Transmission lines are chasing the rapid growth of wind generation across the nation, but it may be a while before they catch up.
Billions of dollars in transmission lines will have to be built before the nation's wind resources, which are concentrated in the center of the country, can be fully exploited by large population centers to the east and west.
In the meantime, regulators, generators and utilities have to deal with transmission congestion and wind curtailments, the temporary shutting down of generation to maintain system balance and reliability. Those hurdles increase the costs of renewable energy and decrease its environmental benefits.
Steve Gaw, a transmission policy specialist with The Wind Coalition, a trade group in Austin, Texas, said investment in transmission across the nation has been lagging for several decades. That changed only in the last five years as wind generation began coming online in a major way.
A combination of favorable tax treatment for wind generation and state mandates for renewable energy pushed the nation's wind capacity to more than 60,000 megawatts in 2012, according to the federal Energy Department. That's enough to power 15 million homes.
Oklahoma ranked sixth among states for wind capacity last year, up from eighth place in 2011. New power purchase agreements for wind generation in the state are increasingly being signed with out-of-state utilities. Meanwhile, the Southwest Power Pool, a regional transmission organization covering 15 million people in Oklahoma and parts of eight other states, has more almost 27,000 megawatts of wind generation in service or ready to come online in the next few years.
“The best wind resources tend to be at the western side of the (SPP) footprint,” Gaw said. “Those were areas that generally didn't have much (customer) load, so the transmission wasn't as developed. That has been changing in a significant way.”
Developers can build wind farms much faster than new transmission. The typical wind farm needs thousands of acres, but the parcels of land are easier to combine for a wind project than the rights of way for transmission lines.
“It may be economically and environmentally efficient to build excess capacity into certain transmission projects given the scarcity of rights of way and the challenges of developing location-constrained renewable energy resources without existing transmission,” the Washington-based Bipartisan Policy Center said earlier this year in a report on grid modernization.
Some grid projects are bypassing regional transmission organizations altogether. Clean Line Energy Partners LLC has five high-voltage, direct-current transmission lines planned for renewable energy in various parts of the country, including the Plains and Eastern Clean Line. It will take power from planned wind farms in the Oklahoma and Texas panhandles and western Kansas and transmit it directly to the western Tennessee for utilities in the southeastern United States. The company also may deliver electricity to customers in Arkansas using an “off-ramp” from the line.
Clean Line said in August a survey of wind companies showed they could develop up to 16,000 megawatts of capacity for the Plains and Eastern Clean Line. That represents more than four times the 3,500 megawatts planned for the 700-mile transmission line, which is still in the environmental impact and siting stage. The $2 billion line could be operational by 2017 or 2018, the company said.
To help the siting of its projects, Clean Line has been granted public utility status in several states, including Oklahoma. While the company prefers to work with affected landowners on easements, it can use a utility's eminent domain power as a last resort. As a backstop, it is pursuing federal eminent domain under a 2005 law to promote transmission projects.
Policymakers must balance the need for new transmission projects and the rights of landowners.
“People are generally receptive to the development of wind projects, but are sometimes less receptive when construction begins nearing their property,” said Jay Albert, Oklahoma's deputy secretary of energy. “But if you want to bring additional wind generation capacity online, transmission is a key factor, and it is something we have to work to accommodate.”
SPP's integrated transmission planning process looks at short-term needs and projections for 10 years and 20 years into the future. To maintain system reliability, companies proposing new generation — from any fuel source — have to get in line and pay for studies to see how the generation would affect electrical infrastructure in the region. In many cases, SPP requires additional investment in substations, transformers or other equipment.
“Some of that (transmission) construction is done in anticipation of these projects, and some of the generation is already up and running before those transmission projects are completed,” Gaw said. “There may be some exposure to curtailments that hopefully the completion of these transmission projects will help rectify.”
Gaw said recent wind curtailments in the SPP were related to repairs or upgrades of several transmission lines in parts of the region, including western Kansas in the spring. Utilities typically make major repairs or try to complete upgrades in the spring or fall. The SPP has a working group studying maintenance schedules and how they can affect transmission from wind generators, he said.
The variable nature of wind energy remains its biggest obstacle to effective integration into the grid, according to a November report by the North American Electric Reliability Corp., which is in charge of reliability in the United States, Canada and parts of Mexico. New wind forecasting tools and technology will help that integration.
“Unpredictability remains the largest obstacle in effectively integrating wind energy into SPP's generating mix,” the report said.
“As wind speeds change, utilities must instantaneously switch to and from other generating resources to compensate for this variability. Increasing the capability to forecast wind's time, location and speed will significantly enhance operators' ability to reliably manage the grid.”