Energy Savings in Air Compressor | Innovative Inlet Air Pre-Cooling

Compressed air is one of the costliest utility in any industry. Out of 100%, electrical input energy given only around 10% will be a useful output and rest everything goes out as waste heat, noise and friction. This number is enough to think in a more focused way to check for possible energy saving opportunities. There are many energy-saving opportunities like pressure reduction, leakage arresting, capacity control through speed regulation, avoiding misuse of compressed air and all that can have significant potential.

Apart from these, there are some energy-saving potential through inlet air pre-cooling. As per BEE's thumb-rule: every 4 °C rise in temperature results in higher energy consumption by 1% for providing equivalent air output. For example, Inlet air to a compressor at some 10 °C would deliver a relative air output of 102% compared to that of 15 °C inlet air henceforth saving around 1.4% of power consumption.

Practical Constraint:  

We know that decent energy saving potential is available through reducing inlet air temperature but still this project is practically not seen implemented widely. Due to reduced air temperatures, air density gets increased resulting in the suction of more volume of air thus providing relatively higher CFM output. But the amount of energy saved when compared to that of energy consumed in reducing the air inlet temperature through conventional cooling methods is relatively far less. But with the advent of low and alternative cooling technologies available, relooking in implementing this energy-saving project seems to be worthy.

Can IDEC be a probable solution for this:

IDEC - Indirect evaporative cooling is a recent advancement in alternate cooling technologies where the required cooling levels can be obtained (some times less than wet-bulb temperatures) with the help of the innovative adiabatic cooling principle where in the air is cooled indirectly with water thus providing sensible cooling. This involves just innovative heat exchangers and water spraying mechanism providing the required cooling effect. 

On the numbers, kW/TR for IDEC is around 0.2 whereas the same for conventional vapor compression air conditioning systems is around 0.55 - 0.75. So at much lower energy consumption per TR of air cooling the net energy savings in compressed air system through inlet air temperature reduction seems to be attractive. In some cases using a hybrid model like pre-cooling the air initially with idec and later cooled further using chilled water coil can also be done for optimal results.

Hope these kind of innovative technologies gets accelerated implementation in near future.