Today's yield so far
Today's yield so far
An overview of energy generated from 00:00-23:59 during: (not completely operational)
Yesterday's yield
Soladin 600 with external sensors. Black box& green wires: flash counter using an LDR. Orange wires: environment temperature. Blue wires: not yet connected. Brown wires: exhaust temp sensor. Thermometer: thermometer :-)
Energy yield of the solar panels is measured by counting the number of LED flashes per 5 minutes of a POPP electricity meter bought from EEM-Groepenkasten (see one but last item).
The meter contains an optocoupler that closes when the LED flashes. A soft-I/O pin supplies 5V to the transistor of an optocoupler that is in series with a 47 KΩ resistor to ground. The voltage across the resistor is measured by a Versatile Digital Input soft device connected to another Soft-I/O pin. When the transistor is not conducting, the VDI reads 0. As soon as optocoupler conducts, the voltage raises to 4.5V, read as '1', which triggers a counter, another soft-device in the Soft-I/O module.
Every 5 minutes a launchd triggered php script reads out the various Soft-I/O device temperatures and counters, then resets the counters to 0 and stores the values in a log file .
1600 flashes are equivalent to 1 KWh so from the number of flashes, the current power output can be calculated (W=(1000*flashes/(1600*time))).
Gemeten met Soft-I/O met LM135 temperatuur sensors
Insolation is measured by a +5V fed AMS302 sensor that is connected via a 470Ω resistor to ground. The sensor is a current source that has a linear relationship between current and lux. At least, that is the theory. It appears that roof temperature has a more linear relation with insolation than the AMS302, when it comes to a bright sunny day. The AMS302 just goes to max as early as dawn and keeps the max till dusk and really needs a neutral grey filter to reduce its sensitivity.
Temperature measurements in the sun (thin purple line) and in contact with underside of solar panel (thick purple line). It is clear that on a sunny day, the solar panels prevent the house from heating up (the roof surface is 30°C (86 °F), not 50°C (122 °F) on a hot summer day).
Yield estimation by counting pulses of the Soladin LEDs is also an option. Compare true output with Soladin Counts. Eventually, the data will be live updated in a log file which is collected by the Sonnenertrag.eu site. These graphs were generated by Sonnenertrag.eu.
Crude source code example in php to compose solarlog files for Sonnenertrag.
Left: three soladins (the right one has been replaced recently) Right: three KWh counters with S0 pulse counter