Expert Column

Energy Efficiency in HVAC


HVAC system as an assembly is a most sensitive asset because it fetches high capital, operation and maintenance costs.

Business sustainability is a ‘talk of the town’ in recent days. What does it mean in real life and why business houses are keen to incline towards it? Every activity nowadays faces competition in its domain. Advancement in technology has gone hand in hand with advanced concepts in commerce also. Businesses are not so easy nowadays compared to some decades ago. Survival and long-term presence in competitive environment in general description is sustainability.

Sustainability comes through reliability, meaning: “Best quality products or services delivered at best quantity and minimum cost, time and time again.”

Operation Excellence (OPEX) and Reliability Centered Maintenance (RCM) are two key columns support any business house along with other support functions like supply chain management, control on Variable Operating Costs (VOCs) etc.

HVAC is one of many operations under OPEX and RCM heads contributing profitability. Cooling and chilling are most expensive operations in any process. There has been a great technological advancement in this sector in recent years, advancement in technologies, monitoring and controls. Efficient equipment like centrifugal, screw and scroll compressors, VAM, integral finned tube and modified internals of tubes used in condensers and chillers, finned tube air cooled exchangers, advanced cooling towers, better pumps and refrigerants. Smart HMI and controls have proved their purpose. Package HVAC systems are nowadays highly energy efficient.

Package units are good for their specific applications, but when it is a large installation, overall system integrity and efficiency must be considered carefully in terms of selection, installation, operation and maintenance too.

Primary and secondary pumping and piping system, cooling tower efficiency, pumps and fans, hydraulic balance, temperature and flow controls, temperature range, operate right equipment at right time, installation of equipment, ducting network and losses etc are important factors to be considered. HVAC system as an assembly is a most sensitive asset because it fetches high capital, operation and maintenance costs. ISO 55000/1/2 focus on Asset life cycle management, with extreme weightage on specifications considering all possible situations and their combinations, correct installations, right most and most reflexing operations and best maintenance practices.

For example in secondary chilling water circuit used to arrive HVAC functions among largely distributed installations connected to a common network with varying thermal loads and different temperature and humidity requirements verses discrete network for every individual HVAC unit or for a cluster of units based on their functionality or set of units at a floor in a building or building, has always been a debate amongst design engineers.

Since every operation has its own cost to company – CTC, distribution network operating cost becomes important. Specific power consumption KW/TR must include overall power consumption of a system not just a refrigerant component.

Discrete distribution network has many advantages over central distribution network of secondary circuit contributing to OPEX:
• Flexibilities in operations to react thermal loads and temperature – humidity requirement. Just required unit can be operated.
• Separate pumps for different flow and head requirement instead of one central pump for all heads always have lower operating costs.
• Selectivity of operation of two or more chiller units based on system loads is more advantageous compared to one unit operating at part loads with compromised efficiencies.
• Common chilled water tank with discrete distribution takes peak loads with great ease. And also impart selectivity of refrigeration units.
• Flexibility during outage of any component is well possible here.
• Discrete distribution system is a best selection for multiproduct business or seasonal products.
• Piping network will be complex and attract high capital investment initially, but has high ROI with better flexibilities and low costs of maintenance.

Operation of HVAC system is equally important for its efficiency and contributes a great to OPEX.
Qualified and experienced operators must be a fundamental selection criteria. Apart from selection, extensive training of operation of entire system and each of its components to operators and users is a vital factor for OPEX as well OEA – overall equipment availability and OEE – Overall equipment efficiency.

Right operations yield less outage. Professional maintaining of an asset is the key contributor. Re-establishing normality of an asset after overhauling, attending breakdown or preventive maintenance is a job of skilled and experienced person backed up with extensive training in doing so.

Authored by:
Jalendu Vadilal Shah Project and Engineering Head, Chemical Process Plants

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