If this works out, it would be huge. It might be useful for Martian water, too.
12 thoughts on “A New Desalinization Method”
Why would we not just pay the energy penalty of flat-out distilling it? (Or, at least the slice we’re going to drink/use industrially as opposed to the slice that’s just going back into whatever hydroponics/recycling we have going.)
No matter how energy efficient your process ends up, it would seem like any actual settlement or development base would be able to -manufacture- from Martian materials an ever increasing power supply. Certainly more cheaply than shipping in more power. Yes, I know the wind won’t carry the heat off from my heat engine – but it also means a simple pit can dump more heat radiatively than would be plausible on Earth.
And a distillation-focus should be able to manufacture more capacity on site. No replacement membranes to send out. (If I’m reading between the lines correctly, they’ve basically eliminated the membrane fouling problem by making the membrane cheap enough to chuck).
The issue with evaporation-condensation systems has been the cost and low performance of the condensation system. If the water vapor is mixed with a carrier gas, the rate of condensation is limited by mass transfer through that gas. For this reason, traditional distillation systems have operated at low pressure, so the gas is just water vapor. But this means the system must withstand considerable external pressure, raising costs.
A recent invention at MIT (now being commercialized by Gradiant Corp.) gets around this by a novel condenser technology. They bubble humid carrier gas through water in a stack of bubble trays at progressively lower temperatures. The large surface area of the bubbles (and their small size) makes the condensation efficient even with the carrier gas getting in the way. Because it operates at atmospheric pressure the system can be made of cheap materials like plastics.
Pervaporation still must evaporate then condense the water, moving 2.5 MJ of heat per kilogram of water. Usually a vacuum pump is needed to remove the air that comes out of solution into the vacuum side of the apparatus, so power is needed in addition to huge amounts of low-grade heat.
Reverse osmosis has a theoretical energy requirement of 4.74 kJ/kg for 75% recovery from 3.43% seawater, and practical systems reach about 50% energy efficiency. Thus call it 10 kJ/kg of electricity vs 2500 kJ/kg of heat.
Unless a solar heated evaporator is 250x lower price than the RO system, the RO system wins.
Doug: evaporative systems will be designed to recycle much of the thermal energy, using the heat of condensation to preheat incoming salt water. Also, low grade heat is typically less expensive than electricity, per unit of energy. So it’s not quite as bad as you depict.
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
So, sticking with the 1kg of water, what would the total mass of that RO system, + mass of any replacement components for one year of continuous operation?
Small scale survival situations on Earth include stunts like “Pit, plastic sheet, cup.” And prizes for “cheap personal drinking water innovations” are quite carefully worded. Here.
How much energy does a 1m x 1m x 1m pit where the bottom is held at 373K (and where the sun is never allowed to shine directly into the pit) radiate to space? The same stunt in Antarctica radiates a fair chunk even with the atmosphere … due to the lack of water vapor.
A fair number of the chemical engineering problems seem unexplored for that particular environment.
With mars you have additional options. The ice is thermally protected by the regolith and atmo is near vacuum. Expose broken soil to atmo in container and you’ve got water vapor at little cost.
But you still have to somehow condense and collect the vapor.
Any dehumidifier does that.
No, Mr. Anthony. That is only true of any dehumidifier except for the recent Energy Star-qualified models with the new ozone-safe climate-change friendly refrigerant that must be charged to higher pressures, so it is more prone to leak out, especially on account of them being made cheaply in China according to sweetheart deals the Clintons had encouraged and rushed into production on account of government regulations under President Obama’s EPA. And you cannot get it repaired according to another set of government regulations, and you cannot dispose of it in the People Republic (of Madison, WI) without paying a special fee, I guess to discourage waste by purchasing a dehumidifier, which breaks down and then cannot be repaired as a result of government regulation.
No, THAT dehumidifier doesn’t condense any water. It just sits in your basement and acts as a space heater . . .
On Earth one gets water depending on how much water is needed and the price of water. And depends on where on Earth you are.
It seems with Mars and before human land on it, one can robotic system
which extracts enough water from the air so it limits the amount water you bring from Earth.
It seems to me that the focus of a first Mars base is to establish a landing area for supplies and place to launch from Mars in order to leave the planet- a landing and launch pad/zone.
I suggested somewhat recently that one could use frozen CO2 for the paving of a landing area.
So if processing enough air to get water, one going to a lot of CO2, which one store frozen or liquid which can be used for the paving.
It seems if need a lot of water, one needs to find regions which allow you to drill water wells. If need a moderate amount of water, one could mine water from various glacial areas on Mars [in tropics and temperate zone] if in polar regions one lots permafrost type area which not including the polar caps which plainly visible from orbit.
If you have lots of water which is polluted, it seems one get fresh water by using something like a solar pond. Roughly solar pond get a temperature of 30 C at the surface and has salt gradient which allows salty water below the surface to be 80 C. So day and night the water can maintain this below the surface temperature of 80 C and also maintain the surface temperature of at surface about 30 C.
On Mars 30 C water boils, so with Mars the surface temperature could be say 20 C or less and/or be cooled by evaporation.
Or if all you did was make a simple solar pond on Mars one could have pond surrounding by frozen ice, as the pond would stay warm at might and evaporate water which would freeze on the cold land around it, and there could be enough snow around it, that it does not all melt during the day, so grows in size. So this is just a shallow pond with a salt water which has sunlight.
So on Earth solar ponds are used to make fresh [or less salty water and to mine the salt, and provide hot water for various uses [you use heat exchange with the hot salty water under surface].
Of course I think people should live under water in Mars- which solves lack of pressure and blocks radiation and give environment lit by sunlight, which nice and can grow plants and have fishes.
I also think it’s possible that Mars has a vast amount water in crust, just as Earth would have more water in it’s crust were earth not as geological active and with it’s plate tectonic activity.
Though Earth does have a lot of water in it’s crust, and could have more than we are currently aware of [like say 25 to 50% more than current estimates].
I wonder if sucking moisture out of the air, drilling for it or trucking it in from the pole will be more economically efficient when Mars’s population hits one million.
Why would we not just pay the energy penalty of flat-out distilling it? (Or, at least the slice we’re going to drink/use industrially as opposed to the slice that’s just going back into whatever hydroponics/recycling we have going.)
No matter how energy efficient your process ends up, it would seem like any actual settlement or development base would be able to -manufacture- from Martian materials an ever increasing power supply. Certainly more cheaply than shipping in more power. Yes, I know the wind won’t carry the heat off from my heat engine – but it also means a simple pit can dump more heat radiatively than would be plausible on Earth.
And a distillation-focus should be able to manufacture more capacity on site. No replacement membranes to send out. (If I’m reading between the lines correctly, they’ve basically eliminated the membrane fouling problem by making the membrane cheap enough to chuck).
The issue with evaporation-condensation systems has been the cost and low performance of the condensation system. If the water vapor is mixed with a carrier gas, the rate of condensation is limited by mass transfer through that gas. For this reason, traditional distillation systems have operated at low pressure, so the gas is just water vapor. But this means the system must withstand considerable external pressure, raising costs.
A recent invention at MIT (now being commercialized by Gradiant Corp.) gets around this by a novel condenser technology. They bubble humid carrier gas through water in a stack of bubble trays at progressively lower temperatures. The large surface area of the bubbles (and their small size) makes the condensation efficient even with the carrier gas getting in the way. Because it operates at atmospheric pressure the system can be made of cheap materials like plastics.
Pervaporation still must evaporate then condense the water, moving 2.5 MJ of heat per kilogram of water. Usually a vacuum pump is needed to remove the air that comes out of solution into the vacuum side of the apparatus, so power is needed in addition to huge amounts of low-grade heat.
Reverse osmosis has a theoretical energy requirement of 4.74 kJ/kg for 75% recovery from 3.43% seawater, and practical systems reach about 50% energy efficiency. Thus call it 10 kJ/kg of electricity vs 2500 kJ/kg of heat.
Unless a solar heated evaporator is 250x lower price than the RO system, the RO system wins.
Doug: evaporative systems will be designed to recycle much of the thermal energy, using the heat of condensation to preheat incoming salt water. Also, low grade heat is typically less expensive than electricity, per unit of energy. So it’s not quite as bad as you depict.
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
So, sticking with the 1kg of water, what would the total mass of that RO system, + mass of any replacement components for one year of continuous operation?
Small scale survival situations on Earth include stunts like “Pit, plastic sheet, cup.” And prizes for “cheap personal drinking water innovations” are quite carefully worded. Here.
How much energy does a 1m x 1m x 1m pit where the bottom is held at 373K (and where the sun is never allowed to shine directly into the pit) radiate to space? The same stunt in Antarctica radiates a fair chunk even with the atmosphere … due to the lack of water vapor.
A fair number of the chemical engineering problems seem unexplored for that particular environment.
With mars you have additional options. The ice is thermally protected by the regolith and atmo is near vacuum. Expose broken soil to atmo in container and you’ve got water vapor at little cost.
But you still have to somehow condense and collect the vapor.
Any dehumidifier does that.
No, Mr. Anthony. That is only true of any dehumidifier except for the recent Energy Star-qualified models with the new ozone-safe climate-change friendly refrigerant that must be charged to higher pressures, so it is more prone to leak out, especially on account of them being made cheaply in China according to sweetheart deals the Clintons had encouraged and rushed into production on account of government regulations under President Obama’s EPA. And you cannot get it repaired according to another set of government regulations, and you cannot dispose of it in the People Republic (of Madison, WI) without paying a special fee, I guess to discourage waste by purchasing a dehumidifier, which breaks down and then cannot be repaired as a result of government regulation.
No, THAT dehumidifier doesn’t condense any water. It just sits in your basement and acts as a space heater . . .
On Earth one gets water depending on how much water is needed and the price of water. And depends on where on Earth you are.
It seems with Mars and before human land on it, one can robotic system
which extracts enough water from the air so it limits the amount water you bring from Earth.
It seems to me that the focus of a first Mars base is to establish a landing area for supplies and place to launch from Mars in order to leave the planet- a landing and launch pad/zone.
I suggested somewhat recently that one could use frozen CO2 for the paving of a landing area.
So if processing enough air to get water, one going to a lot of CO2, which one store frozen or liquid which can be used for the paving.
It seems if need a lot of water, one needs to find regions which allow you to drill water wells. If need a moderate amount of water, one could mine water from various glacial areas on Mars [in tropics and temperate zone] if in polar regions one lots permafrost type area which not including the polar caps which plainly visible from orbit.
If you have lots of water which is polluted, it seems one get fresh water by using something like a solar pond. Roughly solar pond get a temperature of 30 C at the surface and has salt gradient which allows salty water below the surface to be 80 C. So day and night the water can maintain this below the surface temperature of 80 C and also maintain the surface temperature of at surface about 30 C.
On Mars 30 C water boils, so with Mars the surface temperature could be say 20 C or less and/or be cooled by evaporation.
Or if all you did was make a simple solar pond on Mars one could have pond surrounding by frozen ice, as the pond would stay warm at might and evaporate water which would freeze on the cold land around it, and there could be enough snow around it, that it does not all melt during the day, so grows in size. So this is just a shallow pond with a salt water which has sunlight.
So on Earth solar ponds are used to make fresh [or less salty water and to mine the salt, and provide hot water for various uses [you use heat exchange with the hot salty water under surface].
Of course I think people should live under water in Mars- which solves lack of pressure and blocks radiation and give environment lit by sunlight, which nice and can grow plants and have fishes.
I also think it’s possible that Mars has a vast amount water in crust, just as Earth would have more water in it’s crust were earth not as geological active and with it’s plate tectonic activity.
Though Earth does have a lot of water in it’s crust, and could have more than we are currently aware of [like say 25 to 50% more than current estimates].
I wonder if sucking moisture out of the air, drilling for it or trucking it in from the pole will be more economically efficient when Mars’s population hits one million.