- Okay, so solar power

is going through something incredible right now.

Take a look at this chart.

The world went from 1 gigawatt of solar capacity

in the year 2000 to 1 terawatt in 2022.

That's a 1000% increase.

But then in only 3 years,

we're about to double that, to 2 terawatts of capacity.

Now to put that into perspective,

2 terawatts of power could run 92 million US households.

And in 2025, this trend is still accelerating.

Now that's thanks to two big factors.

First, solar power is now cheaper than ever to produce.

The cost has dropped more than 99% since 1970,

making it one of the cheapest forms of energy.

And second, advances in battery technology mean we can store

that energy for when we use it the most, in the evening.

So, this all sounds great, right?

Well, there's a problem with all this new solar capacity.

Where are we going to put all these solar panels?

Now here in California,

the obvious choice might be in the sunny Central Valley,

because there's plenty of flat land there.

But it's also a huge farming hub.

25% of the nation's food is grown here.

You can't just cover it all with solar panels.

So how do we balance the need for clean energy?

With the ability to still grow food?

And it turns out,

the answer is actually taking shape right here,

behind these almond orchards in California.

And this idea could answer California's prayers

for more water.

Now it's a solution so simple and obvious

that people have been talking about this in California

for decades.

So, I came out to the Central Valley

to get a closer look at the future of solar power.

(bright music)

Now before we get into solar panels,

let me take you to where this project really begins.

Here in the Sierra Nevada mountains.

This is where most of California gets its water.

Every spring, that mountain snow melts into reservoirs

and travels through thousands of miles of man-made canals

to reach our homes and California farms.

But as water flows through the hot Central Valley,

we lose billions of gallons of water to evaporation.

That's a big problem in California,

because water is a precious resource here.

Okay, so here's where those solar panels come in.

This is Project Nexus, and its concept is pretty simple.

Cover the canals with solar panels

so that we can both generate electricity

and protect the water from evaporating in the sun.

Now you might have seen a similar idea in parking lots,

like solar canopies over our cars that keep them

from baking in the sun.

- We estimated that if we covered all 4,000 miles

of California's major canals,

we could save up to 63 billion gallons of water.

- This is Brandi McKuin.

She's a UC Merced scientist on the Project Nexus team,

and it was her research paper

that set this whole project into motion.

For years, people have talked

about putting solar over water to help with evaporation.

And India even built

the first solar canals prototype in 2014.

- One thing I'm surprised by is how many people

that have told me they had the idea for this project.

And certainly, this was not my idea.

We've learned a lot from the very first prototype in India.

But we didn't know what the social, economic,

and environmental impacts would be

if we did this at scale

across California's 4,000 miles of major canals.

So that's what we did.

We did a hydrologic simulation

and a techno-economic analysis to better understand that.

- Besides saving 63 billion gallons of water,

Brandi found that covering

all of California's man-made canals

with solar could also generate 13 gigawatts of power.

Okay, you could think of it like this.

That's enough clean energy and water for everyone

in San Francisco and San Diego combined.

The idea to use solar panels to stop evaporation

has been around for decades,

but it didn't move forward until Brandi ran a simulation.

Her paper caused a bit of a stir in California,

and a bunch of groups came together to make it a reality.

There's the Turlock Irrigation District,

who maintains the canals and delivers the water to farms.

The California Department of Water,

who funded the project

and is very interested in saving water.

There's Solar Aquagrid,

the company that basically spearheaded the whole project,

secured funding, and brought everyone together

to make it a reality.

And then there's Brandi and UC Merced,

who continue to study and analyze the project

to make sure it's working as efficiently as possible.

Now, before covering all of California's canals with solar,

we need to test it out first.

Right now, Project Nexus consists

of two different prototypes.

There's the narrow span

that covers a 30-foot-wide section of the canal

with two solar arrays.

And then there's the wide span,

which covers a section that's a whopping 130 feet wide.

Both are located in California's Central Valley,

a major farming hub that grows 25% of the nation's food.

Brandi's research estimates

that this project could save enough water

to irrigate 50,000 acres of farmland.

- Agriculture is a really important part of the story.

Around us are all these almond trees,

and this is some of the most productive farmland

in the nation.

And so, we can multitask,

save water to produce more food

and generate electricity that can be locally used

at the same time.

- Solar over canals provides an alternative,

saving water for farms without using up precious land.

You can think of it like,

if you were installing solar panels for your home,

you wouldn't put them in the backyard,

you'd put them on your house.

The same is true in California.

There's an already built environment,

like these irrigation canals,

and we can add solar to these

so that we're not displacing plants and animals,

like the desert tortoise here,

or using up valuable farmland.

Okay, so why don't we see more

of these dual-land use solar projects?

Well, part of it is cost.

Those iconic ground-level solar farms are cheaper

and easier to install.

Like let's say you wanted

to cover every building in San Francisco with solar.

First, you'd have to get everyone's permission,

and it's a much trickier engineering challenge.

Each building is different

and requires custom installation.

You also have to consider the shade from nearby buildings.

Solar canals, on the other hand,

they might require more customization

than typical solar farms,

but you can install a lot of panels for each project,

without taking up any land.

Covering all of California's canals

with solar doesn't just magically solve all

of our energy problems,

but it shows how we can be creative

with the way we use solar,

and it isn't the only innovative idea that people have.

Some farms are experimenting with agrivoltaics.

This is where solar panels are raised above crops

so that the shade helps plants retain moisture

and reduce heat stress on the plants.

In hot, dry climates, this can make a huge difference.

This works really well for shade-tolerant crops

like root vegetables, berries, and leafy greens.

In fact, China has become a global leader in this approach,

with large-scale solar farms built over fields

of goji berries.

Another approach is floating solar,

basically placing the panels directly on the water

in reservoirs and lakes.

And the principle is similar.

Shade reduces evaporation and keeps the water cooler,

which also can improve the amount of electricity

that the panels produce.

Now, when solar panels heat up,

they tend to become less efficient,

like our phones or computers when they heat up

and they don't work properly.

That cooler water under the panels keeps

their temperatures in check.

Now, all of these approaches come

with their own design challenges.

You might notice that Project Nexus panels

are built higher off the water than the ones in India.

Ideally, the panels would be as close as possible

to the canal water to stop evaporation

and keep the panels cool.

But the Water District needs to regularly clean out silt,

algae, and other vegetation from the water.

But the team is now exploring a new design.

- There's an exciting prototype that we will test here.

It's going to be a much lower profile

and it's retractable design

so they can push the panels

in whenever they need to access the canal

for maintenance and cleaning.

So, we're really excited about that.

But I think that just the fact that this project exists,

that is kind of driving innovation in that space.

- Solar panels are also surprisingly durable

and typically last somewhere between 30 and 35 years.

These panels are designed to withstand 1-inch hail

at 50 miles per hour winds.

Now Project Nexus isn't the only solar over canal project.

For example, in Arizona,

the Gila River Indian community

has installed solar canopies over one of their canals.

Thousands of years ago,

indigenous communities in this region

had built a canal system for farming.

But when Europeans arrived in the 1800s,

they diverted the river's water away from these communities.

It wasn't until the 1930s

that tribes regained some access through the construction

of a new reservoir.

- For the world to see that a tribal nation can do this,

and this links so beautifully to our traditions.

If this moment becomes a movement,

we're going to look back and just to see

that this is a historic time in how we address

and adapt to our changing environment.

- [Zak] With more solar canal projects up

and running in the U.S.,

engineers can troubleshoot problems

and refine their designs for different environments,

all of which advances the technology much faster.

And Brandi's team is there to see

what designs actually work the best.

On a typical canal,

the radiant heat from the sun turns the water

into water vapor,

and then the wind blows the water vapor away.

Brandi is using sensors to measure exactly

how much water is evaporating under the shade

of these solar panels.

- It sounds really simple studying shade,

but actually the amount of irradiance

that's on the water surface, there's a little bit

of light transmitted through the solar panels

and there are gaps between them.

When we're modeling something theoretical,

there's a lot of things we learn by studying them

in the real world that aren't captured in models.

- With Brandi's research,

each prototype can be refined to work even better.

Private companies have to worry about making a profit,

which makes it hard to explore ideas

that might not pay off right away.

And that's where universities like UC Merced come in.

Places where people can ask those big what-if questions

that go on to inspire industry.

- It's amazing.

I never thought in my wildest dreams

that something that was a conceptual paper

would end up being something

that we can test in the real world.

- Okay, after sweating out there in the 100-degree heat,

I can tell you firsthand,

the shade from those solar canals felt amazing.

The funny thing is, we barely think

about shade when we design and build our own communities.

Take a look at this playground slide in LA.

It has a surface temperature of 120 degrees Fahrenheit.

That's not really something you want your kids playing on.

And it isn't just hot surfaces.

On a hot, sunny day,

shade can reduce the heat load on our bodies

by a whopping 50 degrees Fahrenheit.

Check out our video that looks

at what we can do to design cooler neighborhoods.

And it's a whole lot more than just planting trees.