Smart Transmission Shortfall Leaving Texas Green Energy in the Dark

by Vernon Trollinger

It looked like green energy saved all the bacon in Texas this summer. At least until Wednesday, September 6. At 7:25 pm, ERCOT’s generation reserves fell below 1,750 MW and it issued an Energy Emergency Alert 2.

Ironically, the emergency started when too much wind energy threatened to overload a transmission line sending power to Dallas. To save the line, ERCOT curtailed the wind farms supplying it because there just wasn’t enough transmission capacity for it all. Unfortunately, the move put the grid at risk during a period of high demand.

For the control room folks running the grid, it was a case of “Damned if you do; damned if you don’t.” But in the larger scheme of things, it points to future trouble. As PowerChoiceTexas.org rightly points out, electricity rates in Texas depend a lot on where you live. With the Lone Star State facing increasing population and electricity demand, the ERCOT grid needs all the power it can make to keep rates low.

But it won’t light up a night light if there’s no transmission lines to carry the power.

Wiring Renewables to ERCOT’s Grid

ERCOT faces multiple transmission problems. First, even with over 52,000 miles of high voltage transmission lines and substations there’s just not enough wired capacity to connect all the generation projects — both renewable and “dispatchable” — already in the interconnection queue. And there’s more on the way. The EIA predicts combined wind and solar generating capacity in Texas’s power market will double by 2035. Without adequate transmission, significant chunks of that power will be curtailed. Plus, the recent passage of Proposition 7 to give low-interest loans to build more natural gas generators could see those possible future plants curtailed as well.

New Transmission Costs Texas Consumers

Like most obstacles to Texas electricity, the primary problem is the upfront cost. For example, one of the biggest projects in ERCOT was the Competitive Renewable Energy Zones (CREZ) project. Begun in 2005, CREZ strung 2,400 miles of transmission lines to carry 18,500 megawatts of west Texas wind power to major load centers like Houston, Dallas-Fort Worth, Austin, and San Antonio. Completed in 2014, the project cost $7 billion dollars, nearly double the original estimated cost. Even so, CREZ cut wind curtailment by more than 90%. At the time, ERCOT estimated CREZ saved ratepayers $2 billion a year.

Now, most transmission projects are shorter. For example, the San Antonio South Reliability Project near San Antonio will build a new 50 mile line and upgrade another 20 miles of existing line. But it’s expensive and time consuming. For 70 miles of power line, this project is slated to cost $329.1 million and not be ready until 2027.

The US Department of Energy (DOE) estimates by 2035, ERCOT will need to increase its current transmission capacity by 140%. In Texas, transmission costs are passed to consumers in their electricity bills. As TexasElectricityRatings.com reports, the average Texas home in the summer uses more than 1,000 kWh. With summer peak demand increasing by more than 4% each year, construction costs could substantially increase what consumers pay each month, especially in the summer. Isn’t there a smarter, more efficient way?

It turns out there is. And it’s been around for over a decade.

A Smarter Way to Transmit Texas Green Energy

A transmission line’s enemy is heat. Too much electricity going through them heats them up. More heat cuts the amount of power they can conduct…which heats them up more. Hot lines can sag into tree tops or break and cause black outs. To cope, ERCOT adopted a fairly flexible system called Ambient-Adjusted Ratings (AARs). The system uses ambient temperature to set how much power transmission lines can carry. Each transmission owner provides ERCOT with temperature tables rated in 5 degree increments for its lines. ERCOT uses weather forecasts to automatically update line transmission capacity for the day.

While newer Grid Enhancing Technologies (GETs) cannot totally replace the need for additional infrastructure, they can make what’s in place work much more efficiently. Plus, GETs can be deployed much faster and often at less cost than building new transmission projects. One highly promising GETs is Dynamic Line Rating (DLR). DLR systems continuously monitor and adjust the capacity of transmission lines based on real-time thermal conditions sent from the line itself.

This is not bleeding edge stuff. In 2014, Dallas-based Oncor demonstrated that DLRs improved its grid efficiency and reliability by improving line capacity. By just increasing transmission capacity by 5% on the study’s target lines, Oncor found it could relieve congestion by up to 60%. Furthermore, a 10% increase in capacity relieved all congestion.

When it comes to the whole Texas grid, the benefits get even bigger. A 2022 MIT study ran simulations of the ERCOT grid and found that DLRs could save $776 million in annual congestion rents. Notably, the research showed DLRs could cut curtailment of wind and solar resources by about 1,000 MW per hour.

That means smarter transmission might have avoided the September 6 emergency all together.

Rewire Texas for Green Energy Savings

Maybe green energy curtailments like the September 6 event is one way for ERCOT to keep squeaking by catastrophe. But now with both the state’s population demanding more electricity each year, ERCOT knows it needs to invest in a smarter way to transmit its growing green energy supply to the places that need power. Twenty years ago, Texas untangled its regulated energy market to bring customer choice, lower prices, and innovative renewable energy to its grid. Now it’s time for Texas to rewire itself to increase reliability and cut customer prices. By implementing grid enhancing technologies like DLRs, Texas can show it still has the talent, the know-how, and the will to supply cheap, reliable electricity to all consumers without help from outside the ERCOT grid.