Hydrogen fuel cell cars: everything you need to know

9 min reading time
When it comes to alternative power sources for engines, to the mind of the general public, the fuel cell battery currently lags behind. Yet experts believe that hydrogen fuel cell cars will catch up. But how does the technology work? What are the pros and cons? Read on for the answers to all the key questions.

17 March 2020

Fewer pollutants, less noise – these are among the many great hopes for electrically powered vehicles. When it comes to electromobility, most people think of vehicles with a large battery that you charge from a wall outlet. Yet there is another propulsion technology that traffic experts are expecting a lot from – including an alternative to long charging times.

The technology in question is the hydrogen engine, also known as the fuel cell electric vehicle, or FCEV. Before we discuss the pros and cons of hydrogen fuel cell cars, as well as the costs and risks involved, we’ll first briefly outline how this technology works.

1.

How does a hydrogen engine work?

Hydrogen fuel cell cars are powered by an electric motor and are therefore classified as e-cars. The common abbreviation is FCEV, short for “Fuel Cell Electric Vehicle,” in contrast to a BEV or “Battery Electric Vehicle.”

There is one crucial difference between hydrogen fuel cell cars and other electric vehicles – hydrogen cars produce the electricity themselves. So, unlike in fully electric or plug-in hybrid vehicles, the vehicle doesn’t get its power from a built-in battery that can be charged from an external power source (➜ Read more: Electric cars and plug-in hybrids explained). Instead, hydrogen cars effectively have their own efficient power plant on board: the fuel cell.

In the fuel cell of an FCEV, hydrogen and oxygen generate electrical energy. This energy is directed into the electric motor and/or the battery, as needed.

In fuel cell technology, a process known as reverse electrolysis takes place, in which hydrogen reacts with oxygen in the fuel cell. The hydrogen comes from one or more tanks built into the FCEV, while the oxygen comes from the ambient air. The only results of this reaction are electrical energy, heat and water, which is emitted through the exhaust as water vapor. So hydrogen-powered cars are locally emission-free – more about that in a minute.

The electricity generated in the fuel cell of a hydrogen engine can take two routes, depending on the demands of the specific driving situation. It either flows to the electric motor and powers the FCEV directly or it charges a battery, which stores the energy until it’s needed for the engine. This battery, known as a traction battery, is significantly smaller and therefore lighter than the battery of a fully electric car, as it’s being constantly recharged by the fuel cell. 

Like other e-cars, hydrogen vehicles can also recover or “recuperate” braking energy. The electric motor converts the car’s kinetic energy back into electrical energy and feeds it into the back-up battery.

2.

The pros and cons of hydrogen-powered cars for users

The pros and cons of a particular propulsion technology can be seen from two main perspectives: that of the user, and that of the environment. If any technology is to succeed as an alternative to the combustion engine, it must be user-friendly and significantly reduce the emission of pollutants. We’ll start by examining the key benefits and disadvantages for drivers/owners of hydrogen fuel cell cars – with the help of Axel Rücker, Program Manager Hydrogen Fuel Cell at the BMW Group.

Advantages for users:

  • The propulsion in hydrogen fuel cell cars is purely electrical. When you drive one, it feels similar to driving a regular electric car. What does that mean? Virtually no engine noise and a lively start, because electric motors provide full torque even at low speeds.
  • Another advantage is the quick charging time. Depending on the charging station and battery capacity, fully electric vehicles currently require between 30 minutes and several hours for a full charge. The hydrogen tanks of fuel cell cars, on the other hand, are full and ready to go again in less than five minutes. For users, this brings vehicle availability and flexibility into line with those of a conventional car.
  • For the time being, hydrogen cars still have a longer range than purely electric cars. A full hydrogen tank will last around 300 miles (approx. 480 kilometers). Battery-powered cars can match this with very large batteries – which in turn will lead to an increase in both vehicle weight and charging times.
  • The range of fuel cell vehicles is not dependent on the outside
    temperature. In other words, it does not deteriorate in cold weather.

Current disadvantages for users:

Currently, the biggest shortcoming of hydrogen fuel cell cars is the sparsity of options for refueling. A hydrogen engine is refueled at special fuel pumps, which in the future will probably find their way into ordinary service stations. As things stand, however, there are still very few refueling stations for hydrogen-powered cars. At the end of 2019 there are only around 40 in the U.S., as compared to approx. 80 in Germany.

“We have a chicken and egg problem with hydrogen fuel cell technology,” explains BMW expert Rücker. “As long as the network of refueling stations for hydrogen-powered cars is so thin, the low demand from customers will not allow for profitable mass production of fuel cell vehicles. And as long as there are hardly any hydrogen cars on the roads, the operators will only hesitantly expand their refueling station network.”

BMW’s homeland of Germany leads the way in terms of infrastructure for hydrogen fuel cell cars. In order to promote the expansion of refueling infrastructure there, vehicle manufacturers like BMW have joined forces with hydrogen producers and filling station operators in the Clean Energy Partnership initiative, which plans to expand the hydrogen fueling station network to 130 stations by 2022. That would allow the operation of about 60,000 hydrogen cars on Germany’s roads. The next target, with a corresponding increase in fuel cell vehicles, will be 400 stations by 2025. More fueling stations are also needed in neighboring countries to actually make it possible to travel outside Germany via FCEV, according to Rücker.

3.

How much do hydrogen-powered cars cost – and why?

In addition to the thin fueling station network, there is another reason for the as of yet low demand for hydrogen fuel cell cars: they are relatively expensive to buy. The few models of fuel cell vehicles already available on the market cost around USD 80,000 for a mid- or upper-mid-range vehicle. That’s almost twice as much as comparable fully electric or hybrid vehicles.

There are a range of reasons why hydrogen fuel cell cars are still expensive. In addition to small volumes, which means that production is still to be industrialized, there’s also the question of the need for the precious metal, platinum, which acts as a catalyst during power generation. The amount of platinum needed for vehicle fuel cells has already been greatly reduced. “The general goal is to bring down the price of hydrogen-powered cars to a similar level to that of other electric cars,” explains Rücker.

Another reason for the high purchase price is that hydrogen fuel cell cars tend to be quite large because the hydrogen tank(s) take up a lot of space. The drive unit for a purely battery-driven electric vehicle, on the other hand, also fits into small cars. That’s why classic electric cars can currently be found in all vehicle classes.

In addition to the cost of purchase, operating costs also play an important role in the cost-effectiveness and acceptance of a propulsion technology. In hydrogen fuel cell cars, these costs are not least dependent on the price of the fuel. At present, 1 lb (0.45 kg) of hydrogen costs around USD 14 in the U.S., as compared with USD 4.80 in Germany (this is the price the H2 Mobility partners have agreed on). An FCEV can drive about 28 miles (45 km) on 1 lb (0.45 kg) of hydrogen.

The cost per mile of running hydrogen cars is therefore currently almost twice as high as that of battery-powered vehicles charged at home. Rücker expects these operating costs to converge: “If the demand for hydrogen increases, the price could drop to around USD 2.50/lb (USD 5.60/kg) by 2030.”

4.

How environmentally friendly and sustainable is hydrogen fuel cell technology?

A car that uses only renewable energy and produces no harmful emissions would be ideal from an environmental point of view. Let’s take a look at how close fuel cell cars are to this goal in comparison to other types of propulsion:

  • Alternative propulsion systems are designed to reduce the emission of pollutants, in particular climate-harming CO2, but also other noxious gases such as nitrous oxide. The exhaust gas from a hydrogen engine consist of pure water vapor. Hydrogen fuel cell technology is therefore locally emission-free. This means it keeps the air clean in cities, but does it protect the climate at the same time?

  • That depends on the conditions under which the hydrogen for the fuel cell vehicles was produced. Hydrogen production requires electrical energy. This electrical energy is used to break water down into its constituent elements, hydrogen and oxygen, via the process of electrolysis. If the electricity used comes from renewable energy sources, the hydrogen production has a neutral carbon footprint. If, on the other hand, fossil fuels are used, this will ultimately have a knock-on effect on the carbon footprint of the fuel cell cars using the hydrogen. How strong that effect is depends on the energy mix used. In this respect, hydrogen fuel cell cars are no different from other electric vehicles.

  • However, one disadvantage of producing hydrogen is the losses during electrolysis. The overall efficiency in the “power to vehicle drive” energy chain is therefore only half the level of a BEV.
  • However, hydrogen can be produced at times when there is an oversupply of electricity from renewable energy sources when the wind or solar energy currently produced is not otherwise used. The potential for this is huge.
  • Hydrogen is also a by-product of many industrial processes, where all too often it is treated as waste with no further use. The fuel cell battery offers a way to upcycle this hydrogen, although it must be cleaned first.
  • The energy balance sheet for hydrogen fuel cell cars also has to include the transportation and storage of the hydrogen. Depending on the transportation technology used (liquid or gaseous), different costs for compression, cooling, transport and storage arise. Due to its better transportability and storage ability, the trend is towards liquid hydrogen. Nevertheless, the transportation and storage of hydrogen are – at this stage – still a good deal more complex and energy-intensive than for gasoline or diesel. In contrast to fossil fuels, hydrogen can be produced anywhere there is access to electricity and water, theoretically even at the actual filling stations for fuel cell cars. A more highly developed infrastructure could thus shorten transportation distances significantly in future.

In conclusion, hydrogen fuel cell technology has the potential to make ecologically sustainable mobility possible. However, according to BMW’s expert Axel Rücker, this would above all require the use of renewable energy sources when producing the hydrogen used, as well as an expansion of the technological infrastructure in order to shorten transportation distances.

Electric vehicles can deliver a real contribution to climate change mitigation, provided the entire value chain is sustainable.
Oliver Zipse

CEO of BMW AG

5.

What are the risks of hydrogen fuel cell cars?

What happens when hydrogen reacts with oxygen in an uncontrolled reaction? Many people will remember this from chemistry class at school. What you get is an explosive reaction known as an oxyhydrogen gas reaction. Hydrogen is flammable, as this shows, but an uncontrolled reaction of hydrogen and oxygen in the operation of an FCEV is virtually impossible.

This is because, in hydrogen fuel cell cars, the hydrogen is stored in liquid form in thick-walled tanks that are particularly safe. As Rücker emphasizes, numerous crash tests have confirmed the safety of how hydrogen cars are designed: the tanks came out of the tests undamaged and no hydrogen leaked.

We should also not forget that hydrogen technology is not new, but is tried and tested in a range of fields. By way of example, refineries today use large quantities of hydrogen as a process gas in the processing of crude oil. Pipelines and hydrogen storage have also been in operation for decades.

Crash tests have shown that the hydrogen tanks are not damaged in a collision and that no hydrogen escapes.
Axel Rücker

Program Manager Hydrogen Fuel Cell at the BMW Group

6.

What role will hydrogen fuel cell technology play in the future?

BMW is convinced that hydrogen can make an important contribution to sustainable mobility alongside BEVs in the future – provided the necessary hydrogen infrastructure is in place and offers a good price for hydrogen, and the price of the vehicles falls. In those circumstances, hydrogen fuel cell cars can be the zero-emissions technology that allows users to maintain the flexible driving habits they are accustomed to.

The Hydrogen Council, a global initiative of leading energy, transport and industry companies, is also convinced of this. The council sees hydrogen not only as a sustainable future means of propulsion for fuel cell vehicles, but also as a clean energy source for heating, electricity and industry.

Hydrogen fuel cell technology: the customer’s choice

Each driver has different wants and needs when it comes to mobility. Oliver Zipse, CEO of BMW AG, puts it like this: “For us, the central questions are: Which kinds of propulsion and technology will our customers want in the future? And how do we realize their preferences with the maximum possible climate protection?” That’s why BMW will continue to focus on a range of different propulsion concepts – the classic combustion engine, fully electric vehicles and plug-in hybrids, and more research into hydrogen fuel cell cars.

Illustration: Cyprian Lothringer; Video: Benjamin Roth; Author: Nils Arnold

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