
‘Solar’ jet fuel made out of air - Libertatea
http://www.rsc.org/chemistryworld/2014/05/solar-jet-fuel-made-out-thin-air
======
dkokelley
For comparison, global jet fuel consumption for major airlines in 2013 was
over 60 billion liters.
([http://www.transtats.bts.gov/fuel.asp](http://www.transtats.bts.gov/fuel.asp))

My envelope calculations show that we would need 8,334 km^2 (roughly 3% of
Nevada) of plant space at 20k liters/day to roughly cover global jet fuel
consumption. (I welcome sanity checks on this math.) That's actually an
encouraging and apparently achievable number.

~~~
gmarceau
Jet fuel sells for $2.88 per gallon (76 cents per liter),
[http://www.indexmundi.com/commodities/?commodity=jet-
fuel](http://www.indexmundi.com/commodities/?commodity=jet-fuel)

If the entire world worth of jet fuel was obtained from Nevada, it would
inject around 4 billion dollar per year into Nevada's economy, or around $1500
per capita every year. I can imagine them choosing the money over the land.

~~~
theorique
I'm finding a daily consumption of 200M gallons, or 73B gallons annually. This
would work out to a global consumption of about $220B worth of jet fuel, not
$4B.

~~~
dkokelley
Where are you finding that 73B gallons/year figure? That's more than 4x the
number I found at
[http://www.transtats.bts.gov/fuel.asp](http://www.transtats.bts.gov/fuel.asp)

~~~
theorique
That was from the indexmundi site:

[http://www.indexmundi.com/energy.aspx?product=jet-
fuel&graph...](http://www.indexmundi.com/energy.aspx?product=jet-
fuel&graph=consumption)

I think the difference comes from global vs US numbers.

------
jboggan
Sweet. Venus has a very dense CO2 atmosphere with negligible amounts of oxygen
and about twice the insolation of Earth. Let's set up some high altitude
blimps above the cloud layers as floating solar syngas factories. I'm a little
busy right now but in 10 years when Musk has the launch vehicles figured out I
think we should do it.

Edit: I didn't type it because I thought it was obvious, but this would be
producing fuel for rockets and other vehicles operating in exploration, not
for bringing back to Earth to put in your car.

~~~
nostromo
I wouldn't look to Musk to create cheap and environmentally friendly
hydrocarbon fuels. ;) At least not until every house already has an outlet for
their Tesla.

~~~
jboggan
I hope Musk would have better business sense than lifting hydrocarbons from
Venus back to Earth in order to burn them in cars! This would be for fueling
transport and exploration of the solar system, it's always cheaper to make it
there than bring it with you.

------
jbert
This is the 2nd part of the "we need lots of clean/carbon free energy" \- a
way of storing and transporting it.

Chemical fuels have a great energy density. Problem is, they dump carbon into
the air when you burn them (and also basic pollutants).

So we just need:

1) fusion or similar "lots of 'free' energy"

2) a process like this to soak up that energy + CO2 + H2O and emit nice energy
dense hydrocarbons

3) decent catalytic convertor/filter tech (we're pretty good on this at the
moment when we want to spend the money?)

 _then_ we've got a long-term energy future.

~~~
Dn_Ab
_Chemical fuels have a great energy density. Problem is, they dump carbon into
the air when you burn them (and also basic pollutants)_

Exactly!

> So we just need: 1) fusion or similar "lots of 'free' energy"

Utilizing geo, hydro and solar (carpeting them in inhospitable areas) and
fission is enough. Fission is particularly effective, the energy yield per kg
of fuel for _fusion_ is only 4x that of fission. Between less wasteful
alternate reactor designs and extracting fuel from the ocean, if we start
figuring things out now, things will be fine.

> 2) a process like this to soak up that energy + CO2 + H2O and emit nice
> energy dense hydrocarbons

This is well studied by the US Navy and others. It's especially cost effective
when drawn from the ocean. Wikiterms: 'sabatier reaction', 'power to gas',
'carbon neutral fuel'.

> then we've got a long-term energy future.

We're still going to have to act quickly, before the energy (and resources)
required to initiate this industry is more than could be had with the then
current reserves. A true debt. Thus squandering the selfless sacrifice made by
dinosaurs many kilomillennia ago in order that we at least could bootstrap a
space faring civilization.

~~~
XorNot
It's a hilariously under-appreciated fact that the US military is on track to
be one of the biggest investors in green power and fuels, as both are major
logistics hassles and strategic concerns for it.

The USAF would _love_ to not have to worry about the long-term availability of
fuel oil, and just depend on a desert array of concentrators somewhere in the
US.

~~~
dredmorbius
The military, and most specifically the US Navy, have lead fuel innovations
over the past 150 years.

Wind -> coal (1850s) -> Oil (1910s/1920s) -> Nuclear (1950s)

And now hybrid and synthetic fuels.

Much of the more interesting peak-oil / collapse literature comes from
military organizations, including in the US, Germany, and UK.

------
Gravityloss
It's remarkably stupid to burn coal in a power plant and then in the
neighboring lot trying to take the carbon from very diluted (less than one
part per thousand) carbon dioxide in the air.

If these solar plants just fed the electricity into a well built power grid,
the coal plants could be turned off and a huge amount of CO2 would be left
unemitted.

Coal is unbeatable as a carbon storage method, and what's best, it's _free_ as
it already is in the ground, we just have to leave it there!

I'm sorry to say, but most of these energy schemes just make many people who
understand anything about power generation cry.

It's like to an IT guy, some client suggested you ran their enterprise
databases on an Arduino over Bluetooth, because they heard it's a cool new
thing.

~~~
icegreentea
The point is to make more super energy dense liquid fuel for mobile
applications that require that density. IE, airplanes. Thats the reason why
the are seeking to make jet fuel specifically. The energy density requirements
for flying makes the current headaches over EV cars look like a joke.

The scientists and engineers have no illusions that this method will be used
for general energy generation. This is for a niche application. And the
'sequester carbon from the air' part? All they care about is that its carbon
neutral.

And honestly, it's pretty smart. Pretty much a guarantee way to get defense
funding all around the world.

~~~
Gravityloss
You would have a better climate impact by just creating coal replacing grid
electricity with the panels, and flying the airplanes on normal kerosene.

~~~
dredmorbius
"Normal kerosene" is a nonrenewable resource which will be running out by and
by. Hence the interest in synthesis.

------
zackmorris
Converting sunlight to heat is trivial, at 1368 watts per square meter. The
problem has always been energy storage. A single acre is 4047 square meters,
or 5.54 MW (7429 hp). As a rule of thumb, I generally divide the area by 3
because collectors are usually arranged in troughs, slightly spaced for low
sun angles. Still, thinking in terms of 1 MW of heat per acre, or 2000 hp,
puts things in perspective. Dams and power plants are usually in the GW range,
so it would take 33x33 acres to capture 1 GW of heat. Since an acre is about
209 feet on a side, that's between 1 and 2 square miles. At the quoted 1.73%
efficiency, we'd have to multiply by the inverse, 58, to convert from heat to
fuel. So we're talking 50-100 square miles to create the output of a GW power
plant for say 8 hours of daylight. Figure a 200 square mile plant to withdraw
1 GW worth of fuel continuously. However, we get down to the 20-40 square mile
range if they can get the efficiency to 10%. Of course this all ignores the
combustion efficiency which is probably only about 25% so we have to multiply
by a factor of 4 again.

Probably a more practical way to store energy, and in my mind the most likely
way to power vehicles, is compressed air at 300-700 atmospheres, which is
within the same order of magnitude energy/mass density as batteries, depending
on the storage tank:

[https://en.wikipedia.org/wiki/Energy_density](https://en.wikipedia.org/wiki/Energy_density)

A solar plant can be built on top of an empty natural gas well and store
energy in compressed air underground. Another possibility is compressed air in
large bags at the bottom of the ocean, that would displace less water than a
dam since the height difference can be several thousand feet (pumping water
uphill is not very effective due to the elevation required). We’ll also never
have enough batteries or supercapacitors to store that much energy.

I wish I had money to invest in fiberglass or carbon fiber wrapped storage
tanks and micro turbines/pistons that convert the energy in compressed air to
rotational energy. I think we’ll be using them instead of something more
exotic like magnetic bearing flywheels, and future electric cars will have a
small natural gas/hydrogen turbine that tops off an air tank that will take
the car 10 or 20 miles without having to tap into batteries. Also, refilling
air tanks at a fueling station can happen almost instantly, at least as fast
as filling up with gasoline.

Still, I think making hydrocarbons is an exciting development for distributed
generation, where people are only making a few liters of fuel a day from water
basically. I imagine that it might be more efficient to make propane also, and
this is a little off topic but propane engines are much easier to build/more
efficient because they don’t have carburetors or fuel injection. I’m honestly
surprised the world went with gasoline and diesel, although it was probably
for safety reasons.

~~~
DaniFong
Hi Zack,

My company, LightSail Energy, is developing precisely this technology.

www.lightsail.com

We're also developing the world's lowest cost pressure vessels to store the
air.

I wish you had the money to invest in us too ;-)

~~~
dredmorbius
I'm curious what the magnitude of thermal energy loss without capture and re-
injection of heat loss is with CAES.

I've seen repeated mention of this in various sources, but no explicit
quantification.

~~~
DaniFong
It's hard to generate a strict apples to apples comparison -- not only do the
numbers depend on operating parameters, but pure adiabatic operation causes
both very high temperatures, imposing strict materials constraints and very
difficult heat exchange and heat storage challenges, and very low
temperatures, causing icing.

This means no working pure compressed air energy storage tech is in existence
today -- a couple exist which add heat via combustion, one product used to
exist which used an electric heater to keep a heat store warm. Both are
thermodynamically non-ideal.

Based on pure theory, however, running two stages of compression to 200 bar
(14.1:1 each), running perfectly adiabatically during compression and
expansion, temperatures would reach to about 600 C during compression. If one
didn't recover the heat of compression, and let the temperature of the
compressed air drop to ambient, the temperature upon expansion would get to
about -170 C. Pure thermal efficiency would be about 34%.

The results are so extreme / bad that one would choose a whole separate set of
parameters and compromises. But that should show you the power of direct
contact heat exchange.

~~~
dredmorbius
Thanks.

I've seen some discussion of CAES using former natural gas wells for storage.
I don't know the scale of operations there, but it could be large (meaning
that relatively small amounts of energy would be stored or extracted at any
given point in time.

Rock also serves as a pretty good insulator (R5 as I understand, and there's a
lot of it), which might preserve some of the heat of compression.

In your example, is 200 bar a typical pressure for CAES? I see that as about
2900 psi for the imperial units types.

~~~
DaniFong
200 bar is an inflection point in the regulatory landscape for above ground
tanks. A sweet spot. There's another sweet spot around 300 - 400 bar due to
the physics of air.

Salt caverns melt at high enough temps (above 200 C) and injecting hot air
into a methane reservoir is not terribly advisable...

~~~
dredmorbius
Took me a moment to realize you were talking CAES in salt caverns, not salt
caverns for thermal energy storage, though _that_ hadn't occurred to me either
(I don't think it's necessary).

The constraints you raise on natural-formation CAES do raise some interesting
challenges (or Hollywood movie plots).

------
danielweber
I post about LANL's "Green Freedom" every once in a (long) while, so I really
enjoy more articles about manufacturing liquid fuels from atmospheric CO2.

One issue I've found is that it can be expensive to concentrate CO2 from the
air to feed into this process. For the first version, I would recommend
putting it on the smokestack of a coal or natural gas plant, which is putting
out majority-CO2. It's not getting us carbon neutral fuel, but it gets us
double-use out of each CO2 molecule, and it makes the first version much
easier to build.

------
Tloewald
$18.25/year/square meter at $2.50 per liter of kerosene. The US currently
generates 0.6kg/year/square meter of cereal -- and that's on fertile
(irrigated...) land.

So, assuming that most of the plant is low maintenance and not too expensive
to manufacture it's not that bad. Certainly I don't think that turning corn
into fuel is anywhere near as efficient.

~~~
masklinn
Where do you get the $2.5 figure? According to
[http://www.transtats.bts.gov/fuel.asp](http://www.transtats.bts.gov/fuel.asp),
in 2013 the average was $3/gal of kerosene, or 0.8$/liter.

~~~
Tloewald
I got the figure from Amazon (having guess $4/gallon initially) but am happy
to stand corrected. Even so, far more efficient than corn -> ethanol.

------
z3phyr
This is one of the concepts I actually thought about, when I was in middle
school. Really excited about it again :)

One thing I want to ask right now, Will the ratio between the input carbon
consumption and the carbon emission + residue remain the same in such a
process?

~~~
eloff
How could it not? It's not a nuclear process so carbon in must equal carbon
out. All carbon is sourced from the atmosphere and returns to the same. There
may be different ratios of carbon compounds though, e.g. less co2 out than in
and more other types of carbon compounds out.

~~~
z3phyr
It is highly likely that CO will be a possible residue. Could it be considered
a lot more harmful in a different way?

~~~
dredmorbius
In unconfined spaces, CO tends to dissipate. It's fairly reactive (binding
with O2 to form CO2) and will be pretty short-lived. Not something to worry
about.

[https://en.wikipedia.org/wiki/Carbon_monoxide](https://en.wikipedia.org/wiki/Carbon_monoxide)

------
sespindola
some physicists at Sandia labs have been working on a similar technology: the
counter rotating ring receiver reactor recuperator, or CR5[1]. Though it seems
to be a long way from reaching the necessary efficiency for it to be
comercially viable.

It was festured in Daniel Suarez's Freedom, as the main fuel generator for a
native self-sustaining community.

[1]
[https://share.sandia.gov/news/resources/releases/2007/sunshi...](https://share.sandia.gov/news/resources/releases/2007/sunshine.html)

------
ndonnellan
Now we just need to figure out how to keep a quartz window from shattering
after cycling from ambient to 1500C ...every time a cloud passes.

~~~
durkie
why? it seems like it'd be one of the best materials out there - it has a
super low coefficient of thermal expansion, especially in comparison to many
other materials.

~~~
ndonnellan
Oh it absolutely is, but if the chamber is under pressure (which they don't
mention, but probably affects yield), there still will be a lot of stress.
Syngas solar receivers are one of the unicorns of the solar industry.

~~~
durkie
interesting -- i wonder if they could have a 2 lens system where your overall
system would look like:

sun / outer lens / pressurized gas / quartz lens from diagram / reactor

you could adjust the pressurized gas chamber pressure to match that of the
reactor so that you're subjecting the quartz lens to a net zero bending
moment/tension. ideally you could then make the outer lens out of something
tougher than quartz and it wouldn't need as much high temperature strength
since it's farther away from the reactor.

------
tim333
Hope it works. Another interesting approach is Algenol's using algae to make
ethanol - they've been saying it will be up an running any moment for a while
now but you never know
([https://en.wikipedia.org/wiki/Algenol](https://en.wikipedia.org/wiki/Algenol))

------
dia80
Articles claims 20k litres per day from 1km sq. solar farm maybe possible in
the future.

At current (retail) prices that's about 10,000GBP per day or 3.5M GBP per
year. Doesn't sound like a lot to run a 1km sq. facility...

~~~
notahacker
Ironically, the areas with an abundance of sun and low-value undeveloped land
near major aviation hubs tend to be in petro-states...

~~~
NegativeK
Sounds like a match made in heaven.

------
phorese
Anyone know what the "purge gas" is in the O2 half cycle?

------
oDot
Where will the water come from?

------
dredmorbius
The US Naval Research Laboratory's electrically-powered fuel from seawater
research appears vastly more viable than this project. It's been covered
previously at HN.

Briefly:

• It creates aviation-quality fuel (long-chain liquid hydrocarbons equivalent
to kerosene or diesel fuel, longer than those in gasoline) from electricity,
hydrogen electrolyzed from seawater, and CO2 present at 140x atmospheric
concentrations in seawater in both dissolved (2-3%) and bound (97-98%) forms
as carbonate and biocarbonate.

• It utilizes two very-well established and understood principles:
electrolysis and Fischer-Tropsch process fuel synthesis.

• The novel aspect is also relatively conservative: extraction of CO2 at
industrial levels from water via partial vacuum and pH changes induced largely
via electrolysis.

• Efficiency looks to be reasonable and largely governed by electrolysis at
60% in terms of net recoverable energy from H2. Even if operational efficiency
is only 10% of this it's still 3.5x more efficient than the method described
in the article here.

• Scale of operations envisioned is significant at 100,000 gallons/day.
Scaling this to national levels of present petroleum consumption strikes me as
plausible, though not trivial or inexpensive. Capital costs are not
incommensurate with existing and projected petroleum capex spends (trillions
of dollars), and may provide greater return in terms of net energy supply.

• Plant requirements are, as fuel synthesis schemes go, profoundly modest.
Rather than tens or hundreds of millions of hectares envisioned for biofuel
schemes (along with freshwater and ag infrastructure requirements), a volume
of roughly 10m x 4.5km x 4.5 km might provide US national liquid fuel needs.
At envisioned Navy deployment levels, the plant would occupy a modest
industrial site or possibly a shipboard or floating platform (though not fit
within existing warship envelopes while preserving combat operations
capabilities).

• Power requirements at 100kgal/day are ~240 MW (roughly an aircraft carrier's
reactor output). At national scale, about 2 TW, or equivalent to a solar
collector surface of roughly 6,700 km^2 (82 km on a side).

• The process should be highly amenable to utilizing surplus generating
capacity on an intermittent basis to create fuel. It could be used for both
electrical generation storage or for large-scale fuel synthesis.

• The technology isn't inherently large-scale. Smaller modular installations,
or large centralized ones should, from an engineering perspective, be roughly
equally viable, as contrasted, say, with nuclear technologies which are
inherently centralized for engineering, safety, security, and operational
reasons.

More: [http://redd.it/22k71x](http://redd.it/22k71x)

