Weather has a major effect on the productivity of wind turbines. Both the Polar Vortex and El Niño have reduced the output of wind turbines in the Midwest. During the polar vortex, wind turbines automatically shut off in the extreme cold because the low temperatures take a toll on various parts of a turbine, from electrical cabinets to the gearbox, the generator, lubricants and steel components, which can become brittle if the temperature drops low enough. Coal and natural gas plants had to ramp up production to meet the shortfall and keep the lights on. Also affecting the productivity of wind turbines is El Niño that brought calm winds to the Midwest, reducing wind output by 14 percent despite having added new turbines to the region. American electricity consumers, who expect their electricity to be available at the touch of a switch, should be very cautious about policies to mandate 100-percent renewable energy sources that are dependent on natural weather events.
Polar Vortex
In the Upper Midwest, three straight days of subzero temperatures occurred beginning January 29 when about half of the region’s electricity was coming from wind farms. Wind energy across the Midcontinent Independent System Operator’s northern region from Minnesota to Iowa peaked that morning at 11,445 megawatts. At the time, it was minus 8 degrees Fahrenheit.
The electricity from wind steadily tailed off during the next day and a half. By the evening of January 30, there was less than 550 megawatts on the north grid of the Midcontinent Independent System Operator, supplying just 2.5 percent of the region’s power. The temperature had fallen to minus 21 degrees Fahrenheit.
Wind generation in the Midcontinent Independent System Operator’s north region fell faster than anticipated during the polar vortex as turbines automatically shut down as temperatures fell below minus 20 degrees Fahrenheit, as the graph below shows.
The Energy Information Administration analyzed the generating technologies used during the polar vortex period, finding that, on January 30, wind accounted for an average of 5 percent, coal supplied about 41 percent, natural gas supplied about 30 percent, and nuclear supplied about 12 to 15 percent of the system operator’s load.
During the polar vortex, wind turbines shut off when temperatures dipped below minus 20 degrees Fahrenheit. There has been little focus on developing wind turbines to operate below minus 20 degrees Fahrenheit because at these temperatures, there is not much wind blowing. The economics of producing wind energy in such extreme conditions would not justify the additional cost, according to wind experts.
Some might argue that such temperatures are rare, and therefore these circumstances occur quite infrequently. However, when temperatures do reach that low, electricity is desperately needed, and therefore, there must be backup capacity available. As more and more wind is added to the system, it also requires correspondingly large amounts of backup. Such backup would be expected to run intermittently and therefore be extremely expensive, driving up overall costs to the system, which would be required to bear the costs to ensure health and safety for Americans.
El Niño
Calm winds due to El Niño effects are also hurting U.S. wind power production. Despite being relativity weak, the El Niño that formed in the equatorial Pacific Ocean tempered the gusts that typically occur through the U.S. wind belt, which typically cause the wind turbines to spin. In fact, the last 20 El Niño occurences have calmed winds across Minnesota, Wisconsin and beyond. In the fourth quarter of 2018, wind turbines in the upper Midwest produced far less power despite additional new turbines being installed in the region. Wind production fell to an average of about 6,700 megawatt hours, down from 7,800 megawatt hours in the fourth quarter of 2017, according to the Midcontinent Independent System Operator. The Southwest Power Pool, which stretches from Oklahoma to the Dakotas, also saw output from wind turbines decline in the fourth quarter to an average of about 8,100 megawatt hours, down from 8,200 megawatt hours a year earlier, according to the grid operator.
Advocates of 100-Percent Renewable Energy
Minnesota is among the states where clean energy advocates are pushing a bill to establish an 80 percent renewable energy standard by 2035 with a goal of 100 percent renewable energy by midcentury. There are currently 163 wind projects in the queue for the Midcontinent Independent System Operator, representing more than 31,000 megawatts of new renewable capacity. However, at the low capacity factors for wind and solar power, the amount of energy produced from this capacity is far less than from the same amount of coal, natural gas, or nuclear capacity.
Otter Tail, for example, is among the Upper Midwest utilities adding more wind to its portfolio—a 150-megawatt wind farm to be completed next year that will help replace a Minnesota coal plant. The wind project will be complemented by a 248-megawatt gas peaking plant being constructed in South Dakota. The wind is expected to provide energy while the gas turbine is expected to provide the needed capacity—the combination is regarded as the “new baseload.”
Researchers looked at the issue of how much storage (battery power, pumped hydroelectric power, etc.) would be needed to back up a 100-percent renewable system under polar vortex conditions. During the January 27 to February 2 polar vortex, the researchers evaluated a test case of 50 percent wind, 50 percent solar finding gaps of up to 18 hours in which renewable sources were not producing enough electricity to meet the high demand. The analysis found that storage would need to be increased from about 11 gigawatts today to 277.9 gigawatts in the regions that include New England, New York, the Mid-Atlantic, the Midwest, and parts of the South. Wood Mackenzie’s current forecast for energy storage nationwide in 2040 is only about half that figure. Further, battery technology of the magnitude needed to supply utility size areas is extremely expensive.
Consumers need to be aware of the pitfalls of a 100-percent renewable energy mandate. Last fall, the Midcontinent Independent System Operator published a renewable integration impact assessment indicating that more than 40 percent renewable penetration will be increasingly challenging and could require additional transmission.
Conclusion
The polar vortex and other weather events show that consumers should be cautious about pursuing a 100-percent renewable system if they expect electricity to be available at the turn of a light switch 24/7. This is especially true during cold spells, which are a normal occurrence in the Midwest. Weather conditions of this nature reduce winds, which force the system to rely on more traditional forms of generation. The new base load concept of “wind for energy/natural gas for capacity” may not provide the robust system that Americans have come to expect. One of the worst things for people to worry about during life threatening cold periods is the loss of electricity to run the fans for their furnaces, to keep the lights on, and to provide power for pumping water necessary for life.
