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Solar Electric Backup for Disasters? Not as Easy as You Think

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Fires, floods, tornadoes, derechos, hurricanes and earthquakes shatter the lives of a few very quickly, but cause lingering problems in the aftermath for many. Electricity can be out for weeks on end as power line repairs are made, with deaths from heat stress, failed medical equipment and more very common. The fires here in Colorado last month hit my area hard; some locations are still waiting for power to be restored. An estimated 3.7 million people lost power during last month's East Coast derecho, many for over a week.

So, why not just cut that electrical umbilical cord from the power company to your home and go off grid completely, in the middle of the city or suburbs? The power company keeps raising their rates each year anyway. Throw some solar panels on the roof and a wind turbine in the backyard. Looks like there's a couple funny looking black boxes involved too, just order 'em online.

Antique technology

Unfortunately it's not that simple, and not cheap. The problem is, how do you store energy for when the sun isn't shining and the wind isn't blowing? A solar array and wind turbine with no battery backup will not power anything in your house if the grid goes down. Only a battery bank or engine generator can do that.

And let's face it, we're stuck with 1859 technology when it comes to storing a lot of electrical energy at a reasonable price: the lead-acid battery. Gaston Planté, Thomas Edison and Henry Ford would all instantly recognize the batteries used today in off-grid power systems, and likely comment that "That's odd, they haven't changed much in all these decades..." And that's the rub.

There are certainly high-tech options out there, like Nickel Metal Hydride cells used in the Toyota Prius, the Lithium Ion cells in the Tesla Roadster (and also in your laptop computer), and of course over-hyped hydrogen fuel cells. None of these new energy storage technologies has matured yet -- at least not to the point that makes them affordable for or compatible with powering a typical home for even 24 hours.

Even worse, all batteries wear out. Pull a battery bank down too low too often or leave it that way for too long, and you might get only one to four years of life instead of the eight to 10 normally expected. Amortize the cost of the batteries and installation over the years, and you can rack up a pretty expensive "battery bill" each month, just for the privilege of owning them.

Electric vehicles for backup power?

The 2011 earthquake and tsunami in Japan spurred automakers there to start providing options where electric and hybrid vehicles can provide power for lights and appliances during a blackout. Toyota says that a full 12-gallon tank of gas in a 2012 Estima with the power inverter option could energize a home for 2 days at full 1.5 kilowatt output, but that still involves running an extension cord and power strip into the house, and plugging appliances into that. Works in a pinch, but not particularly safe or convenient.

Mitsubishi and Nissan have both announced they are working on standardizing systems and equipment so a car can power home mains circuits, and Sharp Corporation revealed their new "Intelligent Power Conditioner" that's in development to solve the tricky issue of making different cars, battery banks and home power systems send power back and forth to each other. Great concepts, but unfortunately "in development" is the operative phrase right now.

A sensible approach to emergency home power backup

The average U.S. homeowner consumes roughly 33 kilowatt-hours of energy every 24 hours. Lead-acid batteries to provide 24 hours of backup at that rate would come in at about $9,600, weigh almost two tons, last only seven to 10 years and take up an entire small room. A lithium ion battery bank to do that -- say from a Tesla Roadster -- would cost $36,000 with a rated lifespan of about seven years. Those costs are just for the battery bank and don't include all the black boxes needed to connect it to your home.

Instead, I recommend a more sensible approach for most people. The more serious you are about backup power, the farther you'll make it down this list:

  • Conserve energy -- Replace older appliances and lighting with new, energy-efficient models. Install insulated windows and doors. Upgrade your wall and ceiling insulation, and caulk air leaks. Besides lowering your power bill, reducing your ire toward the power company and gaining you federal tax credits, you'll need less backup capacity during a blackout.
  • Install a backup transfer switch -- Actually, have an electrician install it. This automatic device lets you use any portable generator to safely power everything in your home, right through your normal circuits, during an emergency. Don't even consider a trip to the hardware store to build a double-male extension cord to plug your generator output into a wall outlet--that's illegal because it could electrocute a lineman trying to restore your power, and you'll be liable.
  • Install a reliable propane generator -- Propane keeps for decades in pressurized tanks, and most propane generators can be used with utility natural gas service too. Many can be fitted with auto-start circuits that detect blackouts. Gasoline generators are the most common and least expensive, but gasoline is problematic in cold weather and spoils quickly in storage, even with stabilizer additives. Liquid gasoline is also quite dangerous to store in your garage, at least in quantities large enough to power your house for days or weeks. And gas stations need electricity to run their pumps, too.
  • Have an electrician install a "critical loads" sub-panel for you - This secondary breaker box isolates all your most critical loads, like the refrigerator, freezer, water pressure pump, a few lights, and a few outlets (for a portable TV to keep up on emergency news, etc.) When the grid goes out, shut off everything but the critical panel if you need to conserve generator fuel. And, you'll be paving the way for a future battery backup system with solar power to charge it.
  • Consider a grid-tied solar energy system with battery backup - This is a big step, so do your homework. Your conservation efforts and a critical loads sub-panel will save you money on solar, but don't expect to get into it for less than10,000. Small, portable "emergency solar power systems" popular in survival and preparedness publications and websites might run a few small lights and a portable television for you during an emergency, but won't power your fridge, freezer, furnace blower or air conditioner for more than a couple of hours.

Wind power systems are a terribly ineffective waste of money unless installed high in the air -- the small wind industry standard is at least 30 feet above anything within 500 feet in any direction -- and most locales strictly regulate such tall towers, especially in residential areas. So, wind is not an option for most people.

However, if your site and climate are right for renewable energy and your utility will pay you favorable rates, you might have the opportunity to reduce your electric bill to near zero, get a federal, state or local tax credit, and have ample power during an extended blackout. Contact a NABCEP-certified system installer for the straight facts on renewable energy.

Before the lights go out

Do be prepared before the next disaster strikes. But don't jump into any backup generator or solar energy solution without a lot of research, especially if you need to power critical equipment such as medical devices. Even a freezer can be considered a critical device if it's full of hundreds of dollars worth of meat! Be sure that whatever power backup solution you choose can run everything you need all at one time -- that's power, measured in watts -- and can keep it up for however long you need -- that's energy, measured in kilowatt-hours.

Consult with a professional if you have any doubts about what you are doing, and remember: If it seems too good to be true, it probably is.

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