Sustainable Cooling for Livestock & Hatcheries

As our mother-earth faces escalating temperatures and increased energy use, innovative cooling methods have become vital. Evaporative Air Cooling (EAC) systems, an important element of Heating, Ventilation, and Air Conditioning (HVAC) systems, present a promising alternative to traditional mechanical air conditioning approaches.

The Evaporative Air-Cooling system, based on thermodynamic concepts, is a key part of contemporary HVAC setups. By utilizing the natural phenomenon of evaporation, EAC systems provide a sustainable and energy-efficient cooling solution. As we aim for sustainable development, choosing Evaporative Air-Cooling systems over conventional air conditioning will be essential, especially in areas where relative humidity is a significant concern.

Thermodynamic Principles of Evaporative Air Cooling

Evaporative Air-Cooling systems follow the fundamental principles of thermodynamics to cool air:

• Evaporation: When water evaporates, it absorbs heat from the surrounding air, cools it.
• Heat Transfer: The heat transferred from the air to the water vaporizes the water, thereby reducing the air temperature.
• Humidity: The humidity in the cool air thus increases, allowing it to absorb more heat.

What is Evaporative Air Cooling?

Evaporative Air-Cooling systems take advantage of the natural evaporation process to lower air temperatures. By channelling air through a moist medium, heat is absorbed, resulting in cooler air without the need for refrigerants. The mechanism of evaporative cooling involves the evaporation of water into the air. For this evaporation to occur, heat must be absorbed, which comes from the warm outside air introduced into the home for ventilation.

As the hot outdoor air interacts with the damp evaporative cooling pad, some of the heat is taken up by the water, leading to a decrease in air temperature. The temperature of the water remains constant during this process; it merely transitions from a liquid to a vapor state.

The efficiency of evaporative cooling is influenced by the weather conditions. The indoor air temperature can theoretically only be lowered to the dew point temperature, which is determined when the air is fully saturated with moisture (when relative humidity reaches 100 percent).

Typically, the gap between the air temperature and the dew point is largest during the hottest parts of the day. Consequently, an evaporative cooling system performs best during these peak heat hours. The theoretical efficiency of the system is capped by the dew point temperature, and the actual indoor air temperature cannot be cooled down to this level.

However, with a well-maintained system, the indoor air temperature can be decreased to within 3 °F – 5 °F of the dew point temperature. Evaporative cooling is an economical method for alleviating heat stress caused by high summer temperatures. This environmentally friendly technology lowers energy usage and operational expenses. The Evaporative Air-Cooling procedure consists of taking in hot outdoor air and directing it through a moist medium such as pads or mist. Throughout this process, the water evaporates, which cools the air. Finally, the chilled air is circulated to the specified areas.

Benefits of Evaporative Air Cooling in HVAC

• Energy Efficiency: Up to 80% less energy consumption.
• Environmental Sustainability: No refrigerants, minimal carbon footprint.
• Cost-Effectiveness: Lower capital, installation and maintenance costs.
• Improved Indoor Air Quality: EAC enhances ventilation by introducing 100% fresh, cooled air. It’s based on a natural cooling process eliminating the recirculation of stale air.

Application of Evaporative Air-Cooling systems

Evaporative Air Cooling (EAC) systems offer a promising alternative to traditional air conditioning methods, particularly in regions like Central India. By providing a comfortably cooled environment, animals and poultry can experience better weight gain, better production and improved reproductive characteristics.

• Industrial Cooling: Factories, warehouses, and manufacturing units.
• Commercial Spaces: Offices, shopping malls, and restaurants.
• Residential Cooling: Homes, apartments, and housing complexes.
• Agricultural Cooling: Dairy farms, Hatcheries and Livestock shelters.

The Importance of Evaporative Air Cooling in Livestock

As the farming sector continues to advance, enhancing the health and productivity of livestock has become crucial. By ensuring a comfortably cooled atmosphere, both animals and poultry can achieve improved weight gain, increased production, and enhanced reproductive traits. Evaporative Air Cooling (EAC) systems have emerged as an essential solution, particularly for dairy operations.

Elevated temperatures can result in slowed growth rates, lower fertility, higher mortality rates, and diminished milk output. In dairy farms, EAC systems can have a significant effect on milk production.

• Temperature regulation: Maintaining comfortable temperatures (28-32⁰C) for buffalo comfort.
• Stress reduction: Minimizing heat stress, which can decrease milk production.
• Improved feed intake: Encouraging buffaloes to consume more feed, leading to increased milk production.

Studies have shown that EAC systems can increase milk production by 10-15%, improve feed efficiency by 5-7%, reduce mortality rates by 11-20%.

Evaporative Air Cooling in Hatcheries

Basically, chickens don’t sweat, which makes cooling them a challenge. They may cool themselves in two ways, though:

• Through air movement, and
• Through the evaporation of moisture from the respiratory tract.

An increase in the amount of air breathed per unit of time, typically accomplished by quick, shallow breathing or panting, can improve respiratory evaporation. The relative humidity of the air a bird breathes determines how much heat it loses through panting. The body loses more heat and moisture when the relative humidity drops. However, if the bird is breathing the air that is already between 32 – 35⁰C, it cannot drain much water from its respiratory system.

EAC systems are highly beneficial in hatcheries, providing:

• Temperature control: Maintaining optimal temperatures (28-32⁰C) for chick growth and development.
• Humidity management: Regulating humidity levels to prevent respiratory issues.
• Improved air quality: Removing ammonia and other harmful gases.

By implementing EAC systems, hatcheries can increase chick survival rates by up to 20%, enhance growth rates by 15-20%, reduce disease susceptibility.

For cattle productivity, evaporative air-cooling devices are an essential investment. EAC systems can extend the lifespan of hens and cocks and boost buffalo milk output by controlling temperature and humidity. Adopting cutting-edge cooling technologies will be essential for sustainable growth as the agriculture sector continues to change.

The chicken sector benefits from evaporative cooling systems, but there are drawbacks as well. They enable the development of robust, lucrative flocks in the face of harsh summer circumstances when combined with tunnel ventilation. Increased air flow over the birds is necessary to counteract the high humidity levels they produce in the house. Indeed, the effectiveness of an evaporative cooling system in a poultry house is highly dependent on the ability to circulate air efficiently.

The principle of evaporative cooling relies on the fact that as air passes over water, the water evaporates and absorbs heat from the air, thereby reducing the temperature of the air. This is why air movement is crucial; it allows for a constant supply of fresh, hot air to be cooled and the removal of the warm, moist air.

A Viable Solution for Central India

I have played a pivotal role in promoting Evaporative Air-Cooling technology in Central India and my extensive research aided with hands-on experience in helping Optimized EAC system designs for regional climate conditions. Passionately, I educate and train professionals on EAC system installation and maintenance to implement energy-efficient solutions for industrial and commercial applications, in educating and training professionals. It is pertinent to highlight the success stories and case studies done by me in initiating and instigating the application of Evaporative Air-Cooling systems in Central India region. A few pioneering works contributed by me in successfully implementing EAC systems in Central India are listed below:

• Meena Bazaar: A garment shop in Nagpur achieved 70% energy savings using Evaporative Air-Cooling system.
• Apna Bazaar: A commercial complex in Nagpur reduced energy consumption by 60%.
• Karachi Super Bazaar: A supermarket in Nagpur reported improved indoor air quality and 40% energy savings.

Technical considerations for the selection of EAC Technology

Evaporative cooling media play a crucial role in air cooling systems by facilitating water distribution, maximizing air-water contact, and enhancing heat transfer. They provide a large, wetted surface area for efficient evaporation while preventing water droplet carryover.

The efficiency of these media is influenced by factors such as saturation efficiency, media thickness, face velocity, and water flow rate. Thicker media typically enhances efficiency, while optimal face velocity ranges from 1.5 to 2.5 m/s to balance cooling effectiveness and operational costs.

To optimize efficiency, design considerations include appropriate media selection, sizing, and water distribution, along with regular maintenance and water quality management. Additionally, evaporative cooling media have environmental benefits, contributing to energy efficiency and reducing water consumption compared to mechanical cooling systems.

Performance monitoring includes key metrics such as temperature reduction efficiency, pressure drop across media, water consumption rate, and achieved cooling capacity. Maintenance indicators to watch for include increased pressure drop, reduced cooling efficiency, uneven water distribution, and scale formation on media.

Optimization strategies focus on system design with proper media selection and efficient water distribution, operational control through variable speed fan and water flow rate adjustments, and regular maintenance like cleaning schedules and media inspections.

Cellulose pads offer high cooling efficiency (up to 85-90%), uniform water distribution, and a long lifespan of 3-5 years with proper maintenance, although they have a higher initial cost and require specific maintenance. They perform consistently across varying conditions and have a lower pressure drop compared to traditional media. In contrast, dry grass is a more cost-effective and environmentally friendly option, being biodegradable and easy to replace. However, it has a lower cooling efficiency (50-70%) and shorter lifespan (1-2 seasons), along with inconsistent water distribution and higher pressure drop due to its irregular structure.

Influence on Fan Selection

Factors for Cellulose Pads:

• Static Pressure Needs: A higher static pressure drop can occur, reaching 30-50 Pa for each inch of thickness. Additionally, the resistance to airflow can vary depending on the thickness of the cellulose pad, which means the fan must work harder to overcome increased air resistance.
• Fan Characteristics: Generally, stronger centrifugal fans are needed for improved pressure control, allowing for larger safety margins during fan selection.

Factors for Dry Grass (Wood wool):

• Static Pressure Needs: Fans can be optimized for better efficiency by reducing static pressure drop, which is typically 10-15 Pa for each inch of thickness. This adjustment helps fans operate more effectively.
• Fan Characteristics: Axial fans are generally the preferred option due to their power efficiency. These fans are notable for their moderate energy consumption, which translates to cost savings on electricity bills. They are designed with lower resistance, which is the primary reason behind their high energy efficiency. Moreover, they provide consistent performance, an attribute that is particularly valued when selecting an appropriate cooling solution. Essentially, axial fans serve as reliable and unobtrusive allies in maintaining an optimal temperature environment.

Fan Selection Recommendations

For cellulose pad systems, it is of paramount importance to adhere strictly to a series of essential steps:

To commence with, it is crucial to ascertain the precise total static pressure by meticulously assessing the resistance posed by the pads against the airflow. This parameter is of the utmost significance for ensuring optimal system performance. The selection of an appropriate fan is pivotal and should be undertaken by rigorously adhering to the manufacturer’s specifications. For typical configurations, a fan with a horsepower range between 0.5 to 0.75 is often deemed suitable for propelling 1000 cubic feet of air per minute

For dry grass (Wood wool) Systems, it is essential to incorporate a safety margin of approximately 25-30% to the calculated static pressure to allow for optimal system performance and flexibility.

This precaution ensures the system operates efficiently under various conditions. Fans with high-capacity capabilities that are designed to withstand increased pressure levels must be selected. These units are characterized by their robust nature, enabling them to function effectively in more demanding environments. As a standard guideline, a fan with 1.25 – 1.5 horsepower is typically sufficient for moving 1000 cubic feet of air per minute within this specific configuration. This power range is commonly observed in fans suitable for such systems.

Maintenance Considerations

• Cellulose Pads: Water treatment systems are necessary to maintain water quality. They require regular cleaning with mild soap, as well as frequent checks for mineral buildup. An annual inspection and replacement of pads is recommended.
• Dry Grass (Wood wool): They need frequent replacement, also need regular monitoring for any decaying but can be Cleaned simply by flushing with water. for best results seasonal replacement is recommended.

The choice between cellulose pads and dry grass (Wood wool) significantly impacts overall system design and fan selection. While cellulose pads provide higher efficiency and more predictable performance, dry grass (Wood wool) offers a cost-effective and environmentally friendly alternative. Proper fan selection must consider the specific characteristics of each media type to ensure optimal system performance.

G.J. Jiwani is a Post Graduate Mechanical Engineer from IIT Delhi, a Fellow of the Institution of Engineers (India) and a Chartered Engineer. He pursued his career as an HVAC Consultant since 1985 onwards in the Vidarbha region. He is regarded as a prominent icon for ventilation systems and evaporative cooling systems. He is the founder President of ISHRAE Nagpur chapter. He has been conferred with Lifetime Service Award and honoured with the title Chapter President Emeritus by ISHRAE.