Alternatives to Hydrogen: Liquid Regenerable Fuels

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1 Alternatives to Hydrogen: Liquid Regenerable Fuels William Ahlgren Electrical Engineering Department California Polytechnic State University San Luis Obispo, CA IEE Emerging Technologies Review Santa Barbara, May 10, 2018

2 Fuel dominates energy trade Fuel is crucial in the global energy system. Replacement by electric power alone is unlikely.

3 Regenerable fuels are needed Fuel + oxygen Energy in Reduction Oxidation Energy out Air + water

4 Regenerable?

5 Regenerable fuel options Hydrogen Ammonia Methanol Reduction Oxidation

6 The trouble with hydrogen Hydrogen is difficult to liquefy Incompatible with legacy infrastructure Serious competitive disadvantage vis-à-vis fossil fuels! Liquid regenerable fuels are needed to displace fossil fuels in a competitive market.

7 Power density Vaclav Smil, 2015

8 Fuel power density William Ahlgren, 2012

9 Figures of merit for fuels Name Formula - State p ρ h H h L ρh L h L F bar kg/m 3 MJ/kg MJ/kg GJ/m 3 km/s TW/m 2 Hydrogen H 2 g Methane CH 4 g Ammonia NH 3 l Propane C 3 H 8 l Methanol CH 3 OH l Octane C 8 H 18 l Ammonia and methanol are not as good as propane and octane, but better than hydrogen and methane.

10 Ammonia is a convenient liquid form of hydrogen Liquid hydride storage material Chemical vs. cryogenic liquefaction Energy supply chain advantage: Front-end conversion cost Downstream savings in transport, storage, distribution, and use

11 The trouble with ammonia Inhalation hazard makes ammonia unsuitable for some applications

12 Methanol is well-known

13 The trouble with carbon-based fuels CO 2 feedstock must be extracted from ambient air

14 Sherwood plot: cost to extract is inverse to concentration Expect N-fuel to be much less costly than C-fuel CARBON DIOXIDE NITROGEN Figure 1. Relation Between the Value of Pure Substances and Their Concentrations in the Mixtures from Which They are Obtained.

15 Ammonia-methanol dual-fuel pair Ammonia is carbon-free but high relative toxicity Methanol is low relative toxicity but contains carbon Complementary: each has strength to compensate the other s weakness Together, ammonia and methanol are a superior alternative to hydrogen

16 Carbon-based regenerable fuels Methanol (MeOH) primary carbon-based renewable fuel simplest and lowest cost serves most uses Dimethyl ether (DME) equivalent to MeOH inter-convertible at high efficiency and low cost better for some uses cooking and heating, diesel Methyl-derived fuel (MDF) complex mixture of higher hydrocarbons produced from MeOH or DME: nch W OH nch Y + nh Y O High energy density like gasoline and jet fuel

17 Cost hierarchy of regenerable fuels NH 3 MeOH/DME MDF lowest cost but hard to handle more costly but easier to handle highest cost high energy density

18 Ammonia fuel meets most needs Professional fuel handlers Moderate energy density 80% N-fuel 20% C-fuel 20% C-fuel includes: 15% MeOH/DME for most highway transport 5% MDF for high-energy density (aviation, military)

19 Ammonia issues Inhalation hazard but extensive safe handling experience Fire/explosion advantage Environmental risks less than oil NOx emission another advantage!

20 Ammonia safer than hydrogen? Health hazard Flammable Unstable Special

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22 Mandatory training every two years

23 Ammonia used to suppress NOx

24 Not perfect good enough?

25 Fuel production Petrochemical (chemical-to-chemical) Thermochemical (heat-to-chemical) Photochemical (light-to-chemical) Electrochemical (electric-to-chemical) Hybrid (photo-electrochemical, thermoelectrochemical, e.g. SOEC; etc.)

26 Petrochemical production? De-carbonize natural gas CO 2 capture prior to combustion rather than after Requires carbon sequestration Near-term bridge solution Strategy: grow market for ammonia as fuel

27 Feedback prevents change No reason to produce engine Fuel not available Engine not available No reason to produce fuel Status quo is stabilized in a vicious cycle: economic inertia.

28 Feedback will enable change Trigger Lower Half-cost, fuel cost stable supply Increased fuel demand Engine R&D to use fuel More engines Change is driven by a virtuous cycle after a threshold stimulus is applied

29 New fuels: two-step strategy

30 Ammonia as energy carrier enables near-term de-carbonization of electric power generation

31 Base load (GW) electric power Replace natural gas with ammonia Only boiler burners need modification Relatively low cost to implement Ammonia already familiar (thermal de-nox) Zero carbon dioxide emissions at power plant

32 Capture CO 2 at gas fields 390 gas power plants 5 gas fields

33 CO 2 easily captured in NH 3 process 1/3 of total 2/3 of total Source: R. Strait and M. Nagvekar, Carbon dioxide capture and storage in the nitrogen and syngas industries. Nitrogen+Syngas 303 (Jan-Feb): 1-3 (2010).

34 Geologic sequestration of CO 2 Inject CO 2 from producing gas fields into near-by depleted gas fields Net effect: replace CH 4 with CO 2 Carbon pricing mechanisms required

35 Scenario 2035 Suppose all global electricity production projected to be supplied by natural gas and coal in 2035 were instead supplied by ammonia. How much ammonia would be needed?

36 Feasible path to GHG mitigation 2035 global ammonia production would have to be about 21 Gt/y 84-fold increase over 0.25 Gt/y, the current projection for fertilizer demand in Large but feasible. Outcome is complete de-carbonization of the electric power sector. A path worth exploring!

37 Thank you for your attention