Recent Challenges of Hydrogen Storage Technologies for Fuel Cell Vehicles

1. Recent Challenges of Hydrogen Storage Technologies for Fuel Cell Vehicles Presented by Kareem El-Aswad on 12/4/2012 Article & Research by D. Mori & K. Hirose

2. Some Background Information… • Carbon emissions from factories and vehicles have harmed the environment in recent years. • Excessive Amounts of energy consumption in gasoline (very inefficient energy output). • Mobility requirements will increase in the future; therefore energy sources must be safe and clean. • Due to these requirements, and the fact that relatively clean Hydrogen gas can be used, fuel cell technologies are an ideal solution! • However…

3. Two Major Problems! • Hydrogen gas (H2) has an extremely low density; thus limiting how much can be stored in a vehicle. • Hydrogen gas only has 1/10th the energy as gasoline; which limits how far a vehicle can travel. • Therefore, efficiency and the amount of storable hydrogen must be increased. • However, since all of the hydrogen can’t be stored, it is required to either compress hydrogen gas or to absorb it into a form of solid material.

4. Potential Solution • A new tank design that allows for maximum hydrogen gas efficiency must consider all the following: • Material Density • Heat Conductivity • Volumetric Change • Heat Absorption • Gravimetric Density • Hydrogen Uptake

5. Potential Solution • A new vehicle must consider the following: • Safety • Performance • Cost • Technical adaptation • Scalability

6. Methods • Three Main Proposals were tested & a hybrid was created using the following as a basis: • High-Pressure Tank System • Liquid Hydrogen Tank • Hydrogen-Absorbing Alloy Tank

7. High-Pressure Tank System • Most common tank used for on-road testing currently. • Pressurized at 35-70 MPa; although there is a tendency to use 70MPa so that more hydrogen gas is carried. • Simple structure; easy to charge / discharge.

8. High-Pressure Tank System • Uses V3 & V4 types of tanks. Natural gas tanks use V1 & V2. • GFRP = Glass Fiber Reinforced Polymer. • CFRP = Carbon Fiber Reinforced Polymer. • CFRP is required in higher pressure tanks because it’s much stronger and more resilient.

9. High-Pressure Tank System • Problems include: • Pressure & hydrogen volume is non-linear. Doubling pressure only increase volume by 40-50%. • Weight of the tank is still relatively heavy. Further testing for tank durability is required to make a lighter tank. • Volume of the tank can’t be shrunken down even further due to physical properties (i.e. dramatic increase in pressure & lower vehicle range).

10. Liquid Hydrogen Tank • At 20K (-253.15oC), hydrogen becomes a liquid. • Capable of storing much more hydrogen due to significantly higher density than gaseous hydrogen. • Liquids are potentially easier to handle and store. • Tanks require a double wall to keep low temperatures insulated. • Vacuum Multi-Layered Insulation (MLI) is used to prevent radiation and thermal intrustion.

11. Hydrogen-Absorbing Alloy Tank • Can utilize smallest tank size since it can store hydrogen more dense than liquid hydrogen. • Absorbs up to 2.8% hydrogen. • Reversible hydrogen charge and discharge capacities. • Several critical issues: • Low gravimetric density (% of hydrogen). • Can’t handle large amount of heat. • Inefficient hydrogen release in colder environments. • Still largely in the experimental phase. Optimal materials have not even been determined yet, although various metal alloys are primarily used.

12. The Hybrid Containment System • Designed to improve charge-discharge variables. • 4x45L high-pressure tanks combined with high-pressure absorptive alloys (promotes high volumetric density) which absorbs 1.9% hydrogen. • Metal hydride (Ti1.1CrMn) used. • Cooling system (radiator or fan)

13. Results • 7.3 kg of hydrogen stored @ 35 MPa; 2.5x more than a typical 35 MPa tank. • Can be charged with hydrogen up to 80% in 5 min. • At -30oC, still capable of supplying hydrogen. • Can actually be applied to a vehicle(i.e. size and performance)

14. Results • High-pressure hydrogen environment allows MH to absorb hydrogen quickly. • This solves the issues with classical metal hydrides and creates a method of hydrogen storage for vehicles.

15. Results • Comparison of high-pressure tank, hydrogen-absorbing alloy tank and high-pressure hydrogen-absorbing alloy tank system as follows:

16. Discussion • Hybrid Containment is an effective hybrid of the simpler containment systems mentioned previously. • There is a noted relationship between hydrogen uptake and ΔH, energy to take out hydrogen from hydride; but no concrete theory for this relationship.

17. Possible Future Goals • To reach a 4% absorption rate • To open the possibilities for other chemical containment methods.

18. Conclusion • Very thoroughly well-thought out. • Many different ideas and proposals were considered. • Reservations: • They should’ve used 70MPa, since that’s the most used for hydrogen gas fuel cells. • Using a more efficient cooling system probably could have speeded the hydrogen charge capacity even more.

19. References • D. Mori & K. Hirose. “Recent Challenges of Hydrogen Storage Technologies for Fuel Cell Vehicles" International Journal of Hydrogen Energy. 34 (2009): Pages 4569-4574. • “Why CFRP?” Composites World. 30 Nov 2010. Composites Technology. 2 Dec. 2012 < http://www.compositesworld.com/articles/why-cfrp> • “GFRP – Glass Fiber Reinforced Polymer.” Stromberg. 2 Dec. 2012 < http://strombergarchitectural.com/materials/gfrp>