The 'hours total' recorded on my Sunny Boy inverter is now 8,238 hours, which means it has been receiving power from the turbine for 12 days short of a year. In that time, it has never managed to put out the 750 W which calculation said should have been possible with a flow of 3 lps. Today's post is to say the 750 W limit has finally been reached and exceeded.
A flow of 3 lps generated 748 W, - ever so close to the target output, but nevertheless falling short and leaving me hankering to see the full ¾ kW displayed on the Wattson monitor.
Today, by delivering slightly more water with just a slightly bigger nozzle on the top jet (∅ 7.46 vs 7.14 mm), the output is now 765 W. To the best of my measuring ability, the flow giving this output is 3.12 lps, - so just 4 % more than calculation predicted and possibly within the margin for error anyway.
To obtain this output from the inverter to the grid, the dc input to the inverter from the alternator is as follows:
... near enough 915 W (3 A x 305 v), - a figure qualified by these being cheap meters with limited accuracy.
915 W 'in' and 765 W 'out' means there is a power loss in the inverter of 150 W, - a surprisingly large chunk of power, making it apparently only 83% efficient at this power level.
I can't quite fathom this out for the moment, - it goes against what I have documented in previous posts (see here) that inverter efficiency gets better at higher power levels. Certainly a hand on the inverter to feel its warmth confirms that its grab of 150 W is probably correct.
Perhaps the answer lies in there being a more significant voltage drop over the transmission line at this power level, such that the voltage the inverter sees is not what's displayed on the above meter. Hmmm - I'll have to sleep on that to work out a way of checking it out.
I'll sleep more soundly though, knowing the hydro's that little bit more productive.