Hydrokinetics 

Article by: Bryn Dixon

What is hydrokinetics?

Hydrokinetics is the study and development of energy harnessing from the natural power of water movement: waves, tidal streams, natural flow of rivers and underwater ocean currents. Although many companies have come up with extremely efficient models and working concepts  for harnessing large scale amounts of power, the environmental impacts are constantly being reviewed and researched for each individual design. Many small scale companies have started developing numerous designs because each body of flowing water acts differently in terms of the turbulence of flow and the speed associated with that flow. Although classic hydroelectric power makes up a larger source of renewable energy, it still utilizes a dam to form a pressure drop to run the generators which can have severe environmental impacts. Hydrokinetics harnesses this natural energy while minimally restricting the impact associated with their installation.

Hydrokinetics is a broad field with many ways to harness energy.  What are most promising routes of hydrokinetic power generation?

Oscillating Water Column- Using a bell shaped housing, this device floats atop the ocean surface capturing the natural rise and fall of the waves allowing the air entrapped above the waves to become pressurized with every rise. As the top of the structure becomes smaller, the force of the air becomes smaller and the speed increases which is converted to electrical energy via a compressor turbine.

Heave Surge Device- A snake-like device that rides atop the ocean surface set into the path of oncoming waves and is tethered at the front to the ocean floor. As a wave passes over the first section, a rotational motion is set forth causing the energy of rotation to increase as the wave reaches the next section. A set of hydraulic fluid pumps located in the last joint at the back of the device are forced through the rotational energy to turn a motor which converts this into electrical power through a generator.

Tidal Turbine- In accessing the underwater ocean currents or natural flow of rivers and tides, underwater turbines can be utilized much like wind turbines in converting a directional flow of energy into rotational mechanical energy. Since wind turbines have been designed and in use for much longer, many companies have turned to these designs to develop underwater turbines which harness the power in much the same way. Other companies have looked at large propellers from ships to account for the fluid dynamics involved with efficient water flow through spinning blades. Although the conventional design is to set the rotating shaft in line with the flow of the water, some have started to research the advantages of placing the rotating shaft vertical to the flow, allowing a larger surface area to come into contact with the flow, but dramatically decreasing the outgoing flow velocity.

What are hydrokinetic turbines?

Hydrokinetic turbines, much like wind turbines, operate on the principle of turning directional power into rotational power by using a certain amount of surface area to come into contact with the fluids movement over a period of time in order to harness as much power as possible. The shape, angle of deflection, and spacing of blades can drastically improve the efficiency of a turbine and is the main area of research in developing the best hydrokinetic turbine suited for its specific location of application.

This video shows a simple hydrokinetic turbine in action.   

How much power can be generated by hydrokinetics?

Estimates by the Electric Power Research Institute estimate that the total energy potential of both marine and hydrokinetic power could reach 23 Gigawatts by 2025 and even 100 Gigawatts by 2050, given the ideal amount of research and design. This could theoretically power over 67 million homes, cut back on an average 80 million metric tons of carbon dioxide emissions and is equal to the power generated by 20 to 30 coal plants. This combined total power production of all U.S. hydroelectric dams would be equal to extracting only 15% of the total energy potential that the U.S. coastal waves contain.