See updated version at https://brettbeeson.com.au/energy-monitoring-circuit-positives-and-negatives/
Some, it all seems pretty simple, right? It’s just import, export, consumption. This post clarifies the sign (+ or -) conventions I use which seem to make things easiest.
|Import||+ve||Energy from grid|
|Export||+ve||Energy to grid.|
|Consumption||+ve||Consumed in the building|
|Net||+ve Import and -ve Export||Power reading at meter|
|Production||+ve||Production. Can be solar, battery, wind. Note battery is just time-shifted solar or wind.|
Each of the three images has a ‘control volume’ where we measure power flow across.
CV1 is the meter: the ‘Net’ reading is positive (import) or negative (export) at any time.
CV2 simply breaks Net into positive (importing) and negative (exporting).
Import - Export = Net
C3 shows production and consumption. Note production is of any kind (e.g. solar, battery, whatever). Battery storage within the building is consider production, it’s just shifted in time.
Production - Consumption = Net
So putting this together:
Production - Export + Import - Consumption = 0