T

ter tWa2,000 2,500 3,000

Fig. A.8 Temperature variations in relation to ocean depth, simplified illustration (according to /A-2/)

In principle, this type of thermal energy could be used for power generation by means of open or closed Rankine processes (ORC processes). This cycle is based

Water temperature in °C

0 10 20 30

Fig. A.8 Temperature variations in relation to ocean depth, simplified illustration (according to /A-2/)

on the temperature difference between the warm surface water of a maximum of 22 to approximately 28 °C and the cold deep waters of approximately 4 to 7 °C (Fig. A.9). The efficiency of such a cycle depends on the useful temperature difference. Due to the small available temperature differences of a maximum of about 20 K, these power plants can only achieve very low efficiencies that vary between 1 and a maximum of 3 %. In addition, for this electricity generation method enormous volumes of water need to be circulated. Furthermore, the water needs to be transferred from deep sea layers to the ocean surface and vice-versa. The design of these plants is thus very expensive.

To keep energy transfer to the customer to a minimum, ocean thermal energy conversion plants are mainly built near the coastline. In parallel, an easy access to cold deep water is required to run such a cycle.

As the energy yield is relatively low when compared to the large mass or water flows to be transferred, this technology, generally referred to as OTEC (Ocean Thermal Energy Conversion) has, to date, not been applied due to economic aspects. Since there still remain unsolved technical problems with regard to the successful operation of such ocean thermal energy conversion plants, their application in the sunny parts of our planet cannot be expected within the years to come.

Warm water inflow

Electrical energy w

Warm water inflow

Electrical energy

Fig. A.9 Example of an OTEC plant (left: layout; right: power plant cycle; according to /A-1/)

liquid NH: Warm water discharge

Fig. A.9 Example of an OTEC plant (left: layout; right: power plant cycle; according to /A-1/)

A variety of this technology suitable for geographical areas, where both cold ocean currents and geothermal energy are available, has only lately been introduced. This method benefits from the temperature differences between warm areas near volcanic structures and cold ocean water. However, it is unlikely that this method will be put into practice in the near future due to considerable technical problems.

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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