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Efficiency Optimization: The Main Elements of CEA Control

Harvest Integrated

08.03.21

The case for controlled environment agriculture (CEA) is getting stronger, what with the surge in weather and climate change. CEA is an attractive choice, with several benefits such as predictable crop timing, high plant quality, reduced labor costs and limited environmental impact. 

Getting these benefits, however, requires some work. You have to get several factors to work together to achieve the optimal environment. The four critical elements of CEA control that you have to balance to achieve indoor environmental control efficiency are:

  1. humidity 
  2. airflow 
  3. temperature
  4. light 

1. Humidity

No matter how advanced your grow system, the lack of proper humidity in your indoor cultivation operation will limit not only your plant growth, but the potential growth of your entire business. Humidity impacts nearly all the aspects of a grow operation and plant health. From nutrient uptake, VPD, leaf temperature, room temperature, transpiration, and photosynthesis to pathogen control, pest control, and ultimately yield. 

Put simply, a precise and consistent humidity control system is essential for staying in business. You can’t afford to have humidity that’s high or low. For example, stomata tend to close in low humidity conditions to avoid losing water. This change in stomata behavior affects photosynthesis and can stunt growth or result in growth halt. At the same time, high humidity levels can prompt fungi growth while making nutrient uptake and evaporation of water from the plants difficult. In extreme cases, high humidity levels will cause plant rot.

Controlling relative humidity and keeping the VPD within the ideal range is also crucial; it remains one of the biggest challenges with regard to attaining optimum climate control in indoor cultivation facilities. Transpiration increases as plants grow and the excess moisture must be effectively removed from the grow space. However, this poses a significant challenge for most traditional HVAC systems since the latent load can become quite high in the grow space. What’s more, late flowering phases require dew point temperatures that critically reduce the dehumidification capabilities and efficiency of many traditional HVAC systems.  

When it comes to grow room efficiency and CEA control, opting for standard, non-specialized HVAC systems may not be a great idea. After all, compromising on humidity control can substantially reduce the quality, quantity and consistency of your product and this is not an option in today’s increasingly competitive indoor agriculture landscape. 

2. Airflow

Optimal airflow distribution is critical for indoor grow room efficiency, serving various purposes that are essential for plant development and growth. For instance:

Well-mixed air distribution avoids stratification, which can result in high humidity and unequal temperatures in the grow room.

The right balance of humidity and air is critical for processes such as VPD, carbon dioxide uptake and transpiration. For example, as humidity increases, the transpiration rate falls significantly and this affects plant growth. Maintaining the ideal air distribution inside the grow room will ensure that your plants have good transpiration.

Air circulation ensures that the plants have a good supply of carbon dioxide, which is essential for plant growth.

Plants deplete all the carbon dioxide around leaves in a few minutes, creating a dead air zone around the leaves. If there’s no airflow and no gas exchange, the dead air zone stifles the plant and the air around the leaves stratifies, taking with it plant growth.

The speed of air movement plays an important role in determining the structural strength of your plants.

High airspeed can snap plant stems while constant, gentle airflow will promote healthier,  thicker and stronger stems that allow for more efficient movement of nutrients and water. Consequently, strong plants produce better buds.

Airflow is important for preventing mold, pests and disease from taking hold in your grow room.

Air movement in the grow room carries away the moisture released during transpiration. This decreases moisture levels and deters mold, pest infestation and disease.

Every grow room requires airflow that mimics the natural conditions outdoors and encourages growth. Overlooking this fact will likely result in a poor harvest, or no harvest at all. 

3. Temperature

While cannabis is resilient, it can only deal with a certain amount of temperature variation. The ideal temperature during the vegetative growth phase is usually between 68-77°F (20-25°C) and most flowering plants will do well in the range of about 65-85°F (18-29°C). Almost all cannabis plants will start suffering when the temperature goes over these ranges. Less than ideal temperature conditions affect plant metabolism and extreme temperatures for prolonged periods will considerably weaken the plants, inhibit their development and growth, and make them more susceptible to diseases. 

Maintaining temperature within the ideal range is important in a growing system, especially during the budding/flowering stage. But more important is the ability to balance temperature and relative humidity in the grow room. An HVAC system that’s too small will struggle to keep the temperature within the appropriate range whereas an oversized system can result in temperature fluctuations that change relative humidity and affect the entire grow room environment.

Without an adaptable system that can respond to dynamic temperature needs, promoting good plant development and improving the efficiency of your indoor grow operation will likely be a big challenge. 

4. Light

Light is a key driver of plant development, impacting the plants’ photosynthetic rates and anatomy. Besides photosynthesis and plant anatomy, the quality of the light source will also impact plant health and chemical content as well as yield. But not all light will get you the best results, you need the right quality. For cannabis production, light in the UV range has been shown to be most beneficial. 

The length of time cannabis is exposed to light is also important.

  • It catalyzes the cannabis plant from the vegetative growth phase to the flowering phase (cannabis is a photoperiodic plant, requiring set periods of uninterrupted light and darkness to flower)
  • It establishes a daily light integral (DLI) that induces increased flower number and biomass plus shortened growth cycles

However, grow room lights can produce a lot of heat, particularly if they are big. This increases the temperature in the grow space and has a direct effect on relative humidity. A good HVAC system must be able to offset the heat energy from the lighting and keep the air well-mixed to avoid heat build-up, thereby maintaining an optimal space temperature. 

Optimizing CEA Control for Grow Room Efficiency

Not every HVAC system will get you competitive yields and quality. In a grow environment, heating and cooling loads change fast during the shift from dark to photoperiod while the required cooling and dehumidification change as the plants grow larger. Most conventional dehumidifiers and air conditioners are not so dynamic – they can’t automatically stay attuned to the plants’ developmental process and their capabilities are normally limited when it comes to maintaining a dynamically changing environment. 

Achieving an optimal indoor grow environment requires a flexible solution that is specifically developed for the critical indoor growing environment. The solution must be accurate, with the ability to perfectly match the loads in the grow room at each stage of the grow cycle. Such a specialized system eliminates the need for costly, inefficient secondary systems that eat into your budget. 

Harvest AIR™:

  • is designed with both cooling and dehumidification to handle specialized cannabis environments
  • has variable speed compressors and a fully modulating hot gas reheat coil that precisely match the cooling and dehumidification load at every stage of the grow cycle, i.e Harvest Air maintains temperature and humidity conditions for the perfect grow
  • doesn’t rely on mass energy and brute force to cool and dehumidify, thus providing a significant increase in energy efficiency 

Grow room efficiency and CEA control go hand in hand and so having the right system can be the difference between success and failure. Get in touch with the Harvest Integrated team for a fully integrated system that will take out the work in maintaining the four elements of CEA control while reducing your overall costs and yielding a significant increase in efficiency.