by Larry Sinesio, Vice President, WindLogics Inc.
Today's electric utilities are seeing explosive growth in wind energy as a means to meeting evolving renewable portfolio standards as well as increasing demand for power. With a focus on reliability and customer service, this growth absolutely requires smart decisions about siting projects, integrating wind plants into the power system, purchasing wind energy, and developing wind energy projects.
Perspective on wind portfolios
Successful addition of wind energy into a utility's portfolio involves the necessary shift from thinking in terms of resource capacity of a wind plant to considering wind energy "as delivered," and to using forecasting as a critical component of successful operations.
This shift is supported by several recent studies demonstrating the impacts of wind energy on specific power systems (see www.uwig.org). These studies consistently show that the variability of wind energy does have some operating cost, but this cost is modest and manageable even with growing amounts of wind energy. They further show that scheduling wind power delivery with various forecasting methods, even if not perfect due to the challenges of weather and wind forecasting, adds considerable value for both operations and future system planning.
With tools and information from these studies, utilities can put plans in place to assure reliable operation of electric systems, providing a foundation for power purchase arrangements focused on balanced operations and serving customer loads. The success of individual projects is now the focus for many utilities.
Wind energy project siting criteria
Thorough site analysis is essential for successful wind energy projects. Projects must have access to adequate transmission or coincide with evolving transmission corridors. The best sites have no significant environmental hurdles to overcome, such as migratory bird or bat flyways, or conflicts over protected lands. Given the large size of modern wind turbines, road access must be adequate for delivery and construction, and site geology must be suitable for turbine foundations. The remaining critical aspect of this site analysis is wind resource variability.
Like all site characteristics, wind variability can make or break a wind energy project, but many would agree it outranks all others in its complexity and its implications on the project's financial performance. Power varies with the cube of wind speed, so relatively small differences in wind speed can have significant impact on both the instantaneous power output and the long-term success of the wind project.
Components of wind variability
Wind varies over the course of every 24-hour day. It varies over seasons as those of us in the northern states can feel, facing cold blustery winters. It varies over years and even decades, as climatologists can demonstrate impacts of major forces like El Nino. Wind varies by region and even within a given wind plant site. Wind speed changes with height above ground, adding to its complexity since the wind pattern at turbine hub height is often very different from what we experience or measure at ground level.
Because of its complex nature, this variability often accounts for most of the risk in wind farm development. However, ongoing wind resource research and development continues to improve our understanding of wind variability, improving its predictability, thereby reducing its contribution to project risk.
Variability is a characteristic of the "fuel" of a wind plant. Like any fuel source, understanding it is critical to plant performance and financial return. Predicting and managing this "free fuel availability" can make a marginal project profitable and a good project a huge success.
Strategies for wind plant development
Smart wind plant developers have improved their understanding of wind resources through three-dimensional modeling of wind regimes, including investing in meteorological expertise to help quantify results. They are using creative placement of data collection and monitoring devices, coupled with innovative correlations using very long-term (30+ years) datasets, to understand the long-term characteristics of their specific site even prior to the period of on-site observation.
Successful project developers have made a science of planning wind plant development. They use all the available tools and data for prospecting new opportunities (not all the good sites are taken!). We see them apply both traditional and innovative techniques in analyzing the wind resource, building a deep understanding of the entire project space by integrating point measurements (from on-site meteorological measurement towers) with the three-dimensional weather and wind patterns (from regional weather data sets) using physics-based simulation models. If done properly, such methods can provide a detailed, long-term understanding of the entire wind project. It's almost like having thirty years of operating history before the wind plant is even constructed!
A complete, accurate, three-dimensional picture of the wind regime over time offers huge advantages over traditional point data alone. This type of analysis provides wind speed and direction at any point on the site, and extends to air density and even wind shear. This means that, as micro-siting tools are applied to the site, a much more effective turbine layout can be achieved, maximizing the potential energy of the project.
These methodologies let developers separate wind variability from overall project risks, such as turbine availability. With this distinction, they can further clarify the energy available in the wind and then plan for and measure plant performance.
Outlook for successful wind project development
As wind plants continue to be built, developers will seek the best sites. Investors will want the best returns and accurate predictions. Utilities and other power purchasers will want accurate forecasts. All of these requirements will be effectively managed through the careful acquisition and analysis of site-specific data, and thorough site analysis.
Utilities face weather variability daily in supplying reliable power to their customers. They have learned the value of modeling, of accurate data, and of effective data management as a key business tools. They are uniquely positioned to take a leadership role to make sure that we develop smart wind energy, and that wind continues to be a fuel for growth.