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Energy savings potential for commercial buildings hvac

Energy consumption has been growing exponentially over the years. Today, more than 4.7 million commercial buildings consume more energy than the transportation or industry sectors, accounting for nearly 40 per cent of total energy use as shown in Figure 1. The total energy used by commercial buildings topped in 2004-05.

Figure 1. Increase in HVAC energy use in different applications over the period of time

This increase in energy use is caused mainly by growing commercial floor space, which drives other buildings like schools and hospitals. Economic growth (GDP), which drives demand for floor space is shown in figure 2. Commercial buildings consist of various sectors like public utility buildings, hospitals, schools, malls, retail, restaurants and floor space as shown in figure 3. Among these, floor and retail occupy the major percentage. Commercial energy intensity has grown (Figure 4) and understanding the primary energy use (Figure 5) will help with energy cost saving measures.

Figure 2. Growth in HVAC energy consumption in commercial floor space.
Figure 3. Energy consumption in commercial buildings in India.
Figure 4. Electricity consumption growth in commercial buildings in India.

It is not surprising that heating and cooling are the predominant consumers of energy in a commercial building followed by lighting as shown in Figure 6. Here we take a look at some of the energy cost saving measures one can implement in order to meet the annual energy goals of a building.

Fig. 6. Commercial primary energy end use.

Energy saving techniques in HVAC for commercial buildings

Smart building concept

Smart building is the term used for buildings that have complete automated controls and systems in place. These controls comprise of sensors and actuators that are integrated together to form an intelligent data collection application. A smart building has an annual growth rate of 22.6 per cent and has the potential to reach USD 20 billion by 2020.
For optimal operation of utilities in buildings and avoid energy wastage as well as save energy costs, it is essential to collect extensive data and use it for operating various systems. For example, one can use the data to see how his or her HVAC is performing and control the temperature set points based on outside weather. One can also use a centralised command center to transmit any commands to change settings, adjust values and thus, save energy.

Smart building systems save energy costs because they provide visibility into the entire building even if the facilities are spread across a large area like a university. The data that these systems collect can be used for analysing, tracking and communicating.
Table 1 summarises the some of the advanced technology options that fall under alternate heating and cooling options to the conventionally used vapour compression based traditional air conditioners. Figure 7 shows energy saving potential for the technology options.

Figure 7. Comparison for energy saving potential in the different technology options.

Low cost techniques

Employing quick low-cost techniques can save substantial energy bills. For example, turning off office equipment like printers, monitors, computers and copiers into sleep mode when not in use will cut energy costs by approximately 40 per cent. Performing regular maintenance of HVAC system (Figure 8) is another low-cost way to ensure that the largest consumer of energy in building is efficient. Regular cleaning of coils and vents such as condenser and evaporator coils can produce energy savings of USD 0.10 per kWh.

Figure 8. Annual HVAC electricity consumption against COP.

IoT systems

The Internet of Thing or IoT is the latest technological innovation that is being increasingly used to manage energy efficiency. IoT uses the Internet to connect information gathered from various devices like sensors and actuators that are embedded within systems. IoT is typically used to collect information such as motion, air pressure, light, and temperature or water flow. When integrated with a Building Management System (BMS), it enables autonomous monitoring, control and provides advanced analytics where the data can be used for predictive modeling. This allows for higher cost savings, increased productivity as well as revenue benefits, especially with the data.

Advanced insulation

Adding layers of insulation around your HVAC, heating and cooling pipes, and electrical outlets will help with maintaining efficient energy levels and reduce wastage of energy. Insulation provides resistance to heat low and lowers the heating and cooling costs (Figure 9) and increases the comfort of the occupants. Another way to improve the energy efficiency of buildings is to reduce heat loss through the building envelope by internal or external wall insulation. By external wall insulation, the building will also benefit from aesthetic improvement besides improving the thermal comfort. Other advantages of installing the insulation on the outside include the reduced disturbance of the occupants, the disappearance of mold and reduced maintenance.

Figure 9. Annual HVAC electricity consumption against cooling temperature.

Building design

Using general cooling measures and ‘green’ designs help in reducing energy costs. Some of them are:

-Natural lighting and opening interiors to daylight
-Use of landscaping and trees to provide shaded areas and reduce local temperature
-Solar power panels can be installed on rooftops and can be used to power lights in parking spaces or even for water heating
-Designing a water collection system for irrigating landscaping in and around the building.

Figure 10. Annual total electricity consumption against lighting intensity.

Energy efficient lighting

Lighting makes up a significant portion of energy consumption after heating and cooling as shown in Figure 10. Hence, focusing on efforts to use energy-efficient lighting can help to cut down energy costs. Some of the ways one can do that is using occupancy sensors to operate the lights only when occupied. The other very successful way is to use a low energy consuming lights such as fluorescent, incandescent, halogen, LED or HID. The choice of type of lighting will depend on the specific lighting needs.

Fluorescent lighting is the most commonly used type of lighting: 93 per cent of commercial buildings use standard fluorescent lights, and standard fluorescents illuminate 78 per cent of lit floor space. Compact fluorescent (CFL) has become the second most common lighting type, providing light to 13 per cent of all lit space in commercial buildings. The remaining lighting types—incandescent, high-intensity discharge, halogen, and light emitting diode (LED)—each light less than 10 per cent of floor space across all commercial buildings.

Barriers to energy efficiency

-Lack of information about comparative energy use.
-Risk due to lack of confidence in performance of new technologies.
-Higher initial cost of EE technologies.
-Asymmetry in sharing of costs and benefits (especially in building sector).

Conclusion

Energy cost savings is on top of mind of every commercial building owner, operator or facility manager. There are many solutions available that can help you with energy cost savings. These range from implementing sophisticated technologies like IoT to low cost energy efficiency strategies like using natural light and finally using energy star rated equipment for long-term energy savings. Whatever is the solution, ensuring that you implement at least one or two frequently would ensure that your energy costs are considerably reduced and your energy savings substantially increases.


Dr. D.B. Jani,
Government Engineering College,
Dahod, Gujarat Technological University – GTU,
Ahmedabad, Gujarat, India.