The global demand for energy is increasing at a rapid state. The prediction is for it to be 50% higher than the current levels by the year 2030. A mega portion of this demand (Close to 45%) is attributed to the intensifying development in China and India. As response, the Intergovernmental Panel on Climate Change highlights the role that renewable energy should be playing in this carbon-constrained situation of the world. The International Energy Agency has formulated a Blue Map scenario envisioning a 46% of global power being supplied by renewable energy sources by 2050. But would it be possible to expand the renewable energy sector at this pace with just hydro-power, wind energy, solar, geothermal or bio-fuels?
The concept of offshore renewable energy has been gaining wide attention throughout the past couple of decades. Although this includes offshore wind energy development, wind is not the sole source of energy that we could obtain from our vast oceans. A wide variety of engineering solutions have been invented to capture and convert the energy freely available in the ocean. Tidal energy, Wave energy and Ocean thermal energy are leading examples.
The most prominent leaders of offshore renewable energy commercialization are from the European region and includes countries such as Spain, United Kingdom, Portugal, France and Ireland. The Asia-Pacific region is also catching up with the emerging trends and the front-runners include Korea, Australia, and New Zealand. These technologies are spreading out to the developing world as well in their search for alternate energy sources in replacement of the traditional ones that are over-exploited.
La Rance tidal power station in France; the oldest tidal energy facility
The hydro-kinetic energy or fluvial energy of tides and currents are being captured by devices installed under the surface of the water. Tidal barrages or fences are widely used to harness the energy produced due to tidal height changes. They work similarly to hydroelectric dams except for the fact that water needs to flow towards both directions. Once the tide floods into a basin and a sufficient differential in height occurs, the turbines are opened and the water is allowed to flow through. Once the tidal difference erodes, the basin is refilled again. This is continuously performed and is known as ebb generation. Tidal stream farms are another method that requires the employment of turbines and other devices in the water column to extract energy directly.
The energy of the surface wind waves is also utilized to produce electricity through a variety of devices mounted on the surface regions of the sea. The type of device and the design varies depending on the location and the method of conversion of energy. Coastal methods involve attachment of energy generating equipment fixed to the shoreline. Offshore extraction involves buoyant devices installed near to the surface of the water where the energy is greatest. They require complicated mooring systems and also electrical transmission cables that should be maintained efficiently. Wave power plants usually act as wave breakers calming the sea and extracting energy from the wave train. Most are tuned to capture energy from either swell or low-frequency wind-waves. This generally represents a greater source of power compared to higher frequency waves.
An offshore wave energy converter- The device’s pistons push the water ashore via high pressure flow lines and the energy is converted to electricity through hydroelectric generators (Aquamarine Power Ltd).
Ocean Thermal Energy
Ocean thermal energy is also an interesting combination where the temperature difference between warmer surface water and colder deep waters is used to produce energy. It’s a closed loop system with a working fluid where warm water vaporizes the fluid in a heat exchanger which in turn expands and feeds a turbine that generates electricity. The cold water acquired from deeper areas are then used to condense the evaporated fluid to close the cycle and to make the circuit continuous. Land-based Ocean Thermal Energy Conversion (OTEC) devices involve pipes extending along the ocean bottom to significant levels of depth.
A 10 Megawatt OTEC plant proposed- Would be the largest of its kind when complete
Man is always ready to explore and exploit whatever is required for their own comfortable survival. Lessons from the recent history of rapidly depleting fossil fuels, deforestation, species extinctions and climate alterations should not be forgotten when embracing the exploitation of new resources. The safest option is to carry out thorough examinations on potential impacts that may be harmful to the natural habitats, the existence of species and the effects on ecosystem services provided by oceans before installations are done. The most effective and feasible measures to mitigate these impacts should also be considered. The hope is that there would not be a day when our beautiful coastal lines are covered with energy generating devices to supply the magnanimous demand being created by rapidly growing human populations.