Understanding tidal power

Engr Sabir Hussain

Energy is produced from the gravitational pull from both the moon and the sun, which pulls water upwards, while the Earth’s rotational and gravitational power pulls water down, thus creating high and low tides. This tidal power in the sea possesses enough power to rotate tidal turbines, which operate under the sea. These undersea turbines which produce electricity from tides are the main sources of renewable energy in many countries. They operate on the same principle as wind turbine, but the power in the sea turbines comes from the tidal currents which turns the blades like the ships’ propellers.

Unlike wind, the tides are predictable and the input power is constant. The gravitational forces of celestial bodies are not going to stop anytime suddenly. Furthermore, as high and low tide is cyclical, it is far easier for engineers to design efficient systems, than, say predicting when the wind will blow, or when the sun will shine. It is an effective solution to reduce carbon emission and an attractive solution to overcome the crisis of energy in Pakistan. Furthermore, it can raise the prospect of the country becoming not only self sufficient in renewable energy, but also can export to other countries.

Tidal power plants can last much longer than wind or solar forms. Tidal barrages are long concrete structures usually built across river-mouths. The barrages have tunnels along them containing turbines, which are turned when water on one side flows through the barrage to the other side. These dam-like structures are said to have a lifespan of around 100 years. Wind turbines and solar panels generally come with a warranty of 20 to 25 years, and while some solar cells have reached the 40-year mark, they typically degenerate at a pace of 0.5% efficiency per year. The longer lifespan of tidal power makes it much more cost-competitive in the long run. Even nuclear power plants do not last this much long.

A marine turbine blade needs to be only one third of the size of a wind turbine to generate three times as much power as wind turbine. Each turbine will need to be mounted on a tower which will be connected to national supply grid station through underground cables. The tower will be lifted out of the water and enlightened to indicates ships of their existence. Work for the design of sea turbine blades and current sites are being carried out at the university of the Southampton’s sustainable energy research group. The largest tidal project in the world is the Sihwa Lake Tidal Power Station in South Korea, with an installed capacity of 254MW established in 2011.

Compared to wind power, there are less likelihood of environmental objections. In addition, fish and other creatures are thought unlikely to be at risk from relatively slow turning blades. However, a report commissioned in 2010 by the US National Oceanic and Atmospheric Association, titled ‘Environmental Effects of Tidal Energy Development’ identified several environmental effects, including the “alteration of currents and waves”, the “emission of electro magnetic fields” (EMFs) and its effects on marine life, and the “toxicity of paints, lubricants and anti-fouling coatings” used in the manufacturing of equipment. Electro-magnetic emissions might also disrupt the sensitive marine life. Species that are susceptible to EMFs are sharks, skates, rays, crustaceans, whales, dolphins, bony fish, and marine turtles. Many of these animals use natural magnetic fields to navigate their environment.

According to a study, the EMF will cause the eels to divert from their instinctual migratory route. Also, installing a tidal system is technologically challenging. Manufacturers are competing against the moving ocean. The equipment and technical knowledge are needed to successfully construct the system. Companies managing a tidal power system need to conduct continuous analysis into the effect it has on the specific environment in which they are operating. This requires research and assessment from environmentalists, marine biologists and geographical experts to mitigate the destruction of sensitive ecosystems.

The writer is a satellite engineer by profession. He did B.Sc Electrical Engineering (Telecom) from the COMSATS University, Lahore Campus and M.Phil in Space Science from the University of Panjab, Lahore. He can be contacted at: engineersabirhussain14@gmail.com.

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