Performance, Precision, Partnership

What is Your Air Compressor’s Specific Power? Get more output, use less energy, lower your costs

The energy efficiency rating of a compressor is called Specific Power – the lower it is, the more you save in energy and money

What is Specific Power?

Specific Power is the ratio of total energy used by the compressor and its compressed air output (at a stated pressure).

The lower the Specific Power of your compressor, the greater the efficiency, and the higher the energy and money savings.

The total energy used by the compressor is the total power input at the maximum stated pressure, and includes the main motor, fan motor(s) and their efficiencies, and any other compressor power requirements. Specific Power should not be based upon shaft power as this excludes the power requirements of other components within the compressor.

The compressed air output typically described as Free Air Delivery, is the compressed air volume at the outlet of the compressor package at atmospheric pressure.

How is Specific Power Calculated?

The Specific Power of a compressor is the energy used divided by the compressed air output.

Using this calculation, we can see that HPC’s SM13 Rotary Screw Compressor, Specific Power is 6.4 KW/m3/min.

Energy Used ÷ Compressed Air Output = Specific Power

8.56kW ÷ 1.33m³/min = 6.4 KW/m3/min

Equivalent non-HPC compressors are typically less energy efficient with a higher Specific Power, in excess of 7.0 KW/m3/min.

How Does This Save You Money?

The achievable cost saving can be calculated by multiplying the Specific Power, by the total volume of compressed air, by the cost per kWh, like so:

Specific Power x Total Volume Compressed Air x Cost Per kWh = £

This means that investing in a compressor from HPC saves you money in the long-term. Many other brand manufacturers entice customers on the pretext of cheaper priced compressors. While this may offer an initial outlay saving, you will end up paying many times more over this difference in unnecessary energy costs. With further increases in energy costs on the horizon, reducing energy bills is more important now than ever.

HPC saves customers up to £25,000 in electricity costs per year.

Here are some examples of HPC energy cost savings per year versus equivalent non-HPC compressors, based upon 2000 hours (single shift operation):

Fixed Speed Vs Variable Speed Drive Compressors

With fixed speed rotary screw compressors, the Specific Power stays fixed. However, as Variable Speed Drive Rotary Screw Compressors (VSD) operate at different speeds, the Specific Power changes, too.

Why is this? There are two key factors:

  • The motor is typically designed to run at a constant fixed speed of 3000rpm, and at its optimum efficiency. However, running below and above this speed, will reduce its efficiency.
  • The Airend – which produces the compressed air – is also typically designed to run at a constant fixed speed, and at its optimum efficiency. Likewise, running below and above this speed, will make it less efficient.

When operating at varying speeds, the efficiency changes. HPC’s VSD Compressors still rate higher in energy efficiency (Specific Power), compared to equivalent non-HPC VSD compressors.

The HPC ASD 40 SFC Compressor has a peak Specific Power of 5.9, versus the same sized Non-HPC Compressor which has a peak Specific Power of 7.3. This makes the HPC ASD 40 SFC significantly more energy efficient.

The HPC ASD 40 SFC Compressor also has a greater free air delivery range from 1m³/min to 4.5m³/min, versus the non-HPC compressor with a range of 1.5m³/min to 3.5m³/min. The HPC compressor will be more efficient in this range to meet the customer’s own varying compressed air demand. 

HPC KAESER Strategy: “More Air, Less Energy”

HPC compressors are designed without compromise to ensure they have the best Specific Power so customers can save on energy costs. This means the compressor’s complete package is considered and includes:

  • The most efficient motors.
  • A large range of KAESER Sigma Airends that are sized to perfectly match the motor to produce the optimum output at the highest efficiency.
  • The lowest internal pressure drops throughout the compressor, limiting energy losses.
  • The lowest operating compressor temperatures, from the inlet of the compressor, through energy efficient cooling fans, optimum sized coolers, and excellent energy temperature control. The lower the operating temperature, the greater the efficiency.

If you are in the process of looking for a compressed air solution, ask for the manufacturer’s technical data sheet, which should detail, pressure, flow, and input power. Then speak to an HPC Authorised Distributor or contact HPC directly. We will show you how choosing HPC can save you money and turn your operation greener. Go Yellow, Be Green, Save Money.