How Con Ed Uses Smart Thermostats to Control ACs and Save Energy in an Emergency

Monday August 29, 2011
Posted at 08:09

When Thomas Edison started Edison Electric Illuminating Company of New York in 1882, it supplied electricity to 59 customers in a square mile area in lower Manhattan. Almost 130 years later, the company’s descendent, Consolidated Edison Company of New York Inc. (Con Ed), is one of the largest public utilities in the United States, supplying electricity to three million residents throughout the New York City metro area.

There are a few issues when it comes to providing enough electricity for three million people. One of those issues is how to deal with a surge in electricity use, since electricity can’t be stored and has to be supplied to the electric grid continuously every day.

For example, when Con Ed set records for peak electricity use in early August, consumption surged because people ran their air conditioners harder in order to beat back a sweltering heat wave that baked much of the country. In all, the electric utility said that more than 1 trillion watt hours of electricity were consumed over a four-day period, which is roughly the equivalent to the amount of electricity that Vermont uses in two months.

To help with electricity supply issues derived from surges in consumption similar to the four-day period earlier this month, Con Ed has implemented a plan that allows it to remotely control the central air conditioners of some customers. Con Ed installs “smart” thermostats in the homes of those who agree to have them that provide the utility with the ability to cycle connected air conditioners on and off.

The 5 Steps of Con Ed’s Energy-Saving Smart Thermostat Plan

1. Recruiting — The first thing Con Ed has to do is convince New Yorkers to sign up for the program, which allows the utility to switch their central air conditioning off at its discretion. The electric utility provides the smart thermostat, which can be programmed by smartphone, for free. Other incentives include a $25 rebate check for residences and a $50 check for small businesses, as well as the promise of saving money on electric bills. So far, 23,600 electric customers have signed up for the program.

2. Monitoring — Con Ed continuously analyzes weather models at its Manhattan headquarters 24 hours a day, seven days a week. Additionally, the utility’s offices in the boroughs continually monitor the status of underground power equipment. When an event, such as an overloaded transformer, triggers an alert code, a network map displays the affected area in yellow, orange or red, depending on the severity of the problem.

3. Escalating — Once an alert code has been triggered, Con Ed responds with a heightened awareness and watches for further developments. If a significant ongoing event occurs, such as another massive heat wave like the one earlier in August that threatened the stability of the entire grid, the utility sets up a situation room to coordinate emergency measures. According to Con Ed, its situation rooms are designed to be used where they’re most needed and can be set up virtually anywhere.

4. Making the Call — When there’s a power emergency, Con Ed uses individual commanders to manage the emergency in 12-hour shifts. If the decision is made to cycle customers’ central air conditioners off and on to save power, the utility uses its “implementation contractor” to send shut-down and start-up commands via radio signals to tens of thousands of smart thermostats.

5. Shutting Down and Starting Up Air Conditioners — Air conditioners are targeted in areas made up of neighborhoods. Once the decision is made to cycle customers’ air conditioners on and off, shut-down and start-up signals are sent every 30 minutes, resulting in a cycle of 30 minutes on, 30 minutes off. Each area that’s targeted for cycling can ease electricity demand by up to 33 megawatts. Although that amount is a fraction of the 13,000 megawatts used on a very hot day (the record set earlier in August was 13,189 megawatts), the utility says it’s enough to prevent overloads and blackouts.

Sources

How Con Ed Saves the Power Grid During Heat Waves,” Wired, July 26, 2011.

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