The Teatro del Agua, together with the proposed new waterfront buildings, utilise energy from the sun, the sea and the atmosphere to create cooling and fresh water. The process is based on the Seawater Greenhouse concept but the principles are not limited to agriculture and may readily be adapted to the built environment. Indeed many of the principles have been in use since antiquity to moderate the climate in hot, arid regions. The range of possibilities for cooling is considerably enhanced by using seawater. This is a relatively new development, requiring the use of low cost plastics for pipes, pumps and heat exchangers (metals that are adequately corrosion resistant to seawater are generally too expensive for such applications).
Gran Canaria has abundant sunshine year round yet with moderate temperatures for its latitude (which is
the same as Kuwait). It also lies in close proximity to very deep, cold seawater. Within 4 km of the harbour, the seabed falls rapidly to a depth of 1000 metres, where the water temperature is 9ºC. The mean wind speed of 7m/s and NNE direction are remarkably constant year round, and can thus be harnessed to drive the ventilation.
These conditions may all be used to provide sustainable and low cost methods of cooling, and the production of fresh water. This energy is renewable, carbon free and unlimited in its abundance, as the cooling process is driven by solar energy evaporating surface seawater, and thermal stratification with depth.
If the temperature of an air to water heat exchanger is constantly below the ambient dew point temperature, and if its surface is exposed to the wind, water vapour will condense into fresh water continuously. The rate of condensation increases with increased air temperature and humidity, and there are various methods of augmenting this with solar energy. However, the average temperature in Gran Canaria is around 20ºC and rarely falls below 14ºC. Relative humidity stays constantly high – above 70% throughout the year. Thus with a cooling temperature of 10ºC, fresh water will be produced every day of the year, but with substantially more in summer than in winter.
The potential exists to produce fresh water at less cost than any other desalination system and using only renewable energy for the process, with cool air as a free by-product. The water produced is of distilled quality, similar
to dew or rain, and does not need any chemical treatment, unlike all other desalination processes.
The proposed development covers an area of about 400 000 m2. In the sunny climate of the Canary Islands, the amount of solar energy falling on this area is very large, reaching about 320 MW. If, for example, just 1/10th of that energy were used to distil fresh water from seawater, around 300 m3 per day of freshwater would be produced. The buildings are thus self-sufficient in water, and the surplus is sufficient to irrigate some 50,000 m2 of gardens. ....more
Seawater Greenhouse , London
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