Feature/rtd component models

[SabineHaas]

Adress #779

Changes proposed in this pull request:

• Update component models section in RTD with information on energy storages, heat pumps and HVAC.

Questions:

• (Update --> moved to C-rate is not used in D1.storage_fix() only in D1.storage_optimize() #798) [Energy Storage] As I understand from D1.storage_fix() here and here maximum discharge and charge possible in one time step for storage with fixed capacity.
  In contrast, for a storage with optimized cap (D1.storage_optimize() a c-rate can be given, see here. (From the Oemof.solph documentation I also only see the usage of a c-rate for investment optimization.) Is this right and is this how it should be in MVS?
• (Update --> moved to Efficiency of transformers with two inputs should be assigned to input flows #799) [HVAC] in case of non air-sourced device, according to oemof documentation two input busses are needed and efficiencies are assigned to input busses. This could be easily implmented as we allow either multiple input OR multiple output busses see D1.transformer_constant_efficiency_optimize().
  This accounts as well for other conversion technologies with two inputs.

todos

• schedule a meeting with @smartie2076 about first two questions
• write issue: later add link to pvcompare parameter research on heat pumps and TES (costs, temperatures, quality grade etc.)

The following steps were realized, as well (if applies):

• ❌ Use in-line comments to explain your code
• ❌ Write docstrings to your code (example docstring)
• ❌ For new functionalities: Explain in readthedocs
• ❌ Write test(s) for your new patch of code (pytests, assertion debug messages)
• Update the CHANGELOG.md
• ❌ Apply black (black . --exclude docs/)
• ❌ Check if benchmark tests pass locally (EXECUTE_TESTS_ON=master pytest)

Please mark above checkboxes as following:

• Open
• Done

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_{For more information on how to contribute check the CONTRIBUTING.md.}

[SabineHaas]

@smartie2076

I'm not sure about the required level of detail here. Maybe you can check whether you agree with the level of detail checking my first commit on storages (H2 tba).

[smartie2076]

* [ ]  [Energy Storage] As I understand from `D1.storage_fix()` [here](https://github.com/rl-institut/multi-vector-simulator/blob/454171f449538c451377a278bfd63254ac45c44f/src/multi_vector_simulator/D1_model_components.py#L570) and [here](https://github.com/rl-institut/multi-vector-simulator/blob/454171f449538c451377a278bfd63254ac45c44f/src/multi_vector_simulator/D1_model_components.py#L578) maximum discharge and charge possible in one time step for storage with fixed capacity.
  In contrast, for a storage with optimized cap (`D1.storage_optimize()` a c-rate can be given, see [here](https://github.com/rl-institut/multi-vector-simulator/blob/454171f449538c451377a278bfd63254ac45c44f/src/multi_vector_simulator/D1_model_components.py#L655-L658). (From the Oemof.solph [documentation](https://oemof-solph.readthedocs.io/en/latest/usage.html#genericstorage-component) I also only see the usage of a c-rate for [investment optimization](https://oemof-solph.readthedocs.io/en/latest/usage.html#using-an-investment-object-with-the-genericstorage-component).) Is this right and is this how it should be in MVS?

I am not sure about this at this very moment. We can schedule a meeting to discuss this and the implications.

* [ ]  [HVAC] in case of non air-sourced device, according to [oemof documentation ](https://oemof-solph.readthedocs.io/en/latest/usage.html#transformer-basic)two input busses are needed and efficiencies are assigned to input busses. This could be easily implmented as we allow either multiple input OR multiple output busses see `D1.transformer_constant_efficiency_optimize()`.
  This accounts as well for other conversion technologies with two inputs.

But in that case, is it really an air-sourced device? If you do not care about how much energy you "extract" from air, why measure it by connecting it to the inputs?

For two in/outputs, we dont have benchmark tests yet, so maybe we should have that as a milestone. I guess that means that CHP can not be simulated right now...

[smartie2076]

"specific type of SHS"?

[SabineHaas]

stratified thermal energy storage is a SHS, but specific

[smartie2076]

In the OGs, SHS are "solar home systems", so that was my confusion.

[smartie2076]

@smartie2076

I'm not sure about the required level of detail here. Maybe you can check whether you agree with the level of detail checking my first commit on storages (H2 tba).

I like the level of detail.

[SabineHaas]

I am not sure about this at this very moment. We can schedule a meeting to discuss this and the implications.

will do 👍

* [ ]  [HVAC] in case of non air-sourced device, according to [oemof documentation ](https://oemof-solph.readthedocs.io/en/latest/usage.html#transformer-basic)two input busses are needed and efficiencies are assigned to input busses. This could be easily implmented as we allow either multiple input OR multiple output busses see `D1.transformer_constant_efficiency_optimize()`.
  This accounts as well for other conversion technologies with two inputs.

But in that case, is it really an air-sourced device? If you do not care about how much energy you "extract" from air, why measure it by connecting it to the inputs?

No, this is the case for non air source devices.

For two in/outputs, we dont have benchmark tests yet, so maybe we should have that as a milestone. I guess that means that CHP can not be simulated right now...

mhh :/ will this be a problem for the beta release?