As the need for new energy sources is becoming more evident, tidal power is proving to be a formidable contender in the energy race. Tidal power is generated via the motion of tidal waves that ebb and flow daily in the world’s oceans. Tidal power is a very plausible renewable energy source that has minimal impact on the environment and could prove to provide large quantities of energy in areas that were previously being overlooked.
The Rance Estuary is the largest tidal power station in the world. It is located in northern France and was built in 1966. This massive 24 Turbine, 750 foot barrage has a peak rating of 240 MW but supplies an average of 96 MW. This amounts to an anual 600GWh which is roughly 0.012% of the power demand of France [1, 2]. As with any energy source, there are advantages and disadvantages that come with their use. Some advantages of Tidal power are that it “produces no greenhouse gases or waste, requires no fuel, has predictable tides, and has little to no environmental impact” [2]. Some disadvantages are that tidal power plants can only provide power for 10 hours a day and the conditions for potential sites are very specific [2].
A diagram detailing how tidal power is collected through a turbine and generator setup is shown below [2]:
In Korea, a “considerable effort is going into alternative energy sources that will produce fewer greenhouse gas emissions and reduce the country’s dependence on oil” [3]. A massive tidal power plant (TPP) is under consideration at Garolim Bay.” The bay is 18km long and about 8 km wide. It is unique because of its width, which has arisen from the gourd-shaped bay that has a narrow mouth with a span of about 2 km” [3]. Also, due to the fact that the “rise and the fall of the tide is nearly 7–9 m while both ends of the bay are only 2 km long,” Garolim Bay meets the necessary conditions for a functional TPP and would have a capacity of 520 MW, which is more than twice that of the Rance Estuary in northern France [3].
“Enormous amounts of tidal energy are being dissipated twice a day, every day on the world’s ocean shelves;” however, a large amount of this energy is not being utilized. Ewout Van Walsum states that there is the potential to produce “288,133 GWh of tidal energy around the world” but this can only be accomplished once the “hurdles to environmentally sustainable tidal power have been cleared” [4]. In short, Walsum believes that economic policies have to reach an agreement with environmental policies to have any hope of accomplishing such a large scale generation of tidal energy that can be utilized worldwide.
A graph from [4] showing the potential tidal power generation of the world is shown below:
The ocean possesses massive amounts of tidal energy that have the possibility to solve future energy crises. In South American countries, renewable energy sources are becoming more and more prevalent. “Portugal gets 40 percent of its electricity from renewable sources” [5]. This large percentage shows just how much potential there is for TPP’s. 40 percent may seem like a small number, but much of the tidal power available in the world is untapped. “The European Energy Association estimates that, globally, the oceans could yield more than 100,000 terawatt hours per year, which is more than five times the electricity that the world uses in a year” [5], but this is under the assumption that the technology needed to harness said energy would be perfected. Such massive amounts of untapped energy lead us to believe that in future years, we can expect to see a large rise in the number of tidal power plants globally.
Links:
[1] http://www.darvill.clara.net/altenerg/tidal.htm
[2] http://en.wikipedia.org/wiki/Rance_Tidal_Power_Station
[3] http://www.sciencedirect.com/science/article/pii/S030142150900528X
[4] http://galenet.galegroup.com/servlet/BCRC?srchtp=adv&c=1&ste=31&tbst=tsVS&tab=2&aca=nwmg&bConts=2&RNN=A110919719&docNum=A110919719&locID=txshracd2598
[5] http://green.blogs.nytimes.com/2010/10/20/tidal-power-the-next-wave/
Ianclayman's Blog 
Most of the times we tend to overview the energy process only by looking at the generation part of it. If we consider that there are no emissions during the generation using TTP then this is a great energy source. But I think it is necessary to define the energy process from the construction of the energy plant to the distribution.
One specific analysis that would be helpful to determine how “green” is aTTP, would be a carbon balance. Comparing how much carbon is not produced on a conventional power plant by using a TTP versus how much carbon was produced by installing the TTP. We know that a TTP requires a big structure and that concrete has a high carbon footprint of 150kg per ton of concrete. [1]
Calculating the amount of concrete used in the construction of the TTP would give a low estimate of the carbon foot print.
[1] http://www.greenrationbook.org.uk/resources/footprints-concrete/