Chilling Hydroponic Systems
Using hydroponic chillers may be necessary when crops are grown in warmer environments, especially under intense grow lighting or in greenhouses with full sun. There is often a strong and direct relationship plant yields and crop quality share with lighting levels. Typically, for light loving plants the more they get, the more they grow–always to a point, of course. However, the trade off is that roots live in a different world; in nature the root environment is usually around ten degrees Fahrenheit cooler than the aerial portion of the plants. Add to that the fact that temperatures in the root zone are typically very stable and slow to change in natural soil settings.
In hydroponic grow rooms and set ups typically utilized for indoor farming, there is little that separates the plant roots with the aerial environment. So, roots can heat past optimal, especially under long days when there may not be enough canopy up top to adequately shade the hydroponic root zone from intense lighting (solar radiation).
For most commonly grown warm loving hydroponic crops, the upper portions of the plant thrive in a temperature range of 75 to 85 degrees Fahrenheit while the roots, as we mentioned earlier, prefer it cooler–with 65 to 72 degrees Fahrenheit being considered optimal by most growers in most situations.
Additionally, water can hold significantly more oxygen at lower temperatures–overheated nutrient solutions will have a very limited capacity to supply hydroponic crops with healthy dissolved oxygen (DO) levels.
How to Keep Cool
There are a number of methods and management techniques that can be practiced for chilling hydroponic systems.
The first place to start is managing the existing system and components to reduce nutrient solution temperatures. If that isn’t enough for your particular set up to keep temperatures optimal in the root zone, we’ll talk more in depth about actively chilling hydroponic systems (spot chillers versus closed loop chilling systems).
The sun or high intensity grow lighting sources trained on an object for prolonged periods will tend to heat it up. The mods in your RDWC system are no exception. Once plants have developed enough canopy to effectively shade the modules in your system supporting the root zone nutrient solution temperatures may be closer to optimal or easy to manage. Ramping up your light intensity accordingly is one way to help keep things cool; especially if operating HID lighting or growing under full sun.
Roots in a natural setting are protected by a large volume of soil which helps to buffer temperatures. Keeping mods directly off of warmer surfaces, like grow room floors receiving a lot of intense lighting from above, can make a difference in how much heat is absorbed. Good news for growers with newer Under Current RDWC mods is that there is a gap between the bottom of the nutrient solution in the modules and where the module is making contact with the floor–this can help a lot. UC Parkas may also be used (reflective insulative wrap) to cover mods and additionally the joints connecting mods in the system can also be wrapped with reflective insulation.
External Water & Air Pumps
Under Current and CCH2O aeroponic systems (HPAC, high pressure aeroponic cloners) are supplied with external pumps for nutrient solution circulation or misting. This helps cut down on adding heat to the nutrient solution. Air Pumps or Regenerative Blowers used for RDWC aeration are best installed outside of the grow room to reduce the amount of heat that may be added to the nutrient solution –don’t worry, air can travel long distances in tubing without any pressure loss.
Still Need More Cooling?
Doing any or all of the above will help add efficiency to your growing operation and promote healthier crops too. However, if that’s not enough to keep temperatures in the root zone at optimal you are likely going to want to install a gas charged water chiller.
There are two basic approaches for chilling hydroponic systems, and that’s Spot Chilling or Utilizing a Cold Water Loop.
If you run a single system, this is usually the way to go. Spot chilling can also be installed and applied to multiple systems–while convenient to set up, it’s not necessarily the most efficient approach for long term cost savings when operating multiple RDWC systems.
When spot chilling to keep nutrient solution temperatures optimal, a single water chiller is sized up based on system volume in gallons with consideration to what kind of temperature differential needs to be created. The chiller may run directly in line with the return or delivery end of the nutrient solution manifold, however, this may restrict flow rates. Typically, a secondary mag-drive pump pulls from the Epicenter or reservoir and it flows to and back from the gas charged water chiller or heat exchanger.
TIP: By chilling the root system, the upper portion of the plants can tolerate a little more heat, providing savings in cooling power. It’s all about thermodynamics–just like keeping your feet in a cool tub of water on a hot day helps keep your core temperature down, even if the majority of your body isn’t in the cool water.
Above: a common water chiller for spot chilling hydroponic systems.
Cold Water Loop
Definitely the ticket for chilling multiple hydroponic systems efficiently and effectively. In this method a central chiller or bank of chillers is utilized. They chill a cooling reservoir that acts as a heart to distribute chilled water to multiple cooling coils or heat exchangers in the various hydroponic systems or reservoirs within a facility. A properly sized chiller keeps the central cooling reservoir nice and chilly—a high level of insulation here is recommended for good efficiency.
A cold-water loop flows throughout the facility from the cooling reservoir toeach of the Epicenters or reservoirs in the set up. At each Epicenter, reservoir or even module there is a heat exchanger or cooling coil (stainless steel or titanium) in the system. Each cooling coil or group of cooling coils has a connection with a solenoid valve to the supply and return lines from the main cooling reservoir. If optimal temperatures are exceeded in the system, the solenoid valve opens up the flow of very cold water and circulates it through the coil(s) in the system. When optimal temperatures are reached, the solenoid shuts the cold water flow to the coil.
In this manner one central cooling reservoir can keep multiple systems at the optimal root zone temperatures without the purchase, installation and operating cost associated with having a separate chiller for each system in the facility.
Contact firstname.lastname@example.org for optimal sizing recommendations and a quotation based on your specific needs when it comes to chilling hydroponic systems.