Maximum power point tracking implementation and solar tracker energization challenges in off-grid battery-less PVRO desalination plant

This paper proposes a Maximum Power Point Tracking (MPPT) algorithm for an off-grid, battery-less photovoltaic system that powers a solar desalination plant, including parallel reverse osmosis (RO) modules. The open circuit voltage and surface temperature of the PV array are first measured. Then the MP point voltage (VMP) is estimated. The PV voltage is estimated before each RO module is activated. So, the RO units are activated sequentially, before reaching the Maximum-Power-Point (MPP). A single-axis solar tracker is integrated to boost power generation capacity. The solar tracker, controlled by a calendar-based relay, does not require a radiation sensor. As the battery has no role in the steady operation of the system, it is replaced with pre-designed capacitors to handle the start-up inrush current of the tracker’s motor in the absence of a battery. A two-stage return algorithm is proposed for the solar tracker to return the panels to their initial direction without the need for a battery. So the entire system works without a battery backup. Experimental results from a 1100-watt solar system powering ten RO modules with a total demand of 860 watts demonstrate that the simultaneous implementation of the proposed MPPT and the hourly-operating solar tracker can enhance water desalination capacity by 71%.