Domestic Solar Panels

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SeamanStaines

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I am really sorry if this has already been discussed, I just cant find the right answers. I am live aboard on a catamaran and this year we are going to fit solar panels (never had them before, big mistake!).

I have enough space to fit quite large panels so I started looking at the 'marine' units and fitting four units of about 85w each to give me 340w with a cost of nearly £1000, I already have a suitable regulator fitted which is used for my wind and water generator (a duogen).

Talking to one of my customers who fits domestic solar panels (to see if he could get me a better price) he asked why I don't simply fit two domestic panels which physically I could at 250w each and a cost of around £400.

I cant see any reason not to do this, apart from a problem I don't really understand which is to do with bypass diodes. I am being told that fundamentally the 'domestic' units wont work as if any portion of the panel is shaded the panel will cease to output. I asked the manufacturer of the 'domestic' panels and got a response that these had 3 bypass diodes, each one represents 2 rows of cells, if any cell in 2 rows is shaded then those 2 rows performance is affected. The other 2 sets of 2 rows will not be affected.

I don't know if this is either a problem, or is fundamentally different from the 'marine' derivatives which are so much more expensive.

Does anyone have any experience of this, because, from my point of view, 500w of output at £400 seems a pretty good deal?
 
Domestic panels are generally at higher voltage output than the ones sold to charge boat batteries, typically from 30 volts up to about 50 volts rather than open circuit voltage of 18 or 19 volts for battery charging panels. You would almost certainly have to cut into the circuitry of the panel to create two parallel circuits in order to charge a 12 volt system. If you have a 24 volt boat then look for domestic panels with an open circuit voltage at the lower end, and you may be OK.
 
there are load of cheap panels, there are not many real marinised panels and most have aluminium frames anyways, so i wouldn't worry about corrosion, just make sure that the glass is tempered or it will mist up, same if plastic coating , so no need to buy overpriced panels from chandlers, just makes sure the voltage is over 18 and under 22v
 
Norman_E said:
Domestic panels are generally at higher voltage output than the ones sold to charge boat batteries, typically from 30 volts up to about 50 volts rather than open circuit voltage of 18 or 19 volts for battery charging panels. You would almost certainly have to cut into the circuitry of the panel to create two parallel circuits in order to charge a 12 volt system. If you have a 24 volt boat then look for domestic panels with an open circuit voltage at the lower end, and you may be OK.
Click to expand...

I have understood from other posts that an MPPT regulator can take quite high voltages, for example panels connected in series. Is this not an option here? The savings on the panels would easily pay for one.
 
Kyocera make a whole series of panels and generally to 12 volt range-aluminium framed and sold to both the domestic market and for boat and caravan use.
Here in the UK we seem to like to be taken in by the manufactures using words like for marine use;domestic use etc.
Kyocera which has .been making these stateside for years is not obsessed with the idea that you can charge differing prices dependant on the market place.
The latest trendy thing is renewables-something I have been interested in since the 1960s.
In the domestic market we see expensive over the top high power wind gens been sold with sophisticated and expensive systems to feed into the grid.
A good renewable energy system whether land or water based should consist of an adequate means of generation;a good storage capacity;and efficient useage.
So it shouldnt be getting enough panels to run the fridge-it should be having a big enough storage capacity to supply your energy needs when demanded-you can get deep cycling batteries relatively cheap..Storage can include a 12v immersion heater on a calorifier tank to take any over production.
There is a great Oz microhydro generator-The Platypus which either sends excess power to a mains immersion heater or a pair of electric rings mounted on top of the generator!
Of course built for the outback were there is no mains grid.
Only recently I found out that isotherm fridge systems use a modified mains compressor with a built in inverter.
 
vyv_cox said:
I have understood from other posts that an MPPT regulator can take quite high voltages, for example panels connected in series. Is this not an option here? The savings on the panels would easily pay for one.
Click to expand...

That may be so but if a panel generates 250 watts at 40 volts that means that the maximum current is 6.25 amps. If you just regulate it down to battery charging voltage all you get is the 6.25 amp charge at say 14.4 volts. (i.e. a maximum of 90 watts of useable output) Effectively you are wasting over half of the panel's output.

On the domestic panel I think all the cells are in series, so if you re-wire it to produce two strings of cells in parallel you will get the full 250 watts at 20 volts to input into the regulator, giving you a maximum of 12.5 amps charging current, and a potential of 180 watts of useable output.

Both examples assume maximum panel output, most of the time you will be getting less.
 
Whats all t withhe fuss??? I got a 'domestic' (ha ha) 80w panel off ebay a few years ago works a treat, left out all year on a swinging mooring, no corrosion etc, just got another 4 40w panels to bring it up to 240w again 'domestic off ebay for the princely sum of £240, so why pay the swindleries?:D:D
 
Those 80w and 100 watt panels off e-bay are low voltage, typically about 21 volts open circuit, and 18 volts at maximum efficiency, and are designed to charge 12 volt batteries via a regulator. The panels that are sold for domestic PV power generation are typically 240 to 250 watts each and develop about 40 to 50 open circuit volts with optimum working voltage a little lower, and are not suitable for 12 volt battery charging without modification. Even if the regulator can handle the voltage without overheating, you will be wasting more than half of the potential output.
 
Do you know if it is possible to buy a MPPT regulator that would work with up to 200w of solar panels and a 913 wind generator?
Allan
 
Domestic PV panels

My domestic PV panels are 190 watt at about 40 volts no load.
So for a 12v system you would need a MPPT type regulator which "transforms" the higher voltage down to that needed for the battery. Any series or shunt type regulator as said would just waste power.
I would be reluctant to try to dismantle the panels to rearrange the series connection.
Regarding the diodes in the panel. I don't really know. The domestic panels operating in series operate on quite a high total voltage 320v in my case. With the MPPT style of regulator (inverter) it can work with a lot less voltage so if there is shadow over part of the panel diodes bypassing portions of the panel may mean usable output for longer under some shadow. I can't imagine that the diodes would be any problem on a boat. If you were feeding a 24v system directly or via a bypass or series regulator then any shadow would reduce voltage and may then stop charge. Diodes would not help in this case. good luck olewill
 
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