August 23, 2011
A recent article in ClimateWire reported on the contributions of wind energy in meeting the peak electricity demands during the recent record-setting heat wave in Texas. A previous Energy Forward blog entry noted that “wind generation tends to be the most productive in the middle of the night, when demands for electricity are low, and produces little power on hot summer afternoons when the air conditioning loads are highest.” As it turns out, this reduction in output during midday heat may be true for the inland wind farms, but the coastal wind farms tend to produce more wind under these conditions, thereby offsetting the reduced output from inland turbines. According to the article in ClimateWire, while electricity from the concentration of wind farms in western Texas tends to drop off with the fading winds in the midday heat, “energy from newer wind units along the southern Texas coast has helped bail out the state as electricity demand set new records.” Kent Saathoff, vice president of grid operations and system planning for the Electric Reliability Council of Texas (ERCOT), observed that winds from the Gulf of Mexico pick up strength as the landmass heats up, matching the growing demand for electricity in the middle of the day.
As the penetration of wind power increases within a particular transmission region, this complementary diversity in energy production will prove to enhance the value of windpower. The aggregate capacity factor (i.e., the extent to which the wind generation can be relied upon to produce electricity when it is needed) is greater if the wind farms cover a large enough area with different climate characteristics, as a decline in production in one area may be offset by increased production in another, along with the weather patterns. A similar observation was made in the context of the Atlantic Wind Connection, the $5 billion transmission backbone for offshore wind in which Google is taking a substantial equity stake. The length of that transmission backbone, 350 miles, will result in reduced aggregate variability in wind output (once the backbone is built out with offshore wind turbines). As reported in Matthew Wald’s New York Times article from October 2010, Willett M. Kempton of the University of Delaware and John Wellinghoff, Chairman of the Federal Energy Regulatory Commission observed that “the backbone would offer another plus: reducing one of wind power’s big problems, variability of output.” According to the New York Times article, Mr. Kempton noted that “[a]long the U.S. Atlantic seaboard, we tend to have storm tracks that move along the coast and somewhat offshore.” Thus, “[i]f storm winds were blowing on Friday off Virginia, they might be off Delaware by Saturday and off New Jersey by Sunday, yet the long spine would ensure that the amount of energy coming ashore held roughly constant.”
The Texas experience provides another example of the advantages of diversity of geographic location when siting wind turbines. Given that the variability in wind energy production can be complementary across weather zones, the overall reliability of the wind resource is enhanced.