joth Posted December 21, 2021 Share Posted December 21, 2021 (edited) Perhaps a more geeky way of observing the shortest day: in my Loxone config I have a little formula that estimates what "Good" solar generation value would be for a given day of the year, and it's 3W off of its low point (1700W), which it should hit in the next few hours. The formula being : 1700+(1700*sin(pi*((I1-1608565080)/31557600))) where I1 is the current unix timestamp, 1608565080 is the timestamp of a previous winter solstice (2021 as it happens), and 31557600 is the number of seconds in a year (on average -- allowing for leap years). That shows the threshold at 1703.141 W so soon be at at the inflection point (in 6 hours, I think) ? And yeah, 1700W is very optimistic for December, even on an 8kW array. I last calibrated it in November and seemed about right then... Edited December 21, 2021 by joth Link to comment Share on other sites More sharing options...
SteamyTea Posted December 21, 2021 Share Posted December 21, 2021 2 hours ago, joth said: 1700W W or Wh? Link to comment Share on other sites More sharing options...
SteamyTea Posted December 21, 2021 Share Posted December 21, 2021 This is what we do down here. VID_20211221_175557525.mp4 Link to comment Share on other sites More sharing options...
joth Posted December 21, 2021 Author Share Posted December 21, 2021 1 hour ago, SteamyTea said: W or Wh? W Link to comment Share on other sites More sharing options...
joth Posted December 21, 2021 Author Share Posted December 21, 2021 Just now, joth said: W Although I compare it to the 2min average rather than instantaneous. But a time-averaged W is still measured in W. (I mean, even the "instantaneous" W is a 5sec average due to the way my energy monitor works) Link to comment Share on other sites More sharing options...
joth Posted December 22, 2021 Author Share Posted December 22, 2021 17 hours ago, joth said: The formula being : 1700+(1700*sin(pi*((I1-1608565080)/31557600))) OK so there was a clear error with this, lets call it an exercise for the reader here that went unspotted. sin(x) gives negative as well as positive result, and the input should range from 0 to 2π through the year, not from 0 to π. So the result of this expression was a threshold "good" generation power from 0W to 3400W, not 1700W to 3400W as I had intended. Doh! Second attempt gives me a threshold power 1500-3500 based on 2500 W ±1000 2500+(1000*cos(2*pi*((I1-1624242741)/31557600))) Much better. I do enjoy messing with this Loxone system Link to comment Share on other sites More sharing options...
jack Posted December 22, 2021 Share Posted December 22, 2021 10 minutes ago, joth said: I do enjoy messing with this Loxone system It's a lot of fun. Even without getting into the programming language (pico C?), it's amazing what you can do with it. Link to comment Share on other sites More sharing options...
SteamyTea Posted December 22, 2021 Share Posted December 22, 2021 13 minutes ago, joth said: sin(x) gives negative as well as positive result, You can square, then root, the result. Still not sure what you are trying to achieve here, if I am honest. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now