Glossary

Terms are defined at first use across the docs; this is the central reference.

Domain terms

Power-to-X (PtX) — using renewable electricity to make hydrogen, then converting it to a shippable product (X = ammonia, e-methanol, e-SAF, …).
Green hydrogen — hydrogen made by splitting water with renewable electricity in an electrolyser (no fossil carbon).
Derivative — the final product a project makes from hydrogen. Supported kinds: NH3 (ammonia), eMeOH (e-methanol), eSAF (sustainable aviation fuel), eNG (synthetic natural gas), green_iron, green_steel, H2_export (merchant compressed hydrogen). A project holds a list of derivatives.
Electrolyser — the machine that turns electricity + water into hydrogen. Its size (MW) is usually the second-most-important lever after renewables.
BESS — Battery Energy Storage System. Shifts electricity across hours.
H₂ buffer — a hydrogen store (tonnes) that decouples the electrolyser from the synthesis unit hour to hour.
BoP — Balance of Plant: the fixed auxiliary electrical load a plant draws.
Curtailment — renewable electricity produced but not used (wasted), because nothing could absorb it that hour.
Capacity factor (CF) — the average fraction of nameplate a wind/solar asset actually delivers (0–1); a measure of resource quality.
Site — a reusable, owner-scoped location with per-carrier weather datasets (an 8,760-hour wind and solar CF curve). Projects reference a Site.

CAPEX / OPEX — upfront capital cost / recurring yearly operating cost.
CRF — Capital Recovery Factor: spreads CAPEX over the project life so it can be added to yearly OPEX. CRF = wacc·(1+wacc)ⁿ / ((1+wacc)ⁿ − 1).
WACC — Weighted Average Cost of Capital: the discount rate.
Levelized cost — total annualized cost ÷ annual output. LCOH = per kg of hydrogen; LCOA = per tonne of ammonia (or, generally, LCO per tonne of a product); LCOE = per MWh of electricity delivered.
Blended product LCO — for a multi-product project, the H₂-share-weighted average of each product’s LCO. The objective right-size minimises.

Mode A (annual) — closed-form yearly averages on an assumed curtailment floor; no weather data.
Mode B (timeseries / greedy) — an 8,760-hour hour-by-hour simulation with fixed priority rules and no foresight.
Feasibility / LP — the whole year solved as a Linear Program (optimal dispatch with perfect foresight and real operating limits). Built with PyPSA, solved by HiGHS.
Binding constraint / bottleneck — the stage that limits production (the smallest ceiling). The flow diagram lights it up.
Right-size — the optimiser that picks the cheapest set of component sizes.
Duals / shadow prices — a by-product of the LP: the marginal value of one more unit of a constraint (e.g. how much more product +1 MWh of BESS would buy).
Snapshot — a saved, fully-solved design (assumptions + sizing + results) you can compare against others.
Assumption book (DAB / project book) — the versioned set of technical and financial parameters that drives every result.

FastAPI — the Python web framework serving the backend API.
PyPSA — Python for Power System Analysis; builds the feasibility LP network.
HiGHS — the open-source solver that optimises the LP.
Parquet — a compact columnar file format used for hourly result timeseries.
SQLite — the embedded database storing projects, assumptions, and snapshots.
Vite / React / TypeScript — the frontend build tool, UI library, and language.
Room — a screen inside a project (cockpit, feasibility, assumptions, …).
Cockpit — the Prefeasibility room: edit sizes on the left, read results on the right.