Consumerbot3418
Fitting square pegs into round holes... for fun?
I presume that many of us that are off-grid and AC-coupled have implemented Rule 21/UL1741SA frequency shifting, to curtail PV output when production exceeds loads and battery charging capacity.
Rather than curtail production (and "waste" power), I'd prefer to make use of it! In the winter, a space heater would be one way. In summer, AC. EV charging would be another possibility.
I've recently learned that there is an affordable product on the market that is capable of switching up to 10 amps based on programmed frequency thresholds. I've managed to set it up to turn on at frequencies above 60.3, and off again when the frequency dips below 60.1, but those are arbitrary numbers I've chosen. It would be even better if I could implement a minimum duration, improving hysteresis, but this is a start!
The product in question is a Shelly 2.5, flashed over-the-air with a third party firmware called Tasmota. It's very capable--but has a bit of a learning curve! My first successful attempt to achieve the desired switching used the following rules via console:
In the attached image, you can see a chart of the telemetry provided by the Shelly over MQTT, as well as the values measured by my SMA Sunny Boy. It looks like the Shelly values are a bit noisy. Maybe the SMA values implement some sort of averaging? The telemetry can only be set to a minimum of 10 seconds, but the switching based on frequency is very responsive--works within a second or two.
When I have time, I'll try to write a more elegant rule that implements a time delay, etc. But I was excited to share this information, in case it proves useful to others!
Rather than curtail production (and "waste" power), I'd prefer to make use of it! In the winter, a space heater would be one way. In summer, AC. EV charging would be another possibility.
I've recently learned that there is an affordable product on the market that is capable of switching up to 10 amps based on programmed frequency thresholds. I've managed to set it up to turn on at frequencies above 60.3, and off again when the frequency dips below 60.1, but those are arbitrary numbers I've chosen. It would be even better if I could implement a minimum duration, improving hysteresis, but this is a start!
The product in question is a Shelly 2.5, flashed over-the-air with a third party firmware called Tasmota. It's very capable--but has a bit of a learning curve! My first successful attempt to achieve the desired switching used the following rules via console:
Code:
rule1 ON ENERGY#Frequency>60.3 DO Power1 ON ENDON
rule2 ON ENERGY#Frequency<60.1 DO Power1 OFF ENDONIn the attached image, you can see a chart of the telemetry provided by the Shelly over MQTT, as well as the values measured by my SMA Sunny Boy. It looks like the Shelly values are a bit noisy. Maybe the SMA values implement some sort of averaging? The telemetry can only be set to a minimum of 10 seconds, but the switching based on frequency is very responsive--works within a second or two.
When I have time, I'll try to write a more elegant rule that implements a time delay, etc. But I was excited to share this information, in case it proves useful to others!
