“Turning The Tide”.
Energy prices are approaching unmanageable heights and it is generally accepted that the burning of fossil fuels has contributed immensely to the problem of climate change. Consequently, one cannot help but wonder why Tidal Power is almost never utilised, bearing in mind the fact that it is probably the world’s most widespread source of clean, renewable energy.
Only Geothermal energy (using the heat that radiates from the earth’s molten core to its thin outer crust) could provide an equally abundant and reliable supply of power. However, the extraction process requires highly specialised technology and the feasibility of its location is governed by the thickness of the earth’s crust at the place in question.
In complete contrast, tidal movements and ocean currents are worldwide and readily accessible. In fact, it has been calculated that the daily tidal flows in the English Channel contain more energy than the total number of munitions explosions of the Second World War (including the two nuclear devices). Nevertheless, no modern turbine design has been implemented to extract this plentiful supply of energy for the benefit of mankind, and there is no satisfactory explanation for this situation.
The French do have an operational Tidal Energy system at La Rance, but it is over 30 years old. It is a barrier system which dams the flow across a small bay and forces the water through special ‘bulb turbines’ to produce electricity by day and by night. It is perfectly capable of functioning for another 30 years or more, but I often wonder why nothing new has been introduced to extract some of the remaining untapped energy.
In my view, much of the related research and design work has been compromised by the erroneous assumption that a design that will function efficiently in the wind will operate equally well beneath the water.
That assumption fails to take into account the fact that the speed of the wind is usually much greater than that of the water (i.e. a Wind Turbine revolves much more quickly than a Water Turbine). Furthermore, air compresses while water does not. Consequently, a fast-turning Wind Turbine imparts inertia to the generation of the power while a Water Turbine, turning slowly, does not.
Even more significantly, many designs lack sufficient blade-contact with the energy-capture area. To illustrate this factor, simply put your head around the corner of a wall when a very strong wind is blowing. Your hair blows wildly and your eyes might stream, but you are perfectly safe. However, if you step out completely from behind the wall, you can be blown dangerously off your feet. The functional ‘bulb turbines’ at La Rance are ducted with very large blades which cover more than eighty-per-cent of the water flowing through them, whereas many of the propeller-type designs being researched rely on contact with less than twenty-per-cent of the energy flow. How can the latter possibly be expected to operate efficiently?
Unless this or any future government stops placing all the research money on proposals that are based solely on pretty computer-generated animations and funds a centre where developers can fully test their basic prototypes, we will completely miss the opportunity to investigate this renewable source properly and we will be forced to fall back on nuclear power as the only alternative. That scenario is not, I suggest, particularly desirable.
Written by John C. Jones.
