Published: April 03, 2014
How to Keep the Lights on after a Superstorm
A planned micro grid in a New Jersey city could be a model for making local communities more resilient to extreme weather
For five days after Hurricane Sandy hit on October 29, 2012, large swathes of Hoboken, N.J., remained underwater and in darkness. The small city covering five square kilometers hosts three substations for the regional electric grid, all of which were knocked out of service by flooding. Some residents had no electricity for as long as 15 days after the storm.
As Mayor Dawn Zimmer walked around her municipality surveying the damage, she vowed to come up with a backup plan to keep the lights on in a catastrophe. When federal government officials flooded in to tour the damage, Zimmer asked them to help her find a way to have at least a minimal amount of power remain on during storms, no matter what. As a result, she is now working with Sandia National Laboratories, local utility Public Service Electric & Gas Co., the Board of Public Utilities and renewable energy consultant Greener by Design to come up with a plan to put Hoboken, or at least a part of it, on its own power grid. Hoboken needs to be self-sustaining during a storm, Zimmer says, because whether it's stubbornness or lack of resources, people simply don't evacuate. "I thought if we had a safer, better system of sheltering in place, people could stay in their homes through the storm," Zimmer explains.
Based on work Sandia has done for military bases, the planned microgrid will be one of the largest and most complex in the country and will serve as a possible model for other cities. "Military bases have to have power regardless of what happens around them," says Robert Hwang, director of Sandia's Transportation Energy Center, which is the lead department for this project. "We developed this design technology to meet that need."
Inside the micro grid
Any small-scale localized area with its own power generation and users of electricity qualifies as a micro grid (think: energy island). Such a micro grid is a small-scale version of the regular electric grid and can run independently or in conjunction with it. It’s considered more reliable than a conventional grid because its wires are often underground, it has multiple sources of power generation and its power is generated and distributed locally. A conventional electric grid, by contrast, uses overhead wires and has fewer, but bigger sources of power generation. If one goes out, large portions of the grid lose power. For a micro grid, think of Christmas lights: it used to be that if one bulb went out, the whole string went out. But manufacturers started to localize or segment the way the lights were wired, so that if one bulb went out, only that section of the string went out. The rest of the string would remain on. A micro grid can also achieve specific goals, like having a diverse array of energy sources and lowering electricity costs because the grid can produce its own power during peak hours on the regular grid, when electricity costs are usually high.
The micro grid itself will only be activated during times of peak usage on PSE&G's grid—because it will likely be cheaper for Hoboken to make its own power at those times—or when PSE&G's grid is down, either due to repairs or mishaps, such as extreme weather events. An operator must manually turn on or engage the grid, although it can be done remotely, even from a computer. Once the grid is on, it is designed to be able to run continuously for seven days.
The blueprint for the new micro grid spells out the sources of electricity generation, where the wires should go and lists about 100 potential buildings to be wired together. The list includes city hall, buildings that house emergency services like police and fire, hospitals, senior housing facilities, the Stevens Institute of Technology, tall buildings with elevators, a grocery store or two, and possibly some hotels and restaurants.
A draft report suggests powering this micro grid with solar panels, wind turbines and fuel cells—which are like large batteries that convert hydrogen and oxygen into water, and in the process produce electricity. The grid would also use generators fired by fossil fuels, such as combustion engines. Hoboken may also recover some of the heat thrown off by those generators and put it to other uses, such as heating buildings or driving a steam turbine to produce yet more electricity—an approach known as combined heat and power, or CHP.
Profit center, too
Hoboken will likely run its CHP generators and solar panels most often during peak prices. "We will run it on days when electricity is more expensive to buy than it is to produce," says Adam Zellner, founder of Greener by Design, a renewable-energy consultancy, who was a member of former Gov. Jon Corzine's energy policy team. "If we can make energy for seven cents and PSE&G's grid charges nine, we should turn on our grid."
Then there are the micro grids within the micro grid, known as "clusters," each connected to several types of electricity generators. These sources, say solar panels and a natural gas generator, are paired together to ensure there will always be electricity. So, when the sun goes down or the wind stops blowing, another power source kicks in. The locations of each cluster will be determined by the power needs in that section of the grid. A cluster containing cogeneration, for instance, might be situated near an apartment building, where the inhabitants use energy day and night, whereas a cluster containing solar panels might be located near an office building, which uses electricity mostly from 9 A.M to 5 P.M.
Each local power source can switch from one grid to the other because it essentially has two sets of wires: one that connects it to PS&G's grid and one that connects it to the micro grid. A power source will never be connected to both grids simultaneously. In fact, the power source must first be disconnected from one grid before it can be connected to the other.
That's no accident. One of PS&G's concerns all along has been power coming into their lines unexpectedly. What if they had a power outage and shut down a section of their grid in order to work on it? If the two grids were connected, power from the micro grid could flow back into PSE&G's lines and blow a transformer—or worse, electrocute a worker. "Their lines will not be attached to our lines," says Ananda Kanapathy, director of electric and gas asset strategy at PSE&G. "Their grid will be separated and isolated from us."
A power outage might look something like a model train set that loses power, where all of the trains and lights go off, for about 45 seconds, and then go back on. In that delay, any electricity that was being generated and flowing into PSE&G's grid must be grounded. Those power sources are then disconnected from the regular grid and switched over the micro grid.
The goal is to be more like Princeton University. During Hurricane Sandy, as residents in the streets and towns surrounding the college sat in the dark, college kids continued to read, watch television and play on their computers because the school has its own electrical grid.
In normal times the university gets most of its electricity from PSE&G. But when the storm knocked out the power, the university switched over to "island mode" and ran off of its own internal grid, built in 1996, which is powered by a cogeneration plant. By having its own way of generating power, the university was able to produce its own electricity when the regular grid was down, not unlike a house with its own generator. These generators use fuel to rotate turbines that make electricity, and because the exhaust from the turbines reach 480 degrees Celsius, the heat is also captured and put to use. Princeton's CHP plant produces 12 to 14 megawatts of electricity—less than the 12 to 30 megawatts of electricity the college usually uses, but the storm hit during fall break, when only 1,000 of the university's 5,000 students were there. Usage with the reduced population was running at about 16 megawatts, but by turning off some heaters and air conditioners around campus, there was enough power to last the five days electricity in the surrounding area was out, says Tom Nyquist, executive director of the Engineering and Campus Energy Facilities Department at Princeton.
What will it cost?
The Hoboken project is among those recommended by a Hurricane Sandy Rebuilding Strategy task force that the Obama administration formed in December 2012. Congress appropriated $50 billion for disaster relief, to help rebuild the region in the wake of the storm. The task force was created to establish guidelines for investing those funds. The goal is to develop pilot projects aimed at making the energy infrastructure more resilient. To that end, the U.S. Department of Energy and national laboratories like Sandia have been providing technical assistance to states that suffered hurricane damage. The design for Hoboken's micro grid is part of that effort.
The goal, according to the report, is not just to address Hurricane Sandy damage but to mitigate damage caused by climate change. But with all the bells, whistles and security measures that are expected to be part of Hoboken's project, some question how much it will ultimately cost. The project currently has an estimated price tag of $30 million to $50 million, according to Greener by Design’s Zellner, although it could go higher, depending on exactly who participates in the grid and how much wiring is required to connect everyone. But the question that should be asked, Zellner adds, is what it would cost Hoboken to have another 15-day blackout? "They can't afford not to act," he says.