As per industry estimates, heating ventilation and air conditioning (HVAC) systems account for 40 per cent of the energy consumed by buildings in India and therefore remain the key focus area for energy savings through system upgrades and optimisation. According to the Indian Society of Heating, Refrigeration and Air Conditioning Engineers, most of the commercial buildings have an energy performance index (EPI) of 200 to 400 kWh per square metre per year. HVAC systems, when run efficiently, can help buildings achieve a better EPI of 100 to 120 kWh per square metre per year, which makes the buildings energy efficient. Such concepts have brought a paradigm shift in HVAC technologies and trends, where the majority of changes are aimed at achieving energy efficiency and higher energy performance.
There are two important features in the HVAC system: the heating systems and the control systems. In heating systems, proper selection and use of boilers provides significant scope of energy efficiency and savings. Similarly, the control systems need to be deployed to operate efficiently and ensure safety of the equipment.
For buildings that need heating systems, boilers offer the best choice for HVAC. Since heat in a boiler system radiates from the radiator into the air that already exists, no new air enters the space, whereas in forced air systems the new air often causes dust and allergens to infiltrate the atmosphere. Special features like user-friendly programming and zoning capabilities are some of the added benefits of boiler-based heating systems. In addition, these systems provide quiet operations.
There have been many innovations in the boiler industry, which have been driven by factors such as heating and cost efficiency. Each type of boiler is suited for a particular building capacity and design, and comes with its own set of issues and challenges. Hence, proper size and selection of boilers are extremely important for making boiler-based heating systems efficient.
Traditionally, there have been two categories of boilers: steam boilers and hot water boilers. The hot water boilers are more efficient than steam boilers because of a number of reasons. First, there is less heat loss throughout hot water piping and the shell of the boiler because the hot water boiler operates at a lower temperature than the steam boiler. This means that there is less heat loss in the entire boiler and piping system. Second, owing to the fact that the hot water boiler operates at a lower temperature, it requires less fuel or energy to convert into heat.
Boilers can be further classified based on the combustion efficiency levels. While the first category includes water tube boilers and fire tube boilers, the second category includes condensing boilers.
The water-tube boilers are generally found in medium to large commercial/ industrial applications and their efficiency depends on several factors such as whether it is a steam boiler or hot water boiler, the combustion controls being used and the type of flue dampers. In addition, the frequency of tune-ups and/or air and/or water pre-heaters can determine efficiency. Fire-tube boilers on the other hand restrict the combustion process and gases to tubes and water circulates around these tubes. Some fire-tube boilers have turbulators inside the tubes to cause turbulence of the flue gases, which in turn increases the heat absorption, thereby making the boiler more efficient.
The condensing boilers are comparatively more efficient than the conventional atmospheric boilers. A condensing boiler typically has two heat exchangers and absorbs more heat from the flue gases. As a result, moisture in the flue gases condenses. Given that condensed liquid is highly corrosive, it is necessary to build the condensing boiler out of special materials to prevent corrosion. Condensing boilers can be over 90 per cent efficient, however, they are a bit more complex and more expensive.
The IoT solution
An emerging technology trend in the HVAC business is that of internet of things (IoT), which is said to be a game changer for the industry. IoT allows the use of sensors to monitor different conditions in any environment. When devices are connected to each other and to the internet, the resulting communication and data enables buildings to operate at peak efficiency. For instance, smart heating controllers can be retro fitted to any boiler or heating system. These devices monitor, control and regulate heating within buildings. They can also help monitor the current health of a boiler and allows industry users to change from reactive to proactive maintenance schedules.
HVAC systems that can make their own intelligent decisions based on presence, weather and other indicators have a great potential to cut energy use and cost. Connected systems are able to analyse the information they gather and alert managers about unusual equipment behaviour or system failure, which results in quicker response times and help avoid potentially devastating problems. Further, internet-based systems help reduce maintenance and repair costs over time. Thus, many aspects of the HVAC industry can be improved through IoT, from preventive maintenance, responsiveness and increased energy efficiency to improving contractors’ work processes.
Implementing proper controls corresponding to each of the three components of the HVAC system (heating, ventilation and airconditioning) increases the efficiency of the system and leads to energy savings as well. Heating controls, in specific are required to ensure that heating systems operate safely and efficiently. A aood control system not only saves energy, but also maintains a consistently comfortable environment for building occupants, as well as reducing plant maintenance costs.
There are various ways to control the output of a commercial boiler. The simplest one is the cycling or on/off control of boilers to meet part load conditions. Another type of control is the high-fire/low-fire controls that provide fewer off-cycle losses since the boiler shuts off only when loads are below the low-fire rate of fuel input. The third one is the modulating control, which is used mostly in large boilers because of its ability to adjust the output to match the load whenever it is greater than the low-fire limit, which is usually not less than 15 per cent of the full load capacity.
The other category is that of time controls. If set correctly, time controls ensure that the system operates at the best times in terms of building occupancy and requirements. Lastly, the temperature controls help heating systems provide right temperatures to maintain comfort without wasting any energy and money. Most heating systems have some sort of temperature control. The two most basic and common kinds of building temperature control are wall thermostats and thermostatic radiator valves.
The HVAC system along with boilers represents the most significant feature of an energy consuming equipment. A better understanding of their functions and how they can be best controlled may lead to large energy savings for residential, commercial and industrial complexes. While opting for HVAC systems, various factors should be considered such as application, special requirements of the process, space available, load variations, operating reliability, energy conservation and total cost. Besides, constant monitoring, upgrading and suitable building design can considerably reduce the amount of emissions and energy wastage, thereby leading to energy and cost savings.