Beyond the Smart Grid: Utilities Will Still Need Electric Storage

Despite assurances that the smart grid will help the U.S. ease into the renewable energy era, experts said recently that electronic intelligence by itself won't solve one of the energy industry's most pressing problems: What will we do when the wind's not blowing?

That simple problem — largely ignored amidst a rising flurry of corporate and government activity surrounding the smart grid — can still only be solved by old-fashioned energy storage techniques, experts say. Such techniques include "pumped hydro," compressed air energy storage (CAES), and mammoth battery farms, in addition to the smart grid.         

"While the need for pumped hydro and compressed air may be less if you have a substantial smart grid, you're still going to need storage," says Haresh Kamath, a project manager for the Electric Power Research Institute Inc. (EPRI). "The storage will be closer to the customers, but you'll still need batteries and flywheels and all the balancing resources."

Renewables Dilemma
Energy industry engineers believe that little has been said about energy storage because it has been overshadowed by attention to the smart grid. The global market for smart-grid software is expected to triple in the next five years, with such corporate giants as Cisco Systems Inc., General Electric Co., IBM Corp. and Siemens AG helping to boost sales of the technology from $4.5 to $16 billion annually.

The flood of smart grid participants is largely connected to growing mandates for use of renewables. Such states as California and Colorado are looking to have renewables make up 30 percent of their energy. The European Union is moving aggressively, calling for 20 percent renewables by 2020, while Great Britain is shooting for 30 percent, despite the fact that it got just 1.4 percent of its energy from renewables in 2005.

The problem with using such high percentages of renewables, however, is that their contribution can quickly drop off to zero when the wind isn't blowing and the sun's not shining. Because power plants can't store gigawatts-hours of energy for days on end, utilities need so-called "balancing resources" - that is, sources of energy to pick up the slack when the wind's not blowing.

That's where the smart grid could help. In its most basic form, the smart grid could provide pre-arranged
"demand management," enabling utilities to turn off certain loads at times of peak demand.

"Instead of having your water heater turn on at six o'clock at night, when demand is high, it could turn on at midnight, when demand is lower," says George Crabtree, senior scientist and Distinguished Fellow in Argonne National Lab.'s Materials Science Div. "The idea is to move things around a little to help take the peak off the demand."

Engineers say the smart grid will also help utilities by providing data in real time, sometimes from the simplest and most obvious sources. Electric meters, for example, will be able to communicate with utilities, "telling" them what's happening in a particular area at a certain instance in time.

"The whole idea of the smart grid is to have more control over what happens on the load side," Kamath says.

Still, experts say it's not clear that the smart grid's capabilities will be able to compensate when 20 to 30 percent of the country's power is suddenly lost because the wind fails to blow.

Energy Storage Solution
For that reason, most experts believe the U.S. will need sources of electrical storage when the country's ratio of renewable power reaches between 10 and 20 percent.

Though seldom discussed, the idea of storage has been around for decades. Utilities have long used "pumped hydro," for example, in which power is employed to pump water up a hill in off-peak hours. Technically, pumped hydro is considered viable because it allows utilities to employ the potential energy of the pumped water (as it flows back downhill) to spin a generator and create electricity at times of peak demand.  Similarly, utilities have proposed the use of compressed air energy storage (CAES) in caverns below ground, and have begun building giant battery farms in which energy from wind and solar can be stored for later use. In Alaska, for example, the Golden Valley Electrical Assn. now uses a 27 MW battery farm as a back-up to its electrical grid. More recently, a concept called vehicle-to-grid, in which parked electric cars send energy from their batteries back to the grid, has also gained favor in certain sectors.

The bottom line, say experts, is that the U.S. can't employ an energy diet of 20 to 30 percent renewables and expect the smart grid to pick up all the slack on cloudy, windless days. To make it happen, they say, the nation's electrical system will need to add storage in conjunction with the smart grid, and will also need a more effective system of transmitting power from region to region. In the meantime, experts say the need for storage is going to grow in conjunction with the increase in renewable forms of energy. "It's not unusual to have a whole day with no wind," Crabtree says. "You can handle today's percentage of renewable energy with little or no storage. But if we're going to a 20 percent or 30 percent penetration of renewable energy, we won't be able to do that anymore."

For more information:
Electric Power Research Institute Inc.
Argonne National Lab.
Golden Valley Electrical Assn.