In part 3 of this series on energy sources for generating electricity, I discussed the Ocean Thermal Energy Conversion (Otec). In this column, the ocean wave as energy source would be presented. However, it needs to be narrowed down further, since there are several types of ocean wave energy source. Here, the ocean-wave-turbine-system would be the one discussed. In this type, there are two methods: 1) tapered channel method and 2) Bristol cylinder method. Let us concisely discuss each of these methods, their main components and principle of operation.
1] In the first method, a tapered channel is used. The following are the main components. There is a tapered channel, a reservoir, a water turbine (just like in hydro-electric power plant) and a pipe connecting the reservoir and the water turbine. It is of course constructed and installed in the sea.
As to the channel, there are two ends: the wide end facing the ocean and the narrow end connected to the reservoir.
As to the reservoir, it is strategically placed in an elevated location; meaning, it is above the surface of the ocean. As to the water turbine, it is placed somewhere between the level of the surface of the ocean and the level of the reservoir. And as to the pipe, it is used to connect the reservoir and the water turbine.
Now, the waves of the ocean are captured by the tapered channel, which is designed to have an upward sloped bottom. As the waves enter through the tapered channel, they are being somewhat squeezed by the narrowing sides of the channel and tossed up by the upward sloped bottom of the channel. This causes the waves to reach the higher level of the reservoir, in which they are being deposited there. As a result, the reservoir is being filled up with the captured sea water.
The sea water in the reservoir is then released through the pipe connecting the reservoir and the water turbine, which is in a level lower than the reservoir but higher than the surface of the ocean. The sea water would rush down the pipe and fall into the wheel of the turbine, causing it to rotate.
The sea water exits the turbine back to the ocean. An electric generator connected to the turbine shaft would also rotate, thereby producing electricity. There is how basically ocean-wave-tapered-channel system works.
2] In the second method, the following are the main components: a spherical buoy, the Bristol cylinders which are also pumps and hydraulic pipes.
The spherical buoy is connected to the shaft of the Bristol cylinder and/or pump. The other end of the cylinder housing is connected to the sea bed. Now, since the spherical buoy is hollow, it tends to float on the surface of the ocean. For this reason, the ocean waves would cause the spherical buoy to be tossed up along with the wave crest and tossed down along with the wave trough.
As the spherical buoy moves up, the shaft of the Bristol cylinder/pump is being pulled up. This allows the sea water to enter into the cylinder. And, as the spherical buoy moves down, the shaft of the Bristol cylinder/pump is pushed in the cylinder. This causes the sea water in the cylinder to be pumped out.
Through the hydraulic pipe connected to the cylinder, the sea water is being pumped out and up to the reservoir located above the surface of the ocean and it is being deposited there. Then, the sea water in the reservoir is released through a pipe connected to the turbine wheel. The sea water would rush down the pipe and fall into the turbine wheel, causing the turbine shaft to rotate. The ocean water exits the turbine back to the ocean. The generator connected to the turbine shaft would also rotate, thereby producing electricity.
It is a clean, sustainable energy source. In a place where ocean waves are abundant, this method is indeed feasible. If there are ocean waves 24/7, then there could be unlimited source of ocean-wave energy to be used to rotate the water turbine, which in turn rotates the generator to produce electric power.
One advantage of this energy source for generating electricity is that during its operation it does not produce any pollutants to the atmosphere. However, one major disadvantage of this method is that during its construction and installation, alterations of the physical structure of the place is unavoidable. This could affect the rich biodiversity in coastal and near-shore areas. “The installation of wave energy devices, particularly onshore and near-shore designs, could have impacts on fish since construction activity will disturb the sea bed” (Brooke, ed., 2003, 60-61). Nevertheless, it is one renewable energy source for generating electricity needed by man.
