The horizontal-axis wind turbine has had a good run but it’s time to consider other designs for greater efficiency and a much shorter ROI.
A Chinese businessman recently sought advice on different U.S. investment opportunities. The gentleman was considering the purchase a huge wind farm and expecting to reap great profits, so interviews were arranged with several prospective sellers. The outcome, however, was not as anticipated because the investor calculated that the ROI – the payback – would take 40 years.
The anecdote suggests it’s time to examine the challenges of wind power by looking at financials and efficiency in a different way. In particular, a way that has to do with recouping investments in a shorter period than allowed by conventional models. Ideally, it would involve a new turbine design and an approach to manufacturing grown here in the United States and based on readily available data from over the last decade.
Consider the financial situation in Europe: Governments there are willing to subsidize energy paid for by folks willing to accept higher taxes. Things are different in the U.S.
With regard to wind-power efficiency, it should not be based on wind-capture efficiency, electrical-generation efficiency, or rotor loading, but rather on an ROI cost/kW and based on a three-year payback period.
A brief analysis
An epiphany came after successfully reducing the cost and manufacturability of a support structure for a 1 MW, three-blade wind turbine. The client was pleased because we had achieved savings higher than expected. Were similar gains possible from other components?
The current state of the wind-turbine industry (including cost, efficiency, scalability, and other issues) deserves attention before proposing ways to improve the current situation by increasing efficiencies, scalability, reducing cost, and providing a wider range of products.
For more revealing calculations, one must first have accurate wind speeds for different areas of the United States. Then, it is necessary to understand acceptable losses to get power from where generated to where used. How close can the turbines be spaced? Where can they be built? How much does land or easements cost?
Calculations then call for costs and efficiencies of all the prospective turbines available, manufacturing, shipping, and installation costs, ongoing maintenance and lifetime costs as well as the height needed to work at max effectiveness. A more complete list of information includes:
• Transportation and install costs
• Operational range
• Capital Costs
• Transmission design
• Maintenance costs
• Performance in turbulent air
• Replacement costs
• Energy to start, heat, yaw the turbine
• Number of parts and weight
• Land requirements
• Product availability
• Energy to manufacture
• Environmental issues
• Efficiency when blades not at right angle to airflow
• Complexity of feathering blades
For a more detailed analysis, consider the table below. Look at the pay back years in the last column. No wonder the Chinese investor was disappointed.
Turbines could be chosen from horizontal (conventional) and vertical axis designs. From an aerodynamic standpoint, the uni-directional horizontal rotor seems well suited and has a peak efficiency of about 45%.
Problems with convention
What does one find when studying the problem of trying to profit from a wind-power product? Several things including land use and scalability of the turbine.
A conventional wind farm requires quite a bit of land and siting at least a mile away from existing residences. Those two points should be in the business plan.
Unfortunately, business plans have also excluded small turbine developments. They have been disregarded as toys for architects or playthings for unsophisticated householders. But there is always overlooked opportunity, so let’s consider the plusses and minuses of both designs. Start with the table below.
With a cost-versus-profit based on a 36-month payback, nothing with conventional three blades can win unless it is subsidized to offset its costs.
A modest proposal
To meet some of the conventional challenges, consider the advantages of the power consumer living immediately below the power source. For all the engineering rational suggesting that Vertical Axis Wind Turbines (VAWTs) will not work, it is still easy to imagine many omni-directional wind turbines on top of large flat-roofed buildings in windy cities such as Chicago. This concept eliminates the distribution cost and electrical losses, while efficiently using non-value added space.
VAWTs have not been explored and exploited because U.S. developers followed the European model. But “up-sizing” a small-wind VAWT and stacking turbines to create a “wind wall” shows an inexpensive way to tap a natural resource and create electricity in an urban environment.
The problem and solution have been under study for several years. A prototype VAWT has been selected for its good performance chacteristics. It’s rotor measures 8 ft tall by 6 ft wide. Furthermore, these rotors could be ganged or stacked to drive a single generator at the base. For example, a 36 x 32-ft (w x h) array would use a total of 24 vertical-axis rotors stacked four to a column driving a 25-kW generator at the base of each. Six columns provide a total of (6 x 25) 125 kW.
Because these are smaller than the megawatt units require by conventional wind farms, they lend themselves to mass production which drives down costs. In addition, less costly transport and handling would require no special equipment.
Furthermore, the proposed and promising generator uses a covetic nano-copper alloy. Its thermal conductivity increases in excess of 60%, electrical conductivity increases greater than 40%, and fusing current increases in excess of 70%.
A brief turbine comparison of a conventional three-blade unit to the candidate design is thus: A three-blade turbine has a swept area of 21,125 ft2 , which generate 1,000 kW. Therefore, each square foot generate on average 47 W. The proposed vertical axis turbine can generate 50W from each square foot of blade cross section at ground level. At 100 ft up, the output doubles to 100W, and to 150W at 200 ft. These are baseline figures that do not include performance increases likely from array configurations. For instance, Caltech’s John Dabiri found that designing an array of VAWTs for counter rotation (CW, CCW, CW, and so on) significantly improved the array’s power output. WPE
By: Sandy Munro, CEO Munro & Associates, Inc., www.leandesign.com and Tom Scott, inventor and consultant
Filed Under: Transformers