Pros: Good low light output, good build quality, very good value for money (Watts per $)
Cons: Slightly odd voltage range means you need to use a MPPT controller for battery charging, not suitable for horizontal mounting.
After some extensive web searching I found a supplier that sold Sharp panels. I actually wanted the NT-175 monocrystalline panel but it is end-of-line and has been replaced by this, the ND-170 polycrystalline panel.
The main reason I wanted the NT one was was that it had a higher Vmp of 35 Volts and my other panels are series-parallel 17.5Vmp panels, so a 35V panel would have matched.
Anyway, the price was better on these ND panels and they are the only models that Sharp are carrying forward in the power bracket. The monocrystalline panels are now just in the 180+Wp NU panel class.
The ND-170, in common with most of Sharp's high power panels is a lower voltage than commonly seen. Most panels on the market were intended for battery charging and so have either 36 or 72 cells for charging 12V or 24V batteries. The 23.2V peak power voltage of the ND-170 panels means that you can't use one to charge a 24V battery and you waste a lot of power if you charge a 12V one.
The main application of these panels is therefore in grid-tied use with inverters running high voltage DC. These panels are capacble of being run in series up to 1000V. You can use them for battery charging if you use a Maximum Power Point Tracking (MPPT) controller to boost the current at the lower voltage. I use a Morningstar MPPT-15L to deliver up to 15A to a 12V battery.
Used in this way, the ND-170 works very well, the 12 extra cells providing extra voltage at low light to enable charging even on quite overcast days, albeit very slowly. Another feature of the odd operating voltage is that it's not so high that you can't put two panels in series and still use them with the Morningstar MPPT-15L controller, as it can accept PV strings with Voc ratings of less than 75 Volts. The ND-170 puts out a Voc of 29.3V, so two panels in series comes comfortably within the 75V limit for this controller. This then puts the panels into a good position also to charge 24V batteries via a MPPT controller when used in pairs. Perhaps this is why they are only sold in packaged pairs (the price I quoted for this review was per panel though).
Installation was a doddle. The provided instructions are clear and specific on how to mount the panels, safety and information on weight loads permissable. The only thing I noted was that the panels are not recommended for completely horizontal installation as water can sit on the glass or collect at the edge of the frame and result in "glass disease" where the minerals in the water can make the glass turn cloudy over a number of years. At least Sharp have been in the game for long enough to have gained this experience and pass it on to its customers.
The panels come pre-wired with good UV resistant 4mmsq 1m fly leads termintated in MC-3 waterproof rubber connectors. My supplier kindly donated some mating plugs and attached them to the cable I bought. With this arrangement it was a 30 second job to connect the panels in series and plug in the long cable to the controller. The only problem with MC-3 connectors is that you need two special tools to fit them - a crimp tool for the wire terminals and a weird gun thing to push the terminal into the rubber boot. The terminal blocks on the panels are possibly re-wirable but it looked like the lid was a snap-fit rather than screwed on type.
These panels are a uniform very dark blue and look quite handsome. The frames are annodised aluminium and have mounting holes in four locations plus grounding holes and drainage holes to stop water accumulating in the frame which could possibly result in freezing damage.
Shading performance has so far been quite good. As a test I set up the two panels in series on my lawn at an angle. Where they are means that in the morning the garage roof casts a strip shadow across the bottom 25% of both panels and on a clear sunny February day that resulted in an output power of about 95W (7A into 13.6V) from the MPPT controller. The other amorphous panels I have tend to cope better as their structure is that the cells are formed of strips the length of the panel rather than the Sharp's patchwork of cells. It's less likely that the whole strip of an amorphous cell will be shaded so they tend to suffer less from fully shaded cells. On the other hand, amorphous cells are about half the efficiency of the Sharp cells so they take up a lot of space for the power they generate.
It has to be said though that even at the low price that I managed to buy them for, PV panels are still an expensive business and evacuated tube solar water heater panels are cheaper and much more efficient energy harvesters for households (if your main aim is to reduce your gas bill rather than your electricity bill).
I've given these panels a quite low Eco-Score as they are a "traditional" design that uses quite a lot of energy in the making of them (being made from silicon wafers, rather than thin-film). In terms of energy pay-back time it will take a long time to break even when you consider that they can make about 111 kWh of power per year. If you could harvest and use all of that power, it would pay for the panel in 60 years in the UK weather and excluding the cost of all the other kit you need. That's for a grid-tied system without batteries. Given that the design life is 20-25 years, it's not really viable for a small installation. If you use them in an off-grid system with a big lead-acid battery bank, you will never save any money as you have to replace the batteries every 4-6 years and they are expensive and environmentally damaging (although most of the lead and plastics can be recycled into new batteries).
For non-eco-warriors who just need useful amounts of electricity where it can't be obtained from the grid, then these panels are ideal. They are also a good buy for people like me who are just into making their own electricity and denying the utility company at least some small part of their ill-gotten massive profits.