Solar Setups Different than SMB Solar?

[coyotearms]

Originally Posted by billwilson

looks like you have the controler up top? whats up with that?

The box on top is a combiner box. It is there where the leads from each of the solar panels connect in parallel and to a larger gauge cable that comes into the box through the roof from the solar controller, which is mounted on the rear side on the EB50 bed frame. The liquid tight strain reliefs for each panel are not installed in the photo below. With this arrangement there is one roof penetration no matter how many panels I end up with. Right now its guts are very simple, just bus bars to attach positive and negative leads to and is appropriate for two panels.

With four panels the box will include fuse or circuit protection needed on each positive panel lead to prevent any possible short associated with one panel to drive all the current from the remaining panels toward that short thereby over loading the shorted panel's wiring. The size of the box was made large enough to include those additions, whose details have not be finalized yet.

Originally Posted by billwilson

have you thought about a "air dam" for the front to reduce "lift" when on hwy
under the front of the solar???

I haven't yet come up with an attractive, functional design for that yet. I looked at Thule or Yakima air dams, but they are not wide enough and there are attachment problems given where the front load bar is located. Any ideas would be greatly appreciated. Actually, I want the dam to reduce the amount of bug juice that get splattered on the bottom of the panels as the critters are driven up and over the windshield. Putting an air dam on should actually increase the lift of the panels since the air would then be moving over the top of the panels at a faster speed relative to the van than below them.

[coyotearms]

Originally Posted by Okie

Here's the proposed solar design for my soon-to-be-born SMB. I'd appreciate comments and questions:
* Three SolarWorld SW-245 Modules (245 Watts each, total 735 Watts)
* Mounted on cruiser top with Iron Ridge XRL rail system (see first page of http://www.ironridge.com/assets/files/I ... System.pdf) [No custom parts, six roof penetrations total, about $250 parts]
* Three Group 8D batteries mounted under van at rear (245 A-h each, total 735 A-h)

Your design is not too different than our except with 1) more emphasis on solar capacity, 2) emphasis on camping year round, and 3) our "extra" solar load comes from choosing a 110 VAC water heater and microwave, both of which are entirely optional to use given that there is a propane cook top when needing to cook inside. We are still new to our home, but here is what comes to mind:
* The total width of my panels is 56.6" compare to your 66". While going through Glacier National Park (max width allowed = 8') I realized that even though panels are not as wide as the vehicle, with rocking motion I started worrying that there were going to be instances where the first thing to hit was going to be an edge of a panel against the rocks---and you can't watch for them either!
* With the solar mounts you have chosen, be careful with how flexible they will be for mounting future things, even if those things are other panels. I went with Thule rails and load bars for that reason. Down side is how many roof penetrations result. While we have inflatable kayaks now that get stuffed in the back of the EB50 layout, forcing to sleep upstairs, we can easily remove the two panels (of the four) on the drivers side and throw a double hard shell up there, although it is so tall it becomes problematic to store anything up there. Any one panel off and we can put our roof box up there.
* Winter use: If so desired, remember with the bats outside, their useful capacity will be lower and charging will be affected also. Solar energy is also be significantly diminished. The only way out of the bind (or in summer with > 3 days in one place) is a generator, turned on at least when drawing lots of power. Most likely the only choice is an external one given all the stuff underneath(?), but and external one is not so bad, especially if you have a gasoline engine..
* I am guessing with this layout, the bed is in the top up front. We went with the Cruiser II top. We checked out the Cruiser I top for sleeping, and although people do it, we found the height between the bed and ceiling just too low to get in and out with the other person sleeping, reading or even turning over. The Cruiser II gives about 26" of room, which seems just enough to be workable. If at all possible keep fan from being over the bed. It doesn't take many times of it not closing properly at the wrong time to wet the bed, and that can be a big nuisance.

Looking forward to seeing this all come together!

[Advanturetrek]

Thanks so much for all the helpful advice!

Great questions.

To clarify the use scenario, layout, and answer a few questions:

Badgertrek-style -- extended backwoods and winter travels with telecommuting.
The use scenario drives a lot of the design in the build.

We're expecting to run a portable generator a bit in winter to back up the solar.

We looked into solar panel tilting. It seemed like a pretty dangerous thing to be lifting 150 pounds of panels on an icy day.

Cruiser II top for the extra sit-up space. Thanks for the info re the Cruiser I.

We'd love to go for a low vehicle with a PH. Ski goals affected that though.
What are some of the trails where height or width makes a difference? It sounds like Imogene Pass in Colorado and Glacier National Park would be two.

Bed sleeps 2. Full size bed. The aft-end will get cleated to the roof during the day. The fore-end will stay permanently in place over the cab. We like a permanently set-up bed so we don't have to take apart and store the blankets daily.
BillWilson asked about storage of panels in the context of a bed discussion. What panels is that referring to?

Question for the portapottie users: How practical would it be for a couple to be using it daily times several months?

High cabinets will be placed everywhere that the bed doesn't go. Not sure yet whether to put high cabinets in the back over the gear storage space, or whether to leave the area for tall items.

Computer equipment will be in a storage cabinet under the desk cabinet.

Thanks for the tip re fan placement. Appreciate the opportunity to avoid a wet bed!

Re walking on the roof, we'll use an aid climbing set up to get up to the roof while staying clipped in to the vehicle. Aid climbing involves ascending a wall by connecting fabric ladders to fixed load-bearing loops. It's typically done on granite or ice walls that lack good climbing holds. But it also could work for a steel van. The loops will include a vertical track up each side and a horizontal track around the top. The climber can also back himself by clipping a harness into a loop. With this setup, we'll be able to "walk" up to and around the roof while having extra safety insurance for icy conditions.

Bill, thanks for the tip on the BABB. We're eyeing Aldercrest's setup as a possibility, as it accommodates both road and mountain bikes. gallery/image.php?image_id=8562
Not sure about baja box size yet. Any recommendations?

Good advice re storage options. Currently, our storage spaces are the rear area, high cabinets, galley closet, and baja box. Advice and opinions on storage are welcome.

I imagine that Peter will post soon with more of the engineering and solar design info.

Thanks so much for the great advice!

Peter's wife

[jage]

Originally Posted by coyotearms

One big take-away I realized after re-visiting the sizing issue with PVWatts is about the difference between just mounting the panels flat on top of a rig (easy) or having a tiltable system (challenging). It really doesn't matter that much! At least that is what I observed using Seattle data considering a tilt of 45 degrees, which is close to the ideal for that latitude. Over the entire year, the solar radiation only increased by tilting from 3.34 to 3.78 kW-hr/m^2/day (13%). It is actually a tad less with tilting for May-July!

OK, but isn't all that data about having a fixed system permanently installed? With a tilt, I could adjust to the current conditions to get maximum return for a few hours, not averaged over days, weeks or longer- for example May-July my tilt might steadily decrease as the sun reaches equanox, but more importantly to catch that winter evening sun after driving.

Plus it's cooler. Of course, it's easy to build in my head, which makes it seem worth it!

[webbmac]

We have an 85w panel and an 8D Lifeline on our SMB trailer (will try to post pics, we will have it in action this week in Baja). Our reasoning is we tow the trailer when we are going to be on longer trips not moving the van for a few days. We can tilt it up and also point at the sun a little easier. I notice a few% points difference in amps between tilted and flat. But it is not enough to mess with a tilt mechanism on top of an SMB, trust me on that one. The main thing for a solar panel is to keep it out of the shade, partial shade will disable it.

[coyotearms]

Originally Posted by jage

OK, but isn't all that data about having a fixed system permanently installed? With a tilt, I could adjust to the current conditions to get maximum return for a few hours, not averaged over days, weeks or longer- for example May-July my tilt might steadily decrease as the sun reaches equanox, but more importantly to catch that winter evening sun after driving. Plus it's cooler. Of course, it's easy to build in my head, which makes it seem worth it!

You certainly have a point especially in winter, but as I said it is kind of like "zero x zero = zero." Since I live in Seattle, I chose there to make comparisons, and in winter the sun is REALLY low so tilting's good! Here are some numbers averaged over the month just to get the idea (See data for Seattle at http://rredc.nrel.gov/solar/pubs/redbook/). In January, taking the angle from horizontal to be the latitude here, which is very close to 45 degrees (AND pointing south), you get 1.5 vs. 1.0 kW-hr/m^2/day compared to 1.0 at 0 degrees---That's 50% more! However, even though every photon is especially precious in the winter, these numbers compared to 6.1 (the highest monthly value in the table), the winter values of 1.5 and 1.0 are only 25% and 16%, respectively, of that peak summer value! So much for deciding to stay inside the van on a January day to surfing the web and eating microwave popcorn all day hoping those panels can shove a lot of juice back into those cold. shivering batteries!

On that same page of data for Seattle, you can also see that with "2-axis tracking" you can 8.8 vs. 5.5 kW-hr/m^2/day in July. Now maybe that is motivation for some folks to get to the drawing board and figure out how to do that on the roof of their rig!