#99490  by landlubbers
 Thu Sep 10, 2015 1:59 pm
Thank you all for your responses to my enquiry. I have taken on board all your ideas. I am not electrically minded by any means, but I have spent this morning trying to work out how many amps I could be using in a 24 hour period. There is only two of us, mainly travelling around the middle to the north of the north island, probably once a month for a week or so each time. We run a compressor fridge, which according to the specs is 110 litre and is 5.9 amps per hour initially, then 2.1 amps per hour (have just rung Waeco and got these figures), we also run a tv for about 3 hours a night, the water pump and the lights. Our vehicle is a 2006 7 metre Ford Transit Talvor, ex Apollo rental. We have two in house batteries. We don't really use a lot of power, it is just the fridge usage we are concerned about.

The first retailer I spoke to yesterday suggested two 150 watt panels (he said to get one 150 watt panel first, and if that wasn't sufficient, to get another one and link them together and to change the regulator), and also said that mono crystalline panels were used mainly for the South Island (due to the lesser sunlight conditions), and to use the poly crystalline panels for the North Island. I couldn't make much sense out of that hence why I'm asking for actual experience from people who are out there doing it!

Also I'm just interested to know if it is a good idea leave your 12 volt fridges running all night?

Thanks again for all your help, it is much appreciated.
Last edited by landlubbers on Thu Sep 10, 2015 2:57 pm, edited 1 time in total.
 #99495  by muzzanic
 Thu Sep 10, 2015 2:43 pm
I know people that have had to spend quite a bit of time shifting panels around because they brought small & put them in the middle of the roof so no room to fit more panels.

What ever you do decide, try to put them were you wont get shading, Also try & make it so you can fit more at a later date when/ if you need it.

We leave our fridge going full time ( 12v only )

 #99498  by NeilV
 Thu Sep 10, 2015 3:48 pm
I would go with at least 250w to 'start with' as that is currently the best per watt price point. Also a good tip suggested to me was to plan my whole roof layout from the start, thus PLANNING both a potential upgrade path and also ensuring least likelihood of shading by arials and vents etc.

As someone above mentioned, you can't easily have too much solar, so buy as best you can now, and plan to have space for more if needed later?
 #99503  by Neddy
 Thu Sep 10, 2015 5:05 pm
Grant, there are a lot of unknowns in this equation, but let's look at the one thing we DO know. At 2.1 amps, your fridge draws more than double the power of my fridge so, for you, my 300 watts of solar power would not be enough. Your 24 hour power consumption is likely to be roughly 100 AmpHours. In Summer, this could be supplied by 400 watts worth of solar panels but in Winter it would take a lot more than that. I would therefore see 400 watt panels as being your baseline figure and given your aims, I would see no need to go over 500 watts.
Many of the posted estimates of the amount of solar power you need are hopelessly low.
You need 200 watts just to run your fridge. And that's in Summer.........

Why would you want polycrystaline panels when monocrystaline are better?
Blacklist the dude that recommended them.

Solar power is now really cheap. Take a long, hard look at your van's roof and see what you can fit up there.

Don't spoil the ship for a ha'porth of tar.

 #99513  by Desultory
 Thu Sep 10, 2015 8:18 pm
Don't forget that if you option to go for High Efficiency panels then you are able to buy a 260w, 265w or even 270w panel that only uses the SAME roof space area as a 240w or 250w panel.

Likewise it's possible to buy a 330w panel that only uses the same space as a 290w or 300w panel.

As some of the others have said solar prices per watt nowdays are SOOO much cheaper than they were even just 4 years ago, and it's one of those things that you never regret having slightly too much but yet it's easy to regret not having enough (and then hard & costly to easily upgrade if you are out of roof space area).

Typically a 250-270w panel will consume approximately 1.65m long x 1m wide of roof top space, and a 290-330w panel will typically consume 2m long x 1m wide of roof top space.

So first off I'd check out your roof space area and then work out IF it's actually possible to even fit 2 x 250-265w panels (or not) and if it was not possible to fit 2 of these panels on your roof top, then you may want to consider going for a single 330w panel instead (to provide the most amount of power possible from a single panel).

Back in the days there used to be a BIG difference between MONO and POLY Cell panels, but nowdays I can hoenstly tell you (because we supply both types) that GOOD Quality Poly panels are just as good as Most MONO cell panels and in fact many are better than budget MONO cell panels. Eg a 265w Latest Generation High Effiency Poly Panel (with Anti-Reflective Self-Cleaning Glass technology) will perform much better and give a higher output than a 255-260w MONO panel without that same technology (just to give you an example). I've personally done the back to back testing to test and confirm this also for those wondering.

Also remember a panel will only perform as well as the light can get through to glass to hit the cells, so if you get a panel with Anti-Reflective Self-Cleaning glass (essentially a factory applied slippery Nano coating) then it will help the panel stay cleaner for longer and absorb more of the light (instead of reflecting as much) which means that these panels can give MORE output per day than another of the same nameplate rating (that doesn't have these features).

Again this is my MY Personal opinions as as a Solar PV system designer who has designed more than 1000+ Solar PV setups for happy clients, but again it's down to what each persons personal preference is at the end of the day.

Hopefully my advise is of help to you, we've dealt with muzzanic and a few other members on here for a little while now and they all seem to be happy with the items we recommended & supplied for their RV setups.

 #99535  by idex
 Fri Sep 11, 2015 9:33 am
Steve, I'm really interested in the "Self-Cleaning" technology you talk about. I've been spraying "Wet'n'Forget" over our panels for years now and they do stay reasonably clean but I find the leaves, dust and other material still need a manual scrub occasionally. Do your panels do better than this? Does the nano-coating affect light transmission through the glass at all? What facts do you have to support your claims?
 #99549  by Desultory
 Fri Sep 11, 2015 2:48 pm
Hi Bruce,

Please have a read through this article online, it will better explain this technology for you.

http://www.pv-magazine.com/archive/arti ... z3lOT1xF9z

It was actually researched and developed by MIT researchers some time ago, and is becoming MORE common place on high quality PV modules. What is funny is that NOT all Solar PV panels come out with this special smart glass, it typically costs about an extra $14-16 USD more at time of panel production for the manufacturer to use this special glass, instead of standard solar panel glass.

Of course the way I think is that that's such a small price to pay at time of getting the panel made, that we'd be crazy not to buy all panels with the higher spec ARC (Anti-Reflective Self-Cleaning) glass, so that's what we do. Trying to put your own protection onto standard panel glass will typically cost around $120 (eg if you were paying for the Diamond Fusion coating guy to come and apply his coating to a standard 240-250w solar panel) so as you can see it's much more economical at time of manufacturer to just buy the panel with this technology already built in.

Typically as a general rule this is a "FACTORY UPGRADE OPTION" with most panels, and typically most 250w panels will NOT come with this glass as standard. As a general rule most 260w-270w panels (60 cell) and most 320-330w 72cell panels will come with this glass technology as standard, as it helps these high efficiency panels achieve such high outputs.

As per the article link above it states "A recent example is Dutch chemicals producer Royal DSM N.V., which has managed to push the performance of ARC designed for PV glass with its KhepriCoat technology, by increasing light transmission by 6%, resulting in 4% more panel efficiency. The material is applied as a very thin layer, up to 150 nanometers in thickness, by standard coating processes such as roll or slot die coating. Besides its excellent anti-reflective properties, KhepriCoat is extremely durable, able to perform outdoors for 25 years, to match panel lifetimes".

I hope that gives you guys some good reading to learn more about this technology and WHY you specifically want to be using panels that have this technology (rather than panels that don't) especially when it's not really costing much more, but yet over the lifetime of your panel on your RV it will pay for itself hundreds of times over with the extra output it gives you. I don't know about you guys but I'm certainly not a fan of jumping on the roof top and cleaning panels, so any technology that can help avoid that then for me it's worth it's weight in gold right there alone.

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