I am trying to get the info together to build a much smaller trailer than your 6’ X 12’ that you describe in your article. What I had in mind is something that could power, let’s say, a RV-sized refrigerator or refrigerator/freezer combo via 12 volt, or 110 /120 volt using a small bank of batteries, a small solar array, and very likely a small generator….gasoline or propane-powered.
It is my intent to use this trailer for fairly remote camping, and it must be small enough to go over fairly narrow trails, and being light and small enough to be pulled by a 4-wheel drive ATV.
I have not gone through the thought process far enough to determine if this trailer needs to be dedicated to the energy aspect alone, OR could the trailer also double as a trailer for all of the various and sundry camping gear that we all want, such as: tents, ice chests, folding chairs, etc., etc.
If I could find a ‘recipe’ that would include sizing, wiring, and other ‘engineering’ issues, and WHERE to buy these pieces of hardware. Well, that is my goal.
Can you / will you help?
I appreciate anything you can do.
Ron Jackson
Ron:
You should be able to do this without any problem. The trailer could be only 2 or 3 feet high with access doors on each side and back. Several doors could access the batteries and solar hardware, others could be tent storage and camping supplies. The solar array could lay flat on the top and could fold out when you get where you are going. Pick the trailer size and type that works best for your other needs and adapt for the solar equipment.
If you plan to actually provide much solar power, you will still need a solar system at least close to the size of solar array, batteries, and hardware that I used in the article, but you can cut down the trailer height and width as needed.
I have ordered a trailer, and am in the process of replicating the one you built.
In researching inverters, I contacted Xantrex, intending to find out what I could about a ‘true sine wave’ or the SW series. They have discontinued them; it was recommended to me to use a Prosine 2.0, but the individual who responded did not seem to be aware of any application for a mobile trailer…in fact, also recommended a replacement for the SW series that was for residential use, and said that ‘modified sine wave’ inverters were being used by their customers for computer power. I suspect that there is some additional conditioning for a residential application between the inverter and the computer.
Since I would like to be able to power anything in my house that the trailer will provide adequate power for, are there current units in production you could recommend? Not being an electrician (just a jack of many trades), I intend to almost exactly duplicate your trailer (using a smaller fridge, and a Honda generator i already own). I am trying to avoid ‘overbuying’ or mistakenly getting some part that will not work.
Thanks for any help and/or advice you can give :) I thought your trailer was a brilliant idea…2KW of power in a complete outage (which we get from time to time) is far preferable to ‘no KW’…i have an American Ingenuity dome house-approx. 800 sq ft on lower floor, and putting panels up would be a nuisance, not to mention the problem with battery storage area.
Elton Wylie
Elton:
Glad you liked the article. You are correct, the SW series sinewave inverter line has been phased out and many of us are sad to see this guy go as it is the only inverter out there for small applications that came standard with two built-in automatic transfer switches – one for grid power and one for backup generator power. Xantrex has replaced this product line with their new XW series inverters. These are really great, but are definitely high dollar products for larger residential grid connected, grid-ties, and off-grid applications.
Most modified sinewave inverters will power a computer without any problem, but some appliances like a microwave oven will not heat very well and some televisions may have a reduced screen size when powered from a modified sinewave inverter. I actually had some X-10 type remote controlled light fixtures have a melt-down when powered from a modified sinewave inverter, and X-10 wall switches that actually were hot to the touch. Some battery chargers do not charge properly when powered from a modified sinewave inverter. Although they cost more, a true sinewave inverter is your best bet.
However, having said all that, my article describes the system I built using a sinewave inverter from Outback, not Xantrex, and the Outback sinewave inverter line is still going strong with several sizes to pick from.
I’ve been working on a solar trailer design similar to yours for a few months now. I really loved finding your article last month. I also plan to generate a surplus of power to help out at a group camp, event or disaster.
Is there a way I can plug the trailer in to supplement my home electrical supply to knock down my electric bill when the trailer is sitting unused at home?
Thanks,
Steve Sonntag MD
Lame Deer, MT
Steve:
The short answer is yes, the long answer is this may be more trouble than its worth. Your state has had a net metering law since 1999, so it is legal for a homeowner in Montana to sell back to the utility. However, each state has allowed the local utility to set up specific requirements that must be met to ensure the safety of their service people and the quality of the power for the other customers.
Normally, in most states these requirements include filing a form with the local utility that describes the system, the installed hardware, indication that this equipment meets grid-interaction safety requirements (usually listed on nameplate), and the wiring into the electrical system was completed by a licensed electrician who also signs the form. Some states also add the requirement for an exterior dis-connect with a lever handle that can be locked-out by their service people. Again, these requirements vary from state to state, and you can contact your local utility for more information.
However, it does not matter that the source of the power that will be “back-fed” into the utility line is coming from a portable trailer, you will still need to meet most if not all of the states requirements just as if the solar system was mounted on the roof of your home. THey may omit the dis-conect at the meter since you or they could “un-plug” the trailer from the house, but I am betting this will be too complex a decision to make for the non-technical person you will most likely be dealing with and they will still insist on meeting all of their requirements.
Keep in mind that many inverters will meet the requirements for grid-interconnect and can easily be switched manually over to the “sell” mode. However, your trailer will most likely only have an “input” cable to allow charging the batteries from the house or a generator, so your trailer will need a second cable to connect its output to the house and this should NOT be a standard “male” plug with exposed pins since these exposed pins will be HOT at 120 or 240 VAC, depending on the model inverter you install.
If you want to stay “legal” but not go through all the hoops, why not just run a heavy extension chord from your solar trailer into your home and plug in a few appliances like a freezer or other load that closely matches the output of your trailer. This will remove this load from your utility bill, yet keep your trailer wiring from connecting into the other house wiring.
I heard about a 30 amp solar collector that was built on a trailer. I thought by Independent Energy Systems. But I can’t find them and was wondering if you had any info. on portable solar collectors.
Thanks
Matty
Matty:
Not sure what you mean by a “30 amp solar collector”. This is not usually how we reference their capacity. If you are talking about a “30 watt” solar collector (we call them solar “modules” if the generate electricity, and solar “panels” if the make hot water), but a 30 watt solar module would be about 10″ X 36″ in size so it would not need a trailer. If you are talking about a 30 kW solar array, this would definitely require a semi-tractor trailer to move around as it would be over 90 feet long.
If your interest is trailer mounted solar power systems in general, check the next issue of Backwoods Home Magazine (#108) as I will have a 2-part article on how to build your own using a 6 ft X 12 ft enclosed utility trailer.
I’m hoping to develop a low tech, low cost solar water heater for use in a camper van. As such, it needs to be capable of supplying sufficient hot water for showering and dish washing for a family of four.
Assuming two daily wash-ups, and each family member showering perhaps every other day (we are roughing it in the great outdoors after all), daily water usage should be fairly small. I’ve seen the commercially available ‘Solar Shower’ bags, and have read about water-filled truck inner tubes and the like, but I’d like to develop something a little more sophisticated, if only to impress my (slightly more smelly) campsite neighbours!
Initially, I planned to make an open thermosiphon type system, utilising an insulated ground level collector, incorporating a secondhand refrigerator matrix, with a suitably sized storage tank sited on the van roof. This would be fine assuming we’re pitched up for a day or two- more often than not, we’re on the move for much of the day, and pitch camp in the evening- so any system would need to be permanently installed in/on the van and capable of making use of the sunshine on the move during the day.
Due consideration would have to be given to reducing the effect of cooling air passing over the collector while driving, but would a closed, pumped glycol based system, with a heat exchanger and on-board storage tank be feasible?
What precautions would I have to take regarding temperature and pressure build up, and how would one calculate the various capacities involved?
As you may have guessed, this idea hasn’t even reached the drawing board yet, but I’d be keen to hear your views, even if it’s to dismiss it out of hand!
Back in the 1920’s and 1930’s Florida did not have any piped natural gas or propane, and those homes with electricity back then usually only had one or two 15 amp fuses for lights and the radio. The did not wire homes for large electric hot water heaters. Therefore, almost every family home in Florida during this period had commercially made solar hot water heaters. They located the solar panel at the lowest part of the roof just up from the roof eve, then they cut a hole in the roof at the peak and stood up a hot water storage tank. They piled insulation around this tank which stuck up above the roof eve then fabricated a fake chimney around it to hid it. They did this so the tank would be much higher up than the solar hot water panels which allowed thermo-syphening and did not require a pump. Back in the late 1970’s we removed one of these old solar hot water heaters from an older Florida home that was still operational and replaced with a new system.
If you also want to use a thermo-syphen system, you must have the solar module as low as possible and the storage tank as high as possible. If you operate in colder locations you will need some type of anti-freeze. However, commercial solar hot water heaters are required to use a double-wall heat exchanger due to the danger of the heat exchanger getting a leak inside the storage tank and letting anti-freeze leak into water you could be drinking. Ethylene-glycol (automobile anti-freeze) is very poisionous, but propolene-glycol (red food coloring) is not poisionous and this is what they sell in RV stores for winterizing an RV. The problem with any system that uses anti-freeze is this reduces the heat transfer efficiency of the water mixture, so there is a down-side if you must prevent freezing.
If you can utilize a small DC powered pump, you will not need any anti-freeze. You have a small insulated non-pressurized holding tank just below the elevation of the solar panels. When the sun starts heating the panel, the pump is turned on and moves water up into the solar panels flowing from the bottom to top. When the sun goes down the pump shuts off and all the water drains back into this small holding tank, which is NOT the hot water storage tank. Your hot water storage tank will need a heat exchanger for this heated water to pass through as it moves back down from the top of the solar panels through the heat exchanger then into the small drain-back tank.
They also make special controllers that you connect a temperature sensor on the solar panel and the other in the hot water storage tank and it will turn on the pump anytime the solar panel is hotter than the water in the tank.
Since the solar panels are empty when the pump shuts off, there is nothing to freeze.
There are lots more to the design of these systems, but this should get you started.
