Solar Panel

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Solar Panel

Post by Saltyseadog on Thu Jul 20, 2017 12:21 pm

Hi everyone,

I'm new to this forum and owning a motorhome.  My wife and I have taken the plunge and are buying a new Autosleeper Symbol.  The specification we have asked for also included a living space air conditioning unit for the van which uses up the back roof vent.  I've just been informed by the dealer that in order to fit the air con unit I would have to have a smaller solar panel, only 40w instead of 80w, I'm a bit disappointed as this was not pointed out when I originally made the order.  Will this be adequate as we do intend to freedom camp occasionally and I'm not sure if this would be a big enough panel to top up the leisure batter.  Obviously I won't be using the air con unit unless we are on a powered site.

Thanks in advance.
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Re: Solar Panel

Post by -mojo- on Thu Jul 20, 2017 12:34 pm

Welcome to the forum.

It's been discussed quite a lot before, and the point that's generally made (with good reason) is that the size of solar panel you need depends on how much power you use! If you sit inside for hours watching TV then it probably won't be enough - especially if you plan to camp mid-winter. But if you just use LED lighting for a couple of hours each evening it may be Ok.

Personally, if I had to choose between habitation aircon and a decent size solar panel, I would choose the solar panel every time. To my mind the problem with habitation aircon is that you hardly ever need it in the UK, and if you go to places where it's hot all the time, the puny units that get fitted to motorhomes will be totally inadequate. But I concede that not all members of this forum would agree with that point...

Does the current Symbol still have a 3-way fridge (i.e. one that can be made to run on gas)?
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Re: Solar Panel

Post by Saltyseadog on Thu Jul 20, 2017 12:38 pm

Thanks for the info, we wouldn't tend to be watching TV that much so it would be mainly for LED lighting.  The Symbol does have a 3-way fridge so can run on gas.
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Re: Solar Panel

Post by meanchris on Thu Jul 20, 2017 12:41 pm

Is it possible to ask AS to pay special attention to the van's insulation? Both AS Execs we've owned have been a bit skimpy in this area to say the least.
Mojo's comment regarding the effectiveness of an air con unit may well be dramatically improved with the addition of a few quids worth of insulation in the right places at build time, as will the van's usability in winter.

I think that more attention could be paid to this by AS.

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Re: Solar Panel

Post by Saltyseadog on Thu Jul 20, 2017 12:46 pm

From what I've seen the insulation in the Symbol seems to be very good, it was a topic I brought up with the dealer.  Time will tell.  Looking forward to picking up the van next week.
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Re: Solar Panel

Post by -mojo- on Thu Jul 20, 2017 12:56 pm

The problem with solar, that A/S have to pay attention to, is that the panels are very very sensitive to shading - if just one small area of a panel is shaded by something taller (such as an aircon unit) nearby it drastically reduces the output - which limits the area in which they can place a panel.

If nothing else though, a 40W panel should be enough to keep your batteries topped up during periods of low use in winter - that alone is worth having, as it costs a lot of money to have to keep replacing batteries...
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Re: Solar Panel

Post by Saltyseadog on Thu Jul 20, 2017 12:59 pm

Point taken, obviously I'd have liked them to have stuck with the original 80W panel but I was informed today there is not enough room.  It's just a shame they didn't realise this when I made the order.
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Re: Solar Panel

Post by Gromit on Thu Jul 20, 2017 1:18 pm

-mojo- wrote:The problem with solar, that A/S have to pay attention to, is that the panels are very very sensitive to shading - if just one small area of a panel is shaded by something taller (such as an aircon unit) nearby it drastically reduces the output - which limits the area in which they can place a panel.
Hi Mojo
I may be talking rubbish (nothing new here then!!  Whistle1) but did I read somewhere that a MTTP controller can cope with partial shade on the panel far better than a PWM?

If so, that could be an option for SeaDog, plus he would get at least some increase in efficiency with the more sophisticated (and expensive) gadget.

Also I guess he would often be able to park with the sun in mind if something was likely to shade his panel. If there's physical space, wouldn't it be better to have the bigger panel for those times when it was beneficial - or two small panels if roof space needs to be juggled?

Don't know, but it seems as if they can't be bothered to work around a solution - or am I being too cynical? Whistle1 

I'm as dim as a Toc-H lamp when it comes to electronics, but I'm sure there must be alternatives.

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Re: Solar Panel

Post by IanH on Thu Jul 20, 2017 2:10 pm

Hi

Personally I wouldn't consider a 40w solar panel worth having, as an aside I wouldn't want the roof ac either!!

You have some options however. Google Photoninc universe and look at their semi flexible panels, they do a long and narrow 50w one which may allow you to use 2 to give you a much more useable 100w.

If, however, not too late, bin the hook up only usable ac unit and cover the roof with solar!!!

allthumbz
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Re: Solar Panel

Post by -mojo- on Thu Jul 20, 2017 5:24 pm

Gromit wrote:
I may be talking rubbish (nothing new here then!!  Whistle1) but did I read somewhere that a MTTP controller can cope with partial shade on the panel far better than a PWM?

If so, that could be an option for SeaDog, plus he would get at least some increase in efficiency with the more sophisticated (and expensive) gadget.

There is certainly some basis to the suggestion that an MPPT controller is better able to cope with shaded panels, but my understanding is that this is more relevant where you have multiple panels in parallel, some of which are shaded and some not. Within a single panel it is not so easy to make gains with MPPT because the cells are either partly or entirely in series, where one shaded cell has a detrimental effect on all the other cells in that series "chain".

However, as Ian points out, there is a greater range of shapes and sizes available now than ever before, so it may be possible to find one or more that will fit the available space better. When I bought mine there was at least one Chinese company that claimed to be able to supply individual panels in specific shapes and sizes - though in the end I went for a standard panel.
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