Say you wanted to power the entire Earth  with solar power.

I estimate you would need   around 112,000 square kilometers of at least  moderately-efficient photovoltaic panels. If that sounds like a lot, that’s because it  is, but it’s also not.

Because those panels   could also all fit in just a little  more than 1% of the Saharan desert. And with the falling cost of solar panels,   it could be done waaaay more cheaply than making  the same amount of power with nuclear fuel. But like we talked about last time, in episode 3,  there’s a big problem with relying on renewable   resources like solar and wind: What happens  to our electricity when the sun goes down?

Sometimes the rotation of the  Earth can be a real bummer. Another problem? We need reliable ways  to store and transmit electricity,   so that it’s available when and where we need it.

And that is going to require a lot  more technology and a lot more space. Hi hi! I’m M Jackson, and this is  Crash Course Climate and Energy. [INTRO] Electricity rules our lives.

We use it from the moment we wake up and check  our phones, when we cook, when we work, wind down,   when we watch YouTube videos, all the way to the  end of the day when we switch off the lights…   and watch more YouTube. And  then eventually go to sleep. Electricity won this MVP status thanks  to its versatility as an energy carrier.

As tiny particles called electrons flow  within conductive materials — think copper,   aluminum, gold, or really any metal — they  push energy from one place to another. And that energy can be used to  do anything you could dream of,   or at least, design for. It can heat your home,   it can heat your takeout.

It can even  help power those agricultural processes   that lead to your takeout, and manufacture  the plastic container your takeout comes in. So, decarbonizing electricity could go a long  way to decarbonizing many adjacent industries,   like construction, agriculture, transportation. But like you can probably guess by this  point, that’s easier said than done.

Right now, all of our homes and industries  are connected to their electricity supply by   a vast electric grid. Last time, we compared  that electric grid to a bucket of water. Imagine this time the bucket is the  grid, and the electricity is the water.   Power plants put water into the bucket, and then,   when you flip the lights on, that water  flows through a hose to wherever you are.

Crucially, the utilities companies are the  bucket managers: It’s their job to control   the flow of electricity in and out of the bucket  and make sure it stays full throughout the day. Traditionally, power plants that use fossil  fuels have produced electricity on-demand,   to effectively pump water back into the  bucket to replace whatever is used up. But as we lean more on renewable resources like  wind and solar, we won’t have that flexibility.  We don't get to pick when the sun shines  or when the wind blows.

And that can lead   to overproduction. Basically, on a  really sunny or really windy day,   so much water could be poured into the bucket that  it could overflow and damage the whole system. To avoid this, utility companies  do something called curtailment,   where they selectively switch off solar panels  or wind turbines at their most productive times.

If you’ve ever noticed a wind turbine not  spinning on a pretty windy day and wondered why…   Well, there’s a good chance that’s why. Let’s head to the Thought Bubble. The amount of electricity a neighborhood  uses varies during the day, depending on   people’s habits.

And as much as we like to  feel unique, we really are habitual creatures. In the morning, you and your neighbors  get up, turn the lights on, make coffee,   watch YouTube videos. So the load on  the electric grid gradually ramps up.

After that, things tend to stay pretty constant  during the day, because you’re either gone,   or because you’re working at home with the  same lights and same devices drawing power. But then, comes evening. People are coming home, it’s getting dark,   so you’re turning on more lights around  the house, cooking food, playing music,   chilling in front of the TV.

So, the load on  the grid peaks to its highest level of the day. Then, as everyone goes to bed, electricity  usage tails off to its lowest levels. But this curve of “rise, flat, peak, and  drop” changes when you add solar panels.

Panels produce most of their  electricity during the day,   so they easily meet the  demand of the mid-day plateau. In fact, the electric grid is being asked to  supply less power than what’s being produced,   so wind and solar power plants may even  switch off to avoid overproduction. But then comes evening…and it’s like one  minute you’re jogging at a comfortable pace,   and the next you’re sprinting full speed away  from a bear… or, towards an ice cream truck.

Peak demand happens right when the sun  goes down. So, good night, solar power. The baseload fossil fuel and nuclear  power plants suddenly have to step   in to supply all the electricity, ramping up  production very quickly to pick up the slack.

This pattern of midday sag and steep evening  incline has a name: the Duck Curve —because   if you squint and tilt your head to  the side, it kinda looks like a duck?! Look, we don’t make the names here. Thanks, Thought Bubble!

As cute as it sounds, the Duck Curve  spells trouble for the electricity grid. It’s really inefficient and  definitely not economical   for power plants to keep switching off  and then ramping up supply so quickly. That doesn’t mean solar panels are a  bad idea—they’re still carbon-free,   renewable energy!

But the way we do  electricity just wasn’t made for them. Now, one way to get around this is to change  our habits. That’s called load shifting.

Basically, we could start using most of our  electricity when it’s cheapest to generate. That could mean running the washing machine in the   middle of the night when there’s less  demand on the grid. Or it could mean   switching on an electric heater in the  day when solar power is most plentiful.

Those individual changes add up! But, as we  talked about before and we’ll talk about again,   tackling climate change isn’t just  about you; it’s about collaboration. And even if everybody did midnight laundry,   that wouldn’t be enough to  completely flatten the Duck Curve.

Plus, what about when you really need to binge  a nature show during peak evening hours? Or, at any time of the day or night,  when a hospital needs electricity   to perform surgeries, take x-rays,  keep vital sign monitors running? For that, there’s another solution: We  could level out the Duck Curve by storing   electricity when it’s made in excess, and  dishing it out when we need it the most.

For example, any extra electricity  solar panels make during the day   could be stored and then used in the evening  so power plants don’t have to work as hard. And there are already multiple  ways we could make this happen. First, you’ve got electrochemical  storage, a.k.a. your everyday battery.

Batteries contain charged particles.  And when you plug in your phone,   those particles go from one end of the battery to  the other and hang out there until you need them. Then, when you unplug your phone and  start scrolling through cat photos,   the particles release energy by whipping  back to the other side of the battery,   generating an electric current as they go. Batteries are fast and easy to charge,  they’re relatively safe and portable,   and they can hold their  energy for a very long time.

The trouble is, electrochemical batteries  often use metals that are rare on Earth,   so assembling enough of them to store  electricity for an entire grid would be costly. To extract these rare Earth minerals, you  would need big mining operations that would   damage the environment. Which is kind of  the opposite of what we’re going for here.

So instead, excess electrical energy  could be stored by chemical means. We’d use extra electricity to split  water molecules into hydrogen and oxygen,   in a process called electrolysis.  Then, when we needed electricity later,   we could generate it using a hydrogen fuel cell. Here, the hydrogen enter a chamber with  a special membrane.

The membrane lets part   of the hydrogen atoms pass through:  their positively-charged protons.   But the negatively-charged electrons have  to take a different path to the other   end of the fuel cell. And that stream of  electrons creates an electric current. The only waste product here is water,  so this is a carbon-free option that   uses and regenerates one of the  Earth’s most abundant resources.

The catch? Hydrogen is a really lightweight gas,  meaning, its molecules are quite spread out. So, it takes up a lot of space and is difficult  to compress into small containers for storage.

So, there’s a third option that’s carbon-free,   and it deals with regular, un-split  water: it’s called mechanical energy. When there’s electricity to spare,   water is pumped to the top of a big  hill and kept there in a reservoir. Then, when the electricity is needed again,   water is released to turn a turbine  and generate power on-demand.

This is basically the same technology  as a hydroelectric dam: You just add   an uphill pump. So, this is something we  could actually develop relatively easily. But it’s not the most efficient technology.

You need a huge space and at least  one big hill for a reservoir,   if you’re going to rely on  gravity alone. Sorry, Kansas. So, the last option is thermal energy storage.

Here, excess electricity is used  to heat a material with a high   boiling point, like molten salt. Some salts don’t melt until they   reach several hundred degrees Celsius, so  they’re really not something you want to   put on your fries… because your food would  immediately catch explosion, pardon, fire.   But these salts are a good heat source. So, when the demand for electricity increases,  the heat from the salt can be transferred to   water to make steam, turn turbines,  and generate the electricity we need.

It seems simple, and existing fossil  fuel plants could even be repurposed   to contain thermal storage and steam generators. Except, molten salt also has a bad habit of  corroding everything it touches. And fighting   that is a constant, expensive battle, so is  keeping the salt hot enough to stay liquid,   especially if you want to do  that with renewable energy.

As great as they are, renewable energy  sources like wind or solar just don’t   have a high energy density  compared to fossil fuels. In other words, to generate the same amount  of energy as a fossil fuel power plant using   solar panels, you’d need anywhere  from 25 to 2000 times as much space. Compared to fossil fuels, all  these storage options can have   a high Green Premium, or upfront cost difference.

So, there is one more path: We start sharing  buckets across locations, even time zones.  In other words, instead of saving  spare electricity for when we need it,   we could transmit that electricity to  somewhere that needs it right now. Connecting grids over wider areas would allow  utility companies to deliver electricity more   efficiently and more equitably. And it could  overcome some of the limitations with renewable   energy: One region that’s super sunny could  send power to a city that’s a bit more overcast. [Phone rings] This is Seattle… Hey Phoenix!

Unfortunately, this is hard with  the grids we have at the moment. Our buckets only serve certain  regions. Unless you happen to   be near Indianapolis right now, my region’s  electricity bucket, not connected to yours.

But this is starting to change! For instance, the TransWest Express in the US  (say that three times fast) is planning to take   wind power from Wyoming and deliver it all the way  to California, over a thousand kilometers away. Big regional projects like this will  help each state reduce its emissions,   while requiring fewer solar panels and wind  turbines than if each state powered itself alone.

You know what they say: Team  work makes the dream work! In the end, decarbonizing electricity  won’t have a single solution,   like filling part of the Sahara with solar panels. I mean, if transmitting electricity  between states is hard right now,   imagine the challenge of transmitting  electricity from one part of Africa   to the rest of the world!

And that’s  not even mentioning how we’d store it. So obviously, collaboration will be key here. Some regions might work on advancing batteries,   while others might focus on connecting grids.  And you — you might contribute to research,   or policy, or tech, that furthers the  conversation in areas you’re interested in.

Figuring out the best ways to  store and transmit electricity   won’t be easy. But the payoffs will be huge. Because whatever strategy we come up  with won’t just help us make carbon-free   electricity.

The advancements will affect  all other big, carbon-emitting sectors,   like transportation or heating our homes. We’ll get into that next time. Special thanks to Harry Brisson, this episode’s  combination bucket manager, wind turbine wrangler,   and duck curve illustrator.

You really  held it down this episode, Harry.   Thanks for keeping the lights on and the buckets from  overflowing — and for supporting us on Patreon. Crash Course Climate and Energy is produced by  Complexly with support provided by Breakthrough   Energy and Gates Ventures. This episode  was filmed at the Castle Geraghty Studio   and was made with the help of all these  nice people.

If you want to help keep   Crash Course free for everyone, forever,  you can join our community on Patreon.