Regasification is the one step in the LNG chain that wants heat rather than work, and heat is cheap if you are standing next to an ocean.
Open rack vaporisers
The most common design at coastal terminals. Seawater is pumped to the top of tall finned panels and runs down the outside by gravity; LNG flows upward inside, at pipeline pressure, and vaporises against the panel.
Nothing is burned. The operating cost is the seawater pumps, and the heat is free. Where the sea is warm enough this is decisively the cheapest way to regasify.
The constraints are environmental and thermal. Seawater needs to be above roughly five degrees Celsius or it starts freezing on the panels, which limits the design in cold regions or cold months. The intake volumes are large, so screens and marine life entrainment become permitting questions. And the discharge is colder than the water it came from, typically by several degrees, which is itself subject to consent.
Submerged combustion vaporisers
Gas is burned in a burner submerged in a water bath, and the exhaust bubbles up through the water, heating it. LNG tubes pass through the bath and vaporise.
It works anywhere, in any weather, at any sea temperature, and it starts fast. It is also the only common design that is genuinely independent of its surroundings, which is why terminals in cold climates rely on it and why almost every terminal has some.
The cost is fuel: roughly one and a half per cent of throughput burned to warm the rest. On a terminal running flat out that is a substantial and continuous expense, which is why combustion vaporisers usually cover peaks rather than baseload.
Bubbling exhaust through water also produces a mildly acidic condensate that has to be neutralised before discharge — a small operational detail that nonetheless needs a chemical dosing system.
Intermediate fluid vaporisers
A compromise for cold seawater. Rather than exchanging directly between seawater and LNG, an intermediate fluid — commonly propane — circulates in a loop, boiling against the seawater and condensing against the LNG.
The intermediate loop tolerates a much smaller temperature difference without freezing, so the terminal can use seawater that an open rack vaporiser could not. It costs an extra heat exchange step and a refrigerant inventory, and it is chosen where the sea is cool but not cold enough to justify burning gas year-round.
Ambient air vaporisers
Large finned towers drawing heat from the air itself. No fuel, no seawater, almost no energy beyond the fans where fitted.
They suit hot dry climates and inland terminals with no seawater available. What they need is space — a great deal of it — and time, because ice builds on the fins as they work and a tower has to come off line to defrost. Terminals using them run banks in rotation for that reason.
Why terminals mix them
The pattern almost everywhere is a base of seawater vaporisers with combustion vaporisers alongside.
The reason is not redundancy so much as responsiveness. Send-out is not steady: it rises hard in a cold snap, and a terminal that exists for peak shaving may sit near idle for months and then run flat out for a fortnight. A seawater vaporiser is cheap and slow to bring up. A combustion vaporiser starts quickly and costs fuel. Using each for what it is good at is cheaper than either alone.
The wasted cold
Every one of these designs throws away something valuable. LNG carries a large quantity of cold — hundreds of kilojoules per kilogram — and the standard practice is to dump it into the sea or the air.
A small number of terminals recover it. Air separation plants use it to liquefy nitrogen and oxygen; chilled warehousing uses it directly; a few sites generate power from the temperature difference. It has stayed a niche because the recovery only pays where a co-located user exists, and a terminal is usually sited for marine access rather than for industrial neighbours.
It is nonetheless one of the more obvious efficiencies still sitting on the table in the LNG chain.
What the data records
Vaporiser type is not in Global Energy Monitor’s terminal dataset, so no page here reports it. The terminal directory carries capacity, status, ownership and location, and where a field is absent it says Not reported rather than inferring from the climate.