Flying blind takes no skill but is hazardous. John Thompson* offers an invitation for manufacturers to put their fingers on the pulse re energy consumption and costs.
COSTING the electrical energy losses in industrial installations is a smart idea.
There are three main reasons:
One, it provides a cost reference for future improvements and permits payback calculations on new investments;
Two, you are able to identify high consumption loads and therefore look at reducing your energy consumption; and
Three, by reducing energy loss your business becomes greener.
Depending on business costing policies, energy consumption may be considered as fixed, or fixed plus variable.
The latter is of course only possible if there is in-plant metering installed.
This article focuses in particular on transformers, switchboards, busbars and cabling, as well as motor-driven production equipment.
Electric motor efficiency is very important!
Rather than replacing a motor that has blown up or worn out with the same rating, or looking for a cheaper alternative, modern, high efficiency motors can have pay-back periods as short as seven months.
The savings occur in reduced electricity consumption as motors, over their practical life, usually consume far more dollars in energy than their acquisition cost.
For detailed analyses visit www.copper.org/applications/electrical/energy/sys_motor.html.
Because electrical installations are usually not reviewed unless there is a major breakdown, there are many instances where excess energy usage is undetected.
There are great advantages in monitoring, on a continuous basis, the energy consumption (as well as other electrical parameters) of important parts of the production plant in order to allocate direct costs (DIN-rail mounted meters).
Individual metering can indicate incipient problems, thus avoiding sudden interruptions to the production line.
Switchboards, Busbars and Wiring
The more physically extensive the production plant is the more severe electrical energy losses become.
The use of power electronics (induction heaters, electroplating, welding robots, palletising and conveyor lines, etc) entails disproportionate energy losses in the factory electrical distribution cabling.
This is caused by ‘harmonics’, which can cause additional current load between 40% and 100% (technical information will be found at www.copper.org/applications/electrical/pq/issues.html and useful basic information at www.rose-hulman.edu/class/ee/HTML/ECE471/PDFs/Lect15.pdf).
Reduction of harmonics can be achieved through the use of modern, active filters.
By grouping harmonics-causing equipment in a circuit with a harmonics filter in its input, a highly cost-effective energy conservation measure is made.
In larger factories with a substation transformer, the pay-off is in more reliable and cooler transformer operation–and the spare capacity for factory expansion made available by ‘unloading’ the harmonics components before they affect the transformer.
The first thing here to consider is your electricity bill as to which tariffs are applied.
In addition to kilowatt-hours, you may also be charged a maximum demand in kilovolt-amps (kVA).
So far energy loss (in kilowatt-hours) has been the main subject.
Many industrial installations have a large kVA demand compared to the useful power required (kilowatts) and pay more as a result.
Power factor connect the two and is the ratio of kilowatts to kilovolt-amps.
Active power factor correction, which reduces the kVA, can also be a part of harmonics filtering mentioned above.
For kVA demand installations there is, as a rule, a very short payback period for power factor correction equipment through the reduction in demand tariff charges.
Finger on the Pulse
To test the electrical health of your plant, an analysis must be made using instrumentation such as a power line analyzer with harmonics analysis capability.
Such equipment can be rented, purchased or a suitable consultant can be engaged.
There is considerable value, though, in building up your own capability because it allows regular review and therefore timely intervention.
Cost accounting for production processes is as good as the input data. Allocation of electrical energy costs can be critical in the P&L.
Individual machine energy usage provides transparency as well the onset of problems through increased consumption.
In this time of focus on energy conservation and reduction of greenhouse gas emission, knowing what is going on electricity consumption-wise in your factory is highly desirable for you and the bottom line.
* John Thompson is Managing Director of Westek Electronics 03 9369 8802, www.westek.com.au.