SWAC (Sea-water air conditioning) aka DWSC (Deep water source cooling) is an innovative and ecological Air Conditioning technology which uses a renewable source of cold water. It is particularly fitted to Islands in the tropical belt as they represent an important cooling need and only a few kilometers away, deep in the ocean is a vast unused reservoir of cold water. The idea of SWAC is to link them together.

Other sources are appropriate for this use. Usually they can be

  • Oceans : Natural convection ocurring in the deep ocean results in a cold water layer between 800 and 1000m deep from the surface
  • The lakes in temperate areas : The difference of density between cold and warm water allows cold water to naturally stay at the bottom of the lakes (depth of  about 50m). The alpine Lakes are a very suited area for SWAC implementation for instance.
  • Cold water surface currents (As in Stockolm’s downtown AC system ) or other cold sources.

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TECHNIC:

Deep sea water is pumped to water surface. Cold water is thicker than hot water, thus cold water stays in depth whereas only upper layers are heated by the sun.

Then water goes through a heat exchange system to cool down the air conditioning frozen water network. During this step, pumped water heated up from few degrees. Water is afterwards released in a corresponding temperature depth, in order not to modify the ecosystem.

This ecological technology avoids and replaces normal air conditioning systems.

Advantages :

Energy Savings

This is a renewable energy based AC system providing low operating costs for residential and commercial coastal buildings/facilities. SWAC saves energy consumption from 80 to 90% compared to regular AC systems.

Ecological

SWAC systems don’t use any ozone depleting refrigerant. This is of paramount importance for large installations, even though there are other ecological solutions available. Environmentally friendly system. This asset keeps getting more interesting as European and world institutions are enforcing strong financial penalties on greenhouse gas emissions.

Multi-purpose

After cooling the secondary circuit, the sea water is still fresh enough to be used in the cooling process of auxiliary equipment’s, like Heat Pumps or other devices (needs to be investigated case by case)

Employment

SWAC systems create local employment given that the installation requires workers and divers. Most of the SWAC’s price is therefore reinjected in the local economy instead of going to energy exporting countries (oil, uranium, coil etc.)

Limits :

Depth

SWAC systems require a (relatively) vast available cold water resource.

Large-scale Project

The set up of such a system is expensive and needs a lot of workers. Moreover, it requires heavy marine industrial machinery. For instance, the pipelines can be several kilometers long for the large constructions.

Water Debit

The debit has an upper bound (thus limiting the cold production) due to cavitation phenomenon (Formation of air bubbles which induce great stress and fatigue on the equipment).

The particular case of islands

A SWAC system is especially interesting for islands given the following :

  • Islands naturally own a vast cold sea water reservoir within the ocean surrounding them.
  • Air Conditioning represents a strong part of the electrical consumption. In addition, Electricity in islands is quite expensive  given that islands don’t generate electricty but import it. Using a SWAC system will considerably reduce the electrical consumption and reduce the island’s dependence on fossil fuels.
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