I am back with some encouraging results!
This is what I have done:
-I have solar panels in the roof of my house and an Arduino measure the KWh produced
-I have a swimming pool of 95 m2 and with expansion tank of 8 m2.
-I have a ESP8266 connected to an ultrasonic meter HC SR04 that:
measure the level of the expansion tank
get temp, humidity wind and solar radiation from 2 WeatherUnderground stations.
get KWh produced from home solar panels
calculate hourly ET0 with WU solar radiation and with solar radiation derived from Solar Panel
all data are recorded every 5 min. in a log file (in json format)
Results shows good agreement (in a stable weather day) between Solar panels and WU solar radiation data.
There is also a good correlation between the daily pool level change and daily ET0 values.
If anybody is interested I can provide log file printouts in Json format and additional details.
The code of this ESP8266 “Pool, Weather and ET0 logging station” will be on github soon.
Paolo