On the longer term, it's a bit more daunting.
Longer term meaning now to the year 2100.
Things change naturally in that amount of time.
The fact that we have to come up with some
new energy supply by the year 2100 doesn't sound all that frightening.
It sounds like an interesting challenge.
The problem is that if
you use a scenario predictor
like the Kaya identity module that you've played with, and ask how much
carbon-free energy would it take by the year 2100 to continue
growth as we have been growing and yet not melt down the climate,
it turns out that we have to come up with something like 20 terawatts of
energy by the year 2100.
For comparison, we are generating about 13 terawatts of energy today,
not carbon free. This 20 terawatts has to be carbon free.
And it turns out that most of these things that make up wedges
you couldn't possibly scale them up to come up with this much energy.
If you were going to do it using nuclear power,
for example, you'd have to build a
couple of power plants a week for the next 100 years.
You would make thousands of nuclear power plants.
You just can't scale it up.
And so, looking for ideas that could scale up to this kind of carbon
free energy is something of a challenge,
but I've heard some really cool ideas discussed.
One of them that I like is to put solar cells on the moon.
You could also have solar cells in orbit around the Earth,
but then you'd have to lift the solar cells out of Earth's gravity.
Whereas, if you could manufacture them on the
moon you could make them out of lunar soil.
And so you wouldn't necessarily have to bring all the
mass of those solar panels up to the moon.
Of course, there's no clouds on the moon, there's no dust blowing around,
so it would be a perfect environment for capturing sunlight.
And the question is getting the energy back to earth.
Which could be done, by using microwave radiation,
beaming energy it back to Earth.
It's not as inefficient as you might think.
Maybe half of the energy that gets sent here could be collected there.
And this technology, it's claimed, could scale up to
that amount of energy by the end of the century.
It would be a big project. But, we have decades to do it.
Another cool idea I heard was high altitude windmills.
Windmills at the ground are limited in their power by the intensity of the wind.
But if you get up into the jet stream, the wind is blowing much faster.
If you get too high up, the air gets too thin and then it loses its ability
to turn a propeller, so there's an
optimum altitude where the power density is the highest.
You could build windmills that would fly like like giant bat kites,
tethered to the ground by a conducting cable,
which would would harvest energy from the jet stream.
And this, it is claimed, could also scale up.
A third option is less less exotic, but solar thermal
energy is also said to be scalable. This is where you use
some a focusing set of mirrors to concentrate
the sunlight on a little pipe of water where you generate steam.
And then you send the steam to a turbine to generate electricity, just
the same as you would if you had a coal power plant instead.
On the time frames of the next century
we have a bold new challenge that we have
to rise to.