• aditya mehrotra.

initial designs for the greenhouse we were talking about [updates]

So we started playing with the CAD in how to design a greenhouse that could be used in developing nations where there is no real water source, the climate is too hot, and things like that.

These are the first initial designs we've come up with. I want to see what this wood frame on its own would cost to build at the moment.

So that's...

  • (3x) 4x8x1/2" sheets of plywood

  • (4x) 2x4x20ft pieces of wood

  • (57x) 2x4x8ft pieces of wood

That's 3.53*57+12*4+17*3 = 300.21 plus the screws... which is 30 bucks. Then the covering for the greenhouse itself (the plastics) is another 60 bucks then staples and a staple gun. so let's estimate 500 dollars for building the structure we see above with the greenhouse capabilities - that's not terrible (it's much better than the 3,000+ we'll pay for a 20ft shipping container). Now we need to add all the expensive things though and this is going to take some design. The question now becomes, how can we cheaply produce a water and a nutrient source for the greenhouse above. We'd be using the SAME techniques to build this house that we used to build the greenhouse in the backyard that's working really well.

But before we even get there - there might be problems with this design already because there's not necessarily enough space for plant roots and dirt and if the plant roots and dirt when any further down they'd reach a soil area where there are no nutrients. So maybe we'd need some extra plywood or we'd need to dig holes under the greenhouse or something to make this work... fill it with river soil I don't know. We'll get there.

Now it's time to talk about a source of NUTRIENTS and a source of WATER and CLIMATE CONTROL. These are the three things we have left to make this a successful mini farm. We want to try to make this farm self sustaining because then what we can do is allow it to work without putting stress on water sources in the locations of implementation. But first we need to make some diagrams and do some calculations. Let's see what plants developing nations typically grow.

So in Africa and India we're looking at beans, eggplant, cucumber, melons, potato, the kind of things we see in the traditional food so let's do some poking. Let's just take the example of potatoes.

So potatoes need to be planted about 30cm apart in a row and 24 inches apart within rows.

  • Potatoes use 1 to 2 inches of water per week. Water the potatoes as evenly as possible. This helps the tubers to have uniform shape and helps make a better yield. Stop watering about 2 weeks before harvest or when the vines turn yellow and naturally die after 90 to 120 days.

  • (60° to 70°F) The ideal temperature for growing potatoes is 60° to 70°F; temperatures greater than 80°F are too warm for potatoes. Grow a variety that can come to harvest in cool to mild, not hot, weather. “Early” season (early maturing) varieties require 75 to 90 cool days to reach harvest.

  • Prefers well-drained, light, deep, loose soil, high in organic matter. Unlike most vegetables,potatoesperform best in acidsoilwith pH 4.8 - 5.5.

Let's read that again. "Well-drained, deep, lose soil high in organic matter and acidic. They like acidic. Which means these could grow well in soil fertilized by urine. Also:

  • Bean, Brussels sprouts, carrot, chive, collard, corn, cucumber, garlic, kale, kohlrabi, mustard, parsley, pea, pepper, pumpkin, radish, rutabaga, squash, sunflower, tomato, turnipApple, apricot, cherry, currant, gooseberry, peach, pear, strawberry

  • According to: https://www.growveg.com/guides/soil-ph-for-organic-gardeners/ these plants also grow well in slightly acidic soil.

If our plan is to directly mix urine with the soil after disinfecting it these are the plants we should be looking at. But let's make a table of all these plans, the water they use, sunlight, temperature etc. Everything we did for potatoes.

This is a good video we want to watch just to get a feel for what one inch of water actually even means.

Or this one... and there's the answer - 1 cubic inch of water per 1x1 inch square on the garden. So we'd need to take the AREA of the plant. So I think what its saying is in a 12fx12ft square we need 1 inch height of water to water the plants. So for every square foot of plant we need roughly 1 inch tall of water height to water it.


^ Here is the link to our spreadsheet on which crops to grow and which ones to NOT. And we also made a plan as to how to install and solve the space problem in the greenhouse:


Another thing we can do to add nutrients to the soil besides peeing in it is to use compost of waste in the village. Anything that can be composted should be composted and mixed in with the soil. We need to use as much of the available nutrients as possible. Avoiding poop for sanitary reasons at the moment.

WE HAVE NOT FINISHED THE SHEET YET but just because we're seeing a trend. 1-2in of water seems pretty standard for these crops. Which means that's about 0.623377 Gallons per square foot per week to get most of these plants to grow. That's, for this greenhouse, roughly 3ftx16ft times 2 = 96 square feet, *0.62 gallons of water per week. That's like MINIMUM 60 gallons of water per week which is like 10 gallons a DAY.

So we need to build a greenhouse that can produce 60-120 gallons of water per week on its own. 

- 91-96% of urine is made of water
- We aren't sure how much a water extractor (air) can produce.
- Greenhouse can collect water that soaks down through the soil to the bottom.

So the question is, of course, water. We need to get the system to produce 60-120 gallons of water per week. Now the question is power.

Here are some maps of Africa I want to point out. Let's correlate temperature and FOOD stress which will be an interesting correlation.

So we can see there's areas near the Sahara that are high in food stress and are looking at like 30deg C of temperature on average. So that's like 80F that we need to get down to like 75F for most of the crops to. grow. Let's calculate the energy required to do that: https://theengineeringmindset.com/cooling-load-calculation-cold-room/ here's the FORMULA.

Q = U x A x (Temp out – Temp in) x 24 ÷ 1000.

  • Q= kWh/day heat load

  • U = U value of insulation (we already know this value) (W/m2.K)

  • A = surface area of walls roof and floor (we will calculate this) (m2)

  • Temp in = The air temperature inside the room (°C)

  • Temp out = The ambient external air temperature (°C)

  • 24 = Hours in a day

  • 1000 = conversion from Watts to kW.

According to the internet, for plastic, we can expect and R value of like: 0.85? Ish?

U= 1/R = 1/0.85 =~ 1.2
A1 = 8ft x 16ft x 4 --> m^2 = 47.5664  
A2 = 8ft x 8ft x 2 --> m^2 = 11.9
A = 47.6+11.9 = 59.5 m^2
Temp out = 30 C
Temp in = 23 C 

Q = 1.2*59.5*(30-23)*24/1000 = 12kWh/day

NOT accounting for anything like the efficiency of the system we're using to COOL the greenhouse or anything else...

I'm not very convinced by the calculation we'll get back to it when we can think of a better way. I want to look into greenhouse cooling systems. But it does seem most greenhouses just BLOW the hot air out of the greenhouse.

This is something to look into to cool the greenhouse while not using any electric energy or anything. GHAT or ground to air heat transfer. The system is based on the very simple principal that hot air flows from warm to cool areas. I'm not saying it'll work for out application but it very well might. Who knows. Having a large solar array and batteries might not be a problem ! We'd have to see how much the cost is and etc.

Here's a better video because this is a much simpler explanation. And initially this technology seems very promising. WE don't need to waste energy we collect and things like that. And since we're digging anyways to build this greenhouse, we can dig deeper and install a GHAT kind of system. This is a low-energy system that would allow us to pump air in and out maintaining the temperature all the time. The fan could be solar powered since it wouldn't take that much energy at all to power something like this. Then there's only one more thing we need to power. The urine disinfection. So let's talk about the plumbing system.

Here are the first initial design of the toilet/plumbing system that captures urine, stores it in a septic tank, and will pump it through a disinfector to the farm when necessary. It is possible we should switch the PUMP and disinfector and the TANK so disinfection happens before the urine is stored in the tank.

And now we add in the pump and the UV filter and the pipe that goes back into the greenhouse for irrigation.

And then we put the whole assembly together in the TOP-LEVEL CAD. Remember this is the very very first day of design, nothing has been designed and specced this is really more like a rough drawing to get an idea of the size of parts we're looking at.

And from inside the greenhouse here's where the hose-pipe comes back in to deliver the water itself.

Now here are the initial changes I'd make to the design immediately:

  • First, let's disinfect before we store - it's more sanitary and putting the pump in the first half (pressurizing before the tank) will let us use gravity to feed water to the rest of the greenhouse through a one-way valve.

  • Raise the tank up so we can use pressure of water itself to distribute the water in the greenhouse.

  • Bigger water tank? Or make the tank out of something don't buy it because buying is expensive?

The average human pees about 0.211338 Gallons per day - to generate 10 gallons per day for farming we need like 50 humans peeing in the toilets every day. The question is does this farm generate enough food for 50 humans? We don't know.

  • The farm will also need a pump to collect water that collects in the rubber/plastic netting in the bottom under the greenhouse.

  • The farm will also collect rainwater from the top of the house and gravity feed that into the tank where it is mixed with the disinfected urine.

  • Then there's a GAHT cooling and warming system for the greenhouse. Which consists of pipes underground and two fans in the greenhouse. These pipes should be PVC to avoid corrosion. And because PVC is not that expensive.

The general procedure for installing such a greenhouse is documented in the power point but I'll start with it here just to keep it all in one place.

Later would come the install of the above-ground plumbing, the solar cells, and etc. But this is what we have for now. Let's list the powered components:


  • (2x) Air blower fans for the GAHT system

  • (2x-3x) Water pumps for the irrigation system

  • (1x-2x) UV disinfectors for the irrigation system

  • All powered by solar

  • Control system for these components - we'd need a thermostat of some sort

So we'll need to figure out how to power this greenhouse using nothing but solar energy and batteries because it needs to be, essentially, completely self-sustaining. We'll need to test the theory that pee can be used as an effective fertilizer in, essentially, sand to grow crops. Otherwise the system will get a lot more complicated if we have to try mixing in poop.

This thing would need extensive, extensive testing. I wish we'd come up with this idea before the greenhouse we have got installed because maybe then we could test it (without the solar power at first).

Anyways we've developed this idea to a certain extent and I think before anything goes forward we'd need to do some verification on things like:

  • How effective is disinfected pee as a growing medium

  • How effective is GAHT at climate control

  • What kind of crops can we grow in low-quality, low-nutrient soil, acidic soil, etc

#updates #omggreenhouses

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