Specific Power: How Energy-Efficient is Your Compressor?
Key points
With the acute and runaway increase in the cost of energy, today's manufacturing and business environments need to be savvy about reducing energy costs in order to survive.
Facility engineers are charged, therefore, with getting the maximum possible efficiency out of their consumption of energy and extracting every ounce of output possible from each kilowatt hour they pay for and consume.
Compressors & Energy Use
Compressed air systems have traditionally been among the most prominent components of industrial energy consumption. In fact, over 10% of total UK industry consumption is estimated to be accounted for by air compressors. Switching to the most energy-efficient air compressors available, however, can reduce both energy use and costs. It is necessary in order to determine the most efficient compressors available today to know about Specific Power.
What Is Specific Power?
Specific Power is a proportion of total energy used by the compressor to its output of compressed air (given pressure). The lower the Specific Power of a compressor, the greater the efficiency and the more energy and cost savings.
The entire energy absorbed by the compressor consists of the main motor, fan motor(s) and efficiencies, and any additional requirements of compressor power. Free Air Delivery at the discharge point of the compressor package at the ambient pressure is what is loosely referred to as Free Air Delivery.
How Is Specific Power Calculated?
The Specific Power of a compressor is calculated by dividing the energy used by the output of compressed air.
Using this calculation, we can deduce that the HPC KAESER ASD40 7.5 bar rotary screw compressor has a Specific Power of 5.92 kW/m³/min: 23.2kW (Energy Used) ÷ 3.92m³/min (Compressed Air Output) = 5.92 kW/m³/min (Specific Power) Similar non-HPC compressors are typically less energy efficient with a higher Specific Power of over 7.0 kW/m³/min.
How Does This Save Money?
Cost savings can be calculated by multiplying the Specific Power by the total volume of compressed air and cost per kWh. Taking a two-shift operation as an example where compressed air is needed for 4,000 hours per annum, we can estimate the costs of compressed air for a non-HPC equivalent compressor:
7.19kW/m³/min (Specific Power) x 4,000 hours x 3.65m³ (Total Volume Compressed Air) x £0.30/kWh (Cost Per kWh) = £31,492 (Costs Per Annum)
Compared with the ASD40, which would need to operate only 3,725 hours to produce the same volume of compressed air:
5.92kW/m³/min (Specific Power) x 3,725 hours x 3.92m³ (Total Volume Compressed Air) x £0.30/kWh (Cost Per kWh) = £25,933 (Costs Per Annum)
HPC saves £5,559 per annum.
It costs money to buy an HPC KAESER energy-saving compressor, with industry-leading Specific Power and shorter operating time, but it saves money in the long term.
In fact, we save our customers £25,000 or more annually.
| HPC Model (7 Bar) | HPC Specific Power kW/m³/min | Equivalent Non-HPC Specific Power kW/m³/min | Savings Per Year With HPC |
|---|---|---|---|
| SM13 7.5kW | 6.44 | 7.5 | £825 |
| SK22 11kW | 6.52 | 7.5 | £1,064 |
| SK25 15kW | 6.57 | 7.5 | £1,663 |
| ASK34 18.5kW | 6.35 | 7.5 | £2,456 |
| BSD65 30kW | 5.95 | 7 | £3,464 |
| CSD85 45kW | 5.78 | 7 | £6,239 |
| CSD105 55kW | 5.87 | 7 | £8,134 |
| CSD125 75kW | 5.96 | 7 | £8,592 |
| DSD175 90kW | 5.40 | 7 | £19,752 |
| DSD240 132kW | 5.49 | 7 | £25,463 |
Fig 1. Examples of energy cost savings based on 2,000 hours (single-shift operation)
Many other brand producers entice purchasers with the idea of lower-cost compressors. While this can offer a saving initially, purchasers will end up paying much higher unnecessary energy costs in the long term. With impending future increases in the cost of energy, keeping energy bills down is more important than ever before.
HPC KAESER Sustainability Discounts
Until 31st May, HPC is offering Sustainability Discounts on all its range of energy-efficient belt-driven rotary screw compressors, KRYOSEC dryers and filters.
To find out more, visit: www.hpcplc.co.uk/sustainability or contact HPC on offers@hpcplc.co.uk.
