Candidate 03 / Membrane design · RO hypothesis
Match the membrane
to the flow.
Can a salt-selective permeability pattern aligned to spacer flow reduce pressure at the same accepted water output?
See the decisive testNovelty remains unresolved.
A specific difference to investigate.
A feed spacer creates regions that replenish salt water at different rates. Pulling water rapidly through a poorly flushed region can leave more salt near the membrane, increasing the pressure burden.
Put higher intrinsic water permeability in better-replenished regions and lower permeability in slow-flow regions. Keep both regions salt-selective and hold the repeating pattern in alignment with the spacer.
Measure how well each flow region replenishes the membrane surface.
Align the pattern without introducing salt leaks or extra exposed area.
The proposed benefit should depend on relative placement.
Higher permeability alone is not the idea. The test asks whether the spatial relationship matters after accounting for mean material properties, salt passage and ordinary flow improvements.
Start with what already exists.
Spatially graded RO permeability is already disclosed in US8496825B1. Spacer-correlated permeability also appears in a different porous-filtration context in US20220241731A1.
The narrower proposed difference is an intrinsic, salt-selective pattern aligned with each spacer’s local mass-transfer field. Combining known permeability grading with known flow mapping carries substantial prior-art risk. No enabling manufacturing feature or unexpected measured effect has established originality.
This is the most concrete hardware hypothesis retained from the project’s invention search. That makes it a useful test candidate; it does not establish a new separation principle, patentability or clearance to operate.
Make the comparison decisive.
Use a qualified flat-sheet RO cell and independently prepared specimens. Compare the same patterned sheet in its intended position, translated at fixed orientation, and at intermediate offsets. Rotation that changes the flow field is not a clean alignment control.
| Comparison | Question it answers |
|---|---|
| Aligned versus shifted pattern | Does relative placement cause the effect? |
| Uniform sheet with matched mean water and salt permeability | Is the effect spatial, rather than an average material improvement? |
| Best feasible uniform sheet and conventional spacer | Does the candidate beat an optimized practical alternative? |
What the current model supports
0.033 kWh/m³
Approximate reduction in one modeled membrane-pressure-work term. The corrected synthetic batch comparison gives about 1.836 versus 1.803 kWh/m³ under its assumptions. This is not measured electricity use or a prediction of total plant savings.
The comparison uses synthetic 35 g/L NaCl feed, 50% recovery, equal area and average production rate, a collected mixed-product limit of 200 mg/L and an assumed 85% pump efficiency. Filling, flushing, recirculation, treatment, controls, cleaning and manufacture are outside that pressure-work term.
Read the model boundary and coupon-test requirements
The local two-region model uses conventional solution-diffusion transport and a salt-conserving feed film. It assumes a common ratio of salt to water permeability; this has not been demonstrated for a fabricated patterned sheet. Lateral transport, concentrated-electrolyte behavior, deformation and real manufacturing variation require further validation.
The proposed initial coupon exposes 50 × 100 mm in a qualified pressure-rated cell. Local water permeability, salt permeability, actual mass transfer, wet alignment, pressure loss and useful membrane area must be measured. These trial dimensions are not a pressure-vessel design.
Close feed, collected product, brine, sampling and retained-liquid inventories over repeated filling, production and flushing cycles. The model’s quality limit applies to the mixed batch; it does not require every instantaneous permeate sample to stay below 200 mg/L.
At the illustrative coupon circulation ratio, an extra 0.5 kPa loop loss would consume roughly the modeled pressure-work benefit. Bench motor efficiency also prevents a small-coupon wall-plug reading from becoming a plant forecast.
Know when to stop.
- Shifting the pattern does not change performance as predicted.
- The effect vanishes after matching mean permeability, salt selectivity and area.
- Swelling, assembly error, defects or ageing erase the benefit.
- Optimizing an ordinary membrane or spacer achieves the same result more cheaply.
- Extra pumping, manufacturing losses or shortened life cost more than the verified benefit.
The synthetic sensitivity analysis shows that modest improvements in conventional mass transfer or selectivity can erase the margin. Manufacturing cost and durable alignment are part of the hypothesis.
The next useful step.
The next useful step is an expert review of the specific manufacturing and alignment feature, followed by specimen and measurement qualification if the prior-art distinction survives.
This concept has no approved execution budget. It is separate from the A–H estimates. A membrane laboratory must scope fabrication, local characterization, pressure-rated testing and independent replication before a cost plan or funding request.
Discuss the membrane hypothesis