Saturday 10 March 2018

Solar heat, update.

Some points I noticed while my solar heat system was installed last spring.

The glass cracked in couple of days, most likely the window frame was too tight. It was probably loose enough for normal use but in my use it heated to over 50 degrees and I'm guessing that was too much. Next time I'll make a new frame and make sure the glass is really loose in there.

I'm measuring the small solar panel wrong, I should be measuring amps and not voltage. Needs to be fixed sometime in the future.

ESP8266 real time clock is very inaccurate. I fixed this by ignoring the time sent and using the receiving servers time.

There's not enough error handling in my code and sometimes it crashes, most likely it's in the MQTT or NTP part, network trouble probably.

Using just convection didn't give that much heat so I added a fan. Currently it starts the fan when heated temperature is 20 degrees above inside temperature, when heated temperature is less than 10 degrees above room temperature then fan speed is decreased.

I used a standard 120 mm computer case fan I had lying around. "Case" for the fan was fabricobbeled from plastic cellular board I had salvaged from trash.


Here's an example of a sunny day, blue is outside temp (north side of the house), red is bottom of the collector, yellow is heated air and green is inside of our garage. Magenta is the "speed" of the fan, it's actually 10 bit pwm value of the ESP8266, as the fan doesn't have a pin for measuring speed, but it gives some idea on how fast the fan is running.

Updated source and Fritzing scheman can be found on github. https://github.com/mika-koivusaari/solar_air_heat_controller

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