Features - December 2015

Vehicles and Voltage: Regulating the U.S. Power Grid

With the flick of a switch, we can flood our homes with light on freezing winter nights. With a push of a button on a thermostat, we drive away the chill of snow and wind. Power—electricity—is what keeps up safe and warm when the weather outside is nothing but frightful.

Yet, very rarely do we stop and think about how that energy is supplied to our homes or how we influence the complex system that is America’s power grid.

Power lines transport electricity from power plants to our homes and businesses.
Power lines transport electricity from power plants to our homes and businesses.

A vast network of power plants, transformers, and high-voltage transmission lines—over 450,000 miles—creates a giant web across the country. Electric power is generated at power plants and then moved by transmission lines to substations. A local distribution system of smaller, lower-voltage transmission lines then moves power from substations to our homes and businesses. Split into three smaller grids, called interconnections, the United State’s energy infrastructure delivers electricity to nearly every part of the nation. The Eastern Interconnection operates in states east of the Rocky Mountains, The Western Interconnection covers the Pacific Ocean to the Rocky Mountain states, and the smallest—the Texas Interconnected system—covers most of Texas.

Due to their complexity, energy grids require maintenance. Grids must be both reliable and resilient—delivering electricity with few interruptions and equipped to deal with adverse events, like storms and power fluctuations. Frequency regulation is one key aspect of ensuring both the reliability and resiliency of our power grid.

Electricity lights up our country.
Electricity lights up our country.

Power grids must deal with oscillations in frequency of currents when electricity is delivered from power plant to end-user. In America, our power grid standard is 60 hertz. In order to regulate the frequency of the grid, systems must be in place for injecting power into or absorbing power from the electricity grid to closely match power generation with its consumption and stabilize its frequency at near the U.S. standard.

There are multiple methods through which frequency is regulated, but new, innovative methods are also being developed. The National Energy Technology Laboratory (NETL) has been managing a Smart Grid Demonstration Project with the Center for the Commercialization of Electric Technologies. The project set out to determine and demonstrate the efficacy of incorporating electric vehicles to help regulate the frequency on the power grid.

In the demonstration, a fleet of 11 plug-in electric delivery trucks from Frito Lay in Fort Worth, Texas were used to provide frequency regulation services to the Electric Reliability Council of Texas (ERCOT), the operator of most of the power grid in Texas. Under normal conditions, the electric delivery trucks would be drawing power from the grid to charge their electric batteries, a process known as Grid-to-Vehicle. However, if these trucks were to help regulate the system, the vehicles also had to be able to discharge power from their batteries back into the grid to even out power shortages—a process known as Vehicle-to-Grid.

The power system used by ERCOT relies significantly on energy produced from wind turbines. Although wind turbines produce clean energy, their power output is deeply dependent on weather conditions and is therefore highly variable. The variability means that the power grid must be closely monitored to maintain correct frequency, otherwise the spates and dearths of electricity cause mismatches between power generation and consumption.

Imagine a world where you would be paid for charging your electric vehicle. Grid technology like this could make that a reality.
Imagine a world where you would be paid for charging your electric vehicle. Grid technology like this could make that a reality.

The demonstration program used the Frito Lay delivery trucks (which delivered primarily at night and charged during the day, when power consumption is highest) to help regulate this erratic grid. The trucks provided frequency regulation services when notified by ERCOT or when the grid frequency deviated more than 0.09 hertz from 60 hertz. The trucks were able to provide at least 100 kilowatts of frequency services, a requirement for effective frequency regulation, and the demonstration proved successful. This project proved the feasibility of an aggregated fleet of electric vehicles being used to manage stability of the power grid.

Although work still must be done to incorporate this model into America’s energy infrastructure, or possibly expand the concept to a wider range of electric vehicles, the success of the project is just one example of the exciting opportunities for innovation in the way we modernize our power grid—ensuring that our holiday season is a little brighter and a little warmer.