Yup. Sieve implies that the only energy required is that necessary to pump the water to a level above the filter. I highly doubt that is the case. Surely you need some significant pressure differential. Even with pores the size of proteins (100x+ larger) you need pressure.
What you're describing is Reverse Osmosis - pushing salt water through a water permeable, salt impermeable membrane. It requires very large pressures, on the order of 2-30 atmospheres of pressure. The membranes used are incredibly cheap, most of the cost of RO is the pumps and maintenance. IMO innovations on the membrane are pretty marginal to the cost of RO and are usually done for hype.
In any case, they have designed it for pressure. The article describes how pressure causes water atoms to line up, train fashion, and move water much much faster than without pressure.
right, the question is -- how much pressure is required? Is it the pressure generated by a 1 cm column of water (as is implied by sieve), or is it the pressure generated by a 1000 watt high pressure pump? The difference will determine whether they have groundbreaking technology or get a participation trophy. From the article it didn't seem like there was any sort of functional prototype.
Indeed, and even if we live in a magical world where it was 100% free to run the filter, you need to manufacture the filter in the first place, and it will have to be replaced at some point, so there is ongoing energy expenditure no matter how you slice it.
