How to power your house, with xkcd’s Randall Munroe
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How to power your house, with xkcd’s Randall Munroe


Yeah, there’s there’s my
self-portrait. People are sort of surprised sometimes that I’m three-dimensional. Take an imaginary average lot: Let’s imagine that this lot kind of has an appropriate similar fraction of all the US’s resources. You can only have the energy that’s flowing through your plot of land. So you’ve got this column of space and you can harvest the energy that’s coming from there. One of the main potential sources is that there’s stuff growing there. Plants are sort of like solar panels, they they grow on the ground, the sun falls on them and they convert that energy into a stored form, which we can then release by, for
example, harvesting them and burning them. If you took your lot here, and you just
planted a lot of trees on it, Here all these trees. And so I looked up like what’s the productivity of burning wood for fuel. You come up with 38 watts. So the average house, on average you draw about a kilowatt of power. The trees are not going to supply you with that. At best you could use this
to continuously run maybe your laptop. There’s the power that’s flowing through
the air over your house that you can take advantage of. One of the most popular ways to do this is with solar power. The way you place the solar panels
does affect their efficiency. So instead of laying the solar panels on the ground, you can tilt them up. In fact, if you want to really optimize your efficiency, you could fill the entire lot with a tilted panel. It would also mean that you would
live a life of darkness. And also whoever lived to your north would live life of darkness most of the time, because they were in the shadow of your solar panel. For most houses they don’t even need to cover their whole roof and solar panels to get enough power to power their house. If you did cover this this suburban lot with solar power, then you you would be able to generate like enough power for not just you, but for like you know half
dozen of your neighbors. Sunlight isn’t the only kind of power that’s flowing through the space above your home. There’s also the air that’s moving
through. And you can harvest some of that kinetic energy using wind turbines. So if you have sort of a typical situation above your house, the the wind will be much stronger the higher up you go. So this will now really depend on how your neighbors feel. You know, probably if you want to build a 200 meter wind turbine, it’ll be a lot more expensive and also you’ll probably get some calls from the local zoning board. You know, in this typical area, a wind turbine that’s the size of your entire yard would be capable of generating a couple dozen kilowatts of power averaged across the year. That’s enough to power your house
and a dozen of your neighbors. I think this might be the single worst idea in my entire book. The idea is that you can draw power from anything that’s moving. And tectonic plates are moving. Tectonic plates are moving you know inches per year or per decade, but they’re moving with a lot of force. and energy is force times distance. So you’ve got a really, really, really tiny distance that the plate moves but it moves with a lot of force. And that together, that kind of
adds up. So I laid out as an idea. If you live near the boundary between two tectonic plates, you could anchor a device: you have two pistons where one of them is anchored to one tectonic plate, and the other one is anchored to the other tectonic plate, and they come together and they compress some kind of working fluid. As the pressure increases you can let out the pressure by having run a turbine. And the pressure builds up very, very slowly but it can build up extremely high. If you manage to have pistons that are like the width of your entire lot and maybe twice as high, you could in principle generate enough power to keep your house powered over time. The catch is that tectonic plates don’t have a sharp border, so if you want to anchor these Pistons to the plate you’d have to anchor them way out, spreading out the force across the plate. So if you stretch out miles away You’re gonna need miles and miles of whatever this high-strength steel you’re using is that’s as wide as your house. And I worked out that the the steel would cost on the order of 40 billion dollars. That’s 40 billion dollars that you pay upfront, but then you don’t have to pay your power bill. After the first 36 million years, you’re making money. Solar and wind both both do stack up pretty well. There are a couple of these fossil fuels where you could power your house for a little while based on what’s available in this
little plot of land. But not forever. It would be more like a matter of years if you were gonna take your your land’s fair share. Whereas the the sun and the wind, there’s more like enough of those for everybody, and they’re gonna stick around for longer. So they seem like the better bet for the future.

8 Comments

  • Kenz300 x

    Wind and solar energy are safer, cleaner and cheaper than fossil fuels.
    Solar panels with battery storage means that you do not need a generator when the utility power drops.
    Save money and increase reliability, love it.

  • Corey Hannigan

    So I'm in favor of solar and wind, personally, but I are we just gonna glaze right over the uranium option? Sure nuclear power isn't literally infinite, but it's an incredibly compact way to provide tons of energy with zero carbon emissions. Again, not saying it's better than solar or wind, but it was disappointing that they didn't even mention it.

  • Stephen Jay

    Love this. One question/observation, would the ratio of solar vs wind power differ greatly based on location? For example, I am in Winnipeg, and while we have incredible summers, we would have less than ideal winters for optimal solar power generation. We always seem to have wind blowing, however.

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