Once the water, plants, and fish have been put in place, heat and light become crucial elements in aquaponics.
To proceed, certain assumptions must be made regarding your solar-powered aquaponics system, whether it is already in operation or being planned. These assumptions are: 1) consideration has been given to the requirements of the constant aeration pump and circulation pump, and 2) these requirements have been adjusted based on the system’s output.
Next, we will incorporate the remaining two CEA (Controlled Environment Agriculture) components into your aquaponics system by including:
- Grow lights – not expensive, easily available, and need more power than a single deep cycle battery can supply
- Heat for the fish tank – less expensive, easy to install, and, yes that second battery is necessary.
The grow lights need a converter to increase the voltage from 12vdc to either 110 or 220vac, which requires power and extra components. (Although there are 12v fluorescent lights available, they still have a lot of improvements to make in terms of effectiveness.) If you already use a converter for your water pump, ensure that you upgrade to one with sufficient watts to accommodate the total current consumption of your system.
Plants require full spectrum lighting or special growing lights in a density that is sufficient for their growth and health. We have successfully utilized the guideline of one, four-tube 4’ T8 Super-sunlight fixture for every 2m or 6’ of grow tray length. These fixtures, including bulbs, can be purchased for less than US$80 in almost every part of the world. Each fixture utilizes 4 tubes of 32 watts, meaning that a total of 128 watts of power per hour is required for up to 4 hours per day. (It is important to note that indoor growing has different time frames and costs.) To determine the power usage, the requirement is to multiply 128 watts by the number of hours of use, resulting in the watts per hour needed from your solar electrical system. At first, we tried using only one deep-cycle marine battery, but we soon discovered that a second matching battery was necessary to operate the grow lights for three hours per day during the six months of shorter days.
Assuming you already have a solar electrical system, the following are the necessary components for transitioning to solar-powered grow lights.
- A second matching battery
- An 800watt converter – 12vdc to 110 or 220vac (this is for one grow light fixture)
- One Super-sunlight T8 four-tube fixture or similar per 2m (6’) of grow tray length
- Mounting hardware for above the trellises
The price range for these will be from US$300 to US$400.
Now let’s move on to discussing the heating system.
In the majority of aquaponics systems, the fish tank is typically constructed from plastic or a durable rubberized food-grade substance. It is advised to avoid using galvanized steel, as the zinc content tends to dissolve into the water, posing harm to both fish and plants. If you opt for a fish tank made from the aforementioned materials, you may install a heating system with thermostat control for less than US$100, excluding the additional battery. Generally, most warm water freshwater fish thrive in temperatures ranging from 75 to 80° F (25 to 27° C).
To ensure the water in the fish tank stays at the desired temperature, it is important to incorporate a 12vdc heating element and a thermostat. This will offer benefits in terms of both productivity and peace of mind. In colder regions, proper insulation, particularly at the bottom and top of the fish tank, is crucial. Additionally, positioning the heating element near the aerators aids in effectively dispersing the heat throughout the tank.
Below is the list of components required to ‘go solar’ with the fish tank heater:
- 300 watt 12vdc heater element
- Thermostat/relay to control the heating element
- An adapter to mount the heating element into the side of the fish tank (may not be necessary)
Indeed, that is the comprehensive compilation of components. It is essential to acknowledge that the adaptor, which might be necessary, is a complex component comprising various parts and may necessitate minor adjustments to function appropriately in your specific circumstances.
First, drain the fish tank below the hole before mounting the heating element in it. The required components for the adaptor can be found in the plumbing section of hardware and home centers.
The thermostat is positioned near or at the top of the tank’s exterior, while the sensor is secured to the tank’s exterior, approximately halfway up its side, and protected with insulating material. Mounting the sensor on the outside of the tank at this location minimizes its contact with the water and aquatic organisms.
The wiring information is as follows: The positive (+) wiring connects the battery bank’s (+) terminal to the thermostat and continues to the heating element. The negative or neutral wire runs from the battery bank’s (-) terminal to the heating element.
If the lights and/or heating element(s) are installed, the performance of your solar electric system may or may not be sufficient. It is important to monitor its functionality closely. It is recommended to have a solar panel of at least 100 watts and an MPPT (charge controller) that can handle 20 amp loads. Upgrading either component will result in higher costs. If you have not yet bought your solar panels, it is advisable to choose panels with a minimum capacity of 100 watts or preferably over 200 watts.
Even in extreme climates, a properly constructed and insulated single fish tank system, with grow lights included, can be supported by a solar power system consisting of a 200w panel, an MPPT capable of handling 20amps, and two deep cycle batteries.
Do I Need Artificial Grow Lighting in My Farm?
Aquaponic farming offers the advantage of providing fresh produce throughout the year, even when other local growers cannot operate in the winter. This allows aquaponic farmers to be the sole supplier in a high-demand market, resulting in increased revenue for their farm. The only obstacle to efficient production during the winter is the availability of light for the plants, as long as you are in a controlled environment greenhouse.
The amount of light available to plants throughout the year can be measured by calculating the Daily Light Integral (DLI). The DLI is a measurement of the photosynthetically active photons (individual particles of light in the 400-700 nm range) from the sun that are received over a 24-hour period. This measurement is expressed as mol/m2/D (moles of light per square meter, per day). Each crop has its own specific DLI requirement for optimal production. For instance, lettuce and most leafy greens require a DLI of 17 mol/m2/D for ideal production. With a DLI of 17, lettuce only needs 4 weeks to grow. If the DLI is any lower, the production time is slowed down to 6-8 weeks. In comparison, tomatoes require a DLI of 22.
Throughout the year, the amount of sunlight we receive naturally changes with the seasons. From the summer solstice to the winter solstice, the Daily Light Integral (DLI) gradually decreases until December 21st, and then starts to increase again until June 21st. The DLI levels in different locations within the continental US vary depending on the latitude of the farm. For example, a farm in southern Colorado can maintain a DLI of at least 17 in December, while a farm in neighboring Wyoming would have a DLI below 15 during the same time. This difference in DLI can determine the success or failure of a commercial farm. Other factors that can decrease the DLI include the type of glazing on the greenhouse, weather conditions, and shading.
If you want to have production throughout the year, we can utilize artificial grow lighting to add to the amount of light needed for optimal plant production, as provided by the sun (typically a DLI of 17-20 for leafy greens). We assess the deficiency of light in your greenhouse and recommend suitable lighting systems to increase it to the necessary level for the plants. We have conducted tests to determine the light output of each fixture and the amount of light they can generate for a specific area.
The height at which the light is suspended above the plants is an important factor in determining the Daily Light Integral (DLI). For instance, if a fixture is hung 2 feet above the plants, it can supply all the necessary light for growth and cover an area of 16 ft2. However, if the same fixture is hung 3 feet above the plants, it will only provide 60% of the required light but will cover a larger area of 36 ft2. This scenario represents a supplemental lighting system where the remaining light needed is expected to be provided by the sun.
Supplemental lighting systems have different light output, cost, and power consumption levels based on the required amount of light to compensate for the sun’s deficiency during the winter. Northern farms, compared to southern farms, need more light fixtures positioned closer to the plants, with narrower lighting footprints. Consequently, lighting systems for northern farms are costlier and demand more electricity to function. Nevertheless, the income that farmers can generate in the winter often surpasses the cost of utilizing artificial lighting.
To maximize the area covered by lights and reduce the cost of a lighting system, one way is to employ light mover systems. These systems consist of a robotic track where the light is affixed to a motor, enabling it to move several feet along the track. The light moves to one end of the track, reverses to the other end, and repeats the process. By utilizing these motors, electricity consumption is minimalized, and the number of light fixtures required for farm coverage is reduced. Moreover, by adjusting the length of the track, the light’s height over the plants, and the daily operating hours, we can accurately target the Desired Daily Light Integral (DLI) to achieve plant satisfaction while avoiding unnecessary electricity waste due to excess light production.
