This episode is sponsored by Wren, a website with a monthly subscription that helps fund projects to combat the climate crisis.

Click the link in the description to learn more about how you can make a monthly contribution to support projects like rainforest protection programs. [♪ INTRO] Green energy is not a new idea. The US has harvested electrical power from water since the 1880s; almost a decade later, there was also an electric wind turbine in Cleveland.

And now there’s a whole bunch of other types of renewables. But even though we started at this pretty early, renewables have been kind of in the background for multiple reasons, like they can start or stop at any moment. For example, when the wind suddenly gusts or when the clouds cover the sun.

This interruption doesn’t happen all that often with ol’, reliable coal, which is why it has been the grid’s backbone since forever. When you want more power, just burn more coal. And our electric grid was built around that simplicity.

But the world has gotten increasingly complicated, and now it is time to adapt. How electricity is generated and transmitted is critical for building a green energy-friendly grid. But to understand how all of that works, we need to zoom in on a traditional power plant.

Pick your favorite: Coal, nuclear, biomass, oil, whatever. They all work in a similar way because of something Michael Faraday discovered. If you move a magnet and a wire near one another, it produces electricity in the wire.

Every traditional power plant has a generator: Wires that can spin in a circle near a strong magnet, or a magnet that can spin near wires. Either way, the generator spins, and the electricity flows through the wire. If you take that wire and move it towards the magnet’s north pole, electricity will flow in one direction through the wire, just like Faraday discovered two hundred years ago.

And if you move that same wire away from the north pole, electricity will flow in the opposite direction. This cycle repeats over and over again in the generators as they spin, creating what’s called an alternating current, or AC, because the current alternates directions. In addition to AC, there is also DC, or direct current, where charge only moves in one direction along the wire.

And speaking of currents, that’s one of the two components of electricity, the other being voltage. In a broad sense, voltage measures how much energy is available, and current measures how much energy is used. That’s a simplified explanation, so do not write it on your physics final, but it’ll get us where we need to go.

When we send electricity from one place to another, the goal is to keep energy loss at a minimum. Because the more we waste energy, the more fuel we have to use to turn on the same number of lights. So, before sending electricity on a long journey, the current goes through a transformer, which changes low-voltage, high-current AC from the generator to high-voltage, low-current AC for transmission.

To sum up, this is what happens at a traditional power plant: Something hot boils water. That water vapor pushes a turbine which turns a generator, which creates an alternating current, which goes through a transformer to raise its voltage, which helps preserve energy. Some energy is still wasted as heat, since charges moving along the wires bump into atoms and get them jiggling, and create heat.

So every once in a while, transmission wires go into substations that combine power from different sources and fix the voltage with more transformers. And if electricity still has a ways to go, they nudge it back up. Now if it’s close to businesses or homes, where it will actually be used, they drop it down, so we won’t interact with anything that’s too dangerous.

All of these systems, cycles, and stations have to work together in sync, which is why we’ve traditionally relied so much on coal and, more recently, nuclear power. Because we know how much energy to expect from both of them. That means that as grid computers and engineers figure out how much electricity different areas will need, they don’t have to worry about whether the source will make as much as expected.

Now some renewables can slot right into that system. Wind turbines and hydropower plants both contain generators, just like the ones you find in a traditional power plant. They’re just spun by wind or liquid water, making the same alternating current that can be adjusted by the same kind of transformers in traditional plants.

Now if the power is coming from a reservoir that’s built up behind a dam, water can flow through and produce power when there’s extra demand, but it can also be stopped and stored up when the grid is fine without that help. Wind power, though, is trickier. Some places are pretty windy, but nowhere is always windy, even over the ocean.

And even small differences in wind speed from one minute to the next can lead to big differences in how much electricity is generated. So, it’s not as simple as just letting more turbines spin when we need more power. Relying on wind power also adds another variable into the already very complicated system.

Because engineers, in addition to estimating demand, now have to estimate the amount of power available. In other words, they need to forecast the humans, the weather, and how the humans will respond to that weather. And the same is true for a lot of renewables.

Droughts, clouds, and nighttime mean that electricity from these sources cannot be uniformly reliable. Power companies assume you’re still going to want electricity even when the sun isn’t out, so they make up the difference with something more dependable: Fossil fuels. Now, this is a common critique of renewable energy: What do you do when the wind stops blowing?

And there aren’t many great answers right now, even in countries that rely heavily on wind power. And the same goes for any other intermittent power source. The challenge is that it’s easy to have a little bit of renewables, but it’s hard to have a lot of them.

The grid just isn’t set up to have so many different sources going into it, especially when the amount of electricity from those sources isn’t under our control. But engineers are working on it. One of the major avenues of research involves ways of storing extra energy produced on particularly windy or sunny days so that it can be used later on in the form of batteries.

A big enough battery would kick on when the wind stops, smoothing out the supply that goes to the rest of the grid and removing that extra variable. But even the best batteries in the world would need to be huge to store enough energy to power your home for a long time. They’d weigh about a ton, and if they had to be replaced as often as other high-capacity batteries do, they’d cost more in the long run to consumers and utilities than electricity from other sources, even if all the energy going into the battery were free.

Engineers around the world are searching for materials that they can use to make bigger, cheaper, longer-lasting batteries. But our current batteries are proving hard to beat. Now this has not stopped some people and even some whole towns from going all-in on battery power.

In one town in Colorado, every house has solar panels, a household battery, and an electric car charger. So each home is able to move energy between batteries and outlets, depending on how much is coming in through the panels. And the homes have wires between them, too, so that electricity can be automatically redistributed to wherever it’s needed most.

Towns like these form one kind of microgrid: A little section of the electric grid that can be disconnected from the rest during emergencies without losing power. More and more microgrids are popping up around the US and around the world, as communities make and store more electricity locally. Ultimately, many engineers think that the solution to our renewable woes will be a combination of microgrids and their exact opposite: More long-distance transmission wires that can move electricity between regions.

The more we have of both, the more the grid as a whole will act like that town in Colorado: Each region will be able to operate on its own most of the time, but if something goes wrong, we have each other's backs. Other places have also gotten creative with the definition of “battery.” Normally, hydroelectric dams will produce electricity just by letting water from the lake flow downhill and turn the generators. But some will turn their generators into motors when there’s extra energy in the grid, so that the plant can pump the water back up into the lake.

That way, the entire lake acts like a big battery: It stores energy when there’s a surplus and releases it when there’s a demand. Then there are the solar panels themselves, which lead to some unique problems. Just about every source of electricity in the world uses some sort of generator, but not solar panels.

They just sit in the sunlight, which knocks electrons off of atoms in the panels and sends them down wires. Which means that solar panels create DC electricity, where the current goes in one direction, as opposed to the AC of the rest of the grid. If you plugged solar panels directly into the grid, either the panels would fry or the grid would.

And the same goes for batteries. So, if you were to supply energy to the grid, then DC needs to change to AC to fit with the rest of the system, which isn’t too hard to do, but that’s not the end of AC/DC headaches. When more solar is fed into the grid, we run into a surprisingly mechanical problem.

Traditional generators need to keep turning at a constant rate, keeping the power supply stable. But here’s the thing: they are physically turning. And that helps because moving objects have inertia, meaning that unless something outside stops it, it’ll keep going.

So if something happens at the power plant, and there isn’t steam to push the generator anymore, it doesn’t just stop. It keeps spinning. It’ll be, like, a few seconds before there are any noticeable effects, and that’s enough time for a power plant to adjust how much it’s burning or call for backup from elsewhere if there’s a problem.

So, this inertia helps keep the grid in sync. It makes it so that if there are problems, there isn’t a big cascade of, like, sudden power shutoffs everywhere. But, generally, the devices that turn DC into AC are not mechanical.

They’re electronic. So, there’s no inertia there to help smooth out the temporary blips. The more our electricity comes from solar panels and batteries, the more systems need to be put in place that actively monitor electricity from all corners of the grid to make sure momentary hiccups don’t cause that cascade of problems.

All of these changes mean that if we keep getting more electricity from renewable resources, parts of the grid need to become more interconnected and self-reliant. They need to be more stable and more flexible and have the ability to store energy for themselves and share it freely. They all need to monitor one another without any system stepping on another’s toes.

Like I said, this is not simple. But in the year 2000, the National Academy of Engineers rated the development of global electrical grids as the greatest engineering achievement of the twentieth century. Perhaps adapting to a changing world with changing energy sources will be one of the greatest achievements of the twenty-first.

And if you would like to keep changing the world for the better you might want to check out today’s sponsor WREN. They are a website with a monthly subscription that helps to fund projects to combat the climate crisis. Wren searches around the globe for promising projects, getting data on the ground to track their impact over time.

Like one of their projects seeks to help prevent wildfires in California by removing dead and flammable trees and turning the tree biomass into biochar. Over the long term we need governments to fund these projects, but we can start by crowdfunding them. And as a bonus, we’ve partnered with Wren to protect an extra ten acres of rainforest for the first 100 people who sign up using our link in the description!

And as always, thanks for supporting SciShow. [♪ OUTRO]