The Power of Information: Redefining U.S. Energy Infrastructure with a Modern Smart Grid
Hundreds of millions of people turn on their lights at night thanks to the electric power grid. Photo courtesy of NASA.
The U.S. electric power grid provides electricity to over three hundred million people every day. This electricity powers some of the most advanced technologies in the world but is surprisingly delivered through a mostly aging, outmoded and over-stressed network. In fact, 70 percent of transmission lines and transformers are more than 25 years old, while 60 percent of circuit breakers are 30 years old or more. Combine this with the fact that today’s grid was designed in the 50s and installed in the 60s and 70s, before the era of the microprocessor, and it becomes clear that a new system will be needed to handle future energy demands.
Today, the modern grid is driven by a desire for variable renewable power, greater consumer participation, greater reliability and power quality, and affordability. Instead of merely replacing current power distribution infrastructure with the same obsolete components, the U. S. Department of Energy (DOE) is introducing new technologies collectively comprising the Smart Grid that will greatly improve reliability, safety, resilience, security, economics, efficiency, and environmental responsibility. This new Smart Grid is redefining U.S. Energy infrastructure by introducing sensors and other hardware along with sophisticated software to continuously inform the system.
The American Recovery and Reinvestment Act of 2009 (Recovery Act) provided DOE with $4.5 billion to modernize the electric power grid. Part of this money is being used to fund Smart Grid demonstration projects (SGDPs), which are initiatives across the country that are testing and implementing Smart Grid technologies. These initiatives involve every aspect of the electric grid, from information portals and smart meters in the consumer’s home, through the transmission lines, and out into our nation’s power generation plants, including those powered by renewable energy. The National Energy Technology Laboratory manages all 32 of these SGDP projects, lending its energy expertise to help these important technologies succeed.
The Smart Grid and the U.S. Home
The Smart Grid will engage customers directly in their homes. Advanced metering infrastructure (AMI) technology will rely on two-way communication to solve current problems facing electricity providers, like how to reduce usage during peak times. Customers will actively participate in how they consume energy and what that energy will cost by changing the times that they perform energy-intensive activities. In Ohio, a service area comprising approximately 150 square miles of urban, suburban, and rural neighborhoods was selected to take part in an SGDP named gridSMART®, which provided 100,000 residential smart meters and 10,000 commercial and industrial smart meters.
These smart meters are one component of the AMI, which communicates information between customers’ homes and the utility companies. Customers who participated in gridSMART® chose between several different pricing programs, including options that offered a lower rate during off-peak hours. Overall, customers saw an average savings of 15 percent, and the utility company saw a decrease in peak-time usage. Furthermore, AMI removes the need for the utility company to travel to each home to read their meters, resulting in less CO2 emissions from vehicles.
Optimizing Transmission-Line Capacity with Dynamic Line Reading
The Smart Grid offers unprecedented opportunities for power companies to reduce peak loads and for customers to save money, but these successes can be impeded if the lines transmitting the electricity short out and fault or operate at less than optimum efficiency. The metal wire conductors inside power lines heat up as more electricity runs through them. Higher temperatures then cause the metal to expand, resulting in drooping power lines that can fault if they come into contact with vegetation or other objects. Once power lines fault, service can be interrupted to a large section of customers, so it is important to accurately define the current capacity of a transmission line.
Current static line ratings can only provide a seasonally dependent, conservative estimate of overhead transmission-line current capacity. In reality, variables such as air temperature, solar radiation, and wind speed and direction can greatly influence conductor temperature and therefore transmission line sag. However, dynamic line ratings (DLR) employ sensors on or near transmission lines to monitor these environmental variables as well as the current sag of the lines.
In White Plains, New York, the New York Power Authority (NYPA) worked with the Electric Power Research Institute to test whether increased wind generation could be correlated with increased transmission-line capacity. This correlation could demonstrate that transmission lines connected to wind farms could handle the peak loads generated with high winds. They expected to observe such a correlation because higher winds not only produce more wind energy but also have a cooling effect on transmission lines, allowing them to handle more electrical current. The study did establish a correlation, and this information also confirmed to NYPA that real-time transmission-line capacity was higher than what was estimated by static ratings, with up to 25 percent additional usable capacity actually available—capacity that could be revealed only by using DLR.
Energy Storage: Smoothing out Alternative Energy
Renewable sources, like wind and solar, provide unlimited supplies of clean energy, but they’re not a steady source of power. The U.S. grid operates at a consistent 60 Hz frequency that is maintained by adjusting power generation and loads, but the sun’s output varies throughout the day and the wind speed can change unpredictably, resulting in inconsistent power output.
The Public Service Company of New Mexico (PNM) began an SGDP that aimed to conform renewable energy inconsistency by using batteries to smooth fluctuations in their photovoltaic (PV) plant. These batteries released energy into the grid when solar energy waned and then recharged during times of increased solar activity when the batteries’ power was no longer needed. These “smoothing” batteries hold great promise for the efficient use of renewable energy, and companies are actively developing new generations of the technology.
The Future of Safe Energy
Communication will play a critical role in the success of the Smart Grid. Consumers will interact with utility companies through data exchanges, but any transmission of data includes a risk of interception by people or groups who would exploit this information. Just as cyber security is essential when planning a computer network, the Smart Grid will also need to be secure.
As part of an SGDP project, the Long Island Power Authority has developed defenses against cyber-attacks on AMI already in place. The same smart meters that provide essential two-way communication for customers and utilities have employed defenses such as frequency hopping cryptography—a method of data transmission that rapidly switches between many frequency channels. Further security measures are also being evaluated such as a computer program known as a “fuzzer.” This program attempts to identify security bugs by sending invalid messages to target devices. If these devices do not respond appropriately, then the system suspects that a bug is present. These added measures ensure that as the Smart Grid becomes more sophisticated, it will remain safe and secure.
Putting it all Together
All of these NETL-managed SGDPs have proven that the investment by the American people in grid modernization shows great promise for future returns of efficient energy delivery. While a nation-wide Smart Grid may take many more years to completely implement, those participating in SGDP projects are testing the concepts so they can be widely implemented to benefit the nation in the future. As more sections of the national electric grid are replaced with Smart Grid components, customers can expect affordable power, safer and more reliable service, less negative impact on the environment, and energy tailored to the customers’ usage needs—all due to the exchange of information.