Energy recovery and efficiency gains
Energy recovery devices (ERDs) capture residual pressure or energy from the concentrate of pressure-driven desalination processes, notably reverse osmosis, and transfer it back to the feed stream or convert it to usable power.
Common ERD types:
- Pressure exchangers: Transfer high-pressure energy from concentrate directly to incoming seawater with high efficiency.
- Turbines and generators: Expand concentrated brine energy to drive pumps or generate electricity in some setups.
- Pelton wheels and hydraulic devices: Used in some medium-scale installations for partial recovery.
Benefits:
- Significant energy savings: ERDs can reduce the energy consumption of seawater RO by 40–60% compared with systems without recovery.
- Lower operational costs: Reduced electricity demand lowers operating expenses and PV/battery sizing needs for solar-driven RO.
- Smaller environmental footprint: Less energy use means lower lifecycle emissions and smaller infrastructure requirements.
Integration considerations:
- ERDs are most effective in pressure-driven systems at larger scales where concentrate pressures are substantial.
- They add capital cost and mechanical complexity but typically pay back through energy savings.
For solar PV-RO systems, adding ERDs lowers the required PV capacity and battery size, improving overall economic feasibility and making solar desalination more competitive.