Site simulator: thermal plant, facility presets, and live schematic

[frahlg]

Summary

This is now a site simulator, not only a bag of independent devices.

Pick a facility on the dashboard (house ASHP/GSHP, apartment, or PV+battery). That instantiates a physics plant and the Modbus facades an EMS (FTW/FTV) talks to. The site clock is the only integrator. Devices do not invent power; they project what the plant just solved.

EMS --Modbus--> Sungrow hybrid + generic heat pump + SDM630
                   ▲
                   │ site tick
            plant.Model (NativeSite; optional Site4.fmu for AC bus)
            P_grid + P_pv + P_batt + P_house + P_hp + P_ev = 0
            C·dT_in/dt = Q_hp_space + Q_solar + Q_int − Q_loss

The Site plant band is a live schematic: green electrical flows (Lua sign convention), orange heat, indoor/DHW temperatures, occupancy, SG Ready.

How to use it: docs/SITE_SIMULATOR.md. Bus sketch: docs/SITE_PLANT_SKETCH.md.

Facilities

Preset	Plant
house-ashp	Nordic house, air-source HP, DHW, 8 kW PV + 10 kWh
house-gshp	Same house, ground-source HP (stable winter COP)
apartment-ashp	Heavier envelope, larger ASHP, modest PV
pv-battery	Occupancy plug loads only

POST /api/sites/{id}/facility with { "preset": "house-ashp" } creates the Sungrow + heat-pump devices if needed, sets scenario physical, and starts the clock.

Operating routines (not a full FTV stack, enough that the site feels occupied): occupancy plug loads and internal heat, heating curve + night setback, DHW draws, SG Ready 0–3.

Physics / Modelica

• Native Go (internal/plant) is the live thermal + electrical DAE.
• modelica/SiteEnergy.mo now has matching Building, HeatPump, DHWTank, HouseFacility.
• Site4.fmu stays the electrical FMI 2.0 slave (make fmu). A facility forces native so heat and electricity share one clock.

make fmu                     # omc → modelica/Site4.fmu
SITEPLANT_FMU=...            # or drop Site4.fmu in modelica/
SITEPLANT_NATIVE=1           # force Go

Lua drivers still poll Modbus, not HTTP.

API (OpenAPI + MCP + /docs updated together)

• GET /api/facilities
• GET|POST /api/sites/{id}/facility
• GET /api/sites/{id}/plant
• Simulator type heat_pump (holding 1100–1103 enable/setpoint/mode/SG Ready; inputs indoor/DHW/COP/…)

Wails: GetFacilities, ApplySiteFacility, GetSitePlant.

Checklist

• Tests pass locally (go test ./...)
• Thermal tests: ASHP heat+electric, GSHP winter COP, SG Ready block, enable-off, occupancy house load, 24 h indoor hold
• HTTP API change: openapi.json, internal/mcp/server.go, docs.html
• Commit subject uses a release prefix when this should ship (patch: / minor: / major:)