Saudi Arabia has huge reserves of oil under the ground, but it also has a huge resource of solar energy and huge areas of desert above it. My calculations show that 320 square kilometers of Photovoltaic cells in this nation can produce the energy required to meet the demand for all of the world’s aviation fuel. 320 square kilometers amounts to 0.017% of the land area of Saudi Arabia.
The technologies required involve the production of methane (CH4) from CO2 and water (the Sebatier process), and the process of converting methane into liquid fuels, with further CO2 capture, according to the processes researched by the Carbon Engineering Group.
Given the abundance of solar energy in Saudi Arabia and the vast areas of desert, this nation is a wonderful candidate for leveraging this technology for a greener future. Unbeknownst to many, Saudi Arabia has the cheapest per unit cost of solar energy production in the world.
The prospect of huge solar farms in the desert also have the added benefit of cooling the local climate around these solar farms, by converting a portion of the sun’s energy into electricity and then liquid fuel for export.
Why aviation fuel anyway?
I’ve chosen to focus on aviation fuel as air travel is proving to be the most difficult case of oil consumption to replace with clean energy. Just looking at the physics of air travel can show that this is the case. Then consider that mass transport aeroplane design and engineering haven’t fundamentally changed since the 1970s (Boeing 747’s first flight was in 1970), it is hard to see how science and engineering of the aeroplane itself can give us breakthroughs any time soon.
The obvious answer is in making the fuel itself carbon neutral, by storing the sun’s energy of today in the chemical bonds of hydrocarbon fuel. Once fuel is produced with the process explained below, the infrastructure of the aviation industry need not change.
Why Saudi Arabia? They make money from oil….
You’d think that the Saudi’s would have nothing to do with clean energy. However, there are major solar energy projects already underway for electricity generation in Saudi Arabia. As prices for oil goes up, this form of energy is looking to be a cheaper alternative to burning oil for power generation. The pure economic case for solar energy is slowly building.
There is also the major advantage for a nation that is part of OPEC, which effectively sets the world’s oil price, to have a stake in carbon neutral oil. Give the task to a nation outside of OPEC, and they can effectively kill off such an emerging industry by forcing dirty oil prices down.
If they are also producing carbon-neutral oil, however, they suddenly have a reason not to push down dirty oil prices: to support an industry that they can call their own.
Then there is the other point that if you want to start taking CO2 out of the air and back underground, then their oil wells look like a pretty damn good place to put it!
Here are my workings:
To Make the Liquid Fuel from CO2, Gas and Electricity
From: https://www.cell.com/action/showPdf?pii=S2542-4351%2818%2930225-3
To capture 1 tonne of CO2 and turn it into liquid fuel, 5.25GJ of methane is required, and 366kWh of electricity.
Assuming 90% energy efficiency, this results in [5.25+(366*0.0036)] * 0.90 = 5.91GJ of oil
5.91GJ of oil produced
…from 5.25GJ of methane
…and 366kWh of electricity
To Make Gas from CO2, Water and Electricity
To make 5.25GJ of methane, using the Sebatier process, with 95% efficiency, 5.25*278/0.95 = 1536kWh of electricity is required.
Given that CO2 + 2H2O => CH4 + 2O2
… which means 2.75 tonnes of CO2 is required for every tonne of CH4 produced
… and 1 tonne of methane is equivalent to 41.9GJ of gas
…the process removes 2.75/41.9=0.0656 tonnes of CO2 for every GJ of methane produced.
To make 5.25 GJ of methane,
… 0.0656*5.25=0.34 tonnes of CO2 is removed from the atmosphere,
… requiring 1536kWh of electricity
To Meet Electricity Demands for the Above
Therefore, 1536+366=1902kWh of electricity is required to remove 1+0.34=1.34 tonnes of CO2 from the atmosphere. 5.91GJ of liquid oil is produced in this process.
1902kWh of electricity input
… resulting 1.34 tonnes of CO2 removed
… producing 5.91GJ of liquid oil
The Demand for Airline Fuel
https://www.statista.com/statistics/655057/fuel-consumption-of-airlines-worldwide/
Global aviation fuel consumption annually in 2019 was 97 billion gallons
97 x 10^9 gallons = 12.7 x 10^9 GJ of oil required to meet world demand for aviation fuel
Solar Power Required in Saudi Arabia
https://www.stats.gov.sa/sites/default/files/indicators_of_renewable_energy_in_saudi_arabia_2017_en_2.pdf
To power the process using solar power in Saudi Arabia, note:
- solar irradiation averages 6.0kWh/m2 per day
- efficiency of PV cells at converting sun’s energy into electricity is about 20%
For each 1GJ of liquid oil production from air, 321.8 kWh of electricity is required
To produce 12.7 x 10^9 GJ of oil, 4,087 x 10^9 kWh of electricity is required.
Per day: 0.0348 x 10^9 GJ of oil, 11.2 x 10^9 kWh of electricity
To meet demand, (11.2×10^9 / (6.0*0.2)) = 0.37 x10^9 m2 of PV cells are required.
… or 370km2 of PV cells produces 12.7 billion GJ of oil
Total area of Saudi Arabia is 2,149,690 km2
Therefore, covering 0.017% of the ground in Saudi Arabia will produce enough energy to provide fuel for the entire aviation sector of the world.
The cost of energy required
But if this solar energy is too expensive, compared with oil, then we have a problem. Let’s do the sums:
The cost of solar power in Saudi Arabia is looking to be around 2 cents per kWh : https://www.thenational.ae/business/energy/world-s-cheapest-prices-submitted-for-saudi-arabia-s-first-solar-project-1.663842
We said earlier that 1902kWh of electricity would be required to produce 5.91GJ of liquid oil. Or 1902/5.91 = 321kWh per GJ
321kWh @ 2 cents per kWh would cost $6.42. Therefore the cost of electricity of creating liquid oil from air would be $6.42 per GJ
Average jet fuel price in 2019 was $79.7 per barrel, or $79.7 per 5.86GJ. In other words 79.7/5.86 = $13.6 per GJ. The cost of Jet fuel today is $13.6 per GJ
Note that only the electricity costs have been factored in – other capital costs for the air to fuel plants have not been factored in. But given that the buying price of jet fuel is more than twice the cost of the solar power required (which I believe is the major cost), there is room for this. The Carbon Engineering Group have published a paper that goes into the costs of the air-to-oil plant, but I do not understand them enough to plug into these calculations. See https://www.cell.com/action/showPdf?pii=S2542-4351%2818%2930225-3
