heat and subclasses need definition update and maybe reclassification

[stap-m]

Description of the issue

• The definitions of the heat and subclasses are not aristotelian / have no def at all.
• The subclasses are rather use cases for heat that "types" of heat. A reclassification should be discussed.

Ideas of solution

Workflow checklist

• [ ] I discussed the issue with someone else than me before working on a solution
• [x] I already read the latest version of the workflow for this repository
• [x] I added this issue to the Project 'Issues'. If suitable, I add it to further Projects.
• [x] The goal of this ontology is clear to me

I am aware that

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

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

What is meant by "heat"?

In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter.

That describes a flow of energy, thus a power. The energy class however describes energy that is a quality of matter. I suspect that "thermal energy" was meant when this was set up.

The sub-classes are a mixed bunch:

• Ambient heat:

  Ambient heat, understood as heat that is naturally around us in its diffuse and extended form, emanates from a diversity of heat sources, including earth, water, or air, and is increasingly attracting the attention of those concerned with energy and sustainability.

  Let's take note that the first sentences of random papers usually don't make for useful definitions.
  I gather that the intention was to describe an energy flow "heat […] emanates from […] sources", but I'm not sure what it's supposed to be or who (what kind of model) needs it.

• Derived heat:

  Derived heat covers the total heat production in heating plants and in combined heat and power plants. It includes the heat used by the auxiliaries of the installation which use hot fluid (space heating, liquid fuel heating, etc.) And losses in the installation/network heat exchanges. For autoproducing entities (= entities generating electricity and/or heat wholly or partially for their own use as an activity which supports their primary activity) the heat used by the undertaking for its own processes is not included.

  Reads like "gross heat production" to me. Would be linked to issue #394 then.

• District heat:

  District heating (also known as heat networks or teleheating) is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from nuclear power electricity generation.

  Not sure what the purpose of this class is. Is it an energy? An energy flow? An energy network?

• Geothermal heat:

  Energy available as heat emitted from within the earth's crust, usually in the form of hot water or steam. This energy production is the difference between the enthalpy of the fluid produced in the production borehole and that of the fluid eventually disposed of. It is exploited at suitable sites:

  • for electricity generation using dry steam or high enthalpy brine after flashing,
  • directly as heat for district heating, agriculture etc

  I say Aristotelianise the independent clause, drop the rest.

  Geothermal energy is thermal energy that is available as heat emitted from within the earth's crust.

• Solar thermal heat:

  Heat from solar radiation; can consist of:

  • solar thermal-electric plants; or
  • equipment for the production of domestic hot water or for the seasonal heating of swimming pools (e.g. flat plate collectors, mainly of the thermosyphon type).

  Neither electric plants nor any equipment are energy (or heat for that matter).

  Solar thermal energy is thermal energy from solar radiation.

It would help to have concrete use cases of how these classes are intended to be used. @OpenEnergyPlatform/oeo-domain-expert-energy-modelling

[l-emele]

* Derived heat:
  > Derived heat covers the total heat production in heating plants and in combined heat and power plants. It includes the heat used by the auxiliaries of the installation which use hot fluid (space heating, liquid fuel heating, etc.) And losses in the installation/network heat exchanges. For autoproducing entities (= entities generating electricity and/or heat wholly or partially for their own use as an activity which supports their primary activity) the heat used by the undertaking for its own processes is not included.

  Reads like "gross heat production" to me.  Would be linked to issue #394 then.

"Derived heat" is a form of energy but "gross heat production" is a process.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

I'm puzzled.

"gross heat production" is a process.

and

"Gross production" is the energy production including own consumption of the plant while "net production" is excluding the own consumption. So "net production" is the amount of energy that can be e.g. fed into the grid or delivered to the consumer. https://github.com/OpenEnergyPlatform/ontology/issues/394#issuecomment-629071477

contradict each other. Either "gross heat production" is an amount of energy (like gross and net production), or it is a process. Can you describe an example?

---

"Derived heat" is a form of energy

And how is it used? By the logic of the ontology (as far as I grasp it), a heating plant would be an energy conversion device that transforms some form of energy into derived heat? It would them be used by whom? And it differs from district heat in what aspects?

[stap-m]

I edited the issue title. It's useles to dicuss the heat subclasses without having a good definition and classification for heat itself, sorry.

I agree that with the new def of energy, heat as it is defined currently is in the wrong place. The def is obviously copy and paste from wikipedia and has not been restructured and brought into Aristotelian format yet.

A subclass thermal energy as subclass of energy would be intuitive. How would a class thermal energy and a class heat be related? Maybe heat should be replaced with something like heat flow to make the process/power character visible?

[l-emele]

I'm puzzled.

"gross heat production" is a process.

and

"Gross production" is the energy production including own consumption of the plant while "net production" is excluding the own consumption. So "net production" is the amount of energy that can be e.g. fed into the grid or delivered to the consumer. #394 (comment)

contradict each other. Either "gross heat production" is an amount of energy (like gross and net production), or it is a process. Can you describe an example?

Sorry, I formulated slopy and forgot a part.

Energy production is in my view a form of energy transformation and hence a process. And I should have written:

"Gross produced energy" is the energy production including own consumption of the plant while "net production" is excluding the own consumption. So "net produced energy" is the amount of energy that can be e.g. fed into the grid or delivered to the consumer.

It is important that we distinguish between the energy transformation process (energy production) and the energy itself.

[l-emele]

A subclass thermal energy as subclass of energy would be intuitive. How would a class thermal energy and a class heat be related? Maybe heat should be replaced with something like heat flow to make the process/power character visible?

I like your suggestion. Maybe we could avoid heat completely as it is ambiguous.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

I agree that with the new def of energy, heat as it is defined currently is in the wrong place. The def is obviously copy and paste from wikipedia and has not been restructured and brought into Aristotelian format yet.

A subclass thermal energy as subclass of energy would be intuitive. How would a class thermal energy and a class heat be related? Maybe heat should be replaced with something like heat flow to make the process/power character visible?

I don't really care where it is in the ontology or how the definition is formulated. The definition is correct for heat, but the subclasses describe thermal energy. If this is about having classes of thermal energy, there is no point in having a heat class.

I can see that models would want to refer to quantities of thermal energy which are either stored (thermal storage), transported (district heating networks), or used (domestic heating, industrial process heat). (Our model does.) What I don't see yet (but am open to being educated on) is that models need to refer to "heat" as a thermodynamic process. "Heat" in thermodynamics is akin to an adverb, not a noun. There is no "heat" as an entity. Energy can flow from one thermodynamic system (with higher temperature) to another thermodynamic system (with lower temperature) as heat. And then "heat" is a collective term for three distinct process: radiation, transmission, and convection. Calling it a "heat flow" would ring true to most technicians. But do we need it in the ontology? I suggest asking @OpenEnergyPlatform/oeo-domain-expert-energy-modelling they need heat in the ontology, as opposed to (flows of) thermal energy.

---

Energy production is in my view a form of energy transformation and hence a process.

Ok. But why is the process of energy production needed in the ontology? (Kind of working through my thought process here.) I see two possibilities:

• Either we need it for "modelling the energy system". But that's not really the scope of the ontology, as I understand it. And also that's implicitly done already. If there's a energy converting device like a heater that has some physical_output thermal energy (currently it's heat, but I would argue that's a colloquial synonym) and presumably has some physical_input chemical energy (currently missing), the thing is described sufficiently, I think.
• Or we need to quantify the "amount of energy (heat/thermal energy) production". But that is either an empirical fact, so in the realm of "gross/net produced energy" (measured in J/s) or if we talk "capacities" a power rating (measured in W).

How would the process heat production connect to the rest of the ontology?

[l-emele]

But why is the process of energy production needed in the ontology?

Because we want to organise the terms systematically.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

Because we want to organise the terms systematically.

Ok. And which terms can't be organised systematically in the ontology without a class for an energy production process? In other words:

How would the process heat production connect to the rest of the ontology?

[l-emele]

I just realised that we have discussions in parallel. So I suggest that we discuss in this issue only the heat subclasses and concentrate the discussions on net and gross generation in issue #394.

[stap-m]

This won't be fixed for the first release, right? Thus, I'm removing the 1st milestone and add the 2nd instead.

[Vera-IER]

It would help to have concrete use cases of how these classes are intended to be used.

We can report with our model for example the final energy consumption of the houshold sector and we use most of the terms from the subclasses. For example final energy consumption of the houshold sector coming from ambient heat (to indicate how much ambient heat is used in heat pumps), from district heat, from geothermal heat, etc.

The only term we don't use is derived heat, which I would delete from the heat subclasses. Instead it would be nice to have gross heat generation as a subclass of gross generation , which we can discuss furhter in #394 ?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

For example final energy consumption of the houshold sector coming from ambient heat (to indicate how much ambient heat is used in heat pumps)

Huh? You report the heat input into heat pumps? I can totally see reporting the output of heat pumps, but that is the sum of heat and electricity inputs. Why do you report something that is free (as in free beer)? But it's possible, sure.

In any case, all the things you described ("ambient heat", "district heat", "geothermal heat") are – labels non-withstanding – energy flows, so potential subclasses of thermal energy and not heat.

It won't be possible to find a definition of thermal energy and satisfies OEO idiosyncrasies and physics, but here's a bastardised proposal:

thermal energy: 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.

[sfluegel05]

We already have a definition proposal for thermal energy in #522, so I suggest we don't discuss the same topic here as well. Maybe we can continue with the subclasses of heat / thermal energy here after #522 has come to a conclusion.

[Vera-IER]

Huh? You report the heat input into heat pumps? I can totally see reporting the output of heat pumps, but that is the sum of heat and electricity inputs. Why do you report something that is free

If someone is only interested only in heat pumps, I agree that providing the ambient heat input seems strange. But if one is interested in the whole energy systems and wants to see how the final energy consumption changes from fossil to renewable energy, it's common practice to report it in that way. Also Eurostat reports final energy consumption of ambient heat.

[l-emele]

I agree with @Vera-IER : Also in our modelling ambient heat is considered. If you deal with technical and not only economic aspects in the modelling this often makes sense, even if there is no direct cost associated with ambient heat. But of course I understand that for some modelling questions ambient heat is irrelevant.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

But if one is interested in the whole energy systems and wants to see how the final energy consumption changes from fossil to renewable energy, it's common practice to report it in that way. Also Eurostat reports final energy consumption of ambient heat.

Ah, ok. I can see that.

[Vera-IER]

I don't know if we can solve this until tomorrow, but I try to sum up the discussion:

1. We could add a new heat class to show the ambiguity of heat. The parent class could be energy transformation and the definition can be derived from that comment:

"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.

Then we could use heat as alternative term for thermal energy and add an editorial note which points to the properly defined heat class.

2. We delete derived heat from the suclasses of thermal energy.
3. The definitions of the other suclasses need to be rewritten. So far we have:

Geothermal energy is thermal energy that is available as heat emitted from within the earth's crust.

Solar thermal energy is thermal energy from solar radiation.

And some more suggestions: Ambient heat is thermal energy that is naturally around us in its diffuse and extended form and emanates from a diversity of heat sources, including earth, water, or air. District heat is thermal energy that is generated in a centralized location and distributed through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from nuclear power electricity generation.

[stap-m]

I agree for point 1) and 2) of @Vera-IER s summay. Maybe we can implement this as a first step, if others agree, too.

For 3): Geothermal and solar thermal energy should be somehow classified similar to the classes wind energy, solar energy, hydro energy etc. I'd suggest not to classify them as subclasses of energy or its subclasses. In the OEO, we'll use these energy types in the sense of its conversion and the relation to their energy carrier. Maybe we need an own issue for that, it is also related to #515 and #522. Or discuss this in the upcoming dev meeting?!

[stap-m]

district heat / derived heat seems to be the only missing part of this issue.

[sfluegel05]

solar thermal heat also hasn't been addressed yet.

[l-emele]

We have defined: Solar thermal energy transformation is a solar energy transformation that converts solar energy into thermal energy.

So we could define: Solar thermal energy is thermal energy that is the physical output of a solar thermal energy transformation.

[stap-m]

As decided in oeo-dev-meeting 19 we implement

• solar thermal energy is thermal energy that is the physical output of a solar thermal energy transformation.
• grid-bound heating (process) a heat transfer over a distance via a heating grid, using steam or (hot) water
  • alternative term: distance heating
  • subclass: district heating ... to residential and commercial buildings.
    • alternative term: district grid-bound heating process
  • subclass: industrial grid-bound heating (process) ... to industry/industrial installations.
  • axioms:
    • has participant some heating grid
    • has participant some (liquid water or steam)
• grid transferred thermal energy is thermal energy that is transferred via the grid-bound heating process.
  • alternative heat: derived heat
  • axiom: participates in some grid-bound heating process

Afterwards this issue will be clodes. A new issue for waste heat will be opened.