There already are membranes for separating salt from water.
Is this membrane longer-lasting? Does it require less pumping power? Does it work with seawater when other membranes do not? Is it less expensive?
Seawater can be desalinated, but there are other sources of brackish or less pure water that can be made drinkable with less expenditure of money and energy consumption.
The Navy desalinates seawater to have a supply of fresh water on its ships. It is my understanding that they use “mechanical vapor (re)compression” instead of membrane desalination (reverse osmosis). This is the heat-pump version of distillation that achieves much higher energy efficiency than simply boiling water and condensing the vapor in a single “effect.”
Multi-effect distillation saves energy by using the heat from condensing the vapor from one “effect” to boil the water at a lower pressure in the next “effect.” Vapor compression uses shaft power from an electric motor or other source to raise the pressure of the vapor, so condensing it at that higher pressure release enough heat to evaporate the water in one “effect” without adding outside heat — a heat pump or mechanical-compression air conditioner works on similar thermodynamic principles.
It is my understanding the Big Food either uses multi-effect distillation or mechanical vapor compression to remove water in making juice concentrates. Multi-effect distillation is credited to Norbert Rillieux, who applied his invention to concentrating sugar from sugar cane.
Small Food (maple syrup producers on family-owned properties) have switched from boiling sap in pans to using reverse osmosis (RO), using a pan evaporator to “finish” the syrup to give it a slight caramelization expected by consumers.
The plastic membranes used in RO save energy over boiling in a single pan, but they may be far from the thermodynamic optimum or even what can be achieved in a well-design vapor compression still because of the flow resistance of the membrane. RO, however, is much less capital cost at the scale of many maple syrup producers than vapor compression or multi-effect distillation. Maple syrup production also has a short season when the trees can be tapped, making the more capital-intensive methods less economic.
How are the new membranes an improvement?
How do they keep “crud” from spoiling the filters? Economically, that is. We are talking about a major flow of raw seawater needed.
Also, the article talks about the “ecological concerns of returning the concentrated brine to the sea”… What else were they thinking they were going to do with it — ship it to a toxic landfill?
That’s a concern with any fixed-base desalination process. The way to address might be to run tankers around so they can distribute it throughout the ocean rather than concentrate it in a single location.
They are not putting anything back into the ocean that wasn’t already in the ocean.
Maybe they could lay a pipeline to release the effluent at multiple places so it gets mixed with the bulk ocean water.
I remember in my high-school days the “Oh, the Humanity” controversy about “thermal pollution” — the cooling water discharge from the planned nuclear power plant in Zion, Illinois north of Chicago.
I remember submitting a written question to the Commonwealth Edison representatives addressing an assembly in the high-school auditorium. They read my question, “If everyone wants cooling towers, why doesn’t Commonwealth Edison just build cooling towers and add the expense to everyone’s electric bill as they are able to do under utility regulation.”
One representative remarked, “We could do that, but we don’t need to do that and we don’t need to impose that expense on our customers. Our system is that the warmed cooling water will be discharged into Lake Michigan at points along a long underwater pipe so the warm water will not be concentrated and cause algae blooms or other adverse effects. We regard it as our responsibility to protect the environment while at the same time not impose unnecessary costs on everyone using electricity.”
That response certainly influenced my thinking about corporations and social responsibility. There seem to be a large number of young people commenting on Slashdot who don’t think in those terms — the heat wave in the Pacific Northwest is all the result of the Oil Companies and the Koch Brothers and young people and their friends who will be adversely affected by future warming need to get out and vote!
The scary thing is that the Slashdot crowd is not Antifa and is not AOC — I guess they are technically oriented and educated people, either in computer systems, software architecture and coding or in computer-using STEM disciplines.
There already are membranes for separating salt from water.
Is this membrane longer-lasting? Does it require less pumping power? Does it work with seawater when other membranes do not? Is it less expensive?
Seawater can be desalinated, but there are other sources of brackish or less pure water that can be made drinkable with less expenditure of money and energy consumption.
The Navy desalinates seawater to have a supply of fresh water on its ships. It is my understanding that they use “mechanical vapor (re)compression” instead of membrane desalination (reverse osmosis). This is the heat-pump version of distillation that achieves much higher energy efficiency than simply boiling water and condensing the vapor in a single “effect.”
Multi-effect distillation saves energy by using the heat from condensing the vapor from one “effect” to boil the water at a lower pressure in the next “effect.” Vapor compression uses shaft power from an electric motor or other source to raise the pressure of the vapor, so condensing it at that higher pressure release enough heat to evaporate the water in one “effect” without adding outside heat — a heat pump or mechanical-compression air conditioner works on similar thermodynamic principles.
It is my understanding the Big Food either uses multi-effect distillation or mechanical vapor compression to remove water in making juice concentrates. Multi-effect distillation is credited to Norbert Rillieux, who applied his invention to concentrating sugar from sugar cane.
Small Food (maple syrup producers on family-owned properties) have switched from boiling sap in pans to using reverse osmosis (RO), using a pan evaporator to “finish” the syrup to give it a slight caramelization expected by consumers.
The plastic membranes used in RO save energy over boiling in a single pan, but they may be far from the thermodynamic optimum or even what can be achieved in a well-design vapor compression still because of the flow resistance of the membrane. RO, however, is much less capital cost at the scale of many maple syrup producers than vapor compression or multi-effect distillation. Maple syrup production also has a short season when the trees can be tapped, making the more capital-intensive methods less economic.
How are the new membranes an improvement?
How do they keep “crud” from spoiling the filters? Economically, that is. We are talking about a major flow of raw seawater needed.
Also, the article talks about the “ecological concerns of returning the concentrated brine to the sea”… What else were they thinking they were going to do with it — ship it to a toxic landfill?
That’s a concern with any fixed-base desalination process. The way to address might be to run tankers around so they can distribute it throughout the ocean rather than concentrate it in a single location.
They are not putting anything back into the ocean that wasn’t already in the ocean.
Maybe they could lay a pipeline to release the effluent at multiple places so it gets mixed with the bulk ocean water.
I remember in my high-school days the “Oh, the Humanity” controversy about “thermal pollution” — the cooling water discharge from the planned nuclear power plant in Zion, Illinois north of Chicago.
I remember submitting a written question to the Commonwealth Edison representatives addressing an assembly in the high-school auditorium. They read my question, “If everyone wants cooling towers, why doesn’t Commonwealth Edison just build cooling towers and add the expense to everyone’s electric bill as they are able to do under utility regulation.”
One representative remarked, “We could do that, but we don’t need to do that and we don’t need to impose that expense on our customers. Our system is that the warmed cooling water will be discharged into Lake Michigan at points along a long underwater pipe so the warm water will not be concentrated and cause algae blooms or other adverse effects. We regard it as our responsibility to protect the environment while at the same time not impose unnecessary costs on everyone using electricity.”
That response certainly influenced my thinking about corporations and social responsibility. There seem to be a large number of young people commenting on Slashdot who don’t think in those terms — the heat wave in the Pacific Northwest is all the result of the Oil Companies and the Koch Brothers and young people and their friends who will be adversely affected by future warming need to get out and vote!
The scary thing is that the Slashdot crowd is not Antifa and is not AOC — I guess they are technically oriented and educated people, either in computer systems, software architecture and coding or in computer-using STEM disciplines.