What is so special about Inverter type Air Conditioners….

Have you ever tried hiding the remote controller of the air conditioner simply to get rid of the extensive current bill? If so, inverter type air conditioners are just the thing for you!

This particular strategy of energy saving is suggested in a popular TV advertisement, nowadays. As it suggests, with this inverter type air conditioners energy saving up to 60% can be expected.  Therefore, it is worth to have a look, how this new phase of technology accounts for the energy efficiency and the performance of the air conditioners.

The basic operation of the air conditioners is to extract the heat energy from a compartment area and release it to the outer environment.Therefore, when maintaining the air conditioned space, at a lower temperature, air conditioner has to extract heat energy from a lower temperature medium, and release it to a higher temperature medium. From the second law of thermodynamics (Clausius statement), for this to happen, there should be some external work done somewhere in the cycle. The work needed for this thermodynamic cycle is done by the compressor of the air conditioner.

Operation principle schematic

Thermodynamic cycle in Air conditioners

The point of the cycle, where air conditioning can be easily controlled, is the compressor motor.  In conventional air conditioners, on off control of compressor is used to maintain the temperature of the air conditioned space around the set value. That is, if the temperature of the room is below the ‘set value-some tolerance’, compressor will completely turn off, whereas if the room temperature rises above the ‘set value + some tolerance’, compressor will completely turn on. A dead band is there to avoid rapid fluctuations of the response around the set point, which would occur otherwise.

On- Off control operation

In inverter type air conditioners, in contrast, the conventional on- off type control is replaced with a wide range of speed control technology. That is, with this new technology, the speed controlling of the compressor is possible rather than just turning on and off. To control the speed of the compressor motor (which is an induction motor), over a wide range, a variable frequency motor drive is used.

Control block diagram of the compressor

Operation block diagram of the inverter

At stating of the air conditioner powerful cooling is required to reach the set temperature.When the set temperature is reached,only a little power is sufficient to maintain the achieved temperature when it comes to inverter type air conditioners. This is achieved by controlling the compressor speed. In contrast, with conventional air conditioners, only the on-off control of high the speed compressor is possible.That in turn results in large fluctuations of temperature.Subsequently this leads to a wasteful consumption of energy.

How much of this wasted energy you can save by replacing the old air conditioner with an inverter type one mainly depends on the factors such as, environmental conditions, thermal insulation of the compartment area, set temperature, rate of change of the room conditions, etc. 

Another major plus point with inverter type air conditioners, over the conventional type is its ability to reach the set temperature smoothly and quickly. And also it is capable of maintaining the air conditioned space around the set temperature with a lower tolerance. Due to more precise temperature control, enhanced room comfort can be expected. 

With the conventional type air conditioners, sharp fluctuations of voltage which would disturb the other electricity consumers and appliances could occur due to frequent on/off of the compressor. But with inverter type air conditioners, that issue is completely eliminated.

Anyway, with the added complexity due to the introduction of power electronics, production cost tends to increase proportionately. Moreover repairing and troubleshooting of this new inverter, is neither simple nor easy as it is with the conventional one.

Whether you like it or not, conventional air conditioners are now being rapidly replaced by this newly introduced member!

References:

http://www.airintelligence.co.uk/cooling-air-conditioners/  

http://slideplayer.us/slide/245200/

Article By: Thisandu Kahingala 

Read more »

Posted in: Utility and Social