I wanted to post an idea about rescuing the Aral Sea, and it occurred to me that domed farming, while alleviating part of the problems of the Aral Sea, can be applied anywhere.
There are many engineering challenges, and possible disadvantages, to doming off a farm.
I propose focusing on designing a 200-acre dome unit, designed for temparate zones which experience hot summers and freezing winters, tall enough to accomodate farm machinery in the growing area. It would be a matrix of domes, and will probably need support pillars at regular intervals. These pillars could be arranged in hexagonal form, and have sprinklers attached for irrigation.
The most important engineering issues are carbon management, water management, and temperature management and they are closely intertwined.
If we cut off the greenhouse from outside air, there will be many effects: First, the amount of atmosphereic carbon will drop, as plants suck in the carbon. Second, humidity will rise, as plants transpire, and the humidity cannot escape. Third, the temperature will rise, because heat cannot escape via convection.
We need to turn these factors into advantages.
One of the key factors will be the political climate. We must admit the obvious:
1. No farmer in America, much less Uzbekistan, can afford to dome over his fields. 2. If the domes are to be closed off from outside air, a cheap source of atmospheric carbon must be exploited.
Modern greenhouses have found that many plants grow better in elevated atmospheric carbon levels, 1000 ppm; as opposed to current atmospheric levels, at about 370ppm. The way they do this is to burn hydrocarbons in the greenhouse. In the winter, this is great for them, it heats the greenhouse, and extends the growing season. In the summer, it heats the greenhouse even further.
I believe that in order form domed farming to be viable, dome farmers must not only not have to pay for carbon, but actually be paid for sequestering the carbon. At first, the sequestration fees would help defray the costs of installation, but eventually, the carbon money can go to the farmers.
Anyway, as long as the carbon laws are favorable, the rest clicks into place.
Excess humidity should lead to condenstation on the dome ceiling. Natural heat transfer should be enough, but during certain times of the year, extra cooling might be called for. In this case, a form fitting, transparent jacket can be place on the roof and have cold water pumped through it. Because
Which brings us to another important component: resevoirs. These resevoirs would capture any rain that hits the domes. During winter, the water's heat can be extracted, so that the resevoirs provide cooling on the hottest days. To reduce moisture loss, the farm should have only one entry point, with an airlock. Perhaps thermoelectrics can be employed to gain electricity from the difference between the water temp and air temp.
The only water loss should be the water weight of the plants grown, and what little moisture escapes as people and machinery are moved in and out, whereas as an undomed field will require extra water for the transpiration losses.
Nevertheless, It will take extra time for the resevoirs to be filled at first so that the farms can take advantage of the cold winters to moderate the dome temperature in the summer. Water savings will kick in after a few years, once the resevoirs are full. During drought, the domed off areas will be mostly immune, or can even donate water from the resevoirs to aid their undomed neighbors.
If done on a large scale in a Uzbekistan, eventually this will get enough water flowing back to the Aral, while still preserving the agriculture income these countries desperately need. This would have extra advantages in the Aral Sea area because the carcinogenic dust would be blocked off from blowing onto the crops.
Some crops might not perform well under the increased humidity of a greenhouse. But surely several crops can be found that can thrive in it.
Those are the basics of the idea. Carbon sequestration, reduced water usage, longer growing seasons. Relatively expensive setup, but if it's built to last, it'll surely pay off.
There's more details to work out, but this seems to be a good start.-- Madai, Oct 12 2005 Israeli Arava Desert Greenhouse Farms http://www.hos.ufl....images/Arava-2a.jpgBuilt to withstand 150+ mph winds. Not necessarily built to withstand Palestinian repatriation. [jurist, Oct 12 2005] The Eden Project: Cornwall, England http://science.howstuffworks.com/eden.htmA slightly smaller scale project. [jurist, Oct 12 2005] Eurofresh Farms http://www.eurofres.../aboutus/tour.shtmlOver 164 acres of hothouse tomato farming near Wilcox, Arizona. Interesting and informative macromedia virtual tour. [jurist, Oct 12 2005] Air-supported structure http://en.wikipedia...supported_structure [xaviergisz, Feb 01 2013] I understand that you want to create structures large enough to operate combine harvesters inside the enclosure, but I'm not really clear how your idea is otherwise much different from the extensive greenhouse farms found in the Israeli Arava desert, the massive hothouse tomato farming operations in Arizona, or the more futuristic biodomes being made at the Eden Project in Cornwall. [links]-- jurist, Oct 12 2005 Another big difference is using the water resevoirs to control the temperature.-- Madai, Oct 12 2005 Big greenhouses, got it.-- Texticle, Oct 12 2005 I thought that the use of adjustably inflatable/deflatable translucent ETFE foil pillows to aid control of passive heating and cooling at the Eden Project biodomes was an interesting innovation.-- jurist, Oct 12 2005 If you “cut off the greenhouse from outside air”, you are going to have a very difficult time getting enough CO2 mixed into the air over hundreds of acres to have good crop production. Keeping it mixed will take significant numbers of fans. The other problem is the total volume necessary. A gas pipeline from some factory might work. Or large compost bins, probably fed from restaurant scraps. I have in mind an integrated farm/ranch in which the animals produce the CO2 along with compost bins. Air conditioning several hundred acres to keep fungus from taking over I have only solved for particular types of farms in certain areas. These areas are not normally used for farming however.-- cjacks, Oct 13 2005 Re: Jurist's link The Eden Project
"At this point, Eden's creators have left everything wide open". The evening and morning of the 8th day.-- dentworth, Oct 13 2005 I thought this was "Doomed Farms", but it appears to be the opposite.-- wagster, Oct 13 2005 //you are going to have a very difficult time getting enough CO2 mixed into the air over hundreds of acres to have good crop production. //
good point. four possible solutions come to mind.
We could emit the CO2 from the pillars that hold the thing up.
We could emit the CO2 in the same fashion as done in the FACE experiments.
We could design the building to be circular, and have the internal breeeze blow in a circle.
Or, we could build a fan system into the perimeter.
I think the pillars will spread the CO2 out enough. As for the CO2 source, pipelines from factories would work, I was thinking more along the lines of having it delivered in standard fountain soda CO2 tanks.-- Madai, Oct 13 2005 Not to burst your bubble Madai but I am going to have to to keep your farms from blowing up. While you have figured out how to get CO2 into the dome you haven’t got an easy way to get the O2 created by the plants out. For each volume of CO2 the farm converts to carbohydrate it produces an equal volume of O2 gas. If you just vent the excess pressure the percentage of O2 will increase until theoretically all you have left is a little bit of CO2 and a lot of O2. The plants will, thankfully, die before that happens or the farm will be subject to an explosive flash fire. I would suggest putting a cities power plant under the dome or piping the air from the farm to the plant and back if you aren’t going to use animals or something to generate your CO2. This is a bit of an over statement but it is just as important to deal with your waste streams (O2 for plants) as your resources. Make big circles.-- cjacks, Oct 13 2005 Collection of oxygen can be done many ways, and said collected oxygen will be an easily saleable commidity.
Unless they find a more efficient way, one simple way to get pure oxygen would be electrolysis of water, and collect that oxygen, and run the hydrogen through a fuel cell that uses oxygen from the open air.
You can also retrieve oxygen with lead or mercury.
Or, we can go whole hog and do fractional distallation of the air.-- Madai, Oct 13 2005 I thought the title read 'Doomed Farms'...-- finrod, Oct 20 2005 I was just about to post a similar idea to this, but found this idea, so I'll add as an anno instead.
My idea is to make a massive greenhouse covering an area of the order of 100km² with the roof 100 metres or more above the ground. By having such a huge greenhouse I figure you wouldn't need to worry so much about regulating the temperature and humidity; instead the greenhouse would form its own self-regulating (relatively temperature- stable) weather.
A glasshouse is typically constructed using a metal frame structure covered in relatively thin glass or transparent plastic. However, building such a large greenhouse in the typical manner would be too expensive.
Instead I propose making the greenhouse roof entirely from glass, i.e. without a frame. This would be done with relatively thick (e.g. 5cm) glass tiles (roughly 75cm by 75cm) assembled like an igloo. Because of the good compressive strength of glass, each dome in the dome array could have a massive diameter, e.g. 1km, thus requiring 1 (admittedly very strong) pillar per square kilometre.-- xaviergisz, Feb 01 2013 Why use glass? It's expensive, heavy, and needs supporting.
Better shirley to just make a transparent (or translucent) plastic membrane, at least 1km square. Fix the edges to the ground. At 50m intervals inside, add tethers several 10s of metres long fixed to the ground.
Very quickly, trapped heat will cause the membrane to rise as a self-supporting bubble dome. It needn't be sealed around the edges, though it might be advantageous to do so. The internal tethers are there to distribute the stress to that the membrane does not need to be expensively strong.
Small punctures will not matter. Infinitely cheaper than glass, and fairly durable.-- MaxwellBuchanan, Feb 01 2013 random, halfbakery