Editor's note: This Q&A is a part of a survey conducted by Scientific American of executives at companies engaged in developing and implementing non–fossil fuel energy technologies.
What technical obstacles currently most curtail the growth of wind power? What are the prospects for overcoming them in the near future and the longer-term?
Whether they are built on land or at sea, nearly all wind turbines have the same technical issues related to the fact that wind is naturally variable. Today the best machines in the best spots now offer about a 35 percent "load factor," or efficiency level. The largest problem in turbine design is not the blades, but what we can't see. It's the guts of the machine—the engineering components housed in the nacelle, or body, of the turbine, which convert that kinetic energy into electricity—that need improvement.
The main workhorse of the nacelle is the generator. First developed in 1831 for the coal industry, these machines move copper wires past magnets to convert mechanical energy into electricity. The basic premise of the system hasn't changed very much. Generators thrive on a stable input energy source, such as coal or hydroelectric power, and with this stable prime mover they can operate at their peak efficiency upwards of 90 percent. This level of energy input is called the "sweet spot." Unfortunately at speeds outside the sweet spot the efficiency of the generator drops dramatically and a great deal of available energy goes to waste.
If the wind rises above this sweet spot, the shaft will accelerate and the torque will exceed the generator's capacity, so engineers "pitch" the blades, literally turning them out of the wind, and allow the excess energy to blow past, in essence pretending the wind is still blowing at a steady 30 miles per hour. If the wind drops below the sweet spot, the shaft will slow down, causing a drop in generator efficiency. To compensate, engineers engage the gearbox to artificially speed the shaft. The gearbox "tricks" the generator into thinking the wind is still blowing steady, but major efficiency losses result.
The gearbox, the Achilles' heel of wind power, has many moving parts that require frequent maintenance and often cause turbines to be out of commission for up to 10 percent of the time. In addition, they are so heavy that rare and expensive cranes are required to lift the generators into their nacelle housing, bottlenecking construction projects. Finally, to increase the strength of generators, engineers traditionally expand the machine's diameter. This limits their size to the width of roads, or else they could not be transported.
For offshore wind, the industry will need to address reliability and technical difficulties by designing more robust and reliable equipment. First, ports are often not well suited to manage the sheer size of offshore turbines. Secondly, offshore turbines have a very high failure rate and are even more expensive to fix than turbines onshore. Here again, the gearbox proves to be the Achilles' heel of wind power generation. In addition, offshore turbines must battle harsh elements and the rusting properties of saltwater. Like onshore failures, offshore problems have the potential to cripple returns for developers.
These technical challenges mean only wind sites with high wind gusts are currently viable for wind generation, and it's estimated there are only 18,000 square miles of such sites in the U.S. For wind power to become truly cost-competitive with fossil fuels, more sites must become viable and new technology must advance to thrive, rather than struggle, with wind's variability.
To this end, ExRo Technologies has reinvented the generator to operate at peak efficiency (90 percent–plus) no matter how fast or slow the wind blows or how often its speed changes. This function of flexibility and scalability is achieved electronically with a controller, the "brain" of the nacelle, thereby eliminating the need for a fault-prone gearbox. The Variable Input Electrical Generator, or VIEG (pronounced "veej"), is able to produce energy from near-zero to very high wind by increasing its generation capacity or rightsizing itself to the available wind in real time. This improves the reliability of wind power from any site, especially sites that have been deemed not fit for wind generation because of their low wind speeds.
Are there obstacles to scaling up wind power to serve a larger national or global customer base?
The availability of land and integrating wind power with the larger grid system are the two obstacles to scaling up wind power. In the U.S., nearly every site deemed currently viable has been snatched up. Scaling up wind power means finding ways to generate wind power on land where wind is too low to be considered by developers as a lucrative investment. This means developing new technologies, such as ExRo's VIEG, that can produce energy even with near-zero wind. This will open up vast resources of land both rural and urban, as well as optimizing the output of current wind sites.
Land with less favorable wind conditions located closer to the point of energy consumption can be profitable with VIEG-equipped turbines. This eases transmission concerns associated with all renewable energy generation and reduces the hefty cost of building new infrastructure. Wind farms both onshore and offshore require new power lines that, in addition to expenses, often face opposition from local communities.
But perhaps the larger piece of the puzzle is getting wind energy online with a signal the grid wants and can use. Traditionally wind plant signals fluctuate based on the variability of the wind, which creates uneven voltage and signal frequencies. This results in wind energy generation being heavily undervalued. It's often sold to some utilities at even a 30 percent discount rate.
To compensate, wind turbine manufacturers employ sophisticated power electronics to "clean" the signal before sending it to the grid. This post-generator signal processing is expensive, not only due to costly equipment, but also due to the increased inefficiency of the electrical power output.
By matching the generator configuration to the available source energy, ExRo's VIEG can harmonize output voltage and system resistance with grid requirements. This means increased capacity and reliability offered to the grid by any given site, thus allowing for more renewable energy to be incorporated into the grid generation mix and significant economic gains for wind plant operators.
Can the existing energy infrastructure handle growth in wind power? Or does that, too, need further modification?
Wind electricity is rarely generated at the site where it will be used, so improvement to the current electrical grid is pivotal. To truly scale up wind energy, large amounts of power need to be moved over long distances, and often the windiest sites are also the most remote. Often project developers have to work with the utility company to run power lines out to the site. This prospect alone has discouraged some projects.
To improve this, the grid itself has to be updated with what's being called a high-voltage backbone spanning the country. A model for this can be found running from Indiana through Ohio to Virginia already operated by a company called American Electric Power.
Given the current economic crisis, can your industry get the necessary capital (from public or private sources) to adequately finance its growth?
Given all these technical obstacles, wind power in the U.S. still grew by a record 50 percent in 2008, according to the American Wind Energy Association. As financing has dried up in the wake of the banking sector's troubles, experts expect to see less new wind energy coming online in 2009. Currently, the wind industry is looking toward the Obama administration's stimulus bill and energy bill to provide greater financing incentives for investment. [Editor's note: This survey was submitted before the stimulus bill was signed into law.]
However, due to the manufacturing bottlenecks the wind sector faces, projects that have already been planned and paid for will likely go forward. In addition, wind projects tend to be planned over the course of three years, and this gives wind developers the opportunity to order VIEG generators for their wind plants and thus garner more wind energy out of their sites.
From a strategic standpoint, which is the bigger competitor for wind: incumbent coal, oil and gas technologies or other alternative energy technologies?
Coal and natural gas are the biggest competitors to wind energy. When it comes to power generation, cost is king. Until wind energy can be produced (and made available to consumers) for less than coal-generated power, it will continue to be a second choice for power purchasers. The harsh reality is that 30 percent capacity factors simply aren't high enough to drive the cost of alternate energy below the cost of coal, and squeezing out another percentage point through a slightly better gearbox or a mildly better shedding system simply isn't going to get the nation to the Department of Energy's goal of 20 percent wind capacity.
Is there a cost target that you and others in your industry are aiming to achieve in, say, five years?
The mandate for ExRo is "Cheaper than coal." Currently, coal generates more than 40 percent of all electricity (50 percent in the U.S.), according to the U.S. Energy Information Administration. This is because it's the cheapest form of energy, as low as 2 cents per kilowatt-hour (kWh). To meet grid parity, the industry has to bring its cost/kWh down from as high as 5 cents/kWh in some areas. Other places are seeing wind energy as low as 3.5 cents/kWh, and this number is expected to decline in the coming years with advanced turbine technology. Yet small, incremental improvements from a slightly better gearbox or new a coating for turbine blades won't do the trick.
Technologies that cope with the wind's variable and intermittent nature are needed to overcome the price battle with coal. With third-party testing that shows the potential for double-digit efficiency gains for turbines, the VIEG is poised to meet the challenge. Such improvements to efficiency will drastically reduce wind's cost/kWh and transform the choice to build a new wind farm from an altruistic one to an economic one.