Originally Posted by
fietsbob
just remember the solder bridges to connect the elements together take up surface area
and generate no power.
so 100% efficient .. is as achievable as honest politics or Just-Wars.
Good point, but I'm not sure that's the answer to the 14 versus 10 watts issue. The total solar array area can capture a certain amount of solar energy, but only the active area of silicon collects energy that can produce electricity. That lost area is due to interconnects, bus bars, mechanical support, and the fact that solar cell itself contains interconnects.
I assume that by "100% efficient" you meant "maximum efficiency," since not too many solar cells are better than 20% efficient, and most are much worse.
Beyond that the major effect limiting output is the angle of incidence of solar energy, or cosine loss. There are actually a bunch more factors in the efficiency of a solar array, so many that we really don't know what the manufacturer was really talking about in 14 w advertising number and the 5v/2a cases. The V and I specs I used back when I designed PV power systems were the open-circuit voltage and the short-circuit current. And the power that they defined is not achievable in a real solar array.
Bottom line: it's complicated.
I think a bigger issue is, does the OP intend to run a dyno light? If so he needs to bypass the rectifier that is in an LED dyno light, if 5 volts is the correct internal voltage for the LEDs. If they have current limiting that typically requires additional voltage drop.