Renewable energy powered membrane technology: Brackish water desalination system operated using real wind fluctuations and energy buffering

The performance of a wind-powered membrane filtration system using a brackish water reverse osmosis (BW30) module and synthetic brackish (5500 mg/L NaCl) feed water was determined. When tested with real wind speed data (average wind speed 6.1 m/s; interval of 1 s) over one day of realistic fluctuation levels, the wind-membrane system produced 0.78 m3 of water with a final concentration of 191 mg/L NaCl at an average specific energy consumption (SEC) of 7.2 kWh/m3. When a single bank of supercapacitor (SC) energy buffers were added to the system, performance increased to 0.93 m3 of permeate produced and a final concentration of 173 mg/L NaCl at average SEC of 4.2 kWh/m3. Tripling the size of the SC bank further increased productivity to 1.15 m3 (47% increase) at a final concentration 172 mg/L NaCl and average SEC of 3.1 kWh/m3 (57% reduction). The time spent within the safe operating window (SOW) per day, increased from 8 h12 m under the poorest operating conditions up to 19 h56 m with the triple SC bank. Importantly, the results indicate that steady-state system performance at an average wind speed can be used as a very good indicator of the expected performance under fluctuating wind conditions. The results described can assist with the design of autonomous, decentralised, off-grid renewable energy powered water treatment systems and help decide whether to include energy buffering components.