Evaporative Cooling Strategies for Indoor Farming
Indoor farming is a burgeoning market that requires adequate environmental controls to ensure proper temperature and humidity levels. Evaporative cooling technologies play a key role.
It is a sign of the times: Rapidly expanding commercial marijuana-growing facilities are defining a new model for indoor food production and processing. The rapid innovation and processes related to this burgeoning industry are already having an impact on traditional farming. At the same time, population growth experts assert that by 2050, agricultural production will need to rise by 70 percent to meet projected demand. Indoor agriculture will play an important role in this new era of food production too.
Today, indoor farming is a $500 million industry, and significant expansion is expected. Drivers include urbanization, the local-food movement and consumer preference for fresh foods. Boutique indoor vegetable-growing facilities have cropped up in metropolitan areas, and some are likely blossom into large-scale commercial facilities with continuous food production to meet market demand.
The future for indoor agriculture looks a lot like manufacturing of the past — maximizing production and minimizing risks. It will play an important role in food security in the United States and around the world.
One crop taking early advantage of the benefits of indoor gardening is the burgeoning legal marijuana trade. Estimates say as much as 92 percent of the legal marijuana production today occurs indoors. Marijuana Business Daily cites greater control, security and more crop cycles than outdoor growing as key drivers. These advantages are offset by a daunting challenge: the cost of greater energy consumption and its impact on carbon emissions.
Perhaps the most critical component of any indoor-farming operation is proper environmental control. A climate-control system takes into consideration sensor placement (to monitor temperature, humidity and energy consumption) and adequate controls for heating, cooling and air handling.
To meet the challenges of indoor agri-business, refrigerant- free, evaporative cooling technology has been shown to help improve yields. Evaporative cooling also has reducing power usage by as much as 70 percent compared to traditional space-cooling technologies such as air conditioning.
Though some may label evaporative cooling as swamp cooling, modern evaporative cooling technologies take advantage of sophisticated controls and deliver energy efficiency. Evaporative cooling can used for indoor-farming applications and help those production facilities tightly monitor and adjust the amount of outside air and return air as well moisture level. The result: the optimal balance of temperature and humidity to maximize production.
Energy-Efficiency Strategies for Evaporative Cooling
Energy-efficient cooling technologies can reduce operating costs by as much as one-third while keeping indoor-growing operations within optimal temperature parameters. For new or retrofitted indoor-farming facilities, decision makers should consider three important energy-efficient strategies that can be achieved with a well-designed evaporative cooling system:
- Air-Handling Efficiency. High performance air-handling efficiencies using direct-drive plenum fans with variable-frequency drive (VFD) controls reduce energy consumption when the equipment is operating at part load. Variable-speed fans are the preferred choice from a power standpoint because there is a direct relationship between fan speed and power consumed. Power reduction also can be achieved with electrically commutated (EC) fans with built-in speed control.
- Evaporative Cooling Efficiency. Refrigerant-free evaporative cooling technology reduces power usage significantly when compared to traditional air conditioning. Options include using outside air to offer free cooling as well as to offset process exhaust air losses.
- Control Efficiency. Direct digital controls help monitor and adjust ambient conditions (on-site or remotely via the Internet) to maximize energy efficiency and yield. Smart controls can provide data for production analyses and help pinpoint cost savings. Careful review of environmental data — including tracking temperature and humidity levels — are critical for determining yield, appearance, potency and overall product quality.
Budding Expertise: Environmental Control for Indoor Cultivation
Open floor-plan farms housed in old factories or warehouse settings face natural heat stratification. This can be particularly challenging for vertical-farming operations: The air temperature 1 foot off the floor is going to be much cooler than the air temperature 20 feet up. The temperature differential can be as much as 1°F per vertical foot. Yet, with the right controls and efficient air-handling systems, temperature and humidity disparities can be reduced.
All vegetation has its “preferred” growing environment. For cannabis plants, the key to production is consistency — with less than 2°F of deviation from the desired air temperature and less than 2 percent variation from the target level of humidity. This requires careful management of complex criteria — temperature, humidity and air handling — that is nearly impossible to manage effectively by manual means.
Direct digital controls for onsite/offsite management of temperature, humidity and lighting provide growers with invaluable data regarding the energy consumption and environment required to produce a crop. This means growers can identify the environmental conditions in relation to both exceptional harvests and crop failures, giving them the intelligence to increase yield and reduce risk.
Biosecurity Strategies: More Than a Lot of Hot Air
Looking again toward the commercial cannabis industry, producers must take into consideration regulatory and compliance issues that can have a significant impact on the bottom line. For example, in Colorado alone, local regulators ordered 15 recalls of contaminated marijuana over a 16-week period, resulting in a loss of nearly $180 million.
To avoid such losses in the future, many growers have instituted biosecurity measures as a means to reduce risks, including the transmission of infectious diseases, quarantined pests and living modified organisms. Given that plants can fall prey to mildew, spider mites and other predators that — in the span of a single day — can render an entire crop a total loss, air handling plays a vital role in minimizing contamination.
Computational fluid dynamics (CFD) — though not yet widely used for environmental temperature control — is a technology that some evaporative cooling equipment providers have integrated into their service offering to ensure humidity, temperature and particulates are managed appropriately. For example, using CFD to run a particle trace analysis helped animal researchers discover how infectious disease particles travel through the air. These results helped them determine the best way to pressurize a clean room and minimize the spread of disease.
Such a system could prove invaluable to cannabis-growing environments where airborne and human-borne contaminants are continuous threats.
Well-Designed Evaporative Cooling System Delivers for Indoor Farming
The phenomenal interest in indoor farming has created new challenges for reliable production and processing. What is needed is a comprehensive integration of environmental control hardware and software with sensors and controls. A largely automated infrastructure will help ensure the right environmental conditions at the right plant, at the right time, without interruption.
Indoor-farming processes can be a 24-hour-a-day operation. Increased competition and rapid industry growth do more than impact product development and pricing. They necessitate careful attention to creating production strategies that support optimal quality and maximum yields economically.
A well-designed evaporative cooling system — planned with CFD modeling, and monitored and modified with modern direct-digital controls — is an innovative solution for the burgeoning indoor-farming industry. Growers may find a shorter path to achieving indoor-growing conditions by working with companies that can help install, plan, design and manage the right solutions. Indoor agriculture is a sophisticated business. The environmental control strategies should be too. PC
Editor's Note: This article was published with the headline, "Don't Bet the Farm" in the January/February 2017 issue of Process Cooling.