Seawater Greenhouse Desalination

[PlanetBoy]

Hi, I recently joined the science forums and was wondering if I could get help on my science fair project. I am trying to build a model seawater greenhouseand grow plants in it and test for various things. I do not know exactly what I would be testing for, so I was wondering if I could have some help with it.

[CaptainPanic]

You can test the effect of salt to the plants' growth?

Take 5 (or any number of) plants, and give one normal tap water, one water with a little salt, and build it up until the last plant gets normal seawater.

This is something you can do for sure... no difficult equipment needed, and only water and salt (and an idea of the composition of seawater) needed. If you have actual seawater available, you can just blend it with normal water.

 

If you do a little research, you might also find some plants that are more resistant to salt. Do this test with two types of plants to show the difference.

 

Also, you can test how much energy it takes to desalinate water. And how much it takes to only desalinate it for 50%. I admit that this is a lot more difficult than the 1st experiment.

It's a tough problem, but it is important to determine how much energy it takes to grow the plants: you need to desalinate your water, and you have artificial lights. It's quite likely that this greenhouse consumes lots of energy!

[bjelkeman]

I have worked with the inventor of the Seawater Greenhouse for a number of years, so I thought I should help clear up some questions with how it works.

 

The greenhouse does not expose the plants to salt. So whilst it is interesting to understand how salt hampers the growth of plants it really doesn't have anything to do with how plants in a Seawater Greenhouse are grown. The water used in the greenhouse is distilled from seawater by internal processes in the greenhouse and the result is that the plants get distilled water, no salt at all.

 

The distillation process uses very little energy which you have to add to the process. You need a couple of kW to drive pumps and fans for each 1000 m2 greenhouse, the evaporative cooling effect using the seawater is the equivalent to using traditional refrigeration methods of 500 kW in this scenario. So the greenhouse is very energy efficient.

 

I hope that helps.

 

Thomas, http://www.greenocean.org/

[PlanetBoy]

Thanks, I have been looked at the flowchart of the seawater greenhouse on seawatergreenhouse.com. It shows that the water vapor is transported from one end of the greenhouse to the other by fans, would it be possible to transport the water without using the fans?

[Mr Skeptic]

I looked at their greenhouse design and was very impressed. So long as you have a bunch of salt water you don't know what to do with, this seems like it would be one good option. I can't say for sure about their numbers though.

 

Yes, they say you can use regular wind instead of the fans, but of course if the wind isn't blowing you want to use the fans.

[CalvinHW]

I have worked with the inventor of the Seawater Greenhouse for a number of years, so I thought I should help clear up some questions with how it works.

 

The greenhouse does not expose the plants to salt. So whilst it is interesting to understand how salt hampers the growth of plants it really doesn't have anything to do with how plants in a Seawater Greenhouse are grown. The water used in the greenhouse is distilled from seawater by internal processes in the greenhouse and the result is that the plants get distilled water, no salt at all.

 

The distillation process uses very little energy which you have to add to the process. You need a couple of kW to drive pumps and fans for each 1000 m2 greenhouse, the evaporative cooling effect using the seawater is the equivalent to using traditional refrigeration methods of 500 kW in this scenario. So the greenhouse is very energy efficient.

 

I hope that helps.

 

Thomas, http://www.greenocean.org/

 

 

 

I am very interested in the seawater greenhouse technology, but I have only seen this being built in hot arid regions like Australia. Is it also possible to build these in cooler subtropical, coastal regions? How much sunlight and heat does this need for it to work?

 

If you could help me out that would be great, thanks in advance.

[Zolar V]

I looked at their greenhouse design and was very impressed. So long as you have a bunch of salt water you don't know what to do with, this seems like it would be one good option. I can't say for sure about their numbers though.

 

Yes, they say you can use regular wind instead of the fans, but of course if the wind isn't blowing you want to use the fans.

It would be very interesting if you could somehow harness the power of natural pressure to create wind.