Engineering

Hydrogen vs Electric, which is the future for transportation?

Fig 1: Cobalt mined globally by country in 2017 in millions of kg [12]

Abstract

With global warming and climate change becoming an ever-increasing issue, sustainable power is growing in demand. In the last decade, electric vehicles have had a surge in popularity, but could hydrogen be a better option? Elon Musk, the CEO of electric car company Tesla stated that hydrogen cars are ‘mind-bogglingly stupid’ and Toyota, a leader in hydrogen-powered vehicles have agreed ‘Musk is right’. Hydrogen’s impact in the car market may indeed remain modest due to efficiency and economic problems. However, ongoing improvements along with advantages of abundance, low emissions and high energy density mean that in the new market of sustainable larger vehicles hydrogen power will soon gain significant market share.

Introduction

A hydrogen-powered vehicle is classed as a Fuel Cell Vehicle (FCV). Hydrogen gas is fed at high pressure to a fuel cell where electricity is produced to power the motor, with water and heat by-products. This compares to a Battery Electric Vehicle (BEV or EV) which is powered by electric motors that pull current from a rechargeable battery. The power to recharge these batteries is normally drawn from the main electricity grid and may come from a wide range of sources including hydrogen. This can be of further benefit as in some regions of the world with excess power from the wind, like the Orkney Islands, the production of hydrogen has become the dominant way to store excess energy. This hydrogen is produced, compressed and stored, and then converted to electricity for the main electricity grid as required.

In this article, I will be assessing how the practicality of a fuel type is critical to its success, particularly range, refuelling time and fuel availability. I will also discuss, considering the surge in sustainable energy needs, the emissions of different fuels and their vehicles in production, lifetime and disposal. The energy efficiency and energy density of the fuel is also an important factor to add to consideration. Finally, I discuss the limitations of each of the fuels in the real world, in production, finances and commercial use. This work is based on using public sources, in particular, data from the Fraunhofer Institute and the US Energy Information Administration service. In addition, articles written by The Week [1] and YouMatter [2], which represent a journalistic view of current ideas, found that working with existing technology, the electric vehicle comes out on top. However, technology is rapidly developing and it is possible the future of transportation could really lie in hydrogen and here is why.

Range and refuelling time

Firstly, consider each vehicle’s range and refuelling time. The Honda Clarity, a best-selling hydrogen car can completely refuel the tank in less than 5 minutes, as it is a similar procedure for filling a petrol car. In comparison, the 2019 Tesla Model 3 takes up to 33 hours charging from home and at least 20 minutes at a Tesla supercharger station [3]. Moreover, many people do not have a garage or facility to charge their vehicle at home. The hydrogen-powered 2020 Honda Clarity has a range of 366 miles on a full tank whereas [4], the electric Tesla Model 3 has a range of 322 miles for the long-range edition [5]. When comparing other transportation methods, the gap widens significantly, for example, semi-trucks. Tesla recently announced the Tesla-Semi boasting a range of 300-500 miles, with a potentially substantial charge time. The hydrogen Nikola One Semi-Truck has a range of 1200 miles, and a fuelling time of 10-15 minutes, like a standard diesel [6]. Overall in both classes of larger vehicle, hydrogen power prevails in terms of range and refuelling being competitive with diesel.

Refuelling options and availability

Another important consideration especially with newer technology is the ease of refuelling. Even if you are unable to charge your car at home, an electric vehicle is relatively easy to charge with over 100,000 public charging points available in the US [7] up from 814 just 10 years ago [8]. This compares with refuelling a hydrogen vehicle where there are only 43 public access hydrogen refuelling points in the US [9], making it very inconvenient to refuel. Before Tesla, many companies were not serious about electric cars and only produced ‘compliance cars’: a category of car created to meet emission standards and not for profit. Tesla made the electric car more viable by investing millions in their supercharger network and by ramping up battery and automobile manufacturing at the Tesla Gigafactory. The same investment in infrastructure has not been forthcoming for hydrogen, where no company has taken the lead to drive the industry forward. Overall the electric car’s lead is decisive and without the infrastructure, the hydrogen transport industry will struggle to expand.

Limitations to battery production

One of the biggest problems in the electric vehicle is current battery technology and when developing electrically powered products, particularly in vehicles, battery life is paramount . Cobalt is one of the major components of a lithium-ion battery and could be a problem for the future development of electric transportation due to its location. The Democratic Republic of Congo (DRC) holds over 60% of global cobalt resources [10] (see fig 1). This is problematic as the DRC is troubled by political instability and corruption thus is ranked 183 out of 190 on the World Bank’s ‘Ease of Doing Business Ranking’ [11]. Furthermore, 20% of cobalt from the DRC comes from artisanal mines where conditions for most workers which include children are terrible and as Congolese militias are often being funded by this cobalt. It is also considered a ‘conflict mineral’, making it more challenging for sustainable and ethically conscious companies to invest in. Finally, cobalt is generally found in grades between 0.05% and 0.4% [12], making pure cobalt mining expensive so almost all cobalt is mined as a by-product of nickel and copper. This causes cobalt prices to be almost completely dependent on the prices of these metals. While there are many potential new battery solutions, the existing production, efficiency, ethics and sustainability, mean new options will need to be found in the future for electric cars.

Fig 1: Cobalt mined globally by country in 2017 in millions of kg [12]

Carbon dioxide emissions by region

Possibly the biggest consideration when comparing any future technology is carbon dioxide emissions, as slowing global warming and the greenhouse effect is vital for the future of the planet. For an electric vehicle, the cleanliness of the energy used to power it is completely dependent on location as an electric car is essentially an appliance to plug in, so is only as clean as the power in that region. For example in the US, Maine has the cleanest grid with 85.3% of the energy produced coming from renewable sources [13] (See fig 2), in contrast, West Virginia has the dirtiest and only generates 7.1% of its energy from renewable sources [14] (See fig 3).

Fig 2: Maine Electricity Generation (%) – Feb 2020 Fig 3: West Virginia Electricity Generation (%) – Feb 2020

Looking at a comparison of emissions for electric, petrol and hybrid cars, emissions are dependent on region and it is not a straightforward result (see fig 4). In West Virginia coal is used as the primary source of energy generation and is one of the dirtiest fuel sources. It produces upwards of 1.0 kg of CO2 per kWh of energy. In comparison, natural gas is much cleaner producing only 0.42 kg of CO2 per kWh [15]. Comparing the cars, the Tesla Model 3 averages 4.5 miles per kWh, the petrol BMW 3 series averages 0.25 kg/mile CO2 [16], and the Toyota Prius Hybrid (electric and petrol) at 0.16 kg/mile CO2 [17]. The results from this information are interesting. The Model 3, assumed to be the greenest, produces 16.9x more CO2 per mile in West Virginia compared to Maine, making the Prius the lowest emissions option. It should also be noted that people with home-based renewable power sources like solar panels, driving an electric car means their driving emissions have the potential to be negligible.

Fig 4: Carbon dioxide emissions of the Tesla Model 3 (electric), BMW 3 series (petrol) and the Toyota Prius (electric/petrol hybrid) in Maine and West Virginia. It is assumed renewable and nuclear power sources do not have any carbon dioxide emissions.

Emissions for hydrogen production

Hydrogen maybe clean in its emissions, but its production can produce huge amounts of green house gases, which need to be factored in to get a true understanding of its sustainability. Hydrogen is predominantly produced in two ways, the first being natural gas reformation (see fig 5). A natural gas containing methane is reacted with high temperature steam at high pressure over a catalyst to produce carbon monoxide and hydrogen. Then, in what is called ‘the water-gas shift reaction’, the carbon monoxide is reacted with the steam producing CO and more hydrogen gas. The final step, called ‘pressure swing absorption’ is where any impurities are removed from the system leaving only hydrogen gas. The process produces roughly 10 kg of CO2 per kg of hydrogen which is enough to drive about 60 miles thus at 0.017kg/mile CO2 which is similar to Toyota Prius in Figure 4. Currently, natural gas reforming produces 95% of hydrogen in the US[18]. The second method is by Proton Exchange Membrane (PEM) electrolysis where, using an electrical current, an electrolyser splits water producing H2 and O2 gas. Provided the electricity drawn from the grid is clean, this is a zero-emissions process, making it the ideal method for future hydrogen manufacturing. This is important when considering the overall impact of hydrogen on the environment and gives a more realistic view of hydrogen’s sustainability in comparison to electrically powered vehicles.

Steam-methane reforming reaction Water-gas shift reaction

CH4 + H2O → CO + 3H2 CO + H2O → CO2 + H2

Fig 5: Reactions taking place in hydrogen production by the steam-methane gas reforming process

Lifetime carbon dioxide emissions

To understand the sustainability of a vehicle, you must compare the lifetime emissions of the vehicle including manufacturing costs. Over its course, the average 21st century car will achieve roughly 200,000 miles [19]. From the graph, (see fig. 6) over the average lifetime of the car, the diesel car produces the most CO2 emissions as well as harmful particulates and NOX. Comparing the least sustainable powering methods for the hydrogen and electric car shows they produce similar emissions. On the other end of the spectrum, comparing the electrolysis extracted hydrogen car and the renewable electricity electric car it is also the case that the hydrogen vehicle overall produces lower emissions over its lifetime. The main emissions issue with the electric vehicles is in manufacturing producing around 23,000 kg of CO2 before being used, and that is assuming the battery would not be changed over that lifetime increasing emissions further. Overall it can be seen that the hydrogen powered vehicle triumphs, but only under natural gas reforming. This shows that under the correct conditions, hydrogen is the more sustainable option.

Fig 6: Carbon dioxide emissions of differently powered cars over their expected lifetime. The diesel car is modelled off the Hyundai Tucson, the FCV (hydrogen) is the Hyundai Nexo and the electric car is a high powered 90kwh electric vehicle [20] (equivalent to a Tesla Model S).

Energy Efficiency

One of the downsides to hydrogen-powered transportation at the moment is its efficiency. The hydrogen car is only 27% energy efficient (see fig 6), taking huge losses particularly in the fuel cell converting hydrogen thermal energy into electrical energy which is only about 50% efficient. This compares to the electric vehicle (see fig 7) which after all major energy losses is 65% efficient, 2.4x more efficient than the hydrogen car. This means producing and using hydrogen has high losses in energy, which further result in losses of money for companies. However, in places with energy surplus such as the Orkney Islands, this is less of an issue. Due to an over-abundance of wind power, surplus energy which would have otherwise been wasted is being used to produce clean hydrogen by electrolysis. This compares with lithium-ion batteries which drain of power if left unused. They also irreversibly age losing their ability to hold charge relatively quickly. Overall the inefficiencies in hydrogen production can be seen as a huge issue for hydrogen fuel cell vehicles when compared to electric vehicles, but do not have the flaw of a battery which degrades over time.

Fig 7: Cumulative efficiency in the distribution for a hydrogen FCV. [21]

Energy density and commercial usage

Hydrogen as a fuel does offer some key advantages over battery power with the greatest being its energy density (see fig 9). The battery has a low energy density so increasing the range of an electric vehicle would mean adding weight and cost compared with hydrogen it would just mean increasing the size of the fuel tank, like a petrol one but in this case 3x lighter. So currently electricity may not replace the fossil fuels used in larger vehicles like planes, boats and trucks as batteries get too heavy, but hydrogen could. Nikola is a company already introducing a hydrogen semi-truck. Most municipalities place weight limits on large cargo trucks at just over 36,000kg and since it is running on hydrogen fuel, the dry weight is minimised, so the payload can be maximised. For the same payload, the Nikola one can achieve up to 4x the distance as the Tesla equivalent. These same principles are being applied to railways, shipping and aviation. For example, ZeroAvia has been granted an experimental certificate by the Federal Aviation Administration to be on track for commercial production of hydrogen planes by 2023. This could be crucial to slowing climate change as CO2 emissions produced by planes at high altitudes are more harmful than road emissions. Even jet fuel has a much lower energy density than hydrogen. In 2018, 905 million kg of carbon dioxide were produced by commercial air traffic [22]. Due to the weight required for purely electric aviation, hydrogen may be the better clean option and if utilised in this industry it could be crucial in reducing this number. This is a crucial factor that hydrogen is superior in and if hydrogen is to become prolific, then it may be a deciding point.

Fig 9: Energy density of different types of fuel compared to the Tesla Model 3 battery. Hydrogen has one of the highest energy densities at 39.4 kWh/kg [23]. The Tesla Model 3 battery achieves 0.16 kWh/kg [24], and petrol 12.9 kWh/kg [23].

Energy costs

Another factor to consider is the pricing of fuels, as the vehicles themselves come in at similar prices. In the US hydrogen prices are roughly at $13.99 per kg [25]. For context the Honda Clarity on a full 5.46 kg tank [4], would cost $57.36 to fill, roughly $0.21 a mile. In comparison at $0.20/kWh for electricity, a Tesla Model 3 can achieve $0.05 per mile. Another issue with hydrogen is it has a very low energy return on investment (EROI), the ratio of the amount of usable energy delivered from an energy resource to the amount of energy used to obtain that energy resource. For example, coal has one of the best EROI values at 46. So, for every unit of energy required to prepare the coal for consumption 46 units can be extracted [26]. Hydrogen produced using the natural gas reforming process has an E-ROI of less than 1, meaning that natural gas has more energy present than the extracted hydrogen. This costliness is the result of little demand and little production. Until a company pushes for the proliferation of hydrogen cars, creating higher demand for fuel and improved production methods, this is not likely to change.

 

Conclusion

Hydrogen produced by electrolysis is a zero emissions process, a vital property for the future transportation. Companies have been producing hydrogen cars as compliance vehicles to align with emissions standards, however, in the market for larger vehicles they boast better refuelling time and range. This is already seen in hydrogen-powered trucks, which provide an immediate new commercial market and the aviation sector will likely follow soon. Hydrogen has a greater energy density than both fossil fuels and batteries, which in the long-term, will be utilised in many ways. Some countries, particularly Japan, are transitioning to a hydrogen-based economy, and developments in infrastructure are already being seen in the availability of domestic hydrogen boilers and other appliances. However, until a company pushes the hydrogen car market forward, infrastructure development will be limited and strongly constrain adoption. The other downside to hydrogen is the energy efficiency issue of its production. The continued rapid development of the electric vehicle means that it will continue to dominate the zero-emissions car market until the industrial production and supply of hydrogen into fuel cells is improved.

References

All website information is based on October 2020 unless otherwise stated

[1] The Week [2019] – “Battery electric vs. hydrogen fuel cell vehicles: which are the better zero-emission cars?”

https://www.theweek.co.uk/electric-cars/101196/hydrogen-fuel-cell-vs-battery-electric-cars-which-are-better

[2] André Gonçalves [2019] – “Hydrogen Cars Vs Electric Cars: Which Is More Sustainable?” https://youmatter.world/en/hydrogen-electric-cars-sustainability-28156/

[3] Pod Point [2019]– “Tesla Model 3 (2019)”

https://pod-point.com/guides/vehicles/tesla/2019/Model-3

[4] Honda [2020] – “2021 Clarity Fuel Cell Specifications by Trim”

https://automobiles.honda.com/clarity-fuel-cell/specs-features-trim-comparison

[5] EV compare.io [2020] – “Tesla Model 3 Long Range AWD” https://evcompare.io/cars/tesla/tesla_model_3_long_range_awd/

[6] Nikola [2020] – “Nikola One specs” https://nikolamotor.com/one#motor-specs-bottom

[7] Isabel Wagner [2020] – “Electric vehicle charging stations and outlets in the U.S.”

https://www.statista.com/statistics/416750/number-of-electric-vehicle-charging-stations-outlets-united-states/#:~:text=Electric%20vehicle%20charging%20stations%20and%20outlets%20in%20U.S.%20%2D%20March%202020&text=In%20March%202020%2C%20the%20U.S.,stations%20and%2028%2C545%20power%20outlets.

[8] Niall McCarthy [2018] – “The Evolution Of U.S. Electric Vehicle Charging Points” https://www.statista.com/chart/13466/the-evolution-of-us-electric-vehicle-charging-points/

[9] AFDC, U.S. Department of Energy [2020] – “Hydrogen Fueling Station Locations” https://afdc.energy.gov/fuels/hydrogen_locations.html#/analyze?region=US-CA&country=US&fuel=HY

[10] GMC [2020] – “Cobalt Supply” https://www.globalenergymetals.com/cobalt/cobalt-supply/

[11] The World Bank [2019] – “Ease of Doing Business rankings” https://www.doingbusiness.org/en/rankings

[12] Florian Mayr, Stephanie Adam [2018] – “Cobalt crunch? Dealing with the battery industry’s looming supply challenges for cobalt”

https://www.apricum-group.com/cobalt-crunch-dealing-battery-industrys-looming-supply-challenges-cobalt/

[13] U.S. Energy Information Administration [2019] – “Maine State Energy Profile”

https://www.eia.gov/state/print.php?sid=ME

[14] U.S. Energy Information Administration [2019] – “West Virginia State Energy Profile” https://www.eia.gov/state/print.php?sid=WV

[15] U.S. Energy Information Administration [2020] – “How much carbon dioxide is produced per kilowatt hour of U.S. electricity generation?” https://www.eia.gov/tools/faqs/faq.php?id=74&t=11

[16] Carbuyer [2018] – “BMW series 3 MPG and CO2 emissions” https://www.carbuyer.co.uk/reviews/bmw/series-3/saloon/mpg#:~:text=The%20330i%20uses%20a%20turbocharged,top%20of%20the%20BiK%20bandings.

[17] Joe Holding [2020]- “Toyota Prius MPG and CO2 emissions”

https://www.drivingelectric.com/toyota/prius/312/toyota-prius-mpg-CO2-emissions

[18] U.S. Department of Energy Office of energy efficiency & renewable energy [2020] – “Hydrogen production: natural gas reforming”

https://www.energy.gov/eere/fuelcells/hydrogen-production-natural-gas-reforming

[19] Dexter Ford, New York Times [2012] – “As cars are kept longer 200,000 is new 100,000.”

https://www.nytimes.com/2012/03/18/automobiles/as-cars-are-kept-longer-200000-is-new-100000.html?_r=2&ref=business&pagewanted=all&

[20] André Sternberg, Christoph Hank, Christopher Hebling [2019] – “Greenhouse gas emissions for battery electric and fuel cell electric vehicles with ranges over 300 kilometers.”

https://www.ise.fraunhofer.de/content/dam/ise/en/documents/News/190815_LCA-BEV-FCEV_Results_EnglishVersion.pdf

[21] Tesla motors club [2016] – “Fair to say the Model 3 killed Hydrogen!”

https://teslamotorsclub.com/tmc/threads/fair-to-say-the-Model-3-killed-hydrogen.67535/page-2#post-1464602

[22] Jeff Overton [2019] – “Airline Energy Intensity and Emissions”

https://www.eesi.org/papers/view/fact-sheet-the-growth-in-greenhouse-gas-emissions-from-commercial-aviation#:~:text=In%202013%2C%20global%20CO2%20from,905%20million%20tons%20in%202018.

[23] The Engineering Toolbox [2008] – “Fossil and Alternative Fuels – Energy Content”

https://www.engineeringtoolbox.com/fossil-fuels-energy-content-d_1298.html

[24] Max Hall [2020] – “Energy density advances and faster charging would unlock EV revolution”

https://www.pv-magazine.com/2020/02/11/energy-density-advances-and-faster-charging-would-unlock-ev-revolution/#:~:text=Chandrasekaran%20said%20the%20Tesla%20Model,vehicle’s%20weight%2C%20at%20around%20480kg.

[25] California Energy Commission [2015] – “Assessment of Time and Cost Needed to Attain 100 Hydrogen Refuelling Stations in California.” Pg 18, https://ww2.energy.ca.gov/2015publications/CEC-600-2015-016/CEC-600-2015-016.pdf

[26] Charles Hall, Jessica Lambert, Stephen Balogh [2014]- “EROI of different fuels and the implications for society”

https://www.sciencedirect.com/science/article/pii/S0301421513003856

About the author

Maksym currently studies chemistry, physics and maths at St Georges School. He had a work experience at Cummins Engines in Darlington, looking into engine design and manufacturing process and was greatly inspired to research further into alternative engines and fuels. In his free time he plays football and the trumpet and after sixth form he wants to study Chemical Engineering.

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