Bright Lights, Big City--Big Battery

Cities become a key proving ground for commercial energy storage technologies

By Martin LaMonica

ENERGY STORAGE: The unique abilities of energy storage, like this prototype rechargeable zinc-air battery, may find their first role in easing the energy woes of cities. Image: Courtesy of Eos Energy

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Advances in energy storage could help make wind and solar power a mainstay of our electricity system by taking root not only in the Great Plains and the Mojave Desert but also Park Avenue high-rises and urban data centers.

Some of the most compelling needs for storing energy like digital bits are now coming from businesses and utilities in cities, turning them into a crucial proving ground for a technology many consider vital for the electricity grid of the future. Cheap, multi-hour energy storage?a long sought but largely unrealized goal?could convert a variable source, such as wind and solar, into one that can supply power on demand as fossil fuel or nuclear plants do now. A solar cell converts the sun?s energy into a flow of electricity, which a battery stores as chemical energy.

In cities pockets of energy storage distributed throughout a municipality would make the grid infinitely more flexible and perhaps even more reliable. Instead of only shipping energy from big centralized power plants, batteries could supply power closer to where it is actually used. Big batteries in urban buildings or next to a utility transformer could supply energy locally when power plants are struggling to meet soaring air-conditioning loads on hot summer days.

?Energy storage in a city makes a lot of sense because cities are where the loads are, and those loads go up and down,? says Haresh Kamath, program manager for energy storage at the Electric Power Research Institute (EPRI). ?You could accommodate those shifting loads by having more power generation in the city, but it?s expensive and you?d need to tolerate the emissions, the noise and bringing fuel in.?

So why is storage still a tiny sliver of the grid?s power capacity? The main reason is cost. Low natural gas prices and stored energy from pumped hydroplants, where water is pumped uphill at night and released to run a generator at peak times, set a low bar economically. That means that scientists and tech entrepreneurs are trying to get around the low price of incumbent technologies in two ways: chasing a technical breakthrough and developing clever business models. Some of these efforts are starting to show promise.

Peak shaving
The 58-story luxury apartment building Barclay Tower in Lower Manhattan made an unusual addition to its equipment last fall: a two-megawatt-hour battery in its basement, resembling a few rows of commercial refrigerators. Based on its ability to supply about half the 550-kilowatt peak load in common areas for a few hours, saving thousands of dollars per month, building owner Glenwood Management is a convert. It plans to install similar systems at three more commercial buildings this year. Separately, the City University of New York will install a 200 kilowatt-hour commercial prototype of a novel zinc?nickel oxide rechargeable battery this summer, made by start-up Urban Electric Power, the company?s second test installation.

Unlike a battery bank in an off-grid home, these high-tech battery systems don?t provide power when the sun goes down. Instead, they do something just as important: they save on utility bills. They address the basic economics of energy supply in which commercial and industrial users pay higher rates for electricity during peak-demand hours in the afternoon and early evening. By drawing on batteries rather than the grid during peak hours, they avoid demand charges, fees linked to a customer?s maximum power draw.

For InterContinental Hotels in San Francisco, demand charges, also simply called power charges, represent about two thirds of the monthly electricity bill, says Harry Hobbs, the area director of engineering and energy manager of six hotels. To lower them, Hobbs had only one tool at his disposal: demand response, or reducing power by adjusting thermostats and other loads during peak times. But that risked guest and employee complaints about rooms either being too hot or cold. Then Hobbs stumbled on the work of Silicon Valley start-up Stem and installed one of their refrigerator-size batteries in the historic Mark Hopkins Hotel in San Francisco.

Source: http://www.scientificamerican.com/article.cfm?id=cities-show-the-way-with-energy-storage

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