Shanghai Tongjie pitches modular solar desalination for off-grid sites

Shanghai Tongjie is positioning modular seawater desalination systems as a fit for remote coastal facilities, desert outposts and island microgrids that need freshwater without grid power. The company says containerized SWRO packages, energy recovery and water storage can cut solar and battery needs while keeping membrane systems stable.

Why it matters: - Off-grid coastal communities, islands and remote industrial sites need freshwater systems that can operate without utility power. - Solar-powered seawater reverse osmosis can reduce dependence on diesel generation and battery-heavy microgrids. - Lower energy demand per cubic meter can shrink the solar footprint enough to make desalination feasible on land-constrained sites.

What happened: - Shanghai Tongjie used WATERTECH CHINA in Shanghai to highlight its modular seawater desalination systems for off-grid solar applications. - The company is presenting containerized SWRO packages as a way to pair photovoltaic power, backup generators and reverse osmosis in one system. - The release says Shanghai Tongjie provides integrated engineering support for site microgrid configurations.

The details: - Off-grid SWRO systems must match fluctuating solar output with membrane pressure and flow requirements. - The release says standard grid-tied SWRO plants run on stable power, while solar systems face cloud transients, seasonal changes and zero production at night. - The release says feedwater pressure below seawater osmotic pressure, typically 25 to 30 bar for 35,000 ppm TDS seawater, stops reverse osmosis and can foul membranes. - The preferred operating model is to produce a full day of water during the peak 6 to 8 solar hours instead of running a smaller plant around the clock. - For a community needing 100 cubic meters of water per day, the release uses a 12.5 to 16.5 m³/h modular unit as the daytime production example. - Daytime water is stored in atmospheric tanks and gravity-fed overnight. - The release says this approach keeps battery storage small and limits batteries to smoothing cloud transients and supporting controls. - Containerized SWRO modules are described as using standard electrical bus interfaces and factory-integrated power conditioning. - The systems can connect solar PV, an optional diesel or gas generator and internal SWRO motor loads through a common AC bus or centralized DC microgrid. - Energy recovery devices are presented as essential to off-grid desalination economics. - The release says reject brine leaves standard SWRO vessels at 55 to 65 bar and carries 55% to 60% of the hydraulic energy supplied by the high-pressure pump. - An isobaric pressure exchanger or hydraulic turbocharger can reduce specific energy consumption from 6.5 to 8.0 kWh/m³ to 2.8 to 3.5 kWh/m³. - The release says cutting energy use per cubic meter by half can reduce photovoltaic array size, racking and inverter capacity by 40% to 50%. - Shanghai Tongjie says it pre-integrates variable frequency drives, harmonic filters and power transfer switches inside the container to simplify field electrical work. - Variable frequency drives with soft-start logic ramp pumps up over 60 to 90 seconds to avoid inrush currents of 5 to 7 times nominal current. - If solar output falls below the operating threshold, the central PLC performs a controlled ramp-down instead of an abrupt stop. - The system then opens flush valves and uses fresh permeate from an onboard tank to flush concentrated brine from membrane housings. - The release says this helps prevent calcium sulfate and silica scaling while the system is idle overnight. - Remote systems include industrial 4G/5G or satellite IoT gateways for monitoring and service support. - The platform tracks feedwater TDS, temperature, inlet pressure, inter-stage differential pressure, permeate flow, recovery, conductivity, pump vibration, motor winding temperature and drive status. - The release says anomaly detection can trigger alerts for predictive maintenance before water production is interrupted.

Between the lines: - The pitch is less about desalination hardware alone and more about system design around variable solar power. - The emphasis on water tanks over batteries signals a cost strategy aimed at avoiding large electrochemical storage banks. - Factory integration appears aimed at reducing on-site commissioning risk in remote locations where specialized electrical work is harder to support.

What's next: - Shanghai Tongjie says project sizing depends on daily freshwater demand, seawater TDS and temperature, site latitude and longitude, available land for solar arrays and preferred backup power sources. - The company is asking customers to submit site coordinates, raw seawater analysis, daily water targets and available electrical resources for engineering calculations before procurement. - Those inputs are used to calculate load curves, membrane array configurations and containerized equipment specifications.