Overview

What it is

OffshoreLH2 treats an offshore hydrogen project as one connected system rather than a set of separate spreadsheets. In every simulated hour, electricity, water, gaseous hydrogen and pathway-specific storage or cargo states move through explicit physical limits. Research-stage carrier studies can also include compressed-H₂ ship cargo or ammonia synthesis, storage and transport. Every run ends with conservation checks and an independent audit.

The same engine drives single simulations, sensitivity and uncertainty studies, multi-year comparisons and design optimization. You can use it through a desktop application, a command-line tool or a Python API.

Motivation

Why I built it

Offshore hydrogen systems are tightly coupled. Wind sets production, storage absorbs the mismatch, and waves decide when cargo can move. Annual averages hide those interactions, and paper-specific scripts are hard to reuse or check.

I wanted each new study to add to one tested model instead of starting another script, and every result to be traceable to its data, settings and software version. OffshoreLH2 began as the Python models behind my offshore-hydrogen studies and has grown into a general research platform.

OffshoreLH2 at a glance

v0.4.0-alpha.6

Physics core: C++20Deterministic hourly state evolution with conservation ledgers
Interfaces: Desktop · CLI · PythonPySide6 desktop app, command-line tool and a Python SDK through pybind11
Weather input: ERA5 or CSVAutomatic ERA5 reanalysis download, or your own hourly wind and wave file
Project files: .olh2 · .olh2studyJSON projects and versioned study recipes
Outputs: JSON · CSV · HTMLSummary, hourly time series, portable report and a provenance manifest
Platforms: Windows · LinuxWindows is the primary platform; Python 3.12–3.13

System flow

How energy and hydrogen move through the hub

In every simulated hour, an electrical bus balances wind power, storage and backup power against the platform and process loads. Hydrogen moves from electrolysis through a gas buffer to one selected export pathway. The normal pathways are LH₂ shipping and a gaseous-H₂ pipeline; compressed-H₂ shipping and ammonia carriers are available only with an explicit research opt-in. Waves and wind determine marine loading windows. Every flow and loss is booked in hourly ledgers, and each run ends with conservation checks and an independent audit.

Electricity
Water
Gaseous hydrogen
Liquid hydrogen
Weather data
Loss booked in the ledgers
Draws power from the electrical bus
Research-stage opt-in pathway

Simplified view of the integrated chain. Release v0.4.0-alpha.6 also includes opt-in research-stage compressed-H₂ and ammonia carrier pathways. Each project still uses one export pathway.

Read the diagram as text

Weather. An hourly metocean year of ERA5 or imported wind and wave records is quality-controlled before any run. Wind speed at hub height drives the wind farm, and wave height and wind set the windows in which cargo can be loaded.
Electricity. The wind farm, a battery, underwater compressed-air energy storage (UCAES) and a capped backup generator supply an electrical bus. The bus serves the must-run platform hotel load and the process loads: desalination, electrolysis, gas compression, liquefaction and, on the pipeline pathway, export compression. Unused surplus is curtailed.
Hydrogen production. Desalination supplies product water to PEM electrolysis, which feeds a compressed gaseous-hydrogen (GH₂) buffer.
Liquid-hydrogen pathway. GH₂ is liquefied and held in a cryogenic tank, loaded onto a shuttle vessel at the offshore terminal when the weather allows, and shipped to the customer. Tank boil-off, transfer losses and voyage boil-off are tracked.
Pipeline pathway. An export booster compresses GH₂ into a subsea pipeline to landfall and the customer. Leakage is tracked.
Compressed-H₂ shipping, research opt-in. The carrier model adds offshore loading compression, real-gas cargo with pressure and temperature limits, a two-ship fleet and onshore unloading at the declared delivery pressure.
Ammonia carrier, research opt-in. Hydrogen is combined with nitrogen through air separation and Haber-Bosch synthesis, stored as refrigerated ammonia, shipped to the customer and optionally cracked back to hydrogen inside the declared study boundary.
Checks and results. Energy and mass balances must close in every hour. Hard checks in the core and an independent audit follow, economics give CAPEX, OPEX and the delivered cost of hydrogen (DCOH), and the run is saved as a result bundle with a summary, hourly series, report and provenance record.

Capabilities

What the current platform code can do

Status labels follow the software's own capability register. Verified means internally verified through unit, analytical, conservation and regression tests. It does not mean external experimental validation. The carrier modules ship in the v0.4.0-alpha.6 installer but remain explicit research-stage opt-ins.

Verified internally verified, integrated physics
Implemented working data, analysis or workflow feature
Research stage implemented but not enabled for normal use
Planned no implementation yet

Implemented

Site and metocean data

Site selection on an offline world map or by coordinates
Automatic ERA5 wind and wave download for complete years, with caching, stop and resume, and source hashes
Quality control: full calendar years, range checks, short gaps filled (6 h by default), long gaps rejected, hub-height wind correction, design-year selection
Read-only context from GEBCO bathymetry and the NGA World Port Index
Ocean Networks Canada observations compared with ERA5 (bias, MAE, RMSE, correlation) without replacing the simulation weather

Verified

Wind power

Offshore wind farm based on the IEA 15-MW reference turbine power curve
Hub-height wind correction and output capped at nameplate rating
Wave and tidal generation exist only as research-stage compatibility modules

Verified

Water and hydrogen production

PEM electrolysis with part-load operation
Seawater reverse-osmosis desalination with water and energy ledgers
Optional chronological stack degradation and automatic stack replacement

Verified

Gaseous hydrogen buffer

Simple inventory model, or real-gas dynamic storage that tracks pressure and temperature
Hydrogen properties from the Leachman (NIST) equation of state
Staged compression with power and flow limits

Verified

Liquefaction and LH₂ storage

Dynamic liquefier with capacity, turndown and energy use
LH₂ tank with simple boil-off, or an equilibrium-thermal model: heat ingress, self-pressurization, venting and relief-pressure checks

Verified

Electrical storage and platform loads

Battery storage
Underwater compressed-air energy storage (UCAES), as an energy store or a thermodynamic model with thermal storage
Platform loads and a capped backup generator, with unserved energy reported explicitly

Verified

Marine logistics

Terminal loading only inside wind–wave weather windows
Vessel loading, departure, voyage, customer unloading and return, tracked call by call
Cargo boil-off and tank pressure on board; optional reliquefaction, which must be energy-accounted

Verified

Pipeline export pathway

Alternative to shipping: compressed hydrogen sent through a single export pipeline
Real-gas compression work, Darcy friction losses, leakage and customer back-pressure
Quasi-steady model: no line-pack or transient flow

Research stage

Compressed-hydrogen and ammonia carriers

Compressed-hydrogen ships: real-gas cargo with pressure and temperature limits, offshore loading compression, a two-ship fleet loading inside weather windows, and onshore unloading
Ammonia: air separation and Haber-Bosch synthesis with minimum load, ramp limits and hot standby, a refrigerated store, a gas carrier and optional cracking back to hydrogen
Closed mass and energy ledgers and an independent audit; costs from a register of cited published sources (USD 2022)
The hydrogen buffer feeding the carriers includes the heat capacity of its steel wall and must stay within its design temperature limits in every hour
Included in the v0.4.0-alpha.6 installer as opt-in research modules; they are not promoted to the normal pathway selector

Implemented

Economics

CAPEX, OPEX and discounted replacements
Delivered cost of hydrogen (DCOH) at the transfer point, including shipping, and at the customer
Default costs are declared study assumptions, kept separate from the physics

Verified

Research Lab

One-at-a-time sensitivity and Latin-hypercube Monte Carlo
Interannual comparison of complete, quality-checked weather years
NSGA-II multi-objective sizing; every proposed design is re-checked with a full-year physical replay
Storage-portfolio comparison (none, battery, UCAES, combined)

Implemented

Studies

Versioned study recipes that reference the platform physics and never copy it
Published-study reproduction, templates, cloning and per-experiment readiness
Capability register that keeps research and planned features from running by accident

Implemented

Reproducibility and usability

Each run saved with its configuration and weather-file hashes and the software version
Run history, run comparison and a generated methods statement
Run-readiness checks, settings search, activity log, and cancellation at safe checkpoints

Model fidelity

Simple where possible, detailed where it matters

Most subsystems have a fast reduced-order model for screening and a higher-fidelity model that resolves more physical state. Together the higher-fidelity options form the "P8 integrated advanced chain", the frozen and internally verified physics baseline. A more detailed model is not the same as a validated one, and the software labels the two separately.

Fidelity options in v0.4.0-alpha.6
Subsystem	Reduced-order model	Higher-fidelity option
GH₂ storage	Mass inventory with prescribed compression energy	Real-gas dynamic: pressure, temperature, compressibility and staged compression
Stationary LH₂ tank	Prescribed boil-off	Equilibrium thermal: heat ingress, liquid–vapour equilibrium, self-pressurization, venting and pressure limits
UCAES	Energy store with charge and discharge efficiencies	Thermodynamic isobaric: depth pressure, stored air mass, compression and expansion, thermal storage
Vessel cargo	Prescribed voyage boil-off	Equilibrium thermal cargo state through loading, voyage, unloading and return
Electrolyzer	Constant performance	Chronological degradation with operating-hour history and stack replacement

Architecture

Physics in one place

Each layer has one job. The C++ core owns state evolution, dispatch, inventories, marine-transfer state and the hourly conservation ledgers. Python owns data, economics, analysis, studies and reporting. The desktop application never duplicates model equations.

User interfacesPySide6 · CLI · Python
Desktop application with eleven workflow pages; offshorelh2 command-line tool for reproducible runs and ERA5 download; OffshoreH2Model Python API for scripted studies.
Studies and analysisPython
Study recipes, capability register and runner; sensitivity, Monte Carlo, interannual and NSGA-II workflows; economics and delivered-cost boundaries; reports and provenance manifests.
Platform servicesPython SDK
Project schema and validation; metocean ingestion and quality control; site-data providers (ERA5 via Copernicus CDS, GEBCO, NGA World Port Index, Ocean Networks Canada); cyclic steady state, spin-up and checkpoints.
Typed bridgepybind11
Bindings only, with no hidden formulas or fallbacks. Long simulations release the Python interpreter lock so the interface stays responsive.
Physical coreC++20
Wind, electrolysis and water, real-gas hydrogen thermophysics, liquefier, LH₂ storage, battery and UCAES, terminal and vessel logistics, pipeline export, compressed-H₂ carrier physics, ammonia synthesis and carrier logistics, hub dispatch and hourly mass and energy ledgers.

Workflow

From a map point to a citable result

The desktop application follows the order of a study. Each page owns one part of the project, and a run-readiness check lists anything that would block a run or affect how its results should be read.

DashboardCurrent study status, run readiness and shortcuts to each step.
StudiesPublished studies, templates and your own study recipes.
Project SetupName the study and choose the export pathway.
Site & MetoceanPick a site, prepare or import weather data, run quality control.
System DesignChoose technologies and fix, optimize or disable each component.
Operations & ShippingShipping procedure, vessel and terminal sizing, route and weather limits.
EconomicsFinancial and cost assumptions, separate from the physics.
SimulationRun a finite chronological or cyclic steady-state year with hard checks.
ResultsKey results, hourly charts, run history, comparison and export.
Research LabSensitivity, uncertainty, interannual, optimization and storage studies.
Validation & EvidenceWhat has been verified, screened against literature or still needs validation.

Read the step-by-step guide

Desktop interface tour

A clearer workflow, from site to results

These are authentic captures of the redesigned desktop research application, taken from bundled example projects. They show the integrated interface under development, not field results or third-party certification. The alpha.8 release candidate is still subject to distribution review.

01 / Overview

A dashboard that explains the next step

Study readiness, the current physical model, a five-step workflow and links to separate hydrogen workspaces are visible without opening multiple settings pages.

Redesigned OffshoreLH2 dashboard with grouped navigation, readiness checks, and a five-step workflow after a P8 example run. — **A dashboard that explains the next step.** The live readiness state identifies what has been configured and whether a result is current.

02 / Site and weather

Metocean context beside the controls

The site map, coordinates and weather-data controls share one screen. ERA5 preparation, manual import and source provenance retain their separate checks.

Redesigned Site and Metocean page with map and the associated weather configuration. — **Metocean context beside the controls.** The map is context, not proof of site suitability.

03 / Engineering design

Routine sizing first, research details when needed

Component sizing is easier to scan; expert options are available in expandable sections without forcing the user through the full parameter list.

System Design page with component cards and equipment sizing settings in a two-column interface. — **Routine sizing first, research details when needed.** The stored engineering values and numerical precision are unchanged by the UI redesign.

04 / Run control

Readiness before computation

The run control and progress state appear in the same workflow as the settings and the independent audit, with a clear way to cancel a running simulation.

Simulation page showing an active computation with progress and a readiness checklist. — **Readiness before computation.** A successful simulation must still pass the underlying physical and audit gates.

Advanced views and analysis

Detailed overrides and hourly results remain available without cluttering routine project setup. Screens below are from GUI development captures; the figures are illustrative study outputs.

Expanded advanced System Design controls showing research override settings. — **Advanced design overrides.** Expert controls stay collapsible and separate from routine sizing.

Hourly plot of offshore and vessel liquid-hydrogen tank pressures with pressure-limit reference lines. — **LH₂ pressure trends.** Reference lines and the time history make operating constraints easier to inspect.

Earlier alpha.5 Results overview for the North Atlantic demonstration with delivered hydrogen, costs, audit checks and hourly plots. — **Results and audit.** Earlier alpha.5 results capture; the redesigned results screen is awaiting a corrected final screenshot. Costs are research assumptions, not project quotes.

The onshore hydrogen workspace now has its own desktop screens for hourly inputs, production, delivery and financial results. Offshore and onshore retain separate physics workflows.

Research applications

Questions the platform is built to answer

Because the whole chain is simulated together, a constraint in one stage shows up in all the others. That makes it possible to ask questions which isolated component models cannot answer.

Resource and siting

How do wind and wave climate, and year-to-year variability, change production and marine operability at a candidate site?

System sizing

Which combination of wind, electrolysis, liquefaction and storage capacity performs best within declared bounds and service constraints?

Storage

When do batteries, compressed-air storage or larger hydrogen inventories reduce delivered cost or improve service, and when do they not?

Hydrogen chain

How do gas pressure limits, LH₂ tank thermodynamics, electrolyzer degradation and water demand constrain operation?

Marine logistics

How do weather windows, vessel availability, boil-off and delivery schedules affect the hydrogen that actually reaches the customer?

Economics and uncertainty

How sensitive is delivered cost to technical and economic assumptions, and how wide is the spread under declared uncertainty?

Model fidelity as a research question. OffshoreLH2 can run the same hardware with simplified and with detailed physics, so a change caused by the design can be told apart from a change caused by the model. An earlier LH₂-hub study has been rebuilt as a study recipe. It reproduces the original result under the original assumptions, and the higher-fidelity chain then shows how far the conclusions move once tank thermodynamics, vessel cargo state and degradation are resolved.

My 2026 IJHE article on operability thresholds studied the same class of system with a dedicated hourly production, storage and vessel model. Turning studies of that kind into OffshoreLH2 recipes is ongoing work.

Reproducible studies

Papers become recipes, not new code

The platform separates three things. The physical models are the ingredients and the analysis methods are the equipment. A study is a recipe that says which of each to use, in what order and with which data. A recipe never brings its own physics.

A study recipe (.olh2study, versioned JSON) declares:

sites and datasets, with SHA-256 hashes and the weather years that passed quality control;
the export pathway, technologies and fidelity levels;
which components are fixed and which are optimized, with their bounds;
cost boundaries, optimization settings and seeds;
experiments, requested outputs and provenance, including what the recipe was cloned from.

Each experiment is shown as Ready, Declared (valid, but not yet connected to a runner) or Blocked (with the reason). Only Ready experiments run, and each run writes to a new folder with a manifest of its inputs and hashes. Generic runners currently execute baseline, sensitivity, uncertainty, interannual and NSGA-II experiments for single-site studies.

What every run leaves behind

File	Contents
`summary.json`	Key results, economics and check outcomes
`timeseries.csv`	Hourly simulation output
`report.html`	Portable, human-readable report
`project_snapshot.json`	The exact configuration used
`manifest.json`	Software and core versions, build commit, configuration and weather hashes
`analysis_context.json`	Seed, sample counts and inputs for each Research Lab analysis

A cancelled run never writes a result bundle. It is marked CANCELLED / INCOMPLETE so that partial work cannot be mistaken for a finished result.

Verification and evidence

What has been checked, and what has not

The physics baseline (called P8) was frozen and qualified on Windows in September 2026. External evidence is tracked separately. The current evidence set includes a quantitative NASA K-Site LH₂ self-pressurization benchmark with predeclared acceptance criteria, while the carrier integrations remain explicitly research stage. Passing one benchmark does not imply that every subsystem is experimentally validated.

23 / 23native C++ tests passed in the latest carrier exact-head Windows gate

8,784 hfull leap-year integrated acceptance run with an independent audit

7 yearsconsecutive state-continuity stress test passed

~10⁻¹⁶maximum hourly relative error of the electrical ledger in the canonical case

External benchmark results

External comparison	Result	Status / claim
NASA K-Site LH₂ quasi-steady homogeneous pressure-rise rates	7 / 7 cases within the predeclared 10% tolerance; maximum error 9.465%	PASS
NASA K-Site LH₂ full pressure-time homogeneous curves	6 / 6 curves pass; pressure-rise NRMSE 0.32–4.58%	PASS
NASA measured stratified pressure-time curves	Digitized and compared directly with the model	Descriptive model-form evidence; no pass/fail gate because the lumped tank does not resolve gravity-driven stratification
NIST / Leachman hydrogen thermophysical-property check	Retained in the release validation suite	PASS
Restelli ammonia production and makeup compression	−2.0% ammonia/H₂; +2.2% compression	PASS research-stage literature benchmark
d'Amore-Domenech hydrogen-fuelled ship range	+4.7% against the published technical distance limit	PASS research-stage literature benchmark
Taccani compressed-H₂ loading mass	−5.6% against a 5% tolerance (−7.6% before the entry-temperature correction)	OPEN preserved failure and carrier promotion blocker

The carrier comparisons are model-to-model literature benchmarks, not measurements from an operating hydrogen ship or offshore ammonia plant. Failed and descriptive comparisons are kept visible rather than tuned away.

Open the full validation evidence register

Also passed at the frozen baseline

Checkpoint and restart give results identical to an uninterrupted run
Water balance and ship-energy closure
Optimizer proposals replayed with full physics; infeasible designs stay infeasible
Hydrogen-property check against the NIST/Leachman equation of state
A deliberately unsafe LH₂ tank design is rejected

The latest carrier integration run reported 530 Python tests passed and 1 skipped. The exact count will be refreshed again when the next installer release is cut.

Still open

Higher-fidelity LH₂ thermal-stratification validation against the measured NASA curves, if stratification physics is added to the tank model
Matched experimental comparisons for UCAES, PEM part-load operation and vessel boil-off
Liquefier plant comparison and project-specific marine operability evidence
Project-specific cost sources before economics are treated as forecasts

Scope. OffshoreLH2 is research software. It is not a certified engineering-design, class-approval, structural, CFD, process-safety or marine-assurance tool, and its default costs are study assumptions rather than vendor quotes.

Status and roadmap

Where development stands

The integrated alpha.8 Windows candidate includes the redesigned offshore and onshore workspaces. Its release remains a draft pending final dependency and licensing review; the existing alpha.6 documentation and examples below describe an earlier preview.

OffshoreLH2 is in active development as a research preview. New capabilities are added one at a time, and each must pass its own evidence gates before it can be used in normal studies.

v0.4.0-alpha.6

Available now

Liquid-hydrogen pathway, end to end
Gaseous-hydrogen pipeline pathway (quasi-steady)
Higher-fidelity thermophysics and electrolyzer degradation
ERA5 site preparation and Ocean Networks Canada comparison
Research Lab, Studies, run history and provenance

Not enabled

Research stage

Compressed-hydrogen shipping and ammonia carrier pathways: in the v0.4.0-alpha.6 installer with hourly physics, desktop interface, source register and independent audits; explicit opt-in is required and they are not promoted to normal pathways
Wave and tidal generation (compatibility modules)
Fidelity comparison and physics attribution, currently available only through the published-study workflow

No implementation yet

Planned

MILP and MPC dispatch back-ends
Multi-site study execution and cross-fidelity design replay
Offshore solar; alkaline and solid-oxide electrolysis
Hybrid offshore energy hubs and offshore CO₂ capture, transport and storage
Lifecycle-emissions objective

Recent releases and integrations

8 Oct 2026 · alpha.6
Professor-demo pathway fixes
Projects set up for the advanced LH₂ chain, such as the professor demo, now run the pipeline and research carrier pathways: an LH₂ vessel check was evaluated on pathways without a vessel. The desktop app now applies the carrier GH₂ buffer wall, reports failed runs instead of leaving earlier results looking current, and no longer reports a replaced Results Explorer as crashed. LH₂ and pipeline results are unchanged; the build passed the exact-head Windows validation gate.
7 Oct 2026 · alpha.5
Research carriers and NASA validation release
The v0.4.0-alpha.5 installer ships the compressed-H₂ and ammonia carrier pathways behind the research opt-in, the NASA K-Site pressure-time benchmark and a fix for garbled characters in the desktop text. LH₂ and pipeline results are unchanged; the build passed the exact-head Windows validation gate.
7 Oct 2026 · research integration
Compressed-H₂ and ammonia carrier pathways merged into main
The carrier modules are integrated as opt-in research pathways with real-gas cargo or ammonia-chain physics, multi-year warm-up and measurement windows, hard feasibility checks, cited source registers and preserved benchmark failures. The GH₂ buffer feeding them models its steel wall and must stay within design temperature limits; the Taccani loading benchmark still fails at −5.6% and blocks promotion. They are not promoted to normal pathways.
7 Oct 2026 · validation update
NASA K-Site LH₂ external pressure-time benchmark
Primary NASA TM-105411 Figure 2 data digitized with provenance and an independent render check. All 7 homogeneous-reference slope cases and all 6 full pressure-time homogeneous curves pass their predeclared 10% gates. The measured stratified curves remain visible as descriptive model-form evidence rather than being tuned away.
3 Oct 2026 · alpha.4
Ocean Networks Canada observational validation
Live Oceans 3.0 observations, targeted station discovery and a Campbell River wind comparison workflow; matched-sample bias, MAE, RMSE and correlation against ERA5; QA/QC flags and provenance kept; API credentials redacted from errors.
2 Oct 2026 · alpha.3
Integrated research-platform preview
Gaseous pipeline pathway integrated alongside LH₂; study recipes and published-study reproduction; run readiness, run history, run comparison and methods statements; cooperative cancellation; pathway-aware Results Explorer.
25 Sep 2026 · alpha.2
Research workbench
Dashboard, offline world map, ERA5 acquisition with provenance, GEBCO and port context, Research Lab and the Validation & Evidence workspace, built on the frozen P8 physics baseline.

Access and citation

The source repository is private while the first public release is prepared. The source carries an Apache-2.0 licence and citation metadata, and an archived release with a DOI is planned. Researchers interested in evaluation or collaboration are welcome to ask for access.

Request access by email Read the guide