Restructure energy subclasses

[stap-m]

Description of the issue

This comes from issue #224 but hasn't really been discussed yet. We currently have these subclasses:

• electrical energy
• chemical energy
• heat
• hydro energy
• nuclear energy
• solar energy
• wind energy

Hydro, nuclear, solar and wind energy are of a different "quality" than electrical, chemical, heat/thermal energy. We should cover this in the structure.

Ideas of solution

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

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

Hydro, nuclear, solar and wind energy are of a different "quality" than electrical, chemical, heat/thermal energy.

How so?

[Vera-IER]

We could group them into primary energy types and secondary/final energy types. But I think in #390 the conclusion was not to apply this distinction for different energy tpyes...

[sfluegel05]

Hydro, nuclear, solar and wind energy are of a different "quality" than electrical, chemical, heat/thermal energy. We should cover this in the structure.

That's a good starting point. hydro, nuclear, solar and wind energy don't describe the energy itself, but more where it comes from. I would suggest to remove these and instead use processes to distinguish between the origins of energy. So when describing a distinct portion of energy, you don't say it has the type wind energy, but you say it has the type electrical energy and it is the output of an energy transformation process which has input some wind. Most of the definitions already describe processes, e.g. hydroelectricity (Potential and kinetic energy of water converted into electricity in hydroelectric plants.), so it should be relatively straightforward to re-implement them as processes.

As for the other energy subclasses:

• chemical and electrical energy seem fine to me
• heat already has its own issue: #393
• maybe we need more subclasses (e.g. potential and kinetic energy which are already used to describe other energy subclasses and might therefore be useful for the energy transformation processes which arise from them)

[l-emele]

Technically, you are right. However, concepts like wind energy or nuclear energy are used widely used in the domain.

What about defining these concepts as equivalent classes or something like that? wind energy: Wind energy is electrical energy that is output of an energy transformation with input kinetic energy of wind. wind energy is equivalent output to of some energy transformation and has input some wind

I am sure that my idea is not yet 100% ontologically correct and needs some refinement. But I hope it depicts a way forward.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

That's a good starting point. hydro, nuclear, solar and wind energy don't describe the energy itself, but more where it comes from.

So when describing a distinct portion of energy, you don't say it has the type wind energy, but you say it has the type electrical energy and it is the output of an energy transformation process which has input some wind.

What about defining these concepts as equivalent classes or something like that? wind energy: Wind energy is electrical energy that is output of an energy transformation with input kinetic energy of wind. wind energy is equivalent output to of some energy transformation and has input some wind

This does not reflect how these concepts are used in energy modelling and in energy statistics.

IEA Energy Balances of OECD Countries, Chapter 4 "Products":

• Nucelar: Energy released by nuclear fission or nuclear fusion.
• Hydro: Hydro energy represents the potential and kinetic energy of water converted into electricity in hydroelectric plants.
• Geothermal: Geothermal energy is the energy available as heat emitted from within the earth’s crust, usually in the form of hot water or steam. It is exploited at suitable sites:
  • for electricity generation using dry stream or high enthalpy brine after flashing
  • directly as heat for district heating, agriculture, etc.
• Solar photovoltaics: Electricity from photovoltaic cells.
• Solar thermal: Solar energy is the solar radiation exploited for hot water production and electricity generation, by:
  • flat plate collectors, mainly of the thermosyphon type, for domestic hot water or for the seasonal heating of swimming pools
  • solar thermal-electric plants
  • Passive solar energy for the direct heating, cooling and lighting of dwellings or other buildings is not included.
• Tide, wave and ocean: Tide, wave and ocean represents the mechanical energy derived from tidal movement, wave motion or ocean current and exploited for electricity generation.
• Wind: Wind energy represents the kinetic energy of wind exploited for electricity generation in wind turbines.

The distinction between inputs (wind energy) and output (electricity produced from wind energy) is important and meaningful, because e.g. most impacts of energy production (like the area of a wind farm) scale (as a first approximation) directly with primary (wind) energy consumption and are separated from secondary (electric) energy production by the conversion efficiency, which is an independent variable.
Not representing primary energy accounting as it is used in the domain would be a serious flaw of the ontology, in my view.

[l-emele]

So what is your proposal how to solve this issue?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

So what is your proposal how to solve this issue?

None. As I don't really see what the issue is.

Hydro, nuclear, solar and wind energy are of a different "quality" than electrical, chemical, heat/thermal energy.

How so?

[sfluegel05]

What about defining these concepts as equivalent classes or something like that? wind energy: Wind energy is electrical energy that is output of an energy transformation with input kinetic energy of wind. wind energy is equivalent output to of some energy transformation and has input some wind

That is a good idea. We could use relations like this to describe the differences between different forms of energy. I am not sure if we should also change the hierarchy between the energy subclasses. Is, for example, wind energy really a subclass of electrical energy? Could you also generate other forms of energy from wind like heat?

[l-emele]

Okay, maybe my example was confusing as it implied one specific way wind energy is treated in some energy balances where the (electrical) output of a wind turbine is treated as equal to the wind energy input of that transformation (i.e. implied efficiency of 100%).

Probably we should be more general. But I think my basic idea of defining classes like wind energy via its relations to processes and other classes we already have is still useful.

[stap-m]

What about the following process:

1. We fix the subclasses of energy (kinetic, eletrical, chemical, thermal)
2. We fix #390 and #575
3. Then we talk about wind energy etc., which can't be defined without some of the classes from 1.) and 2.)

[Vera-IER]

Sounds good,

We fix the subclasses of energy (kinetic, eletrical, chemical, thermal)

I would keep nuclear energy and solar energy (or an alternative term), because they cannot be described as a subclass of these 4 energy forms.

[stap-m]

We discussed chemical energy and electrical energy in #224. This should be done for now. Thus, we need a def for kinetic energy and thermal energy. Any suggestions?

[stap-m]

Proposal: kinetic energy: energy that a a material entity possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to a stated velocity. source

[Vera-IER]

Sounds good! proposal for thermal energy: The thermal energy is the energy that a material entity containes in the motion and vibration of its molecules. Thermal energy is measured through temperature. source

[l-emele]

I like the suggestions for both kinetic energy and thermal energy.

[sfluegel05]

Should we implement this definitions then (but leave the issue open for the next discussion steps)?

What would happen to heat? Do we just rename it to thermal energy with the new definition?

[stap-m]

We have another proposal for a def for thermal energy from @0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q here which is: Thermal energy is the energy of a portion of matter that is available for thermodynamic transformation processes when the portion of matter is in thermodynamic equilibrium. Let's discuss the proposals.

[Vera-IER]

Maybe we can combine the definitions?

I suggest that we include heatas an alternative term to thermal energy. I know it's not the same, but in the language of energy system modellers they are used as synonyms. For example, we report final energy consumption of "heat", Eurostat does and also the IAMC template uses the variable "Final energy|Heat". And we could put an editor note expllaining the thermodynamic definition of heat?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

I suggest that we include heatas an alternative term to thermal energy. I know it's not the same, but in the language of energy system modellers they are used as synonyms.

Sure.

Maybe we can combine the definitions?

I've more or less given up on bringing some physical rigour into these definitions, which seems to be subordinated to metaphysical concepts, e.g. "Aristotelianess". But to point out these issues:

thermal energy: The thermal energy is the energy that a material entity containes in the motion and vibration of its molecules. Thermal energy is measured through temperature.

1. This excludes i.a. noble gases, which don't form molecules.
2. "motion and vibration" is imprecise and over-specific at the same time.
   • Directed motion (like the motion of hot water through district heating pipes) does not contribute to thermal energy, only undirected motion.
   • Vibration would not include rotation of molecules, which is a sizeable chunk if one gets down to statistical mechanics.
3. This does not include other important parts, e.g. the electric potential energy between atoms that mediates pressure.
4. Temperature is not a measure of thermal energy. If I tell you the temperature of a body, you can't tell me its thermal energy.

As I noted, my proposal is a bastardisation at best, due to the fact that (as also noted before) physics does not much care about "what something is", but about "what something does". So the definition of internal energy is based on how it changes, not what "it consists of".

But since I doubt anybody will read the definition for thermal energy and go "That's not correct. I'm not annotating my data with that!", I don't much care about the definitions.

And we could put an editor note expllaining the thermodynamic definition of heat?

As in explaining why heat is included as an alternative term, although this is not heat (in the strict sense of the term)? Sure.

[Vera-IER]

I am not a physicist - I am also happy to go with the definition proposal of @0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q .

As in explaining why heat is included as an alternative term, although this is not heat (in the strict sense of the term)? Sure.

Could you formulate such a note?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

"Heat", although it strictly speaking describes a mode of energy transfer, not an energy, is included as a colloquialism for "thermal energy", following everyday usage.

[l-emele]

I've more or less given up on bringing some physical rigour into these definitions, which seems to be subordinated to metaphysical concepts, e.g. "Aristotelianess".

"Aristotelianess" does not mean to give up physical rigour, but is a way to formulate the definition in a standardised form, see Principles for Definitions: 'S' is a 'G' that 'Ds'. In the D part you can and should be precise and when defining a physical class that definitely means being physical rigid.

thermal energy: The thermal energy is the energy that a material entity containes in the motion and vibration of its molecules. Thermal energy is measured through temperature.

1. This excludes i.a. noble gases, which don't form molecules.

That part can in my opinion easily be solved by extending the definition by writing ... of its molecules and atoms.

4. Temperature is not a measure of thermal energy.  If I tell you the temperature of a body, you can't tell me its thermal energy.

I agree. We should exclude the temperature sentence from the definition.

"Heat", although it strictly speaking describes a mode of energy transfer, not an energy, is included as a colloquialism for "thermal energy", following everyday usage.

Your are basically giving here a definition for heat. If we agree that heat is an energy transfer than we should define it properly as such a class. But even if we define a heat class as subclass of energy transfer then we could still use heat as alternative term for thermal energy. So if we add an editorial note then it then should also point to that properly defined heat class.

[Vera-IER]

What about we take the first part of my definition proposal and change it to be more physical correct and as a second sentence, @0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q can formulate something without Aristotelian roules? thermal energy: The thermal energy is the energy that a material entity containes in the undirected motion, vibration and rotation of its molecules and atoms. + 2nd sentence

I would prefer to not include a heat class as a thermodynamic term. I don't see an use case for energy system models to use heat as a thermodynamic state variable and the users of the ontology might be confused and use the wrong heat term to annotate their data.

[l-emele]

The thermal energy is the energy that a material entity containes in the undirected motion, vibration and rotation of its molecules and atoms.

I consent to this definition.

I would prefer to not include a heat class as a thermodynamic term. I don't see an use case for energy system models to use heat as a thermodynamic state variable and the users of the ontology might be confused and use the wrong heat term to annotate their data.

Are you arguing against including a concept of thermal energy transfer or against using the label heat for that?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

thermal energy: Thermal energy is the energy that a material entity contains in the undirected motion of its constituent parts (e.g. molecules and atoms).

(Vibration and rotation are motion too, no need to single them out. And there's also ions and electrons, so lets not claim to be exhaustive.)

+ 2nd sentence

I didn't get why we need a second sentence, sorry.

I would prefer to not include a heat class as a thermodynamic term. I don't see an use case for energy system models to use heat as a thermodynamic state variable and the users of the ontology might be confused and use the wrong heat term to annotate their data.

So would I. We can include heat should the need arise.

If we agree that heat is an energy transfer than we should define it properly as such a class. But even if we define a heat class as subclass of energy transfer then we could still use heat as alternative term for thermal energy. So if we add an editorial note then it then should also point to that properly defined heat class.

So we should include a class heat for the sole purpose of pointing from the editorial note of thermal energy to it, telling people these are not the same, although the alternative term for thermal energy and the name of the heat class are both "heat"?

[l-emele]

If we agree that heat is an energy transfer than we should define it properly as such a class. But even if we define a heat class as subclass of energy transfer then we could still use heat as alternative term for thermal energy. So if we add an editorial note then it then should also point to that properly defined heat class.

So we should include a class heat for the sole purpose of pointing from the editorial note of thermal energy to it, telling people these are not the same, although the alternative term for thermal energy and the name of the heat class are both "heat"?

That would be a better solution. I am sure that we sooner or later need the concept of thermal energy transfer anyway. And defining the different classes and using the alternative terms to show the ambiguity is the way we deal with in the ontology, see for example wind turbine. Maybe an @OpenEnergyPlatform/oeo-general-expert-formal-ontology can explain this better.

[Vera-IER]

I didn't get why we need a second sentence, sorry.

I thought the definition is not complete yet because of your comment:

3. This does not include other important parts, e.g. the electric potential energy between atoms that mediates pressure.

If you already agree to the definition, how it is now, it's fine. thermal energy: Thermal energy is the energy that a material entity contains in the undirected motion of its constituent parts (e.g. molecules and atoms).

Are you arguing against including a concept of thermal energy transfer or against using the label heat for that?

Both. I don't have a use case in my mind, for which this concept might be needed. But I understand that if we would include such a class we could show the ambiguity in an elegant way (which is not needed in my pragmatic view).

[stap-m]

I am sure that we sooner or later need the concept of thermal energy transfer anyway.

Then let's discuss its def here #393. For thermal energy it seems that we have an agreement 🎉 Let's implement it along with kinetic energy. Any volunteers?

[stap-m]

What do we do with the remaining subclasses of thermal energy? Own issue?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

That's #393, no?

[stap-m]

Right. Sorry, I was confused.

[stap-m]

This related to #660

[stap-m]

In the todays dev-meeting we decided to restructure the energy subclasses like wind energy and solar energy etc. as follows: 1) find primary energy (subclass of energy) 2) find primary energy carrier 3) find primary energy process 4) find energy transformation process

[stap-m]

The only subclass that is not restructured yet is nuclear energy. I don't see a good parent class but energy directly. What do @OpenEnergyPlatform/oeo-domain-expert-energy-modelling think?

[Vera-IER]

I agree.

[stap-m]

Or call it nuclear binding energy ? In wikipedia it's defined like this: Nuclear binding energy is the minimum energy that would be required to disassemble the nucleus of an atom into its component parts. Then we could have nuclear fission energy as subclass, and probably also nuclear fusion energy.

[Vera-IER]

I think both ideas are good. The second suggestion would be more in line with the structure of the other energy classes. But I wouldn't include nuclear fusion energy into the ontology.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

Then we could have nuclear fission energy as subclass, and probably also nuclear fusion energy.

1) Nuclear fission and nuclear fusion derive their energy from the same source -- nuclear binding energy. 2) Fission and fusion are processes, not energy types, so they shouldn't be part of the definition of the "primary energy" (to my understanding).

[stap-m]

Right, we should stick to the workflow. Let's do this in a separate issue, see #692.

a: primary energy process b: transformation process c: primary energy d: primary energy carrier

Anyway, is this a consensus for nuclear binding energy? Then, we could implement and close this issue finally.

[stap-m]

Any objections to implementing?

[Vera-IER]

What would be the definition? Here is a aristotelian proposal: Nuclear binding energy is a form of energy that describes the minimum amount of energy which would be required to disassemble the nucleus of an atom into its component parts.

[stap-m]

Oder noch kürzer? Nuclear binding energy is the energy that is minimally required to disassemble the nucleus of an atom into its component parts. Vielleicht kann man das "minimal" auch weglassen?

[l-emele]

I agree.