The static image here is created from true data. Measured by Soft-I/O devices (counters).
The static image here is created from true data. Measured by Soft-I/O devices (counters).
Comparison between power estimations from the Soladin600 flash count and the "real" power output as measured by an electricity meter. For other parameters see also more data on PV panels.
Energy yield of the solar panels is measured by counting the number of flashes per 5 minutes of a LED in the front panel of a Soladin600 unit.
The Flashing Soladin LEDs illuminate a photodiode. A soft-I/O pin supplies 5V to a resistor in series with this photodiode. The other side of the photodiode is connected to the ground. The voltage across the photodiode is measured by a Versatile Voltage Input soft device connected to another Soft-I/O pin. Whenthe diode is not conducting, the VVI reads 5V. As soon as the Soladin 600 LEDs shine on the photodiode, the photodiode conducts and the voltage over the photodiode drops to about 2.5V. An alarm is then raised by a Soft-I/O soft device. The alarm acts as a trigger for a counter, yet another soft-device in the Soft-I/O module.
Every 5 minutes a launchd triggered php script reads out the various temperatures and the flash count then resets the counter to 0 and stores the values in a log file .
A rough estimate is that 80.000 flashes are equivalent to 1 KWh, the number of flashes per 5 minutes appears to approximate the current power output. In this graph, the realtion between the Soladi600 flash count and the true output can easily be seen.
The true power output is calcuated by counting the number of pulses of the electricity meter, which outputs 1600 counts per KWh. This number then is divided by 1600 and multiplied by 12, to account for the 5-minute interval, to get the watt-hour rate. The resulting unit is 'Watt' as the calculation is Wh/h.
In the current graph, a horizontal line at the level of 200 on the left y-axies would thus mean a constant output of 200 W for an hour, accounting for 0.2 KWh.
Insolation values are obtained by measuring the voltage across a 0.1Ω resistor which is shorting a small solar cell. This is a good estimator for the solar radiation energy received.
Recently this setup was replaced by an AMS daylight sensor. Unfortunately this sensor is too sensitive and its output quickly reaches the specified limit on a clear day between sunrise and sunset. Shortly, the sensor should receive a pair of 'sunglasses' (a neutral density filter) to get the values back in range of the current source, so it is again linearly related to the insolation.