Optimising Operations

High-performance HVAC systems could yield energy cost savings

Heating, ventilating and air-conditioning (HVAC) systems constitute a large part of a commercial building’s energy consumption. Industry estimates suggest that these systems account for around 40 per cent of the energy bill. Therefore, improving the operational performance and control of HVAC systems could result in significant overall cost savings. In view of this, building management systems and air-conditioning controls have evolved significantly over the years to perform more efficiently and cost effectively, and be more environment and user friendly. The use of high-performance HVAC equipment has the potential to yield energy, emission and cost savings of 10-40 per cent. Besides, with the deployment of internet of things (IoT), HVAC systems have become more intelligent and self-healing.

Key components of an HVAC system

An HVAC system has two key components: heating systems and control systems. In heating systems, the proper selection and use of boilers can help achieve energy efficiency and cost savings. The control systems manage the operations to ensure an efficient outcome and maintain equipment safety.

Boilers are the oldest heating solutions and are best suited for HVAC systems. Even the powerful HVAC systems used in hotels, warehouses and large stores utilise boilers to achieve the desired heating. Broadly, the boilers used for HVAC systems can be classified into two main categories: steam boilers and hot water boilers. These differ in design and piping configurations. While a steam boiler system is designed to turn the water into steam and uses gravity and pressure to deliver heat, a hot water boiler is designed to simply make hot water, which is circulated (using a circulator pump) through a piping system to provide heat. Both these boilers can be fuelled by oil, gas, or electricity. Generally, hot water boilers are more efficient than steam boilers. The former entails lesser heat loss throughout the hot water piping and the shell of the boiler since it operates at a lower temperature than the steam boiler.

Another categorisation of boilers is water-tube boilers and fire-tube boilers. Water-tube boilers comprise a number of tubes that circulate water and are surrounded by hot combustion gases. The exchange of heat is realised between the combustion gases and the tubes and water. The size of a water-tube boiler ranges from 10 million British thermal units (mBtu) per hour to boilers of 300 mBtu per hour. These are generally used in medium to large commercial/industrial applications. On the other hand, fire-tube boilers confine the combustion process and gases in tubes and water circulates around these tubes. Some fire-tube boilers have turbulators inside the tubes to cause turbulence of the flue gases. This increases the heat absorption by the water, which makes the boiler more efficient. Fire-tube boilers range in size from 0.6 mBtu per hour to 50 mBtu per hour. Since in the water-tube boiler steam and/or hot water are confined in the tubes, it can be built for higher capacities and high pressure conditions.

As per another classification, boilers in the HVAC system could be conventional atmospheric boilers and condensing boilers. Condensing boilers are more efficient than the conventional atmospheric boilers. They deploy two heat exchangers and absorb more heat from the flue gases. These absorb so much heat from the gases that moisture in the flue gas condenses, which needs to be drained off.

With regard to the control of the HVAC system, it comprises starting, stopping or regulating of the HVAC system’s operations. Control over the system is established by collecting the data, processing it with other information and undertaking control actions. Broadly, HVAC control systems use sensors, controllers and controlled devices to regulate the operations of the system. The sensor measures the actual value of controlled variables such as temperature, humidity or flow and provides information to the controller. The controller processes the input and generates a signal for the controlled device to accordingly modify the controlled variable. With the emergence of IoT and advanced communication technology, the control of an HVAC system has become more sophisticated over the years. The control of the HVAC system can now respond to change in the system’s performance on a near-real-time basis and help in maintaining efficient operations.

Emerging technology solutions

Over the years, there have been significant advancements in the HVAC systems deployed for commercial and industrial purposes. These technological advancements aim at improving operational efficiency, reducing utility bills, lessening the strain on the grid and the environment, and increasing user comfort. A host of technological advancements offering these benefits are fast gaining momentum. These include movement-activated airconditioning (sensors hung from the ceiling are activated by movement), on-demand hot water recirculator (cool water circulated back into the water heater) and ice-powered air conditioning (water frozen in a tank during off-peak hours used in a building).

Connected and intelligent HVAC system

IoT is revolutionising the commercial HVAC industry in a number of ways, ranging from remote diagnostics to increased efficiency. Internet-connected heating and cooling systems have the ability to continuously monitor conditions and system functionality with the help of smart sensors. Smart sensors installed at the desired points measure system performance parameters and the data thus collected can be transferred to a computer, smartphone or tablet over a Wi-Fi network. With the use of a well-suited operating system and an intelligent processor, the data from the system can be used to derive meaningful interpretations.

With regard to the benefits offered by IoT in an HVAC system, these broadly include seamless remote access, diagnosis and control functionality. Analysing the data collected from the system can help identify unusual equipment behaviour or system failure in a timely manner, thereby reducing the response time and lowering equipment downtime. With the use of IoT, an HVAC system can be configured to send alerts in case of any anomaly in system performance. It also helps in identifying situations such as excess energy consumption and equipment wear and tear, which could be precursors to the occurrence of a fault in the system. Preventive maintenance of the system could be based on such performance data to ensure uninterrupted performance.

Another important benefit of IoT in an HVAC system is minimising energy consumption. The use of thermal modelling technology for operating the building systems helps in obtaining the desired outcomes while minimising energy consumption and plant wear and tear. This regulates the operation of the system according to different ambient and occupancy conditions.

Conclusion

Although there have been significant technological advancements in the HVAC space to meet varying consumer requirements, ensure environment-friendly operations and minimise resource use, the high cost of technologies poses hurdles in their deployment. Industry estimates suggest that energy-efficient HVAC systems are 15-20 per cent more expensive than conventional ones.

Although the return on investment for more efficient systems can be substantial, shorter payback periods are required to increase their uptake. Therefore, it is essential that while establishing an HVAC system, the consumer undertakes a detailed cost-benefit analysis to identify the best-suited technology solution. Apart from this, regular maintenance of the HVAC system by a qualified engineer is essential for maintaining efficient system operations in the long run.

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