Definition and History

Wave power is defined as being “the transport of energy by surface ocean waves.”


The earliest recorded attempted use of wave power was in 1799, when a patent was filed by a man named Girard. This was the first example of an Oscillating Wave Column.


The “wave farm” was built in Agoucadura Wave Farm, Portugal, and consists of three 750 Kilowatt devices. The machines used in Portugal work by having different sections that bend as they are hit by waves, and this flex is slowed down by hydraulic rams, which pushes oil into a hydraulic motors, which ends up turning an electrical turbine. In total, the wave farm can produce 2.25 Mega Watts of electricity, which is estimated to be enough to power 1500 homes.

"water_column_614.jpg". 18/04/10 http://celebrating200years.noaa.gov/magazine/wave_energy/water_column_614.jpg.

Benefits and Challenges of the installation, maintenance and economic viability of wave machines

Pros:

Wave systems are generally inconspicuous and would have no impact environmentally and socially when placed on offshore sites (such as the one in Portugal), and depending on the durability of the machine itself, maintenance should be inexpensive.

Cons:

Some scientists have predicted that installing wave systems could alter the displacement of sediments, which could have possible long-term negative impact on the environment.

Finding a proper site where waves are constant could be difficult in certain areas. Furthermore, if an extensive amount of cables are required, implementing a viable wave power system could be overly expensive.

The machines would need to be very durable, and would need to be able to resist extreme conditions.

OWCs inhibit fishing and also present marine navigational problem.

Well's Turbines are only 40% efficient. (Evans 109)


"File:Pelamis bursts out of a wave.JPG". Wikipedia. 18/04/10http://en.wikipedia.org/wiki/File:Pelamis_bursts_out_of_a_wave.JPG.

What is an Oscillating Wave Column (OWC)?

An oscillating wave column is a method of harnessing wave power through the falling and rising of water (ie: waves), which creates an oscillating air current, which in turn moves a Well’s Turbine.

The total potential power a wave has, provided that the wave exists in deep water (when depth is more than half the wavelength), is approximately (.5)(h^2)(T) kilowatts per meter, where h is wave height, in meters, and T is the wave’s period, in seconds.

An oscillating water column is a tube with one end submerged in water and one end open to the air. The water pushes air out of the tube every time a wave passes through the OWC. A Well’s turbine is placed near the opening which generates power regardless of the direction in which it spins. Unfortunately, most efficient turbines require a steady flow of air, and in the case of an OWC, wind speed and direction are usually very irregular.


"Efficient-Wave-Power-in-Sig_large.png". 17/04/10 http://thefutureofthings.com/upload/items_icons/Efficient-Wave-Power-in-Sig_large.png.

What is a “Well’s Turbine”

A Well’s Turbine is a turbine that was developed for oscillating wave column’s, and it uses a two-directional turbine, which makes the machine more efficient and takes away the need for things such as a “check valve system”.


"wotturbine.jpg". 18/04/10 http://www.wavegen.co.uk/images/wotturbine.JPG.

What are Floating and Hinged Devices?

One of the most common types of floating devices are Point Absorbers or Buoys, which float on top of the ocean and therefore use the propelling motion of the wave generate energy.

(Aquaret, http://www.aquaret.com/index.php?option=com_content&view=article&id=137&Itemid=280&lang=en)

The most common buoys have magnetic generators, which involves a magnet that is anchored to the bottom of the ocean and surrounded by a coil. As the motion of the waves propels the buoy up and down, the magnet also moves, creating an electric current through the coil.

There are also hinged devices or attenuators that consist of multiple floating buoys that are connected to each other by hinges. As the waves move through each of the buoys, the hinges, which are connected to hydraulic pumps or other converters, are forced to move, harnessing the energy of the wave.

What is an Overtopping Device?

An overtopping device harnesses the power of waves by creating a small barrier for the waves, which flood over the wall into a reservoir. The water then flows through turbines, similar to those of hydro dams, and them back out into the ocean. Overtopping devices also require a large amount of space to be built due to the minimum capacity that the reservoir requires function; nevertheless, the structure can be floating or built on land.

(Aquaret, http://www.aquaret.com/index.php?option=com_content&view=article&id=137&Itemid=280&lang=en)

What are the costs?

In a report published by the World Energy Council in 2005, they estimated that the cost of the energyproduced by wave power would be around 12-16 cents per kWh. However, they predicted that as new technologies are discovered and old devices harnessed, the price would drop to about 5-7 cents per kWh.(Martin BC Sustainable Energy)

The first commercialized wave energy project called LIMPET (Evans), just off the coast of Scotland, sold the energy it produced at about 14 cents per kWh.

As we compare these costs to those of fossil fuels or even hydropower, which BC Hydro now charges 6-9 cents for, we can question the affordability of such an expensive power source. However, one should still keep in mind that as demand for energy goes up and oil supplies become scarce, the cost of energy will also increase. The development of wave power technologies is also estimated to reduce the cost of the power, meaning that the possibility of wave power is definitely in the future.