Monday, May 28, 2012

Is on the grid greener than off?

Photo: The Womerlippis' own propane-powered back-up generator, which is only needed when the grid power goes out.

Here's an interesting island conflict, slightly reminiscent of some of the ones I've witnessed in Scotland and Maine:

The pro-solar islanders seem to believe that having connectivity to the power grid is worse, environmentally speaking, than producing your own power. They also seem to think that solar power can't be produced if you're on-grid. In this, they fall into the same kind of mental trap that a lot of enviros fall into: assuming that small is always beautiful and that the "system" is always corrupting.

There may indeed be desperately corrupt elements in the Floridian power markets that I'm unaware of, but in general, small is not always beautiful, especially when it comes to power production. Living off grid is not only inconvenient, but downright polluting, if the power you use is produced wholly or partly by relatively small household generators. And the best format for efficient use of solar photovoltaic power is to be firmly connected to the grid.

My wife and I learned this lesson the hard way when we built our own off-grid straw bale house. We no longer live there, and there's a good reason. Several good reasons, in fact. But one is that our off grid house was terribly polluting. It was unsustainable and so we decided not to sustain it.

Go figure. But it's true. Small isn't always beautiful. Small can be dirty and polluting.

All renewable energy sources require back-up power, which can come from the grid, or from a home generator. This is because renewable energy comes from weather: sun, wind and rain. The alternative to not having a generator is to simply not use power from time to time, when because of the weather there's no sun, or wind, or water in the creek. The larger and more diversified your power system, the less you need to use your generator. One Internet acquaintance of mine who lives on a Scottish island, and is so far from the grid that he must make his own power (and thus can't be accused of making this mistake), has solar, wind and hydro power, a total investment of many thousands of dollars, and so rarely uses either of his two Lister generators. But he's an exception, and an expert mechanic and engineer to boot, and so he can lower his costs by installing and repairing his own equipment.

Small gas and diesel generators are notoriously inefficient and polluting. The smaller the generator, the more pollution produced per unit of electricity, and the less electricity produced per unit of fuel. Propane and natural gas generators are marginally less polluting, but still inefficient.

But if your home solar PV system is connected to the grid, it can be sized smaller, saving lots of money, and it won't need a back-up generator, saving yet more money. Put the savings into some other renewable energy investment, and you will have achieved something much closer to an optimum use of resources.

(Understanding this efficiency/pollution relationship is actually a fine application of the Second Law of Thermodynamics, and makes a great classroom module in critical thinking.)

If you want to use renewable energy, especially solar PV, it's nearly always cheaper, and less polluting, to be connected to the grid that it is to try to live off-grid. Unless, as I said, you're prepared to invest in a lot of different energy systems, so that, for instance, you can take advantage of the fact that when the sun doesn't shine the wind is often blowing. But when there's no sun and no wind, you will either start the generator, or do without. Doing without is fine if you can live without electrical water pumping and food refrigeration. Most folk can't or won't live without these things.

Otherwise, you're going to start your generator, and your green ambitions will evaporate in a small, private, and totally unsustainable off-grid cloud of air pollution and greenhouse gas.

What's funny about our own experience is that people still write to us about our off grid house, always fulsome in praise of the clean, green. off-grid lifestyle.  When we try to educate them about why off-grid is generally more polluting, they don't believe us.

Sometimes they even become rude.

Prejudice dies hard, doesn't it?

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