Heating ventilation and air conditioning (HVAC) systems and boilers are critical components of energy consuming equipment. They are primarily used to optimally heat or cool commercial areas such as hotels, restaurants, malls, shops and schools, in addition to households. According to industry estimates, HVAC accounts for 40 per cent of the energy bill. Therefore, by upgrading these systems with high performance equipment, consumers can unlock enormous efficiencies by economising costs and lowering energy intensity. Additionally, the sector is poised for tremendous improvement with the development and deployment of internet of things (IoT) technology, and the rising adoption rates of cogeneration and trigeneration.
HVACs generally consist of two essential subsystems: The control system and the boiler system. The control system manages operations to ensure an efficient outcome and maintain equipment safety, while the boiler system utilises energy to regulate the temperature. Proper selection and use of boilers in heating systems can help achieve energy efficiency and cost savings.
Boilers are the most used components for heating in HVAC systems. Even the powerful HVAC systems used in hotels, warehouses and large stores utilise boilers to achieve the desired heating. The boilers used for HVAC systems can be broadly classified into two main categories-steam boilers and hot water boilers. These categories are fundamentally distinguished by differences in design and piping configurations. While a steam boiler system is designed to turn 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 varieties can be powered by oil, gas, or electricity. Hot water boilers are generally more efficient than steam boilers, as they operate at lower temperatures and thus entail less heat loss throughout the hot water piping and the shell.
Water-tube boilers and fire-tube boilers are two other varieties. A water-tube boiler contains 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 water-carrying tubes. Water-tube boilers range in power from 10 million British thermal units (mBtu) per hour to 300 mBtu per hour. They are generally used in medium- to large-scale commercial/industrial endeavours. Fire-tube boilers, meanwhile, confine the combustion process and gases to tubes around which water circulates. Some fire-tube boilers have turbulators inside the tubes to create turbulence in the flue gases. This increases heat absorption by the water, which makes the boiler more efficient. Fire-tube boilers range in power from 0.6 mBtu per hour to 50 mBtu per hour. Since steam and/or hot water are confined in the tubes in water-tube boilers, they can be built for higher capacities and high pressure conditions.
As per another classification, boilers in an HVAC system could be either conventional atmospheric boilers or condensing boilers. Condensing boilers are more efficient than conventional atmospheric boilers. They deploy two heat exchangers and absorb more heat from flue gases – so much so that the moisture in the gases condenses and needs to be drained off.
HVAC systems designed for cooling include air conditioners (ACs) and air coolers. An AC runs refrigerant through coils in a loop. The refrigerant absorbs the heat inside a room as it turns from liquid to gas, then deposits the heat after condensing it into liquid. The issue with ACs and other systems designed for cooling is that they are expensive and emit hydrofluorocarbons (HFCs), which are thousands of times more detrimental to the atmosphere than carbon dioxide. Therefore, experts predict that in the medium-to-long manufacturers will phase out HFCs from ACs and will enhance the efficiency of ACs. Cleaner substitutes for HFCs already exist, pre-eminent among them being Hydrofluoroolefin, which are already being used in more than 70 million vehicle air-conditioning systems and have a climate impact on par with carbon dioxide. Furthermore, on the regulatory front, around 120 nations became signatories to the Kigali agreement in 2016, whereby they committed to phasing out HFCs over the next decade.
Efficiency enhancement also requires attention. There are many benefits to be reaped from it, considering that most existing cooling systems are significantly inefficient, as demonstrated by the Environmental Investigation Agency’s 2019 report suggesting that a typical cooling system leaks 25 per cent of its coolant each year. So the twin trends of improved efficiency and commerce, propagated by HFC-less ACs, are set to alter cooling systems. The government is endeavouring to enable the transition to HFC-less ACs through the Energy Savings Company Limited, which uses a business model wherein it sells more efficient replacements for existing equipment and recovers the price by obliging the consumer to pay a part of the energy savings thus accrued.
HVAC control systems and IoT
HVAC systems are controlled through real-time data collection, data analytics and by regulating the system in accordance with external conditions. Generally, HVAC systems use sensors, controllers, and controlled devices for operation, with the sensor measuring and providing the actual value of temperature, humidity or flow to the controller. The controller processes the input and generates a signal for the controlled device to accordingly modify the relevant variable. With the emergence of IoT and advanced communication technology, controlling an HVAC system has become a more sophisticated, efficient and non-intrusive process, with the possibility of programming responses on a near-real-time basis.
The incorporation of IoT-based technologies is set to improve the operation of HVAC systems. 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. These sensors are installed at the desired points to measure system performance parameters. 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 can be used to derive meaningful interpretations.
The other benefits offered by IoT in an HVAC system include seamless remote access, and diagnosis and control functionalities. IoT can assist in analysing the data collected from the system and help identify unusual equipment behaviour or system failures 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 if an anomaly is detected in system performance. IoT can also help in identifying situations such as excess energy consumption and equipment wear and tear, which could be precursors to a fault in the system. Such performance data can enable preventive maintenance, ensuring uninterrupted performance.
Another important benefit of IoT in an HVAC system is to minimise energy consumption. The use of thermal modelling technology to operate 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.
Emerging technology solutions
Over the years, there have been significant advancements in the HVAC systems deployed for commercial and industrial purposes. These technological advancements have aimed to improve operational efficiency, enhance durability, reduce utility bills, lessen the strain on the grid and the environment, and increase user comfort. The advancements that are gaining momentum today include movement-activated air-conditioning (sensors hung from the ceiling are activated by movement), on-demand hot water recirculators (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).
The efficiency of the sector is also bound to be augmented by the introduction of variable flow technology, permitting the operation of boilers over a wide range of flow rates with limited pressure drops. This will streamline installation by eliminating the time and materials cost of primary/secondary (boiler/system) piping, or the need for pumps to maintain flow. Variable flow technology can also make boilers more flexible in handling frequent fluctuations in system flow rate.
Most of the cutting-edge fire-tube heat exchangers used in cogeneration-based HVACs enhance the life of the heat exchanger by allowing the tubes to flex. This lets them operate stress-free, without the adverse effects seen in earlier generations of fire-tube heat exchangers. When each fire tube is welded into the heat exchanger and surrounded by water, the heat transfer process is enhanced by the water’s counter-flow motion. As water flows up inside the vessel, superheated flue products flow down the fire tube. With just one pass, heat is effectively transferred, thereby reaching condensing temperatures. At the top of the vessel, the combustion chamber is also water-backed for additional heat transfer.
Heating systems and boilers, as well as their replacements, are expected to become leaner, more affordable and more flexible. They used to be much sturdier and heavier in the past, which made it expensive to commission the replacement of certain parts within the boiler.
The Way Forward
In the future, driven by extreme climate change and the increased purchasing capacity of people in developing nations, the HVAC industry will inevitably witness unprecedented growth in demand for ACs, air coolers, boilers, heaters, etc. Consequently, the industry, the government and the consumers must proactively collaborate, deliberate and design a strategic blueprint comprising technical specifications, policy measures and financial mechanisms to facilitate the phased development, manufacturing and commerce of green, efficient, affordable, and technologically advanced HVAC solutions.