Solar Air Conditioner

Almot wrote:

sushidog wrote:
What's wrong with the Morningstar TS-MPPT-45 and TS-MPPT-60 charge controllers?

Nothing is particularly wrong with TS 45 or TS 60. Don't know whether Outback 60 would work better, but TS 60 is a good machine.

But they don't offer TS 45 or TS 60 with their 1000W system. They offer some unspecified PWM controller. A lot of beefy cable to run in RV.

They do offer TS 45 with 1500W solar, but 1500W won't fit on the roof of most RVs.

Besides, TS 45 is way too small for any of their systems. 1000W array needs at least 60A controller, not to mention larger arrays. They have very unusual approach to solar design. Not meant for RV.

Thanks for the reply.

Yes a TS45 is too small if you're only running it at 12v, as it will only handle 600 watts at 12v. But according to Morningstar's specs http://www.morningstarcorp.com/wp-content/uploads/2014/02/TSMPPTdsEng.pdf it will handle 2,400 watts at 48volts (what is needed to run this air conditioner). Wiring it at 48 volts, the amperage drops to 1/4 of what it would be for a 12v system. The wire size required drops too, making the wiring weight and expense 1/4 of what it would be for a similar wattage 12v system. Frankly I'm amazed that most solar systems don't run at higher voltages to save system resources. You can always draw 12v out of a 48 volt battery bank using 6-12v batteries to run your 12v appliances.

As far as roof acreage goes, let's do the math: a typical TT is 8ft x 30ft or 240 sq ft. Let's subtract 40 sq ft for the single ac (your solar AC is a mini-split design that will rest on your trailer tongue and won't protrude through the roof) This still gives you about 200 sq feet or available area for solar panels. Your typical 250 watt solar panel is nominally 40" x 65" or 18sq ft. Lets say that you place 2 panels side by side so their long axis is the same as the TT. this means that together, they would be 80" wide (less than the 96" width of the TT) and 65" (5 1/2 ft long). So 6 panels making up 1500 watts would occupy 195 inches of trailer length (16' 3") of that 30 ft long roof. 2000 watts would occupy less than 22 ft of roof space allowing you an 8 ft x 8ft area for protrusions (and their shadows), like an ac unit, roof vent and such. That's a little tight, but still doable. Then you can always mount solar panels on a fold our rack to the side of your TT, as I've seen some do, if you really need more than 2,000 watts of solar power.

At 44lbs each, plus wiring, you probably won't want to add more than 2,000 watts of panels (352lbs)to your roof anyway. Of course all this weight up top, raising your center of gravity will be offest by 500lbs (8-6v golf cart batteries) down low. Again, we're talking about a huge system. I think most folks might at least start with a 1,000 watt system (176lbs on the roof) and 4-12v deep cycle batteries (about 300lbs with controller and maybe another 30-35lbs of wiring) making the total minimum system weigh in at around 530lbs (plus the weight of the solar ac, which will be offset by the loss of the second roof mounted ac unit that it replaces - removing 85-90lbs off the roof too.)

Will there be unforseen problems to solve? Certainly, just like when folks install Lithium batteries in their RVs. But any new concept has these challenges. I'll bet it won't be long before installed systems like this become options on higher end units specifically marketed to the boondocking crowd. Of course I'm sure they'll be pricy, especially at first. Well at least there's the 30% second home tax credit you can get till 2016 - but you have to pay income taxes to get the tax rebate, which leaves out a lot of full-timers and retirees who would benefit the most from something like this.

Chip