PROBLEM: Can a modern electrical grid change
As innovation has transformed much of the global economy, America's electric power grid has remained based upon technologies that have been virtually unchanged for decades. In parallel with an increasing public awareness of global warming and the need for sustainable supplies of energy, the potential benefits of a robust, intelligent, interactive grid have become a centerpiece of policy discussions and an emerging research focus for the Department of Energy.
Advocates of grid modernization point to the need to accommodate diverse power generation sources, ensure more efficient and more reliable service, and provide consumers with the information necessary to manage household energy consumption.
Tom King, director of ORNL's Energy Efficiency and Electricity Technologies Program, has spent years studying both the potential benefits of transforming the nation's power grid and the challenges that will have to be overcome prior to meeting the energy demands of the coming decades. Echoing his ORNL colleague David Greene (see "Both Directions at Once," page 4), King summarizes America's challenges into two distinct categories: energy security and the impact of energy options on climate change. "Solutions to both of these challenges will place a burden on an electric infrastructure that is showing signs of stress," King says.
A Convergence of Issues
In the area of energy security, consensus exists about America's need to reduce sharply current levels of imported oil. "One nearest-term option may be the growing convergence of the electric delivery and transportation systems," King says, "The growing use of hybrid electric vehicles will combine, over the next decade, with the introduction of plug-in electric vehicles. Depending upon when and how fast these vehicles charge, their collective impact on the grid could be significant."
The second challenge, and one related to energy security, is how to generate adequate energy while simultaneously decreasing the negative impact of energy production on the environment. King believes that electrification of the transportation system could meet roughly one-half of the CO2 reduction goals for transportation. Such a dramatic increase in electric vehicles, however, would result in a corresponding increase in the demand on power plants to charge the vehicles' batteries. "Much of this demand is likely to be met by a greater penetration of renewables into the energy market to address the environmental concerns," says King. Although a good thing, these variable and intermittent resources can pose problems for the grid. Utilities will need to understand the potential impacts of these new energy sources on the electric delivery system before making long-term investments."
For example, when we look at energy security and climate challenges, each technology pathway has major impacts on the grid. "Many advocate a reduction in the use of coal," says King, "but such a decision must come with a clear understanding of other energy alternatives. Increasing our use of renewable energy sources is a desirable option, but we must be realistic in projecting the ability of renewable sources to meet future energy demand."
One as yet unresolved issue related to renewable energy sources is the effect of power inverters on the grid. Inverters are used to convert the electricity generated from solar panels, for example, into power that can be transmitted across the grid. Wind and solar energy farms require the intensive use of power inverters. Experience has shown that, when large numbers of inverters are on the distribution system, they can interact in ways that can create stability challenges to the grid.
"We have to understand what those consequences could be," King says. "Safety and reliability require that a plan to generate significant amounts of energy from renewable technology must ensure that all of the system's components are compatible before deployment. The technology pathways needed to address these problems will demand a robust electrical infrastructure."
Over the past two or three decades, a general uncertaintly about the direction of regulatory policy led to a lack of investment in new grid technologies. King emphasizes that closing this technology gap means more than just building more transmission towers. It also means making the grid "smarter."
By King's definition, a smart grid combines a two-way communication infrastructure with a power delivery system that can handle a range of new generation technologies, such as renewables, monitoring devices or fault current limiters. The smart grid would also enable customers to be more responsive in energy management.
"A smart grid is much more than placing a new meter on the side of a home in hopes of reducing demand," King says. "The goal is to enable more customers to understand how they consume energy and to respond to price signals in a way that reduces peak consumption."
"Many consumers have little appreciation for how much it costs if their kids leave the lights on," says King, "or for the financial impact of running the refrigerator or setting the thermostat in the summer at 72°F instead of 76°F. Currently there is no easy way for the American consumer to understand the relationship of use and cost of energy."
"Over the next five years," King says, "the market will make available to consumers a variety of in-home monitoring devices that will indicate in real time how much electricity is being used, along with the precise cost. In other words, turning off a light will reveal the immediate savings. Only a real-time monitoring system that is visible to the consumer will provide the motivation needed to alter behavior to the extent required to produce a significant reduction in energy consumption."
At present, most regions of the United States have fixed-rate pricing for electricity, meaning the cost is the same regardless of when the power is used. King foresees an accelerating trend toward time-of-use, or real-time, pricing to provide a strong financial incentive for consumers to move some of their power usage, like washing clothes or dishes, to off-peak hours. Time-of-use pricing would help utilities level daily demand on the grid and greatly reduce stress on the system during peak heating and cooling hours in the summer and winter. Equally important is the fact that utilities would be under less pressure to build new power plants to accommodate peak periods of demand.
King believes that development of a capacity for the grid to store power, perhaps by batteries positioned at substations, could be an additional way of reducing stress on the system, both at the bulk transmission level and at the distribution level. "As America moves toward increased market penetration of renewables," says King, "the ability to integrate technologies like wind or solar with storage devices would be transformative. Such concepts are high risk, but they are also high reward and are likely to present a variety of research opportunities for the laboratory in the near future."
"The goal of providing energy security in an environmentally benign way is among the biggest challenges facing humanity," King says. "Energy will continue to be a critical component of almost everything we do that sustains our quality of life. Meeting CO2 reduction goals represents a new dimension of this challenge."
Unknown is whether the scientific community can develop revolutionary technologies, like an interactive electrical grid, that will be accepted by a public accustomed to an unlimited supply of affordable energy. Even less clear is whether sufficient time exists to find the answer.
Web site provided by Oak Ridge National Laboratory's Communications and External Relations