Being effective with the term efficiency

There is a whole minefield strewn across the word efficiency.

That's forgivable, because it's a powerful concept and a powerful word.

Fundamentally it's tied up in how much we put into something to derive a certain amount of something we get out. Importantly that's a bit different from being effective, which depends on whether what we get out does the job we want. Throwing a net into a school of fish might be an efficient way of fishing. It is not effective as a way to make camembert. So, I illustrate with the ridiculous, but you get the point. There are other things that can matter just as much, or even more, than efficiency - depending on how we define it.

Given the very generic nature of efficiency, it is important to be careful in how we define it in any specific context. It is all too easy to end up comparing apples with oranges because we have assumed the word efficiency means the same thing in different contexts, when it may not. Sometimes different types of what is "an" efficiency are given various jargon terms to confuse even further.

The other important thing to note, is that efficiency only matters if there are constraints in how much we can put in. If we have income of X, we will probably be far more concerned with using every cent to maximum effect than if we have income of 5000X. There are few things that have no constraint, so always typically, efficiency is of some interest, even for those earning 5000X - but for some things it matters way more than others. Things that can be exhausted give us far greater incentive to be efficient that those which will pop into being anew with the next sunrise.

So when we look at energy, there will be some initial process which takes an energy source and puts it in some initial energy "lego brick" form that can be moved around to a user. That process will have some efficiency. Yet, it is interesting to reflect that the importance of this efficiency depends to some extent on how "constrained" that source is. If it is something that our supply will eventually run out of, we worry about this efficiency a lot more than if the supply will pop up again anew with the sunrise, or with some other event, that might be unpredictable precisely in when it comes, but will come around eventually. But then that problem is also a function of how efficiently we are able to store energy and/or how efficiently we are able to transmit it to/from afar.

However, we should not also forget that there is another efficiency which relates to the energy involved in making all the kit required for that process. Converting some energy sources into that "lego brick" (and/or things that can use it) takes a whole lot more kit than others. And also the process of replacing that kit and recycling or disposing of any of its waste at the end of life. That includes any things we are depending on for transmission or storage. How much material from one generation of usage can be propagated into a new generation is also another kind of efficiency. One rarely considered but quite important.

Also, there is the efficiency of space or volume used. If we live in the vast tracts of Siberia this might matter less to us than if we are in downtown Hong Kong. How much space or simply how much stuff we need to do our energy is another important input. That can be especially important if we want to use our energy to move things around and being light or small will make that easier. This isn't usually described as an efficiency, but it is one. Similarly we can think of efficiency with time. Something might be very efficient in energy out terms, but if it takes three million years for the process to run, we are missing something.

Whatever the case, returning to the more common energy context, once energy is in that "lego brick" form, it is actually transported to the user. That distribution process has losses so it will have another efficiency. This efficiency is often pretty good. We are getting better at moving energy around with fewer losses.

Ironically we sometimes describe this energy transported to the user as final energy, but it is a bit of a misnomer, because the really important efficiency is the next and truly ultimate stage of how much useful work energy the user is able to get out of the energy delivered to them. That will vary with every individual machine or process, so it is never really measured exactly (who could), just at best estimated. However the so called “final” energy transported to the user before use in some "lego-brick" form is of note, because it is the last stage we can really count semi-accurately at some kind of audited national level.?

The problem is, we can mix and match all these different efficiencies at different stages, to give different multiplicative combined total efficiencies from different combinations of stages.? If we don’t think about it, or attempt to resolve it carefully, it can be oh so easy to compare things that combine different stages, or include ones that aren’t really relevant to the discussion taking place.?

I don’t say this from an accusatory point of view, but as one who has had the eyebrows singed by efficiency error explosions on several occasions, thankfully mostly by my own realisation before plunging in too deeply publicly, but even now, I try hard, warily, get my head around these things.? If we are not sometimes confused by these things, we probably aren't thinking about it hard enough. If you are one of those rare geniuses to whom it all comes naturally and instantly, forgive me for saying so.

So the point?? Simply, if you hear the word efficiency, try to know precisely what is meant by it in the instance quoted.? That might not be quite as straightforward as imagined, depending on how many steps are involved.? If we are comparing efficiencies of things, we need to take great care to compare like with like, and to use the efficiencies that are most relevant to the question we are trying to answer. It's not always a foregone conclusion that we are.

If I have confused, then I don't automatically apologise for that, because to feel confused over something with complexity is a better state of affairs than to misguidedly think it simple.