ABSTRACT

The potential of a variable speed compressor provide enhanced load-matching capability, energy saving and thermal comfort for application in air conditioning system is demonstrated. An air conditioning system, originally operates on an on/off control, was retrofitted with an inverter and controller using PID control. The system was installed to a thermal environmental room together with a data acquisition system to monitor the temperature of the room, compressor performance in term of coefficient of performance (COP), energy consumption and energy saving. Measurements were taken during a two hour experimental period at a time interval of five minutes for temperature setpoint of 20 C with internal heat loads of 0, 500, 700 and 1000 W. The system with variable speed controls the room temperature by changing its frequency. The higher the frequency the smaller is the value of COP. A high COP at a lower frequency is mostly due to the small compressor power consumption compared with that at a higher frequency. When the compressor power consumption increases, the COP decreases with the increase of the compressor frequency. The results indicate that thermal comfort of the room together with energy saving can be obtained through a proper selection of controller parameters. Energy analysis shows that PID controller ensures lower energy consumption and gives the highest saving followed by PD, P and PI in comparison with the conventional on/off control.


CONCLUSION
Energy and Compressor Performance of an Air Conditioning System using PID Controller oleh henrynasution
The controllers i.e. on/off and PID were developed to control the motor speed in order to maintain the room temperature at or close to the setpoint temperature. The on/off controller is used in many simple control systems, the controller turns on the motor compressor when the room temperature reaches the upper limit temperature setting, and turns off at the lower limit temperature setting. The PID controller tries to minimize the error between the setpoint temperature and the room temperature. If the room temperature reaches the setpoint, the motor speed abruptly reduced and fluctuates to maintain the room temperature. However, when the room is thermal loaded, the controllers act such that the heat recovery to the room is fast until the temperature setpoint is upheld again. The energy consumption would change with the change in motor speed. When the motor speed increases, the room temperature decreases and COP increases with the increase in energy consumption. Furthermore, the higher the energy consumption the smaller is energy saving.

A well-tuned PID controller that produced satisfactory solution in term of energy saving for the room was employed. The impacts of all controllers on the performance of the system, the room temperature and energy consumption have been analyzed experimentally. The trend of compressor performances in term of COP is found to be similar for all controllers studied. Energy analysis shows that PID controller gives the highest saving followed by PD, PI, and P in comparison with on/off controller. The main outcome of this study shows that using VSC and choosing suitable control strategy, it is capable to control the space temperatures with significant energy saving.
Energy and Compressor Performance of an Air Conditioning System using PID Controller oleh henrynasution
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Energy and Compressor Performance of an Air Conditioning System using PID Controller oleh henrynasution
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Energy and Compressor Performance of an Air Conditioning System using PID Controller oleh henrynasution
Dr. Ir. Henry Nasution, M.T
Staff Jurusan Teknik Mesin
Fakultas Teknologi Industri
Universitas Bung Hatta