Smart Solar Water Heater Controller

Smart Solar Water Heater Controller is a personal IoT project developed to reduce heat loss in a domestic solar water heating system.
The project started with a simple observation: during the night, heat accumulated in the storage tank could be transferred back into the colder solar circuit. After monitoring the system and experimenting with manual valve control, I designed an ESP32-based controller that automatically operates a motorized valve according to actual system conditions.
The controller uses temperature sensors to monitor the solar circuit and the hot-water tank, as well as position feedback from the valve. It supports manual control and several automatic strategies based on time, temperature, and temperature difference (Delta T). A built-in web interface provides real-time monitoring, configuration and access to temperature history.
Particular attention was given to reliability and fail-safe operation. The controller remains autonomous if Wi-Fi or the web interface becomes unavailable, monitors valve movement and position, and uses an OPEN valve position as the safe hydraulic state in case of a control fault.
The project is currently being tested and refined using real operating data. Future development includes improved Delta-T control, temperature compensation and integration with Home Assistant for long-term monitoring and higher-level automation.