In Aquaponics the plants have a constant supply of water and nutrients. Therefore, growing food in Aquaponics can produce a huge quantity of vegetables but some environmental factors have a massive impact on the crop production. Indeed plants need water and nutrients to grow but they also need light and an appropriate temperature. Growing your food in a greenhouse aquaponics can have many advantages.
A Competition for light
Generally speaking there is a natural competition for light between the plants in a garden. The plants are growing in high trying to catch the most sunlight possible while the small or younger plants remain in the shade. The growth is therefore limited by the quantity of light available to the plants. In a Greenhouse the sunrays are going through a plastic (polycarbonate…) or glass wall that often diffuse the sunrays in a more diffuse light, making it more available to all plants height and limiting the high competition. The small plants will therefore grow much better and the general shape of the plants will be stronger and more productive. This is a significant advantage of the greenhouse aquaponics system.
An improved temperature profile
Temperature is often the limiting factor in aquaponics. Plants and fish metabolism is directly dependant of the temperature of their environment which means that when the temperature is in the lower end of their thermal preferendum, the growth will decrease. On the other side when the temperature is at the optimum, their growth will increase significantly and the general production of the aquaponics system will increase. A Greenhouse is the perfect way to keep the air and the water temperature high and therefore to boost the production of the system.
How a greenhouse increase the temperature of the system
Generally speaking everybody has heard of the greenhouse effect. Basically when the sun ray penetrate through the greenhouse it is absorbed and the heat remain in this “closed” environment. This phenomenon allows the greenhouse to keep the air at a significantly high temperature compared to the outdoor temperature.
Watch out for the big heat!
If the greenhouse effect is an advantage when we want to raise the temperature be careful as it can also be a treat in summer. If the temperature outdoor is already high, the temperature inside a classic greenhouse can very quickly increase and reach 50+oC which would be a disaster for both the fish and the vegetables
The classic ways to regulate the greenhouse temperature
A number of possibilities are available in order to keep your greenhouse temperature below the critical high limit.
The most common is to manually open some windows and doors in order to allow the air to circulate.
Some specific systems automatically open the windows and doors when the temperature reach a maximum limit.
Fans can also be placed and turned on (manually or automatically when the temperature reach the pre-set limit).
A very interesting way to keep the greenhouse temperature slightly higher in winter is to keep the chicken coop in or next to the greenhouse so the heat of the animals is kept into the greenhouse and the animals avoid to be exposed to the cold nights of winter.
Passive solar aquaponics greenhouse
Solar systems allow to heat the greenhouse and regulate the temperature without using receiving the electricity bill at the end of the month but more interesting, combining a solar system with the 2 methods detailed below will make your production completely ecofriendly!
A very interesting way of regulating the greenhouse temperature is to use the ground thermal inertia to keep the temperature cool during the day and keep it high during the night. The principle is very simple, during the day when the temperature get warm, some of the hot air is blown into pipes buried into the ground. In contact with the ground the pipes will cool down the air. At the end of this net of pipes the cooled air is coming back into the greenhouse. During the night the air inside the greenhouse is cooling down but so the cold air is blown into the pipe system buried into the ground and some warmer air comes back into the greenhouse. This clever system allows to avoid the large variations of temperature during the day and to keep the system very productive at minimal cost.
There is the possibility to connect the water of the aquaponics system to a pipes system running inside a “compost” in fermentation. The fermentation produce a natural heat that will warm up the pipes and therefore the temperature of the whole aquaponics system. This is an excellent and ecofriendly way to heat the water of the aquaponics system and therefore the whole greenhouse.
Design of the Aquaponics system into the greenhouse
The high of the greenhouse is an important point to consider if you want to grow climbing plants or large plants/trees. If you are limited in terms of height you can bury the sump tank into the ground and therefore keep your growbeds close to the ground so it leaves some height for the plants to develop in height. That said, before building the growbeds or raft tanks / Deep Water Culture (DWC) to close to the ground please think of your working/harvesting process and of the ergonomic of the task. Design your system properly in order to keep your back in good shapeJ.
When it comes to the greenhouse floor you have the option of keeping it as it is (generally earth) or adding gravels, rocks, pavement or concrete. The earth and gravels can generally let the weeds grow which is not necessary a problem. The concrete surface is net but can become slippery if your system presents some leaks of highly fertile water (algae would quickly develop).
Efficiency, material and lifetime
The efficiency of your greenhouse aquaponics system will be the sum of the different choices and material used. Polycarbonate for example is an excellent choice in order to ensure a good insulation and a perfect light diffusion. Wood is often used for the frame of the greenhouse but with the specific high moisture environment the lifetime is often limited. Galvanized still is slightly more expensive but last better in time. Geothermal setup are very expensive to put in place as they involve digging and fixing the pipes (often with concrete for a better efficiency) but will pay back in the long term. All those decisions will depend on your specific project. For commercial aquaponics don’t be afraid to invest in lasting materials and technologies.