Ontology: artificial objects and energy transformation need more axiomatic connections

[sfluegel05]

Description of the issue

In #737 @l-emele said:

In #372 we already had a long discussion which touched also the aspect of connecting the objects to energy transformations. But as far as I can see we did only some top-level relations (i.e. relating energy converting device to energy transformation etc) but not for the subclasses. But I am to doing that now as we now have a much better structure in energy transformation as back then.

Ideas of solution

We should look at the subclasses of artificial object, especially the subclasses of energy converting device and power generating unit and add fitting relations.
Useful object properties are:

• participates in: _a relation between a continuant and a process, in which the continuant is somehow involved in the process_
• produces: _a produces b if some process that occurs_in a has_output b, where a and b are material entities._
• uses: _A relation that holds between a continuant and another continuant it requires to function._

An example: PV cell is defined as _a generator that converts light into electrical energy._, but has no axioms.
We could add

• participates in some photovoltaic energy transformation
• uses some photon / solar energy (?)
• produces some electrical energy

Results so far

New classes

• hydrogen fuel cell: _A hydrogen fuel cell is a fuel cell that uses hydrogen._ (+ axiom hydrogen fuel cell uses some hydrogen)
• natural gas turbine: _A natural gas turbine is a gas turbine fueled with natural gas._ (+ axiom natural gas turbine uses some natural gas)

New / changed axioms

| subject | predicate | object |
|:-:|:-:|:-:|
| electro motive generator | uses | some kinetic energy |
| fuel cell | uses | some ~hydrogen~ fuel |
| fuel cell | participates in | some redox reaction |
| PV cell | uses | some solar energy |
| PV cell | participates in | some photovoltaic energy transformation |
| heat exchanger | uses | some thermal energy |
| heat exchanger | produces | some thermal energy |
| electric heat pump | uses | some electrical energy |
| solar thermal collector | ~has physical input~ uses | ~only solar thermal heat~ some solar energy |
| solar thermal collector | participates in | some solar thermal energy transformation |
| solar thermal collector | produces | some solar thermal energy |
| motor | produces | some kinetic energy / rotational energy |
| pump | produces | some (kinetic energy or potential energy) |
| steam reformer | uses | some hydrocarbon (new class) |
| steam reformer | produces | some syngas (new class) |
| gas turbine | produces | some ~electrical energy~ kinetic energy / rotational energy |
| gas turbine | uses | ~only natural gas~ some combustion fuel |
| hydrogen turbine | uses | ~only~ some hydrogen |
| turbine | produces | some kinetic energy / rotational energy |
| steam turbine | produces | some ~electrical energy~ kinetic energy / rotational energy |
| steam turbine | uses | some steam |
| steam turbine | participates in | some steam-electric process |
| steam turbine | uses | some thermal energy |
| water turbine | participates in | some hydro energy transformation |
| water turbine | produces | some ~electrical energy~ kinetic energy / rotational energy |
| wind rotor | participates in | some wind energy transformation |
| wind rotor | uses | some wind energy |
| wind rotor | produces | some ~electrical energy~ kinetic energy / rotational energy |
| water electrolyser | uses | some electrical energy and some water |
| water electrolyser | produces | some hydrogen, oxygen (new class) and chemical energy |
| power generating unit | produces | some electrical energy |
| hydro power unit | participates in | some hydroelectric energy transformation |
| solar power unit | uses | some solar energy |
| solar thermal power unit | produces | some thermal energy |
| wind energy converting unit | uses | some wind energy |

other changes:

• electric heat pump: we should use definition-annotation instead of comment annotation and change "electric energy" to "electrical energy" in the definition text
• lignite power unit has an axiom EquivalentTo uses some lignite. This is probably a mistake and should be changed to SubClassOf uses some lignite

To Do

• hydrocarbon and syngas are part of the definition of steam transformer, but don't exist in the ontology yet. We should add them
• we should add rotational energy, which is used in the definition of motor and turbine
• water turbine is defined as _converting potential energy and kinetic energy of water_, but has the axiom uses some hydro energy. We should change either the definition or the axiom. The same applies to wind rotor.
• oxygen is used to define water electrolyser

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

[sfluegel05]

Here is a list of relations I was able to derive from the definitions:
| subject | predicate | object |
|:-:|:-:|:-:|
| electro motive generator | uses | some kinetic energy |
| fuel cell | uses | some ~hydrogen~ fuel |
| fuel cell | participates in | some redox reaction |
| PV cell | uses | some solar energy |
| PV cell | participates in | some photovoltaic energy transformation |
| heat exchanger | uses | some thermal energy |
| heat exchanger | produces | some thermal energy |
| electric heat pump | uses | some electrical energy |
| solar thermal collector | ~has physical input~ uses | ~only solar thermal heat~ some solar energy |
| solar thermal collector | participates in | some solar thermal energy transformation |
| solar thermal collector | produces | some solar thermal energy |
| motor | produces | some kinetic energy / rotational energy |
| pump | produces | some (kinetic energy or potential energy) |
| steam reformer | uses | some hydrocarbon (new class) |
| steam reformer | produces | some syngas (new class) |
| gas turbine | produces | some ~electrical energy~ kinetic energy / rotational energy |
| turbine | produces | some kinetic energy / rotational energy |
| steam turbine | produces | some ~electrical energy~ kinetic energy / rotational energy |
| steam turbine | uses | some steam |
| steam turbine | participates in | some steam-electric process |
| steam turbine | uses | some thermal energy |
| water turbine | participates in | some hydro energy transformation |
| water turbine | produces | some ~electrical energy~ kinetic energy / rotational energy |
| wind rotor | participates in | some wind energy transformation |
| wind rotor | uses | some wind energy |
| wind rotor | produces | some ~electrical energy~ kinetic energy / rotational energy |
| water electrolyser | uses | some electrical energy and some water |
| water electrolyser | produces | some hydrogen, oxygen (new class) and chemical energy |
| power generating unit | produces | some electrical energy |
| hydro power unit | participates in | some hydroelectric energy transformation |
| solar power unit | uses | some solar energy |
| solar thermal power unit | produces | some thermal energy |
| wind energy converting unit | uses | some wind energy |

Some minor issues I noticed:

• electric heat pump: we should use definition-annotation instead of comment annotation and change "electric energy" to "electrical energy" in the definition text
• hydrocarbon and syngas are part of the definition of steam transformer, but don't exist in the ontology yet. We should add them
• we should add rotational energy, which is used in the definition of motor and turbine
• water turbine is defined as _converting potential energy and kinetic energy of water_, but has the axiom uses only hydro energy. We should change either the definition or the axiom. The same applies to wind rotor.
• lignite power unit has an axiom EquivalentTo uses some lignite. This is probably a mistake and should be changed to SubClassOf uses some lignite

[l-emele]

Looks good. I would add solar thermal collector produces some solar thermal energy.

[l-emele]

Regarding the fuel cell: Maybe we need a new subclass hydrogen fuel cell that gets the axiom uses some hydrogen that currently the fuel cell has.

[l-emele]

Proposal for definition for hydrogen fuel cell; _A hydrogen fuel cell is a fuel cell that uses hydrogen._ I think we can include this subclass as part of this restructuring issue and do not need a separate issue for that.

[sfluegel05]

I like the idea of including a class hydrogen fuel cell.

[l-emele]

I found a further inconsistency: hydrogen turbine is a subclass of gas turbine. Those classes have the following problematic axioms:

• 'gas turbine' uses only 'natural gas'
• 'hydrogen turbine' uses only 'hydrogen'

If a gas turbine uses only natural gas, then a subclass of it cannnot use only something else. Also I am not happy here with the uses only part of the axioms for a second reason: Every gas turbine needs also an oxidiser. Almost all gas turbines use air (which has oxygen as part).

The first axiom does not match the definition of gas turbine which has no limitation to natural gas: _A gas turbine is a turbine that converts chemical energy into rotational energy using a continous internal combustion process. Hence it is also called combustion turbine._

To fix this, we could introduce a natural gas turbine (or natural gas gas turbine?) which might be defined in parallel to hydrogen turbine: _A natural gas turbine is a gas turbine fueled with natural gas._

[sfluegel05]

The first axiom does not match the definition of gas turbine which has no limitation to natural gas: _A gas turbine is a turbine that converts chemical energy into rotational energy using a continous internal combustion process. Hence it is also called combustion turbine._

To fix this, we could introduce a natural gas turbine (or natural gas gas turbine?) which might be defined in parallel to hydrogen turbine: _A natural gas turbine is a gas turbine fueled with natural gas._

I agree. This means we also need a new class for the gas turbine uses some ... axiom. I would suggest combustion fuel, which is the first common superclass of both hydrogen and natural gas.

If a gas turbine uses only natural gas, then a subclass of it cannnot use only something else. Also I am not happy here with the uses only part of the axioms for a second reason: Every gas turbine needs also an oxidiser. Almost all gas turbines use air (which has oxygen as part).

This is indeed a problem. I just added turbine uses some fluid in PR #769 which lead to a long list of unsatisfiable classes. So I agree that we should change the uses only-axioms. An easy solution would be to replace "only" with "some".

[sfluegel05]

I tried to summarize the results so far in the issue header. Since this issue has gotten pretty comprehensive already, I would suggest to implement what we have (if everyone agrees). For the To Do points, we can open new issues (at least for hydrocarbon / syngas and rotational energy. After taking a closer look at it, water turbine and wind rotor are not really a problem, because hydro energy and wind energy are forms of kinetic energy according to our structure)

[stap-m]

I agree. This means we also need a new class for the gas turbine uses some ... axiom. I would suggest combustion fuel, which is the first common superclass of both hydrogen and natural gas.

(combustion fuel and has state of matter gaseous) ?!

[l-emele]

The word _gas_ in _gas turbine_ does not mean that it uses a gaseous fuel but that it uses a gas as working medium (i.e. air in most cases) that is heated in an internal combustion (hence the alternative term _combustion turbine_).

A gas turbine can also used with other combustion fuels than gaseous fuels, some power plants with gas turbines use e.g. heating oil. Most airplanes have gas turbines as engine and use kerosene.