Question

Describe ocean wave, tide, current, and thermal energy conversion. (8 marks) a. Large single-stage multi-blade turbines with rotor diameters of twelve meters and COP of 0.40 are to be installed in ocean currents flowing at a steady 2 m/s in the Gulf of Paria. If the density of seawater is 1025 kg/m', determine the output of a plant consisting of ten turbines. b.

Answer 1

a)

From the oceans we can harvest: thermal energy, from the temperature difference of the warm surface waters and the cool deeper waters, as well as potential and kynetic energy, usually lumped as mechanical energy, from the tides, waves and currents. The technology that is use to produce electricity using the difference between the low and high tides is very similar to the one use on the generation of electricity on the traditional hydroelectric power plants. The use of the tidal energy requires a dam or barrage across a shallow area preferably an estuary, bay or gulf of high tidal range where the difference on the low and high tide have to be at least 5 meters [01]. The tide basins are filled and empty every day with the flood tides when the water level rises and with the ebb tides when the water level falls. On the barrage there are low- head turbines and sluices gates that allow the water to flow from one side of the barrage to inside the tidal basin. This difference on elevation of the water level creates a hydrostatic head that generates electricity. There are different modes to generate electricity using the barrage systems:

Ebb generation - Incoming water (flood tide) is allowed to flow freely to fill the basin until high tide, then the sluices are close and water are retained on one side of the barrage. When the level of the water outside of the barrage decreased (ebb tide) sufficiently to create a hydrostatic head between the open waters and the tide basin, the sluices are open and water flows through the turbines and generate electricity.