Should I purchase solar?

[neil.ervin]

I live in Phoenix and am ordering a new 25 foot Safari. It comes with two deep cycle batteries. We plan to do a lot of dry camping and to take long trips (up to 6 months) in the trailer.

My dealer is recommending I install two solar panels for keeping the batteries charged. He sells ARCO panels. As you folks know, the cost is high. Assuming the sun is out, is solar dependable over many years, or does it take a lot of maintenance to keep the solar system in operation?

Thanks,

[Tin Hut]

Solar should not be high maintenance if installed properly. I'd check out other options to compare cost and spec. On my sailboat I use a flexible Siemens panel that keeps the battery charged well. I unplug it and store it when underway. It was easy to connect to the battery as well. Check out some marine sites such as Westmarine.com, Defender.com. Boatus.com Good luck.

[Silvertwinkie]

If you're looking to keep your batteries charged and you run fantastic fans, lights, radio and you boondock, I would go with a plain old Honda 1000 inverter generator. Reason being is that Moe did a great write up on actual energy used vs. what the solar could provide and if I recall correctly, it wound up that the solar barely kept up with the demand, even in full sunlight (which is not always possible).

[dtbw]

I have two 55 watt panels on our '02 19' Bambi along with a SolarBoost 2000E MPPT controller. I also have a Tri-Metric battery monitoring system. The solar panels do work and if you have a way of accurately monitoring your usage (ie something like the Tri-Metric), you can be self sufficient electrically. Modern Airstreams have LOTS of lights and power hungry devices, that if used indiscriminately, outstrip even the largest solar array that you can install. Also remember that your solar panel will only be at peak a fraction of the day since they are in a fixed horizonal position , but a good MPPT controller offsets some of this. About the only maintenance is to clean off the panels from time to time as dust accumulates and cuts the output. Another factor is that you should really not drain deep cycle batteries below 50% as it really shortens their life (another reason for something like the Tri-Metric). One thing that I really like about the SolarBoost2000E is that it has a built in desulfation cycle. Sulfation of batteries is what kills them over time and slowly reduces the amount of power they can deliver. It is easy to remember the last desulfation as the Tri-Metric has a day counter that records days since last desulfation cycle (equalization). The built-in converter that A/S uses (Magnetek) is lacking this feature and even if it had it, it would be of no use without 120VAC to run the Magnetek. (the aftermarket IntelliPower with ChargeWizard does have a auto desulfation cycle)

Solar is expensive as you pointed out and you can buy two of the Honda EU2000 genset and have 4000W of power for less money and they will run your Air Conditioner, where solar is only good for the lights, water, refrig circuits, heater. If your goal is keeping the batteries topped off while in storage then the flexible panel that Tin Hut mentioned is a good solution, but on the other hand, if self sufficiency from AC is the goal, then either gensets or solar are your options. Ideal situation would be have both.

david

[bredlo]

Without knowing anything about cost or effort to make it all work...

I'm thinking of a dream system which would include a series of flexible solar panels on 2-3" tall legs, riveted to the roof in an arc that would match the curve of the Airstream. As we drive down the highway it would charge several batteries which would run our plasma t.v., stereo, a couple of roof fans, water heater, etc.

I'll bet there are also some kind of array of wind generators that could be perhaps tucked between the trailer and tow vehicle, so that you were harnessing your speed as well. Does this exist in any form?

Trailers are such small habitats, there must be reasonable ways to power it by alternative means. I'll have to search more on this, I'll bet there's a lot on this site alone.

[nellie the elephant]

I recently have installed three 10 watt seimans panels, and a small 4 amp charge controller, and a second battery. Just tried it out over Easter, and was super pleased. On the last day there, I was vacuuming the interior of my AS using an inverter, and had my kids watching a DVD while I was striking camp. Grant it, I have a 1966 Safari, with no phantom loads, and I only run lights, water pump, stove fan (occasionally), and the heater fan (occasionally). Every day by noon, my batteries where back up to full charge.

The "myth" of not getting the full benefit of your panels if they aren't aimed directly at the sun, is just that...a myth. You lose 10-15% max power in the horizontal postion, I know because I had a volt meter hooked up to my system, and I watched it while aiming the panels almost away from the sun. It read 17.6 volts no matter which way it was aimed (short of being in the dark), and that counts for cloudy days. I checked it every day while it was in storage (we get marine layer conditions that can last all day), and it alway measured the same voltage. Bottom line, they work. And if you are like me...where you don't like the smell or sound of a generator in a spectacular remote location, that you somehow managed to get your AS to squeeze into, then solar is the answer.

Good luck.

[Silvertwinkie]

I think that overall cost vs benefit is where I'm coming from.

Cost of solar package lets say is $1000.00 (when Airstream offered it I think it was about $1200). Let's say that it produces 17 volts.

Cost of a Honda 1000. $800. Produces 120V A/C. Inverter buit in, is very quiet, fuel efficent and does not produce a noticable smell of exhaust.

Now granted, the old generators were bad news...loud, bulky and smelly. The Honda I have seen first hand and it is a supurb little device and produces more bang for the buck in a shorter period of time than solar can (currently). My vote is still the Honda based on output vs. cost. Plus depending on how large your A/C unit is, you might even be able to hook up two in par and run your A/C unit (might need the Honda 2000s for that and they cost about $999 each, but only if you want to run the A/C).

Last part is that we are talking about the new coaches that do have the extra loads, and to top it off, I thought Airstream nixed the solar package.

RoadKingMoe did a great writeup on the generator vs solar somewhere here....great reading, very accurate and a must for folks thinking about this very subject.

[nellie the elephant]

All good points Twink, and well taken. There may be a day that I will purchase a generator, when I'm a full timer. For now, for me, the solar package is the real deal. I did it myself for under $300.

[thenewkid64]

I have had solar, I now have a genset.

Depending on where, when, and how you camp there are benefits to both.

Solar is silent, will get you plenty of power as long as you have sun and a properly sized system. It does have limitations, but so do gensets. With a proper inverter and batteries the solar will do 75% of what a genset can do.

With solar:
No lugging of gensets, lugging gas, no maintaining of additional engine(s). No need to worry about the solar getting legs if it is attached to the roof while you are off hiking. Not having to give the genset rules any though when parking/camping. Not having to deal with the next door neighbor that HATES gensets. Solar is COMPLETELY silent, great when you are boondocking and want to hear nature.

With Genset:
Ability to run the AC if you wish, and have enough capacity (properly sized). Ability to run the microwave if you wish. No need to worry if tomorrow will be cloudy that we need to conserve today. See cons above

I have a genset now because we camp in FL. It is also frame mouted in the MH. We NEED the AC to make camping fun. In many of the northern climates AC is optional, many campgrounds do not even offer 30 amp service. So depending on where you are planning on camping, or where you live, solar or a genset is a personal decision.

Roadkingmoe's chart is a good primer on what the loads are, what you will need to maintain the coach batteries. The style of camping you do has a lot to do with the "will it work for me" factor. Get as much in the way of panels as you can along with as many batteries as you can fit. Once you have it (properly sized of course) you may never plug in to charge the batteries ever again.

[dtbw]

Nellie,
What you can't detect with a voltmeter is output current (amps, and that is what charges the batteries). Solar panels generate rated voltage with very little light, but their current output is VERY dependent on the intensity of the sunlight which is greatly affected by the angle between the panels and the sun. With my SolarBoost2000E controller, I can watch output current. When a cloud passes overhead the current drops dramatically, yet the voltage remains constant. It also shows that although the panels startup (indicated by the controller) shortly after sunrise, no significant current is produced until a hour or so later and peak productions is a few hours around the solar zenith in the summer months.

I chose to go solar as my initial investment, but I do plan to add a pair of the EU2000E gensets as solar is only part of the overall solution

david

[nellie the elephant]

Very cool. Thanks for the info David.

[silver suz]

I suggest you go to www.realgoods.com. They have a great package all set up for rv's. The solar works even on cloudy days, and the racks can be tilted for max sun. I plan to have the solar energy fed into the utility at home when we arent using the trailer, so it can make us some money. And yes there are people who do both solar and windgenerators. Realgoods is working with us on designing the solar pkge. There is even a pedal power generator that my son will make on his own out of parts around here. Put that teenage creativity and energy to use!!! Silver suz
Real Goods summer 2004 resource guide 800-919-2400

[74Argosy24MH]

Originally Posted by silver suz

The solar works even on cloudy days, and the racks can be tilted for max sun.

I have 2 panels on my mh and would be careful about claims made by vendors. Solar is good, but a hundred watts takes a lot of space, and is only a hundred watts on a totally clear day and when the panels are at 90 degrees to the sun. Lower angles and clouds dramatically reduce output. I doubt seriously you would ever get your money back for the extra equipment needed to feed back to the commercial grid. Call your local electric company (and an electrician) and see how much trouble and expense it will be to get connected for the amount of power you will generate.

The panel mount drawing I saw on their site was pretty generic, no latch, adjustability, etc. You don't want the panels bouncing loose on the roof for the longevity of both, will they latch and release from the ground? Mounting looks like it is from the ends, adapters will be necessary for the curve of the roof. Tilt looks like it is to only to 1 side, so it will probably only be useful half the time if then. For solar panels to be the most efficient you should park east-west which is the worst orientation on hot sunny days when they work the best. Park in any other direction and the tilt will help for a couple of hours but put them at a very low angle for the rest of the day. I went through all this and finally mounted them solid and flat, the limitations and hassles didn't seem worth the benefits. Solar is pretty expensive for the power produced, in this case I think simpler is more reliable and cost effective.

John

[RoadKingMoe]

Lots of good information and correction of misinformation here, especially with Dave on board.

The problem with solar is that you can't park in the shade anymore. The same sun that provides electricity is heating up your trailer. But if you camp where there is no shade, solar can help offset some of that heat gain. One Shell/Siemens SM-110 110W, or one Kyocera KC120 120W panel, with a SB2000 controller, puts out just about enough amp-hours per day to run one Fantastic Vent on medium during daylight and a bit longer to get the day's heat out of the trailer. In spring and fall, it puts out less, but less fan run time is needed. As already mentioned, there are way too many phantom loads and power-hungry appliances in modern Airstreams to try to rely completely on solar.

Heed the warning about ratings. Solar panels are rated at 1000W/m² of solar insolation, which is what you get on a clear day with the sun at 90° to the panel in both axes. As the sun moves away from that, insolation and output CURRENT goes down with the cosine of the sun's angle away from 90°. They are also rated at a panel temperature of 25°C or 77°F. That would probably only happen with an ambient temperature down around 50°F. As temperature goes up, output VOLTAGE goes down, and cell temperatures can exceed 140°F on a hot day.

The only time and place a horizontally mounted panel would get its rated output would be at solar noon, on June 22, 1 degree (60 nautical miles) south of Key West, IF the temperature was about 50°F at that time of day, at that time of year, at that location. It'll be a cold day in hell when that happens.

Shell is the only one I'm aware of that also publishes their performance under realistic conditions, with their Typical Data at Nominal Operating Cell Temperature conditions. Their 110W panel becomes an 80W panel, with about 1.5V and 1.3A less output, under mild real-world conditions.

Maximum Power Point Tracking (MPPT) controllers can convert excess panel voltage above that needed to charge the batteries to extra current. The higher the panel voltage and the lower the battery voltage, the better they are at this. However, like converters and inverters, they are not 100% efficient. There are times, when temperatures are high (and panel voltage low) and battery charge isn't low, that they can be less efficient than a standard controller. It's very important to select a panel with a high output voltage, if you are going to use a MPPT controller like the SB2000. It is also important with these to use large gauge wiring to minimize voltage drop.

Tilting mounts can help, if you are out boondocking where you have the freedom to park the trailer with one side or the other due south. But this is seldom practical in RV parks, where you may wind up having to park with the trailer in a north/south orientation. But then you'd have electricity in an RV park, and using solar or generators would be pretty insignificant, if not absurd.

You CANNOT even come close to gauging the state of your battery charge with the Airstream indicator lights. Even the good amp-hour meters like the Trimetic, Link 10 or others are just a close estimate.

It's also unlikely you'll fully charge your batteries with either solar or generators. That last 15-20% takes as long or longer than it does to go from a near-dead 20% to 80%. It isn't practical to run the generator that long, unless you're using air-conditioning all day, and you'll usually run out of daylight with solar before that. It's best to shoot for 85-90% charge, which means you'll have 35-40% of your battery capacity to work from if you try to stay above 50%.

With a modern Airstream, solar panels are fine to augment generator(s) if you have extra money left over. They'll reduce your generator run time perhaps an hour/day for every 100-120W. But they won't do air-conditioning, and that Fantastic Vent may not cut it in the desert.

[Flyincloud]

Im real fond of my new panels made by unisolar , they are flexable plastic mounted on sticky bituthane stuff , they come in lengths up to 18 ft x15 in. x 1/8 inch and made to stick on flat seam metal roofs . They bend to fit the curve on your roof and stick right to it . One side of my roof is covered with them from end cap to end cap . less output than a rigid panel but big enough to make up for it . No you cant run your a/c but it extends my camping in the williwacks and is worth it to me because its quiet and with glass matt batteries I never think about the charge unless I am using power . When its sitting I dont have to think about adding water or having it plugged in to maintain the charge .

chris

[RoadKingMoe]

It takes four of the Uni-Solar 32W panels, for a combined area of 33.4" by 112.54" (3758.84 sq in) and a 4 for $1,100 price, to approximately equal the rated output of ONE $474 Kyocera KC-120 panel that only takes up 25.7" X 56.1" (1441.77 sq in).

In other words, flexibles cost 2.5 times as much, and take up 2.6 times as much area, for about the same power.

Or said another way, conventional panels only cost 40% as much and only need 38% of the space compared to flexibles.

Plus, the flexibles run hotter without the space for cooling air flow behind them.

But it's your money... whatever floats your boat.

[silver suz]

Well, I still have no choice. Petrochemical is out of the question. I'm not getting the tilt racks right away as I realised I'm not capable of tilting them on my own.
I am having very good progress turning my dog (part black lab- 8 yrs old 50 lbs) into a service dog. The private trainer says she's the best dog she's ever seen. We are already up to service dog in training- just waiting for the cape. She's great in her new cage in the car and hops in and out. Great at the grocery store. Now we have to get her used to obeying commands when there are lots of kids and other large dogs around. The UPS man and I agree she passes when she stays at my command and doesn't chase the truck or bark at him.!!! Today was a slightly rainy day so I was able to walk her up and down the road but no one else was out. Oh well. Still working on solar and husband replacing the tail lights with leds so they are much brighter. One got in tonight. I know it's not traditional but it fits the same space and is MUCH brighter. It's going so slowly I feel like screaming and pulling my hair out. Don't know how you did it tin can luv. Of course my husband is a perfectionist. this makes for beautiful work when he FINALLY gets done. We do have two fantastic fans in now and all sealed. suz

[RoadKingMoe]

Suz,
If the power goes out during the summer (worst case) in a campground in the Keys, you will need as a minimum per day:

60AH - one Fantastic Vent running on medium 24 hours

82AH - Sun Frost RF19 refrigerator running with an average 90 degree internal trailer temperature, maybe 80 at night, 100 during the day with the Fantastic Vent with 90+ degree average ambient temperature.

8AH - one ThinLite flourescent light running 4 hours, second Thinlite (over the sink or in the bathroom) running an additional 1 hour

That's 150AH per day, and you'd want to be able to go two days on batteries without dropping below 50% charge, so you'd want 600AH of battery capacity. For going three days on batteries, you'd want 900AH and so on. Group 31 Lifeline AGMs are 100AH each, IIRC.

If you believe the electrical outage will last more than 2-3 days, or if you intend to try to boondock, five 120W solar panels at 30AH/day would supply that minimal use per day, if every day was a sunny day all day. With afternoon clouds and thunderstorms, plus the occasional rainy spell, eight 120W panels would carry you through most situations, plus have sufficient capacity to make up one day's use in two days of all sun.

In Spring and Fall, your solar array will be producing about 2/3 of that output, but the need for the Fantastic Vent will decrease and the refrigerator power use will go down.

Winter might still be a problem, especially without tilting panels.

[silver suz]

Thanks, Moe, I'm still trying to figure out how much room I have on top of the roof. I already have a lot of solar things like a portable oven, lamps that generate 20 hours from 3 hour exposure, fans that operate on batteries and a solar battery charger. Lots of things that operate on batteries and can be used with re chargeable batteries. I also have a cooler that lasts 5 days with ice. The one thing I wonder is if I put solar panels on the behemouth van, would they be too far away to charge the trailer batteries next to the refrigerator( lines going out the ref vent.). Should I have seperate batteries in the behemouth (the AS van's name)?? And can they take the heat in the van? after all the agm's were made for hummers. But John can get deep cell gel for 1/2 the price. I even have a solar laptop charger. And Mark is working on the bycycle charging generator! As if I could petal very fast. I still havent figured out the oxygen problem but I hear nebulizers come in battery operated models. Thanks for all your help, Moe. I'll send you the electrical diagrams when we get that far. Any good advice on the microwave oven? I'm looking at 500 watt and 700 watt ones at west marine. As for clothes washing I can always do the foot stomping in a bucket routine, and dry on a line strung the length of the trailer. Been there, done that.
And over all- the keys and the carribean islands are FAR FAR cooler than TX in the summer. And a great breeze usually. I find I eat very little when I am by myself, and spend most of my time during the hottest part of the day, snorkeling- the kind that exerts very little energy. Mostly observing one patch. I really am the absolute most relaxed, snorkeling, and feel the best. (I wear full suit with booties to protect against jelly fish stings, and cold) I guess the solar will have to take care of itself- I'll just have to live with it. Cold camping is not something I can do, now. The circulation is so poor in my feet I wouldnt want to chance it (Aunt lost toes, Uncle lost leg). Thanks again, suz P.S. I can be home for winters!!!! And the speed at which the trailer is going- who knows where I'll be this summer. And mostly, I'm getting used to staying in the house all the time. suz

[silver suz]

P.S. If I could get someone to run the van- would that charge the batteries?? Would it harm the van? I have a solar battery trickle charger that's working really well with the other (hhhmmmm...) useless trucks around here (My son's projects in progress). thanks, suz