This was from Tuesday, while Freethoughtblogs was still down and I was posting on my patreon instead. I could use a bit of a cheat day for various reasons, so I’m taking advantage of the technical difficulties to use this post twice. This is very much in the vein of “sounds too good to be true, but it’s an interesting concept. A while back, I saw articles about a clever design for a desert greenhouse that used the evaporation of seawater to both maintain a cool enough temperature for crops, and to provide the water those crops needed. Now, a team at the University of South Australia has designed a floating version, that uses wicking and an evaporator to irrigate the crops:
Professor Haolan Xu and Dr Gary Owens from UniSA’s Future Industries Institute have developed the vertical floating sea farm which is made up of two chambers: an upper layer similar to a glasshouse and a lower water harvest chamber.
“The system works much like a wicking bed that household gardeners might be familiar with,” Dr Owen says.
“However, in this case, clean water is supplied by an array of solar evaporators that soak up the seawater, trap the salts in the evaporator body and, under the sun’s rays, release clean water vapour into the air which is then condensed on water belts and transferred to the upper plant growth chamber.”
In a field test, the researchers grew three common vegetable crops – broccoli, lettuce, and pak choi – on seawater surfaces without maintenance or additional clean water irrigation.
The system, which is powered only by solar light, has several advantages over other solar sea farm designs currently being trialled, according to Professor Xu.
“Other designs have installed evaporators inside the growth chamber which takes up valuable space that could otherwise be used for plant growth. Also, these systems are prone to overheating and crop death,” Professor Xu says.
Floating farms, where traditional photovoltaic panels harvest electricity to power conventional desalination units, have also been proposed but these are energy intensive and costly to maintain.
“In our design, the vertical distribution of evaporator and growth chambers decreases the device’s overall footprint, maximising the area for food production. It is fully automated, low cost, and extremely easy to operate, using only solar energy and seawater to produce clean water and grow crops.”
Dr Owens says their design is only proof-of-concept at this stage, but the next step is to scale it up, using a small array of individual devices to increase plant production. Meeting larger food supply needs will mean increasing both the size and number of devices.
I very much want to see this scaled up. When they say “fully automated”, I’m assuming that’s something of an exaggeration, since the crops will probably need at least some attention, beyond planting and harvesting, and the machinery will need maintenance, and to be cleaned of salt buildup and sea life.
In the paper itself, the authors say the field trials were done in pools with “artificial seawater”, which is great as a proof-of-concept, but it completely sidesteps the fact that sea life tends to glue itself to every possible surface. It would honestly surprise me if the water intakes didn’t start getting plugged or covered a lot faster than expected. On the plus side, the tests generated more fresh water than the plants could use, so operating at reduced efficiency may still provide enough water, especially if there’s a system for storing excess water at the beginning, and using it to supplement a shortage. If they have that, then they can also have the same sensors send out an automated maintenance request.
The other big concern, which I’m sure has occurred to you, is that the sea surface is a rather boisterous place. Even on a nice day, you get choppy water, knocking things around, and as we all know, there are days that are not nice!
The planet’s warming fast, and hot seas tend to produce big storms. I don’t know if farms like this are more vulnerable to a hurricane or typhoon than crops in coastal areas hit by those storms, but it sure seems like a problem that’ll need to be accounted for. The researchers say this is best suited for places with mild weather conditions, but I have to ask: Do such places exist, anymore?
Despite my concerns, I think this is really neat, and I feel like there’s likely to be at least some application for it, even if that consists of creating sheltered lagoons or something. In the meantime, the only way to find out what problems lie in wait for this technology, is to start using it, and seeing what it takes.