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RV Questions and Answers

My last post on living in an RV has generated a bunch of questions by comment and by email. Instead of responding to them individually, I'm going to answer them all here.

How long did it take you to outfit the RV with solar power?

Putting solar power into an RV is a simple job, primarily because most things in an RV (everything that I use) runs of 12V DC power instead of standard household 120V AC power.

What to do with too much biogas.

On Green Thinking

At a recent show on small-scale power, I saw an interesting display of a domestic biogas generator, ideal for installing in suburban household. It's a good deal: garden waste in, three plate-hours of gas per day out, and it couples to the sewerage system so there's no maintenance. Good so far.

But then I asked the question, "what happens when you're not using the three hours of gas?" The answer is that excess gas simply vents into the sewers.

Now this is not a good solution. Biogas/sewer gas is methane, and although this methane gas in not a fossil fuel, it is still methane, with 25 times the global warming capacity of carbon dioxide. It is not something that is responsible to vent into the atmosphere. So on the one hand one can displace a fossil fuel with a biofuel, but the spillage of that biofuel leads to increased global warming.

Biogas is used, in places, to generate electricity. One can make money out of this, by capturing methane, say from a landfill, and burning it in an engine that spins a generator and sell the electricity and the carbon credits.

But the engine one uses to spin the generator is a heat engine, and immediately two thirds of the energy is lost as heat. Some methane now will not be vented into the atmosphere, which is good, but it does represent a lost opportunity: more fossil electricity could have been displaced by the biogas. Additionally, generators are expensive, require a lot of maintenance and are more inefficient the smaller they are. It would hardly be worth anyone's while to run one at home.

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