Happy Solstice! (In 3W time)

[joth]

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

[SteamyTea]

2 hours ago, joth said:

1700W

W or Wh?

[SteamyTea]

This is what we do down here.

 

[joth]

1 hour ago, SteamyTea said:

W or Wh?

W

[joth]

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)

 

[joth]

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  

 

[jack]

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.

[SteamyTea]

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.