Life span of amorphous solar panels

I have just taken delivery of a 62 foot narrow boat, and very interested in the Unisolar adhesive backed panels. However on the Free Solar Energy UK web site it says 'these panels offer ease of fitting but due to being based on cheaper silicon,don't offer the same efficiences and typically need replacement every 5 years- these degrade fast.' Your comments please as I am a little confused. Paul.

That's nonsense - Unisolar offer a 20 year warranty on the power output of the panels. Why would they do that if they only had a lifetime of a few years?! I've used Unisolar panels on the roof of my own narrowboat for over 5 years and haven't noticed the slightest loss of power from them. I've found them exceptionally good value.

It is true that some of the early 'thin-film' solar panels had a significantly shorter lifespan than conventional silicon panels. But it's just not true of the current Unisolar amorphous range. I'm sure you will be very happy with them if you do go for them!

Glass-glass laminate solar panels

We have a south facing conservatory with an angled double-glazed glass roof.  We are thinking of replacing the glass roof with solar panels (which produce electricity) but are struggling to find the right product.  The sticky panels you sell might be an option depending on weight. But do you know of a product which would replace ordinary double glazing with similar thickness (and weight) glass panels which have integrated PV cells?

Yes, it is possible to get solar panels that are glass-glass laminates - ie the solar cells are sandwiched between two sheets of glass - rather than between a layer of glass and a sheet of metal or plastic, which is more normal in framed panels. See http://www.solarcentury.co.uk/products/low_carbon_building_products/solar_glazing for more details.

Glass-glass laminates are effectively double glazing with integrated PV cells, which sounds like exactly what you want.

The adhesive-backed panels are not particularly heavy incidentally. I shouldn't imagine the additional weight would be a problem on most roof structures if you wanted to consider them instead.

Solar panels for 120Ah per day usage

Your suggestions please for solar panels for a narrowboat with 675Ah battery bank and 120+ Ah daily demand
Thankyou, Alan

120Ah per day is a fair demand, so I would first try to reduce demand to make things as efficient as possible! If you have a look at our solar panel calculator, in part three you can put in the power output from a solar panel array and see how much you can expect to get from it. So the 64W panel that is there for an example will give you around 26Ah in summer on average, going down to around 5Ah in winter.

The adhesive-backed solar panels we sell are definately the neatest solution. Great for narrowboats. The Unisolar or Kyocera framed panels are a little cheaper, but are not as discreet or so easily mounted. Personally I would go for four of the adhesive-backed panels, with a Prostar 30A controller - I would expect those would make you nearly free of other charging sources in the summer, although you would still need to top up by other means in the winter.

Temperature dependence of Unisolar solar panels

I am interested in your Uni solar products, but I need a little advice.
I have a 50mm thick foam insulated (on the inside) flat, smooth, steel roof onto which I would like to mount two panels. The framed version needs to be raised and ventilated underneath for best results, but the self adhesive version must get much hotter being dark in colour and unable to dissipate heat from underneath; indeed, I understand that it must not exceed 85c.
My question is: Given that the PVL68 will get a lot hotter when compared to the framed version, how much difference in efficiency should one expect, given a hot summers day - if we get any?

Thanks for your advice. Jeff.

If you want a technical answer, the data sheet for the photovoltaic laminate series has some temperature coefficients for the different parameters, so you should be able to work out a loss of efficiency from those. See: http://www.uni-solar.com/uploadedFiles/0.1PVL-68%20AA4-3698-02.0601107.pdf, in particular the max power, which reduces by 0.21% per degree C. Note however that they say elsewhere that the temperature dependence is very non-linear, so I don't know how much reliance you can place on those figures at high temperatures. However, if a panel glued to the roof was, say, 10 degrees hotter than a ventilated framed panel, the difference in efficiency would only be 0.21 x 10, or 2.1%.

At the uni-solar web site (www.uni-solar.com) there are a few technical papers which might give you some help. Go to the home page, then select Resources > White Papers/Research reports. http://www.uni-solar.com/uploadedFiles/0.4.2_white_paper_2.pdf has a paragraph on temperature dependency for example.

If you want a practical answer, unisolar laminate panels are designed to be used in exactly your sort of situation, have a lower temperature dependence than conventional crystalline panels, and I've used unisolar panels in a very similar application myself for the last five years - on the steel roof of a narrowboat which is also insulated with foam underneath. Mine are laminate panels glued directly to the roof. I don't have any figures for the production at different temperatures, but on hot sunny days, when the roof can get too hot to touch, they are certainly kicking out a good current. I daresay there may be a little loss at high temperatures - but to be honest in any battery charging application I'd be a lot more concerned with the production at low light levels on colder days, as that is when the output is most likely to be struggling to keep up with demand.

In short, I personally wouldn't make the efficiency at high temperatures the deciding factor in deciding on the most suitable panel - the difference you notice will likely be minimal.