Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
 
Old 05-23-2021, 01:57 AM   #1
Traveling
 
Join Date: Aug 2016
Posts: 198
Maximum solar for 40' bus with standard solar panel sizes

Yes, I have searched on this topic, so let's get that out of the way. There were some interesting threads, but tech and prices have rapidly evolved, and I have new ideas.

My current working model is using two rows of 410w bifacial solar panels, one down each side, leaving a path in the middle.

These panels are said to be quite good in terms of winter performance, and since I have a white roof, so much the better for the back side component.

They will be aligned such that the outer edge roughly aligns with the edge of the bus, maybe a little over, because they will be at a slight angle, sloped down from the peak of the roof. They will be hinged on the top side and some sort of height adjustment on the down side so that the northern side can be elevated to face the sun.

I thought I had thought this up myself, but turns out others had the idea too, but I haven't seen a solid example of it being done.

Okay, dirty details: Panels are nearly 40" wide by 80.5" long, which means if I hang over the back a touch, I could fit six lengthwise on each side, but conservatively 5, if I want hatches or whatnot. That's ten total panels, easy. Bus is about 92 inches wide, but with the curved roof, I'm not sure exactly, but that would leave approximately a one foot wide walkway in the middle. Five in series would make two perfect 250 volt strings for two 250 volt charge controllers.

As to production, just assuming 6 hours a day of 4000 watts gives me 24 kWh per day, though these can be capable of over 500 watts on a cold sunny day, and cold is more of a concern. Let's face it, it's a little harder to die of being too hot, we are savannah animals after all, as long as we have water and shade, we're fine.

For batteries, I am looking at 280 ah lithium iron phosphate cells from China in a 48v pack. 12 cells is about 10 kWh, so probably two of those for 20 kWh of storage.

Both the storage and production are well above what I have clocked using in a full size house with heat pump and electric water heater in the past. I used to pride myself on using 12-15 kWh per day in a 1200 sf house. Nowadays, I have very little need for air conditioning, but also an electric car. One solid run on the electric car can wipe out 20+ kWh.

I also am thinking about solar panels on the roof of a car trailer but that's a one day dream.

I have a 6 kW diesel generator I might build in under the skirt, but also I might install a second 48v battery charging alternator on the main engine. The Broccoli Bus doesn't have a generator. Who knows, work in progress. I already HAVE the generator, and it was cheap, so why not.

WiredForStereo is offline   Reply With Quote
Old 05-23-2021, 08:22 AM   #2
Bus Nut
 
Join Date: Sep 2017
Location: Cerrillos, NM
Posts: 393
Year: 2002
Coachwork: Amtran
Chassis: Front Engine
Engine: DT466E
Rated Cap: 72
I don’t know much about the bifacial panels but I would assume the cost doesn’t justify the extra production, and the length of the bus *may* make 7 rows of 65” panels more effective overall. I think 6 hours a day is a bit of a stretch too, but that really depends on where you are. I saw a chart someplace that said to derate solar wattage 75% in NY, 0% in NM (the two places I stay) so location obviously really matters.

Lastly, the Chinese cells are 3.2v nominally so 48v packs have to be 16 cells or 32. 14kwh but really 11.5kwh usable per bank of 16.

Other than the little details I think it’s going to be a robust setup. You’re going to want a fan up there, or two, at least most people find, so I would consider leaving space for that or engineering my idea of using the school bus
flashing light locations as vents with four fans on the front and back.
rffffffff is offline   Reply With Quote
Old 05-23-2021, 11:11 AM   #3
Bus Crazy
 
kazetsukai's Avatar
 
Join Date: May 2017
Location: Athens, TN
Posts: 1,574
Year: 1999
Coachwork: Amtran
Chassis: International RE
Engine: International T444e
Rated Cap: 76
I have a 38' bus, using 10x 305W (not bifacial, don't see a compelling reason for them personally) panels I ended up with 3050W up top, ran out of roof space with my skylight hatches. Without them I could fit another two panels I think. Wired in 2S5P for around 90V, mounted flat.

My current daily record yield is something like 19kWh limited by the 10kWh 48V Tesla bank- it is full in the first two to three hours of charging during normal use, and the rest is what I can use in a day- AC blasting from the mini spit, TVs, induction cooking, etc.

Anyway I wanted more solar, so I'm in the process of building slide outs for about 6200W total. The reason I want more is twofold...
  1. For my new larger battery bank (3.2V 280Ah cells in 16S3P is 43kWh), I want a maximum "recovery time" (charge from empty to near full) of less than a couple days ideally.
  2. We have a 5th wheel and I anticipate having to power that too without access to grid power at some point.
Also anticipating towing an enclosed trailer with solar on it, although that will likely be an independent system for several reasons.
kazetsukai is offline   Reply With Quote
Old 05-23-2021, 11:34 AM   #4
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,358
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
I have eight 255W panels on my bus, in two rows of four on either side of a central roof walkway I built between the roof hatches. Each panel can be tilted to 21, 33 or 45 degrees up, and when the panels are down against the roof for travel they are at 21 degrees down. I'm keeping some space at the end for two water-heating panels that I'll make later, and these will also tilt similarly. I don't have photos of my installation, but there's a YouTube video called Buses Gone Wild VII where you can see my bus before I installed the actual panels into their hinged support frames. Everything's made from 6061 and 6063 aluminum, with stainless hardware and hinges and support struts, so nothing will need painting. I also put two quick-connect water outlets on the walkway so I can easily and safely wash down the panels when they get dusty or covered in bird crap.

So far, so good!

John
Iceni John is offline   Reply With Quote
Old 05-23-2021, 02:04 PM   #5
Bus Nut
 
Join Date: Sep 2017
Location: Cerrillos, NM
Posts: 393
Year: 2002
Coachwork: Amtran
Chassis: Front Engine
Engine: DT466E
Rated Cap: 72
Quote:
Originally Posted by Iceni John View Post
I have eight 255W panels on my bus, in two rows of four on either side of a central roof walkway I built between the roof hatches. Each panel can be tilted to 21, 33 or 45 degrees up, and when the panels are down against the roof for travel they are at 21 degrees down. I'm keeping some space at the end for two water-heating panels that I'll make later, and these will also tilt similarly. I don't have photos of my installation, but there's a YouTube video called Buses Gone Wild VII where you can see my bus before I installed the actual panels into their hinged support frames. Everything's made from 6061 and 6063 aluminum, with stainless hardware and hinges and support struts, so nothing will need painting. I also put two quick-connect water outlets on the walkway so I can easily and safely wash down the panels when they get dusty or covered in bird crap.

So far, so good!

John

Solar solar solar blah blah blah but WATER OUTLETS on the roof! Brilliant! All kidding aside it seems like you made a cool setup with the tilting. How often do you tilt? And the water up there is genius but how do you prevent that from freezing?
rffffffff is offline   Reply With Quote
Old 05-23-2021, 02:14 PM   #6
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by rffffffff View Post
Lastly, the Chinese cells are 3.2v nominally so 48v packs have to be 16 cells or 32. 14kwh but really 11.5kwh usable per bank of 16.
You are correct, buggered up the math. I knew this, just goofed and used 12 instead of 16. Two 48 volt banks of 280 ah cells.

Quote:
Originally Posted by rffffffff View Post
Other than the little details I think it’s going to be a robust setup. You’re going to want a fan up there, or two, at least most people find, so I would consider leaving space for that or engineering my idea of using the school bus
flashing light locations as vents with four fans on the front and back.
I want to eliminate as many vestiges of schoolbushood as possible. I'd like to eliminate that front (and back) "eyebrow" look altogether. My father is a hotrod builder, so he has the sheet metal expertise. We shall see. But yes, I intend to include active ventilation.
WiredForStereo is offline   Reply With Quote
Old 05-23-2021, 02:18 PM   #7
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by kazetsukai View Post
Anyway I wanted more solar, so I'm in the process of building slide outs for about 6200W total. The reason I want more is twofold...
I have also considered a bank of solar panels down the driver's side, with angle brackets to deploy while parked. But we shall see. Not currently part of the plan.

I like your three string battery bank. They're cheap. You can buy quite a few batteries for the price of a generator. Though I already have the generator. I actually have picked up two Mitsubishi L3E generators in the last couple years, one still has the gen head, 6kW. Thinking of building that in under the skirt.
WiredForStereo is offline   Reply With Quote
Old 05-23-2021, 02:20 PM   #8
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by Iceni John View Post
I don't have photos of my installation, but there's a YouTube video called Buses Gone Wild VII
I would really love to see this. If I give you my info, could you possibly text me some pics or something? This sounds like exactly what I'm looking for.
WiredForStereo is offline   Reply With Quote
Old 05-23-2021, 08:23 PM   #9
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,358
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Quote:
Originally Posted by rffffffff View Post
Solar solar solar blah blah blah but WATER OUTLETS on the roof! Brilliant! All kidding aside it seems like you made a cool setup with the tilting. How often do you tilt? And the water up there is genius but how do you prevent that from freezing?
When I start using my bus (it's still a work in progress now . . .) I probably won't need to tilt them in the summer; the tilting is for the winter when the sun is low and daylight hours are short. And if it's that cold I won't be there anyway - that's why buses have wheels! I can however drain each of the eight individual water lines coming off my distribution manifold without draining the other seven, so I could easily drain just the line up to the roof if it's that cold.

John
Iceni John is offline   Reply With Quote
Old 05-23-2021, 08:31 PM   #10
Bus Crazy
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 1,358
Year: 1990
Coachwork: Crown, integral. (With 2kW of tiltable solar)
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Quote:
Originally Posted by WiredForStereo View Post
I would really love to see this. If I give you my info, could you possibly text me some pics or something? This sounds like exactly what I'm looking for.
Sorry, no pics at all. I take crap photos, so now I just don't take any photos any more. Whenever I used to take them, I would always end up deleting all of them later anyway because they all looked pathetic.

John
Iceni John is offline   Reply With Quote
Old 05-24-2021, 10:02 AM   #11
Bus Geek
 
Join Date: Sep 2018
Posts: 2,831
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
Quote:
Originally Posted by rffffffff View Post
Solar solar solar blah blah blah but WATER OUTLETS on the roof! Brilliant! All kidding aside it seems like you made a cool setup with the tilting. How often do you tilt? And the water up there is genius but how do you prevent that from freezing?
I have a 5 window and one of best discoveries I’ve made is that the bidet sprayer shower wand on the 6 foot hose can be used to spray the panels through the emergency hatch.
Danjo is offline   Reply With Quote
Old 05-24-2021, 11:33 AM   #12
Bus Nut
 
Join Date: Sep 2017
Location: Cerrillos, NM
Posts: 393
Year: 2002
Coachwork: Amtran
Chassis: Front Engine
Engine: DT466E
Rated Cap: 72
Quote:
Originally Posted by Danjo View Post
I have a 5 window and one of best discoveries I’ve made is that the bidet sprayer shower wand on the 6 foot hose can be used to spray the panels through the emergency hatch.

Love this. I made my own faucets so I can spin off the adapters and connect a garden hose but it still requires the hose so it’s annoying.
rffffffff is offline   Reply With Quote
Old 05-25-2021, 12:37 AM   #13
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by Iceni John View Post
Sorry, no pics at all.
Well, as we say on the internet, pix or it didn't happen.
WiredForStereo is offline   Reply With Quote
Old 05-25-2021, 10:59 AM   #14
Bus Geek
 
Join Date: Nov 2016
Posts: 2,775
ballpark production in ideal subtropical conditions for a 12V system

is 300Ah per day per 1000W of panel power rating

Season, latitude and weather dependent of course.

Panels visible from the ground increases chance of theft, and most likely adds wind resistance, requires a stronger heavier support rack and decreases mpg at speed.
john61ct is offline   Reply With Quote
Old 05-25-2021, 12:00 PM   #15
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by john61ct View Post
ballpark production in ideal subtropical conditions for a 12V system

is 300Ah per day per 1000W of panel power rating

Season, latitude and weather dependent of course.

Panels visible from the ground increases chance of theft, and most likely adds wind resistance, requires a stronger heavier support rack and decreases mpg at speed.
Will be a 48 volt system with lithium iron phosphate batteries. Solar panel theft is not on my list. I think the kids are more into Playstations these days.

I always wonder why people are so concerned with fuel economy. How many hundred thousand miles are you putting on a year? I'm buying this thing to live in, not commute from Alaska to Florida every morning for work. It's shaped like a brick! What do you expect?
WiredForStereo is offline   Reply With Quote
Old 05-25-2021, 12:41 PM   #16
Skoolie
 
Join Date: May 2013
Location: Monrovia California
Posts: 151
Year: 1984
Coachwork: Blue Bird
Engine: 3208 turbo Cat
Rated Cap: 78
Quote:
Originally Posted by rffffffff View Post
I don’t know much about the bifacial panels but I would assume the cost doesn’t justify the extra production, and the length of the bus *may* make 7 rows of 65” panels more effective overall. I think 6 hours a day is a bit of a stretch too, but that really depends on where you are. I saw a chart someplace that said to derate solar wattage 75% in NY, 0% in NM (the two places I stay) so location obviously really matters.

Lastly, the Chinese cells are 3.2v nominally so 48v packs have to be 16 cells or 32. 14kwh but really 11.5kwh usable per bank of 16.

Other than the little details I think it’s going to be a robust setup. You’re going to want a fan up there, or two, at least most people find, so I would consider leaving space for that or engineering my idea of using the school bus
flashing light locations as vents with four fans on the front and back.
fffffff, what do you mean by" fan up there", to cool down the inside?

J
juliol is offline   Reply With Quote
Old 05-25-2021, 12:46 PM   #17
Bus Nut
 
Join Date: Sep 2017
Location: Cerrillos, NM
Posts: 393
Year: 2002
Coachwork: Amtran
Chassis: Front Engine
Engine: DT466E
Rated Cap: 72
Quote:
Originally Posted by juliol View Post
fffffff, what do you mean by" fan up there", to cool down the inside?

J

Maxxair or fantastic fan, nothing about the solar panels just considering roof space. I couldn’t live without mine and if the whole bus was covered in solar it would be hard to ventilate.
rffffffff is offline   Reply With Quote
Old 05-25-2021, 12:53 PM   #18
Bus Geek
 
Join Date: Nov 2016
Posts: 2,775
Quote:
Originally Posted by WiredForStereo View Post
Will be a 48 volt system

What do you expect?
Then divide my Ah number by four, and LFP's high CAR may help make it true even far from the equator, at least in summer.

Just trying to help, you're welcome, and

feel free to just ignore stuff you think irrelevant to your use case.

I agree mpg are not a priority, but panels going flying should be.
john61ct is offline   Reply With Quote
Old 05-26-2021, 02:48 PM   #19
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by john61ct View Post
I agree mpg are not a priority, but panels going flying should be.
Obviously. I've seen some pretty terrible solar mounting bodges, using department store hinges and random pieces of steel.

As an engineer, I would consider it a personal failure to lose a solar panel. Everything I do is well over designed.

My family motto is "If it is worth doing, it is worth overdoing."
WiredForStereo is offline   Reply With Quote
Old 05-26-2021, 02:49 PM   #20
Traveling
 
Join Date: Aug 2016
Posts: 198
Quote:
Originally Posted by rffffffff View Post
Maxxair or fantastic fan, nothing about the solar panels just considering roof space. I couldn’t live without mine and if the whole bus was covered in solar it would be hard to ventilate.
Extra power makes lots of things doable though. Ventilation is not required to be on the roof.
WiredForStereo is offline   Reply With Quote
Reply

Tags
battery, generator, solar

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 07:39 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.