Some people think hydrogen is the future of mobility and some say the battery is the future. This article, based on scientific research, compares the efficiency and CO2 emissions of hydrogen fuel cell and battery electric passenger cars. In future updates, other vehicles like buses, trucks, ships and airplanes may be included as well.
BEV & FCEV
Before we compare battery electric vehicles and hydrogen vehicles, let’s first get the terminology clear. There are different types of electric vehicles. For this article only the battery electric vehicle (BEV) and hydrogen fuel cell electric vehicle (FCEV) are discussed.
The BEV is a fully electric vehicle without an internal combustion engine or fuel tank. It has an electric motor and a rechargeable battery. The battery can be charged wherever there is electricity. A simple household outlet, a home/public charge station or fast chargers. The best-known examples are Tesla’s and the Nissan Leaf. Figure 1 shows the platform used in the Tesla Model S and X.
The FCEV is an electric vehicle that also has a (much smaller than a BEV) battery, but also a fuel cell and a tank with compressed hydrogen. Simply put, inside the fuel cell, hydrogen is mixed with oxygen and this results in an electrochemical reaction that produces electricity. This electricity is either stored in the battery or directly sent to the electric motor. An FCEV can only be filled up at a hydrogen station. The best-known examples are the Toyota Mirai and Honda Clarity. Figure 2 shows the platform of the Honda Clarity FCEV.
Figure 3 shows the most important components of the Honda Clarity FCEV with a short explanation.
For more information about the workings of a fuel cell see Wikipedia fuel cell. Now that we have a basic understanding of the workings of both the FCEV and BEV, let’s look at the efficiency.
Before we start with the efficiency of producing a kg of hydrogen, let’s find out how far an FCEV can travel on one kg of hydrogen. In table 1 the hydrogen capacity and range are given for the Toyota Mirai and Honda Clarity (Toyota, 2017; EPA, n.d.1; Honda, n.d.).
According to Hydrogenics (2018), the energy required to produce one kg of hydrogen is between 65 and 68 kWh. This number includes the production of hydrogen and the storage in high pressure (700 bar) tanks. I should mention that this number is for the production process with electricity which is called “electrolysis”. Hydrogen can also be made with natural gas (most hydrogen is made with natural gas) or other hydrocarbons, but I’m only looking at the most sustainable production process which is with (renewable) electricity.
Table 2 provides a comparison of the range of several FCEV and BEV, based on test results from the Environmental Protection Agency of the United States of America (EPA). For both types of cars, the 65 kWh includes charging losses and all necessary steps to get the energy in either the battery or hydrogen tank (EPA, n.d.2).
Looking at these results, it is quite remarkable that even a big heavy SUV like the Model X is more than 2,5 times as efficient as a midsize FCEV. A comparable BEV midsize sedan like the Tesla Model 3 is even 3,75 to 4 times as efficient as an FCEV.
Looking at the efficiencies of FCEV and BEV, it looks like FCEV are a waste when it comes to passenger cars. Hydrogen fuel cell vehicles need 3,25 to 4 times as much electricity to drive the same distance. Remember that both vehicle types are compared on the same amount of electricity needed to drive them a certain distance. In other words, the difference in required electricity is the same as the difference in CO2 emissions.
Emissions from driving the vehicle are the majority of emissions in a vehicle’s lifetime as we will see later on, but production is also a significant part.
Vehicle lifetime emissions of FCEV and BEV
According to the Department of Energy of the United States of America (DOE), the production, recycling and disposal of an FCEV causes about 11.900 kg of CO2 (DOE, 2014), whereas a comparable long-range BEV causes around 10.500 kg of CO2 (Union of Concerned Scientists, 2015).
The figure of 10.500 kg for the BEV is based on the estimate of 15.000 kg for the Tesla Model S 85 which is in its turn based on industry averages (Union of Concerned Scientists, 2015). However, this number can be reduced by 30% because of the lower emission grid of California (Tesla’s factory) and renewable electricity used in Tesla’s battery factory (Union of Concerned Scientists, 2015). A 30% reduction compared to the Model S may sound like a lot, but it does not even take into account that the Model 3 is 400 kg (881 lbs) lighter, has a smaller battery, and has a significant economies of scale advantage because its production is more than four times the production of the Model S. In other words, the production emissions of the Tesla Model 3 are likely even lower. The reason these advantages are not taken into account is that I don’t have a source for an estimated reduction and I don’t like to guess.
With CO2 emission factors, the CO2 emissions for driving the vehicle can be calculated. An example of a CO2 emission factor is the Well-to-Wheel emission of 0,012 kg of CO2 for a kWh from Dutch wind turbines (co2emissiefactoren.nl, n.d.). This factor includes all emissions, from production and maintenance to recycling and disposal of the wind turbine.
The CO2 emission factors used in this article are given in table 3.
Table 4 gives an overview of the lifetime CO2 emissions of FCEV and BEV. The reason I use the Honda Clarity in this example is because it is 7% more efficient than the Toyota Mirai and similar in dimensions.
As you can see in table 4, the lifetime CO2 emissions depend greatly on the source of the electricity (co2emissiefactoren.nl, n.d.). The grey electricity is only produced from coal, gas and a little nuclear and based on the Dutch grid in 2017. The Dutch mix was the mix in the Netherlands in 2017 with 0,431 kg of CO2 per kWh.
With the current electricity mix the inefficiency of FCEV results in much higher CO2 emissions compared to a BEV. A comparable midsize BEV causes 65% less CO2 in its lifetime than a comparable FCEV.
You might look at the wind power scenario and think the difference is small, but remember that an FCEV consumes over 3,75 times the electricity compared to a BEV. Not only does this cause more CO2 emissions but, unless electricity is free, it will cost the owner of the FCEV 3,75 times as much per km than BEV in “fuel” cost. Table 5 provides a summary of the comparison between the Honda Clarity and Tesla Model 3. It also includes the number of 8 MW wind turbines when all passenger cars in the Netherlands would be either an FCEV or BEV to illustrate the difference in energy need between the two technologies. The calculation for the wind turbine number is given under table 5.
The number of 8 MW wind turbines has been calculated with the following data. According to the Central Bureau for Statistics of the Netherlands, passenger cars have driven 118,5 billion km (73,6 billion mi) in 2016 (CBS, n.d.). Modern offshore wind turbines are 8 MW and have a capacity factor of about 50%. Therefore, one turbine will deliver 35 GWh (8*50%*24*365) per year. An FCEV requires 0,61 kWh per km which equals 72.000 GWh or 2.057 wind turbines. A BEV requires 0,16 kWh per km which equals 19.000 GWh or 543 wind turbines.
Refilling hydrogen cars in 3 minutes
One of the most heard arguments in favour of hydrogen is the short time needed to refill the tank. The refill time can be as little as 3-minutes or similar to a gasoline or diesel refill. In reality, it is a bit more complicated. One of the projects working on a 200 kg per day hydrogen filling station is called PHAEDRUS (2015). The project’s aim is to show the feasibility of a hydrogen station with the capability of refilling 36 cars per day with 5,5 kg of hydrogen per car. This translates to dispensing 100 kg of hydrogen (half the capacity of the station) per three hours.
The 36 cars are refilled in two periods of three hours each. Each hour within a period, the station can refill the first car in 3 minutes, compress hydrogen again in 3 minutes and refill a second car in 3 minutes. So, 9 minutes to refill two cars. The other four cars can be refilled in the remaining 51 minutes. The extra time for the other four cars is a consequence of the station needing to compress the hydrogen again to the optimal pressure to provide maximum range. In other words, the average time needed to refill a FCEV is 10 minutes.
Refilling a FCEV is faster than a typical fast charge of BEV which takes between 25 and 55 minutes to get the battery charged to 80%, although developments point to 15 minutes for an 80% charge (Porsche, n.d.). On the other hand, you can charge BEV wherever there is electricity and you can charge your car while doing something else such as: charge at home while sleeping, charge while working, charge while shopping, charge when visiting amusement parks.
Conclusion: hydrogen for passenger cars, win or waste?
Looking at all the data, there is only one conclusion that can be drawn. Hydrogen for passenger cars is a waste. You can have over three times as many BEV driving around than FCEV using the same amount of electricity. Even with low-carbon electricity (wind power) the FCEV is causing 21% more CO2 emissions and requires over 3 times the electricity as a comparable BEV. Even a full-size 7-seater SUV (Tesla Model X) is over 2,5 times as efficient as a midsize FCEV. Let us be economical with the (renewable) electricity we have and use it as efficiently as possible by choosing BEV for passenger cars.
The future of hydrogen
Does this mean that hydrogen has no future? No. One area where hydrogen will probably be very useful is the steel industry. The steel industry requires enormous amounts of energy and emissions and hydrogen can significantly lower the emissions.
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