Smart selection, operation and maintenance strategies for sustainable energy savings

HVAC systems account for a major portion of energy consumption in commercial and industrial applications. In this article, Sandeep Rane, Director at Sheetal Academy, discusses implementing energy-efficient solutions from the project planning stage through operation and maintenance as crucial to optimising performance, reducing costs, and ensuring sustainability.

HVAC systems consume almost 40 percent of electrical energy in any commercial application. In industrial applications, they are a Major power consumer. Hence, it is essential to install and run an energy-efficient HVAC System. Planning starts at the project stage and continues through operation and maintenance. Selecting the proper equipment for your project is very important. The main equipment of any HVAC System is a Chiller, AHU, Pumps, and Cooling tower (in the case of a water-cooled chiller).

When selecting chillers, prioritise those with flooded-type evaporators wherever possible, ensuring a Coefficient of Performance (C.O.P.) between 5.6 and 6.2 and electrical consumption of 0.57 kW/ton at full load by AHRI 550/590 (IP) and 551/591 (SI) standards. The standard rating condition should achieve an IPLV.IP as low as 0.34 kW/ton. Opt for oil-free operation and choose chillers with built-in Variable Speed Drive (VSD) and a two-stage compressor design to enhance full- and part-load performance. Refrigerant-cooled compressors should comply with AHRI 550/590 and 551/591 standards, while absorption chillers should adhere to AHRI Standard 560. Additionally, it is recommended that a soft start module be incorporated to minimise inrush current during start-up.

Air-handling unit

When selecting an Air-Handling Unit (AHU), it is better to choose a double-skin modular design with insulation thickness between 25 mm and 50 mm, ensuring a density of 40 kg/m³ and a thermal conductivity of 0.07 W/m·K for optimal energy efficiency. Modern EC motor-driven AHUs should be preferred over traditional belt-driven systems, along with axial fans instead of centrifugal fans, to enhance airflow performance. The AHU’s performance must comply with industrial standards such as AMCA 210, AHRI 430, and ASHRAE 51. Direct-drive fans are more efficient and reliable than belt-driven alternatives and should be preferred.

Energy Star-certified equipment increases energy efficiency. Additionally, installing the correctly sized air compressor and operating it with a Variable Speed Drive (VSD) ensures optimal performance and energy savings. Building projects should adhere to the mandatory provisions of ASHRAE 90.1 to maintain high efficiency and sustainability. The low-emissivity, double-pane glass further improves insulation by reducing heat transfer and enhancing overall building efficiency.

Operation and maintenance of HVAC systems

Effective operation and maintenance of HVAC systems require regular energy audits to monitor and optimise energy consumption. Managing energy usage involves collecting and analysing data from all HVAC equipment to ensure performance remains at its peak. A comprehensive preventive and predictive maintenance schedule is crucial to sustain system efficiency and longevity.

Neglecting maintenance in cooling towers can impact chiller efficiency, reducing it by 10 to 35 percent. In the case of air-cooled chillers, dirty condenser coils can cause efficiency losses ranging from 5 to 15 percent. Even a slight decrease of 1°F in the cooling water temperature from the cooling tower can improve the overall chiller system efficiency by 1 to 2 percent for water-cooled condensers. Proper annual chemical cleaning of the internal surfaces of the condenser and evaporator coil pipes enhances heat transfer, leading to energy savings of 5 to 15 percent in terms of kW per ton.

Proper insulation of chilled water pipes is equally important, as worn-out insulation results in a loss of thermal efficiency in the chiller system. Additionally, air compressors should be routinely checked for air leaks and pressure drops under ideal conditions to prevent energy wastage and maintain optimal performance.

Expertise shared by-
Sandeep Rane
Director
Sheetal Academy.