Solar Air Conditioner

[BassinDmax]

Okay for all boondockers needing to run air conditioning, gotta love ingenuity! :B

Solar Air Conditioner

[Ron3rd]

Yep, it's a version of the old "swamp cooler". Downside if there's much humidity all bets are off, plus they pump a lot of water into the air, which is not always good.

[sushidog]

westend wrote:
Good stuff guys. What I'd like to see is a small AC unit, even down to 2K or 3K BTU but with much less draw. If I could find an AC unit with lower draw, I'd increase my bank to 500AH and get more modules on the roof.

I'm kind of like Jim, in that I usually camp/boondock at places where the ambient isn't to bad. I also have my trailer insulated about as best as possible.

I would think a < 5K unit would keep the cabin temps in a range that would be very comfortable. I have an 8K BTU AC in my tent camper and at 85f with high humidity, it becomes a meat locker. I have to turn it off at night because the family freezes.

With the ultra-insulated, sealed cabin, less would be great.

Here's a small ac unit:
http://www.climaterightair.com/applications/outdoor-dog-house-air-conditioner-and-heater/climateright-2500-btu-mini-ac-heater.html
It has 2,500 BTUs of output, and draws 480 watts or 4.3 amps (7 amps at start-up) at 110v, so it is not very efficient compared to the last heat pump I posted which produces 12,000 BTUs from only 560 watts.

[westend]

Good stuff guys. What I'd like to see is a small AC unit, even down to 2K or 3K BTU but with much less draw. If I could find an AC unit with lower draw, I'd increase my bank to 500AH and get more modules on the roof.

I'm kind of like Jim, in that I usually camp/boondock at places where the ambient isn't to bad. I also have my trailer insulated about as best as possible.

I would think a < 5K unit would keep the cabin temps in a range that would be very comfortable. I have an 8K BTU AC in my tent camper and at 85f with high humidity, it becomes a meat locker. I have to turn it off at night because the family freezes.

With the ultra-insulated, sealed cabin, less would be great.

[sushidog]

Jimindenver, that is definitely a cheap way to go if you only need 5,000 BTUs of cooling. It's similar to the AC in my Aliner which I run with a 1,200/1,500 watt geny. However it only has an EER of 11.2, not bad as far as window ac's go, as many this size are only in the 9.5-10.5 EER range. The AC I linked to however has an EER of almost 21.5 meaning it will produce roughly twice the cooling power from same wattage draw. So if you truly only need 5,000 BTUs of cooling most of the time it will only be drawing around 250 watts with it's variable speed compressor and scalable power draw/output. Plus, being a native DC device you don't have any inverter loss, making it roughly 10% more efficient than converting from DC to AC power that a window unit AC would require. Remember that 3.9 amps is at 120v which will convert to a about 43 amps at 12v (assuming a 90% efficient inverter.) 720 watts of solar panels might keep up at peak sun, but just barely.

A better comparison is to an Arctic Breeze 12v truck AC. It draws 600 watts, making 8,000 BTUs, but like most ACs it must cycle (turn off and on)to reduce its cooling output. 8,000 BTUs should easily be enough to cool a single RV bedroom if you have decent insulation. My Aliner barely gets by with a 5,000 BTU AC, but it is tiny, (less than 100 sq. ft.) only slightly larger than an big RV bedroom, though it is well insulated. This unit draws 45 amps at 12 volts, but it will probably be running only 60% of the time, meaning that your average wattage draw would be about 30, making it much easier for your solar to "keep up" when not in peak sun. Still, 3-4 8-d batteries would give a much more comfortable buffer, and wouldn't be stressing your battery bank as much from the Peukert effect of such a high current draw from a single battery when the sun isn't cooperating.

http://www.arcticbreeze-truckac.com/content/arcticbreezeintro.html

Chip

[crcr]

JiminDenver wrote:
This is the you tube about the bucket evaporator cooler.

Click

A buddy of mine who owns an older VW Westfalia camper, made his own version of the cooler in this u-tube vid. However, he used a small styro cooler in place of the 5 gal bucket, which of course gives much greater insulating power. And he uses dry ice instead of regular ice. He found using dry ice, the ice lasted for a full 7 hour drive.

[JiminDenver]

This is the you tube about the bucket evaporator cooler.

Click

[JiminDenver]

I am not saying this will work for anyone else, may not even work for us. Who knows?
This Window shaker uses 3.9a/ 446w on high and we have 720w of solar tracking the sun. A 8-D will take the surge of start up and I am hoping the solar will run it and leave the battery in float. At peak the array can produce 50a/ 650w. Luckily at 10,000 ft when the sun hides behind a cloud, the temps drops quickly. So no sun means no air needed.

Now being a dry state like Colorado is, swamp coolers work great up to a certain degree/ humidity. There is a you tube of a bucket swamp cooler that probably would do well for us if we had a larger supply of water. I can produce the electricity to run the A/C, I can't make water.


Edit fixed the link.

[sushidog]

I just saw a new development in solar ACs that are even more efficient, requiring even less battery power. Here's the link: http://www.geinnovations.net/Specifications.html

This new super high-efficiency heat pump (EER = 21.43) only requires 560 watts (11.5 amps) of 48v dc to produce 12,000 BTUs of cooling - about 60% of the previous high efficiency solar heat pump I linked to! Plus, like the previous system, the rotary compressor doesn't cycle on and off like a typical ac unit. It ramps up and down from 5,000 BTUs to 12,000 BTUs as required, so no high current start-ups are needed, saving even more power. Yes, a solar ac system will still be heavy, but 1,500 watts of solar should be sufficient to replenish your 8 - 6v GC-2 battery bank, not 2kw as was previously suggested with the other less efficient AC unit. As time passes and technology improves, the prospect of solar ACs gets more and more practical, extending one's boondocking season even longer, especially if you plan on only cooling a single bedroom at night, for a good night's sleep (when it's cooler outside anyway) and not the entire trailer, as you would during the day when there is plenty of solar power available. Let's say you start the night with 200 ah in your batteries (at 48 v) or 100 ah available and your AC averages only 6 amps draw (about 1/2 power, as things are cooling off), that means that you could run it for over 16 hrs. before you reach 50% battery capacity, leaving extra power available to run other things. Or you could cut your battery bank in half - say only 4 - 12v deep cycle batteries and still run your solar AC for a full 8 hrs before your batteries reach the 50% level. Let's say you have 4, Trojan T1275s (150 ah 12v batteries, leaving power to spare). Since you are normally outside most of the day and won't be using your AC then anyway, a full day of sun on those 1,500 watt panels and you should be good to go for another night of comfortable sleep (and an evening of a couple hrs. TV viewing, lighting and water pump use to boot). If it's a cloudy day, a back-up EU2000 Honda run for few hours or a supplemental wind generator should be enough to make up the difference and get that battery bank up to capacity again.

Chip

[reed_cundiff]

Barney

Thanks - I shall try this

Reed

[BarneyS]

reed cundiff wrote:
Snip...
I can send you photos of system via e-mail if you like since I have not figured out how to attach photos to this forum

Reed and Elaine

It is extremely easy now that we have a site dedicated to posting pictures on the forums. Take a look at this thread, which is stuck at the top of this forum for instructions. It is basically cut/paste.
Barney

[reed_cundiff]

"Does the KWH rating of PFP batteries reflect total KWH, or usable (available) KWH (70% of total capacity)? Also, did you have to get a special solar controller or was the Morningstar folks able to reprogram your controller with LFP voltage curves?"

Chip

The 9.6 kW-hrs is total energy storage, we can safely use 80% DOD for several thousand cycles (according to work done by Liberty Coaches) so we have just under 8 kW-hrs of usable energy. Our older son (as noted in earlier posts) has been in solar for almost 30 years as a researcher and first licensed solar/alternative energy contractor in New Mexico(has BS in electro-mechanical engineering and is a licensed master electrician). As noted elsewhere he designed and fabricated the panels and low voltage (under 1000 V probaby)for a 1.8 megawatt system for the power company near Las Vegas, NM. He did the reprogramming required for LFP voltage curves along with Manzanita industries. The Manzanita batteries came with internal battery management system that seems to work well (after 13 months with no hiccups)

I think our plan is to put a much smaller a/c unit into our bedroom that would (750 W) that would cool that room for sleeping. The outside temperature was in mid-90s today and we kept the 34' fifth wheel down to low to mid 80s which is quite comfortable. A single a/c unit is insufficient when it gets above 105 and we do not plan to go anywhere like that again. The Fantastic-Fans and the smaller 12V fans we plug into the 12V outlets make life quite livable. If it gets over 100, we go to much higher elevations, and we primarily boondock at dispersed camping in BLM/NF areas. We are currently "mootchdocking" for several days on the street visiting my cousin in Missoula, MT. We have not hooked up - and of course cannot open the slides on the street. City and neighbors are happy.

But we shall look into the 48 V DC heat pump. If it does use 1/3rd the wattage, it would be most affordable at $1.8K

We see no reason to add LFP batteries since 256 pounds is quite enough. The front bay is rated at around 400# so it could be done within frame, pin weight and pickup rear axle loadings.

I can send you photos of system via e-mail if you like since I have not figured out how to attach photos to this forum

Reed and Elaine

[sushidog]

Reed, since you are already at 48v it seems that adding a high efficiency 12,000 BTU mini-split 48v DC heat pump (actually an AC and an efficient heater) that uses only 1/3rd the wattage of your conventional rooftop ac unit at only $1,800 would be more cost effective than adding enough LFP batteries to triple your roof unit's runtime.

Does the KWH rating of PFP batteries reflect total KWH, or usable (available) KWH (70% of total capacity)? Also, did you have to get a special solar controller or was the Morningstar folks able to reprogram your controller with LFP voltage curves?

Almot, I see your point that their minimal system might provide 10 hours of cooling on day one (as you are starting with full batteries), but what about day two, (as you are starting day two with depleted batteries)? You would definately need more battery capacity and more solar power than that for continuous 10hr/day usage. Perhaps they are counting on the AC's 500w draw being reduced significantly as the inside temperature drops during the evening hours and the AC compressor scales back its output - to say 6,000 BTU or lower. I'm sure that a lot would depend on the load placed on the AC (which will vary widely) to determine its actual current draw and battery run time.

Chip

[reed_cundiff]

"...In reality, 30ft trailer - meaning 30ft box - will have room for 6*250W solar, not 2,000W. There should be clearance from roof structures, sides, front cap, and enough space to walk between all this if you need to inspect the roof and/or service the panels. Unless you cover the side walls with folding panels that you would have to fold/unfold every time, getting 2,000W on a 30ft box is going to be difficult..."

As noted in earlier post, we have 1420 W of solar on a 34’ 5th wheel and could have put another 700 W if had we so chosen. We have obtained over 1300 W to controller at mid-day in summer. There are definitive power losses in the system as is expected to battery suite and then from battery suite through inverters.I just went on roof to check and 3 more 235 W panels could be installed. We would have to remove the TV aerial but we don't watch TV anyway (we are generally not in coverage)

"Also, 4*6V batts is a lot of batteries for some RVs, and RV-oriented lithiums in infant stage yet"

As noted in earlier posts, we have 9.6 kW-hours of lithium-iron-phosphate and it has worked extremely well for a year. LFP is beyond infant stage and into advanced development since Liberty Coaches has been installing on all their $2M Liberty Ladies for the last two years. This is much like the ads in Scientific America 50 years ago when GE was making fun of solid state devices (transistors then) by noting that valve technology was quite developed and we should never need anything more advanced.

Son Cary noted we have room for another 4.9 kW-hours of LFP in the bay. We do not think this is necessary and choose not to do such. 14.5 kW-hour and 24 kW-hour lithium suites are available.The latter is about 500#. The prices are going down.

We do run the a/c several times a day when it does get hot. We choose not to run it continually since we are a bit OCD about going far down on DOD.

Ron Jones was the first that we know of to incorporate LFP which he did on his motorhome(400 amp-hours I believe).
Reed and Elaine

[Almot]

Sushidog, 2,000W solar on 30ft trailer is just a math.

In reality, 30ft trailer - meaning 30ft box - will have room for 6*250W solar, not 2,000W. There should be clearance from roof structures, sides, front cap, and enough space to walk between all this if you need to inspect the roof and/or service the panels. Unless you cover the side walls with folding panels that you would have to fold/unfold every time, getting 2,000W on a 30ft box is going to be difficult.

Also, there are many 20ft and 24ft rigs out there, and those will only have room for 700W or 1000W.

Also, the retailer's estimates of solar harvest are a bit optimistic. I couldn't find any data on the A/C current on their website, but from what they say about 5 hours of run from 4*6V batts, it comes to 45AH per hour @12V. Harvesting 500-600 AH a day required to run the 1,200 BTU A/C for 10 hours and other loads - with 1,000W solar panel I wouldn't count on that. (Or - 1.5 times that much with 1,500W panel). There will be days when there will be hot but not sunny enough to harvest even 400 AH. Not to mention that harvesting is one thing and putting it into battery is another.

Also, I feel a bit of sales pitch here. They say - A/C 10 hours in daytime (with their smallest system), and 5 hours from battery after dark. Wait a minute - 10 hours A/C plus other loads is ALREADY what the solar can harvest under perfect conditions, so where those extra 5 hours will come from? You need to put that 5 hours worth of energy back in battery next day, but the solar is already taxed up to the limit.

Also, 4*6V batts is a lot of batteries for some RVs, and RV-oriented lithiums in infant stage yet.

Also, running 48V system for 48V A/C and battery charging won't let you use the excess of solar energy without it going into battery first, when you have such an excess. Technically possible, with some 48V inverter to run 110V devices, and some DC-DC converters to run the remaining 12V devices. A bit of pain and losses. IMO, this retailer didn't think that far.