Rethinking Greenhouse Technologies

Greenhouse cultivation has gained immense worldwide popularity due to its ability to provide controlled conditions and maximize yield potential. However, without meticulous attention to climate control, they?can inadvertently become breeding grounds for harmful pathogens. Poorly designed or inadequately regulated environmental conditions can create an ideal habitat for bacteria, fungi, and other microorganisms, putting the entire crop at risk.

Greenhouses are enclosed structures used for the cultivation of plants in a controlled environment. Maintaining the ideal temperature, humidity, and light conditions are essential for the optimal growth of plants. These structures have traditionally used evaporative cooling technologies like pad & fan systems or wet walls?to control the temperature inside. In hot climates, evaporative cooling is way more practical, much cheaper and less energy intensive than HVAC, however..?traditional forms of this?technology?has?several known problems, including temperature and humidity gradients, contamination in the wet wall and its re-circulation?tanks, and therefore a greatly increased risk of microbial contamination. Lets briefly rehash?the problems associated with traditional evaporative cooling technologies and look at how new versions of the same technologies using?water chillers,?air handling units and pre-filtering of cooled?(or heated) air, can improve plant growth whilst helping to reduce?the overall microbial burden?in cannabis facilities.

Problems Associated with Traditional Evaporative Cooling Technologies:

Evaporative cooling pads or wet walls are commonly used in greenhouses to reduce the temperature inside. Wet walls consist of water-soaked pads or curtains made of materials such as cellulose pads?or fiber. As hot air is drawn through the wet wall, it is cooled by the evaporation of the water from the wet pads. However, wet walls have several known problems?and?can create temperature and humidity gradients, as the air closest to the wet wall is cooler and more humid than the air farther away. These gradients inevitably lead to greenhouse micro-climates, which in turn result in uneven microbial growth throughout the greenhouse, making it difficult to obtain accurate and consistent microbial testing results.

Contamination:

Wet walls and their re-circulation tanks have a bad reputation for?being sources of contamination?for?algae, fungi, and bacteria. These microorganisms can proliferate in the moist and warm environment of the wet wall, and can then be spread throughout the greenhouse by the circulating air. Microbial contamination can affect plant growth, as well as pose a risk to human health, particularly in cannabis facilities where cleanliness and safety are of utmost importance.

Inefficiencies

Traditional forms of evaporative cooling rely on the principle of evaporative cooling, which involves the evaporation of water to remove heat from the air. In humid climates, the air already contains a significant amount of moisture, which reduces the potential for water to evaporate. As a result, the cooling effect is diminished, and the system must work harder to achieve the desired temperature reduction.

In addition, in humid climates, traditional evaporative cooling systems can actually increase the humidity levels?within the greenhouse, leading to an uncomfortable and potentially damaging environment for plants. This is because the water used in the cooling process adds moisture to the air, and when the air is already saturated with moisture, it cannot absorb any more. This can lead to a condition known as high humidity stress?(Low VPD), which can result in reduced plant growth, susceptibility to disease and pests, and other issues.

Newer Technologies:

Newer and more precise versions of evaporative cooling technologies have been developed to address some of the problems associated with traditional wet walls. These technologies make use of a separate climate chamber and use air handling units to first pre-filter the cooled (or heated) air?before introducing it to the greenhouse by means of PE tubes that extend the full length of the greenhouse underneath the benches. These?air handling units make use of HEPA class filtration to?remove any organic or non-organic particulate matter that may be present, such as smoke, diesel fumes, pollen, dust, or microorganisms, before they?enter the greenhouse.?Warm air from the top of the greenhouse can also be recirculated back through the climate chamber and as such be re-filtered before being reintroduced to the greenhouse by means of the tubes, thus ensuring a substantially cleaner and more homogeneous climate.

?Water Chillers:

Evaporative cooling is usually only used in hot & dry climates. Traditional wet walls tend to lose efficiency in areas with higher humidity due to the extra moisture content of the air (already moisture laden) being unfit for purpose of evaporation, rendering the cooling process much less effective. Using an air-cooled?water chiller to pre-cool water before it is used in a wet wall system can result in more efficient cooling of the greenhouse. Here are some reasons why:

Improved Temperature Control: A water chiller allows you to lower the temperature of the water used in the wet wall system to a specific desired level. This pre-cooled water can effectively lower the temperature of the greenhouse more efficiently than using unchilled water. By maintaining a consistent and controlled temperature, the chiller helps create an optimal environment for plant growth while minimizing temperature fluctuations.

Enhanced Cooling Efficiency: Pre-cooling the water with a chiller increases the temperature differential between the water and the greenhouse, improving the heat transfer process. When the cool water passes through the wet wall pads, it absorbs more heat from the greenhouse air, resulting in better cooling efficiency. This allows the wet wall system to cool the greenhouse more effectively, providing a more comfortable and favorable climate for plant growth.

Energy Savings: By pre-cooling the water with a chiller, you can reduce the workload on the wet wall system itself. The chiller can operate during off-peak hours or when electricity rates are lower, taking advantage of cost-saving opportunities. Additionally, with the water already chilled, the wet wall system's fans and pumps may require less energy to circulate the water and maintain the desired cooling effect, leading to potential energy savings.

Increased Control over Humidity: In addition to temperature control, pre-cooling the water with a chiller can help regulate humidity levels in the greenhouse. As the cool water passes through the wet wall pads, it not only cools the air but also helps to remove moisture through the process of evaporation. This can be particularly beneficial in humid climates or during periods of high humidity, as the wet wall system can effectively contribute to reducing excess moisture and maintaining optimal humidity levels for plant growth.

Improved Plant Health and Productivity: Consistent and efficient cooling provided by the pre-cooled water can contribute to improved plant health and productivity. By maintaining appropriate temperature and humidity levels, the wet wall system helps create a more favorable growing environment. This can result in healthier plants, enhanced photosynthesis, better nutrient uptake, and ultimately increased yields.

It's important to note that the efficiency of the cooling system will also depend on factors such as the design and maintenance of the wet wall system, greenhouse size, climate conditions, and crop requirements. However, incorporating a water chiller to pre-cool the water can certainly enhance the overall cooling efficiency of the wet wall system and contribute to a more optimal greenhouse climate for plant cultivation.

Holes in the Bench Trays:

To further improve the distribution of treated?air within the greenhouse, holes are placed in the benches ebb & flood?trays to allow the air to rise up through the plant canopy. This helps to maintain a more equal distribution of?air, thus reducing the risk of temperature and humidity gradients. Additionally, it also?helps to keep the boundary layer surrounding the leaf fresher, minimizes the development of micro-climates?and maintains?positive air pressure to limit pests and further reduce the risk of microbial contamination.?This new tray design is especially effective when coupled with hydronic heating or cooling.

Hydronic Heating

Hydronic root heating is used to warm the root zone of plants by circulating warm water or a heating solution through a network of pipes placed in close proximity to the plant roots. This method offers several benefits that can positively impact plant growth, especially in cooler climates or during periods when root temperature management is critical.Some of?the advantages of hydronic root heating?are:

Temperature Regulation: One of the primary benefits of hydronic root heating is the ability to maintain optimal root zone temperatures. In colder climates or during chilly seasons, low root zone temperatures can impede root development and nutrient uptake. Hydronic root heating allows for precise control of root zone temperatures, ensuring that the roots remain warm and facilitating optimal plant growth and productivity.

Accelerated Growth and Development: Warm root zones promote faster germination, root growth, and overall plant development. By providing a consistently warm environment for the roots, hydronic root heating stimulates root activity, leading to improved nutrient absorption, enhanced metabolic activity, and accelerated plant growth. This is particularly beneficial in early growth stages when root establishment is critical.

Extended Growing Season: In regions with short growing seasons or cold climates, hydronic root heating can help extend the growing season. By maintaining the root zone at an optimal temperature, plants can continue to grow and thrive even when external temperatures are too cold for normal growth. This allows for an extended period of crop production and can increase overall yield.

Enhanced Nutrient Uptake: Warm root zones facilitate efficient nutrient uptake by promoting enzymatic activity and nutrient solubility. When roots are exposed to colder temperatures, their ability to absorb and transport nutrients can be compromised. Hydronic root heating ensures that the roots receive the warmth they need to efficiently absorb and utilize essential nutrients, leading to improved plant health and vigor.

Disease Prevention: Certain plant pathogens are more prevalent in cold and damp soil conditions. By maintaining the root zone at a warmer temperature, hydronic root heating creates a less favorable environment for the growth and development of these pathogens. Warm roots are less susceptible to diseases, reducing the risk of root rot, damping-off, and other soil-borne?infections, thereby promoting healthier plants and higher crop yields.

Environmental Efficiency: Hydronic root heating systems can be integrated with other environmental control systems, such as greenhouse heating and energy management systems. By utilizing the same water circulation infrastructure, the overall energy efficiency of the greenhouse or growing facility can be improved. This integration allows for a comprehensive?approach to environmental control, reducing energy consumption and optimizing resource utilization.

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Hydronic Cooling

Hydronic root cooling is used?to cool the root zone of plants by circulating cool water or a cooling solution through a network of pipes placed in close proximity to the plant roots. This method offers several benefits that can positively impact plant growth, particularly in hot climates or in situations where root temperature management is critical. The advantages of hydronic root cooling?are:

Temperature Control: One of the primary benefits of hydronic root cooling is the ability to maintain optimal root zone temperatures. Excessive heat in the root zone can lead to stress, reduced nutrient uptake, and hindered plant growth. By circulating cool water through the pipes, the temperature of the root zone can be effectively regulated, ensuring a more favorable environment for root development and overall plant health.

Enhanced Nutrient Uptake: Cooler root temperatures can improve nutrient uptake efficiency. When the roots are exposed to high temperatures, the absorption and assimilation of nutrients can be compromised. Hydronic root cooling helps to maintain cooler root temperatures, enabling better nutrient uptake and utilization, which ultimately promotes healthier and more vigorous plant growth.

Reduced Heat Stress: In hot climates or during heatwaves, plants can experience heat stress, leading to wilting, leaf damage, and reduced photosynthetic activity. Hydronic root cooling provides a direct cooling effect on the roots, which helps to mitigate heat stress. By maintaining a more favorable root zone temperature, plants are better equipped to withstand high ambient temperatures and maintain optimal physiological functioning.

Enhanced Water Uptake: Root cooling can improve water uptake efficiency by reducing the transpiration rate. When the root zone temperature is too high, plants tend to transpire more rapidly, leading to excessive water loss. By keeping the roots cool, hydronic root cooling minimizes transpiration, allowing plants to conserve water and optimize water uptake. This is especially beneficial in water-limited environments or during periods of drought.

Disease Prevention: Cooler root temperatures can also help suppress the growth and development of certain plant pathogens. Some soil-borne?diseases thrive in warmer environments, and by reducing root zone temperatures, hydronic root cooling creates a less favorable habitat for these pathogens. This can contribute to the prevention and management of diseases, leading to healthier plants and improved crop yields.

Environmental Efficiency: Hydronic root cooling systems can be integrated with other environmental control systems, such as greenhouse heating and cooling systems. By utilizing the same water circulation infrastructure, the overall energy efficiency of the greenhouse or growing facility can be improved. This integration allows for a more comprehensive approach to environmental control and resource management.

Positive Impacts on Contamination in Cannabis Facilities:

The positive impacts of the above?technologies?are particularly significant for the cultivation of medical cannabis. The strict quality control and safety requirements in medical cannabis facilities necessitate a clean and contaminant-free environment. By minimizing the risk of microbial contamination and ensuring a consistent growing environment, cultivators can maximize the yield and quality of their medical cannabis crops.

Furthermore, the implementation of these advanced climate?technologies can lead to increased operational efficiency and cost savings. With improved air distribution and reduced energy consumption compared to traditional methods, cultivators can achieve better temperature and humidity control while reducing their environmental footprint.

As the medical cannabis industry continues to grow and evolve, it is crucial for cultivators to stay at the forefront of technological advancements. The adoption of newer evaporative cooling technologies not only enhances the productivity and quality of medical cannabis but also aligns with the industry's commitment to providing safe and effective treatments for patients in need.