Ready for season 10!
A new 200-litre boiler with two coils will be used from 2022. The upper coil is already connected to the heating system and in use. The lower solar coil is connected but not yet filled with water as the temperature is still below zero at night. The boiler is raised from the ground by 60 cm because the heating system is gravity fed. Here are a couple of photos:

Real-time temperature graphs will be available here:
Outdoor temperature, collector temperature, boiler temperature.

From 2020 April 19 the collector is filled with water. We are starting the season! The graphs in real time will be here:
Outside temperature, collector temperature, boiler temperature

The longest season since 2012. Water was released from the system on October 17th.

From 2020 April 22 the collector is filled with water. We are starting the season! The graphs in real time will be here:
Outside temperature, collector temperature, boiler temperature

From April 10, 2020 the controller starts collecting data.

Testing of new controller started. Throughout the 2019 season, the collector worked with a new controller that worked very steadily. It is based on a new controller for home heating system with solid fuel boiler, storage tank, hot water boiler. Change widget settings when connected via browser from your phone or computer. The controller is now being tested pre-test software is here , wiring diagram, pcb.

September 27, 2019 was the last time the sun warmed the water. It was the best season since 2012.

April 7, 2019 solar collector filled with water, new controller connected, graphs in real time will be here:
O_2019- air temperature, K_2019- collector temperature, B_2019- boiler temperature

A new generation solar controller is being tested. The esp8266 processor (ESP-12E module) connects to the Internet wirelessly (WiFi), controlled via a web browser from a computer or mobile phone. The Beta version of the app is here. Short-term data can be stored in its internal memory and plotted. Can be connected to the most popular smart home management systems. I hope to have a working layout by the beginning of this season. Here are photos of the control interface and processor:

In 2018, the collector is filled with water and the season started on April 12th. It was sunny spring from April 1, but I still did not believe that there would be no frost.
The season ended on September 26th. There are no temperature charts, I’ve eliminated everything, and I did not get ready to sort things out. I hope next year everything will start to work properly and on time.