Tidal Energy – The good, the bad and the ugly

Invention of electricity has been one of the major forces behind the current progress achieved by mankind and hence the efforts are on to find new, sustainable and eco-friendly methods to generate Electricity as the current sources like coal and petroleum are fast becoming scarce and major reasons for grave issue of global warming. Tidal energy or tidal power is one of the methods tested as an alternate way to generate electricity. Tidal energy is basically the energy stored in the waves, tides and ebbs of the ocean. Ocean, as a reservoir of energy, is limitless and according to the estimates of World Energy Council the energy entrapped in tidal waves of oceans world wide is as huge as 1.5 million MW. How to harness this energy in a cost effective and eco-friendly manner is another question all together.

To establish a tidal power plant and to get the electricity in a sustainable manner it is necessary that the difference between the ocean level before and after the tide is at least 4.5 meters. The more the difference the greater is the amount of electricity generated from the installed plant. There are approximately 40 such suitable sites available around the globe and experiments are being carried by various countries on such sites, major being Scotland, Finland, France and U.S.A.
But, as with all the new technologies, there are some good, some bad and also some ugly side to tidal power also. Let’s try and understand what they are.
The Good
1. Tides are predictable
Gravitational force exerted by the moon creates tides and current in the oceans and hence the occurrence of tides and ebbs is precisely predictable as compared to solar or wind energy, both of which entirely depend on the local climatic condition. Predictability is an important condition while testing the usefulness of the project. Supply and demand of electricity varies between day and night and it is necessary that the power grid attached with the project exactly matches the variance. Precise prediction of daily tidal energy production can help in doing so.
2. Green energy
Tidal energy is a clean and green energy source. It entirely works on the concept of converting the Kinetic Energy of tidal waves in to electric energy. Because tidal power plants does not use any fossil fuels like coal or petroleum for it’s functioning, it does not emit any green house gases in to the atmosphere and there by helping to reduce the effect of global warming. Tidal energy can generate huge amount of electricity and their by helps reducing the dependence on air polluting thermal power stations. Also, it reduces the need of installing ultra complex nuclear power plants and thus reduces the danger of radiation leakage, which such nuclear plants have inherently associated with them.
3. Protect coastal ecosystems
Though not totally certified, it is estimated that Tidal Power Plants will also help in protecting the coastal marine ecosystems that are very fragile and sensitive to its surroundings. Ocean Energy Council estimates that tidal power plant like the one in Bay of Fundy, France, affects the local tides by just 15 cm which is far less than the variations caused by natural factors such as winds which can affect the tide by few meters. Also, barrages and other enclosures used in such tidal power plants helps protecting the local coastal marine ecosystems like coral reef from natural devastations such as storms.
4. Low maintenance and long operative life of tidal power plants
Simplicity of design and technology makes the tidal power plants easy to maintain as compared to other alternate sources of energy like nuclear power plants. Barrage system used for harnessing tidal energy is as easy to operate as dams. The simplicity of the design of turbines used in tidal power plants makes it possible to make very strong tidal turbines that require very few repairs and maintenance and hence, they have a very long operative life of almost 75 to 100 years.
The bad
1. High cost
Although the technology for tidal power plants is well developed and principles well established, it still remains a very expensive technology to use. It has a very high capital and establishment costs. The cost of installing a huge barrage structure is as high as constructing massive hydro power dam. Also, the cost effectiveness of harnessing the tidal energy for electricity depends largely on height and length of the barrage structure and variance between the tides and ebbs at the coastal sites which varies from region to region.
2. Low capacity factor
The other drawback of tidal energy is its low capacity in keeping up with the high and low demand of electricity during the day. gravitational force of the moon creates tides which last almost 6 hours and similarly takes another 6 hours to ebb making the whole cycle of 12.5 hours to be exact. Any part of the world thus experiences two cycles of tides in a 24.52 hours of tidal cycle which makes it difficult to co-ordinate with the demand to the existing power grid.
The ugly
1. Effect on marine life
Large barrages and turbines needs to be constructed underwater near the coastal areas for installing a tidal power plants. It is feared that such a large mechanical set-up under the water can run havoc for the coastal marine ecosystems by disturbing their natural life cycle. It also impacts coastal navigation and recreation activities. Fishes can die due to the turbine blades. Tides will not go out normally after the tidal power plant harnesses it and hence it can create and adverse situation for 80,000 plus birds feeding on mud slut after the tide goes down.
Why are we so critical?
Mild and warm waters of tide bring with them tones of nutrients on which small creatures like planktons thrive. This in turn attracts the small fishes living on planktons and the large one feeding on the small fishes. Tidal power plants can seriously harm this natural food pyramid by obstructing the natural inflow and outflow of Tidal waters.
The bottom line
It is a no brainer for anyone that the demand for electricity is going to increase as the day passes and generating it from any single source of energy is not going to serve the huge demand. Also the present major source of energy are fossil fuels which are fast becoming scarce and using them is like digging our own grave due to problems like green house effect and global warming. Alternate sources of energy are the only way forward. Though tidal Energy has its drop backs like high cost, low capacity factor and danger to marine eco system, it has emerged as one of the best renewable sources of energy and most eco-friendly.
As of now it will be too much to expect from this emerging technology to substantially replace the existing energy sources but its judicious use by more technological innovations and keeping in mind its pros and cons along with other alternate sources of energy like Solar and Nuclear Power can considerable reduce the dependence on fossil fuels and can give a new ray of hope for the Earth’s environment.

http://www.ecofriend.com/entry/tidal-energy-the-good-the-bad-and-the-ugly/