The Knowledge: How to Rebuild Our World From Scratch (19 page)

POWER TO THE PEOPLE

The white flashed back into a red ball in the southeast. They all knew what it was. It was Orlando, or McCoy Base, or both. It was the power supply for Timucuan County. Thus the lights went out, and in that moment civilization in Fort Repose retreated a hundred years. So ended The Day.

P
AT
F
RANK,
Alas, Babylon
(1959)

FLICKING BACK THROUGH
the gas and electricity bills for my apartment in north London, my total energy consumption last year was a little under 14,000 kilowatt-hours (kWh). If, without access to fossil fuels, all of this energy were to be provided by maintained forestry, I’d need to burn almost 3 tons of dried wood (or 1.7 tons of more-condensed charcoal) every year, which would require more than half an acre of short-rotation coppiced woodland. But that’s assuming that it’s possible to successfully convert 100 percent of the energy locked up in a log into electricity flowing from my outlets. In fact, the multistep process of combusting fuel to generate electricity is inherently inefficient, and even modern power stations can convert around only 30–50 percent of the stored energy of their fuel into electricity.

And of course, that’s only counting the energy I use directly within my four walls, for heating, lighting, and running appliances. It misses all of that expended to support my share of the industrialized civilization I live in—the energy used in road building and construction, the
industrial processes needed to provide me with writing paper and powdered detergent, the energy required to manufacture and transport my clothes or sofa, and to synthesize fertilizer and plow fields for my meals, and the fuel burned by the train I take to work. When you divide national energy consumption by total population, you find that each individual living in the United States actually uses nearly 90,000 kWh every year, while a European uses just over 40,000 kWh.

Before the mechanical revolution in the Middle Ages that began the widespread use of waterwheels and windmills, and later, industrialization based on the exploitation of fossil fuels, the effort needed for agriculture, manufacture, and transportation was provided by muscle power alone. If we put this modern energy consumption into perspective, 90,000 kWh is equivalent to every American having a team of fourteen horses, or more than a hundred humans, working flat-out, 24/7 for them.

With the fall of industrialized civilization and the disintegration of this energy feed, the recovering post-apocalyptic society will have to relearn how to provide for its energy requirements. The advance of civilization is based on being able to marshal greater and greater energy resources, and especially on learning how to convert between energy types, gaining the capability to transform heat into mechanical power, for example.

Civilization requires not just thermal energy, as we saw in Chapter 5, but also the harnessing of mechanical power, relieving it from the constraints of using muscle power alone.

OVERSHOT WATERWHEEL. THE RIGHT-ANGLE GEAR CONVERTS THE VERTICAL MOTION INTO HORIZONTAL ROTATION SUITABLE FOR DRIVING MILLSTONES TO GRIND FLOUR.

One of the key Roman innovations was the development of the vertical, geared waterwheel: the bottom of a large wheel with paddles
is dipped into a stream or river and turned by the force of the flow. In antiquity, this water power was primarily applied to turning a grinding stone to mill flour, and the crucial mechanism that allowed this technology was the invention of the right-angle gear (dated to around 270 BC), transforming the direction of motion from the vertical spin of the waterwheel to the horizontal rotation of the grinding stone. Most simply, this can be achieved with a large crown wheel (one with pegs sticking out of the flat face of the gear) on the waterwheel drive shaft, coupled to a cylinder of rods known as a lantern gear or cage gear that is connected to the millstone. Altering the relative sizes of the crown wheel and lantern gear allows you to match the required speed for grinding to the flow rate of different rivers. These water mills were the
very first known application of gearing to transfer power, and so represent the earliest roots of mechanization.

Although it can be dunked in the flow from practically any riverbank, or even mounted over the side of a milling boat anchored in the current, the undershot wheel is woefully inefficient, and in its simplest form suffers from problems with varying river levels. Luckily it doesn’t take much technical know-how to build a far more capable and powerful waterwheel. The overshot wheel became widely exploited across Europe during the supposedly ignorant and stagnant “Dark Ages” following the fall of the Roman Empire, and, despite similarities in overall appearance, functions on a completely different principle than the primitive undershot wheel.

Rather than being stuck into the flow, the bottom of the overshot wheel is held clear of the tailrace, and water is delivered to the very top of the wheel by a chute. The overshot wheel derives its torque not from the impact of a current, but from the energy relinquished by the water as it falls. This design is far more efficient and can capture as much as three-quarters of the energy held in the head of water. Fit a sluice gate to the chute to control the flow onto the wheel, and if the stream is dammed to create a mill pond, a reservoir of energy can be built up until it is required to be expended (something that wasn’t attempted until the sixth century AD, half a millennium after the first vertical waterwheels were used, but could be leapfrogged to during a reboot).

SELF-ORIENTING TURRET WINDMILL. THE FANTAIL KEEPS THE MAIN SAILS TURNED INTO THE WIND, AND THE CENTRAL SHAFT DRIVES TWO SETS OF MILLSTONES.

Harnessing wind is technically much trickier than tapping into water power, and consequently the technology arrived much later in our history of development (although boats with sails to catch the wind for propulsion date back to 3000 BC). Water is a far denser medium than air, and so even a gentle flow carries a great deal of energy, making it an easy resource to exploit even with imperfectly designed elements and inefficient wooden gearing. Unlike the sluice gate, you have no control over the strength of the wind, so if it begins blowing too
briskly, the windmill blades or driven mechanisms can be damaged. Windmills therefore need a braking system and a method to control the effectiveness of the blades, such as reefing canvas sails. The most fundamental challenge, however, is the constantly changing wind direction; a windmill needs to be able to be quickly reoriented.

Rudimentary windmills can be built on a post and the entire structure manually turned to the wind, but for larger and more powerful fixed windmills the blades need to be mounted on a top turret able to automatically swivel around the central drive shaft to face into the wind. The mechanism employed here is ingeniously simple: a small fan behind, and facing at a right angle to, the main sails is geared to a toothed track running around the top rim of the tower, so that whenever the wind changes and blows across this fantail, it spins and rotates the turret around until it is oriented perfectly in line with the wind again.
*

All of this demands a much greater degree of mechanical sophistication than even the largest waterwheel. But once you’ve mastered wind power, your sites of production are liberated from the watercourses and can occupy even flat landscapes (like the Netherlands), or regions either without abundant water resources (such as Spain), or that are often frozen over (like Scandinavia).

FUNDAMENTAL MECHANISMS: THE CRANK (RIGHT) TRANSFORMS ROTATION INTO A BACK-AND-FORTH MOTION SUITABLE FOR SAWING, AND THE CAM (LEFT) CAN BE USED TO REPEATEDLY LIFT AND DROP A TRIP-HAMMER.

The taming of the wild power of both wind and water, coupled with the increasingly effective use of draft animals (we’ll return to this later), had a profound impact on our society, and you’ll want to achieve the same level as rapidly as possible during the reboot. Medieval Europe became the first civilization in human history to base its productivity not on human muscle power—the labors of coolies or
slaves—but on the exploitation of natural power sources.
This mechanical revolution, gathering momentum between the eleventh and thirteenth centuries, went far beyond the use of a mill to pulverize the harvest’s grain into flour. The potent torque of the waterwheel and the windmill became a ubiquitous power source for a staggeringly diverse range of applications: pressing olives, linseed, or rapeseed for oil; driving wood-boring drills; polishing glass; spinning silk or cotton; powering metal rollers to squash iron bars into shape. The elementary mechanical component that is the crank arm transformed rotary motion into a reciprocating thrust suitable for mechanizing sawmills, ventilating mine shafts, or pumping water from mines or flooded lowlands (as employed to great effect by the Dutch).
But perhaps the most versatile function was turning a cam to repeatedly lift and drop a trip-hammer—perfect for crushing metal ore, pounding out wrought iron, crumbling limestone for agricultural lime or mortar, beating dirty sheep wool to full it (to clean and compact it), and pounding mash for beer, pulp for paper, bark for tanning, and woad leaves for blue dye.

The cam mechanism was employed to heave trip-hammers for seven centuries before being replaced by steam-powered versions in the Industrial Revolution, but it lives on today under the hoods of our cars and trucks, opening and closing the engine valves in the correct sequence (see Chapter 9).

So with the appropriate internal mechanism to convert the principal rotation into the desired action, medieval water and windmills were the original power tools. The medieval world may not have been
industrial, but it was certainly industrious. And if our civilization catastrophically collapses there is hope that this technology can be employed again to rapidly reattain a base level of productivity during the reboot.

Any civilization must successfully marshal both thermal and mechanical energy. But how do you convert between these forms? Turning mechanical energy into heat is trivial—imagine rubbing your hands together on a cold day—and indeed, trying to minimize friction and the loss of useful energy to heat is the whole point of engine lubricants and ball bearings. Being able to convert the other way, though, would be exceedingly useful. Thermal energy can be provided on demand, by burning any of a number of fuels, and the capability to transform this heat into mechanical power would release you from reliance on the vagaries of wind or water and also offer a power plant for mechanical transport. The first machine in history able to effect this transformation—to convert heat into useful motion—was the
steam engine.

The central concept behind the steam engine goes all the way back to the ages-old mystery, well known to Galileo in the late 1500s, that a suction pump can’t raise water more than about 10 meters up a pipe. The explanation of this is that the air itself exerts a pressure, a force squeezing everything on the Earth’s surface, including the column of water. The implication is that the atmosphere itself can be made to do work for you. All you need is to create a vacuum within a smoothly bored cylinder with a freely movable piston and the air pressure outside will forcibly plunge the piston down; you can couple this to machinery for effortless labor. But how do you repeatedly generate a vacuum inside the cylinder? The answer is by using steam.

Vent hot steam from a boiler into the cylinder and then allow it to cool: as it condenses from vapor to liquid water, the pressure it exerts plummets and no longer balances that of the atmosphere. The piston is driven in by the force of the outside air, doing the work for you, and you can repeat the cycle by opening a valve to allow the piston to
return, and then squirting more steam in again. This is the basic operating principle of the earliest “fire engines” of the eighteenth century, and you can make certain efficiency improvements, such as adding a separate condenser so that you’re not repeatedly cooling and reheating the cylinder. But if you’re able to construct sturdier cylinders and boilers, perhaps from scavenged materials or by redeveloping skill in metallurgy, you can do much better. Rather than using the sucking effect of steam condensing in the cylinder, build the steam up to a higher pressure and you can use the expansive force of the hot gas—the same whoosh as in an espresso machine—to drive the piston first one way within the cylinder, then back again from the other side.

The primary output of a steam engine (as with any piston-based heat engine, like the car motor we’ll return to in Chapter 9) is the plunging back and forth of the piston. This is fine for pumping water from mines, but for most applications you’ll want to transform that reciprocating motion into a smooth rotation. The crank will perform this conversion for you, just as we saw for windmills, and produce an action suitable for driving machinery or a vehicle’s wheels.

You might think that steam engines represent exactly the sort of transitional technological level that you would aspire to leapfrog over during a reboot, straight to internal combustion engines or steam turbines, which we’ll explore in detail later. But steam engines offer two major advantages over more advanced alternatives, and so you may need to recapitulate this developmental stage. First, they are external combustion engines and don’t require refined gasoline, diesel, or natural gas to run—they are much less fussy, and their boiler can be fired with pretty much anything that burns, including scrap wood or agricultural waste. Second, a simple steam engine can be constructed with much more rudimentary machine tools and materials and with far more forgiving engineering tolerances than a more complex mechanism. We’ll return to mechanical power shortly, but for now let’s take a look at how to reboot one of the cardinal features of the modern
world: electricity.