Doctor Flamond: “You see, a year ago, I was close to perfecting the first magnetic desalinization process so revolutionary, it was capable of removing the salt from over 500 million gallons of seawater a day. Do you realize what that could mean to the starving nations of the earth?”
Nick Rivers: “Wow. They’d have enough salt to last forever! ”
Top Secret 1984
“This would be a game changer.”
You know the Greens won’t take this sitting down.
About a year ago I was thinking of running a deep pipe of California for desalination, with the osmosis at the bottom, and realized that turgor pressure has to exist across the membrane or you’d have a perpetual motion machine. If the membrane was in a pipe 1,000 meters down, the seawater inlet pressure to the pipe would be 99.4 atmospheres, which would support a freshwater column of 1,030 meters, because fresh water is less dense than salt water. So the fresh water coming out of the top of the pipe would be 30 meters above sea level. You could use it to run a turbine and then dump it back into the ocean, generating energy forever from nothing. That can’t work, so the 30 meter pressure difference has to exist across the osmotic membrane, and it would have to be a function of pressure.
An osmotic fountain of that sort *can* work, because it’s moving the salt to a greater depth. The net system energy remains constant, and the entropy does go up. If you started with a an enclosed system within a larger pipe, the fountain would only run until the bottom water became more saline, increasing the pressure needed for reverse osmosis until the flow stopped.
Things that can work, theoretically, often do not, or not very well, in practice.
Solar power can theoretically supply all our energy needs. But, the spatial coverage required is so vast that there is no practical way that it will ever fill more than a niche. Just the mundane manufacturing of enough photovoltaic material and support structure is the first virtually insurmountable hurdle. Maintaining it in working order is the next.
If it takes a plant the size of a major city to obtain a trickle of fresh water, it won’t happen. Not saying it would, but I’ve read too many pie-in-the-sky revolutionary claims which never came to fruition to be significantly motivated to even bother reading the article. Based on that experience, I strongly suspect the hurdles are daunting, but largely downplayed. It’s a recurring pattern, and life is short, and getting shorter all the time.
I’m afraid that that their claim “The energy that’s required and the pressure that’s required to filter salt is approximately 100 times less.” is complete and utter horseshit. Current technology has reached 50% of ideal efficiency, and it’s immaterial how thin the membrane is, what matters is the osmotic pressure losses. The best improvement physically possible is only a factor of two.
I have always had an issue with saying something was “100 times less” instead of “1 percent of”.
Doctor Flamond: “You see, a year ago, I was close to perfecting the first magnetic desalinization process so revolutionary, it was capable of removing the salt from over 500 million gallons of seawater a day. Do you realize what that could mean to the starving nations of the earth?”
Nick Rivers: “Wow. They’d have enough salt to last forever! ”
Top Secret 1984
“This would be a game changer.”
You know the Greens won’t take this sitting down.
About a year ago I was thinking of running a deep pipe of California for desalination, with the osmosis at the bottom, and realized that turgor pressure has to exist across the membrane or you’d have a perpetual motion machine. If the membrane was in a pipe 1,000 meters down, the seawater inlet pressure to the pipe would be 99.4 atmospheres, which would support a freshwater column of 1,030 meters, because fresh water is less dense than salt water. So the fresh water coming out of the top of the pipe would be 30 meters above sea level. You could use it to run a turbine and then dump it back into the ocean, generating energy forever from nothing. That can’t work, so the 30 meter pressure difference has to exist across the osmotic membrane, and it would have to be a function of pressure.
An osmotic fountain of that sort *can* work, because it’s moving the salt to a greater depth. The net system energy remains constant, and the entropy does go up. If you started with a an enclosed system within a larger pipe, the fountain would only run until the bottom water became more saline, increasing the pressure needed for reverse osmosis until the flow stopped.
Things that can work, theoretically, often do not, or not very well, in practice.
Solar power can theoretically supply all our energy needs. But, the spatial coverage required is so vast that there is no practical way that it will ever fill more than a niche. Just the mundane manufacturing of enough photovoltaic material and support structure is the first virtually insurmountable hurdle. Maintaining it in working order is the next.
If it takes a plant the size of a major city to obtain a trickle of fresh water, it won’t happen. Not saying it would, but I’ve read too many pie-in-the-sky revolutionary claims which never came to fruition to be significantly motivated to even bother reading the article. Based on that experience, I strongly suspect the hurdles are daunting, but largely downplayed. It’s a recurring pattern, and life is short, and getting shorter all the time.
I’m afraid that that their claim “The energy that’s required and the pressure that’s required to filter salt is approximately 100 times less.” is complete and utter horseshit. Current technology has reached 50% of ideal efficiency, and it’s immaterial how thin the membrane is, what matters is the osmotic pressure losses. The best improvement physically possible is only a factor of two.
I have always had an issue with saying something was “100 times less” instead of “1 percent of”.