Report 6 - Wind Energy Part 2

 

Report 6. Wind Energy – Part 2

By: Armando Moncada, Certified Energy Manager

(Please Note: The USPTO will NOT allow you to patent ideas that are opens source as they are already part of the public domain. 

Secondly, these ideas are being shared in an open-source manner with everyone including designers, manufacturers and researchers to discover effective means of reducing energy costs. We encourage individuals, facility owners, businesses and research centers to explore the ideas and develop them even further. This idea pool is available to the public to directly address energy efficiency within product design, in an effort to globally update our technology, reduce CO2 emissions and reduce energy consumption. Good luck, be safe and have fun!)

 

The theme of this report is wind power. This report is the second half of the Wind Energy Reports. Wind energy represents a viable means for creating energy at a low cost. The designs explored demonstrate new methods for optimizing axial wind turbines.

Examples are provided that demonstrate specific methods for designing axial wind turbines such that higher energy output can be attained per installed cost, and a shorter payback period may be realized.

 

1.      Axial Wind Turbines with Camera-Like Shutters

A simple axial wind turbine system will spin at a velocity similar to the wind passing it; however, the torque can be enhanced if the porosity of the surface normal to the wind can be increased and decreased throughout the full cycle of rotation as required. Axial wind turbines vary greatly, but a very easy to manufacture design is shown below in Figure 1.

One manner of achieving surface porosity variation is via the addition of apertures similar to camera shutters. Although the cost may seem higher, if very well made, the maintenance cost may be miniscule. Apertures that open and close similar to camera shutters are ideal if quick reaction time is desired. If the apertures open when the axial wind turbine surface is moving against the wind and close when moving with the wind, the pressure differential between the two surface is greatly increased, allowing for the net torque to increase.

In addition, the energy to open and close the shutters is a very small percent of the total energy generated. Small rechargeable battery packs combined with capacitor banks may provide the required energy storage to facilitate the shutter’s movement. Batteries are less expensive but require replacement if recharged over 1000 times. Capacitors last indefinitely if properly maintained. Their charging and discharging can be integral to the control system in a way that minimizes drag on the shaft. Charges may be uploaded from one capacitor bank to another and then to a battery pack in order to get the charge to quickly “jump” to the right place and charge the batteries. Contact with the shaft is similar to a slip ring contact but is intermittent, proportional to the time required to move the charge.

If the construction of the panel is double walled, the camera shutters and the wiring can be inserted within the depth of the panel like a triple layer system, allowing for proper routing of wires and a place to store the batteries. The batteries will only draw a small amount of power from the total power output of the generator, and the system will not be significantly hampered if the shutters are light weight and thin gauge in their construction.

 

Figure 1 (Above). Camera-like shutters are mounted on a Savonius Axial Wind Turbine. (Imagine the wind coming out of the page.) The double 2-pipe brace allows for wind to flow across the surface of the system. To minimize vibration, shutters are embedded within a double wall panel system that is reinforced internally. The structure is mounted on bearings. The electrical connection between the generator and the structure is not shown.

Shutters should be of a high strength-to-weight ratio material such that the weight is very light, but the resistance to fatigue is very high. They can be made of a fiber composite or a thin gauge metal. The material should also resist UV-degradation and corrosion from the elements. Shutters made of stainless steel with a 1/100^th of an inch thickness represent an ideal balance between weight and strength of the component.

If the designer or engineer wishes to design an orthogonal flap system similar to what was demonstrated in the previous report Wind Energy Part 1, they may do so but a separate dedicated motor might need to be employed for each column of flaps.  The shape of the turbine does not have to be adjusted.

This type of system will be heavier than other axial wind power systems so the power to weight ratio will be less, but these systems are useful in compact areas and can be installed on the corner of roofs and in urban environments. The power output per area of surface of turbine will be much higher.

Axial wind turbines can also be installed on marine vessels enabling increased power for the ship that they serve. The key advantage in this application is that they are omnidirectional. If one steers directly into the wind or away from the wind, the power output is proportional to the differential velocity between the ship and the wind. Axial wind turbines might be very suitable for catamarans, because of the ample area to install them without sacrificing the main sail in the central area. Installing points might be at the ends of each half, totaling 4 wind turbines. In another example, the four corners can be utilized as installation points and the intermediate space can be solarized for maximum power output with optional energy storage below.

 

2.      Stepper Motors and Coil Springs.

In systems where the velocity varies, or the device operates in a start stop fashion and it is required to conserve the inertia of the moving parts as much as possible, it may be effective to employ coil springs to act similarly to mechanical flywheels, in conjunction with stepper motors.

If the mechanical system oscillates between two points, instead of rotating continuously, it is very possible to employ a stepper motor to shift from one position to another and then have the ability to diminished the amperage or shut it off entirely while the spring engages.

In this case, it would be preferable to select stepper motors with electromagnets as opposed to permanent magnets in an effort to disengage the system from any magnetic field and allow it to move with low drag when the electromagnets are turned off.

The motorized system will be fully powered for only a part of the cycle because the spring coil moves the system during the parts of the cycle where there is a reversal in direction and a significant degree of deceleration followed by acceleration in the opposite direction.

The effort of conserving inertia in this manner also implies that the energy consumed will be significantly less. The best analogy would be something like pushing a child on a swing only intermittently allowing gravity to do the rest. It is obvious that the oscillatory movement of parts can be pushed by the stepper motor only intermittently. It may be required to stop the movement of the components within cycle of oscillation at points where the velocity is zero but only intermittently. If so, then a brake must be designed with enough capacity to match the tension in the coil at its maximum stress in the cycle. The brake may be as simple as a clamp that grips the component, for fractions of a second at a time, operating similar to a disk brake. Gripping the parts when they are already stopped may be considered too complex, or it may be considered a opportunity to optimize energy output even further. It is predictable that the scale of the system will drive the complexity of the system, typically.

Figure 2 (Above). A Stepper Motor and Coil Spring Assembly assists in moving components in an oscillatory fashion by conserving inertia, such as the shutter blades in the previous example.

 

3.      Axial Wind Turbines with Motor-Generators Pairs to Drive the Blade Angle

Axial wind turbines can be designed to have motors control the blade angle of the turbine. If the wave form is AC, it can be used to position the blade angles much like gear teeth ratios can be used to determine position in a sun-planet gear system. In this design what is proposed is to build axial wind turbines with motors electrically coupled to the AC generator output, such that the blades of the turbine rotate from the 0 degree position to the 90 degree position every 180 degrees that the entire system turns. The ratio allows the motors to turn at half the rate of the generator, enabling the blade surface area to maximize when moving with the wind and to minimize when moving in opposition to the wind direction, increasing power output.

The need for the generator to have an AC output is such that the number of poles in the generator-motor pair can determine the rotation rate for the motors. If the generator has 4-poles and the motors have 8-poles, the motors will turn at half the rate of the generator, enabling a simple system to be created without motor controllers. This is a way to reduce cost.

It is estimated that the energy output would increase significantly to the point that the energy generated vs. a typical system of similar size and design would be greater than 4:1, simply by enabling blade angle control. It is also assumed that the blade angle motors would consume less than ten percent of the total energy generated.

Axial wind turbines are very effective in urban environments, where one cannot easily employ large turbine blades due to noise, risk of injury and vibration. A smaller more compact system may be installed at the edge or corner of a roof where wind speeds increase in addition to typical installation sites like a windy open valley, or a mountain ridgeline.

The materials of the system can be thin double-wall metal blades, with low vibration and mass but designed to have added stiffness due to an internal structure of thin walls. Low mass blades allow for the system to speed up when gusts of wind appear, enabling a higher efficiency in energy generation.

If the materials are aluminum or stainless steel they can be recycled very easily. Printing the blades with 3D-SLS Printers to add interior structural connections is highly recommended.

It is worth mentioning that there is an alternative system for blade angle control, whereby stepper motors, a weighted flat cylindrical gyro and a spring coil is employed at the ends of each blade, enabling the spring to share some of the work and the stepper motors to agitate the system until the optimal blade angles are achieved throughout the cycle. In this system the blades do not turn all the way around but simply oscillate back and forth from the 0-degree position to the 90-degree position, (see section 2).

Figure 3. Axial Wind Turbine with Optimized Blade Angles. Imagine the direction of the wind from the bottom of the page up, with the system spinning counterclockwise. The flow force of the wind is maximized and minimized on opposite sides of the rotation cycle.

 

Figure 4. Axial Wind Turbine (Type-Darrieus w/ vertical blades) with Optimized Blade Angles. Observe the difference in cross sectional area of the blade when facing a 90-degree difference in direction. Blade motors and bearings rest above and below the structural clips that hold the blades in place. The top half of the structure rotates, along with the rotor in the generator to simplify contact connections.

 

4.      Double Axial Wind Turbines with Motor-Generators Pairs and Wind Wafers to Maximize Efficiency

Like the previous example in section 4, it is feasible to double the axial wind turbine, to seek out specific advantages.

Benefits associated with creating a double axial turbine system include a) funneling the wind into the center, using flaps to increase the wind pressure thereby increasing the efficiency and b) reducing lateral vibration, bending loads and fatigue on the main axis. The reduction is due to structural symmetry.  If the system is doubled, the wind pressure on the blades increases slightly because the air flow is partially contained by the adjacent panel on the opposite side. Additionally, corrugated flaps or wind wafers redirect wind toward the center increasing wind pressure even more. See figures 5 - 8 below.

Figure 5. Double Axial Wind Turbine, with Wind Wafers. Front View

 

 

Figure 6. Double Axial Wind Turbine, with Wind Wafers. 3D-View.

 

Figure 7. Double Axial Wind Turbine, with Wind Wafers. Top View. Wind flaps can be mechanized to adjust for different wind speeds if required.

Figure 8. Double Axial Wind Turbine, with Wind Wafers. Side View.

 

The structural base can be constructed in a variety of ways, the ideas to keep in mind are to make sure that it does not reduce wind velocity or interfere with the necessary air flow. In the image below, an example is shown where the base of the structure consists of angle iron, flat plate, and cylindrical tubing.

Figure 9. Structural Support Base. Bearings are contained within a structural enclosure, which is welded to supports.

5.      Axial Wind Turbine with Circular Shutters

Another system for generating wind power is an axial wind turbine that is represented by a rotating set of circular surfaces where circular shutters are employed to provide an increase in differential pressure between each side. In this system the cross-sectional area of each surface varies by the angle in the rotation of the entire system, allowing for the surface to become more porous to the wind when moving against the wind and nearly non-porous when moving with the wind. The shutters move from open to closed back to open every 360 degrees that the system rotates.

At the center of each plate are two axial motors that spin in opposite directions. They control eight bevel gears. Each bevel gear is tied to the central support shaft of each shutter. The system is equipped with a motor controller that is very simple. At certain points in the rotation of the system, the shutters are moved from open to closed and vice versa, but the time allowed may be governed by degrees of rotation of the entire system. In short, the motors should be able to open or close the shutters in the amount of time required for the entire system to spin 30 degrees, but if that is not possible, at higher wind speeds, due to stress on the system and limited time, then the shutter position may use a longer arc to open or close but it cannot exceed 180 degrees.

If the designer/engineer discovers that it is more optimal to spin the shutters at a constant velocity out of a need to avoid extreme stress on the components, then that is also acceptable, but the efficiency will drop slightly. It may change by up to 30 percent; the same manner that the area under the curve of a square wave and sine wave differ. The ideal would be to open and close the shutters in a manner where the parts do not fatigue and fail due to sudden acceleration and the maximum efficiency is only slightly diminished.

An alternative design may be a system where eight motors are installed between the base of the shutter and the structural ring, at the periphery instead of at the center. Although more costly, this system is also quieter and simpler to build. The cost is elevated because one has to purchase one small dedicated axial motor per shutter, totaling 8 motors per plate and 24 motors per turbine.

In summary apertures that vary the cross-sectional area allow for a pressure differential to be achieved which increases the efficiency of wind power systems.

 

 

Figure 10. Front View of Circular Shutter System

Figure 11. Side View of Circular Shutter System

Figure 12. 3D-View of Circular Shutter System.

 

Figure 13. Opening and Closing of Shutter in 5 positions.

Figure 14. Opening and Closing of Shutter in 5 positions.