Adding more heat terms

[Alex2448]

Description of the issue

In general, we should introduce more terms about heat, since over 50% of end energy usage is used for heat. In the current implementation, concepts of thermal energy are mixed with electric energy which leads to some confusion. Therefore, I propose to introduce some heat concepts: @OpenEnergyPlatform/oeo-domain-expert-energy-modelling

Ideas of solution

General:

• Introduce heat transfer unit (which has as parent class energy transformation unit)

  • A heat transfer unit is a energy transformation unit that contains a heat exchanger among other parts.

• Heat exchanger can be extended by the following subclasses:

  • A rotary heat exchanger is a heat exchanger that uses a wheel for a heat transfer process.
  • A plate heat exchanger is a heat exchanger that uses a plate for a heat transfer process.

• A power plant feeds electric energy into an electric energy grid, but a geothermal heat plant (in contrast to geothermal power plant) produces thermal energy which is feed directly into a heating grid. Since we introduce more kinds of plants that are doing this, I think it is convenient to add a new class as a parent class for these. Therefore, I would introduce a heat plant which has the parent class energy transformation unit:

  • A heat plant is an energy transformation unit consisting of heat transfer units and a grid component that feeds thermal energy into a heating grid.

• A combined heat and power plant produces per definition both electric and thermal energy. Therefore, I want to add a class named cogeneration plant which has the parent class energy transformation unit.

  • A cogeneration plant is an energy transformation unit consisting of combined heat and power generating units and a grid component that feeds thermal energy into a heating grid and a electricity grid component that feeds electrical energy into an electricity grid.
  • A combined heat and power plant (CHPP) is a cogeneration plant that has combined heat and power generating units as parts.

Solar heat:

• There are solar thermal power plants which focus mainly on producing electric energy using solar energy, but there are also solar heat plants which focus mainly on producing usable heat. Therefore, I suggest the introducing of solar heat plants which have the parent class heat plant and also solar heat unit which has the parent class heat transfer unit:

  • A solar heat plant is a heat plant that has solar heat units as parts.
  • A solar heat unit is a heat transfer unit using solar heat.

• Solar thermal collector can be extended by the following subcategories:

  • A tube collector is a solar thermal collector that uses tubes to absorb solar radiation to convert into thermal energy.
  • A flat-plate collector is a solar thermal collector that uses flat-plates to absorb solar radiation to convert into thermal energy.

Geothermal:

There are several technologies which use different depth level of geothermal heat. The deeper you drill, the hotter it is and you can get more heat but there are also higher risks and costs. In general, we distinguish between 2 layers of depth:

• Near-surface geothermal depth (up to 500m)
• Deep geothermal depth (1500m - 4500m)

Downhole heat exchanger and geothermal collector and geothermal wells are used in near-surface geothermal depth. For hydrothermal geometrie, drillings are carried out in deep geothermal depth and water (with high temperatur) from high depths is transported to the surface. This is quite similar to geothermal wells except that the wells are in near-surface geothermal depth. So to distinguish these two kinds of technology, introducing different depth level is conveniant.

The difference between petrothermal geothermal (like downhole heat exchanger and geothermal collector) and hydrothermal geothermal is that hydrothermal geothermal get the thermal energy from water which is already in the crust and petrothermal geothermal, water is pressed in the drills. So distinguishing between different media is also conveniant to describe the technologies.

This may need some discussion on how to introduce these concepts and terminologies.

But first, there are some terminologies which are quite clear:

• Introduce geothermal heat unit (which has the parent class heat transfer unit)

  • A geothermal heat unit is a heat transfer unit using geothermal heat as source.

• Introduce geothermal heat plant which has as parent class heat plant:

  • A geothermal heat plant is a heat plant that has geothermal heat units as parts.

• Introduce geothermal well system which has as parent class geothermal heat plant:

  • A geothermal well system is a geothermal heat plant that has geothermal heat units as parts.

• Additionally, there are other components of geothermal heat plants which have as parent class heat exchanger:

  • A geothermal collector is a heat exchanger that uses thermal energy to convert it into heat and consists of plastic pipes laid horizontally in the ground.
  • A downhole heat exchanger is a heat exchanger that uses thermal energy to convert it into heat and consists of plastic pipes installed vertically or inclined in a borehole.

Workflow checklist

• [X] 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] 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

[Alex2448]

There is a problem that combined heat and power generating unit and combined heat and power generation also have co-generating power unit or co-generation as alternative label. Since we want to add cogeneration plant, these have to be changed.

We can define CHPPs as a subclass of cogeneration plant or the other way around: cogeneration plant as alternative label of CHPPs and heat and power plant as the parent class. But then, we have to change several definitions in the ontology accordingly, like combined heat and power generation.

Which way do you think makes more sense? @OpenEnergyPlatform/oeo-domain-expert-energy-modelling

[Alex2448]

@OpenEnergyPlatform/oeo-domain-expert-energy-modelling:

What do you think so far about the definitions: heat transfer unit, heat exchanger, heat plant (the top four defintions, in General) as well as the definitions of Solar heat so far?

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

Heat Transfer Unit

A heat transfer unit is a energy transformation unit that contains a heat exchanger among other parts.

What's the point of "among other parts"? Are they relevant? Are they secret and can't be detailed? I suspect this got copied over from power generating unit. We should loose it there, too, as it is irrelevant. #1258

Heat Plant Are all heat plants connected to a heating grid, no matter how short?

A heat plant is an energy transformation unit consisting of heat transfer units and a grid component that feeds thermal energy into a heating grid.

So is on-site heat production in industry considered to have a very small heating grid? (I'm neither here nor there, it's just something about which we should make up our minds.)

Solar Heat

A solar heat unit is a heat transfer unit using solar heat.

1. There's no solar heat class.
2. That would make it an energy transformation unit that contains a heat exchanger using solar heat. That is not how solar thermal works. It converts radiation into thermal energy, and not by a heat exchanger.

See solar thermal energy transformation.

Co-generation

The definition of combined heat and power plant is redundant.

A combined heat and power plant (CHPP) is a cogeneration plant that has combined heat and power generating units as parts.

A cogeneration plant is an energy transformation unit consisting of combined heat and power generating units and…

I'd opt for using co-generation as an alternative term for CHP. There's also tri-generation out there (electricity, heat, and cooling; or electricity, heat, and desalinated water, depending on who tries to sell it) and there might be somebody with a process that does either electricity and desalinated water or electricity and carbon removal (using off-heat to regenerate their scrubbers) and call that co-generation. If somebody wants to annotate that with the ontology, it will have to be adapted and alternative terms are easier to shuffle than definitions, I feel.

[l-emele]

This issue covers a lot of topics. I think, it makes sense to discuss these on one of our next OEO dev meetings.

[Alex2448]

Heat Transfer Unit You are right, I tried to stay consistent and formulate definitions similar to their energy counterpart, so I copied the definition from power generating unit. So as discussed in #1258, I would also remove the "among other parts" part and the new formulation would be:

A heat transfer unit is a energy transformation unit that contains a heat exchanger.

Heat Plant I think considering different lengths of heating grid would maybe be overthinking and overengineering and complicate things unnecessarily. So I would keep things similar to power plants and stay with my proposed definition.

Solar heat:

1. As discussed in the last developer meeting, not every word of the defintion needs to be already defined in the ontology and have a class. So I think having a solar heat class may be unnecessary but I can exchange it with solar thermal energy which is already defined and the new defintion would be:

   A solar heat unit is a heat transfer unit using solar thermal energy.

2. The definition of heat exchanger is:

    A heat exchanger is an component converting device that is used for a heat transfer process.

And for the heat transfer:

    Heat transfer is an energy transfer with thermal energy as the only input and thermal energy as the only output.

So I do not think there is much of a problem for the definitions. But I can see that in reality, a heat exchanger is often not really the part of a solar thermal power plant. So one proposal to define a solar thermal unit which is not a subclass of heat transfer unit and has as parent class energy transformation unit although this might be a bit confusing:

    A solar thermal unit is a energy transformation unit that converts solar energy into thermal energy.

Co-generation:

I think maybe the motivation why we want to introduce a separate parent class is a bit unclear.

There already exists combined heat and power generation, combined heat and power plant and combined heat and power generation unit. The combined heat and power plant has as alternative label CHPP, the combined heat and power generation has as alternative label CHP but the combined heat and power generation unit has as alternative label co-generating power unit which might be a bit confusing.

combined heat and power generation is defined as:

    Combined heat and power generation (CHP) is an energy transformation that converts energy simultaneously to electrical energy and thermal energy.

So to include things like tri-generation and other cases, we still have to adapt the definition of f.e. combined heat and power generation too.

The goal with my proposed definition is to make more clear what we define as CHPs and co-generations and do it consistently and also be more open for other generations of heat and power which might not be simultaneously.

[Alex2448]

@OpenEnergyPlatform/oeo-domain-expert-energy-modelling In oeo dev 42, we discussed that Near-surface geothermal depth (up to 500m) and Deep geothermal depth (1500m - 4500m) of geothermal energy can be similar described like sector division: So the proposal in this meeting was: Creating a new subclasss of sector division: 'crust depth division'. The problem is that I cannot find any suitable destinction (besides hard numbers in meter or temperature in °C) of the crust, since we still drill in the crust and not in the mantle.

[Alex2448]

As discussed in OEO Dev 42, I would like to introduce these classes additionally to my suggestion:

• Introduce heat transfer unit (which has as parent class energy transformation unit)

  • A heat transfer unit is an energy transformation unit that can contain a heater or a heat exchanger.

• Introduce boiler (which has as parent class heater) as discussed in OEO meeting 42:

  • A boiler is a heater that increases the thermal energy of fluids.

• Introduce combustion-based heater (which has as parent class heater) as discussed in OEO meeting 42:

  • A combustion-based heater is a heater that increases the thermal energy using combustion.

• Introduce electrical heater (which has as parent class heater) as discussed in OEO meeting 42:

  • An electrical heater is a heater that increases the thermal energy using electric energy.

• Change definition of heat plant (which has as parent class combined heat and power plant) as discussed in OEO meeting 42:

  • A heat plant is a combined heat and power plant consisting of heat transfer units or a heater and a grid component that feeds thermal energy into a heating grid.

• A combined heat and power plant produces per definition both electric and thermal energy. Therefore, I want to add a superclass combined power plant and heat plant which has the parent class energy transformation unit and power plant and heat plant are subclasses of this class (and have to be adapted).

  • A combined heat and power plant (CHPP) is an energy transformation unit that can have combined heat and power generating units as parts.
  • A power plant is combined heat and power plant consisting of power generating units and a grid component that feeds electric energy into an electric grid.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

A heat plant is a combined heat and power plant consisting of heat transfer units or a heater and a grid component that feeds thermal energy into a heating grid.

Don't you think this to be confusing? Common usage would see heating plants as distinct from combined heat and power plants, in so far as they don't produce any power (e.g. https://en.wikipedia.org/wiki/Heating_plant).

[l-emele]

Common usage would see heating plant as distinct from combined heat and power plants, in so far as they don't produce any power

I agree.

[carstenhoyerklick]

I agree that may be confusing, as I think what has been meant here is the heating part of the CHP System as a heat plant. Splitting this suggests that the heat and power production can be separated, which I am not shure if this is the case.

I think the main principle of a combined heat and power plant is, that the incoming energy carrier cannot be converted into electricy completely. In the conversion process from the incoming energy carrier there will always be some heat as part of the process which is used in the CHP plant to increase the overall efficiency.

Therefore I would not create subprocess of CHP of power and heat, as this is an integrated process anyway. This would make this type of heat plant obsolete.

[Alex2448]

I agree with @0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q that heating plants are not a part of CHPs which produce mainly electricity. Heat plant produce mainly heat. Do you think that both heat plant and combined heat and power plant should be a subclass of energy transformation unit (so the same level as power plant) and there should be no common parent class?

[Alex2448]

@l-emele @carstenhoyerklick Do you think that both heat plant and combined heat and power plant (currently implemented as a subclass of power plant) should be a subclass of energy transformation unit (so the same level as power plant) and there should be no common parent class? So all 3 plants existing in parallel as a subclass of energy transformation unit?

Also, in oeo dev 42, we discussed that Near-surface geothermal depth (up to 500m) and Deep geothermal depth (1500m - 4500m) of geothermal energy can be similar described like sector division. So the proposal in this meeting was: Creating a new subclasss of sector division: 'crust depth division'. The problem is that I cannot find any suitable destinction (besides hard numbers in meter or temperature in °C) of the crust, since we still drill in the crust and not in the mantle.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

@l-emele @carstenhoyerklick Do you think that both heat plant and combined heat and power plant (currently implemented as a subclass of power plant) should be a subclass of energy transformation unit (so the same level as power plant) and there should be no common parent class? So all 3 plants existing in parallel as a subclass of energy transformation unit?

We have:

A power plant is an energy transformation unit consisting of power generating units and a grid component that feeds electric energy into an electric grid.

I'd suggest:

A heat plant is an energy transformation unit consisting of heat generating units and a grid component that feeds thermal energy into a heating grid.

A heat generating unit is an energy transformation unit that contains a heat exchanger.

(Analogous to power generating unit containing a generator.)

A combined heat and power plant is an energy transformation unit consisting of power generating units, heat generating units, a grid component that feeds electric energy into an electric grid, and a grid component that feeds thermal energy into a heating grid.

I don't see a point in a common parent class between the plants and energy transformation unit. The only feasible axioms for it would be has some energy transformation unit (parent of power generating unit and heat generating unit) and has some grid component. What's the point in having this class if we don't use it for anything?

[l-emele]

I agree on the following definition proposals:

• A heat transfer unit is an energy transformation unit that can contain a heater or a heat exchanger.
• A boiler is a heater that increases the thermal energy of fluids.
• A combustion-based heater is a heater that increases the thermal energy using combustion.
• An electrical heater is a heater that increases the thermal energy using electric energy.
• A heat plant is an energy transformation unit consisting of heat generating units and a grid component that feeds thermal energy into a heating grid.

I suggest to extend the following definition:

• A heat generating unit is an energy transformation unit that contains a heat exchanger or heater.

I don't see a clear reason yet why to change the existing classes combined heat and power plant and combined heat and power generating unit.

[0UmfHxcvx5J7JoaOhFSs5mncnisTJJ6q]

I'm puzzled.

• A heat transfer unit is an energy transformation unit that can contain a heater or a heat exchanger.

Heat transfer currently is defined as energy transfer with both inputs and outputs of thermal energy. Should a heat transfer unit implement heat transfer? What's the heater doing there?

• A heat generating unit is an energy transformation unit that contains a heat exchanger or heater.

Good point.

I don't see a clear reason yet why to change the existing classes combined heat and power plant and combined heat and power generating unit.

Some measure of orthogonality between power, heat, and combined heat and power plants. But it's not necessary.

[l-emele]

Seems, I read over the a heater or part in heat transfer unit. Of course, that should be deleted. Anyway, we should make heat transfer unit a subclass of heat generating unit. Something like: A heat transfer unit is an heat generating unit that contains a heat exchanger. Axioms:

• 'heat generating unit' 'has part' some (heater or 'heat exchanger')
• 'heat transfer unit' ('has part' some 'heat exchanger') and not ('has part' some heater))

[Alex2448]

To summarize the discussion: you think I should rename heat transfer unit to heat generating unit to distinguish from heat transfer process, as far as I understand it. Then we will not need heat transfer unit anymore I think, @l-emele.

[l-emele]

If heat transfer unit is not needed anymore we do not need to include this.

[Alex2448]

To summarize the discussion:

• rename heat transfer unit to heat generating unit to distinguish from heat transfer process, as far as I understand it
• have combined heat and power plant parallel to heat plant and power plant as a subclass of energy transformation unit

[Alex2448]

I discussed it with Christoph and Beneharo, and we decided to implement it like you suggested @l-emele, with both heat transfer unit and heat generating unit.

Further, since there is no consensus about the geothermal issue, I will open a new issue about that and implement the rest of this issue.

[l-emele]

I am okay if you implement both heat generating unit and heat transfer unit.

Some suggestions and comments regarding your geothermal concepts:

• geothermal heat unit: Small improvement: A geothermal heat unit is a heat transfer unit ~using geothermal heat~ that uses geothermal energy as source. We call the energy geothermal energy and should use that in the definition. Further we are aiming for definitions with the pattern A is a B that C.
• geothermal heat plant: A geothermal heat plant is a heat plant that has geothermal heat units as parts. I agree with this definition.
• geothermal well system: A geothermal well system is a geothermal heat plant that has geothermal heat units as parts. That is basically the same definition as geothermal heat plant. What differentiates a geothermal well system from other geothermal heat plants?
• geothermal collector: A geothermal collector is a heat exchanger that uses thermal energy to convert it into heat and consists of plastic pipes laid horizontally in the ground. There are a couple of problems with this definition proposal: First, in my understanding thermal energy and heat are the same. Second, according to our definitions of geothermal energy[^1] and ambient thermal energy[^2], subsurface collectors do not collect geothermal energy but ambient thermal energy. Thus I would avoid having the word "geothermal" in the label here. So I suggest the following definition: A subsurface collector is a heat exchanger that transfers ambient thermal energy. It consists of plastic pipes laid horizontally.
• downhole heat exchanger: A downhole heat exchanger is a heat exchanger that uses thermal energy to convert it into heat and consists of plastic pipes installed vertically or inclined in a borehole. Again, here I suggest a rephrasing: A downhole heat exchanger is a heat exchanger that transfers ambient heat. It consists of plastic pipes installed vertically or inclined in a borehole.

[^1]: Geothermal energy is thermal energy that is released from within the earth's crust. [^2]: Ambient thermal energy is thermal energy that is stored in the ambient air, beneath the surface of solid earth or in surface water. It is captured by heat pumps.

Regarding the solar concepts:

• solar heat unit: I suggest to add the link to the solar thermal collector: A solar heat unit is a heat transfer unit ~using solar thermal energy~ that has a solar collector. This follows the structure of heat transfer unit, which also mentions the involved heater.
• solar heat plant: I basically agree to that very generic definition. But even aware what we mean here in real life? In my understanding that would be something like a field solarthermal collector system that is connected to a district heating grid. Do you have the same understanding here?
• tube collector: This could be shortened and a bit rephrased:A tube collector is a solar thermal collector that ~uses~ consists of tubes ~to absorb solar radiation to convert into thermal energy~. It does the same as the general solar thermal collector, it is only a technical detail. So no need to repeat what is already covered by the parent class. Further, the tube are the collector, that is clearer with my rephrasing.
• flat-plate collector: Same as above: A flat-plate collector is a solar thermal collector that ~uses~ consists of flat-plates to absorb solar radiation to convert into thermal energy.

While talking about solar, I am thinking of the existing solar thermal collector class: A solar thermal collector is a heater that ~absorbs solar radiation to convert it into heat~ converts solar energy to solar thermal energy.

Sorry, this comment has gotten a bit long...

[Alex2448]

@l-emele thanks for the comments and suggestions!

• Regarding the geothermal well system: that is exactly the problem. The only difference is the depth on where this is installed and I do not quite know how to model depth devision since everything is still in the crust and we should avoid hard numbers. (I explained it better in some comments above in this issue and also in the initial description of the issue).

• Regarding solar heat plant: yes this is also my understanding. Maybe I can specify it more like:

  • A solar heat plant is a heat plant that has solar heat units as parts and consists of solar thermal collectors.

I agree with the rest of your suggestions.

[l-emele]

The only difference is the depth on where this is installed and I do not quite know how to model depth devision since everything is still in the crust and we should avoid hard numbers. (I explained it better in some comments above in this issue and also in the initial description of the issue).

If we are not able to differentiate it from an other class, than we should not include it.

A solar heat plant is a heat plant that has solar heat units as parts and consists of solar thermal collectors.

The solar unit heat has solar thermal collectors as parts. The solar heat plant has solar heat units as parts. Therefore, every solar heat plant has also solar thermal collectors as parts. We don't need to repeat that in the definition.

[Alex2448]

Currently, the PR#1360 does not implement the geothermal well system, geothermal collector and downhole heat exchanger. For these, see Issue#1361.

[Alex2448]

I opened a new discussion on solar thermal power plant in Issue#1378 and do not implement this in PR#1360.

[Alex2448]

I opened a new discussion on solar thermal power plant in Issue#1378 and do not implement this in PR#1360.

I added solar heat plant and solar heat unit now in PR#1360.