Hydrogen and the Drive for Zero Emission Transportation

There are at least three good reasons why hydrogen vehicles may be preferred over electric, especially for longer range, heavy duty applications

With increasing global focus on reducing carbon emissions, there is significant discussion and excitement for electric vehicles across all applications from personal vehicles to heavy trucks.   However, there are other key zero carbon pathways including bio-fuels (liquid and gaseous), and non-carbon based fuels, of which hydrogen is the major one considered for road transportation.  Hydrogen has recently returned to the spotlight and there are at least three good reasons to consider hydrogen over electric propulsion: (1) it can be used for grid energy storage aiding integration of renewable power and providing hydrogen for fuel, (2) some locales are hard to electrify at scale, and (3) impact of battery weight can become prohibitive in certain vocations.   Taking a closer look at each of these:

Hydrogen Storage

Wind and solar power are not dispatchable and moving to 100% renewable grid power, without energy storage, will lead to excess capacity at off-peak times.   Hydrogen energy storage is an option and there have been a number of announcements on large scale hydrogen generation and storage facilities across the US, including Air Liquide’s $200M investment in renewable liquid hydrogen plant and logistic infrastructure in Nevada, and NextEra’s $65M investment in a green hydrogen plant in Florida.  Stored hydrogen can be used in various ways including converted back to grid power, provide heating, be supplied as an industrial processing gas, and used as a transportation fuel.

A hydrogen storage facility has the potential to improve the cost effectiveness of renewable power integration and also reduce the production cost for renewable hydrogen as a fuel.   Lowering the fuel price of hydrogen becomes an enabler to increasing fuel cell vehicle deployments and in turn, increasing demand for renewable hydrogen, which will also aid further cost reductions.

An often mentioned concern about the renewable power to hydrogen fuel pathway, is the relatively low efficiency of electrolysis systems.   While this is true, there can still be good economic benefits from the renewable power integration and hence significant reduction in the effective cost to generate hydrogen.  These economic benefits can outweigh the efficiency concern, especially as there are no emissions associated with the low efficiency and the renewable power being stored is in excess to grid demands at the time.

Locales hard to Electrify

We often forget that the electric grid is not strong in all areas, and in many locations power systems are at capacity.  Increasing demand may require transmission line overbuild and/or additional power lines as well as distribution system upgrades.   While the costs of these can, in principle, be recovered through electricity rates, utilities have limited capital budgets and will need to prioritize where the upgrades are made across their whole service territory.  This means there will be service areas where electrifying vehicles on a large scale will be costly and low priority.   This has been less of an issue to date as fleets have pilot programs with small numbers of electric vehicles.  It will become much more of an issue, as fleets scale up their zero emission vehicles, and as more fleets will consider electrification due to proposed mandates requiring sales of zero emission trucks and buses. 

This means that in certain areas, electric vehicles may not be a practical, or at least the best solution in the short and medium term.  Hydrogen can be the solution, even if it requires (hydrogen powered) truck delivery of gaseous or liquid hydrogen.

Impact of battery weight and size

The dramatic drop in battery costs over the last few years, has made electric propulsion affordable for many applications, and there are plans for OEMs to offer longer range, electric heavy duty vehicles.  However, battery weight can become restrictive for at very high battery energy levels.   Today, production battery pack energy density is around 150-160 Wh/kg.  Heavy duty trucks and buses may do 0.5-1 miles/kWh, this means for long 300 mile range applications, battery pack energy will likely need to be approaching 600 kWh and for 500 mile range would approach 1000 kWh.   This implies the battery pack weight for these applications would be 8000- 14,000 lbs.  This can significantly impact payload if GVWR limits are maintained at 80,000lbs.  There is also a cost (reduced fuel efficiency) in carrying this additional weight around, and would be especially noticeable in city driving or empty load situations.   There is a further higher capex and operating costs in the high power infrastructure to provide reasonable charging times (a 1 MW charger would need 1 hour to charge a 1000 kWh pack).   Of course, refueling infrastructure is needed for hydrogen too.  However electric vehicle charging infrastructure required tends to grow more quickly than the required hydrogen infrastructure as more vehicles are charged/fuelled.  For larger zero emission, heavy duty vehicle fleets, the required charging infrastructure may be more expensive than a hydrogen refueling infrastructure for the same number of vehicles.   The quicker refuel times with hydrogen can also lead to some operational efficiency and cost benefits.  

This does not mean that electric heavy duty trucks are not a valid option and in various vocations will make economic sense and the technology is readily deployable.  The intended point is that hydrogen can also a good if not best option, especially for the longer range vehicles.

What does this mean for transportation

Hydrogen will have a role in our global path to sustainability providing a solution path integrated with renewable power generation as well as providing zero emission transportation options, especially where electric solutions are handicapped.

There are some challenges to overcome with hydrogen deployments.  Fuel cells are available for passenger cars and longer life (20,000 hour) fuel cells for commercial vehicles are in pilot production.  However total fuel cell system cost today is relatively high and will hopefully enjoy significant reductions as production volumes increase.   Hydrogen dispensed as a fuel is also high today, partly due the price of hydrogen delivered to the refueling stations and partly due to the low daily utilization of the hydrogen stations themselves.  Again, it is anticipated these costs will come down with increasing hydrogen usage. Onboard vehicle hydrogen storage is also a challenge, either needing more high pressure (750bar) gaseous tanks or liquid hydrogen storage to achieve very long ranges.  Higher volumetric density storage media are also in development but these tend to add weight to the vehicles and take away one of hydrogen’s advantages.  At least refueling times are close to those for gasoline vehicles, hence a solution to limited onboard storage could be more hydrogen stations.  

With the advantages of hydrogen, expect to see more deployments of hydrogen vehicles in the next few years with stronger growth in hydrogen vehicles as the economics and hydrogen station availability improves.  It will be an option alongside other alternative fuel vehicles as we move towards zero emission heavy duty transport.