Saturday, 3 December 2011

Inverter Startup/Kickin Voltage for PV Solar Panels

Does Inverter Startup/Kick In Voltage Matter?

A number of installers throw around the startup voltage of inverters as a sales ploy and seems to be particularly prevalent with Aurora salesmen (it must be part of their training ) . A salesman from PV Solar UK used the argument when trying to sell their system to us but logic said something wasn't right if SMA Sunny Boy, the market leader didn't use that voltage.

The Aurora inverters are shipped with a default startup of 200V, which is actually higher than some other makes, but this is adjustable between 120V & 350V, other makes have adjustable startup settings too. An issue which has come to light in the past is that the saleman will push the 120V startup voltage, but when installed it'll be left at 200V .... why ? Well having too low a startup voltage causes unnecessary switch cycling, particularly in the morning, which can result in premature component failure.

Some data:

Sunrise on 5 Dec 2011 was 07:43 and sunset was 15:49.

Our Sunny Boy inverter started at 0805 producing 12W of electricity and finished at 1545 again producing 12W of electricity. So  the maximum window for increasing production was from 0743 to 0805 and from 1545 to 1549, a total of 22 minutes in the morning and 4 minutes in the evening. Realistically it will only be a few minutes either side that any meaningful electricity can be generated and at less than 12W output (125v/200V) likely to be 7.5W the difference over a year could be a maximum of 3kWh at a cost of early component failure, even the FIT payment of £1.50 isn't worthwhile.

Also when the Sunny Boy inverter starts up at 0805 it is then running for the whole day until sunset. This means that a lower kick in/startup voltage will only have any effect at sunrise and sunset not during daylight hours.

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