With the growth of awareness regarding the immense environmental damage and global warming caused by fossil fuels like coal and oil alternative sources of energy that are both clean and renewable have grown in prominence. Energy from the ocean is also a form of energy. There are a number of ways in which this ocean energy can be harnessed. The two most commonly used however involve the use of ocean waves and tides.
When winds pass over the surfaces of the oceans, they produce waves. When the wind speed is higher than the wave speed energy is transferred from the winds to the waves. This energy is propagated as the waves move. Using a variety of methods wave power devices then harness this energy. An example of these power devices is the SeaRaser technology used by Britain which has piston pumps attached to ocean floors with buoys tethered to the piston. The buoys experience rising and falling due to the motion of ocean waves. It then generates water under high pressure which is flown to reservoirs located onshore via pipes. This water is then able to drive hydraulic generators that produce electricity (Phillips, 1977). Another method used in the production of power using wave energy is the Wavestar method. The method makes use of floats which move up and down as the waves move in the same pattern. Arms are attached to the floats and connected to the sea floor. As the floats move the attached hydraulics on them transfer this motion to a generator. This generator then converts the mechanical energy to electrical energy (Phillips, 1977).
Tidal power on the other hand is generated when the energy contained in tides is converted to electricity. Tides are as a result of the earth experiencing periodic varying attraction from physical bodies in the universe like the moon. Whenever this attraction occurs a rise occurs in the sea levels. The ocean middle is therefore forced to move towards the shore. This creates ocean tides whose energy can be converted to electrical energy using a tidal generator.
There are a number of methods in which this can be done. An example is the Tidal barrage method. Using this method the difference in high and low tides creates potential energy. Specialised dams are created to harness this potential energy. During the high tides period, the tidal power is taken to a basin behind the dam and is held as potential energy. During low tides this energy is converted to mechanical energy through turbines. This mechanical energy is then converted to electrical energy using generators (Evans, 2007). Another way is the usage of tidal generators. This method uses the energy in motion of water to move turbines. These turbines possess mechanical energy which the tidal generator converts to electrical energy (Evans, 2007). A significant advantage of these energy sources is that they are always readily available. Every ocean and sea (71% of earth’s surface) experiences waves and tides and therefore their potential is limitless.
Tidal energy is inexhaustible since it results from earth’s rotation and the gravitational attraction due to the moon and the sun. Since the earth’s rotation and gravitational forces which supply this energy is indefinite unlike fossil fuels that get exhausted. They are therefore some of the most important sources of sustainable energy. The other big advantage of energies whose sources is the ocean is that they have minimum environmental pollution especially when compared to fossil fuels like coal and oil. They also have zero carbon emissions which have been the major source of global warming. Tides and waves are also very predictable thus making them more reliable than the solar and wind power whose intermittent availability makes them unreliable. Once operational the running costs of tidal and wave energy plants is very low especially when compared to other energy sources like nuclear energy. The wave and tidal plants also have a much longer life span than other energy sources like wind. It is approximated that they can last up to 100 years. This makes them particularly cheap in the long run (Evans, 2007). Moreover tidal power in particular has a very high efficiency compared to other power sources like the fossil based ones.
Wave energy has a number of limitations as a form of energy. First, it arises from the fact the whole the process of energy production produces a lot of noise thus causing noise pollution. This can have adverse effects on the organisms with marine habitat. The methods used to generate this type of energy are also highly inefficient. Less than 20% of the total wave energy is harnessed in one cycle. Furthermore, there is also the danger of killing other industries like the fishing industry. This is because when wave farms are set up, they take a lot of fishing ground therefore undermining commercial fishing. Apart from fishing they also present a significant threat to navigation especially in areas where ships are likely to anchor (Rutan, 2008).
Moreover the initial cost especially of the technology required is usually so high that it locks out many less wealthy countries especially in the Third World. The other requirement for this project requires both significant scientific expertise and money thus locks out many countries from using this energy. More so, wave energy is quite unreliable. This is due to the fact that it is highly intermittent in terms of intensity. Sometimes the intensity is low that no significant power can be produced. This makes it hard to produce stable power. In addition, tidal and wave power requires high initial capital for start. A lot of resources are required in the construction of the dams used in the electricity generation and the equipment required. The costs are pushed up by the fact that most of the technology used is still in the experimental stage. There’s therefore high chance of failure. The result of this is that the risk of investing in these energy production methods increases. Fewer investors are therefore willing to put their money in tidal and wave energy production.
Significantly, the difficulty of transferring power from the oceans where it is produced to the inland areas where it is consumed also makes tidal and wave methods in some instances uneconomical to use. They are also prone to vagaries of nature like typhoons and tsunamis. Whenever they occur, a lot of destruction is caused which usually has a negative effect on power production. Another significant problem with tidal energy is that there are very few sites which have sufficient tides of the required energy to make its generation commercially viable. This limited site locations greatly the amount of power that can be generated using this method worldwide. Research has for example found that there are less than 40 sites that can support tidal barrages (Evans, 2007).
Just as wave energy, tidal production of tidal energy also poses a significant threat to marine life. The rotating blades of turbines have for example been found to kill many fish. This has the effect of causing the fish to immigrate to other areas in the oceans and seas.
Another threat to marine life is due to the fact that these methods usually use a lot of mechanical fluids. Whenever this mechanical fluids leak, there is a significant pollution of sea water which can be a threat to marine life.
In conclusion, due to constant corrosion resulting from salt water, there is always need to regularly maintain the equipment used. This adds significantly to the cost of power production. Thus, it can be seen that even though tidal and wave energy have their own disadvantages, their advantages far outweigh them. Based on this there is no doubt that it is the energy of the future and therefore necessary investments need to be made in this area.