6kWp system (6 south facing panels, 9 west facing panels), Growatt inverter (SPH5000) and battery (GBLI6532, 6kWh).
Collection of tools to calculate sun position, sunrise, sunset. I haven't used them yet but I found them online and I wanted to record their links. Maybe they're going to be useful when I write software to optimise power usage with Octopus Agile smart tariff.
- NOAA spreadsheets to compute sunrise and sunset time.
pvlib, a community developed toolbox that provides a set of functions and classes for simulating the performance of photovoltaic energy systems and accomplishing related tasks
- Astronomy answers walkthrough the calculations.
- Quartz Solar Forecast. See also their FOSDEM '24 talk. Open source.
- Solcast offers forecast API. Free for home usage.
The process of charging and discharging the battery has some losses (i.e. you can get fewer kWh than what has been used to charge the battery). There seems to be a few factor affecting losses:
- charge power. Every battery has its own efficiency curve but in general charging at full power isn’t the most efficient due to heating;
- discharge power. Again different batteries have different efficiency curves but discharging with little power isn’t very efficient;
- amount of time between charge and use. The higher the more self-discharge we’re going to see.
Thanks for reading. Feel free to reach out for any comment or question.