# RL State Variables

> **Markdown report of a non-markdown source document.**
>
> | | |
> |---|---|
> | **Source** | [`docs/_originals/STATE VARIABLES AND DESCRIPTIONS.docx`](../_originals/STATE%20VARIABLES%20AND%20DESCRIPTIONS.docx) |
> | **Format** | Microsoft Word (.docx), 14.7 kB |
> | **MD5** | `59dde2384627aa8cdc0412ed6d7f589f` |
> | **Owner** | AI & Control Systems cluster |
> | **Status** | Current — but see [Naming mismatch](#naming-mismatch-with-the-simulator-io-contract) |
> | **Report generated** | 2026-07-25 |

## What this document is

The observation space for the reinforcement-learning controller: everything the agent is
allowed to *see* at each timestep. It is the counterpart to
[RL Action Variables](rl-action-variables.md) (what the agent may *do*) and
[RL Reward Function](rl-reward-function.md) (how it is *scored*).

Thirty-two variables in eight groups. The source document gives a name and a one-line
description for each; it does **not** specify units, ranges, or datatypes — those are
implied at best. Adding them is the obvious next revision.

## State variables

### Photovoltaic array

| Variable | Description |
|---|---|
| `PV_Generation` | Current electrical power produced by the solar panels. |
| `Solar_Irradiance` | Amount of sunlight hitting the panels (W/m²). |
| `PV_Temperature` | Panel temperature affecting efficiency. |
| `PV_Efficiency` | Conversion efficiency of the PV array at the current moment. |

### Battery

| Variable | Description |
|---|---|
| `Battery_SOC` | Battery state of charge (%) indicating energy stored. |
| `Battery_Current` | Charge/discharge current flowing through the battery. |
| `Battery_Voltage` | Terminal voltage of the battery pack. |
| `Battery_Temperature` | Battery temperature affecting performance and lifespan. |

### Electrolyser

| Variable | Description |
|---|---|
| `Electrolyzer_Power` | Electrical power supplied to the electrolyzer. |
| `Electrolyzer_H2_ProductionRate` | Amount of hydrogen being produced per unit time. |
| `Electrolyzer_WaterLevel` | Water reservoir level needed for electrolysis. |
| `Electrolyzer_Temperature` | Stack temperature affecting efficiency and safety. |
| `Electrolyzer_StackHealth` | Degradation/health level of the electrolyzer stack. |

### Hydrogen storage

| Variable | Description |
|---|---|
| `HydrogenTank_Level` | Current amount of hydrogen stored in the tank. |
| `HydrogenTank_Pressure` | Internal pressure of the hydrogen storage tank. |
| `HydrogenTank_Temperature` | Tank temperature affecting pressure and safety. |

### Fuel cell

| Variable | Description |
|---|---|
| `FuelCell_Power` | Current electrical power produced by the fuel cell. |
| `FuelCell_Temperature` | Fuel cell stack temperature. |
| `FuelCell_H2_ConsumptionRate` | Rate at which the fuel cell consumes hydrogen. |
| `FuelCell_StackHealth` | Degradation/health of the fuel cell stack. |

### Grid

| Variable | Description |
|---|---|
| `Grid_Status` | Whether the grid is online/offline/faulted. |
| `Grid_Price` | Current real-time electricity price from the grid. |
| `Grid_Availability` | Whether grid import or export is allowed at the moment. |

### Hospital load

| Variable | Description |
|---|---|
| `Hospital_Load` | Total electrical demand of the hospital. |
| `Critical_Load` | Portion of the load that must always be powered. |
| `NonCritical_Load` | Flexible load that can be shed or shifted. |
| `Predicted_Load` | Forecasted load in the near future. |

### Environment and calendar

| Variable | Description |
|---|---|
| `Ambient_Temperature` | Outside temperature affecting PV, battery, and loads. |
| `Ambient_Humidity` | Humidity affecting cooling and equipment performance. |
| `TimeOfDay` | Current hour used for daily patterns in generation/load. |
| `DayType` | Whether it is a weekday, weekend, or holiday (affects load patterns). |

## Naming mismatch with the simulator I/O contract

This document and the [Simulator I/O Interface](simulator-io-interface.md) describe the same
system with **two different naming conventions**, and neither references the other:

| Concept | This document | Simulator I/O sheet |
|---|---|---|
| Battery state of charge | `Battery_SOC` (%) | `SoC(t)` (0–1) |
| PV power | `PV_Generation` | `P_PV_available(t)` / `P_PV_used(t)` |
| Hydrogen stored | `HydrogenTank_Level` | `H2_level(t)` (mol or kg) |
| Critical demand | `Critical_Load` | `L_crit(t)` (W) |
| Grid availability | `Grid_Availability`, `Grid_Status` | `grid_on(t)` (1/0) |

The simulator sheet also **omits** several states listed here — stack health, water level,
humidity, and all four component temperatures — because it assumes an isothermal tank and no
degradation model (both flagged as open questions in that document).

Conversely this document lists no `DayType` or `TimeOfDay` equivalent in the simulator outputs.

**Neither document is wrong; they are unreconciled.** Before the environment is coded, one
naming convention and one authoritative variable set has to win. The Simulator I/O sheet is the
more rigorous artefact (it has units, ranges, sign conventions, and an explicit power-balance
invariant), so it is the natural base — but it needs the health/temperature states from this
document if degradation or thermal effects are to be modelled at all.

## Related

- [RL Action Variables](rl-action-variables.md) — the action space
- [RL Reward Function](rl-reward-function.md) — the reward terms
- [Simulator I/O Interface](simulator-io-interface.md) — the typed simulator contract
- [Rule-Based Controller](rule-based-controller.md) — the baseline policy this agent must beat