Levelized Cost Of Energy


The Coefficient of Power (Cp) measures the efficiency of the turbine and equates to the amount of energy extracted divided by the total amount of energy in the wind.  Even though the Cp of a HAWT is higher than the Cp of a VAWT (about 50% versus 45%) this should not be the main factor when evaluating the two types of wind turbines.  The most accurate evaluation tool is the Levelized Cost of Electricity or Energy (LCOE), which is the sum of all the costs over a lifetime divided by the sum of all the revenue from the electricity produced over a lifetime.  The Lux wind turbine is expected to have ½ the LCOE as a HAWT for the following reasons.  

First, I will compare the expected power output through the lifetime of the turbine.  The last 50 KW prototype that I built was in operation from February 2014 to March 2016 after which I took it down to build the rotor without guy cables.  IOPARA in Montreal, did an aerodynamic analysis of the rotor using their CARDAAV software program.  The mechanical (shaft output) power curve they created was similar to the data collected from the prototype.

If we take the data from the curve in red and multiply this by 100 the power curve would be for a 5 MW wind turbine.  Obviously the blades would have a larger chord length and the Reynolds Number would be higher yielding a higher coefficient of lift, a lower coefficient of drag and a higher power output, but for comparison purposes let’s assume the power output is directly proportional.  The chart below shows this curve with the NREL 5 MW Reference Turbine http://www.nrel.gov/docs/fy09osti/38060.pdf page 32.

It is clear the scaled up 50 KW turbine would extract more power than the NREL reference turbine through a 20-year lifetime, in fact it is close to doubling the power output.

Second, the total cost for all the materials of the 50 KW prototype rotor, which replaces the blades, hub, tower, foundation, yaw and pitch systems on a HAWT, was $6,500 US or $130/KW, which did not include any volume based discounts or assembly costs.  If we assume these components on a HAWT cost 50% of the total cost of $1,200/KW US than these costs are $600/KW.  The $130/$600 cost reduction is only valid if the cost/KW does not increase as the turbine increases in size.

The Institute of Aerospace Research, a branch of the National Research Council of Canada (NRC), in Ottawa, used computer models to analyze a 1 MW Lux wind turbine.  Both the 50 KW and the 1 MW turbines used an aluminum blade with a 1/8-inch thickness.  The figure below, from the NRC report, shows the maximum stresses expected at various wind speeds.  If the stresses were multiplied by a factor of 4 (a comfortable safety factor) according to the report, the life expectancy of the blades would still be 62 years.  It is clear the 1/8-inch thick blades on the 1 MW turbine could be made with thinner material. 

If we assume the materials are scalable, since the blade thickness does not increase, the rotor material costs would still be $130/KW US.  Since the life expectancy of the blades, with a safety factor of 4 is beyond the 20-year period, this $130/KW value could be applied to larger turbines as well but at some point the material thickness would need to be increased. 

These are some of the reasons why I believe in the ½ LCOE theory but there are a few more things to consider.  Look closer at a few basic engineering principles to compare the two types of wind turbines.  HAWT use cantilevered blades and a cantilevered tower, which means, each of the blades and tower are supported only at one end.  This is similar to sweeping a floor with one hand at the end of the broom stick.  Engineers avoid using cantilevers wherever possible because cantilevers require more material.  Structures that require the least amount of material are supported in several places.  This basic principle can be seen in nature and the majority of products built by mankind.    

In contrast, the multiple (six or more) Lux wind turbine blades are supported at each end and cables are attached at various positions along the blades entire length.  This fully supported system is in direct contrast to the cantilevered blades and tower of the HAWT.  The cables cross each other and when looking from the top down, each cable forms a hexagon, which is close to a circular shape.  This shape ensures that the aerodynamic drag from the rotating cables is kept to a minimum.  The cross cables and blades create a rigid structure similar to the shape of a football.  This structure is also similar to the geodesic dome, which popularized the slogan “doing more with less”.

The forward-looking material presented here may not be the proof needed by everyone in the wind industry but if we are serious about lowering the cost of wind energy it cannot be discounted without further investigation.  I have invested time and money to bring it this far but I need help to go further.  I have the support of many scientists around the world but I need a partner or organizations willing to continue the research and development.  I am also willing to license the technology to companies that show an interest for further research and development.