Restructure `energy storage` and `energy storage object`

[l-emele]

Description of the issue

We have energy storage as a function: Energy storage is a function of an artificial object that has been engineered to contain energy for conversion as usable energy later. Subclasses:

• battery storage: A battery storage is a energy storage that uses batteries to store energy.
• methanation gas storage: A methanation gas storage is a energy storage that uses carbon dioxide and hydrogen from electrolysis to produce methan and store this. The methan can then be used to produce electricity or heat in a gas generator.
• pumped storage: A pumped storage (pumped-storage hdyroelectricity) is an energy storage that uses water from a higher reservoir to generate energy.
• thermal energy storage: A thermal energy storage is an energy storage that stores thermal energy for later use.

And we have energy storage object as subclass of artificial object: An energy storage object is an artificial object that has the function energy storage. Subclasses:

• battery: A battery is an energy storage object using different chemical or physical reactions to store energy. (And further subclasses)
• power-to-liquid system: A power-to-liquid (often abbreviated P2L or PtL) system is an energy storage object that converts electrical power to a liquid fuel.
• SMES: Superconducting magnetic energy storage (SMES) systems store energy in the magnetic field created by the flow of direct current in a superconducting coil which has been cryogenically cooled to a temperature below its superconducting critical temperature. A typical smes system includes three parts: superconducting coil, power conditioning system and cryogenically cooled refrigerator. Once the superconducting coil is charged, the current will not decay and the magnetic energy can be stored indefinitely.
• underground hydrogen storage: An underground hydrogen storage is an energy storage object that stores hydrogen underground. Examples are underground caverns, salt domes and depleted oil/gas fields.

At least to me, there is no clear distinction between the subclasses of energy storage and the subclasses of energy storage object. It is not obvious, why we need this parallel structure. Most subclasses of energy storage could also be subclasses of energy storage object. Also most of these classes lack axioms.

Ideas of solution

• Make energy storage object equivalent to 'artificial object' and ('has function' some 'energy storage').
• Add axiom 'energy storage' 'has bearer' some 'artificial object'.
• Discuss whether methanation gas storage, pumped storage and thermal energy storage are rather objects than functions. If these stay functions, improve definitions.

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

[l-emele]

Also we could think about improving the definition of the energy storage function. At least to me, energy storage means that you get the same type of energy of a storage that you put in before. So in a battery or pumped hydro storage you put electrical energy in and get electrical energy out. In a thermal heat storage you put thermal energy in and get thermal energy out.

That differentiates to the energy carrier disposition which is defined as: An energy carrier disposition is a disposition of an material entity that contains energy for conversion as usable energy.

[Alex2448]

As far as I understood, you do not want to delete the energy storage function but rather its subclasses right? I think that makes sense. A similar discussion was also discussed in Issue209.

[l-emele]

Yes, the general energy storage function should definitely be kept, but we should discuss whether to delete, restructure, redefine or move the subclasses.

[Alex2448]

@OpenEnergyPlatform/oeo-domain-expert-energy-modelling any thoughts?

[chrwm]

We discussed in the last dev meeting, that the subclasses of energy storage function should be restructured and based on energy type, e.g. electrical-, chemical-, heat storage function.

The definitions of energy storage function and energy carrier disposition should be revisited to create a clear distinction.

[Alex2448]

As this is also important for the Issue#1261, I would like to delete battery storage, methanation gas storage, pumped storage (for underground hydrogen storage) and thermal energy storage. Instead, I propose to introduce these subclasses of energy storage function:

• For battery, use electrochemical storage with the parent class energy storage:

  •  An electrochemical storage is an energy storage that uses an electrochemical reaction to store energy. 
    

• For pumped storage, use chemical conversion storage with the parent class energy storage:

  •  A chemical conversion storage is an energy storage that uses chemical conversion to convert one matter that is hard to store to another that is easier to store.
    

For heat storages, introduce similar to Issue#1261 thermo-chemical heat storage, sensible heat storage and latent heat storage:

• thermo-chemical heat storage with the parent class energy storage:

  •  A thermo-chemical heat storage is an energy storage that uses reversible chemical reactions with thermo-chemical materials (TCM) to store thermal energy.
    

• For methanation gas storage, use similar to sensible heat storage chemical conversion storage with the parent class energy storage

  •  A chemical conversion storage is an energy storage that uses temperature changes in some medium to store thermal energy.
    

• For SMES, use latent heat storage (LHS) with the parent class energy storage:

  •  A latent heat storage (LHS) is an energy storage that uses phase transitions in phase-change materials (PCM) to stores thermal energy.
    

Additionally, to distinguish between the storage objects in Issue#1261, I would like to introduce the following classes:

• adsorption with the parent class process:

  •  Adsorption is a process that lead to an accumulation of a substance within a phase or at an interface between two phases.
    

• desorption with the parent class process:

  •  Desorption is a process that lead to a detaching of a substance that was accumulated within a phase or at an interface between two phases (for example by adsorption).
    

• phase transitions with the parent class process:

  •  A phase transition is a transformation of a medium from a solid, liquid, or gas state to a different state.
    

• evaporating with the parent class phase transitions:

  •  Evaporating is a phase transition from a liquid medium to their gaseous state.
    

• melting with the parent class phase transitions:

  •  Melting is a phase transition from a solid medium to their liquid state.
    

[carstenhoyerklick]

Do you mean pumped storage on the second bullet point?

Do we need methanation storage, is it not just a chemical conversion storage?

[l-emele]

@Alex2448 : Are the proposals in your comment on 16 September objects or functions? The agreement in OEO dev meeting 43 was to have electrical-, chemical-, heat storage function, but not go deeper, as where are else unnecessarily replicating structures that we already have somehere else. And I don't understand why you want do redefine some classes with something completely different. E.g. why do you want to redefine SMES (where energy is stored in a magnetic field) with latent heat energy storage (where energy is stored in a phase transition)?

[lumi321]

A suggestion from my side, picking up on some of the ideas above: energy storage: Energy storage is a function of an artificial object that has been engineered to contain energy for later usage whereby input energy and usable output energy are of the same type. Beneath thermal energy storage (maybe update the definition) I would add: chemical energy storage: A chemical energy storage is an energy storage with chemical energy as input and output. electrical energy storage: An electrical energy storage is an energy storage with electrical energy as input and output. kinetical energy storage: A kinetical energy storage is an energy storage with kinetical energy as input and output. potential energy storage: A potential energy storage is an energy storage with potential energy as input and output.

[l-emele]

chemical energy storage: A chemical energy storage is an energy storage with chemical energy as input and output. electrical energy storage: An electrical energy storage is an energy storage with electrical energy as input and output. kinetical energy storage: A kinetical energy storage is an energy storage with kinetical energy as input and output. potential energy storage: A potential energy storage is an energy storage with potential energy as input and output

We already agreed upon this in the last OEO dev meeting.

[lumi321]

I know. I thought it wouldn't hurt to suggest some definitions, though.

[Alex2448]

@l-emele I proposed functions. I agree that it makes not really sense to have a battery function and a battery storage object, this is repeating. However, I did not think that we agreed to implement the functions electrical-, chemical-, heat storage function, I thought that it was more a general idea to have a distinction similar to this and tried to propose how we can implement it.

[Alex2448]

Since I want to concentrate on the isseue Issue#1261, I want to just propose the functions:

• thermo-chemical heat storage with the parent class energy storage:

  •  A thermo-chemical heat storage is an energy storage that uses reversible chemical reactions with thermo-chemical materials (TCM) to store thermal energy.
    

• For sensible heat storage object, use the function chemical conversion storage with the parent class energy storage

  •  A chemical conversion storage is an energy storage that uses temperature changes in some medium to store thermal energy.
    

• For latent heat storage, I propose the function latent heat storage (LHS) with the parent class energy storage (maybe a better name would be phase transition storage or something similar):

  •  A latent heat storage (LHS) is an energy storage that uses phase transitions in phase-change materials (PCM) to stores thermal energy.
    

The problem with not having these functions and just use a heat storage function is that for some heat storage objects, I cannot axiomatically distinguish between the objects. Another idea is to have these functions as a subclass of heat storage functions, instead of energy storage like I proposed.

[l-emele]

Let's wait for tomorrow's discussion on this topic in the dev meeting.

[l-emele]

Discussed today in OEO dev 46. PR #1348 will solve this issue almost completely. For SMES I created a separate issue #1349.