Forward Osmosis Technologies

Forward osmosis is a process, whereby water can be removed from saline feeds across a semi-permeable membrane by an osmotic “draw” solution, due to significant osmotic gradients between the saline feed and the draw solution. The diluted draw solution is subsequently separated from water and reused in the forward osmosis process loop.

Nrgtek Inc. has developed several new polymers, which have very intriguing properties: very high osmotic potentials, and the ability to phase separate from water either by application of heat or by inoculation of certain gases. Termed thermolytic or CO2-philic polymers, these osmotic polymers are easily regenerated for continued use, and available in industrial quantities from leading chemical manufacturers (BASF, Dow-DuPont, Clariant, Oxiteno etc).

Using these specialized polymers, Nrgtek Inc. has developed several new technologies of industrial significance.

• Waste Heat to Osmotic Power (WHOP)
  
  The high osmotic gradients of the osmotic polymers are converted to hydraulic energy, which in turn is used to drive hydro-turbines for power generation.  Waste heat or low-temperature heat (≤ 250oF) is used to regenerate the osmotic polymers.
  Nrgtek Inc. has currently engineered and fabricated a small-scale pilot plant to demonstrate the WHOP process, under a California Energy Commission subcontract. The metrics are Round-trip Efficiency (RTE) ≥ 20% for low-temperature waste heat, at a cost of ≤ $750/KW. Current technologies for similar applications (Organic Rankine Cycles) have lower RTE and significantly higher costs.

• Thermal Energy Storage in Osmotic Polymers (TESOP)
  
  These osmotic polymers can also be used for thermal energy storage, since after regeneration by application of low-temperature heat (≤ 250oF) from solar thermal, industrial heat or geothermal sources, the now-concentrated polymers can be used for power generation when needed, using high-efficiency hydro-turbines. The cost of energy storage is estimated to be around $0.075/kWh.  Currently, no technologies are available for using low-temperature heat for thermal storage to electrical power. Technology development of a 1-KW TESOP system is funded by a CalSEED subcontract.

• Electrochemically Mediated Forward Osmosis (EMFO)
  
  A new process for saline water desalination (seawater, brackish water and produced water) is currently being developed by Nrgtek Inc., at a total energy cost less than 1.25 kWh/m3 of potable water. Conventional reverse osmosis processes (with energy recovery) have an energy cost ≥ 3.00 kWh/m3 of potable water.

US patents for the above technologies include:  

• US 8,021,553

• US 9,962,656

• US 10,384,164

• US 9,782,719

• US 10,143,970