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What is the correct wording to use in a formal paper, "power consumption" or "energy consumption" for an industrial machine?

I totally understand the practical difference between power and energy, but this is a question I never got a definitive answer for, no matter how many experts I have asked. I personally lean towards the later.

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  • \$\begingroup\$ Power in this case means electricity not energy consumption rate. \$\endgroup\$ – user3528438 Sep 29 '17 at 22:59
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    \$\begingroup\$ I'm probably not qualified to answer this, but I'd say it depends on context. If you are talking about a total amount of energy for a given amount of time, then energy. If you are talking about a rate of consumption for an unspecified amount of time, then power. \$\endgroup\$ – Wesley Lee Sep 29 '17 at 22:59
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    \$\begingroup\$ Context required. Both make sense. If the machine makes a car, you can talk about the "energy consumption" for making the car. You don't really care if it takes a lot of power and delivers a car a minute later, or if it uses very little power and takes all week. But if the machine runs continuously you want to know its power consumption. \$\endgroup\$ – Brian Drummond Sep 29 '17 at 23:00
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    \$\begingroup\$ Energy cost is the preferred unit in Watt-hrs for average utilization for electricity or MPG, L/100km for gasoline or.... Power is preferred when peak work load is defined in kW, Hp, BTU or whatever industry it belongs with. It depends if you are referring to capacity or usage or cost or whatever is relevant. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Sep 29 '17 at 23:04
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    \$\begingroup\$ Energy consumption must be qualified by specifying the time interval. \$\endgroup\$ – Chu Sep 29 '17 at 23:07
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Once it is understood that power is the rate of energy consumption (which you say you do), then use of either term in a paper is very much driven by the context.

When talking very informally, the terms are often used interchangeably, however incorrect that is.

When talking formally, you'd use one or the other, depending on what what important.

For a paper on a hydro-power power installation. The size of the lake is related to the energy consumption of the town it serves. The size of the generators and transmission lines is related to the peak power consumption.

For a paper on an industrial machine it's a little more difficult, and depends on the duty cycle of the machine. The size of the switch-board, fuses and transmission lines to it depend on the peak power consumption of the machine. The running costs per year depend on the energy consumption over that period, so how many hours per day it's in use, and at what fraction of maximum capacity. If it's a water pump that operates at constant flow 24/7, then the relationship between the two is very simple.

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What is the correct wording to use in a formal paper, "power consumption" or "energy consumption" for an industrial machine?

I would normally say "power demand" in preference to power consumption as it carries the implication that the supply system has to be capable of supplying that power while the equipment is running.

"Energy consumption" is in general use and refers to the total energy used over a period of a day, week, month or year.

For an industrial user both power and energy consumption are important.

  • The power demand will determine the required supply infrastructure, contracted supply and fusing.
  • The energy consumption will be the number of electrical "units" consumed in a time period. This is the integral of power over time.

Energy (J) = Power (W) x Time (s).

Electricity usage is charged by the kilowatt-hour (kWh). 1 kWh = 1000 W x 3600 s = 3600 kJ.

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  • \$\begingroup\$ 3600 kJ not MJ. \$\endgroup\$ – Oskar Skog Sep 30 '17 at 6:01
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The usage very much depends on context. If the power usage is constant over time, it doesn't make much difference whether you refer to power or energy in most contexts. If the load or duty cycle changes, it would be better to discuss energy use rather than power. In a situation where one machine is less efficient but can accomplish the same task in less time than an alternative, it is necessary to compare based on energy required to complete the task rather than power required to operate the machine.

The bottom line is that discussing either power or energy can be accurate and useful, but it is easy for an article to be inaccurate or misleading if the choice of parameters and complete presentation is not carefully done.

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Think Power as the speed how fast the energy is consumed. Power 1 watt means one joule energy per second.

Power consumption is established term and people understand it mean the power which a device or system takes.

Energy consumption is also ok term, but it means how much energy is consumed in some time interval or between starting and finishing some job.

Comparison: One can say A has smaller energy consumption than B. That means: At the same time interval or to get the same job done B consumes more energy than A.

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Power is an instantaneous value. Energy is power across time. Think of kW (power) vs kWh (energy)

1kW of power for 1 millionth of a second is very little energy. .0000001kW of power over a million years is a LOT of energy.

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  • \$\begingroup\$ Sure, but how does this answer the question? \$\endgroup\$ – DimP Sep 30 '17 at 0:04
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You are almost certainly looking for "energy consumption."

Power is the rate that energy is consumed. However, the phrase is "energy consumption" because energy is a conserved value, so you can actually take it away from somewhere else. Power is not conserved, so the implications of "consumption" are hard to apply to it.

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Both expressions can be used appropriately in a technical context. If they are really appropriate to the context, that is the question.

Of course you must use these expressions in a context where it is absolutely clear that you are aware that "consumption" is taken from engineering jargon and you know that energy cannot be really consumed, but only converted in other forms.

The same applies to power, since it is the rate of energy conversion ("consumption"), and the physical principle of conservation of energy applies always (at any time instant).

Assuming your audience is well aware that you know what you mean by saying "consumption", then sometimes it is equivalent to either say power or energy, because you just want to emphasize that some energy is "used-up" to do something, without particular interest on the difference between the two quantities (e.g. you might want to express that some machinery consumes lots of power/energy, without focusing on the details).

In some other context, you must be precise and specify energy or power according to what you want to express. For example, if you are computing the maximum power that a particular power line can deliver to a load, you can say that a load is particularly power-hungry by saying "it consumes a lots of power", or "it consumes 1000W (of power)"; talking about how much energy it consumes will sound strange in this case.

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