Solar Panels - why are some so much more expensive than others?

Houleaux

Houleaux

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I'm considering installing a solar panel and know little about them.

Semi-flexible seem to be the most practical for me, but the prices for apparently similar spec panels vary hugely.

Can anyone explain why the 70w semi flexible kit on this page http://www.midsummerenergy.co.uk/buy/solar-panel-kits/,for example, is so much more expensive than the 100w one here http://www.bestecoshop.com/100w-semi-flexible-kit-with-10amp-waterproof-controller-5m-cable.html?

Also, am I wasting my time if I fit one on the cockpit hatch garage - i.e. under the boom - because of the shade it will inevitably get?

Thanks.

Rob
 
I have a couple of rigid PV panels on the hatch garage and they do the business ok, at least in the summer months. It is a common place to mount them and if it doesn't interfere with mast access is an efficient use of space.
 
You could also mount them outboard of the guard wires pivoting from the top wire. Something like solar dodgers.
 
The difference in price is because the Chinese ones are less expensive than the European ones. Over time the output diminishes from solar panels but they haven't been around long enough to find out if the expensive ones last longer than the cheaper ones. In the short medium term both keep the same output. Told to me by a solar installer.
 
Houleaux said:
ICan anyone explain why the 70w semi flexible kit on this page http://www.midsummerenergy.co.uk/buy/solar-panel-kits/,for example, is so much more expensive than the 100w one here http://www.bestecoshop.com/100w-semi-flexible-kit-with-10amp-waterproof-controller-5m-cable.html?
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Both of these look pretty expensive to me. I spent ages this spring investigating semi-flexible panels as I wanted to fit them to my hatch garage and coachroof, both of which restricted the size possible. The conclusions I came to was that there are basically three categories around. First of all, the cheap and cheerful (typical manufacturer: Lensun) which come in at about £2/watt and use simple,established technology. Then there are the slightly more upmarket, at £3/watt which gets you the latest mass production technology (eg back contact) in its early stages. Both of these come in simple plastic packaging. the third sort gets you super-tough ribbed protection on top, so much more rugged ... but at anything from £5/watt up.

In the end I bought two 50W panels: a cheap-and-cheerful (Chinese made) at £100 and a back-contact (US made) at £150. My decision was driven more by size than anything else: the biggest cheap-and-cheerful I could fit on the hatch garage was 30W.

There are a lot of resellers around who charge a huge markup, and both of the links you give look to me as if they in that category. I was very impressed by Barden prices but in the end bought from Remytek (cheaper panel) and Photonic Universe (dearer panel). I'd suggest having a good trawl through eBay ... you'll soon recognize teh various panels available from their sizes.

One word of caution ... semiflexible panels can be plastic or aluminium backed. The aluminium ones really aren't very flexible at all, and are normally quoted as allowing 3% curvature - ie one end of a 1m long panel can be 3cm below the tangent the other end. That's not enough for me, so I was very please to find a Chinese importer whose panels allowed 30o curvature, and bought a pair. When I got them I found they were far too rigid, and it was obvious that at some point along a trail of translation 3% had become 30o. The importers were fine, and refunded in full, but the moral of this long ramble is that aluminium backed panels are only just flexible.
 
JumbleDuck said:
.....

One word of caution ... semiflexible panels can be plastic or aluminium backed. The aluminium ones really aren't very flexible at all, and are normally quoted as allowing 3% curvature - ie one end of a 1m long panel can be 3cm below the tangent the other end. That's not enough for me, so I was very please to find a Chinese importer whose panels allowed 30o curvature, and bought a pair. When I got them I found they were far too rigid, and it was obvious that at some point along a trail of translation 3% had become 30o. The importers were fine, and refunded in full, but the moral of this long ramble is that aluminium backed panels are only just flexible.
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Thanks for your informative post JD :)

Am planning to get a couple to hang off the guard rails in place of the dodgers so for me I am not concerned about flexibility, in fact rgid would probably be best as I want to devise a way of angling them up when we are not sailing. Do you think I am right in thinking that plastic backed panels would be best for a marine environment ? Have visons of the aluminium oxidising after a year or two.
 
Storyline said:
Thanks for your informative post JD :)

Am planning to get a couple to hang off the guard rails in place of the dodgers so for me I am not concerned about flexibility, in fact rgid would probably be best as I want to devise a way of angling them up when we are not sailing. Do you think I am right in thinking that plastic backed panels would be best for a marine environment ? Have visons of the aluminium oxidising after a year or two.
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My older panel is 5 years now. It is anodised-just like my mast and boom-and is as good as the day I fitted it.

I used the Duralac yellow paste to stop galvanic corrosion between the alloy and S/S fastners.
 
Thanks all for your help.

The Photonic Universe site has lots of useful info thanks Jumbleduck. Looks like I can get all the bits for a 100w set up using 2 semi flexible panels and an MPPT controller for about £300. I gather that this controller will enable the panels to be connected in series which should be more efficient, but please tell me if I'm wrong!

Can anyone tell me from their experience what sort of charge current I can reasonably expect from a 100w set up in the UK - in summer sunshine and winter cloud, for example? Or, better still, how many Ah per day in summer and in winter?
 
Houleaux said:
Can anyone tell me from their experience what sort of charge current I can reasonably expect from a 100w set up in the UK - in summer sunshine and winter cloud, for example? Or, better still, how many Ah per day in summer and in winter?
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I would suggest you think in terms of half the stated max output for perhaps 6 hours/day in UK mid summer. Practically nothing when overcast. Even this assumes your panel is actually facing the sun without ANY shadows. Ideal is probably a panel mounted horizontally on a tall arch with as little potential for shading as possible. Failing that mount one on the coachroof/guardrails either side and accept that only one will ever be working efficiently, and sometimes neither!

One idea is to buy a small, cheap, framed panel (about £15 for a 10w panel on ebay) and play with it. You will learn a great deal about how orientation, shadows, etc affect performance in the real world.

Having said all that, my two 40w rigid panels, one either side on the coachroof, have revolutionized my onboard power:encouragement:
 
Storyline said:
Am planning to get a couple to hang off the guard rails in place of the dodgers so for me I am not concerned about flexibility, in fact rgid would probably be best as I want to devise a way of angling them up when we are not sailing. Do you think I am right in thinking that plastic backed panels would be best for a marine environment ? Have visons of the aluminium oxidising after a year or two.
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In your situation I'd use aluminium backed. The metal is quite thick, and I think they would survive a lot better than floppy plastic ones, while being a lot thinner and lighter than rigid.
 
Houleaux said:
Thanks all for your help.

The Photonic Universe site has lots of useful info thanks Jumbleduck. Looks like I can get all the bits for a 100w set up using 2 semi flexible panels and an MPPT controller for about £300. I gather that this controller will enable the panels to be connected in series which should be more efficient, but please tell me if I'm wrong!

Can anyone tell me from their experience what sort of charge current I can reasonably expect from a 100w set up in the UK - in summer sunshine and winter cloud, for example? Or, better still, how many Ah per day in summer and in winter?
Click to expand...

As I said, I have 2 x 50W panels. The power is quoted at maximum panel voltage of ~20V, and I have a PWM regulator rather than MPPT, so the most I could ever expect to see going into the batteries is 5A. In practice the most it has ever produced, according to the controller's remote display was 4.1A. With the batteries a bit run down I have see 4.0A in bright sunshine; 2 - 3A is more common, though that may result as much from the a batteries not being terribly flat. On a cloudy bright day (f5.6, as the film instructions used to say) I get an amp and even on dull days it seems to give me 500mA or so. Not much, but over a few hours it's fine.

I run almost all LED lights (one mini fluorescent over the galley), a rather power hungry old set of B&G instruments (4A), occasionally a VHF radio and keep a Netbook, a phone and a tablet charged. The house bank is 2 x 60Ah. In five weeks over the summer I never had the slightest problem with electricity, so as far as I can see my set up is producing as much as I ever need. Or was producing ... I am about to spend a scottish autumn half-term week on board. We shall see.
 
I've gone for the £1/watt eBay cheapie panel- well actually £45 for a 50w rigid polycrystalline. So far it is proving very, very good; I will see how it lasts in the long run. I have it mounted on the hatch garage using a length of bungee threaded through holes in the aluminium frame. The bungee is then secured to some hooks that were already on the hatch garage, and it seems very happy there through all weathers, however in a few seconds I can unhook it and sit it somewhere to catch the sun at the best angle.
 
Thanks JumbleDuck. That's really helpful. Encouraging too, as our electricity demands are quite modest.

I'm amazed at the power consumption of your instruments. Our Stowe stuff (hardly state of the art) plus a CP180 chartplotter only consume 1.2A according to our BM-1.
 
Houleaux said:
Thanks JumbleDuck. That's really helpful. Encouraging too, as our electricity demands are quite modest.

I'm amazed at the power consumption of your instruments. Our Stowe stuff (hardly state of the art) plus a CP180 chartplotter only consume 1.2A according to our BM-1.
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I'm petty sure they are about 4A when everything is running. Years ago I sailed in a Sigma 33 which had one of the very first GPS sets. It was a huge thing and it used so much power that we had to run the engine for several hours per day just to keep the GPS running.

But I digress. It sound to me as if 100W installed will do you just fine.
 
Houleaux said:
Can anyone tell me from their experience what sort of charge current I can reasonably expect from a 100w set up in the UK - in summer sunshine and winter cloud, for example? Or, better still, how many Ah per day in summer and in winter?
Click to expand...

In my experience this rule of thumb is about right: For a panel mounted flat on deck, during the summer months (May-Aug) in mid/northern Europe: Expect 25 percent in Ah of the rating in Watts per day as an average (mix of sunny and less sunny days). So in your case: 25 Ah/day in summer. In winter: Quite a lot less.
 
Keeping an eye on this thread cos i am also considering fitting a solar panel just behind the mast.
Going on max size the best fir i can find is the Photonicuniverse 30w one.
I wrote to them enquiring about shade tolerance , here's what they said:-

[FONT=&quot]"We don’t sell amorphous panels, so I can’t really tell you much about the difference between an amorphous panel and mono/polycrystalline panel in terms of shade tolerance.[/FONT]

[FONT=&quot] [/FONT]

[FONT=&quot]What I can tell you is that the solar panel that you are initially inquiring about is monocrystalline, which is better than polycrystalline at absorbing solar energy, and it also uses back-contact solar cells; this means that the metal strips that you see on the front of regular panels are behind the solar cells, so that there isn’t any shade cast over the solar cells from the metal strips.[/FONT]

[FONT=&quot] [/FONT]

[FONT=&quot]These solar panels will absorb more solar cells than an average solar panel, even in the shade. Also, if you use a 10A MPPT controller to regulate this panel, the current from the panel to the battery will be boosted. If the panel is going to be in the shade for long periods of time, then you may want to consider getting an MPPT controller:[/FONT]

[FONT=&quot] [/FONT]

[FONT=&quot]http://www.photonicuniverse.com/en/...er--regulator-for-up-to-100V-solar-input.html[/FONT]
[FONT=&quot] [/FONT]
[FONT=&quot]Please let me know if there’s anything else that you’re interested in.[/FONT]"

To me this does not really answer the question but it is interesting.

Will watch the thread with interest.
 
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