Irradiance, irradiation, power density and energy density

[l-emele]

Description of the issue

The discussion in #362 has shown that irradiance and irradiation are useful concepts for our ontology

Ideas of solution

From discussion #362 :

• Irradiance is an instantaneous value and describes a power (Leistung) of solar rays on a defined area. The unit is usualy W/m².
• Irradiation is an enery, so power integrated over time. The unit are Wh/m². Irradiation defenitely needs a time step (see timestep, timehorizon, timeseries need new place and def #267) over which it has been recorded.

Originally posted by @carstenhoyerklick in #362 (comment)

Irradiance seams to be a specific kind of power density and irradiation an specific kind of energy density. So we should define the concepts of power density and energy density first and then use these definitions to define the concepts of irradiance and irradiation

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]

Some proposals:

Upper classes, I intentionally left the labels open:

• A is a quantity value that measures the power per area.
  has unit C
• D is a quantity value that measures the energy per area.
  has unit Joule per square metre

Those upper classes need

• C is unit that measures the power per surface area.
• `D is a unit that measures the energy per surface area.

Using the upper classes we can define:

• E is an A that measures the arriving solar power per area.
• F is an B that measures the arriving solar energy per area. F is usually measured or calculated for a time step.

I am unsure about the labels, but I have some suggestions:

• A and B could be labelled power density and energy density. However, these could be mixed up with their volumetric counterparts. So a better approach might be to label these areal power density resp. areal energy density and add power density and energy density only as alternative terms. With that second approach we are open to define e.g. a volumetric energy density later. Then both the areal energy density and the volumetric energy density would have the same alternative terms energy density showing that this term is ambiguous.
• C and D: following my preferences for A and B I would label these as areal power density unit and areal energy density unit.
• E and F: One option would be to use irradiance and irradiation. A second option would be to use something more systematic like areal solar power density and areal solar energy density. A combination is also possible by using one set of terms as labels and the second set as alternative terms. If so, I would prefer using (as they are more systematic) areal solar xyz density for the labels and using irradiance and irradiation for the the alternative terms. But I do not have strong feelings against doing it the other way round.

@stap-m and @carstenhoyerklick : What do you think?

[carstenhoyerklick]

Von: l-emele <[email protected]> Gesendet: Mittwoch, 25. November 2020 17:47 An: OpenEnergyPlatform/ontology <[email protected]> Cc: Hoyer-Klick, Carsten <[email protected]>; Mention <[email protected]> Betreff: Re: [OpenEnergyPlatform/ontology] Irradiance, irradiation, power density and energy density (#597) Some proposals: Upper classes, I intentionally left the labels open: * A is a quantity value that measures the power per area. has unit C * D is a quantity value that measures the energy per area. has unit Joule per square metre [CHK] This probably should be B? Those upper classes need * C is unit that measures the power per surface area. * `D is a unit that measures the energy per surface area. Using the upper classes we can define: * E is an A that measures the arriving solar power per area. * F is an B that measures the arriving solar energy per area. F is usually measured or calculated for a time step. I am unsure about the labels, but I have some suggestions: * A and B could be labelled power density and energy density. However, these could be mixed up with their volumetric counterparts. So a better approach might be to label these areal power density resp. areal energy density and add power density and energy density only as alternative terms. With that second approach we are open to define e.g. a volumetric energy density later. Then both the areal energy density and the volumetric energy density would have the same alternative terms energy density showing that this term is ambiguous. [CHK] We will probably need volumentric terms, e.g. to describe storage tanks. Therefore I support this. * C and D: following my preferences for A and B I would label these as areal power density unit and areal energy density unit. * E and F: One option would be to use irradiance and irradiation. A second option would be to use something more systematic like areal solar power density and areal solar energy density. A combination is also possible by using one set of terms as labels and the second set as alternative terms. If so, I would prefer using (as they are more systematic) areal solar xyz density for the labels and using irradiance and irradiation for the the alternative terms. But I do not have strong feelings against doing it the other way round. [CHK] Irradiance and Irradiation are shorter terms, but areal solar power/energy density describes it more precise. So the latter may be the more logic terms and irradiance and irradiation commonly used alternatives. @stap-m<https://github.com/stap-m> and @carstenhoyerklick<https://github.com/carstenhoyerklick> : What do you think? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#597 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ANW4YRCB63FY3DT5YSDV66LSRUYJZANCNFSM4T4VTTLA>.

[l-emele]

[CHK] This probably should be B?
Yes, sorry for that typo.

I think we have an agreement, as @stap-m gave some thumbs up.

@carstenhoyerklick : Do you want to try to implement this issue? Else I can do that.

[l-emele]

No reaction, so I'll implement now myself.