It's the middle of summer. What better place to go then the beach? At the beach, one can swim, build sandcastles, get tanned, or eat hotdogs and ice-cream. But if you take your eyes off this fun, and take a few moments to observe the sea, you will notice waves splashing on the coastlines on a regular pattern. And if you venture to stand in the way of one of them, you will doubtlessly feel the immense power crashing on you and pushing you back with all its might. Welcome to wave power.

How do Waves Produce Electricity?

Wave power works more or less the same way as hydropower works - using the movement of water to turn a turbine and generate electricity. There are two types of marine-generated energy: wave power and tide power.

 

Wave power uses the regular pattern of waves on the shores to produce energy. The circulative movement of air above the oceans pushes water to the away into the coastlines. Every time a wave hits the shores, small turbines, a series of which is installed parallel to the wave lines, receive kinetic energy and produce energy. Because waves are constantly pounding the shores (a wave every ten seconds or so), wave generators are continuously producing a steady flow of electricity, day and night. However, the overall output is often small.

Tide power uses the change in the sea level to produce energy. The gravity exerted on Earth by the moon and the sun, along with the rotation of the Earth, result in a rise and fall of sea levels near the shorelines, normally twice a day. During the change of sea levels, water flows from one location to another. This flow of water is what powers those generators.

The actual difference between the rise and fall greatly vary for different places the greater the difference, the greater the flow of water during the change, and therefore the greater the energy produced. Tide power plants, in order to generate maximum energy, are installed in the region in which water passes through during the change of sea level. If installed on well-chosen spots, tide power plants generate enormous amounts of electricity a day – not continuously, but in short bursts (during the change of sea level, which takes place four times every 24 hours).

 

Advantages & Disadvantages

Like hydroelectric energy, tide and wave energy is completely renewable and sustainable. Both waves and tides happen regularly every day, and the output can generally be relied upon. Likewise, it is a clean form of energy, with no emissions whatsoever.

The disadvantages. Wave / tide power stations are often very expensive to build. In order to expect considerable output, tide power plants must be built on locations with considerably high tides (often with considerable depth) this involves the drilling of the seabed underneath and driving concrete pillars into it, after which the platforms must be built on them, with the tide swirling all around. The general environment of the high-tide areas make the construction process very expensive and dangerous, not to mention the construction itself having to go on for decades. This also makes repairing the tide power stations very tricky.

Furthermore, the enormous tide power plants critically altars the surrounding environment. The La Rance tide power plant in France, for example, significantly changed the surrounding ecosystem, causing some species to disappear and be replaced by other species unheard-of in the vicinity. As most coast-side straits and beaches are ecosystems with diverse life forms, the environmental impact of tide / wave power plants should be considered when building them.

Lastly, there are only a limited number of locations physically available for the construction of tide power plants. Same goes for wave power plants – most eligible beaches and coastlines have either been populated (i.e. cities), turned into tourist attractions, or simply too remote.

Case Study

Tide / wave power generators can be used in any country, provided there are suitable locations with considerably high velocity of water flow during tides. The largest tide power plant in the world is the La Rance station in France which generates a whopping 240 megawatts (MW) of power. The power output is so high that the electricity production cost is lower than for nuclear energy (18 Euro cents per kWh, versus 25 per kWh for nuclear source: http://www.global-greenhouse-warming.com/tidal.html).

While there are not very many tide power plants in the world, there are many wave power plants, particularly on the coasts of UK, France, Canada, and USA. The recently built tide power generator in Islay, Scotland, produces 500 KW of energy, and is drawing attention as an effective use of converting marine energy into useful energy.

Areas of Research in the Future

There could be little more done to improve the efficiency of tide power plants and wave power plants. What really needs to be solved is the difficulty, cost and time of building the power plants, which will greatly lower the price of electricity for many nations. Of course, this is not something that can be solved readily...

 

 

Citation of Images

Neilep. Tide. Digital image. Topic: Is There A Place On Earth Where There Are No Tides ? (Read 5126 Times). The Naked Scientist, 8 Oct. 2008. Web. 27 Oct. 2014. <http://www.thenakedscientists.com/forum/index.php?topic=17564.0>.

Neilep. Schematic View of Turbines Fixed at the Bottom of a Reservoir. Digital image. Tidal Power. Tutor Vista, 8 Oct. 2008. Web. 27 Oct. 2014. <http://www.tutorvista.com/content/physics/physics-ii/fission-and-fusion/tidal-power.php>.

Schematic View of Turbines Fixed at the Bottom of a Reservoir. Digital image. Tidal Power. Global Greenhouse Warming, n.d. Web. 27 Oct. 2014. <http://www.global-greenhouse-warming.com/tidal.html>.

Islay Wave Power Station. Digital image. How It Works: Wave Power Station. BBC News, n.d. Web. 27 Oct. 2014. <http://news.bbc.co.uk/2/hi/science/nature/1032148.stm>.