America’s electric power grid is truly one of the wonders of the modern world. A combination of millions of miles of cables and wires, transformers, generating plants and, of course, hundreds of millions of customers who use the constantly available energy, the grid is the world’s largest musical instrument, tuned precisely to within a fraction of a single note, 60 Hertz.
Every second of every day independent system operators, the folks who manage the grid’s various regions, perform modern society’s greatest balancing act by matching the fluctuating load created by each of us as we make toast, turn on lights, or adjust the air conditioning with the exact same generating capacity from the variety of energy sources available to them.
In today’s world, coal- and natural gas-fired plants serve the majority of our national electrical demand. Large-scale hydroelectric turbines can, at any given time, provide for about 7 percent of total demand. Hydroelectric power is typically the energy used by the system operators to rapidly balance supply against demand, since it is available immediately, whereas steam plants take hours to reach operating temperature. Hydroelectric plants normally run at whatever levels match the inflows to their reservoirs so the lakes don’t drain away, but when large amounts of power are needed the operators can ramp up production to much larger levels to match grid loads for short periods of time almost instantly.
These days we read and hear more and more about the exponential increases in renewable energy, particularly large wind farms such as those sprouting up on Colorado’s front range and eastern plains. Colorado’s Amendment 37 requires the state’s largest utility companies to produce 10 percent of their energy from renewable sources by 2015. A subsequent legislative action doubled that to 20 percent by 2020.
The Denver Post reported recently that Vestas Wind Systems has announced plans to spend $250 million to build the world’s largest wind turbine tower factory in Colorado. This year, Vestas opened its first American blade manufacturing facility in Windsor, which is between Greeley and Fort Collins. The $65 million, 350,000 square-foot facility eventually will produce more than 500, 40-meter wind turbines a year, according to company officials. Originally, the company planned to employ 450 people at full capacity. But an expansion announced late in 2007 added another 250 jobs.
This is all great news, right? Not if you are an independent grid system operator, and not if you’re expecting all of this large scale wind power to help reduce global warming carbon emissions.
Wind power is by nature a notoriously intermittent source of power. Wind simply doesn’t blow steadily all of the time. Therefore, the power output of all large scale wind farms goes up and down dramatically throughout the day, regardless of the demand for power on the grid.
Today, the grid’s operators constantly track wind power’s input and balance its fluctuations using reserve power from already-operating hydro, coal and gas generators.
Since the total power wind contributes to the national capacity is still below that which hydro can deliver, this “spinning stock” routinely makes up for the increases and decreases the nation’s wind systems provide. Most of the time.
Recently in Texas, which has more wind turbine energy sources than anyone else, system operators were forced to declare a power emergency when the wind suddenly just stopped blowing, cutting more than 3 billion watts from the grid.
Large scale industrial equipment was shut down by grid operators to lessen the load on the fossil-fueled generators, which were beginning to slow down under the increased load.
When these huge generators slow down, the single note the system is tuned to operate on, 60 Hertz, drops in frequency, increasing heat in all portions of the tuned system.
If the frequency changes too much, other automatic protection systems engage to shed more load, creating widespread “rolling blackouts” to protect the system’s backbone. This was narrowly avoided last month in Texas.
But what happens when wind power reaches its mandated percentage of 20 percent of supply?
There aren’t any more large scale hydroelectric dam sites in this country where additional spinning stock could be made available to match the much larger fluctuations in the wind power supply.
As wind power approaches Colorado’s mandated levels, utilities will have few options. More rolling blackouts as the wind changes, or building more gas and coal fired generators that will have to burn fuel all the time in order to be hot and ready to take on the loads when the wind changes direction, slows down or stops. Massive storage of wind power simply isn’t available with today’s battery technology, and proposed alternative storage systems such as huge compressed air reservoirs that could spin turbines are still not available, or take more far more energy to compress and fill than they produce.
We’ve legislated large-scale renewable power, but the laws of physics and the laws of Colorado may not share the same basis. Large scale wind farms cannot replace a single coal, gas or nuclear facility. In fact, if the grid is to continue serving the massive constant demand it sees today, more wind will require more coal and gas plants to be built.
As large-scale wind power becomes a bigger percentage of the grid’s supply, individuals who require uninterrupted power may need more local sources of reliable energy, such as on-site generators or battery-backed solar systems, to meet their needs when the grid is being balanced.
Without energy diversity, the more renewable power we mandate, the more unreliable the grid will become. The laws of physics simply can’t be amended.
Bill Sepmeier is chief technical officer and Matthew Charles is marketing director for Grid Feeders in Eagle-Vail. To learn more, go to www.gridfeeders.com.
21 May 2008
URL to article: https://www.wind-watch.org/news/2008/05/22/wind-power-could-complicate-electricity-management/