Balcony solar power plants represent an increasingly popular solution for local energy generation in households due to their simple installation and low investment costs. However, without battery storage, significant energy surpluses occur during peak production hours, which are typically injected into the grid for free or lost due to inverter power limiting. This paper presents the design and real-world implementation of a closed-loop control system that utilizes an existing domestic electric water heater as a dynamic thermal energy storage unit. By acquiring real-time power data directly from the smart meter’s P1 port using an ESP32-C3 microcontroller, the control algorithm continuously modulates the heater’s power via a phase-angle regulator to minimize grid export. The paper analyzes the thermal model of the boiler, the linearisation of the dimmer characteristic, and evaluates the robust control strategy designed to handle grid voltage fluctuations, measurement noise, and fluctuating household loads.
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