Complex cooling control for cannabis products
Cannabis plants like long, warm days and short, slightly cooler nights. Leon Brülisauer, managing director of the CBD hemp startup LMP GmbH, has been involved in the cultivation of legal hemp plants for more than five years. “Precise regulation of the temperature, humidity, and light is what we need to harvest high-quality hemp flowers”, explains the qualified horticulturalist.
Stringent requirements for room air conditioning
For this to be successful, the hemp plants require specific climatic conditions for each separate phase of growth. Therefore, in a room holding the mother plants, cuttings are also cultivated, which takes 10 to 14 days. Following this, the plants come into the flower room for a good two months, where they flourish until they are harvested.
Precise regulation of the temperature, humidity and light is the prerequisite for harvesting high-quality hemp flowers.
Day and night phase control
Control over the day and night phases is particularly important. The plants require room temperatures of 18 to 20°C during the nighttime hours, and 26 to 31°C during the bright daytime hours. This is automatically controlled using light sensors. A sophisticated timing control system turns the light on and off and provides the plants with the push they need in order to grow. Because of the intensive lighting, the thermal load in the rooms is so high that they have to be cooled in a specific manner. This allows the plants to thrive under ideal growing conditions. At the same time, the cooling, together with de-humidifying equipment, also ensures the regulation of humidity in the rooms.
Standard products with a programmable logic controller (PLC) control system specially designed for the plant growth process.
Component interplay
Implementing the various climatic production conditions was challenging. Marzetti Gebäudetechnik GmbH were responsible for the design concept. The designer, Patrick Marzetti, explains: “In the beginning, there was the question of an exhaust air system for a new tenant of the industrial premises. This resulted in a close collaboration with Leon Brülisauer and, finally, a well-thought-out design for conditioning the hemp production rooms.”
Danijel Matic, Technical Sales Consultant in the Commercial Cooling & Heat Pumps Division at CTA, was actively involved in the design phase. The interdisciplinary team soon realised that it was not so much the individual room air conditioning components that were particularly demanding, but rather ensuring their perfect interplay and the associated regulation of different climatic zones and times.
Process-specific requirements for regulation
«The challenge lies in achieving perfect interplay of individual room air conditioning components and the associated regulation of different climatic zones and times.»
A focus on energy efficiency
The solution adopted comprises a CTA standard cooling system with a 70 kW cooling output. The cold water for 12 air cooling units (fan coils) is provided via an efficient, pre-installed Coolfit piping system in the plant rooms. The fan coils release cold air into the rooms via textile hoses. At the same time, they dehumidify the air in the room.
Particular attention was paid to the energy efficiency of the system. With the desuperheater, 10% of the chiller’s output is extracted at a higher useful temperature and transferred to a heat buffer tank. In this way, the heat can be used inside the industrial unit.
Quiet recooler with plenty of power
The recooler has an output of 240 kW. With this design, a second chiller can be connected, if required. The recooler, over seven meters long and two meters wide, has five ventilators and allows for active free cooling. During winter and in the transitional period, the chillers are completely switched off and the premises cooled using free cooling. A green and energy-saving solution.
In selecting a recooler, emphasis was also placed on keeping noise levels as low as possible, as the industrial estate on which the production building is located lies adjacent to a residential area.
The industrial estate borders a residential area. This is why a recooler with the lowest possible acoustic output was chosen.
Clever CPL control system creates value
On the “hardware” side of the air conditioning solution, standard products were widely used, which could be incorporated inexpensively and without major adjustments. The process-specific requirements for regulating the system proved to be a challenge. A programmable logic controller (PLC) was used, which CTA progressively adapted to Leon Brülisauer’s needs.
Complex technology, simple to operate
Following various improvements and readjustments, the system functioned reliably and robustly, and the first CBD crops could then be harvested. It therefore proves that, despite the complexities of air conditioning, a great emphasis was placed on ease of use. “This simplicity means that we don’t have to struggle with the technology every day, and that we can concentrate on our core business: cultivating CBD hemp plants”, says Brülisauer.
Contributors
Design: Marzetti Gebäudetechnik GmbH, Brislach
Installation: Meier-Kopp Service AG Basel, Reinach, Basel-Landschaft
Commercial Cooling & Heat Pump Products: CTA AG
