I just love this cartoon, it comes from Robert in Australia
I'm borrowing it for my example of why its actually 100% impossible to install enough
solar to power an RV - Air Condition system.
Robert is actually a good guy and you can find his page here
Solar AC is impossible
The simple fact is that while completing this project I have found at least 10,005 expert reasons in the field of RV's , Solar Experts and Solar RV experts all with no less then 30 years each in experience telling me and others like me that it is simply 100% impossible to install enough solar onto a trailer or an RV to operate an Air Condition system at best maybe for 30 minutes to an hour and what good would that do ? You may look at my project and say, well its no big deal running an ac inside a trailer - after all I have done it and proven that its now possible. First i'm gonna tell you why all the 10,005 experts are right - its impossible to install enough solar on a RV or trailer to provide air conditioning. Then i'm gonna tell you how I broke the mold and how its really not only possible, but I think its quite easy.
1.) The first and most stubborn problem the experts have is that its already frozen into their mind that it cannot be done, its impossible. Example: I sent my project to the self proclaimed "GOD of all RV -SOLAR GODS" - this solar god spends quite a large amount of effort bad mouthing other RV solar dealers on how they improperly install solar systems which he has to rebuilt from scratch. There is only one way to install a solar system & that is SOLAR - GOD's way or its the highway. His response to me was that my system will not work & he would never install such a system for a customer BECAUSE my Lithium batteries do not have a proven 10+ year track record and he is not willing to risk his or his customers money - WTF does this circular reasoning have to do with reality - this is typical thinking of how people are stuck in their mind that its impossible to have solar air conditioning on an RV or Trailer. So just throw up your arms and give up right now, who wants to prove the experts wrong.
2.) The second reason is that RV air condition systems & lets be honest they are not the most energy efficient appliances in the world. First they sit out in the bright & hot sun on the RV roof and that can't be good. I have measured my trailer roof temp at easy 150 degrees and I would not want to be that working AC under those conditions. The RV roof ac units come in between 9,000 to 15,000 Btu and the larger ones suck 1,500+ watts, requiring about 4,500+ watts to even start - giving you about the same MPG as a 454 Chevy with quad 4 barrel carbs - somewhere under 6 -8 MPG. This is pretty sad for a time that we are using house AC systems that have a SEER 27 or in the most simple terms getting 27 MPG.. its not quite correct but its an easy example to follow.
3.) The third major reason is really batteries. Since 1850 they have been making the same old tried and true flooded batteries. Today there is a small twist with AGM etc and or no maintenance batteries but this is really still dressing the wolf in new sheep's clothing. 98% of all batteries world wide that are sold fall into this area, they are rated at 20 hour usage = X amount of AH. Example being L16 Batteries are rated at 400 AH if the power is drawn out at a steady 20 hour rate. But now they tell you don't use more then 50 -80% or you will kill the battery. So here we go with a real 320 AH battery. If you take out the power over maybe one hour you might get as little as maybe 120 AH. The math is simple a set of L16 400 AH batteries weight is 260 Lbs giving you maybe 120 AH x 12 volts = 1,440 watts about 1 hours worth of AC usage if your lucky. Here comes the real fun math, in order to recharge your L16 - you will need to add about 4,000+ watts until they are fully charged. No my math does not suck, its actually much worse then that because every time your energy goes from one piece of equipment to another - you loose 5-20% in heat and the conversion process, when the energy moves from the solar panels to the charge controller into the batteries then back to the inverter and finally to your AC system, its almost like the government having taxed away 70% of your power in the conversion process. This is the real reason why its impossible to have solar AC on your RV you would need about 4,000 watts in panels to keep your AC running.
Here is my real life example. I had 1000 watts in panels laying flat on my roof - generating about 660 solar watts on my charge controller at high noon going into my L16 batteries. Now on the out going side I had a small window ac using 450 watts, so that means I have an EXTRA 210 watts to charge my batteries, everything cool right ? WRONG. DEAD WRONG !! Lets check my math 400 AH Battery usable at 80% is 320 AH x 12 volts = 3,840 watts / by 450 watts ac usage = 8 hours run time for my AC now thats without ANY SOLAR !! so add in 660 watts in solar and I should be able to really kick some solar BUTT !! and have that sucker running on TURBO - RIGHT ? WRONG AGAIN !! To my shock here is what actually happened. I started the ac and it was running fine, the inverter stated I was using around 40 amps GREAT 40 amps x 12 = 480 watts PERFECT ! and to boot there was 660 watts coming in on the solar side...... YAHOO ! solar ac was now BORN in my little silicon valley garage - was I gonna become the next Apple ? I was soooooo HAPPY !! Overjoyed with my success, BUT wait disaster was about to strike... the ac started to sound a little strange - what was wrong ? I looked at the inverter it was now reading 55 amps and climbing WHAT ? thats impossible !! INSANE !! My charge controller was telling me 660 solar watts are coming in....I kept watching and listening to the ac while at the same time it was getting hotter inside - even with the cold air blowing from the ac...I was flipping out ....the inverter meter had climbed up to 85 amps being drawn by the ac after running about 60 minutes, the ac really sounded sick - i shut it all down FAILURE ! where did all the solar go ? what went wrong ? a thousand questions and 36 months work - all gone in that split second.....the experts were proven right running solar ac was impossible.
4.) The fourth major reason is RV insulation, as we all know cars when sitting in the sun get very hot - very fast 130 to 150 deg F easy. Well thats pretty much the same problem with RV's - most models do not have a large amount of insulation, usually only about 1-2" of fiberglass or something like that. The models with metal or steel frames tend to get hotter even faster then models made from wood which transmits the heat much slower. " Ever wondered why most trailer are made of wood?" From my experiments I have found that RV's pretty much track the exterior temperature very closely - even when parked in the full shade. If they are parked in the full sun or partial sun over 70 deg then they will receive additional heat load - just like a car. With a well insulated house the exterior temp may be 50 at night and 100 during the day, however the interior house temp will normally go from 65 to 80F during that time. With a typical RV the temp will go from 50 to 100+ exactly like the exterior temperature. Most all RV's have a min 13,000 Btu AC cooling system for lets say a 7 x 18' trailer or RV. A house in comparison that has a 10,000 Btu window ac which does about 400 sq ft, therefore a 13,000 Btu ac will do a min 520 sq ft house, however the your RV trailer is only 126 sq ft. So on a sq ft basis an RV uses 400% more heating and cooling vs your average house.
5.) The fifth major problem is COST..... everybody is screaming cost, it will cost too WAY TOO MUCH !! I don't really see this cost problem because there are people out there buying a $150,000 Air Stream MB van with not one watt of solar... so how can cost be a problem. I see people paying $8,000 for a dealer installed RV solar system that does almost nothing. People paying $50,000 for a home solar system when the cost of power is 15 cents a KW from the utility vs costing about $1.00 per KW for mobile power on the road. People are paying $1 million for a bus with a $20,000 generator and $40,000 in graphics on the side of the Bus.....People are paying $35 to $100 per night to go RV camping with 50 AMP hook ups, I just don't see how cost argument can be a problem ? $1,000 per month in rent inside an RV park can add up real fast when it comes to paying for a little solar system. What the hell if you get tired of having to much solar on your RV, you can always go put it on your house or maybe take it with you to the old folks home.
So here we have the 10,005 reasons why it is all but impossible to install solar AC to heat or cool an RV or Trailer, under the above conditions it is clearly impossible. BUT why do all experts approach the problem from this angle ? Come on this 2014 its been since 13 September 1959 when Soviet Union's Luna 2 mission landed on the moon, we are in the internet age 55 years latter, we have maybe 1,000,000+ houses using solar for their AC - what can be so hard that it cannot be done for one single RV or trailer, this was the question that really bugged me. Maybe approaching the problem from a whole different angle will make it possible.
This is how I approached the problem. When folks add solar onto their house - they call the solar guy, he looks at their $500 per month bill and with a big smile on his face he says YES - WE CAN HELP YOU ! with a $50,000 solar system to get your bill down 70%. Well that is 1,000% WRONG. First you should look at every possible way to make your house more energy efficient, more insulation, better windows, efficient appliances etc - all of these measures are more permanent and more cost effective, require less maintenance than adding solar to your energy hog of a house. My number one rule is "make your house as energy efficient as possible" once your house is a mean and lean energy efficient machine, then lets look at solar. I think with my approach you can save 30% or more on your solar installation & get your utility bill down to ZERO !
Not knowing anything about trailers or RV's I went to a form to see how the people there were doing their builds & followed their advice "BECAUSE" the all raved at how fantastic their 1" insulated trailers were. How they could camp at -20 deg F. How they could cool them with a 5,000 Btu window AC. When I was done - I realized that this was total 100% bunk.... It was the blind leading the blind and my metal ribbed trailer into which I had installed double the recommended insulation was hot as hell in the sun & freezing cold with dripping condensation from the ceiling when it was below 40 F outside. There was ZERO chance that this was ever going to become a Solar AC trailer.... So scratch trailer # 1 and back to the drawing board with a complete new plan. Searching the internet day and night of every trailer manufacturer i soon discovered, one egg was exactly like the next egg - almost like they copied each other with only the logo being different. Somewhere along the line I ran across a CarMate trailer and discovered that they were the only ones to build their trailer with a wood frame. I also knew from experience with installing insulation during Jimmy Carters time that wood transfers the heat & cold much slower then metal. This is how CarMate trailer became base for version # 2. This time around I now actually knew and had looked and every single component manufacturer that produced parts which go into trailers, I was able to actually pick the best trailer parts because I wanted the trailer to last a min of 100,000 miles and or 10 years while driving around the country.
Sometime around April - May 2013 began the 6800 mile round trip to leeper PA to get the current version. This time around just to be on the safe side I installed the best possible insulation Dow Blue board. The min is 2-3" to the floor, walls, doors - the roof has a R-19 Denim insulation as I knew from experience the roof can reach 150-180 deg F and since windows cause large amounts of energy loss or heat gain - no windows were included in this version. Ventilation would be provided my mechanical fans that can be opened and closed adding or removing exterior air for ventilation. This time the first problem was to attack the insulation and I also knew that if I got things right the entire trailer could be cooled with less then 5,000 Btu when parked in the full sun at 100 deg F - something that is all but impossible for a RV, trailer or Bus even with duel 13,000 Btu ac units running on the roof. One thing many people don't think about is that its actually much easier to keep a car or RV cooled while driving, then when parked - because the massive air flow reduces the exterior temp / heat flow from the vehicle. Rv's always head for the shade - like elephants head for water.
Once the interior was completed - now came the fun part of installing the solar to seeing if my theory was correct and if AC can actually be run with solar panels. If you try this yourself, you will soon find the same 10,000 experts who will tell you it can't be done and they don't really want to help a kook like you, so I was on my own - no book, no manual, no experts, no internet & no help !! This is how I ended up with 2,000 watts because surely having that much available for 4-5 hours per day would supply the needed power requirement.
more to come on this topic, stay tuned.
Its funny - right when you need some heat you never get it.
On a short side note I have been watching my AC power usage carefully with a watt meter and I'm averaging around 200 -225 watts per hour running the AC when the temp is 85 outside & I'm parked in the full sun cooling to around 74 deg inside. I did a test without me being inside, with the TV, fan & DVR off etc....the AC power use came to 125 - 150 watts. Over 5 hours thats only 750 total watts - this can be supplied by a single 250 watt panel - well beyond my expectations.