Winter storm Uri, and the unprecedented cold temperatures it ushered in, knocked out around a third of Texas's electricity generating capacity. On Wednesday, February 17, 2021, almost 3 million Texas were without power, including a quarter of all homes in Dallas, and 1.4 million homes in the Houston metropolitan area.
This has resulted in the largest forced blackout in U.S. history, according to Time Magazine, and brought attention to Texas's unique approach to electricity grid management.
The North American power grid
The North American power grid is divided into what are called "interconnections", and in Europe are called "multiple wide area synchronous grids." Regardless of their name, they are a three-phase electric power grid that operates at a synchronized utility frequency. "Three-phase" refers to the alternating current generation, transmission, and distribution method that is used by electrical grids worldwide.
The two major grids are the Eastern Interconnection and the Western Interconnection, and there are three smaller grids, the Quebec Interconnection, the Alaska Interconnection, and the Texas Interconnection.
The Eastern Interconnection extends from Central Canada eastward to the Atlantic coast, excluding Quebec, south to Florida, and west to the foot of the Rocky Mountains. The Western Interconnection stretches from Western Canada south to Baja California in Mexico, east over the Rocky Mountains to the Great Plains.
Interconnections can be tied to one another via high-voltage direct current (DC) power transmission lines, or with variable-frequency transformers (VFTs). The Texas Interconnection is tied to the Eastern Interconnection with two DC ties.
On October 13, 2009, the Tres Amigas SuperStation was announced. It is designed to connect the Eastern, Western, and Texas Interconnections via three 5 GW superconductor links.
The Texas Interconnection
Texas ended up having its own power grid because during WWII, the war effort required large amounts of power to be available along Texas's Gulf Coast. Prior to the war, in 1935, President Franklin D. Roosevelt had signed the Federal Power Act, which allowed the federal government to regulate interstate power lines. Following the war, Texas wanted no part of any federal standards and regulations, and in 1970, Texas created its own Electric Reliability Council of Texas, or ERCOT.
ERCOT is a nonprofit with joint state and private governance. ERCOT doesn’t actually provide electricity to all of Texas, but it covers around 75 percent of the state's land area and approximately 90 percent of its residents. Areas not included within ERCOT are the cities of El Paso, Longview, Marshall, Texarkana, Beaumont, Port Arthur, and The Woodlands.
ERCOT has four DC connections to other grids. Two are in the northeastern part of the state and they allow two-way transmission of around 820 megawatts of power. Texas also has two DC connections to Mexico which are only capable of transmitting small amounts of electricity.
What went wrong in Texas?
Most homes and businesses in Texas are heated by either electricity or natural gas. Electrical power generators typically schedule maintenance and upgrades for the winter months, so when Uri arrived, some of them were offline.
While Texas leads the U.S. in the production of natural gas, that gas couldn't be used to provide electrical power and to heat homes in Texas because of the way natural gas is stored. It is stored in underground chambers, and to bring it to the surface, a pump is required. The cold temperatures knocked out the diesel engines that power these pumps. Also, natural gas pipelines used to transfer the gas froze.
Some Texas politicians were quick to point to renewable energy sources, such as wind turbines, as the source of the problem:
This is what happens when you force the grid to rely in part on wind as a power source. When weather conditions get bad as they did this week, intermittent renewable energy like wind isn’t there when you need it.https://t.co/glCm3K0xyp— Rep. Dan Crenshaw (@RepDanCrenshaw) February 16, 2021
But, that is not the case. Wind power accounts for less than 13 percent of the 30 to 35 gigawatts of total outages, as Dan Woodfin, a senior director at Texas's grid operator told The Daily Mail.
What finally brought about the blackout was that home users were competing with power generators for the limited natural gas supplies, and the home users won. The reason they won is when natural gas supplies are constrained, they go to homes.
Most surprising is that Texas also lost its nuclear energy and coal power generating capacity. Coal plants couldn't operate because the coal piles froze and became stuck to the ground. One of the two nuclear reactors located at the South Texas Nuclear Power Station had to be shut down when the cooling pumps for its reactor froze.
Slowly coming back
On Wednesday, February 17, ERCOT brought back on line around 7 Gigawatts of generating capacity, however, many homes still remain in the dark because ERCOT is shifting to rolling blackouts rather than the continuous shutdown.
This strategy presents still more problems because as soon as they receive power, many appliances, such as furnaces and refrigerators, will start operating at their maximum capacity, further draining electricity supplies.
Once this current crisis is past, Texas may have to take a new look at its power grid. The only question is whether those governing the state will do it.