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Creating a windowfarm

Mar 21, 2011
Not too long ago I came across this site: It is a great project which immediately piqued my interest - I enjoy building things, virtual and real, and growing up in the countryside instilled a love for plants and living things. I have a little nooked corner window behind my desk which would be a perfect spot for a dozen plants and less green around the place than I would like meant I soon found myself with a new project. Of course I tend to regard build plans as little more than hints and decided on my own design inspired by several of them.

Since I prefer as little clutter as possible I soon decided to use a single pipe to send water up, collect it in a reservoir and from there let it siphon down past the plants. I estimated a 40mm PVC tube would be perfect as upper reservoir:

For this I used a 1 meter pipe, cut into two pieces of 40cm and 60cm connected by a bend. Little metal hooks (about €1,50 a pack) are screwed into predrilled holes:

The next step was to obtain plantholders and cups for the clay pellets and plants themselfs. The windowfarms project advices the use of specific bottles which I promptly ignored. The most common bottle encountered in our home were 1.5L coca-cola bottles which seemed just fine for the job. Their inner diameter is about 10cm, so I obtained plantholders with a diameter slightly larger than that and removed the upper ring with a small metal-saw:

This is actually an almost perfect fit after adjustment and looks very promising. Note the holes at the top of the bottle used to add suspension wires and the larger hole for the plant itself.

My next move was to test and build a pump system which would push the water from the bottom reservoir back up to the top reservoir. Initially I planned to use a normal water pump for this: I had one laying around anyway and it seemed much more efficient than the air-pump designs posted. Although this worked great for my initial test (a little too great almost, the bottom reservoir was depleted in a matter of seconds thanks to a 400l/h pump) later tests showed the fatal mistake in my plan: the pump only had a 60cm lift capacity. And as expected, over the roughly 1.5m I needed the water to rise it could not produce a single drop.

At this point I went to a pet shop to get a new pump: either a stronger water pump or an air pump to try the adviced lifting method. Much to my surprise the cheapest water pump capable of lifting high enough costed about €75,-, so I went with the €10,- air pump instead:

It is a little 3 Watt Sera Air 110 Plus pump which produces very little noise. It only has a single outlet, but as said, that was all I needed. Next I needed to test it, and for this I procured a simple reservoir. For you dutch guys out there: it's an empty container for Jodekoeken biscuits. To prevent backflow I installed the one-way-valve provided with the pump inside the reservoir:

A piece of ducttape and a firm push prevents water from leaking out, although this is of course merely a test setup.

Sadly, an utterly failed test setup at that. From a garden center I obtained (aside from the clay pellets and cups) some 15 meters of tubing used in sprinkler installations. A short length of flexible silicon tube (left over with the water pump from old watercooling installations) was fitted over the smaller black tubing to act as water inlet but utterly failed to work. At best I got about 40cm of lift with enough water to fill about a teaspoon per minute. After much trial and error I realised there were two problems with my approach:

1. The inner tube should fit inside the smaller black tubing used for the rest of the circuit.
2. Gaining enough water pressure would be instrumental in obtaining the desired lift.

The first problem required some creative thinking. Initially I attempted to find one of this little metal spikes used for ballpumps, like these. No sports store nearby could be found to have them and as usual I was impatient, so I decided to canabalize a simple ballpoint pen. The ink container was the perfect size for my purposes and I did not actually need another one-way-valve anyway. Finding an empty pen and blowing out the remaining inkt was fairly easy, after which I tried to solve the second problem.

This I realised required a larger reservoir than my cookie jar. Seeing how there were a couple of cola bottles lying around already it did not take long for me to connect the dots. Drilling a small hole in the bottom and cap of the bottle was done soon enough. Next I connected the pumps valve to the outside of the cap and using a piece of tubing and some tape I connected the inktube to the inside:

And presto! It is all fairly simple (for the final version some glue or kit should be used to lock the valve and tube to the inside of the cap) but quite effective. During tests this produces more than enough water for several columns of plants, lifted for up to a meter and a half easily.

The next steps include hooking this all up to my window sill, adding more plants and connecting it all together. That however will have to wait for a future update :)

FragFrog out!

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