Ontology: we have to distinguish between primary/secondary/final energy carrier

[sfluegel05]

Description of the issue

This comes from #390
We need to distinguish between primary, secondary and final energy carriers.

Ideas of solution

We can implement subclasses of energy carrier disposition: primary / secondary / final energy carrier disposition
Related definitions mentioned so far:

Primary fuels: Fuels which are extracted directly from natural resources. Examples are: crude oil, natural gas, coals, etc.
Secondary fuels: Fuels manufactured from primary fuels. Examples are: cokes, motor gasoline and coke oven gas, blast furnace gas.
(Glossary of the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories)

Primary Energy is energy that is contained in fuels within the biosphere and natural reserves, or captured from natural energy flows, in a suitable form for use. Inert matter removed from the extracted fuels and quantities re-injected, flared or vented are not included.
— adapted from United Nations. _International Recommendations for Energy Statistics_. 154 https://unstats.un.org/unsd/energystats/methodology/ires/ (2018), paragraph 5.10

Secondary Energy is energy that has been converted from primary energy or a different form of secondary energy.
— adapted from United Nations. _International Recommendations for Energy Statistics_. 154 https://unstats.un.org/unsd/energystats/methodology/ires/ (2018), paragraph 5.10

Final Energy is energy that is delivered to energy consumers for their use.
— adapted from United Nations. _International Recommendations for Energy Statistics_. 154 https://unstats.un.org/unsd/energystats/methodology/ires/ (2018), paragraph 5.22

Workflow checklist

• [ ] I discussed the issue with someone else than me before working on a solution
• [ ] I already read the latest version of the workflow for this repository
• [ ] The goal of this ontology is clear to me

I am aware that

• [ ] every entry in the ontology should have a definition
• [ ] classes should arise from concepts rather than from words

[Vera-IER]

I prefer to add them as subclasses of the term energy carrier (from #407).
And I suggest the following definitions:
_Primary energy carriers are energy carriers that are extracted directly from natural resources. Examples are: crude oil, natural gas, coals, etc._
_Secondary energy carriers are energy carriers that are manufactured from primary energy carriers. Examples are: cokes, motor gasoline and coke oven gas, blast furnace gas, etc.._
_Final energy carriers are energy carriers that are delivered to energy consumers for their use. Examples are: electricity, district heat, etc._

[l-emele]

Currently we do not have a class energy carrier, but only the energy carrier disposition. And even if we finally implement energy carrier in #407 the distinction between primary, secondary and final seems to be more disposition-like.
When we finally have energy carrier we might create something via equivalent classes like:

'primary energy carrier'
    SubClassOf 'energy carrier'
    SubClassOf 'has disposition' some 'primary energy carrier disposition'

@stap-m : What do you think?

Anyway, we need to solve #407 first.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

_Primary energy carriers are energy carriers that are extracted directly from natural resources. Examples are: crude oil, natural gas, coals, etc._

Would not match anything that is not a resource: wind, sun shine, hydropower …

_Secondary energy carriers are energy carriers that are manufactured from primary energy carriers. Examples are: cokes, motor gasoline and coke oven gas, blast furnace gas, etc.._

Secondary energy carriers can also be made from other secondary energy carriers. E.g. coke oven gas, which is made from coke, which in turn is made from coal. Or H₂ from electricity.

[Vera-IER]

Okay, lets add these points to the definition:
_Primary energy carriers are XX that are extracted directly from natural resources or natural energy flows. Examples are: crude oil, natural gas, coals, etc.
Secondary energy carriers are XX that are manufactured from primary energy carriers or from a different form of secondary energy carriers. Examples are: cokes, motor gasoline and coke oven gas, blast furnace gas, etc.._

[stap-m]

Since energy carrier is an equivalent class (_An enery carrier is a material entity that has the disposition energy carrier disposition._) we could define primary ... and secondary energy carrier disposition and add equivalent classes as subclasses of energy carrier afterwards. What about:

• _Primary energy carrier disposition is an energy carrier disposition of material entities that are extracted directly from natural resources or that are natural energy flows. Examples are: crude oil, natural gas, coals, etc._ --> For wind and hydro this would work, for solar it requires some fantasy, though.
• _Secondary energy carrier disposition is an energy carrier disposition of material entities that are manufactured from primary energy carriers or from a different form of secondary energy carriers. Examples are: cokes, motor gasoline and coke oven gas, blast furnace gas, etc.._
• And then: primary energy carrier equivalent to (material entity and (has disposition some primary energy carrier disposition)) and same for secondary...

[sfluegel05]

Sounds good to me. We could proceed analogously with final energy carrier disposition:

• _Final energy carrier disposition is an energy carrier disposition of material entities that are delivered to energy consumers for their use. Examples are: electricity, district heat, etc._