hems-core

The domain model every other crate in the hems workspace speaks: sites, assets, circuits, the 15-minute Europe/Berlin slot grid, measurements, and commands that must name their reason.

Facts, not rules. What a heat pump is lives here; whether it is a steuerbare Verbrauchseinrichtung under § 14a EnWG lives in hems-grid, and the regulatory vocabulary the two share — Fallgruppe, the Bundesland calendar, the market identifiers — comes from metering.

• 🧊 No I/O, no clock, no async — time is a parameter, so a winter day with a DST transition is a unit test.
• ➕ One sign convention — positive power flows into the thing measured, so grid == Σ assets holds site-wide and is testable.
• 🧾 Commands explain themselves — a Setpoint cannot exist without a Reason, and reasons carry an Authority that makes "the grid limit wins" a checked property rather than a convention.
• 🏠 The building is a store — a two-mass RC model discretised exactly by a matrix exponential, so the planner, its baseline and the simulator all step the same house and none of them can ring or diverge at a quarter-hour step. So is the hot-water tank: three hundred litres between 45 and 60 °C are five kilowatt-hours of heat that can be bought hours before they are used.
• 🔀 Wiring and mode are different questions — PhaseConnection is what a device is wired to, PhaseMode is what it is using right now. Answering the second with the first is how an 11 kW wallbox drawing symmetrically on three conductors acquires the 4,6 kVA limit a single-phase device is allowed.

use hems_core::prelude::*;

let limit = Setpoint::new(
    AssetId::new("wallbox-garage")?,
    Command::ConsumptionCeiling(Power::from_kw(4.2)),
    Reason::guard(GuardRule::Lpc),
    time::macros::datetime!(2026-01-15 17:04:00 UTC),
)?;
assert_eq!(limit.authority(), Authority::Guard);
# Ok::<(), Box<dyn std::error::Error>>(())

License

MIT OR Apache-2.0