What If? by Randall Munroe Read Free Book Online

obvious: Most lights wouldn’t last long, because the major power grids would go down relatively fast. Fossil fuel plants, which supply the vast majority of the world’s electricity, require asteady supply of fuel, and their supply chains do involve humans making decisions.

    Without people, there would be less demand for power, but our thermostats would still be running. As coal and oil plants started shutting down in the first few hours, other plants would need to take up the slack. Th is kind of situation is difficult to handle even with human guidance. Th e result would be a rapid series of cascade failures, leading to a blackout of all the majorpower grids.
    However, plenty of electricity comes from sources not tied to the major power grids. Let’s take a look at a few of those, and when each one might turn off.
    Diesel generators
    Many remote communities, like those on far-flung islands, get their power from diesel generators. Th ese can continue to operate until they run out of fuel, which in most cases could be anywhere fromdays to months.
    Geothermal plants
    Generating stations that don’t need a human-provided fuel supply would be in better shape. Geothermal plants, which are powered by the Earth’s internal heat, can run for some time without human intervention.
    According to the maintenance manual for the Svartsengi Island geothermal plant in Iceland, every six months the operators must change the gearboxoil and regrease all electric motors and couplings. Without humans to perform these sorts of maintenance procedures, some plants might run for a few years, but they’d all succumb to corrosion eventually.
    Wind turbines
    People relying on wind power would be in better shape than most. Turbines are designed so that they don’t need constant maintenance, for the simple reason that there area lot of them and they’re a pain to climb.
    Some windmills can run for a long time without human intervention. Th e Gedser Wind Turbine in Denmark was installed in the late 1950s, and generated power for 11 years without maintenance. Modern turbines are typically rated to run for 30,000 hours (three years) without servicing, and there are no doubt some that would run for decades. One of themwould no doubt have at least a status LED in it somewhere.
    Eventually, most of the wind turbines would be stopped by the same thing that would destroy the geothermal plants: Th eir gearboxes would seize up.
    Hydroelectric dams
    Generators that convert falling water into electricity will keep working for quite a while. Th e History Channel show Life After People spoke with an operator atthe Hoover Dam, who said that if everyone walked out, the facility would continue to run on autopilot for several years. Th e dam would probably succumb to either clogged intakes or the same kind of mechanical failure that would hit the wind turbines and geothermal plants.
    Batteries
    Battery-powered lights will all be off in a decade or two. Even without anything using their power, batteriesgradually self-discharge. Some types last longer than others, but even batteries advertised as having long shelf lives typically hold their charge only for a decade or two.

    Th ere are a few exceptions. In the Clarendon Library at Oxford University sits a battery-powered bell that has been ringing since the year 1840. Th e bell “rings” so quietly it’s almost inaudible, using only a tiny amount of charge with every motion of the clapper. Nobody knows exactly what kind of batteries it uses because nobody wants to take it apart to figure it out.

    Sadly, there’s no light hooked up to it.
    Nuclear reactors
    Nuclear reactors are a little tricky. If they settle into low-power mode, they can continue running almost indefinitely; the energy density of their fuel is just that high. As a certain webcomic put it: 

    Unfortunately, although there’s enough fuel, the reactors wouldn’t keep running for long. As soon as something went wrong, the core would go into