Energy Saving
Did you know that 80% of an industrial screw air compressor’s purchase cost is spent on electricity to run it? We are experts in supplying Energy Efficient Screw Air Compressors.
If your current compressor is oversized or you have a process where the air demand varies, then considerable savings could be made by installing a VSD (Variable Speed Drive) compressor.
Let’s take a look at the advantages an SCR Variable Speed Drive Screw Compressor can offer:
Energy saving
Energy Savings of 30% can typically be gained, but energy savings as high as 50% are not uncommon on an oversized screw air compressor. A Variable Speed Drive (VSD) has the ability to vary the output speed of the compressor’s airend depending on the actual pressure in the system. The net result of this means that when air demand is low, the speed of the compressor is reduced, but when the air demand is high the compressor runs at full speed. One of the benefits of a Variable Speed screw compressor is that it stops the compressor ‘unloading’ when the air demand is low, unlike a fixed speed machine which will vent unused air to atmosphere when not required. Venting unused air to atmosphere is a particularly wasteful method of flow control when compared to a VSD screw compressor which backs off the speed when demand is low, therefore saving energy. On a constant torque application such as a screw compressor, power is proportional to speed. For example if the screw compressor is loaded but the air demand is low and running at 50% speed, the energy savings will be 50%.
Dynamic pressure control
Because a VSD compressor offers dynamic pressure control, it is capable of maintaining a smooth and stable pressure when compared to the ‘on-off’ load control of a fixed speed machine. A VSD screw compressor can typically maintain pressure to within +/- 0.1 Bar while fixed speed compressors can typically hold pressure to within 0.5 bar. As the air pressure is controlled much more tightly on a VSD screw compressor, a small reduction of the pressure set point is often possible, which again offers additional savings over a fixed speed machine. In addition a 0.3 bar reduction in pressure will also reduce air leakages by around 4%.
Pure soft start capability
Typically a Variable Speed Screw Air Compressor will maintain Full Load Current (FLC) on start up within 1-2 times of the nominal rated motor current. This method of starting a motor offers the purest form of soft start. Even a dedicated soft start unit can only maintain FLC on start up within 3-4 times of the motors nominal current. Compare this to a standard Star Delta starter which maintains FLC on start up between 7-8 times and you can see the benefit an SCR Variable Speed screw compressor can offer. This pure soft start means reduced mechanical stress on belts, couplings and gearboxes, as well as increasing the reliability of the screw air compressor. It can also help keep the sites electrical peak demand to a minimum when starting the compressor
Intelligent motor protection
A Variable Speed Drive offers improved protection of the compressors main motor over a traditional thermal overload. A modern VSD can sense a number of faults within the motor such as Overcurrent Faults, Earth Faults and Short Circuit faults. This enhanced level of motor protection can help reduce costly motor repairs. On board drive diagnostics help reduce down time and fault finding.
Improved power factor
Installing a VSD Compressor can help lift the sites Power Factor due to the internal capacitance within the VSD itself.
Would I benefit from a Variable Speed Drive Screw Compressor?
If your current compressor is oversized or you have a process where the air demand varies, then considerable savings could be made by installing a VSD compressor.
In some cases this may be a standalone single compressor system or part of a system where a number of compressors are all supplying air to the same network. Usually only one VSD compressor is required, with the fixed speed machines providing the base load and the VSD compressor acting as the ‘top up’ machine.
The simplest way to see the energy saving benefits is to compare your running hours with the load hours. If for example the annual run hours are 8000 hours and the load hours are 4000 your compressor is spending half of it’s time consuming energy but without making any air! These off load costs can be around 20-30% of your compressor motors full power!
To find out how much an SCR Variable Speed Screw Compressor could save, please use our energy saving calculator.
You only have to input the following details to see how much you could save on with a Reliable Industrial Air Screw Compressor.
- Motor size in kW – This can usually be found on the data plate on the side of the compressor. This data can also be found on the motor nameplate.
- Annual Running Hours – This data can be found either on an a mechanical hours run counter or by accessing the data on your digital compressor controller. If your machine is for example 5 years old, simply divide the total run hours by the number of years the compressor has been operating to arrive at your annual operating hours.
- Annual Off Load hours – As with the annual running hours, this figure can be taken from the on load hours counter or by accessing the on load hours figure on your digital compressor controller. Alternatively, count the number of times the compressor unloads over a 15 minute period during production hours.
- kWh rate. This is the current cost of your electricity. If you have a different day & night rate and the compressor runs continuously then you can use an average figure. If you don’t know your current cost, you can use the default value of 0.11p.
There are two savings shown on the calculator once the data has been entered. Unloaded energy savings along with the additional savings that would be gained by tighter pressure control.
For an Energy Efficient Screw Air Compressor please see our Variable Speed overview brochure for further information.
