Alternative Energy Part 2: Wind, Water and Sunlight: Tidal Energy

Ok, I last left off talking about alternative energy and I discussed the problem of fossil fuel reliance. The best options for energy would be wind, solar, geothermal, tidal or hydroelectric. These sources are grouped together and abbreviated as WWS, since they are all created by wind, water or sunlight. Personally, I think the most potential is in solar energy; solar and wind combined would be ideal. There is a myth that only sunny places can utilize solar power effectively, but actually, solar panels can be effective even on cloudy days. Wind power seems like it would be a good complimentary power source. The idea with alternative energy is combining sources, so that each source contributes to the system as a whole to maintain a constant sufficient energy supply.  I’m going to give an overview of the various alternative energy sources scientists are exploring today and analyze their potential pros and cons.

Many questions begin bubbling in my mind when it comes to alternative energy – and specifically in comparing its environmental impacts to fossil fuel.

  1. What would the cost and time be to create an infrastructure for this new type of power supply?
  2. What would we have to change in the following areas/places: manufacturing processes, factories, office buildings, and homes?
  3. What would the individual costs be i terms of the utilities bill?
  4. Where would this energy source be located? Would it affect the ecosystem?
  5. How easily integrated into society could it be? As in, could we take this technology and apply it to things that already exist?
  6. What would the scale need to be to generate enough electricity? (A source of energy would still be impractical and inefficient if it had to be massive in size and it took space away from other necessary parts of life such as forests or farmlands.)
  7. From a cradle-to-cradle perspective: what are the materials being used? How are they made? How much energy is required to produce these materials? Are these materials renewable or non-renewable? What is the waste impact – are they biodegradable or would they fill a dump and leech toxic chemicals into the air and soil?

Tidal Energy:

The first renewable energy source I want to explore is tidal energy, since I have never even heard of this option before. I would guess it’s not very well known, but from my research, I’m finding that it is actually more reliable than solar and wind power options; the problems have been cost and the very few places on the earth where this could work.Advances in technology and design have opened doors more recently to developing this method further. Tidal energy is created by gravitational forces between the sun, moon and earth that causes each coast to have two high tides and two low tides within a 24-hour period. In order for the energy to be gained from this source, the difference in the high tide and the low tide must be at least 16 feet. While tides are predictable and their size can be reasonably well estimated, there are not many places on earth where the 16 feet difference happens consistently. There are two types of methods for capturing tidal energy, and this is where the biggest problem occurs with tidal energy. These methods of using tides to create electricity extremely affect the ocean’s ecosystem.

Rance Tidal Plant

The first method of capture is called a barrage or dam. There are only three barrages in the world currently, with France’s Rance Tidal Plant (built in 1966) being the largest in the world. In a barrage, water is forced through a turbine to create electricity. This happens when the water level on each side of the barrage has reached a great enough difference. Gates open to allow water to flow through, activating the turbines. The barrage is like a dam, but on a much larger scale. It sits at the opening of a bay to catch water as it moved in and out with the tides.

Barrages have extreme environment and economic impacts that must be accounted for in considering them as an alternative for energy. Barrages are expensive to build initially, although they don’t require expensive maintenance once constructed. They also take a long time to construct, and in the meantime the area has to deal with increased traffic, road blocks and


construction noise. The Rance barrage took five years to build. Although barrages can be useful as roads across a bay, unless they have a feature allowing them to swing open like Seattle’s 520 floating bridge, boat access to the bay is cut off. This could possibly have social and economic impacts upon the coastal town or city. More significant is the environmental impact of barrages. A barrage affects both plant and animal life as it alters the natural flow of the water in and out of an estuary or bay. Fish can easily get killed in the turbines, and the bay’s water quality can decrease as a result of the barrage acting as a road block to the dispersal of contamination. The Rance plant is a good example of the environmental damage that can occur. Because of the barrage, sandbanks disappeared and many species lost their habitat. Other species moved in actually, which changes the diversity of the ecosystem. It is easy for us to disregard changes in diversity and species, but it is one of the biggest environmental impacts humans have and it must be better understood. Changing an ecosystem has profound and last impacts, and regardless of how much people alter their surrounding and separate themselves from the natural environment, we have to understand that we are actually a part of the greater environment, and destruction or changes to nature will eventually impact us.

Underwater turbine

The second method of tidal energy capture is tidal turbines. Underwater turbine technology is much newer than tidal barrages, and they are similar to wind turbines. These are placed at the entrances of bays or rivers where there are fast currents to move the turbines. Since water is denser than air, more energy can be extracted through spinning turbines with water than with wind.  These turbines need to be in water about 60-120 feet deep, and in an offshore or estuary location with winds of at least 5-6 miles per hour. An underwater turbine farm was constructed in 2006 in the East River of New York City, and they are hoping for expansion of that project that will have a generating capacity of 10 megawatts. That would generate enough power for several thousand homes in the city. While turbines are less environmentally destructive than barrages, they are still taking up permanent space in the ocean that aquatic flora and fauna should have free range of. There have also been concerns about the machines being overrun by barnacles and other sea life of that nature.

While tides are reliable and predictable, tidal energy can only be captured during the high and low tides, which totals about 10 hours each day. From that standpoint, combined with the large scale and serious ecosystem impacts, I don’t see tidal energy as a viable solution to clean energy. It is my personal opinion that we should opt to find energy solutions that can be utilized on various scales of size and not alter the environment this much. In finding alternative energy sources, I think it’s important to find one that doesn’t take up undeveloped space. This is why I am hesitant that developing turbines are barrages in water is a good idea, since it expands our development even further, rather trying to incorporate energy production into already developed areas like cities. I think that we should look to solar energy for meeting our needs of the future. And my next post will explore this option!

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