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Today I would like to show you how
we can produce conventional liquid hydrocarbon
fuels, such as gasoline and kerosene,
from these three ingredients, water, CO2 and solar energy.
Why is that important?
Three days ago I took the flight Zurich-San Francisco.
I flew over 5,800 miles with an Airbus 3340, which
carries 300 passengers and 50,000 gallons of kerosene,
of jet fuel.
So a back-of-the-envelope calculation is telling me that
my carbon footprint, on that particular day,
was 1.4 tons of CO2.
Now, considering that worldwide there are 50,000 flights a day
carrying 3 million passengers, it's not a surprise
that global aviation is responsible for 900
million tons CO2 per year.
Now, if we consider all transportation, including cars,
then we are talking 3.9 billion tons of CO2 per year.
This represents 14% of the anthropogenic CO2 emissions.
But today I don't want to talk about general CO2 emissions.
I want to focus on those CO2 emissions derived
from liquid fuels for transportation,
and specifically, for aviation.
And this is because there are no alternative fuels for aviation.
There is no way around jet fuel.
We are not going to fly Boeings with batteries.
So this Solve for X becomes how can we
eliminate the carbon footprint derived
from the use of liquid hydrocarbon fuels
without the need for abstaining from flying or driving?
I'm going to keep the world map and I'm
going to attach the annual solar irradiation,
this is in units of kilowatts per square meter.
And I'm going to do the following back-of-the-envelope
calculation.
The energy consumption by global transportation,
all means of transportation, is this number
that you see here, 2.8 times 10 to the 13th kilowatt hour
per year.
Now, let's assume you pick up in a region
where the annual irradiation is at least 2,000 kilowatt hour
per square meter, so anywhere in this dark orange region.
And further, let's assume that we have a technology
within a conversion efficiency of 20%.
Now, the solar area required for covering the complete energy
consumption by transportation becomes a square of 160 times
160 miles, which is drawn in scale here,
in the state of Arizona.
Now, what you see here is a photograph
of a commercial solar power plant, CSP.
Based on steam Rankine cycle, this one
is in the south of Spain.
There are many of these solar towers being
built around the world, several of them here in California.
Now, we are going to be making use
of this same solar concentrating infrastructure.
We will use the same heliostat field,
concentrate the solar radiation on top of the tower.
We will remove the boiler from the top of the tower
and we will place a solar reactor, which
we are filling with water and CO2
and producing these solar fuels.
Now, let's make a close up on the process
here inside a solar reactor.
We are talking about what is called
a solar thermochemical redox cycle.
Redox is for reduction oxidation.
Two steps.
In the first solar reduction step,
the methyloxide is thermally reduced, oxygen is set free.
In the second oxidation step, the reduced methyloxide
reacts with water to generate hydrogen, with CO2 to CO,
and the original oxidized methyloxide, which
is recycled to the first step.
So the net reaction is solar energy in, water and CO2 in,
oxygen out, and hydrogen and CO out.
This mixture is called syngas, it's
a key mixture, the precursor, for the synthesis
of liquid hydrocarbon fuels.
What you see here is the solar reactor technology
consists off a cavity with a small opening
to let in concentrated solar energy.
This cavity contains the reactive material,
it's ceria, which is in the form of RPC.
This is short for reticulated porous ceramic, a foam type
structure.
And this is the way this solar reactor operates.
Remember, two steps.
During the first solar reduction step
we introduce concentrated solar energy,
enters the cavity, undergoes multiple internal reflections,
it's absorbed.
This is the way that we deliver the high temperature processed
heat, at around 1,500 degrees Celsius.
The ceria undergoes reduction, oxygen evolves,
and exits through this outlet port here,
at the rear part of the reactor.
Once the first step is completed we
are ready to move into the second step.
By the way, the second step is slightly exothermic.
We don't need a source of energy.
So we stop the input of solar energy.
Here is the oxidation, and we bring the reactor
to 900 degrees Celsius.
This is for kinetic reasons.
We introduce the reacting gasses, water, CO2,
radially, which flow across the porous RPC,
react to generate hydrogen and CO, which
exits through the same outlet port, producing syngas.
Syngas is processed to liquid hydrocarbon fuel.
Now, we have built a four kilowatt prototype
solar reactor just to give you an idea of the dimensions.
Here the aperture is five centimeters in diameter.
And in this reactor we have measured, experimentally,
a solar-to-fuel efficiency of 2%.
Let me explain what is this efficiency.
The definition is this solar-to-fuel energy conversion
efficiency, the heating value of the fuel produced,
divided by the solar energy input.
This is the most important performance indicator
of the reactor technology, of the process.
Very directly linked to the economics.
Now, while our analysis indicates
we should be able to reach efficiencies of around 20%,
and when we do that, then a solar tower
similar to the one that you see here in this photograph,
and here you see the area that it occupies.
This solar tower should be able to produce 4,100 gallons a day
of gasoline or kerosene.
One issue still needs to be solved.
What is going to be the source of CO2?
For a true sustainable processes,
CO2 should be captured from atmospheric air.
We have developed an absorption-desorption process
based on temperature vacuum swing cycle using
amine functionalized cellulose.
And this way we can capture pure CO2.
While we are doing that we are also recapturing water
from the humidity in the air.
And this is also for dry air, because even dry air
has 10 times more water content than CO2.
To summarize, we have an absorption-desorption process
to capture CO2 and water from atmospheric air.
These are the two ingredients that we
need for the redox thermochemical cycle using
concentrated solar radiation to produce
the syngas mixture, which is further processed
using conventional catalytic processes,
to the liquid fuel hydrocarbons, gasoline, kerosene, diesel,
and these liquid fuels that we used for transportation.
Now the material cycle is perfectly closed.
This is a true sustainable process.
And I'm coming back to the first slide,
and I'm going to make a slight change in the title.
Gasoline and Kerosene from-- there you go.
Thank you.
[APPLAUSE]