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Dumb Meters Get Smarter

A new device could convert conventional electricity meters, making the smart grid cheaper.
March 31, 2009

Tendril, a startup based in Boulder, CO, has developed a device that converts existing electrical meters into smart meters that can track customers’ energy use as frequently as once every few minutes. Working with utility companies, Tendril plans to introduce it to thousands of homes this year.

Power remote: An iPhone application from Tendril allows residents to control the use of appliances, heaters, and air conditioners based on the cost of electricity from utilities. It also provides current information about electricity use using information from a new company device that converts ordinary electricity meters into “smart meters.”

The device could help speed the spread of the so-called “smart grid,” a network of sensors and controls that could reduce energy consumption, enable the large-scale use of renewable energy, and save consumers money. Smart-grid projects will receive billions of dollars in funding under the stimulus bill signed into law in February. Tendril’s device could be used by utilities to introduce variable-pricing schemes that discourage the use of electricity during times of peak demand, reducing the need for the most expensive and most polluting power plants. Eventually it could be used to help the electricity grid accommodate more electricity from variable sources of renewable electricity, such as wind and solar.

The new device–Tendril hasn’t yet settled on a name for it–takes advantage of a type of electricity meter that utilities have installed in recent years to reduce costs. About half of the homes in the United States now have these meters, estimates Adrian Tuck, Tendril’s CEO. They use short-range wireless signals to transmit energy usage information using a proprietary communications protocol. Meter readers, rather than manually inspecting each meter, simply drive by once a month with equipment that automatically reads these signals. These meters actually transmit the data every few minutes, though data is only recorded monthly. Tendril, working with the primary manufacturer of these meters, developed a device that reads these proprietary wireless signals and then sends the data to the utility over the Internet. Utilities can in turn transmit information about prices to consumers, also over the Internet.

The system provides a potentially much cheaper alternative to existing plans that involve replacing existing meters with “smart” meters that have two-way communications capabilities, as well as establishing new communications networks dedicated to transmitting the data, says Steven Hauser, vice president for strategy at GridPoint, a company based in Arlington, VA, that is developing a device similar to Tendril’s.

With Tendril’s device, new meters and networks aren’t needed. “All you have to do is plug it in, go to the Web and enter the serial number from your meter,” says Tuck. “It reads the signal [from the existing meter] and mimics a smart meter from that point on.”

By giving utilities detailed information about energy use throughout the day, the device could allow utilities to charge different prices depending on how much it actually costs to provide electricity. During peaks in demand, such as hot summer afternoons, utilities rely on generators that can quickly ramp-up to meet the demand. These tend to be more polluting, less efficient, and more expensive to operate than ordinary generators. If utilities can charge much higher prices at these peak times, they can discourage energy use and reduce demand, reducing the need to use these generators. But almost all homes in the United States are charged a flat rate because utilities haven’t installed the equipment needed to track energy use.

With a system like the one Tendril describes, utilities that charge nine cents per kilowatt-hour during ordinary times might charge a much higher price–say 75 cents–when demand peaks, says Harvey Michaels, an energy efficiency scientist and lecturer at MIT. Consumers could save money by using energy-intensive appliances when prices are lower, and the shift in demand could significantly reduce costs for utilities. Indeed, if pricing schemes could be used to redistribute demand equally throughout the day, no new electricity-generating capacity would need to be installed for as long as 28 years, according to an article appearing soon in the new journal Service Science by Richard Larson, a professor of civil and environmental engineering at MIT.

Tendril also has developed a group of devices, including smart outlets and thermostats, that make it possible to monitor and control the energy use of individual appliances, heaters, and air conditioners. With information from these, as well as data about price and electricity sources from the utility, a homeowner, using Web- or iPhone-based applications from Tendril, could program these devices to run only when prices are below a certain level, or when there is a certain amount of renewable electricity available on the grid.

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