#180170 - 08/23/09 04:25 PM
Solar Electricity, A RV'ers Perspective. (Preface)
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Addict
Registered: 05/04/02
Posts: 493
Loc: Just wandering around.
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Preface:
Gloria and I live in a camper. We have no other home. We left Maine in August of 1997 which makes this out 13th year on the road. Our preference is for the wild places. Of course there is no electricity in the wild places, so we have become very dependent on our solar electrical system.
For the most part, we have enough power to live a normal life. We have a 22” flat screen TV. Our internet connection is via satellite. We both have amateur radio licenses and use radio a lot. Our computer network uses power and so does our reverse osmosis water system. Because I did stupid things on motorcycles, I need to use a breathing machine (CPAP) when sleeping. All of this uses power.
My background is in technology and my work provided ample opportunity to learn about batteries and such. In Maine I had a very large battery bank driven by solar cells, so I have been messing with this stuff for a long time. Hopefully I have gained some useful information and techniques.
Powering a RV with solar has some unique issues. It is different than powering a home. So what I will provide here is my perspective on RV Solar.
I appreciate the opportunity to present this to the Equipped group for critical comment. I intend to eventually put it on my web site where it will be easy to maintain, edit and add pictures. It is a work in progress and I sincerely appreciate discussion on the topic.
I have done a bit of technical writing I had an editor that repaired my typos and misplaced punctuation. If you are a habitual proofreader I would welcome your corrections. Please do that via private e-mail so as not to clutter up the dialog. Use n1ahh.ron@gmail for that and any other comments that do not need to go to the whole group.
I will post this is sections so questions can be asked and discussed. So lets begin at the beginning.
---Nomad---
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#180171 - 08/23/09 04:40 PM
Re: Solar Electricity, A RV'ers Perspective. 1.
[Re: Nomad]
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Addict
Registered: 05/04/02
Posts: 493
Loc: Just wandering around.
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Solar System Description:
A solar system consists of several components
A solar array, sometimes called a photo voltaic (PV) array. This consists of one or more solar panels wired together in one of several ways (discussed later).
Wire: The most overlooked part of the system. Do this part right and it will make a great deal of difference.
Solar Controller: Electricity from the solar panels must be regulated before it gets to the batteries or they will overcharge and be destroyed. The solar controller oversees the charging process.
Batteries: A very complex subject. There are lots of types, models and technologies to consider.
Inverter: The electricity in the solar system is DC or direct current. Many appliances need AC or alternating current. An inverter changes the DC to AC.
Metering: Although the system basically runs itself, you need to know how much power you have available and you need to monitor the system to detect any problems.
The components, one by one:
Solar Arrays:
Panel types:
There are several types of solar panels. Some of the characteristics include, power output per square inch, break ability, shadow performance , and cost,to name a few.
Basically they fall into two groups. I will call them Mono-crystalline (MC) and Thin Film (TF) .
Mono-crystalline(MC) are the most common type. The array consists of many individual cells wired together to form a panel. MC are cheaper and provide more power than Thin Film (TC) panels.
The disadvantages of MC are that they are more fragile, they do not have diodes between each cell and therefore have a severe power loss when even partially shaded and they do not produce as much energy when the sky is overcast or in other reduced light situations.
The cells are sandwiched between an aluminum support sheet and a tempered glass covering. They are rigid and although the tempered glass is pretty strong, can be (and frequently are) broken when used in the RV environment. The cells are mostly sensitive to visible light with limited production under ultraviolet and infrared light.
Thin Film(TF) panels are used in severe service environments. Marine and military applications are the most common. TF panels are one continuous multi-cell layer, sliced very thin and then bound with other thin films to produce a multi-layered surface.
Each cell within the film has a diode between it and the other cells. This diode greatly reduces the effect of shading. The thin film layers are flexible and can be put on rounded surfaces. They are covered with a very strong plastic protective layer. Mine have many large gouges and “pings” from hitting trees, dropped wrenches and other hazards that would have destroyed the glass covered MC panels.
The multi layers are sensitive to different wavelengths of light, allowing much better performance in overcasts where the amount of visible light is reduced but light of other wavelengths remain high.
There are two major disadvantages to TF panels. One is their lower power output per area. I have TF panels and they occupy about twice the roof real estate the MC would occupy for the same output.
Second, TF panels cost about twice the price of MC panels for a given output. My 64 watt panels cost about $350 each whereas a 120 watt MC panel would cost about $550. These are old prices, all have gone up considerably but the same ratio of costs remains.
Next: Mounting the Panels.
_________________________
...........From Nomad.........Been "on the road" since '97
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#180176 - 08/23/09 05:31 PM
Re: Solar Electricity, A RV'ers Perspective. 1.
[Re: Nomad]
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Veteran
Registered: 11/01/08
Posts: 1530
Loc: DFW, Texas
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Next slide please...
This has just recently come to the front of issues for me, and I need to have something going in the next week or so.
_________________________
I do the things that I must, and really regret, are unfortunately necessary.
RIP OBG
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#180196 - 08/23/09 10:19 PM
Re: Solar Electricity, A RV'ers Perspective. 1.
[Re: Todd W]
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Addict
Registered: 09/08/05
Posts: 662
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Great post so far Nomad, keep it coming. I can relate to the 2 type panels, I have both as well and I am more to the thin film when traveling and my thin film definitely works really well in clouded conditions. I use a 20 watt TF to keep my truck charged in storage and I can go to my truck 6 months later and it fires right up with the battery. I am hoping as technology improves that solar comes down in price, I'll be all over that. Wind mills and solar, unfortunately turbines won't work well here due to the lack of constant wind. but we have plenty of sun.
_________________________
Failure is not an option!
USMC Jungle Environmental Survival Training PI 1985
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#180214 - 08/24/09 12:45 AM
Re: Solar Electricity, A RV'ers Perspective. 1.
[Re: Am_Fear_Liath_Mor]
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Product Tester
Pooh-Bah
Registered: 11/14/04
Posts: 1928
Loc: Mountains of CA
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Do you mean something like this.   900 Watts of Solar PV with solar tracking and combined 6500 Watt Backup Generator and battery bank giving 4KW of power. http://www.mobilesolarpower.com/ Not really... I have a 5kw/generator in the RV already which is more than enough. I was just curious if they have 1-3 panels or something mobile to move 100ft away and keep the batteries juiced up. That looks like something to keep your entire house juiced up or an entire camp.
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#180215 - 08/24/09 12:50 AM
Re: Solar Electricity, A RV'ers Perspective. 1.
[Re: Todd W]
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Addict
Registered: 07/04/02
Posts: 436
Loc: Florida
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ToddW,
One caution to be aware of when adding distance between the solar panels and the battery banks, every inch of conductor (wire) added to the overall length comes at a price called VOLTAGE DROP. In the case of lower voltages and direct current, this can be a steep price to pay.
You will have a minimum to two conductors to complete the circuit) and this will increase the overall circuit voltage drop due to increased conductor resistance. Thus, if you locate your power source 100 feet from your load (in this case your battery bank/s) you will have 200 feet of conductor overall creating added resistance to your circuit supply voltage and creating voltage drop
Within certain practical standards this concern can be addressed by increasing the conductors cross sectional area by using a bigger conductor (i.e. going from a small wire #18 wire gauge to a larger #10 wire gauge). With proper up front planning / engineering this can be addressed within the limitations of your physical layout and available budget.
The trade off comes in practical aspects such as CO$T, flexibility, weight, handling time etc. With electrical circuits as in many other aspects of our lives, "there ain't no such thing as a free lunch".
Regards,
Comanche7
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#180224 - 08/24/09 02:00 AM
Re: Solar Electricity, A RV'ers Perspective. 1.
[Re: Desperado]
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Addict
Registered: 05/04/02
Posts: 493
Loc: Just wandering around.
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Next slide please...
This has just recently come to the front of issues for me, and I need to have something going in the next week or so. Well I won't get it done that fast. You might want to PM me with details and we can go from there. You do Skype? No cell phones etc where we are, but happy to do a video chat via skype I just cleared a nice area for my RV and realized I have a small problem... it's under very tall pine and oak trees and gets little sun. Sure, I could have parked it in the sun but then I have to deal with the heat, and problems associated with items left in the sun for long periods of time.
What do you for this scenario? Comanche7 is right on about the wire length. I have not gotten to that part yet, but at 100' the wiring would be a real issue. The work around is to put the panels, a controller and a battery at the remote point. Add a small inverter and do the 100' run with AC, then put a charger in the RV. It will work, but it will be less efficient. However since you will probably not have a large demand unless you are living in the RV it may suffice. You would be better off running AC from the grid (if it is available) to charge your batteries than trying to use solar. Will the camper be in "storage", occasional use or being lived in? Nomad
_________________________
...........From Nomad.........Been "on the road" since '97
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