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1) Without emissions pricing/regulations, synthetic liquid fuel costs more to produce than fossil-derived liquid fuels, so it is unprofitable. 2) Even assuming
by philipkglass 7y ago
1) Without emissions pricing/regulations, synthetic liquid fuel costs more to produce than fossil-derived liquid fuels, so it is unprofitable.
2) Even assuming that there were emissions pricing/regulations that kept fossil fuels in the ground, synthetic liquid fuel is much more capital intensive and energy intensive to produce than the corresponding amount of electricity needed to move a car N kilometers.
Synthetic fuels have a place in the future for applications that require high energy density like aircraft, rockets, and long distance shipping. But burning synfuels in legacy internal combustion engine vehicles is, generally speaking, not going to have a lower systemic cost than replacing ICE vehicles with battery electric vehicles and charging them with clean electricity.
A sketch of the problem: the Oryx Gas to Liquids plant is a modern Fischer-Tropsch plant that produces about 34,000 barrels (5.4 million liters) per day of liquid hydrocarbon fuels:
https://qp.com.qa/en/QPActivities/Pages/SubsidiariesAndJointVenturesDetails.aspx?aid=37 https://qp.com.qa/en/QPActivities/Pages/SubsidiariesAndJoint...
It cost about a billion dollars to build. A corresponding electrical synfuel plant would cost significantly more. You could eliminate the natural gas reformer and desulfurization processes, but would need to add:
1) CO2 separation unit sufficient to extract 14.2 million kilograms of CO2 from the atmosphere, daily (to supply the carbon found in 5.4 million liters of synthetic diesel fuel). Since the air contains ~400 ppm CO2, you need to process about 35.5 billion kilograms of air per day to get sufficient input CO2. Capital costs: wild-ass guesses, because nobody has built anything like this at scale. There's a recent claim that it direct air capture could cost "as low as" $94 per ton of CO2 [1]. That would come to 1.3 million dollars per day.
2) Enough hydrogen per day to turn all that CO2 into liquid fuel. Assuming an empirical "average diesel" formula of C12H24, you need 12 moles of CO2 and 48 moles of H2 to make a mole of diesel: 12 CO2 + 48 H2 -> C12H24 + 12 H2O. In terms of mass, that's .18 kilograms of hydrogen for every kilogram of CO2 -- 2.58 million kilograms of hydrogen per day.
3) A clean source of hydrogen. Electrolysis driven by clean electricity is the only process demonstrated at scale. Assuming it takes 46 kWh of electricity to produce a kilogram of hydrogen from water, and that plant capital costs are $975 per kg-H2/day [1], that's an electricity consumption of 118,860 megawatt hours per day plus an electrolyzer complex cost of $2.5 billion.
4) Electricity to drive the electrolyzers. The very cheapest electricity from hydro, nuclear, or renewable sources is somewhere between $20-$30 per megawatt hour. Such low priced electricity isn't available everywhere; in some countries, even large industrial buyers pay $40 and up. At the lower end that's 2.4 million dollars per day for electricity.
Adding it all up, the electricity and air capture costs alone come to about 69 cents per liter of diesel in costs. That is even though I have tried to make very charitable assumptions about how low the costs could be kept. The wholesale price of diesel in the US is currently about 51 cents per liter:
https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=EMA_EPD2D_PWG_NUS_DPG&f=M https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=E...
I don't know how to properly amortize the extra capital investments to give a per-liter figure, but keep in mind that just adding the hydrogen electrolyzers triples the capital requirements for the whole complex. Note that I have budgeted nothing for labor either.
Finally, how much transportation do you get out? 5.4 million liters of diesel provides 85 million vehicle-kilometers in a 2019 Chevrolet Cruze:
https://www.fueleconomy.gov/feg/PowerSearch.do?action=alts&path=3&year1=2019&year2=2020&vtype=Diesel&srchtyp=newAfv https://www.fueleconomy.gov/feg/PowerSearch.do?action=alts&p...
118,860,000 kWh of electricity provides 645 million vehicle-kilometers in a Tesla Model 3 (assuming 80% generation-to-battery efficiency):
https://pushevs.com/2017/08/01/tesla-model-3-efficiency-impressive/ https://pushevs.com/2017/08/01/tesla-model-3-efficiency-impr...
The battery-electric propulsion solution delivers more than 7 times as much range per kilowatt hour of electricity spent, compared to clean synthetic fuel, and even more per dollar spent.
[1] https://www.sciencemag.org/news/2018/06/cost-plunges-capturing-carbon-dioxide-air https://www.sciencemag.org/news/2018/06/cost-plunges-capturi...
[2] https://www.energy.gov/eere/fuelcells/doe-technical-targets-hydrogen-production-electrolysis https://www.energy.gov/eere/fuelcells/doe-technical-targets-... -- using the "2015 target" numbers for centrally located electrolysis.
- sprash 7y agoConcerning point 1: Of course it will always be cheaper to pump Oil directly out of the ground. Nobody claimed otherwise. Concerning point 2: A few billion investment seems to me far less than forcing everybody to switch to electric and building a vast network of charging stations and additional power plants to power those cars. (Which right now predominantly work with coal what everybody somehow seems to be ignoring) Concerning point 2,3 and 4: Generating Hydrogen can easily be done with heat which you have plenty of when using solar as your primary energy source. Using electrolysis is overkill at that point. Besides that, 69 cents per liter diesel is really not that bad considering most people in e.g. Europe pay vastly more per liter because of massive taxes. The real problem I really see is the CO2 capture. As you said, nobody tried that at a huge scale. But maybe there is innovation possible. It won't work if synthetic fuels are taxed the same way as fossil fuels. That is entirely obvious. I agree with that.
- philipkglass 7y agoIt's not easier to generate hydrogen with thermally driven processes than with electricity. People have certainly proposed thermally driven methods that could use solar heat or the output of high temperature nuclear reactors. But none of them have reached pilot plant scale, and IMO they are going to be hard to make reliable/affordable because they combine high temperatures with chemically aggressive environments.
- sprash 7y agoAgain, here[1] a process is demonstrated that generates CO and H directly out of CO2 and H2O with a specialized catalyst using only heat from direct sunlight on a large scale. No electrolysis necessary. [1]: https://www.dlr.de/content/en/articles/news/2019/02/20190613_solar-fuel-breakthrough.html https://www.dlr.de/content/en/articles/news/2019/02/20190613...
- philipkglass 7y agoThat's another research project that hasn't even reached pilot plant scale. Here is the main web site for the project: https://www.sun-to-liquid.eu/ https://www.sun-to-liquid.eu/ The preceding EU-project SOLAR-JET has recently demonstrated the first-ever solar thermochemical kerosene production from H2O and CO2 in a laboratory environment (6). A total of 291 stable redox cycles were performed, yielding 700 standard litres of high-quality syngas, which was compressed and further processed via Fischer-Tropsch synthesis to a mixture of naphtha, gasoil, and kerosene (7). As a follow-up project, SUN-to-LIQUID will design, fabricate, and experimentally validate a more than 12-fold scale-up of the complete solar fuel production plant and will establish a new milestone in reactor efficiency. The field validation will integrate for the first time the whole production chain from sunlight, H2O and CO2 to liquid hydrocarbon fuels. If they achieved, say, a 13-fold scale-up, that would mean producing 9100 liters of synthesis gas in the course of the project. Based on the synthesis gas composition from the previous project [1], that might yield around 3 liters of diesel. 3 liters of liquid fuel from a multi-year research project. [1] https://pubs.acs.org/doi/abs/10.1021/acs.energyfuels.5b00351 https://pubs.acs.org/doi/abs/10.1021/acs.energyfuels.5b00351