Improve your motor power efficiency.
Opportunities to enhance the efficiency and economy of the motor power you use:
- Go for a high standard – motors are generally pretty efficient devices (85% to 95% in most cases), but as their power to cost ratio is high, choosing a higher standard of motor that offers better performance can pay back very quickly.
- Avoid motor rewinds – though it might seem environmentally friendly to have a motor rewound rather than throw it away and buy a new one, efficiency is lost in the rewind process and newer motor designs are invariably better than the original unit. So buy new.
- Variable speed drives – most motors are fixed speed devices, which is fine if that’s all you want. But for uses like pumping and ventilation, you can benefit from variable output. VSDs (or inverters) let you do this. With many applications power is proportional to the cube of the motor speed – so drop the motor speed by 20% and your power consumption falls by almost 50%1.
- Link motor speed to your required output – if you do choose to go with variable speed drives, you can go optimise motor performance by aligning the speed to your required output dynamically. So, for instance, in an irrigation system that is required to give variable water volumes, a pressure sensor can modulate the pump speed to ensure water is delivered at a constant pressure. So when the irrigator stops, the motor slows to almost standstill.
1 Figures taken from the Carbon Trust: Variable Speed Drives.