Experimental Investigation on Energy Saving Potential in AHU of an Air-Conditioning System with BLDC Fan

Abstract

Our current energy source is mainly based on fossil fuel which is depleting continuously day by day so all the efforts should be made to reduce the energy consumption with the help of different energy saving initiatives in all levels. As industries use significant part of the total energy consumption of the world, it is the main area to be studied for reduction in energy consumption. In this paper, a study is conducted on a conventional air-conditioning system of 300 ton of refrigeration capacity in a steel plant located in Jajpur, Odisha, India. The energy consumption on different elements of the air-conditioning system has been studied to get an idea of quantum of energy consumed in different sections. It is found that in an air-conditioning system, air handling units (AHUs) consume 24.5% of energy, whereas chiller consumes around 52.6% and others together consume 22.9%. Further energy consumption in AHU has been studied in detail for different drive systems to evaluate the most energy-efficient AHU system. Three numbers of AHU were studied with similar rated capacity of 40,000 m3/h and 15 kW fans. The first AHU is conventional in design having V-belt drive, second AHU has direct-coupled motor with variable frequency drive (VFD) motor and third AHU has brushless direct-current (BLDC) motor direct coupled with the fan. It is found that the conventional AHU system consumes 12.4 kW load at 34,702 m3/h, direct-coupled motor with VFD consumes 9.4 kW load at 34,935 m3/h and BLDC motor-driven AHU consumes 8.4 kW load at 34,702 m3/h. Hence, it is concluded that the BLDC motor-driven AHUs are most energy efficient compared to others. It is also observed that the highest internal rate of return (IRR) is coming in BLDC motor-driven system which is around 60% and noise level is also the lowest in BLDC fan that is 60 dB and the highest in conventional V-belt-driven AHU system that is 70 dB. Similar results are also found in carbon footprint study for 1 year (240 days) of operation of the AHU fan that is the lowest in BLDC motor-driven fan and the estimated value is 60.71 tons CO2 per year, whereas the highest carbon footprint is estimated in conventional V-belt-driven AHU that is 41.13 tons CO2 per year. Hence, we can conclude that by using an efficient drive system of an AHU like BLDC motor-driven fan, we can save energy as well as reduce the impact on our environment.