the Lux Wind Turbine

 

+ Comparing Vertical & Horizontal Axis Wind Turbines

Several decades ago, scientists were in disagreement as to which type of turbine would be beneficial to the industry. After extensive research on both types of turbines, the Horizontal Axis Wind Turbines (HAWT) won the battle, not because it was a great turbine but because scientists at that time were unable to solve the major problems associated with the Vertical Axis Wind Turbines (VAWT) and they were also fixated on efficiency.

Comparing vertical & horizontal axis wind turbines
How Wind Turbines Work
Wind turbines are categorized as either lift or drag turbines. The blades on lift type turbines travel faster than the speed of the wind and the airfoil shaped blades receive lift and drag similar to the wings of an airplane. Lift is the component that provides the power to the turbine. Drag wind turbines travel slower than the wind speed, have a much lower efficiency, and require more material to produce the same power as a lift type turbine. Drag machines are never used in commercial applications.

Lift wind turbines can rotate around a horizontal axis (HAWT) or around a vertical axis (VAWT). The most popular machine today is the HAWT, but we believe our vertical wind turbine can be built with less material while extracting the same or more power as the HAWT.

The Lux Wind Turbine
Our turbine is a 5 bladed VAWT. Several cables are connected between each blade in a cross pattern, which supports each blade along its entire length. This rotor is a rigid structure never seen before in the wind industry. Due to this cross cabling, the central structure/tower can be removed, which is the main reason why the turbine can be built using less materials producing a lower LCOE.

Lux Wind Power is a Vertical Axis Wind Turbine Manufacturer, but at this time, our turbine is for research purposes only. We do not claim to build the most efficient turbine, but we do believe we can build a turbine that will produce energy at a lower cost than other turbines of equal size. That is, the Levelized Cost of Energy (LCOE), which is the lifetime costs divided by the lifetime energy production, on our turbine is expected to be lower than on the HAWT.

Are Vertical Axis Wind Turbines better than Horizontal Axis Wind Turbines?
The answer is, only if the LCOE is lower. The LCOE is not dependent on efficiency or extracting power from winds high above the earth. It is simply the cost of producing energy. The LCOE of a VAWT can be lower for the following reasons:

  • The turbine requires less material to manufacture
  • Does not have to be turned into the wind
  • Major mechanical and electrical components are at ground level
  • Lower transportation and erection costs if components are modular
  • Pairs of counter rotating turbines can be spaced closer together than HAWT in a wind farm

We believe our wind turbine has a lower LCOE for all the above reasons.

+ Advantages

• The blade and cross cable system eliminates or reduces all problems associated with previous Vertical Axis Wind turbines including reduced vibrations, torque ripple and premature blade failure. The power output is improved, especially in low winds, by using an advanced blade profile and by building a rotor with a larger swept area. This is practical because the blade and cable system is light in weight and therefore relatively inexpensive. The ½ cost analysis includes this larger swept area.

• The tower at the bottom of the rotor is short but the equator of the rotor, on megawatt machines, is as high or higher than the hubs of conventional turbines, therefore, taking advantage of higher wind speeds that occur at higher elevations.

• All of the mechanical and electrical components are at ground level. This makes it easier to erect and also reduces maintenance costs and also makes it a more practical vertical axis wind turbine for residential areas.

• A yaw system is not required because this turbine accepts wind from all directions.

• The blades do not need to be pitched, which eliminates the need for the large diameter slewing bearings, retainers and hydraulic components. The blade speed and power output is controlled by aerodynamic stall.

• According to Dr. John Dabiri at Stanford University, counter rotating Vertical Axis Wind Turbines can be spaced closer together than conventional Horizontal Axis Wind Turbines https://arxiv.org/pdf/1010.3656.pdf. This is advantageous because most high wind speed sites are already occupied by widely spaced conventional wind turbines.

• The blades on the prototypes are made from aluminum, which are extruded at relatively low costs. However, since the blades experience only small deflections, they could be made from a wide range of materials or a combination of materials. Conventional wind turbine blades have large deflections, therefore, their material selection is limited.

• The blade profile is constant from one end to the other. Manufacturing this blade is much easier than manufacturing the conventional wind turbine blade, which has a profile that changes in width and curvature along its entire length.

• The blades can be made in sections and assembled like tent poles. This is possible because the blades are always in compression, unlike all other wind turbine blades that change from tension to compression through each cycle. The blade sections are easy to transport and assemble.

+ Validation

The Institute of Aerospace Research, a branch of the National Research Council (NRC), in Ottawa, Canada developed computer models of the Lux turbine and tested these models for aerodynamic and structural performance. The first model they analyzed was 40 meters in diameter and had a power output of 1MW. The results of the analysis showed the Lux Wind Turbine performed well and the blades had a life expectancy well in excess of 25 years. NRC then scaled the computer models to a diameter of 160 meters with a power output of 16MW. The positive results observed in the 1MW turbine analysis were repeated with the larger turbine.

IOPARA, a Vertical Axis Wind Turbine consulting company, in Montreal, used their CARDAAV software, which is well respected around the world, to predict the power output of several Lux Turbine models with and without cross cables. The power curves created from this software were confirmed with data collected from the prototypes. The power loss from the cross cables was low, as expected.

+ Product Development

The first generation of the 40KW Lux Wind Turbine was operational for 1½ years. It was then lowered and 7 other models were assembled and tested for various periods of time. Variations of blade curvature, blade offset angles, solidity ratios, blade profiles, drivelines and air brakes, were applied to these models, with the goal of optimizing turbine performance.

 
 

There are two options to hold the rotor in place.  

+ Guy Cable Supported Rotor

The least expensive option uses 3 guy cables that go from the top of the rotor to an anchor on the ground. This turbine does not need a central structure/tower or a robust foundation to keep the rotor upright. The guy cable and anchor system is only a fraction of the cost of the traditional robust cement foundation and tower system. This turbine can be used in most rural areas and could reduce the cost of the support structures in offshore locations as well.

+ Lattice Supported Rotor

In locations where it isn’t feasible to use guy cables, the rotor is supported by a lattice structure positioned along the vertical axis that rotates with the blades. The cross cable pattern is still utilized so the blades have very little movement even in hurricane wind conditions. This system requires a robust foundation but the blade, lattice tower and cross cable system is expected to have a cost that is significantly lower than the conventional wind turbines.

Wind Pump

A wind operated water pump

Our turbine can generate electricity or drive a pump connected directly to the output shaft. The pump on our turbine can pump water for desalination plants, water for irrigation or for pumped-storage hydro. 

How does our wind turbine pump water?  

The pump is directly connected to the vertical output shaft of our wind turbine at ground level. It has several horizontal cylinders (usually 3 or more) with one end connected to the turbine foundation and the other to a reciprocating bearing and housing on the shaft. This short video shows the frame in green, the cylinders in black and the stationary shaft in the middle. For clarity, the video shows components in a vertical position but in reality, they are horizontal and close to the ground.

 
 

Two check valves on each end of the cylinder (not shown in video) control the flow of the water as the piston inside the cylinder moves in and out; therefore, creating a flow rate. Restriction of this flow rate controls the speed of the turbine and it could be the membrane in a desalination plant, nozzles on an irrigation system or an altitude change for energy storage to be used in a hydro plant.

A HAWT wind turbine that is used to generate electricity works similar to how a windmill would pump water, but it has electrical and mechanical components that are 40% or more of the total cost of the wind turbine. The water pump does not need a gear box or specialized equipment for its operation. The pump is simple and can be maintained by anyone, anywhere in the world. This is a positive displacement pump, so the efficiency is high. The size of the wind turbine and the size and stroke of each cylinder can be modified according to the flow rate and pressure needed.

HAWT have blades that need to be turned into the wind and the output shaft is high above the ground. Therefore, attaching this type of pump to a HAWT is a difficult process. However, the shaft on our turbine is stationary and at ground level, which makes it easy to attach the pump. This water pump is an excellent device for extracting energy from a slow turning wind turbine.

Development History

2003-2005

Experimented briefly with a HAWT, then built and tested several H style VAWT.  The experiments clearly demonstrated the vibration problems with 2 and 3 bladed turbines. Started experiments with 5 or more blades of a VAWT.

2006

Built a mobile wind tunnel consisting of a diffuser, test section, contraction zone and fan.  Conducted experiments on blade profiles, bluff bodies, small VAWT with solid aluminum blades and aerodynamic drag on cables at various skew angles.

2007  

Started experimenting with horizontal cables attached to the blades of rotors with 5 or more blades.  

The blades on each rotor started at the bottom of the central structure, went outward and diagonally upward, then vertical and diagonally back to the central structure.  The joints from the diagonal and vertical blades were adjustable so data was collected using various blade offset angles.

2008

Build the first Darrieus shaped wind turbine with cross cables and struts.

2009

Hired the NRC to build computer models of this turbine with a diameter of 40 meters.  They also did an aerodynamic and structural analysis of the 40 and 160-meter diameter models.  Removed the central structure or pipe in the middle of the rotor.  The rotor was raised using hydraulics and the support from the pipe.  After the rotor was in place the pipe was removed by using cables and pulleys connected to the top hub.  The pipe weight (2000 pounds) was more than doubled by using this procedure but the blades and cables remained motionless.

2010  

Attached strain gauges on the blades and used equipment from NRC to collect data while the turbine was operating under various wind conditions.  The NRC concluded the stress on the blades was low as expected.

2011 

Constructed the Traction Drive with the small wheel on the outside of the big wheel.  The generator extracted power from this drive system.

2012  

Won first place in a worldwide competition organized by NASA’s media group ‘Tech Briefs’ and attended the awards ceremony in New York. 

Built a Savonius rotor inside the Darrieus rotor to enable the turbine to start operating in low winds.

2013

Built and tested a new traction drive with the small wheel on the inside of the big wheel.

Started the construction of the 60-foot diameter 50 KW wind turbine.

2014  

Completed the 50 KW turbine in January and collected data until March of 2016.

Travelled to Las Vegas and did a presentation at the AWEA annual convention.

2015  

Designed, built and tested a novel aero brake system consisting only of 2 ropes that extended to the equator of the rotor which prevented the turbine from over speeding in potential runaway situations. 

2016  

Designed, built and successfully tested the Lux Hydraulic Pump.  

2018  

Designed and built a 100 Kw machine tied to the grid with a 20 year PPA.

Questions & Answers

 

+ Why will the Lux wind turbine produce more power at a lower cost?

The rotor of the Lux turbine is bigger so it extracts more power, especially at wind speeds between 4 and 10 m/s (9 and 22 mph). This is significant because the majority of power production happens between these wind speeds at most wind turbine locations. The annual kilowatt hours produced by a 2MW Lux turbine is expected to be approximately 10-20% more than most other 2MW HAWT. The Lux turbine has a lower capital cost than HAWT because it does not need a tower, a pitch system or a yaw system. The blades are easier to manufacture and a robust foundation is not required. This is why we say this turbine can produce more power at a lower cost.

+ Problems such as vibrations and torque ripple were common with past VAWT. How does the Lux wind turbine negate these issues?

The Lux turbine uses 5 or more blades instead of 2 or 3. As the blade of a VAWT rotates through one complete revolution, the relative wind direction produces torque, no torque, torque, and no torque. By using multiple blades that are supported with cross cables, this torque pattern is diminished and these problems are eliminated.

+ The Lux turbine only uses a short tower or bottom structure. Does this impair the power output because the equator is lower than the hub height of HAWT?

Although it is true that higher wind speeds are found at higher elevations, the Lux turbine still extracts more power because the rotor is larger. An expensive tower is not required to produce more power. The equator on a megawatt sized Lux turbine can be as high or higher than the hub of most HAWT of equal power rating, therefore, the Lux turbine does utilize the winds at higher elevations.

+ The Lux turbine rotates at a slower speed than other turbines of equivalent rating and will require a more expensive gearbox or direct drive generator. How does this turbine deal with this issue?

First of all, a slower rotating rotor with vertical blades may be easier for birds to see and therefore easier to avoid. We use a Traction Drive system that is similar to the well-proven technology of the locomotive and rail system where steel wheels transfer 6000HP to the steel rails. Our steel on steel Traction Drive is low cost and increases the output shaft speed without using an expensive gearbox. The hydraulic pump using cylinders is also an excellent low cost method for extracting power from a slow rotating output shaft.

+ HAWT must be spaced at large distances from each other to avoid interference. Do the Lux turbines need the same spacing?

Researchers such as Dr. Dabiri at Stanford University have developed computer models and experimented with as many as 18 VAWT in various configurations. They believe that counter rotating VAWT placed in close proximity can extract 10 times more power from a given area of land than can HAWT. More research is required in this area but most people believe turbines like the Lux turbine can be spaced much closer together.

+ Can the Lux turbine operate offshore?

It is an excellent candidate for offshore use because of its very low center of gravity and lightweight. Instead of having the heavy gearbox, nacelle, generator and blades positioned high above the water level it is much easier to float or stabilize a lightweight rotor and have the heavier components such as the Traction Drive, generator and support structure near water level. Also, the components that require maintenance are at water level.