An investigation into the efficiency and embodied energy of electric motors for use in pumping
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Date
2011-10-19
Authors
Smythe, Clinton
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Abstract
This research report is separated into two sections. The rst section covers the
embodied energy which is required to manufacture a new electric motor. It takes
into account the energy required to mine, transport and process all raw materials, as
well as the energy used by the factory to turn the raw materials into a motor. The
second section investigates the actual e ciency of a pumping system under various
operating conditions, these include changing the static head, changing the throttling
of a valve, and changing the supply frequency. Two 0.37 kW induction motors are
used, an energy e cient motor and a standard motor. The di erences in e ciency
between two motors is compared under each of the di erent test conditions. The
analysis is also taken a step further as the e ciency of each of the subsystems is
investigated in isolation, rather than simply looking at the overall e ciency of the
system. This provided valuable information about how the system could be made
more e cient, as well as an understanding as to where the losses in the system occur.
Finally the two sections are combined so that one is able to decide whether it is
worth upgrading to a new more e cient motor or stick with the existing motor.
Although there may be e ciency improvements by using the new motor, there is
also an upfront embodied energy which was required to manufacture the motor. The
two pieces of information will give a payback period, if the motor is operated less
than the payback period then more energy is in fact used to manufacture the motor than the motor actually saves due to improved e ciency.