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How is this better than local rainwater collection? It works when there is no rain without needing a tank big enough to last a several year long drought. The

How is this better than local rainwater collection? It works when there is no rain without needing a tank big enough to last a several year long drought. The architecture of the greenhouse acts as a solar desalinator that in testing creates more water than is needed to irrigate the plants, so it not only grows plants, but also can provide clean water in the desert.

Zancarius 13y ago
I find it curious that on HN of all places, there are some who seem appalled that technology could be used to offset much of what we've done, largely as a fault of technological advancement. That's not to say I'm against conservation. I think conservation is a necessity that few appreciate (having lived in a desert all my life, I have a certain appreciation for scarce resources), but comments like the one you replied to are exactly the kind we don't need. That is, dismissal of alternate solutions isn't going to help the problem get any better. Out here, there's a large, untapped reservoir of brine that would be ample water to supply the neighboring communities for decades or more. The local government continues to humor bonds to build a desalinization plant every 10 years with conditions that the money will be redirected after 3 years if the plant isn't built, and unsurprisingly, the plant is never built. These greenhouses, if they work, would be a worthwhile experiment and probably substantially cheaper considering the wider variety of crops that could be grown and sold. Not to mention local growers could continue growing their crops without ruining the freshwater wells of their neighbors by running them dry. I just doubt it'll happen until the cost of pumping fresh water becomes too expensive or the wells are run completely dry.
- schiffern 13y ago
  >comments like the one you replied to are exactly the kind we don't need. GP here. :) I'm 100% in favor of using technology "to offset much of what we've done, largely as a fault of technological advancement." After all, rainwater collection is technology! But desalination isn't that kind of technology — it's the destructive kind. My question was genuine. What advantage does plastic greenhouse desalination have over rooftop rainwater harvesting? It uses less land. It costs less. It produces less pollution. No piped distribution to tear up the streets for every 50 years. No energy needed to pump water long distances. The only advantage I can see is that under desalination, someone gets to control your access to water. Advantageous for them I mean.
  - Zancarius 13y ago
    > But desalination isn't that kind of technology — it's the destructive kind. But is it really? You're effectively doing what occurs in nature. Clearing land and building a distribution infrastructure is destructive, but certainly no more than what is already going to happen regardless of whether or not desalinization is used. Pumping from salt water aquifers might qualify as well. > My question was genuine. It was, but your comment seemed dismissive of alternatives. I don't think that objectively adds anything to the conversation. I apologize if that wasn't your intent. I can see a solar desalinization system in place in areas where much of the water you encounter underground is brine or otherwise non-potable, and it's particularly useful in areas where other methods of collection won't work. Yes, it has the potential drawback of kicking the can farther down the road in terms of potentially extracting water faster than it's replaced. But that said, in much of the west, the topography lends itself well to draining much of the run off into large basins and water ingress likely far outpaces whatever could be pumped out of the ground. Perhaps a hybrid (rainfall collection + solar desalinization) would be ideal. I think you're focusing exclusively on the advertised "seawater greenhouse" and may not be aware of the benefits such a design would have in areas where there certainly is plentiful salt water, just not from a sea.
    - deleted 13y ago
      [deleted]
    - schiffern 13y ago
      >You're effectively doing what occurs in nature. Remember, the alternative I'm comparing it to is restoring the land to a forested state (specifically one with much higher food production). >draining much of the run off into large basins …from which it evaporates, leaving the salt. Not a great plan. You have to design for the desert: evaporation > rainfall. That means getting the water shaded asap. Further, run-off is not a given. It's better to design for in-place infiltration instead of run-off by remediating hardpan, imprinting, contour earthworks, etc. >water ingress likely far outpaces whatever could be pumped out of the ground The Ogallala aquifer is currently pumped 6x faster than it's being recharged, and that's not even a desert yet. http://www.upi.com/Science_News/Blog/2013/08/28/Ogallala-Aquifer-could-dry-up-in-50-years/9221377716516/ http://www.upi.com/Science_News/Blog/2013/08/28/Ogallala-Aqu...
schiffern 13y ago
> big enough to last a several year long drought You're way overestimating the size needed. Even in drought years there is substantial precipitation, but generally it happens at the wrong time of year. Often you'll have flooding in the same year as drought! See this recent example: http://news.nationalgeographic.com/news/2013/09/130913-colorado-flood-boulder-climate-change-drought-fires/ http://news.nationalgeographic.com/news/2013/09/130913-color... That flooding is made worse by hardware (meaning roofs, concrete, etc) that prevents infiltration and overwhelms surrounding areas. It's often cheaper to oversize your catchment area and direct tank overflow to a nearby garden. Generally the available roof area isn't the limiting factor, but I encourage you to verify this by looking up annual rainfall numbers for areas you're interested in. Do you know how much rain falls on your roof each year?

Zancarius 13y ago

I find it curious that on HN of all places, there are some who seem appalled that technology could be used to offset much of what we've done, largely as a fault of technological advancement. That's not to say I'm against conservation. I think conservation is a necessity that few appreciate (having lived in a desert all my life, I have a certain appreciation for scarce resources), but comments like the one you replied to are exactly the kind we don't need. That is, dismissal of alternate solutions isn't going to help the problem get any better. Out here, there's a large, untapped reservoir of brine that would be ample water to supply the neighboring communities for decades or more. The local government continues to humor bonds to build a desalinization plant every 10 years with conditions that the money will be redirected after 3 years if the plant isn't built, and unsurprisingly, the plant is never built. These greenhouses, if they work, would be a worthwhile experiment and probably substantially cheaper considering the wider variety of crops that could be grown and sold. Not to mention local growers could continue growing their crops without ruining the freshwater wells of their neighbors by running them dry. I just doubt it'll happen until the cost of pumping fresh water becomes too expensive or the wells are run completely dry.

schiffern 13y ago
>comments like the one you replied to are exactly the kind we don't need. GP here. :) I'm 100% in favor of using technology "to offset much of what we've done, largely as a fault of technological advancement." After all, rainwater collection is technology! But desalination isn't that kind of technology — it's the destructive kind. My question was genuine. What advantage does plastic greenhouse desalination have over rooftop rainwater harvesting? It uses less land. It costs less. It produces less pollution. No piped distribution to tear up the streets for every 50 years. No energy needed to pump water long distances. The only advantage I can see is that under desalination, someone gets to control your access to water. Advantageous for them I mean.
- Zancarius 13y ago
  > But desalination isn't that kind of technology — it's the destructive kind. But is it really? You're effectively doing what occurs in nature. Clearing land and building a distribution infrastructure is destructive, but certainly no more than what is already going to happen regardless of whether or not desalinization is used. Pumping from salt water aquifers might qualify as well. > My question was genuine. It was, but your comment seemed dismissive of alternatives. I don't think that objectively adds anything to the conversation. I apologize if that wasn't your intent. I can see a solar desalinization system in place in areas where much of the water you encounter underground is brine or otherwise non-potable, and it's particularly useful in areas where other methods of collection won't work. Yes, it has the potential drawback of kicking the can farther down the road in terms of potentially extracting water faster than it's replaced. But that said, in much of the west, the topography lends itself well to draining much of the run off into large basins and water ingress likely far outpaces whatever could be pumped out of the ground. Perhaps a hybrid (rainfall collection + solar desalinization) would be ideal. I think you're focusing exclusively on the advertised "seawater greenhouse" and may not be aware of the benefits such a design would have in areas where there certainly is plentiful salt water, just not from a sea.
  - deleted 13y ago
    [deleted]
  - schiffern 13y ago
    >You're effectively doing what occurs in nature. Remember, the alternative I'm comparing it to is restoring the land to a forested state (specifically one with much higher food production). >draining much of the run off into large basins …from which it evaporates, leaving the salt. Not a great plan. You have to design for the desert: evaporation > rainfall. That means getting the water shaded asap. Further, run-off is not a given. It's better to design for in-place infiltration instead of run-off by remediating hardpan, imprinting, contour earthworks, etc. >water ingress likely far outpaces whatever could be pumped out of the ground The Ogallala aquifer is currently pumped 6x faster than it's being recharged, and that's not even a desert yet. http://www.upi.com/Science_News/Blog/2013/08/28/Ogallala-Aquifer-could-dry-up-in-50-years/9221377716516/ http://www.upi.com/Science_News/Blog/2013/08/28/Ogallala-Aqu...

schiffern 13y ago

> big enough to last a several year long drought You're way overestimating the size needed. Even in drought years there is substantial precipitation, but generally it happens at the wrong time of year. Often you'll have flooding in the same year as drought! See this recent example: http://news.nationalgeographic.com/news/2013/09/130913-colorado-flood-boulder-climate-change-drought-fires/ http://news.nationalgeographic.com/news/2013/09/130913-color... That flooding is made worse by hardware (meaning roofs, concrete, etc) that prevents infiltration and overwhelms surrounding areas. It's often cheaper to oversize your catchment area and direct tank overflow to a nearby garden. Generally the available roof area isn't the limiting factor, but I encourage you to verify this by looking up annual rainfall numbers for areas you're interested in. Do you know how much rain falls on your roof each year?