The influence of terrain to enhance and enable future wind energy

Posted on November 04, 2015
Posted By: Harry Valentine
Topic: Wind
 
While many state power utilities internationally have embraced wind energy conversion to provide additional electric power, prevailing economic constraints are requiring the same utilities to make more efficient use of available capital. Evolving economic conditions have the potential to curtail the ability of many states to directly or indirectly assist development of various energy conversion technologies through subsidies or tax incentives. As a result, market forces would influence the future choices of generating technologies that would have to yield extremely competitive overall capital and operating costs as well as cost per kilowatt-hour to customers.

Present generation wind energy conversion technologies encounter a variety of challenges that include the availability of wind at the optimal velocities to assure efficient power production. At low wind velocity, turbine conversion efficiency as well as electrical generator conversion efficiency becomes drastically low. While high wind velocities suggest higher turbine efficiency and much greater power output, wind turbines may be locked down to either prevent breakage of the turbine blades or inability of the tower-mounted electrical generator to convert elevated quantities of kinetic energy to electrical power. Future designs of turbines would need to resolve such issues.

Multiple Generators:

The design of traditional towers for horizontal-axis, 3-bladed wind turbines (HAWT's) place restrictions on the weight and dynamic loads that the turbine may carry. While vertical-axis wind turbine (VAWT's) designs may offer lower conversion efficiencies than the horizontal axis competitors, the ground level placement of the electrical generator allows for the possible installation of a larger and heavier generator that could operate during periods of extreme elevated wind velocities. The ground level location also allows for the option of multiple generators, possibly up to 5-units in a 1:2:4:8:16 output ratio, an arrangement better suited for multiple connected turbines.

The possibility of mechanically linking multiple turbines on a single drive system to drive multiple generators could be cost competitive against traditional turbine systems. Except that such a system would restrict the size and weight of multiple interconnected horizontal turbines that could change direction with the wind and drive interconnected generators that a tower could carry. An alternative installation system could utilize the nature of the terrain at select locations to mechanically connect multiple turbines that simultaneously drive a battery of generators. Such installations may have to be based on cable suspension bridge concepts.

Cable Suspension Systems:

The engineers of the Mayan Empire were believed to be the first builders of suspension bridges across mountain chasms. There are locations around the world where predominantly unidirectional winds blow through fiords, ocean inlets and steep sided valleys, chasms and gorges. Such locations offer the possibility of connecting a cable system at high elevation across these passages, perhaps to allow a few vertical-axis wind turbines (VAWT's) to be built to extreme height with some of the weight being suspended from above by cables, with additional cables providing horizontal stability to a vertical stack of VAWT's.

The assembly would generate the output of multiple turbines and drive a vertical assembly of electrical generators located at or below ground level, offering peak generating efficiency at 15 or even 31-levels of output. When wind speeds become extreme, the generator assembly may still be capable of restricting turbine rotational speed when horizontal-axis wind turbines (HAWT's) would need to be shut down and set to neutral. An alternative arrangement would involve a cable suspension system carrying VAWT's set to operate in transverse-horizontal-axis mode, with flexible drive couplings between each turbine and generators built into the valley walls.

Diagonal-Concentric Horizontal Axis Turbines:

While HAWT's and their transverse-axis equivalents have operated in single units, California based wind turbine builder Douglas Selsam has actually built and demonstrated an installation that involves multiple small-diameter VAWT's on a single, extended length drive shaft that is set at an angle to the prevailing wind direction. The span of some cable suspension bridges approaches 10,000-ft and indicates the possible diagonal distance that may be achieved in an extended valley with relatively steep sided walls. A diagonal cable suspension installed along a valley allows for installation of transverse cables at regular intervals to provide a measure if lateral stability.

A multi-rotor VAWT system installed diagonally along a valley would require flexible drive couplings at regular intervals and be able to drive multiple generators secured to the valley walls at both ends of the driveshaft system. The combination of small rotor diameter that can operate in high-speed winds and multiple generators offering multiple levels of power output at peak generator efficiency, could continue to generate power when other competing designs of wind turbines would need to be shut down to prevent their self-destruction. During such wind speeds, an elevated multi-rotor could likely achieve the output of much larger turbines.

Conclusions:

The future cost competitiveness of wind turbines would include the ability to convert the kinetic energy of high-speed wind to electrical power. Over the next decade, economic constraints would require governments to reduce direct and indirect subsidies to various segments of the energy sector. As a result, alternative wind energy technologies such as airborne turbines and terrain enabled wind power technologies with superior cost performance and higher availability, would likely emerge.

 
 
Authored By:
Harry Valentine holds a degree in engineering and has a backround in free-market economics. He has undertaken extensive research into the field of transportation energy over a period of 20-years and has published numerous technical articles on the subject. His economics commentaries have included several articles on issues that pertain to electric power generation. He lives in Canada and can be reached by e-mail at harryc@ontarioeast.net .
 

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