Transonic flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic flow is seen at flight speeds close to the speed of sound, typically between Mach 0.8 and 1.2.
The Darrieus wind turbine is a type of vertical axis wind turbine (VAWT) used to generate electricity from wind energy. The turbine consists of a number of curved aerofoil blades mounted on a rotating shaft or framework. The curvature of the blades allows the blade to be stressed only in tension at high rotating speeds. There are several closely related wind turbines that use straight blades. This design of the turbine was patented by Georges Jean Marie Darrieus, a French aeronautical engineer; filing for the patent was October 1, 1926. There are major difficulties in protecting the Darrieus turbine from extreme wind conditions and in making it self-starting.
Wave power is the capture of energy of wind waves to do useful work – for example, electricity generation, water desalination, or pumping water. A machine that exploits wave power is a wave energy converter (WEC).
Wave Dragon is a concept wave energy converter of the overtopping type, developed by the Danish company Wave Dragon Aps. Incoming waves flow up a ramp into a reservoir, the water the drains back to sea level though a hydro-electric turbine, generating electricity. "Reflector arms" are used to focus incoming waves, to channel the waves towards the ramp, increasing the energy captured.
Airborne wind energy (AWE) is the direct use or generation of wind energy by the use of aerodynamic or aerostatic lift devices. AWE technology is able to harvest high altitude winds, in contrast to wind turbines, which use a rotor mounted on a tower.
The Gorlov helical turbine (GHT) is a water turbine evolved from the Darrieus turbine design by altering it to have helical blades/foils. Water turbines take kinetic energy and translate it into electricity. It was patented in a series of patents from September 19, 1995 to July 3, 2001 and won 2001 ASME Thomas A. Edison. GHT was invented by Alexander M. Gorlov, professor of Northeastern University.
Unconventional wind turbines are those that differ significantly from the most common types in use.
An OE Buoy or Ocean Energy Buoy is a floating wave power device that uses an Oscillating Water Column design. It is being developed by Irish company Ocean Energy Ltd., based in Cork, in collaboration with the Hydraulics and Maritime Research Centre at University College Cork, Queen's University Belfast, and Marine Institute Ireland.
Oceanlinx was a company established in 1997 which specialised in the research and development of ocean-based renewable energy technology. The company's central technology was based on the Wave Energy Converter "WEC" which converts wave energy into electrical energy. Oceanlinx technology focused on the oscillating water column principle, and developed several prototype generators which were deployed and tested in Port Kembla, New South Wales. In 2014, Oceanlinx entered receivership and its technology, intellectual property, brand and trademark were sold to Wave Power Renewables Limited in Hong Kong. Wave Power Renewables Limited has continued to develop the technology, and Oceanlinx's founding director, Tom Denniss has further developed the technology since 2016 as a director of Wave Swell Energy.
The Wells turbine is a low-pressure air turbine that rotates continuously in one direction independent of the direction of the air flow. Its blades feature a symmetrical airfoil with its plane of symmetry in the plane of rotation and perpendicular to the air stream.
Islay LIMPET was the world's first commercial wave power device and was connected to the United Kingdom's National Grid, in November 2000. The device was initially rated at 500 kW, but this was later downrated to 250 kW. The device was eventually decommissioned in 2012.
Evopod is a unique tidal energy device being developed by a UK-based company Oceanflow Energy Ltd for generating electricity from tidal streams and ocean currents. It can operate in exposed deep water sites where severe wind and waves also make up the environment.
Marine energy or marine power refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences. The movement of water in the world's oceans creates a vast store of kinetic energy, or energy in motion. Some of this energy can be harnessed to generate electricity to power homes, transport and industries.
A tidal stream generator, often referred to as a tidal energy converter (TEC), is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from the run of a river or tidal estuarine sites. Certain types of these machines function very much like underwater wind turbines and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis.
The Mutriku Breakwater Wave Plant is a wave power plant constructed by Ente Vasco de la Energía (EVE), the Basque energy agency, in the bay of Mutriku in the Bay of Biscay. It is the world's first breakwater wave power plant with a multiple turbine arrangement. The plant has a capacity of 296 kW from 16 turbo generator sets. It was inaugurated on July 8, 2011.
MARMOK-A-5 is an offshore electrical power generator that uses wave energy to create electricity. This device is a spar buoy installed in the maritime testing site BiMEP, in the Bay of Biscay. It is the first grid-connected maritime generator in Spain, and one of the first in the world.
India has a long coastline of 7517 km marked along by numerous estuaries and gulfs which makes it attractive for the development of marine energy projects. India's wave power potential is around 40-60GW. However, compared to the developments in other renewable energy technologies, ocean energy technologies like wave and tidal are in their nascent stages of development in India.
A vertical-axis wind turbine (VAWT) is a type of wind turbine where the main rotor shaft is set transverse to the wind while the main components are located at the base of the turbine. This arrangement allows the generator and gearbox to be located close to the ground, facilitating service and repair. VAWTs do not need to be pointed into the wind, which removes the need for wind-sensing and orientation mechanisms. Major drawbacks for the early designs included the significant torque ripple during each revolution, and the large bending moments on the blades. Later designs addressed the torque ripple by sweeping the blades helically. Savonius vertical-axis wind turbines (VAWT) are not widespread, but their simplicity and better performance in disturbed flow-fields, compared to small horizontal-axis wind turbines (HAWT) make them a good alternative for distributed generation devices in an urban environment.
