Solar power capacity?

[ldetsf]

Anyone up on the latest solar power options for camping? Can it replace a generator now for thingsl like A/C, TV, Refer. etc.? Your comments are appreciated. Thanks.

[Silvertwinkie]

Very doubtful. For what you'd spend to get the capacity to run and A/C unit, I'd suspect you'd need the surface of a 34 footer. In comparision a generator would cost less and deliver more power without needing to be in full sun.

A lot of folks have wrestled with this issue and I believe most have gone with a generator. Some, propane powered generators.

[Fyrzowt]

I think in practical terms, you are going to be limited to battery maintenance, with some reserve. I had a trailer with about a 4'X5' panel, I was able to run my Fantastic fan all day, and incidental 12 volt appliences as needed, and still kept the battery topped off. You will not be able to run A/C.
Dave

[2airishuman]

Originally Posted by edfos2

Anyone up on the latest solar power options for camping? Can it replace a generator now for thingsl like A/C, TV, Refer. etc.? Your comments are appreciated. Thanks.

hi edfos2

tv yes, my 70-90 watt lcd runs great via inverter and is not a big juice draw for 2-3 hours viewing

fridge in gas mode easier when off the grid...

a/c, no way...that would take a boat load of panels AND a very large inverter, large bank of batteries,
gotta park in the sun which would just increase cooling needs... and so on. just not practical.

i've got both solar and genset...and use both.

microwave, coffee pot and other 800-1500 watt ac appliances also need a larger inverter and will just suck too much juice.

one needs to do an 'energy audit' to sort out how many amp hours used or needed, then look at the storage requirement (batteries) and charging potential (panel size, efficiency, hours of sun)

several of the solar vendors offer a spreadsheet for this purpose...

search the forums. there are many solar threads and some include links to the better vendors and solar web sites....

there are some newer things happening like shade tolerant panels, double layer panels, battery advances and so on....

hard to justify solar on a dollar cost basic...so don't look for magical free energy...yet.

cheers
2air'

[Janets Husband]

Originally Posted by Fyrzowt

I think in practical terms, you are going to be limited to battery maintenance, with some reserve. I had a trailer with about a 4'X5' panel, I was able to run my Fantastic fan all day, and incidental 12 volt appliences as needed, and still kept the battery topped off. You will not be able to run A/C.
Dave

Dave is correct in his assessment. You can probably get about 130W of solar panels on top of a 25' or so trailer.
That means about 130 rated watts of panel up there. In the best sun light conditions it usually works out to 70 to 80% due to variable factors of incident angles of sun light, so you can realistically expect 130W x 75% = 95W which comes out to 95W / 13.5Vdc = 7 amps of charging current give or take a little. Solar power is not exacting due to conditions beyond our control and it will vary greatly. So with about 7 amps available to charge the battery you can figure what you can run and for how long.

[bryanl]

Figure a typical battery has a kilowatt hour of energy in it, only half of which is usable. But most Airstreams these days have 2 batteries for a full kilowatt hour of usuable energy storage.

Gary and Dave noted that you could get maybe a couple of kilwatt hourss per day of energy from a solar panel on the roof, maybe.

An A/C needs more than a kilowatt of power usually so you could theoretically run it for maybe a half hour on a typical RV battery. But the typical RV battery isn't usually designed for this sort of 100 amp load as a routine thing.

So, like Joe said, the typical trailer RV is going to be hard pressed to have a battery, solar panel, inverter, and charge controller system to handle large loads like an A/C for anything more than a few minutes. A big class A with 8 times or more the battery capaacity (they don't worry about weight) and a large roof full of solar panels and near $10k of electronics might be able to support an A/C type load for a couple of hours a day.

And if the energy, power, amps, weight, and stuff doesn't throw you, you have a good start to being an expert in this area ;-)

[Silvertwinkie]

This has all been great info. Impressive all of the depth of the info shared so far. Thanks!

[ldetsf]

Thanks for all the informative responses.

[Motoman]

[QUOTE=Janet's Husband]Dave is correct in his assessment. You can probably get about 130W of solar panels on top of a 25' or so trailer.


I put 260 watts of solar (2 Kyocera 130 watts panels, rated capacity) on our 25' CCD, wired in series using a BZ Products MPPT controller; 24 volts nominal to the controller letting it handle the conversion from 24 to 12. I thought I would get similar performance in good sun conditions using the voltage conversion of the MPPT controller and better performance with in low light conditions. Another reason I used 24 volts from the panels is that the 10 gauge wire furnished with the panel kit and the 10 gauge wire pre-installed by Airstream is longer than recommended for 260 watts. Using 24 volts cut the current flow in half which results in less voltage drop in the wires. I am working on an article for the Sierra Nevada Unit and will post something with pictures when finished.

It was tight to fit the panels on the roof. I had plenty of room behind the AC to mount then lenghtwise but close side to side between the refirigerator vent on the street side and the awning rail on the curb side. I believe I had ~3" clear to vent cover, ~4 inches between panels (less between the Zee mounts) and ~3 inches to the awning rail.

[davidz71]

Check out Welcome to AM Solar - Your RV Solar Specialists since 1987 for their 100 watt panels which are made by BP and a little narrower than other 100 watt panels. I've measured my 25' roof space and believe I can fit 4 of these on my roof. I'm planning on purchasing the 100 watt system and then adding another panel next year. That should take care of battery maintenance and running Fantastic fans as long as I need. I also use a Yamaha EF3000iSEB generator during the cold months (20's-40's) while hunting and during the early bow season for deer when it gets hotter than the Fantastic Fans can keep up with and I have to go with AC.

[audiobox]

Another vote for the AM Solar system. We just finished principal photography for a solar DVD and had them install four panels, four AGM's, MPPT controller and converter/inverter on our 34' Excella. Great system. Imaculate installation. We have room for two more panels and hope to get them on there by next fall. They're always happy to talk with you and the owner, Greg Holder, is a trove of experience-based information.

Craig

[thecatsandi]

Only issue there is you are not getting the full output of the panels.
THe Controller is doing th voltage conversion not a Current conversion.
In order to get the most out of the panels, the output should match your battery/system voltage. ie 14vdc per panel 14vdc system parellel the panels.
14vdc per panel 28vdc system series the panels.

[ESCAPE POD]

I'm just starting to research solar panels for my 19' Bambi. What capacity solar panel(s) would I need if my only goal was to charge the batteries when they reach 50% capacity? Is there a standard measure (watts, amps, etc.) that I can use to compare solar panel systems for this limited purpose? I don't need to power any appliances, and want to keep the size of the panel(s) to a minimum, but I want to do more than just to keep the batteries topped off.
Thanks for any advice!
-Jerry

[Silvertwinkie]

There has been great discussion on that topic. I'd try a search for solar if no one chimes up.

[davidz71]

Jerry,
If you go to the AM Solar site mentioned in my previous post, you can compare the amp output per hour of the 100 watt panel and their 65 watt panel. You can then calculate on a 5-6 hr. day during the summer when the sun is overhead. The RV Solar Electric site also has a worksheet giving you the energy usage of appliances in amps per hour and you multiply this times how many hours you expect to use those appliances. They also have a phantom load calculator for those things like LPG detector, refrigerator panel, etc. Both sites have a wealth of information. One of those sites suggested a 105 amp hr battery and 100 watt panel for each individual in the trailer. Obviously this is a SWAG because some individuals are rather conservative and other leave lights on like they were at home. Anyone remember the Redi Killowatt stickers they use to have for light switch plates?

I will start with my one 115 amp hr battery and the 100 watt panel and experiment for 12 months. I will then buy 2 new batteries along with an additional 100 watt panel. I figure that will be more than enough for what I need. You also have to remember that you shouldn't discharge your batteries more than 50% for flooded wet cells to get the full life out of them and that as you get closer to winter the sun is lower in the sky thus you have to use tilt bars to take full advantage of the sun. Extremely overcast days can also cut into the solar output so I would rather have more than I need just in case.

[ESCAPE POD]

Thanks, Craig. My visit to the site you recommended makes more sense now, and I will scout for panels in the 100 watt range. We're pretty frugal on power usage, and with a solar panel, I doubt we'd ever actually deplete our batteries to 50%, but that's what they got to in about 2-3 days while boondocking in Death Valley this last week. At that point, we started flushing without the pump and broke out the battery-powered lantern!
-Jerry

[Motoman]

Originally Posted by thecatsandi

Only issue there is you are not getting the full output of the panels.
THe Controller is doing th voltage conversion not a Current conversion.
In order to get the most out of the panels, the output should match your battery/system voltage. ie 14vdc per panel 14vdc system parellel the panels.
14vdc per panel 28vdc system series the panels.

Michelle, sorry I was busy and didn't get to respond. I had the same concern in that how did they control the power applied to the batteries with an input voltage of ~28 volts and a battery voltage of 14. I reviewed the material for several manufacturers that produce MPPT charge controllers and then talked with BZ Products. Their MPPT controller, like others, incorporates a high speed switching network which includes a transformer to provide the voltage/current transformation from the PV side at approximately 28 volts to a lower voltage/higher current on the battery side at a nominal 12 volts or in my case a float voltage of 13.7 volts, not just a voltage transformation. The industry likens the high speed switching network and light weight transformer to the modern switching power supplies used for computers and other consumer and commercial electronics gear vs the more legacy heavyweight linear power supplies we were used to in the 1970's and 80's. They claim no significant loss of efficiency when used for higer voltage on the primary side provided it is within the design range for the charge controller.

Someone might better describe the technology than I did but I have had several conversations with BZ Products and it aligns with the descriptions from other manufacturers so I decided to incorporate that feature in our system on the Airatream.

[DFDureiko]

We've recently purchased a 1996 Excella with four solar panels, two batteries and a 2.5kw U-Series Trace inverter, installed in 1997 when the trailer was first purchased, by the now defunct Solarmetrics.
When I get to International I'll have AJL Solar go over the system. as I can't get it to work.
Question though.
with a four panel system, and saying I add two more Lifleline batteries. would it be unrealistic to be running an HD TiVo and 23in HDTV, meaning that, the HR10-250 DirecTV Tivo is running continually, 24hrs a day.
assuming we have sunny days every day would that be too much to ask?
I've heard people say they run their solar/inverter system at rallies with "limited electric" as they get more power from their solar system then they would plugged into the rally.
Thanks
Dan

[tslanier]

We are going to add solar panels instead a generator. I've talked to several Airstreamers who have solar and are very pleased with it as a more convenient way to recharge the batteries vs the disadvantages associated with a generator.
Does anyone here have recommendations for a particular brand or supplier. My local Airstream dealer installs them and they recommend Sunsei? Camping World sells SunForce.

[Dwight]

I am in the process of adding 4~120w Evergreen panels to our 34' with a 3000w inverter and 8~Optima group 27 batteries. Based on early calculations, I should be able to run the A/C for about 4-6 hours.