Tetiaroa · Sea water air conditioning

A deep diveinto SWAC

Cooling requires you to move heat from one place to another. In the tropics, that usually requires an immense amount of energy... until you look down. Nine hundred metres under Teti'aroa, the Pacific sits at five degrees.

The descent

Nine hundred metres, straight down

Follow the pipe all the way down to where the water sits near freezing.

Depth0 m
Temperature28.5 °C
Pressure1 bar
Daylight remaining100.00 %
0 metresWarm mixed layer

The lagoon

Twenty-eight degrees. Perfect for swimming, but not for cooling. We need to dive deeper.

40 metresStill 28 °C

The reef wall

As we descend down the reef wall, the sealife changes and becomes less frequent. The water begins to cool and the amount of light starts to decrease.

200 metresFalling fast

The last of the light

A hundred-thousandth of the sunlight that hit the surface. Divers call this the twilight zone. The water is cooling now, and the pipe still has seven hundred metres to fall.

400 metresThe boundary

Through the thermocline

The ocean's dividing line. Above it, sun-warmed water that mixes with the surface. Below it, a different ocean entirely.

900 metresIntake depth

The intake

Every day, every season, the water here sits near 5 degrees. Now that we have reached it, this ice cold water can be pumped to the surface.

And then it becomes energy efficient cooling

The cold seawater flows across a heat exchanger, absorbing the heat from anything from air conditioning to server cooling, and then pumps the heated water back into the warm, upper layers of the ocean.

A cross-section of the water column beside Tetiaroa, from the reef at the surface down to the intake pipe mouth at 900 metres, with temperature falling from 28 to 5 degrees.

The basics

What is SWAC?

Sea water air conditioning replaces the part of an air conditioner that makes cold. Instead of a compressor burning electricity to chill water, a pipe runs out to where the ocean is already cold and brings that cold ashore. The seawater never enters a building and never mixes with anything. It passes a titanium plate, hands over its chill, and goes home. Everything downstream is ordinary air conditioning.

What is SWAC?A cross-section showing a pipe running from a shore plant down to 900 metres, a heat exchanger on land, an optional deep-water branch serving the Bailey Field Station wet lab, a freshwater usage loop carrying chilled water to buildings and warmed water back, and a return pipe discharging warmed seawater at depth.Sea level900 m · 5 °CPlantBuildingsOptional Bailey Field Station wet labCold seawater inWarmed seawater outChilled fresh water supplyWarmed fresh water return01020304
A cross-section showing a pipe running from a shore plant down to 900 metres, a heat exchanger on land, an optional deep-water branch serving the Bailey Field Station wet lab, a freshwater usage loop carrying chilled water to buildings and warmed water back, and a return pipe discharging warmed seawater at depth.
  1. 01

    Reach the cold

    From a cold water source, pump the water to the heat exchanger

  2. 02

    Trade the chill

    The seawater passes thru a heat exchanger. It sucks the heat out of a fresh water loop. The two loops never make physical contact.

  3. 03

    Cool the buildings

    Chilled fresh water circulates thru a closed loop cooling rooms, systems, servers, etc.

  4. 04

    Warm water returned

    The warmed seawater is returned to the warm upper layers of its source

Up to90%
Less electricity than a conventional chiller

The meter

Watch both meters

Same building, same rooms, same afternoon, same number on the thermostat. One runs a conventional chiller. One runs sea water air conditioning. Give the meters a moment, or skip to the end of the year.

Cooling load2,500 kW

Conventional chiller: 833 kW. Sea water air conditioning: 125 kW.

Conventional chillerLive
kWh0

833 kW

Sea water air conditioningLive
kWh0

125 kW

Per year · kWh
Cooling loadConventional chillerSea water air conditioning
One villa22,5003,375
Small hotel1,050,000157,500
The resort3,750,000562,500
A hospital7,500,0001,125,000

These figures come from a model, not site meters. It assumes a seasonal COP of 3.0 for a conventional chiller and a whole-system COP of 20 for SWAC, including pumping and distribution, over 4,500 equivalent full-load hours a year. Diesel is used only as a comparison: one litre represents 3.6 kWh of delivered electricity and, if burned, 2.68 kg of CO₂.

Elsewhere

Who else has the slope

Plants that are running, freshwater cousins, and a few that never got built. Drag the globe. The pattern is easy to spot: this technology follows steep coastlines and deep lakes, and thins out where the shelf runs long.

OperatingFresh waterCandidateNot built

Drag to rotate · tap a marker

Operating · French Polynesia
Tetiaroa
Roughly 900 m intake on the atoll's outer slope, running since 2013.

Run your own coastline

Three numbers decide it. How far you have to go to reach cold water, how much cooling you need, and what electricity costs where you are.

Distance to cold water4 km
Cooling demand2500 kW
Electricity price0.35 / kWh
Capital cost11.0 M
Saved per year1.12 M
Simple payback9.9 years
Simple payback
Worth a feasibility study
A payback in this range is ordinary for civic infrastructure and long for a private developer. Whether it gets built usually comes down to who is holding the balance sheet.

Deliberately coarse. It assumes roughly two million per kilometre of marine pipeline and twelve hundred per kilowatt of onshore plant, and it ignores financing, permitting, seabed conditions and most of what actually decides a project. Treat it as a way to feel the tradeoff, then talk to someone who has laid one.

Tetiaroa Society

Bring us your project

Tetiaroa has run a deep-water cooling system through a decade of tropical weather, and the Society's scientists have been measuring what it does to the reef the entire time. That combination is rare: a working plant and the research to go with it.

Talk to us about your siteOur research stations

What we bring

  • Route surveys and slope stability assessments
  • Discharge modelling and reef monitoring, before and after
  • Plant sizing for loads that triple between noon and midnight
  • Ten years of operating data across cyclone seasons