Hydropower, Wind Power

Bottom Line: Wind & Hydropower Can Work Together

When a utility is initially introducing wind power in the mix, is it important that the utility — which is responsible for the transmission grid and the majority of all generation — control or experiment first before a private non-utility generator enters the market? Secondly, if given the option would you choose hydropower or wind for a 1,000 MW or more project? — Sue Kelland-Dyer, St. John’s NL Canada

Anyone who has stood outside and observed the wind pick up and then die down understands that this energy resource, while powerful and limitless, is also variable in nature. That’s why utilities — particularly those that have little experience with wind power — are sometimes reticent to incorporate it into their energy mix. But it is easy to forget that with or without wind, utilities are already expert at managing variability. Here’s why. The peaking and falling of electricity demand is something utilities have learned to deal with quite well. When a heat wave hits in August, power plants need to answer the peaking need in the afternoon and ramp up their output; facilities idle the rest of the year also may need to come online. Such events can be predicted to a certain extent, but the forecast of demand — and the weather — is hardly perfect. Further, a utility also must stand ready to deal with the sudden disconnection of any of the major components of the energy supply system. Now let’s return to the supply side of the equation, where wind energy and the rest of the energy sources reside. Keeping in mind the analogy concerning the variability of electricity demand, it is helpful to think of wind power as “negative demand” or “negative load.” That is, wind energy reduces the need for the rest of the system to provide power. Wind, then, is a positive addition to the overall energy picture on a given system. To continue the analogy of electricity demand, if a large consumer of electricity were added onto the system — let’s say some type of manufacturing facility that sucks up notable quantities of electricity from the grid — the utility would make the necessary adjustments, learning how the facility’s usage pattern affects the overall demand for power. If you think this is one of those analogies that make sense on paper but don’t apply in the real world of wires, think again. “This analogy is widely used by utility system operators addressing the introduction of wind power,” notes AWEA Deputy Policy Director Mike Jacobs. As for your second question, it’s important to explore the differences between wind energy and hydropower when considering this issue. The good news is some of these differences allow wind energy and hydropower to actually complement each other. In your region, you have a great deal of hydro already in place. Wind, incidentally, is a very good match to add into the energy source mix alongside hydro. That’s because when the wind is blowing, allowing for wind turbines to produce needed electricity, the water that isn’t needed to pass through the dam and produce electricity at that time can be held back or stored behind the dam so that it can be used at a later date. Thus, because less total water is passing through the dam as a result of wind power, the wind turbines in essence extend the hours in a year when that hydro facility can produce electricity. In short, existing dams can be used more efficiently with wind facilities working with them in tandem. No question, a 1,000-MW plant, no matter what the energy source, is a big facility. Historically hydropower plants have been capable of producing significantly more electricity than wind farms, and that remains somewhat true today; however, wind power facilities are getting increasingly bigger. Late last year, FPL Energy, LLC, completed its 735-MW Horse Hollow Wind Energy Center in Texas, making it the largest wind farm in the U.S.; FPL called it the largest in the world as well. The facility is comprised of 291 1.5-MW turbines and 130 2.3-MW turbines spread across 47,000 acres in Taylor and Nolan Counties. FPL Energy, incidentally, operates more than 1,600 MW of wind in Texas alone. Horse Hollow was producing electricity long before construction was completed late last year, which brings us to the next difference between the two energy sources. Another plus for wind as compared to hydro is the modular nature of wind farm project construction. A hydro facility cannot begin to produce energy until it is entirely built and ready. The planning and construction must be based on a decision of how large the plant will be, and no power will be produced until the project is finished. Naturally, as with all hefty financial deals, investing the massive amounts of capital needed for such a project brings with it inherent risks. Wind construction is the opposite. Most wind turbines are manufactured in sizes of 1-2 MW and can be installed and operated in a matter of months, so a risk of change in need or economics can be mitigated by installing the turbines incrementally — say, the first 100 MW or 200 MW — and adding more in the following years as needed. That way, operation and new power supply begins sooner, while the need for the full 1,000 MW can be revisited and revised if necessary. Also note that sizes of turbines are getting larger. Turbines with 2.5-MW capacities are being deployed with increased frequency today, allowing project developers to get more megawatts out of fewer turbines. At a recent AWEA event, Jim Lyons, chief engineer at GE Global Research Center, said that 5-MW turbines are not too many years away. Turbines with capacities of 5 MW, he said, can be deployed in such areas as the Great Plains, allowing for “gigawatt-scale [that is, 1,000 MW] land projects.” Having said all this, proponents of wind have always said that wind power is just one of several solutions to meeting electricity demand. A diverse energy portfolio reduces financial and other risks and creates greater energy security. Bottom line: wind and hydro can work well together, and so it doesn’t need to be an “either-or” decision.