How the Lights Stay On

Chapter 3: The Long Road

If you have ever driven on a highway in the United States, you have seen them.

Giant lattice-work towers, taller than most office buildings, marching in a long line across farmland and hills and forests. The wires between them sag in graceful curves — three of them, sometimes six, sometimes more. The towers keep going as far as you can see. They cross rivers. They climb ridges. They thread through gaps in the mountains.

Where do they come from? Where are they going?

The honest answer is that they are going from somewhere with a lot of electricity to somewhere with a lot of people, and almost everything else about the grid — the synchronized machine from the last chapter, the lights in your house, the air conditioner at your school — depends on them.

This is a chapter about wires. About why they have to be so big. About why they have to go so far. And about why building new ones may be the single hardest problem in clean energy today.

Power plants are not, as a rule, in cities. Cities have people, and people do not want a coal-burning plant or a nuclear reactor in their backyard. Even cleaner plants are usually built far from where the electricity gets used.

There are also good natural reasons. The biggest hydroelectric dams need rivers in steep valleys. The best solar resources are in deserts. The best wind resources are on the Great Plains and offshore. None of those places have very many people.

So the American grid was built with a kind of permanent puzzle. The places that make electricity are not, mostly, the places that use it. The Hoover Dam sits on the Arizona-Nevada border, far from any major city. But it powers Los Angeles, almost three hundred miles to the west. The hydroelectric dams of the Columbia River sit in eastern Washington and Oregon. They power Seattle and Portland and, through one of the longest transmission lines in North America, Los Angeles again.

To bridge that gap, you need wires that can carry a lot of electricity, a very long way, without losing too much of it on the trip.

This turns out to be harder than it sounds.

Here is the problem.

When electricity flows through a wire, it meets a tiny amount of resistance. The wire heats up. That heat is energy that was supposed to reach your toaster but instead went into warming the air around the wire. It is lost. Gone. Wasted.

The longer the wire, the more heat. The more current flowing through, the more heat.

How much heat? The important part is this: the heat lost goes up with the square** of the current.** Double the current, four times the heat. Triple the current, nine times the heat. Push too much current down a wire and the losses become enormous — or the wire physically melts.

For a long time, this was the wall. You could only run electricity a few miles before so much of it was lost as heat that the whole enterprise stopped making sense.

The way around the wall is one of the most elegant tricks in all of engineering. It is so important that the entire modern world depends on it. And almost nobody outside electrical engineering ever thinks about it.

The trick is voltage.

The amount of power flowing in a wire is not just the current. It is the current multiplied by the voltage. Power equals current times voltage. P = I × V.

This means there are two ways to send the same amount of power down a wire. You can have lots of current at low voltage. Or you can have a little current at high voltage. The power delivered is the same.

But the losses — the heat — depend only on the current. So if you keep the voltage low, you need a lot of current, and you lose a lot to heat. If you crank the voltage up, you only need a little current, and you lose almost nothing.

This is why transmission lines have such enormous voltages. The wires you see on those giant lattice towers might be running at 345,000 volts. Some run at 500,000 volts. The newest “ultra-high” lines run at 765,000 volts in the United States, and up to 1,100,000 volts in parts of China.

For comparison, the outlet in your wall runs at 120 volts.

The lines are held high in the air by giant porcelain insulators, well away from anything that could touch them — or anything they could touch. If you got too close to a transmission line, the voltage could leap through the air to reach you. That is how dangerous they are. That is also how efficient they are.

But there is a problem.

The appliances in your house cannot use 345,000 volts. They would melt. They are designed for 120 or 240 volts. So somewhere between the power plant and your toaster, the voltage has to come back down.

The piece of equipment that does this is called a transformer. You have probably seen them without knowing it. The big gray canisters on top of utility poles in suburban neighborhoods? Those are transformers. The fenced-off grids of equipment beside highways, with humming sounds and warning signs? Those are substations — full of transformers. The slightly larger gray boxes that sit on the ground in newer developments? Also transformers.

A transformer is, mechanically, simple. It is two coils of wire wrapped around the same iron core. Electricity flowing through one coil creates a magnetic field in the iron, and that magnetic field creates electricity in the other coil. If one coil has more loops than the other, the voltage changes when the electricity moves from one to the other.

More loops on the output side: voltage rises. This is called stepping up. Used at the power plant. Fewer loops on the output side: voltage falls. This is called stepping down. Used at the substation.

So the actual journey of electricity from the Hoover Dam to a lamp in Los Angeles goes something like this:

The generator produces electricity at maybe 20,000 volts. A transformer at the plant steps it up to 500,000 volts. The electricity races across the desert on transmission lines. A substation outside Los Angeles steps it down to 13,000 volts. Smaller transformers on neighborhood poles step it down again to 240 volts. The wire enters a house and powers the outlet, which delivers it to the lamp at 120 volts.

Voltage up, current low, losses low, distance covered. Voltage down at the destination, current up to a level appliances can use. The whole grid, all the way from the dam to the lamp, is just this trick — performed thousands of times along the way.

In the 1880s, this was not yet a settled matter. There was a great public argument over how electricity should be delivered, and the two sides hated each other.

On one side was Thomas Edison, who had built the first commercial electricity system in lower Manhattan. Edison ran his system on direct current, or DC — electricity flowing steadily in one direction. The trouble was that the transformer trick we just learned does not work with direct current. With DC, you could not easily step the voltage up and down. So Edison’s power plants had to be very close to their customers — within about a mile — and the wires carried thick, heavy currents at low voltage. To cover a city, you needed a power plant every few blocks.

On the other side was George Westinghouse, with help from a brilliant inventor named Nikola Tesla. Westinghouse and Tesla championed alternating current, or AC — electricity that swings back and forth, the way the grid still works today. Alternating current has a useful property: a transformer does work with it. So you could generate AC at one voltage, step it up for transmission, step it down for distribution. One power plant could light a whole city, with the plant located far away from anyone.

The argument got nasty. Edison’s people staged public demonstrations electrocuting animals with alternating current to prove it was dangerous. Westinghouse and Tesla, for their part, pointed out that you could deliver electricity to far more people, at far lower cost, with AC.

In the end, AC won. The grid you live on today — the synchronized machine from Chapter 2, all sixty hertz of it — is Tesla’s grid.

But here is the interesting twist.

In the last fifty years, direct current has quietly returned. Not for distribution. For the very, very long lines.

It turns out that for enormous distances — hundreds or thousands of miles — DC has some advantages AC does not. AC lines lose extra energy from a kind of pulsing magnetic effect along their length, which DC does not. DC lines can also carry more power on the same physical wire. And DC makes it easier to connect two electrical systems that aren’t synchronized to each other.

So engineers built converters — massive electronic stations that can change AC to DC and back. The electricity flows out of the power plant as AC, gets converted to DC for the long haul, travels hundreds of miles as DC, then gets converted back to AC at the destination, where the local grid still runs on Tesla’s old design.

These are called high-voltage direct current lines, or HVDC. The Pacific DC Intertie, which runs almost 850 miles from the Columbia River in Oregon to Los Angeles, is one of them. It was completed in 1970 and is still working. China has built the longest in the world: a single line running more than 2,000 miles at over a million volts, from hydroelectric dams in the western mountains to the cities on the eastern coast.

Edison was right about direct current, eventually. He was just about a hundred years too early.

If transmission is so clever, and the physics is so well understood, why don’t we just build more lines? Why is the United States still struggling to connect its wind farms in Wyoming and its solar farms in Arizona to its cities on the coasts?

The answer is not engineering. The answer is permitting.

Building a new high-voltage transmission line in the United States requires getting permission from every single landowner whose property the line crosses. It also requires approval from every state the line passes through. Each state has its own rules. Each county has its own rules. Each landowner has their own opinion. Every step can be appealed in court.

A famous example: a project called Northern Pass was supposed to bring clean hydroelectric power from Quebec into New Hampshire and from there into the rest of New England. It would have lowered electricity prices, reduced emissions, and increased reliability. It was proposed in 2010. It was killed in 2018 by opposition from New Hampshire residents who did not want transmission towers on their land. New England is still paying more for dirtier electricity than it would have with Northern Pass.

A more recent project, SunZia, brings wind power from New Mexico to Arizona and California across about five hundred miles. It was first proposed in 2006. It took seventeen years of permitting fights, environmental reviews, and lawsuits before construction began. Wind power was a relatively young technology when the project started; by the time it was approved, wind had become one of the cheapest electricity sources in the world.

This is why, in earlier chapters, I have mentioned permitting paralysis as a real American problem. It is the bottleneck for almost everything in clean energy. You can have the best wind and solar potential in the world. You can have the cheapest hardware. None of it matters if you cannot get the electricity from where it is generated to where people live.

By comparison, China can build a 2,000-mile transmission line in about three or four years. We will come back to that comparison — and what it costs underneath — in a later chapter.

For all the cleverness, the modern American grid still loses about five percent of all the electricity it generates to transmission and distribution losses along the way. Five percent does not sound like much. But the United States generates roughly four trillion kilowatt-hours per year. Five percent of that is two hundred billion kilowatt-hours — more than the entire annual electricity use of many countries.

That is what is leaking out of the wires as heat, between the power plant and your outlet, every year. It is the price the grid pays for distance.

In a world that needs more clean energy fast, in places far from where the electricity is wanted, the long road is not getting shorter. It is getting longer. And the wires we are going to need over the next fifty years are wires that have not yet been built, on land that has not yet been crossed, through political and legal fights that have not yet been won.

The next time you drive past one of those lattice towers, look up. They are not background scenery. They are the answer to the question of how a power plant in one state lights a lamp in another. They are the long road.

We just have to build a lot more of them.

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