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ALLSHIFT/docs/04-simulations/pem-electrolyser-and-fuel-cell-models.md
pepe 72dd781dbc Organize documentation into docs/ and superseded/ 
Audit every document in the repository, convert the non-markdown ones into
markdown reports, and split current documentation from outdated material.

docs/ — 31 markdown documents in seven numbered sections. Twenty are new
reports generated from .docx / .pdf / .xlsx / .mlx / .m sources that were
previously unreadable in the browser and undiffable in git. Each report
carries a provenance block (source path, format, MD5) and links back to its
original; all 13 recorded checksums verify against the files on disk.
Machine-extraction losses (PDF table column interleaving, Word OMML
equations, embedded figures) are called out explicitly rather than silently
smoothed over.

superseded/ — outdated material with a documented reason per entry:
two byte-identical ClickUp re-exports, an older revision of the BIDMC/UCSD
energy-flow doc (the retained copy adds the SoC Violation Rate KPI), a
duplicate of Shift input data.docx, the May 2026 simulation plan, the
root PV+Battery.md now covered by a fuller report, GitHub's stock
demo-repository template, and a zero-byte placeholder. Its README also
records what was deliberately NOT retired and why — the "Old Frameworks"
and "Old Simulations" folders hold unique Simulink revisions, and
"Big Ugly Folder" holds the only copy of framework revision 1.3.

Findings worth flagging, all documented in the reports:
- Simulink lineage recovered from each .slx's internal coreProperties.xml
  revision counter. The current model is
  Current Framework/Bobert0206_Initial_Simulation_Framework.slx (rev 2.7);
  the top-level copy is rev 1.3, five revisions behind.
- Simulations/Constants.m is a truncated byte-prefix of the Current
  Framework copy, silently missing H2_leak, H2_cap and E_H2_vol_h.
- The PEM electrolyser and fuel cell are unmodified MathWorks Simscape
  examples still at vendor defaults; the "10x bigger" sizing TODO recorded
  in Constants.m was never carried out.
- controller-claude.m does not compile — undefined P_Electro_max, outputs
  unassigned on several paths.
- The specification set uses two incompatible variable naming conventions
  and disagrees on action-space size (5 vs 16).
- MA_hourly_load.csv (13.7 MB) is the same 35,040 rows as 89993-0.parquet
  (2.4 MB).
- Clinical data is the MIMIC-IV *demo* (ODbL, 100 patients), not full
  MIMIC-IV — redistributable, but the licence and citation are unrecorded.

Housekeeping: untrack 21 Simulink build artefacts (slprj/, *.slxc) and add
ignore rules for them. Root README rewritten around the new layout.

Recruitment notes naming individual candidates are excluded from version
control via .gitignore rather than committed; the generic question template
is kept in docs/07-team-and-operations/.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-07-25 21:20:33 -07:00

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# PEM Electrolyser and Fuel Cell Models (MathWorks Simscape examples)
> **Markdown report of non-markdown source files.**
>
> | | |
> |---|---|
> | **Sources** | `Simulations/Ready Made PEM Electrolyzer/` · `Simulations/Ready Made PEM fuel cell/` · duplicated in `Simulations/Big Ugly Folder/` |
> | **Origin** | **MathWorks Simscape shipped examples**, obtained via `openExample(...)` |
> | **Licence** | © 2020–2024 The MathWorks, Inc. — see [Provenance](#provenance-and-licensing) |
> | **Status** | Current — but **still at vendor default parameters** |
> | **Report generated** | 2026-07-25 |
## Provenance and licensing
> [!WARNING]
> **This is unmodified third-party code.** Every `.m` and `.ssc` file in both folders carries a
> MathWorks copyright line; not one carries SHIFT attribution. Unlike the
> [EST model](existing-est-model.md) — which ships its MIT LICENSE and upstream URL — this
> vendored code is **marked nowhere in the repository**.
```
Ready Made PEM Electrolyzer/Electrolyzer.ssc:9 % Copyright 2021-2024 The MathWorks, Inc.
Ready Made PEM Electrolyzer/PEMElectrolysisSystemExample.m:57 % Copyright 2021 The MathWorks, Inc.
Ready Made PEM Electrolyzer/PEMElectrolysisSystemParameters.m:6 % Copyright 2021 The MathWorks, Inc.
Ready Made PEM fuel cell/FuelCell.ssc:10 % Copyright 2020-2024 The MathWorks, Inc.
Ready Made PEM fuel cell/PEMFuelCellSystemExample.m:64 % Copyright 2020-2021 The MathWorks, Inc.
Ready Made PEM fuel cell/PEMFuelCellSystemParameters.m:6 % Copyright 2020 The MathWorks, Inc.
…and 8 more Plot*.m files, all MathWorks
```
How they were obtained is recorded only as a comment in `Constants.m`:
```matlab
%openExample('simscape/PEMElectrolysisSystemExample')
%openExample('simscape/PEMFuelCellSystemExample')
```
**Recommended:** add a `PROVENANCE.md` to each folder stating that the contents are unmodified
MathWorks Simscape examples retrieved via `openExample`, and that redistribution is governed by
the MathWorks licence terms.
## The unfinished sizing work
`Constants.m` records the requirement and the plan, verbatim:
> `%Ready made electrolyser -`
> `%Good news: it has a solar profile.`
> `%Bad news: random constants - we want it at 128m3 hydrogen production a day`
> `%I have attempted to find volume via the volumetric flow rate, however this`
> `%uses "standard conditions". THIS BRINGS IT TO 12.8m3, JUST ADJUST (power?)`
> `%SO ITS 10 TIMES BIGGER AND WE ARE GOOD!`
>
> `%openExample('simscape/PEMFuelCellSystemExample')`
> `%This one is also PEM so it should work?`
>
> `%To do: Check if PEM is ok, change parameters for electrolyzer so that`
> `%production is exactely 10times bigger, adjust fuel cell, create grid,`
> `%ensure its power output is appropriate`
> [!IMPORTANT]
> **That TODO has not been carried out.** The parameter files are still at MathWorks demo
> defaults:
>
> - The electrolyser's 24-hour `solar_profile_power` still peaks at exactly **100 kW** — the
> vendor's round demo number, not a SHIFT-derived profile.
> - The fuel cell still loads **`PEMFuelCellSystemDriveCycle.mat`** — an *automotive drive
> cycle*, wholly inappropriate for a hospital microgrid.
>
> **No SHIFT-specific hydrogen system parameterisation exists anywhere in this tree**, despite
> `Constants.m` recording the requirement since the earliest revision. This is the single
> largest gap between the [simulator specification](../02-specifications/simulator-io-interface.md)
> and the models that are supposed to implement it.
Note also that the "just multiply by 10" approach to sizing is recorded as an unverified
assumption (*"This one is also PEM so it should work?"*), and that scaling a Simscape
electrolyser's hydrogen output by 10× is not achieved by scaling power alone — cell count,
active area, and current density all enter.
## Electrolyser parameters
`PEMElectrolysisSystemParameters.m` — 71 lines, 11,972 B, MD5 `7871b9ab`. Byte-identical in
`Ready Made PEM Electrolyzer/` and `Big Ugly Folder/`.
### Environment
| Parameter | Value | Unit |
|---|---:|---|
| `env_p` | 0.101325 | MPa |
| `env_T` | 20 | °C |
### Solar profile (24 h)
| Parameter | Value | Unit |
|---|---|---|
| `solar_profile_time` | `(0:23)' * 3600` | s |
| `solar_profile_power` | `[0 0 0 0 0 0 0.572 13.1 44.9 74.5 96.4 100 97.5 89.5 65.8 34.0 7.61 0 0 0 0 0 0 0]'` | kW |
### Stack
The comment header in the source says *"Fuel cell stack"* — a MathWorks copy-paste artefact in
the *electrolysis* file.
| Parameter | Value | Unit | Description |
|---|---:|---|---|
| `stack_num_cells` | 50 | – | Number of cells |
| `stack_area` | 280 | cm² | Cell area |
| `stack_t_membrane` | 125 | µm | Membrane thickness |
| `stack_t_gdl_A` | 25 | µm | Anode gas diffusion layer thickness |
| `stack_t_gdl_C` | 250 | µm | Cathode gas diffusion layer thickness |
| `stack_w_channels` | 1 | cm | Gas channel width and height |
| `stack_num_channels` | 8 | – | Gas channels per cell |
| `stack_io` | 1e-04 | A/cm² | Exchange current density |
| `stack_alpha` | 0.7 | – | Charge transfer coefficient |
| `stack_D_gdl_A` | 0.07 | cm²/s | Water diffusivity in anode GDL |
| `stack_D_gdl_C` | 0.07 | cm²/s | Water diffusivity in cathode GDL |
| `stack_membrane_rho` | 2000 | kg/m³ | Density of dry membrane |
| `stack_membrane_MW` | 1.1 | kg/mol | Equivalent weight of dry membrane |
| `stack_mea_rho` | 1800 | **kg/s** *(sic)* | Overall density of MEA — vendor unit typo, should be kg/m³ |
| `stack_mea_cp` | 870 | J/(kg·K) | Overall specific heat of MEA |
### Piping and heat exchanger
| Parameter | Value | Unit | Description |
|---|---:|---|---|
| `water_pipe_D` | 0.01 | m | Water pipe diameter |
| `gas_pipe_D` | 0.01 | m | Gas pipe diameter |
| `exchanger_L` | 1 | m | Overall radiator length |
| `exchanger_W` | 0.025 | m | Overall radiator width |
| `exchanger_H` | 0.5 | m | Overall radiator height |
| `exchanger_N_tubes` | 25 | – | Number of coolant tubes |
| `exchanger_tube_H` | 0.0015 | m | Height of each coolant tube |
| `exchanger_fin_spacing` | 0.002 | – | Fin spacing |
| `exchanger_eta_fin` | 0.7 | – | Fin efficiency |
Derived quantities computed in the script: `exchanger_gap_H`, `exchanger_air_area_primary`,
`exchanger_N_fins`, `exchanger_air_area_fins`, `exchanger_tube_Leq`.
## Fuel cell parameters
`PEMFuelCellSystemParameters.m` — 94 lines, 12,709 B, MD5 `6eaf6bf3`. Byte-identical in
`Ready Made PEM fuel cell/` and `Big Ugly Folder/`. Line 8 executes
`load PEMFuelCellSystemDriveCycle.mat` (13,667 B).
### Environment
| Parameter | Value | Unit |
|---|---:|---|
| `env_p` | 0.101325 | MPa |
| `env_T` | 20 | °C |
| `env_RH` | 0.5 | – (relative humidity) |
| `env_yO2` | 0.21 | – (oxygen mole fraction) |
### Fuel tank
| Parameter | Value | Unit |
|---|---:|---|
| `tank_p` | 70 | MPa |
| `tank_yH2` | `1 − 3e-4` | – (hydrogen mole fraction) |
| `tank_V` | 120 | L |
> `tank_V = 120 L` at 70 MPa is an **automotive** hydrogen tank. The
> [project spec](../02-specifications/simulator-io-interface.md#13-hydrogen-tank) calls for
> **up to 200 kg across two tanks** — roughly three orders of magnitude larger. Another
> consequence of the untouched vendor defaults.
### Stack
| Parameter | Value | Unit | Description |
|---|---:|---|---|
| `stack_num_cells` | **400** | – | Number of cells (vs. 50 in the electrolyser) |
| `stack_area` | 280 | cm² | Cell area |
| `stack_t_membrane` | 125 | µm | Membrane thickness |
| `stack_t_gdl` | 250 | µm | Gas diffusion layer thickness |
| `stack_w_channels` | 1 | cm | Gas channel width/height |
| `stack_num_channels` | 8 | – | Gas channels per cell |
| `stack_io` | 1e-04 | A/cm² | Exchange current density |
| `stack_iL` | 1.4 | A/cm² | Limiting current density |
| `stack_alpha` | 0.7 | – | Charge transfer coefficient |
| `stack_D_gdl` | 0.07 | cm²/s | Water diffusivity in GDL |
| `stack_membrane_rho` | 2000 | kg/m³ | Density of dry membrane |
| `stack_membrane_MW` | 1.1 | kg/mol | Equivalent weight of dry membrane |
| `stack_mea_rho` | 1800 | **kg/s** *(sic)* | Vendor unit typo, should be kg/m³ |
| `stack_mea_cp` | 870 | J/(kg·K) | Overall specific heat of MEA |
### Gas tubes and coolant
| Parameter | Value | Unit | Description |
|---|---:|---|---|
| `anode_tube_D` | 0.01 | m | Hydrogen tube diameter |
| `cathode_tube_D` | 0.05 | m | Air tube diameter |
| `coolant_w_channels` | 1 | cm | Coolant channel width/height |
| `coolant_num_passes` | 12 | – | Coolant channel passes per layer |
| `coolant_num_layers` | 20 | – | Coolant layers in stack |
| `coolant_tube_D` | 0.05 | m | Coolant tube diameter |
### Radiator
| Parameter | Value | Unit | Description |
|---|---:|---|---|
| `radiator_L` | 1 | m | Overall radiator length |
| `radiator_W` | 0.025 | m | Overall radiator width |
| `radiator_H` | 0.5 | m | Overall radiator height |
| `radiator_N_tubes` | 25 | – | Number of coolant tubes |
| `radiator_tube_H` | 0.0015 | m | Height of each coolant tube |
| `radiator_fin_spacing` | 0.002 | – | Fin spacing |
| `radiator_eta_fin` | 0.7 | – | Fin efficiency |
| `radiator_t_wall` | 1e-4 | m | Material thickness |
| `radiator_rho` | 2700 | **kg/s** *(sic)* | Vendor unit typo, should be kg/m³ (2700 = aluminium) |
| `radiator_cp` | 910 | J/(kg·K) | Radiator material specific heat |
### Compressor map
| Parameter | Value | Unit |
|---|---|---|
| `comp_p_ratio_TLU` | `[1; 1.25; 1.5; 1.75; 2]` | – (pressure ratio) |
| `comp_rpm_TLU` | `[0, 1800, 3600]` | rpm |
```matlab
comp_mdot_corr_TLU = [
0, 0.05, 0.1;
0, 0.0375, 0.075;
0, 0.025, 0.05;
0, 0.0125, 0.025;
0, 0, 0] * 4; % [kg/s] Corrected mass flow rate table
```
## Gas properties (shared by both files)
| Gas | `_R` [J/(kg·K)] | `_D` [mm²/s] |
|---|---:|---:|
| H₂ | 4124.48151675695 | 74 |
| O₂ | 259.836612622973 | 18 |
| N₂ | 296.802103844292 | — |
Each gas also carries 52-element lookup vectors sharing the temperature grid
`_T = [-56.55, -50:10:-10, -5:1:5, 10:10:350]` °C, with `_h` in kJ/kg (specific enthalpy),
`_mu` in µPa·s (dynamic viscosity), and `_k` in mW/(m·K) (thermal conductivity).
## What differs between the two models
The two parameter files share identical gas property tables and identical membrane/MEA
parameters. The substantive differences:
| Aspect | Electrolyser | Fuel cell |
|---|---|---|
| `stack_num_cells` | 50 | **400** |
| Limiting current density | — | `stack_iL = 1.4 A/cm²` |
| Gas diffusion layer | Split anode/cathode (`_A` 25 µm / `_C` 250 µm) | Single `stack_t_gdl` = 250 µm |
| Fuel storage | — | `tank_*` block, 120 L @ 70 MPa |
| Air handling | — | `env_RH`, `env_yO2`, compressor map |
| Cooling | Heat exchanger | Coolant channels + radiator |
| Drive input | 24 h solar profile | Automotive drive cycle `.mat` |
## Supporting scripts
Both folders ship MathWorks' plotting and example scripts, all copyright MathWorks:
| Electrolyser | Fuel cell |
|---|---|
| `PEMElectrolysisSystemExample.m` | `PEMFuelCellSystemExample.m` |
| `PEMElectrolysisSystemPlot1IV.m` | `PEMFuelCellSystemPlot1IV.m` |
| `PEMElectrolysisSystemPlot2Power.m` | `PEMFuelCellSystemPlot2Power.m` |
| `PEMElectrolysisSystemPlot3Hydrogen.m` | `PEMFuelCellSystemPlot3Efficiency.m` |
| | `PEMFuelCellSystemPlot4T.m` |
| | `PEMFuelCellSystemPlot5Energy.m` |
The `Plot*.m` files carry polished vendor documentation citing textbook figures — for example
*"The theoretical maximum efficiency for a PEM fuel cell is 83%. However, actual efficiency is
around 60% due to internal losses"*, which lines up with the 40% fuel-cell loss figure in
[AI Efficiency Improvements](../01-project/ai-efficiency-improvements.md).
The `.ssc` component sources use the Simscape `foundation.moist_air.moist_air` and
`foundation.thermal_liquid.thermal_liquid` domains.
## Related
- [Simulink Model Inventory](simulink-model-inventory.md) — including the `Constants.m` staleness
- [Simulator I/O Interface §1.1–1.3](../02-specifications/simulator-io-interface.md#11-electrolyser) — the parameters these should match
- [UCSD Equipment Manual](../03-energy-management/ucsd-equipment-manual.md) — real-world PEM electrolyser specifications
- [AI Efficiency Improvements](../01-project/ai-efficiency-improvements.md) — the loss targets
- [Existing EST Model](existing-est-model.md) — the other vendored subtree
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