Is Solar power the way to go?

[Michael_Minion_Can]

Hello, Myself and my Crew are discussing Running Solar or just generators, We are leaning towards Solar but Know nothing about it. We Would be running a Full Surround Sound Music system, A Air conditioning system, a mini fridge, Flood lights outside, a projector system and a laptop. We have no idea what to do and I'm Curious what anyone thinks.

~Michael

[Drop out]

Solar seems to make the most sense if you have pared down your consumption to near minimum and then add more than enough panels so you don't run too big of a deficit when conditions are not ideal.

AC off of solar is usually a losing proposition and it sounds like you have a lot more power usage than just that so I think you will be running your generator a lot.

If your generator is running a long time every day, buying enough solar to make a dent might be very expensive.

Going the other way with low consumption and lots of solar helps you stay off the grid while boondocking and you might only need an inexpensive little Honda as a backup.

[jazty]

What Dropout said. While running all those items off of solar CAN be done it will get expense. If you're going to live in your bus for 1.5+ years you will likely recoup your costs on a solid solar system and can enjoy the silence. If you're going out on weekends then you probably won't.

[mmoore6856]

solar ac has been done the key is super insulation so you can run a small ac

[brokedown]

Solar + Heat/AC is going to require a huge array of panels, a LOT of insulation, a huge battery array, and a very small heater and AC unit. And it won't' work if you have cloudy days, it won't keep you cool or warm while you drive, etc. If you don't already have it mapped out to the watt, you should start looking into more efficient and reasonable ways to control your climate.

[mmoore6856]

Im using propane for heat only need to run fan ill have a small back up 12 volt deep cycle charging system also. Can you give some numbers as huge is a relative term. How many watts can you get per sq. Ft? I ctunched them to my satisfaction and as i stated its been done.

[brokedown]

You can do some simple math. I've looked up a small AC window unit here:
http://amzn.to/2h39V6l

Now this is a pretty small unit, only 5000BTU. COnsider that an in-dash AC is likely to be nearer 25000BTU, and many buses have more than one unit!

This little guy claims to draw 450W while running. I'll be really generous and say that your insulation is good enough that it only runs 50% of the time in the summer heat of Imaginaryland, FL.

I'll also be generous and say you've bought a high quality pure sine inverter and you're only losing 15% of your power in the conversion process, which means you're pulling about 540 watts of DC to produce the 450 of AC.

The math is easy enough, 540 watts * 12 hours = 6480 watt/hours per day.

So that's the consumption side. Remember, I'm being really generous here! Let's look into generation.

To keep things fair, we're still talking about summertime in Florida, so we have a lot of sunshine. Being generous we'll call that 14 hours of sunlight, and through some miracle you're able to average 75% of your max panel rating across that entire period.

With those criteria, every 100W of solar panel is going to produce 1050 Watt/hours per day. To reach your 6480 figure you'll need 7 of those panels (7350 watt/hours daily). So that's the production side.

Storage is next. Following generally accepted best practices, you want to be able to handle a cloudy day here and there. This is a nice calculator to determine how much battery you need: https://www.wholesalesolar.com/solar...ry-bank-sizing and with my specs (6480 w/h usage, 1-2 cloudy days, 12v system using 200AH packs limiting to 50% depletion) you're looking at 1685AH worth of battery, which means 9 200AH batteries.

Now you've got about 800 watt/hours left over at the end of each day, which can go towards building your reserve capacity back up, and let you have a cloudy day once every few weeks... But let's be realistic here...

You're not going to meet all the generous levels I've thrown out, in some cases you won't even be close. You're also not going to use your solar just to power your air conditioner. Real world where you're not going for easy math you can expect to double this.

[mmoore6856]

So how does my friends system work for the last couple of years? He only runs his gen once in a while im doing what he did. Go troll somewhere else

[brokedown]

I"m afraid you've confused me with someone else if you feel like my post wasn't in good faith.

Your friend is doing something different if he's able to cool adequately with his solar, but you just said yourself that he supplements it with a generator. Math doesn't lie, even if you don't like the results.

[Drop out]

Staying cool somewhere in Florida with only 5,000 BTUs of AC seems like it would be a very very short bus.

With a 35-40' bus, I am looking at a 24,000 BTU dual zone mini-split AC unit, good insulation and most of the windows blocked off and I still think it will be a struggle to just be comfortable in the high 80s when it's 100° outside. I'll need about 2,000 watts of solar panels to run that on a good day and I'll want another 1,000 watts to deploy when it's not so good.

I won't be running flood lights a sound system or a projector, just a PC on occasion, a cell phone charger, a refrigerator, LED lights, ventilation fans, water pump and a TV.

Hopefully I wouldn't have to run a generator very often.

I don't have any crew but I doubt a crew would be good for your power consumption.

Hopefully for 8 months out of the year I'll be places where I don't need more than a little bit of AC every once in a while but during the other four months I expect a struggle unless I pay up for an RV park with plenty of shore power.

The flood lights, surround sound and projector sound fun but they are going to draw a lot of power when your solar isn't generating...

[Dog Rescuer]

I have been happy with a portable 10,000 btu AC unit in my bus - 28'. As long as I am not in direct sun, it easily keeps the bus at a reasonable temperature.
Before the Hurricane I had it under trees during 96 degree heat - and it stayed about 78-80 in the bus with the AC running. The back end of the bus stays a little warmer - but the exhaust fan helps a lot.
The next day it was about 95 - and I left the bus in the shade - no AC, just ran a box fan and opened a few windows - the bus never got about 84 degrees. I sat in it most of the day doing work - and it was never too hot.

I think the white (BusKote painted) roof helps a lot - I did not do any insulation inside the bus - except replacing the floor. I use Refletix on some of the windows.

If I did not have a Bernese Mountain Dog - I would probably not bother with AC - as I never had AC before moving to Florida - and seem to have survived. But, I have gotten use to the AC - so it will take some time for me to toughen back up a bit!

I was without power since Sunday night - and just got power back this morning. I stayed in the bus with my two dogs - and only used the generator a few times to take some of the heat out of the bus - other than that, we did pretty well with the 12V fans running.

Monday was mostly cloudy and windy - so it was beautiful, windows open - had a great breeze.

Tuesday was a little hot - so I ran the generator and AC for about 2 hours during the day - that was enough to take the edge off - and recharge the battery.

I will keep experimenting.

[brokedown]

Originally Posted by Drop out

Staying cool somewhere in Florida with only 5,000 BTUs of AC seems like it would be a very very short bus.

And that is exactly my point. My post was being very generous to the point of assigning magic properties to a little 5k BTU unit in an effort to demonstrate that the power needs are extremely high even for very little cold air output.

If it's something you don't use all the time, it's so much cheaper and easier to deal with a 2000W gas generator than adding 2000W of solar panels and storage.

I've got near 50k BTU in my short bus and its enough to keep the area behind the driver cool with a layer of reflectix covering the walls/windows/ceiling while we drive.. And if I drop to 1 unit I can generally keep cool while we're stationary if I close my thermal curtains that split the driver area off from the house area. But even with the insulation I have, the sun is a harsh mistress and my white painted roof can double as a cooking surface during the peak hours of the day, and some of that heat ends up inside the bus.

My point stands that relying on solar to cool your bus is almost never superior to a gas generator. AC is hard work.

[joeblack5]

It seem to me that if you want it to happen you will make it happen and if you don't then you won't. I guess people in Florida are keen aware that you can not tame nature. So you will have to go with the flow, if you can not do that and want to live at 74F in 105 F environment then there is already a flaw in the calculation to begin with.
2000 to 3000 watt on a 40 ft bus is not impossible and $0.50 / watt not expensive either. You can easily make ice during the day and release the cold during the night if you are not able to sleep with windows open and avoid expensive batteries, cold storage is more efficient to.
Sometimes it seems that before AC nobody besides the natives were living in Florida. Not sure how they did it.

later J

[Drop out]

Don't get me wrong, I want to try solar powered AC but when I budget for it, I come up around $10,000 for the solar, lithium batteries and inverter I would need.

I know that you can find solar panels at $0.50/watt but they aren't very efficient, which makes them big. 2,000 watts on a 40' RV roof would be tricky because it wouldn't leave much space for vents and your AC would have to be in the basenent (one reason why I am looking at a dual zone mini-split).

The panels I have been budgeting for are closer to $1/watt but very efficient and small so could leave me an aisle down the center for vents and a walkway. That aisle would also allow adjustable angle panel mounting so that in the winter (in Arizona) pointing due west I can tilt for maximum solar and my south side panels won't be shading my north side. That might let me save on propane heating so worth the effort probably.

Also they say solar panels need a few degrees of tilt so that they will be somewhat self cleaning when it rains.

There are lots of considerations and choices to make. If you are going to be full time living in a bus with lots of boondocking, $10,000 for solar is probably worth it in fuel savings, convenience and quiet but that isn't everyone's equation. Lead acid batteries, a cheaper inverter and less efficient panels could reduce the budget by a few thousand but if it screws up your roof access, weighs you down a bunch, self shades around the winter solstice and doesn't like the deep discharge of two consecutive cloudy days, your system isn't helping you out very much when you need it the most.

That's still a plan that doesn't include a projector, flood lights or surround sound, it just is enough to cover a reasonable amount of AC and my regular power usage without discharging too deep over night (so you have power left in the morning and increased battery life).

If you are planning for much more draw, I would start with that plan and improve on it with more solar and more kilowatt hours of battery. If you aren't thinking along those lines, you might end up running a generator several times a day and your investment in solar will feel like a waste.

[joeblack5]

Yep, like I said, if you want to make it work you will and if you want to make it expensive you can.
So my actual spending for solar looks very , very , very different.

3kw solar at 14% eff less then $ 1500
15 KWH lithium storage from salvaged chevy volt $ 1000
mppt charge controllers 4 pieces at $ 100 / each

Then lots of work and studying. $ ?????
I probably can rack up $ 7500 with the right hourly rate.

The solar will help you a lot with little leaks in the roof seams and more important the shading of your roof.

You are probably aware that you can walk on solar panels as long you stay close to the frame rails.

If you want to spend ?? on tilting mechanism please do, a lot cheaper to mount more panels. No use to tilt in winter, you do not need the AC and with 3KW you will plenty of power for normal..... whatever that mean....

You grid tie your bus to your home or shop and save some money and not die of CO poisoning, not the mention the horrible sound and vibrations that you probably can overcome with a good stereo combined with some anti noise canceling head phones.

I have done my house , our first camper, my first bus Elfie , working on Dory ,my second, and I can tell you ..NOTHING .. is as cool a solar panels

[PNW_Steve]

JoeBlack,

Please tell us more about that battery bank?

That has been the biggest obstacle for me in trying to come up with a realistic solar design.

[Drop out]

Here is where our budgets differ: I found a source for some 20% efficient Sunpower solar panels lightly used for a little less than $1/watt, I was budgeting $2,000+ for a DIY Tesla powerwall type battery bank, I budgeted $1,500 for a nice inverter and about $2,000 for the 24,000 BTU mini-split AC unit (which is the main reason for going big on solar). I figure there is another pretty big chunk of money for wiring, breakers, a 110vac panel, the basement rack, the roof rack, rearranging anything on the roof that interferes with the panels, etc. I'm pretty generous with that miscellaneous line item, maybe my total should be $9,000 but it sucks to start a $10,000 project if you only have $9k.

I am also interested to hear about your Volt battery. That might get my budget down to $9,000. You'll probably say I can use cheaper panels but that is $900 well spent in my opinion.

And by the way, if you want to full time in a bus and have no bricks and mortar house, grid tying isn't something you can do unless you rent a space at an RV park. That's a good reason for getting it done right and maximizing the output even during the winter when you might not be able to maintain a full charge and then you run in to a week with clouds and rain.

I'll try to avoid that last part by wintering in AZ.

I should have said this earlier but I'm glad to hear that 10,000 BTUs works well in 28' with out crazy insulation. The reason why I want a 24,000 BTU dual zone mini-split is that you get one 15,000 BTU zone for the living area and one 9,000 BTU zone for the bedroom. You don't have to run both at the same time (you might have to on a really warm day) and you don't have to cool the living area while you are asleep in bed. Doing it all with one unit gives you some flexibility and cost is not bad unless you are comparing to converted window AC units. I imagine that running 15,000 BTUs of AC with a compressor and condenser rated for 24,000 BTUs will be a nice easy life for the AC unit too. I will be planning on good insulation so hopefully the system I'm planning should have enough overkill so I mostly run my generator to make sure it's ok (every 2-3 months).

[family wagon]

Are there any figures available for the actual storage capacity of a used electric vehicle battery pack? Obviously it'll vary, and perhaps widely, but would it be conservative or would it be optimistic to hope for 10 kWh remaining capacity in that 15 kWh nominal pack?

[86Prevost]

Just finished putting solar on mine 5x 100 Watt panels with a 40 amp, 12 volt charge controller with battery monitor

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[86Prevost]

Originally Posted by 86Prevost

Just finished putting solar on mine 5x 100 Watt panels with a 40 amp, 12 volt charge controller with battery monitor

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The solars will charge the 5 battery bank that I installed and will power the 6000 Watt continuous inverter which will power my inverter. Should be a completely self sufficient system. If I need more juice I have a 6500 Watt continuous diesel genny as back up.

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