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Blackouts Illuminate the Bright Side of Rooftop Solar

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By Ben Jervey, OnEarth Magazine

As more than 8 million people huddled around candles or sadly dumped their spoiled food during the power outages spawned by Superstorm Sandy, several friends who know my interest in renewable energy asked me very seriously about whether they should run out and put solar panels on their rooftops.

During a disaster like Sandy, they wondered, could a photovoltaic array have kept the lights on or the refrigerator running while the rest of the grid went kaput?

Credit: Egan Snow

Sadly, I had to tell them (and you): it depends.

In the Northeast, rooftop solar arrays tend to be tied to the grid. This is good for the utility companies, because they get any extra electricity not used by the homeowner. But it’s also really crucial for the homeowner, because it allows any solar-outfitted house or apartment to draw power from the grid at night or whenever demand exceeds the PV panels’ level of energy production.

Unfortunately, in most cases, that means that when the grid goes dark, so do any solar-outfitted homes that happen to be tied to it. That’s because these systems funnel electricity from the panels down through an inverter (which converts the charge from AC to DC) and then into the home’s fuse box. Any excess electricity is sent out to the broader grid, which could be a safety hazard for workers trying to restore downed power lines. So the inverters are programmed to shut down whenever the utility’s grid goes dark, for safety reasons.

There is a solution: a hybrid system that stays tied into the grid when the utility is up and running, but can separate itself during a power outage and operate on its own with the aid of battery banks or modifications to its circuitry.

Take, for example, the case of the Villani family, whose Long Island town lost power for more than three days. Their 4.8-kilowatt PV array is connected to the grid, but it also has a battery bank, so their house never went dark. “We had friends and neighbors coming over to charge phones and batteries,” Stephanie Villani says. A similar scene played out on the flooded banks of the East River in Manhattan, where Solar One, a showcase building that’s run by the organization of the same name (full disclosure: I used to work with this organization), was producing power from its rooftop solar array even before the brackish water had fully receded from its front steps. Neighbors in Stuyvesant Town-Peter Cooper Village -- the sprawling, 35-building apartment complex nearby -- eagerly accepted Solar One’s invitation to come over and charge their gadgets.

Neighbors charge cell phones, computer at Long Island house with a battery array. Credit: Solar One

So why don’t more businesses and households add a battery bank to their solar systems? It’s expensive, for one. An inverter and a couple of batteries -- just enough to keep a few household appliances and some efficient CFL lightbulbs aglow -- can easily run a couple thousand dollars. These battery systems come in a whole range of shapes and sizes, but the most common ones look pretty much like a car battery. Typically, they’re installed with the inverter right next to your electrical panel, though if flooding is a concern, the basement might not be the best place to keep them. Another annoyance: all but the most expensive batteries (called sealed “gel” or absorbed glass-matt) require regular maintenance. If you’re not the type to change your car’s oil every 3,000 miles or your Brita filter every couple of months, you’d want to dish out the extra cash.

The second reason this hybrid model is so uncommon is that a growing number of solar households are customers of leasing programs, like those offered by SunrunSungevity and SolarCity. These programs don’t provide battery storage and don’t allow customers to make modifications to the services they provide.

Which isn’t to say there aren’t some real advantages to these programs in times of natural disaster. John Steeves is a Sungevity customer in southern New Jersey. According to the terms of Steeves’ contract, Sungevity technically owns the panels on his roof; he is simply purchasing the power that they generate. As he and his family nervously watched TV and saw that the storm was heading directly for them, “it was a relief to know that any damage was [Sungevity’s] responsibility,” Steeves said. Not that it mattered in this case. Steeves’s panels fared just fine, and so did the vast majority of arrays battered by Sandy. It’s tough to come up with comprehensive numbers, but Susan Wise of Sunrun told me that her company received service calls from just 0.7 percent of its customers in Connecticut, New York, and New Jersey. Of those calls, “the majority involved roof leaks and not damage to the panels.”

Yes, Steeves lost power after the storm, and he does “wish that maybe [he] had a battery bank,” but at least for him, power during a blackout isn’t the main reason for leasing solar panels. “The rates in New Jersey are so high,” he told me. “I’m constantly trying to figure out how to save more. If I could install more panels and buy more power, I would.”

Credit: flickr/Mike Berta

As any impartial solar expert will tell you, the PV system you choose, and whether to buy or lease, depends entirely on your personal finances and what you want out of the system. If 24/7 self-reliance is your main concern, and you’ve got the funds to do it, the hybrid grid-tied system with a battery bank is ideal. If you just want to cut your electricity costs and add some clean electrons to the grid, leasing works just fine.

But for sake of discussion, let’s take a quick, crude look at the numbers and compare a couple of average-sized systems.

The Villanis bought their system back in 2003 -- “I think it was the first to plug into LIPA’s grid,” said Villani -- when panels were much more expensive and feeding power back into the grid was still a novelty. A similar 4.8-kilowatt system today with a typical battery bank would run in the ballpark of $15,000 ($28,000 upfront, before all the hefty federal and state tax credits), according to GetSolar.com.

For anyone who might balk at those kind of upfront costs, the lease (also sometimes referred to as a "power purchasing agreement") could be more palatable. You can lease panels for no money down, and your monthly costs are set when you sign your contract. Really, you’re just replacing the more expensive watt-hour from the utility with cheaper ones you’ve committed to buy from the company that owns the panels on your roof. Steeves’ rates from Sungevity are locked in for the full 20-year agreement, so he’s insulated from constantly rising utility costs.

For now, none of the three big leasing companies have immediate plans to offer battery options -- even after the inevitable spike in demand post-Sandy -- citing expense and maintenance concerns. Danny Kennedy, the founder and CEO of Sungevity, hopes that backup storage will soon be redundant. He sees a future grid where the plug-in electric car in your garage would provide most of the storage you’d need, and where local “microgrids” would feature community-based backup storage.

But before those technological hurdles are cleared, solar lease customers will have to keep up their stocks of flashlights and candles, just like the rest of us.

This article is provided by NRDC's OnEarth magazine, a Climate Central content partner, and appears online at onearth.org

Comments

By Joe Yoder (Montpelier, VT)
on December 3rd, 2012

Good article, except I have to point out that you have left out of the discussion one option that really speaks to this issue, the battery-based stand alone system.

My wife and I have had one since 2006. It is less expensive and less complicated than a grid-tie battery back-up system.

I don’t find battery maintenence to be any big deal. Since deep-cycle flloded lead batteries are better performing, longer lasting and cost less than “maintenance free” types, it is well worth the trouble of checking the water levels every couple months.

We have opted to also keep our house wired to the grid. So our solar power has its own set of wires and outlets. Kind of a stand-alone/grid parallel system. Why? Well, we live in town anyway, and the grid makes a great “back-up” to our solar power.

a couple months ago a storm knocked power out for the night in our neighborhood. My neighbors across the street with their 20k grid-tie sytem were just as dark as every other house, while we had the only power to be seen.

For any who might wonder, our 1/2kw system with (x4) 248ah batteries cost about $6K (learning curve included), minus a $2K federal tax credit available at the time.

And, oh yeah, cutting waste and using energy efficient technology is a big part of why we only need a 1/2kw system.

Questions?  looongerbeard@yahoo.com (not a business)

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