New technology uses less energy to desalinate water

[Auggie]

S.F. Chronicle, 8-3-08:

A San Leandro (S.F. Bay Area) company has developed an ingenious pump that greatly reduces the energy needed to extract salt from seawater, a small but vital innovation that could help transform ocean water into something fit to drink.

<snip>

State-of-the-art desalination plants suck in seawater and then use electricity-driven pumps to put it under pressure. This salty stream is then slammed against filters designed to let the fresh water bleed through while sequestering the high-pressure brine - a process called reverse osmosis.

"It takes a lot of pressure to get the pure water to go away from the salt, and it takes a lot of energy to pressurize the water," Energy Recovery Chief Technology Officer Richard Stover said.

That's where Energy Recovery comes into play. The company designed its pump to capture the pressure trapped in that left-behind brine and recycle its energy into repressurizing the next batch of virgin seawater destined to be slammed against those reverse-osmotic filters.

LINK: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2008/08/03/BUQN122TTL.DTL

The article doesn't mention how much energy the process saves. But Wall Street apparently loves the idea. Energy Recovery went public in July 2008 at $8.50 per share closing August 1st at $11.34. Revenue has grown from $4 million in 2003 to $35.4 million in 2007.

Encouraging news!

[Thor_MN]

1. RO system designs seem bassackwards to me if you live by the ocean

Instead of pressurizing the salt water into a container, why not put the RO membranes at depth and then lower the pressure on the desalinated side? Pump the freshwater out of the system and you don't have to pump large amounts of salt water, just smaller amounts freshwater.

[DCKit]

2. They showed this thing on "Beyond Tomorrow" two or three years ago.

A kind of cartridge that captures energy from one side of the process and transfers it to the other.

I Tivo'd the episode again a few months back and, no matter how many times I watched it, I still don't get it. However, they did say it cuts the energy use for desalinization by (at least) 30%, greatly decreasing the cost of desalinization - close enough to the cost of regular water treatment to make it worthwhile.

[TheWraith]

3. Good stuff. Frankly, I'd have to think that in a lot of places it would be gravy.

Water needs are important enough that if I were running the place, I'd be willing to take the hit on energy costs to insure ample fresh water. But this is good news either way.