Self Sustaining Autonomous Greenhouse

I only have a small back garden. Even so I have often toyed with the idea of a small greenhouse but being part of a busy family I fear it would become neglected and my poor little tomatoes would suffer.

I hadn't considered automating the growing process, but seeing this project everything just clicked in my head. I can simply set it and forget it and come back periodically to ensure all is well.

I would be tempted to source the materials for the greenhouse frame locally, possibly branches from fallen trees or even use old pallets which seem to be appearing everywhere.

For the windows, how about taking some clear 2 litre fizzy drink plastic bottles, slicing them into squares of sheet and joining the sheets together with cord made from more plastic bottles?

These parts (or local alternatives) are readily available worldwide and would save a chunk of materials that may well have ended up as landfill, giving them a second chance.

We could simply stop at this stage and rely on constant manual intervention (watering, monitoring et cetera) or push on and allow the greenhouse to take care of itself.

Let's break down what we need to monitor:

• water levels
• temperature
• humidity
• soil moisture levels
• CO2 and O2 levels

If we have a permanent water source such as mains water then we don't need to monitor that but I am assuming the water is captured in a barrel or trough.

Temperature is important - too hot or cold will kill the plants.

humidity needs to be carefully balanced to ensure the plants do not rot.

Soil moisture levels must be monitored to ensure the plants do not dry out and die - most critically when the plant is in bloom or fruiting.

Carbon dioxide (CO2) is the gas that plants require to grow, in turn producing oxygen (O2) via photosynthesis ("light" "to make" as my old biology teacher drummed into me). Monitoring these gases over time will show us how our plants are getting along - as the plants grow they will reduce the CO2 in the atmosphere and replace it with O2. As CO2 is a so-called "greenhouse gas", reducing the level of CO2 is critical to our survival in the future.

Monitoring our contribution to the reduction of greenhouse gases can only be a good thing and lead us all as individuals to see the difference we each can make.

Finally, we need a reliable, repeatable way to water the plants and ensure the temperature is regulated.

Using a solar cell to charge a battery then using that free energy to pump water, monitor levels and open and close windows turns this into a self-sustaining system with minimal human involvement.

While we will still be required to top up the water occasionally if it has been a particularly dry spell, or to examine the plants themselves to ensure they don't outgrow their medium and check for pests, and finally to enjoy the fruits (or vegetables) of our labour, most of the work is done for us by nature itself, we can build one, have a break, build a second, third, fourth, knowing that in each one we are playing a small part in a global game, the game of life.