr.

Then there are losses in the drive belt and fans for the condensor and evaporator. Now he fans can be run at way lower power the normal because you use much less cooling capacity.
Any how I am not an AC tech and I hope others can chime in but it looks doable and a 600 watt dc motor is pretty cheap.

later J

[TAOLIK]

Have you considered using a swamp cooler? I was thinking for awhile about using a swamp cooler, and I still do think about it occasionally. But I don't know about releasing all that moisture in my bus. However, it would relieve a lot of wattage not using a compressor.

[Robin97396]

Swamp coolers work great in areas like Nevada where the air is dry. Not so great in Oregon and Washington unless you want more humidity.

[bubb, the real one]

I have a full length roof rack, 12ft of solar and 20ft of metal, I also have the top 5ft of the bus sides covered with metal with a 2in air space underneath, it stays darkin full sun it is 5 degrees below ambient inside

[bubb, the real one]

Just the original 2in of fiberglass in the roof, one inch of board jnsulation on walls by me, had no original wall insulation ,

[tobeamiss]

Originally Posted by joeblack5

I am a little more positive about solar and AC. On my 5 window bus I have space for 900 watt. So a full size could be 2500 watt or more
I think the $ 30K mentioned is about someone else doing it for you.
In my last thread with Elfie we picked up a Chevy Volt battery that holds 16 Kwh, for long life 12 kwh. I paid $ 900. see images.
3000 watt solar can cost less then $1500. weight less then 400 LBS
4 mppt Charge controller at about $ 150 / each
Wire and frames / material can all be had from the scrapyard.
your labor free.
A cheap new split 9000 btu is about $ 400.
A used one $ 150

A nice new silent generator is also not cheap but a used harbor freight one is about $35

I think it depends where you are coming from and yes if you require to keep your bus in a 105 F environment and the inside on 65F with 6 cloudy days in a row then you will have a problem.
Everything has its limitation so very good insulation, get rid of windows etc. is all required.

If you believe you can do it then you can and solar is very cheap and very very pleasant.

Later J

I like your positive outlook and calculations on this possible problem. I like solving problems and I, (like you), believe there can be a solution. You just want to have it bad enough. I'll be facing a similar situation when I'm through with my build, but I'll be in Sunny Fla. My dream is to be off-grid....eventually. I WILL make this work.

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