Cooling hydroponics systems in greenhouses, outdoors and growing indoors for optimal root health and plant growth becomes an important consideration during warmer months and when looking to increase cooling efficiency and climate control in CEA (Closed Environmental Agriculture) growing. There is a strong relationship between the amount of oxygen that will be available to plant roots, nutrient absorption and prospects for serious root diseases when it comes to maintaining optimal temperatures in your hydroponic reservoir and directly in the rhizospere (root zone).
This is the upper limit. If you are using bio based ingredients, for example nutrient supplements that contain organic ingredients, you are cautioned to be extra careful. Note that some nutrients will perform better than other in warm temperatures, but the bottom line is temperatures in the root zone are best maintained at a steady temperature, some where in the range of 65-72 Deg F.
You can get away with a little more in terms of slight increases in hydroponic reservoir temperatures when you keep a higher degree of sanitation in the root zone. This means low biological loads by using mineral based nutrients intended for re-circulating hydroponics. The degree of effectiveness is further improved upon with additions of supplements like UC Roots which reduce build up of sludges that can harbor and initiate problems like root diseases and limited intake of critical elements like oxygen and minerals required for good yields.
Above: UC Roots can provide more forgiving conditions for plant roots if temperatures are slightly higher than optimal for short periods in the growing cycle.
When sunlight or to some extent strong artificial light from grow lights strikes the surface of an object, it typically causes that object to heat up relatively quickly. Things like intensity, duration and shading from the plant canopy (once developed) play a role in just how warm nutrient solutions and hydroponic reservoirs may heat up-past the optimal range. By reflecting this light away, while insulating the cooler temperature inside the reservoir or hydroponic growing module or bucket growers can significantly reduce the possibility of over heating the root zone. If using an active reservoir chiller (discussed in brief below) system it will reduce how hard the system has to work and provides electrical savings.
Stainless steel (below) or titanium coils are available for cooling hydroponics systems and reservoirs. A solenoid valve with a temperature sensor equipped thermostat can open or close a steady flow of very cold water through the cooling coil placed in the system Epi Center or a central reservoir-or even in each grow module in a daisy chain. Once the temperature of the reservoir reaches the optimal set point, the flow stops via probe and thermostat control to solenoid valve. Multiple reservoirs may be linked from the same cold water supply and capture from a central cold water reservoir because the cold water never mixes with the solution in the reservoir. The stainless steel cooling coil prevents corrosion in the saline and acidic nature of hydroponics solutions.
For the best control in cooling hydroponics systems, you may require an active hydroponics water chiller in some situations. With a well designed hydroponics system you can make efficient use of a powered water chiller, that contains titanium heat exchangers that water or nutrient solutions can be pumped through to scrub away heat from the growing solution. These work great and tend to be very reliable when you follow the basic instructions included. Typically 1/4 to 1 Horse Power models are plenty for most hydroponics applications. Typically a 1/4 HP water chiller for hydroponics or aquarium use will keep it cool for 2-4K of HID lighting. Naturally using air cooled lighting is an effective way to keep temperatures from rising past optimal in your grow room or your reservoir when things start to heat up.
Erik Biksa has been writing about and discussing hydroponics growing, related technologies and cropping methods since 1999 in a variety of professional publications and platforms globally Erik has travelled the world learning and teaching modern growing techniques and technologies and is appreciated by many growers for his informative yet hands on approaches. Presently, he is the Editor at Grozine Hydroponics Mag.