Texans Shed Their Extra Load
For the past 48 hours, Texas has been slammed by a wave of winter weather that has Texans bundling up – and using more energy – to keep warm. This extreme weather has caused more than 50 power plants to go offline for periods of time ranging from minutes to hours. In response, the Electric Reliability Council of Texas (ERCOT) has ordered the Lower Colorado River Authority to increase power output from its dams. But, despite this extra capacity, ERCOT has been forced to start a series of rolling blackouts throughout central Texas in order to shed the load that these power plants are unable to meet.
The Electric Reliability Council of Texas manages the flow of electricity from power plants to customers through most of the state of Texas. They are responsible for ensuring that, when Texans want electricity, it is there. When ERCOT does its job well, we don’t notice them. When things go bad – due to technical difficulties (aka something breaks) or freak january snow storms – we become acutely aware of their role in the energy world and the lengths they go to in ensuring our electricity supply.
To keep the electrons flowing, ERCOT attacks the potential problems from two sides – supply and demand.
On the supply side, ERCOT makes sure to keep power plants waiting in the wings to come online quickly if they are needed. This reserve capacity is designed to be able to put electrons onto the grid within a few minutes of it being called upon by ERCOT. Frequently, these reserve plants are powered by natural gas, which Texas uses to supply about 50% of its electricity needs throughout the year.
On the demand side, ERCOT (or, at times, other companies working in the electric utility world) maintains the ability to quickly reduce demand in response to unexpected drops in supply. Load shedding is the process of reducing the amount of power that is demanded from the electric grid by turning off the demand of certain users. These abilities might take the form of agreements with large industrial facilities, where contracts guarantee benefits (money) for those who agree to be “turned off” in the case of an emergency. On a smaller scale, residential customers can agree to cycle appliances (for example, air conditioners) on and off to reduce their total electricity demand. One example of this can be found in Austin Energy’s Power Saver Program, which provides free programmable thermostats for residential customers who agree to flex their power use to reduce demand when it peaks in the summertime.
When reserve power and voluntary load shedding are not enough to balance electricity supply and demand, involuntary load shedding is a likely next step. Today, ERCOT imposed 8 hours of rolling blackouts throughout Central Texas, when unexpected difficulties in more than 50 power plants across the state led to an insufficient supply of electrons for Texans to use. While most blackouts were limited to short intervals (less than 45 minutes, according to Austin Energy and other utilities in the state), each blackout was experienced by an average 330,000 Texans.
Today’s rolling blackouts show the potential problems with maintaining the careful balance of supply and demand that is required in a system that functions without large-scale energy storage as a back-up. This load-following design (where power plants respond to customer demand, instead of vice versa) lacks some of the flexibility needed to maintain grid reliability in the face of unexpectedly harsh winter weather. And, today, this design left many Texans in the dark.
[photos from flickr and KETK NBC – obtained via Creative Commons]