Growing transmission costs for wind-generated electricity have prompted Xcel Energy to seek approval for rate hikes to smaller utilities using Xcel’s transmission lines to reach their consumers:
Xcel wants the utilities to pay for its costs associated with having supplies of reserve power ready to go in case the wind suddenly dies, said Terri Eaton, Xcel’s director of federal regulatory and compliance efforts.
Currently, those costs are paid by Xcel’s business and residential customers, Eaton said.
If the transmission lines customers can supply their own back-up power supplies, they wouldn’t be charged under the proposed rates, she said.
Readily available, back-up power supplies are critical to keep the transmission grid in balance and avoid blackouts that can occur when a big source of power suddenly disappears, Eaton said.
Xcel’s hikes would hit rural cooperatives and other utilities should the Federal Energy Regulatory Commission approve the rate hike at the beginning of 2015.
But what, exactly, does Eaton mean when she refers to “reserve power ready to go in case the wind suddenly dies”?
“We’ve seen some dramatic wind fall-offs in really short periods of time,” Eaton said.
Xcel has already experienced such falls offs, when “several hundreds of megawatts of wind” drops dramatically — and swiftly — due to changes in the wind, she said.
“Sometimes the wind is just howling, and an hour later the wind has calmed — and it’s in those circumstances that we need to have reserves available to pick up the load,” Eaton said.
In such cases, backup power supplies typically come from natural gas-fueled power plants, she said.
The tariff proposed by Xcel would help cover the costs when the wind “suddenly dies.”
The intermittency of wind has been widely discussed, and no amount of forecasting or improved efficiency will spin a wind turbine’s blades if the wind isn’t blowing.
In 2012, a study examined wind generation in Illinois at the height of a summer heat wave, when energy demands rise to yearly highs. The author found that just 5 percent of installed wind capacity was available during that outbreak of record temperatures, and at times, “virtually nonexistent.”
Earlier this year, wind energy proponents touted the example provided in Texas–wind had saved the day. But a closer examination of the figures from the Electric Reliability Council of Texas (ERCOT) demonstrated that contrary to claims that wind had bailed out conventional sources of electricity by ensuring grid reliability, wind had actually fallen so substantially that Texas turned to other sources to meet the extra 1,000 megawatts of demand on January 6. Both scheduled and unscheduled plant closure elsewhere had left Texas with a gap during a record cold snap, a gap that wind was unable to fill.
As the Institute for Energy Research wrote in January, only 3.2 percent of the energy needs of the Texas grid operated by ERCOT came from wind, while 83 percent of Texas wind turbines “were unavailable during peak demand.”
ERCOT itself continues to rate its “wind power at 8.7 percent of its installed capacity” for 2014 during the periods of highest demands, which typically occur in mid-to-late summer. For nearly 12,000 megawatts of installed wind capacity, only 990 megawatts are considered reliable for forecasts computed by ERCOT for 2014. That’s like having the equivalent of 12 1,000 megawatt power plants built and only 1 online when summer energy demand spikes.
As a percentage, ERCOT figures wind to provide just 1.3 percent of the total amount of energy it needs this summer, rising to 2.2 percent by 2017 according to its own projections.
As for Colorado, under Senate Bill 252, rural cooperatives must reach 20 percent renewable energy by 2020.
Tri-State Generation and Transmission Association spokesman Lee Boughey acknowledged the rising costs of integrating ever-greater amounts of intermittent energy supplies like wind.
“As more intermittent resources are added in the region, we understand the need to address the higher costs of integrating and balancing power,” Boughey told the Denver Business Journal.
Those costs were highlighted in a March post that examined the integration of wind and other intermittent energy sources to the reliability of the grid operated by Public Service and regulated by the Public Utilities Commission (PUC), under the state’s preferred energy mandate:
The concern over infrastructure costs and the cost to ratepayers, as well as the challenge of incorporating ever-larger amounts of intermittent generation sources like solar and wind, is not a new topic at the PUC.
In June 2012 comments by PUC staff engineer Inez Dominguez indicated that off-peak load and wind generation in particular was “alarming.”
The integration of intermittent sources like wind would overwhelm the system, either with higher costs or decreased reliability. Bringing in wind and curtailing conventional, coal-fired generation during off-peak periods would result “in an economic penalty to the Public Service customers because more expensive wind generation would be supplying their load.”
Cutting off the wind, however, would also penalize ratepayers, as the “take or pay” agreements give wind first priority.
But the Public Service engineer also highlighted reliability concerns. “In its simplest terms as it concerns the customers, reliability deals with keeping the lights on. This reliability issue may occur when the wind suddenly stops blowing and a significant amount of wind generation is lost to the balancing authority,” Dominguez said.
“When this event happens, the balancing authority needs to replace the lost generation quickly enough to keep from tripping off the load. This means that the generation in reserve to cover such an event has to be quick enough in its response to cover the lost generation,” Dominguez continued.
For Colorado ratepayers, this backup generation comes from “gas fired combustion turbine generation reserves” that displace “more economic base load coal fired generation,” only adding to the cost, and “complexity” of the load balancing requirements.
According to Dominguez, these examples suggested a “flag that Public Service may have too much wind generation.”