From the Inventor:
Humans have used wind to move and make things for centuries. Wind propels boats, pumps water, mills grain, and generates electricity to name a few. It is a naturally occurring resource available throughout the world and is free. Our challenge was to engineer a system that captured wind power to meet safety, financial, environmental and aesthetic criteria. We feel we have met and exceeded this challenge.
Below you will find Powersails™ 101, the goal of which is to describe the Powersails™ difference, how they work, the approach we took and the results we attained.
101.1 Concept Introduction
We are obsessed with wind power. The biggest barrier to wide spread renewable energy adaptation is efficiency and cost. In July of 2012 the average installation cost for small wind was $6040.00 per kw and $4750.00 for solar. Powersails™ is less than $4000.00 per kw and falls well under the average of both small wind and solar, and carries these added benefits: off-grid energy production, sustainable advertising, and State and Federal Tax credits. Small wind turbines qualify for a 30% federal tax credit and businesses qualify for accelerated depreciation credit. USDA grants are also available for farmers, ranchers, and rural businesses. Many states offer additional incentives, a list of incentives in your state can be found here. To determine what, if any, type of incentive you get, we recommend you talk with a tax specialist.
Powersails™ evolution began with the identification of inefficiencies in readily available wind turbine technologies. Through extensive testing, modeling, and dissection of scientific white papers on the subject; Powersails™ is the answer to scalable wind energy production. By systematically improving efficiency and reducing total cost, ownership for installed small wind turbines is feasible. Powersails™ now offers customers the opportunity to create power in a way like never before.
Below is a further explanation of the complete system. The main difference being three turbine subsystems:
- The prime mover : responsible for capturing power from the wind.
- The nacelle: all moving parts including the generator that converts mechanical energy to electricity.
- Tower and installation: Structural support
In terms of cost, these three categories represent most of the total cost of the turbine. The average cost break-down is as follows: 15% for Blades, 40% for nacelle, 25% for tower and installation, and 20% for transport, permits, ballast and other incidentals.
101.2 Prime Mover
Horizontal axis wind turbines are widely accepted and produce the majority of all wind power. They are primarily 3 bladed, are based on a propeller design and scalable from personal use to industrial megawatt wind farms. Depart the traditional and enter accessible wind energy with Powersails™.
Traditional method inefficiencies:
Understanding Traditional Wind: The tri-blade propeller design requires pristine winds at higher velocities to attain optimum tip speed ratios of 6 or 7. A turbines diameter and rotational speed determine tip speed ratio (TSR). Small turbines need to rotate fast to reach optimum TSR some up to 900 rpm. Large turbines rotate slow and can reach tip speeds that exceed 110 mile per hour while maintaining a TSR of 6 or 7. Models requiring a gear system or drive train convert the rotors slow rpm to the generators higher rpm rating. This trade off is torque for speed and a balance of both are needed to convert mechanical energy to electricity.
Other inefficiencies include weight, rotor tip end losses, rotor slip/slide and rotor over speed.
- Design: An airfoil / sail hybrid, NACA 4412 airfoil profile was used with adjustments to angle of attack and cord depth plus the addition of rotor end caps to meet rotational speed and torque requirements for low rpm high torque generators and geared synchronous generators.
- Weight: Manufactured with light weight alloys and aerospace processes. Options for light weight sail material range from PET / Dacron to PVC and reinforced weaved Banner material for advertising. A single 8 ft Powersail weighs 28 lbs and covers 13 ft² of surface area. 5 Sails weigh a total of 140 lbs, and cover 60 ft² at a diameter of 17.5 feet. Engineered ultra light blades are the only scalable solution for high and mid solidity rotors. This configuration has a 1.5 mph start up speed, has a 4 second response to wind gusts and at 25 mph produces 705 ft-lbs of torque with a TSR of 2.6.
- Rotor Tip End Losses: Significant energy losses occur from wind flowing off blade ends. Powersails™ use end caps that restrict air flow on the sail ends. Engineered to match the airfoil profile and sail cord depth, end caps enhance high pressure buildup on the wind ward side. This feature increased rotational speed and torque produced.
- Rotor Slip/Slide: Wind slips/slides off the rotor blades resulting in efficiency losses. Powersails™ overcome the efficiency losses with its leading edge profile, angle of attack, cord depth and trailing edge contour. These characteristics and its ultra lightweight are contributors to a low 1.5 mph startup speed and the near instantaneous response to gusts that capture additional energy.
- Rotor Over Speed: High winds and gusts cause catastrophic failure of turbines and place people and property at risk for injury or damage. Powersails™ have a multi step safety process to prevent damage from rotor over speed:
- Sail surface area and quantity are designed to use rotor solidity to create stall conditions at specific wind speeds. By using CAD modeling and CFD simulation software, the turbines solidity is engineered to reach maximum rpms relative to predetermined wind speeds.
- Sails auto release when high wind events occur. This feature minimizes surface area exposed and sails resemble flags flapping in the wind. The structural frame covers 2 ft² and remains intact allowing high winds to pass through the spars. The 5 sail 17.5 ft diameter configuration transitioning from 65 ft² of surface area with sails attached to 10 ft² with sails detached and represents an 85% surface area reduction.
- In the event of hurricanes or typhoons the recommended safety procedure is to lower the tower and remove the system from harm’s way. This is possible thanks to the entire systems light weight nature and the onboard hydraulic system.
101.3 The Nacelle
Powersails™ pair with synchronous generators using gears or asynchronous direct drive generators. Both generator types are housed with their respective support systems in the nacelle and require a prime mover to supply rpms and torque to produce electricity. Synchronous systems must be grid tied and traditionally use gears/drive trains. Asynchronous generators are direct drive and are capable of producing electricity for grid tie and off grid applications. Both have their merits and drawbacks. This component is purchased from our supply chain and system type is determined by the customers needs.
101.4 The Tower and Installation
Powersails™ have two options for installation: This element typically represents 25% of the total cost of ownership. Resources, skilled labor and site characteristics are drivers for these costs and will vary by geographic location.
- Fixed platform installation: Powersails™ unit anchored permanently on installed concrete foundation, designed and engineered for a 55’ tower and foundation. Customer responsibility on such installation includes: electronics package, monopole, project management, permitting, professional trades coordination, and maintenance.
- Power On Demand System (PODs): Structurally engineered to be both shipping container and structural platform for Powersails™. Manufactured with cost controls and ISO certified quality standards. Optimize delivery and affordability. We removed most of the additional installation costs by creating an all in one product. Monopole, foundation, and electronics are all included in the price. Site preparation and electrical hook-up are still required.