Friday, 8 March 2013

Can Power be Consumed?

I may be being pedantic, but a phrase commonly seen in the media, and also in scientific journals is ‘power consumption’.

Can we consume power, or is power a means of creating energy (and vice-versa)?

In other words, should the correct phrase strictly be ‘energy consumption’.

Your advice sought.


  1. To my knowledge power is the rate of doing work while energy can be potential energy [the capacity of doing work] or kinetic energy [KE = 1/2 mv raised to the power 2. So I think "power consumption" is correct.
    Fathi Habashi , Laval University, Canada

  2. I take it that you are going back to definitions where power is the rate of doing work and energy is what is used to perform the work. So from that point you do not consume power, but rather consume energy to generate power.
    M. C. (Mike) Albrecht, USA (via LinkedIn)

  3. No, power cannot be consumed. However to speak of power consumption is perfectly legitimate, both scientifically and semantically. In this instance "consumption" implies a rate.

    Our perception of power is confused by using, in most engineering applications, a unit for power rather than for energy. Thus we use "watt" for power and, by integrating with respect to time, we have "watt hour" as a unit of energy. This is a bit like having a fundamental unit for velocity - lets say "horse" - which would mean that distance would be measured in horse seconds!

    This is all more easily understood if we shift to SI units. Energy, in Joules, can be consumed. Power, in Joules per second, cannot be consumed because it is an instantaneous rate. Power consumption is simply the rate at which energy is being consumed.

    John Rayner, Australia, via LinkedIn Minerals Engineers

  4. Still not quite clear. Is kWh/tonne power or energy consumption?

    1. kWhr is a measure of energy. A kilowatt hour, the amount of energy when a kilowatt of power is delivered for one hour, is 3.6MJ (because a watt is 1J/s). So kWhr/t, like J/t, is a measure of energy consumption.
      John Rayner, Australia

  5. We may say"power required" to do a particular operation.
    T.C.Rao, India

  6. Power is certainly the biggest limiting factor to modern civilisation. If we look at at a process like comminution then it is easy to determine the energy that is required to reduce a rock to a given size. In many cases though that energy could, in theory, be provided by a single person with a decent hammer and a suitable length of time.

    It's that time that is key, since obviously in many cases people are not prepared to wait years (or more) for a given outcome - something which does not appear to have been an issue in creating many of the "wonders" of ancient civilisation. In creating a need to produce a desired result within a narrow time range, like crushing X tonnes of rock per hour, modern society has created an ever greater need for power rather than energy.

    So in short although the pyramids of Egypt may have required substantial energy to create, that amount of energy is trivial compared to what is expended every day in modern society. It has been this increase in power, or the rate at which energy can be used, that has driven modern civilisation - and will also inevitably provide a limitation on the rate at which civilisation can expand (unless technology, and resources, is able to keep up with demand). Ultimately it's fossil fuels, in particular oil, that we have to thank (or blame), so it remains to be seen whether other energy sources are capable of providing the power that modern society increasingly craves.

    James Rowe, Australia, via LinkedIn Minerals Engineers

  7. Power is like the CC of the engine of your car, and energy is the fuel consumption. Fuel consumption does depend on the road you take (ore hardness). Yes, power consumption is not the right expression, but often it is used as if it means power utilisation. The installed power is a capital cost and energy is an operational cost. The more capital upfront, the more powerful your mill will be which might (if you are a good driver) result in energy eficiency. Good issue Barry. It seems to be a common misunderstanding that low power utilisation is good.

    Romke Kuyvenhoven, Gecamin, Chile via LinkedIn Minerals Engineers

    1. I think your explanations sums it up perfectly Romke. Thanks

  8. "In the initial post that posed the question, MEI commented on being "pedantic" and then wondered whether the proper term is "energy consumption."

    "I don't wish to be overly pedantic, myself, but the First Law of Thermodynamics states that energy can be neither created nor destroyed. Consumption implies destruction. Energy is not, per se, consumed; it merely changes state or is transferred. But that is being hyper-technical. From the point of view of the non-engineer or non-physicist, energy does appear to be consumed in the same way that, say, water is "consumed" by users, even though matter, like energy, can be neither created nor destroyed.

    "Just as we can measure water in terms of liters, we can measure energy in terms of joules. And power is the rate at which we "consume" the energy. It's measured in joules per second, which is also known as the Watt. Curiously, we sometimes see energy expressed in watt-seconds, which is just another way of saying joules! On your electric bill, it will be in kW-hrs, so you are being charged for the amount of energy you are using -- or consuming. (One kW-hr is about 3.6 million joules.)"

    Joe Lombardi
    Toms River, NJ, USA


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