add `energy service`

[stap-m]

          I've not followed this discussion closely, but the concept of an `energy service` has been around for at least thirty years.  Please see:

• Groscurth, Helmuth-M, Thomas Bruckner, and Reiner Kümmel (1995). "Modeling of energy-services supply systems". Energy. 20 (9): 941–958. doi:10.1016/0360-5442(95)00067-Q.

That paper essentially describes an early energy systems ontology. And I do suggest a quick skim for an historical perspective.

Energy services are defined thus in the introduction: "energy services are the ends for which the energy system provides the means".

So that is quite general. I will add that specific energy services are usually specified using intensive variables: air temperature, speed over land, illumination level (technically luminance), and so on. So I think that aspect is quite important. More on Wikipedia:

• https://en.wikipedia.org/wiki/Intensive_and_extensive_properties

I am not sure what the equivalent metric for a hair cut would be: relative removed mass of hair?

Incidentally, that cited paper underpinned the deeco framework, now archived here on GitHub:

• https://github.com/robbiemorrison/deeco

Originally posted by @robbiemorrison in https://github.com/OpenEnergyPlatform/ontology/issues/1514#issuecomment-1835993902

[l-emele]

I am not sure what the equivalent metric for a hair cut would be: relative removed mass of hair?

As first approximation, I would argue that the energy service is independent from the length of the removed hair. However the hair cut involves a lot of other subprocesses that has each it own energy service (e.g. the hair salon needs illumination, the hair drier increases temperature...).