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  • January

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    2012
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The Pleasures and Pitfalls of Off-the-Grid Solar

For our year living in the woods of Maine, I wanted a place where I could see and hear wildlife. Someplace both quiet and remote.

In our part of Maine, quiet and remote means off the electrical grid. Our summer rental cabin had no electricity except for a small generator to power the water pump and a 20-watt solar panel connected to a 12-volt battery powering our laptop and cellphone. The winter rental cabin where we are now has a diesel generator and a battery bank.

Having a diesel rumbling in the background is not the Maine woods experience I wanted. Too noisy. Too smelly. Too OPEC.

What about solar, I thought? It seems to work great on my pocket calculator and all those highway construction signs. Here was my chance to try solar without my wife’s objecting to the expense.

I became an Internet instant expert and found that in the last three years, theretail price index for solar modules has dropped almost 50 percent as a result of a flood of Chinese exports and German subsidies. For the size of the system I wanted, solar seemed affordable.

Once in Maine, I found a local expert on solar, asked for a detailed cost estimate, cross-checked it with people who knew solar and drained $6,000 from our savings to install six modules (panels) totaling 1,410 watts of power.

Then the real learning started.

I learned that installed capacity is different from actual energy generated. TheNational Renewable Energy Laboratory estimates that solar power production in the ZIP code for our system over the last four months in an average weather year should be 441 kilowatt hours. Our system produced 305 kilowatt hours in those four months — 31 percent less.

The tilt of the modules is 45 percent, the same as our latitude, which is what most experts recommend for a fixed array, and the orientation lines up perfectly with the noonday sun, which is the way it should be. Yet even on a clear and sunny day, we don’t see the factory-rated output of 1,400 watts from the system. Around 1,250 watts is the max. Factory-rated output is not woods-of-Maine output.

I learned that energy generated is not the same as energy that can be used. When the solar panels convert photons to electrons, it’s DC power, but we need AC power. The DC power is stored in a large battery bank, and an inverter switches it to AC, losing about 23 percent of the power generated in the process.

I learned that moonlight on the solar modules produces power, and I love the thought of lunar power for my laptop, however small it may actually be.

I learned from plugging our electrical appliances into a Kill A Watt meter that we use 5.9 kilowatt hours of electricity on the average day. This is equivalent to one load of laundry with an electric washer and dryer. As one can see in this table, we could not cut our electricity consumption much more and still live a connected life, which is a necessity given that we have to have an income to make the year in the woods work financially.

How does this compare with the electricity consumption of others? Well, we are using 76 percent less electricity than the residential average in Maine, which is already the lowest in the nation. We use 81 percent less (178 kilowatt hours versus 958 kilowatt hours a month) than the residential average for the United States over all.

The bottom line is that our solar production provides only 46 percent of what we need, and what we need is minimal.

The result is that we run the diesel generator every few days. In four months, we’ve had 89 hours of noise and smoke and burned 45 gallons of diesel. Not what I expected.

Our three boys hate to hear the generator running. It is not the noise or smell they dislike but the water and the work. The diesel generator produces more energy than the batteries can absorb, so we use the extra electricity to power the water pump for showers and the vacuum cleaner for the floors.

Our two cats have learned to stay out of the way when the generator is on because bad things happen like wet boys dripping on them and the howling vacuum getting too close.

Our solar system was installed in such a way that we can take it back with us to New Jersey if our Maine landlord doesn’t want it. Putting the system on the roof of our house in New Jersey and tying it into the electrical grid would eliminate the generator and the battery bank and 99 percent of the extra work. Tied into the grid is where residential solar makes more sense. Install it and forget it.

Off-grid solar works, but not yet as advertised. We would need to double the size of our solar system to cover 90 percent of our power needs, and we would still need a backup generator.

Maybe the local real estate agent was right when he called us “M.W.D.’s” — Maine wilderness dreamers. Yet I remain optimistic about solar.

Even in the woods of Maine, which has nothing close to intense sunlight, a home could be largely energy-independent and environmentally benign with about 220 square feet of solar panels and enough land to grow firewood. Yes, it might be a dream, but it’s one that can withstand the rationality that comes with the morning coffee.

Original post from NYT.
The Pleasures and Pitfalls of Off-the-Grid Solar

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