feat(stebbs): Enable multiple building archetypes (#360)

[sunt05]

Summary

This PR implements GH#360 - enabling multiple building archetypes in STEBBS.

Completed Phases

• Phase 1: Made nbtypes dynamic in Fortran

  • Changed from compile-time PARAMETER to runtime variable
  • Added nbtypes_max=10 as upper bound

• Phase 2a: Updated Fortran types for multi-archetype arrays

  • Added building_archetypes(:) allocatable array to SUEWS_SITE
  • Added sfr_bldg_arch(:) for archetype surface fractions
  • Updated allocation/deallocation routines

• Phase 2b: Added archetype initialisation loop in driver

  • Loop variable and initialisation in suews_ctrl_driver.f95

• Phase 3: Updated Python/Pydantic data model

  • Added sfr field to ArchetypeProperties
  • Added building_archetypes dict field to SiteProperties
  • Added validator for sfr sum == 1.0 and max 10 archetypes
  • Added effective_archetypes property and nbtypes property

• Phase 4: Extended DataFrame bridge for multi-archetype

  • Added indexed serialisation methods (to_df_state_indexed, from_df_state_indexed)
  • Store nbtypes and archetype_names in DataFrame

• Phase 5: Added per-archetype output variables

  • Added STEBBS_ARCHETYPE output group
  • Added generate_archetype_variables() function for dynamic variable generation

• Phase 6: Created tests and fixtures

  • 19 tests covering data model, validation, serialisation, output variables

Remaining Work (Future PRs)

• Fortran STEBBS physics loop with per-archetype calculations
• Area-weighted aggregation using DOT_PRODUCT pattern
• Integration tests with actual STEBBS simulations

Design Decisions

• Max archetypes: 10 (dynamically scalable via allocatable arrays)
• Per-archetype outputs: Opt-in via STEBBS_ARCHETYPE output group
• Output naming: {variable}_{archetype_name} format (e.g., Tair_ind_residential)
• Aggregation: Area-weighted using DOT_PRODUCT(flux_array, sfr_array) pattern

YAML Configuration Example

# Multi-archetype format
building_archetypes:
  residential:
    sfr: 0.6  # Surface fraction
    stebbs_Height: 8.5
    FootprintArea: 45.0
  commercial:
    sfr: 0.4
    stebbs_Height: 25.0
    FootprintArea: 500.0

# Single archetype (backwards compatible)
building_archetype:
  stebbs_Height: 10.0

Test plan

• All smoke tests pass (9/9)
• Multi-archetype unit tests pass (19/19)
• Backwards compatibility with single archetype

🤖 Generated with Claude Code

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[sunt05]

Hi @yiqing1021, please take a look at this and see whether the prototype aligns with our expectations.

[yiqing1021]

Hi Ting,

Thanks for adding the new STEBBS features — the prototype looks good and the approach is reasonable.

A few points I think we should plan to address in future work:

1. yaml inputs for multiple archetypes.
Although the building_archetypes array is set up to store multiple archetypes, the YAML currently provides only a single set of archetype inputs, which is then passed into SUEWS_cal_multitsteps(). We’ll likely need to extend the YAML structure so each archetype can be defined and ingested explicitly.

2. aggregated output.
If we configure STEBBS outputgroup to produce outputs aggregated across archetypes, we’ll probably need additional logic to perform that aggregation downstream. Also, some variables (e.g., wall/roof surface temperatures) are currently stored in the type file for STEBBS–SS coupling; we may need to adjust how these are stored so the aggregated outputs can be passed cleanly into other modules.

[sunt05]

Thanks for the review, Yiqing.

Re: YAML inputs for multiple archetypes

Agreed - the infrastructure is in place but YAML schema needs extending. The Pydantic model already supports building_archetypes: dict[str, ArchetypeProperties], so it's mainly a case of adding the YAML parsing layer.

Re: aggregated output

Just to clarify - the PR already provides per-archetype outputs (e.g., Tair_ind_residential, Qload_heating_commercial). Your point is about whether we also need aggregated (weighted-average) outputs for users who want a single representative value, correct?

For STEBBS-SS coupling, the current design stores per-archetype surface temperatures. If SS needs a single aggregated value, we'd compute the weighted average at the coupling interface. This keeps maximum flexibility internally.

Shall we merge this first and create follow-up issues to track the remaining work?

[sunt05]

To clarify scope: this PR establishes the infrastructure (data model, Fortran arrays, initialisation loop), while the actual per-archetype calculations and output generation are follow-up work.

Proposal: let's expand #360 with sub-issues to track the full feature:

1. Infrastructure for multiple archetypes (this PR)
2. YAML schema extension for multi-archetype input
3. Per-archetype STEBBS calculations and output

We can link this PR to close sub-issue 1, then work through the others. Thoughts? @yiqing1021

[yiqing1021]

Yes, I agree to merge this infrastructure for multi-archetype. Also we need to let @MatthewPaskin know this change because he designed the STEBBS structure.

[MatthewPaskin]

This looks good to me @yiqing1021 @sunt05 , however, where is the fraction for each archetype coming in? This has not previously been a parameter for STEBBS (YL correct me if I am wrong). There is however, the surface area and certain datasets contain the count of the archetype. I think a discussion may need to be had with Denise, Stefan and Sue with regarding how STEBBS aggregates across the different archetypes.

[sunt05]

Thanks both @yiqing1021 @MatthewPaskin - let's leave this open for now.

Good point about the fraction parameter, Matthew. The sfr field in this PR is a placeholder that we haven't fully thought through yet - it could represent surface area fraction, building count weighting, or something derived from external datasets. This needs discussion.

From a maintenance perspective, STEBBS is becoming a substantial component of SUEWS. Before we proceed further, I'd like to have a clearer picture of how STEBBS should integrate as an organic component - particularly around:

• Input structure (how archetypes are defined/sourced)
• Aggregation logic (how outputs combine across archetypes)
• Module coupling (STEBBS-SS interface)

Let's leave this to our next SUEWS catch-up.

[yiqing1021]

Thanks for these useful consideration, @MatthewPaskin ! This PR introduce a parameter “sfr_bldg_arch” for the aggregation, but currently not used. You are right, we should discuss how to do the aggregation of archetypes, but that likely sits outside SUEWS/STEBBS