Hydrogen fuel cell cars
Fuel cells are devices that convert chemical energy (in this case hydrogen) directly into electrical energy, water and heat. In most hydrogen fuel cell cars, a high-power fuel cell and motor combination provide propulsion in place of an internal combustion engine.
Hydrogen fuel cell technology is an area of the automotive industry that is becoming increasingly important as more manufacturers commit to developing this type of power-train.
Like electric cars, hydrogen powered fuel cell electric vehicles (FCEVs) are are classed as ultra low emission vehicles (ULEVs) since the only substance to come out of the exhaust is water vapour.
As most FCEVs have an on-board battery for temporary energy storage, they are in this sense similar to a plug-in hybrid electric vehicle (PHEV), the fuel cell performing the same role as the PHEV's small combustion unit.
- What fuel cell cars are available?
- Owning a fuel cell vehicle
- How does a fuel cell car work?
- Are fuel cell cars better for the environment?
- What are the costs of a fuel cell car?
What fuel cell cars are available?
Hyundai and Toyota have gone about creating their models in different ways, with the ix35 fuel cell adapted from the company's existing ix35 SUV, whereas the Mirai has been specifically designed from the outset as a fuel cell vehicle. The Honda is like the Toyota in this respect, and it is expected that new manufacturers coming into the FCEV market will follow this approach. There are likely to be a few 'converted' models released though, like the Hyundai, since the development costs are significantly less, even if packaging compromises need to be made.
BMW, Audi, and Mercedes Benz are just some of the companies that have been developing hydrogen fuel cell models, so the market will gradually expand over the course of the next few years. Until then, Toyota, Hyundai, and Honda will remain the main market leaders for this technology, though even small start-ups such as Riversimple, with its ultra-efficient Rasa, look set to compete on some level.
Owning a fuel cell vehicle
Driving a fuel cell car is a breeze. As with any all-electric or automatic transmission vehicle, there are no gears to worry about, the main decision being the level or strength of regenerative braking required. Since FCEVs are electric vehicles, power is available instantly as all mass production models include a battery as part of the power-train. This is to act as a buffer and provide instant power from the electric motor, instead of having to wait for the fuel cell to kick in and provide an electric charge on demand.
However, ownership is not all plain sailing. The current hydrogen refuelling infrastructure (or lack of it) is the biggest constraint with less than half a dozen publicly available refilling stations currently in the UK. The technology is more restrictive than buying a battery electric car since at least most people have access to a home-based socket with which to charge their EV. Given that very few households have a hydrogen refuelling unit in their garage, living within a convenient distance of a public hydrogen refuelling station is essential.
Apart from the lack of locations, refuelling a FCEV is almost as simple and quick as using a petrol pump, and anyone who has used an LPG vehicle will find plenty of similarities. The driver fixes the refuelling station's nozzle to the car and locks it in place creating a sealed system. The pump will then check the seal can withstand the pressure by pre-conditioning it, before proceeding to dispense the hydrogen at the industry standard 70 MPa (10,000 psi) if all is ok.
Using a state-of-the-art 70 MPa refuelling dispenser, a few minutes refuel will provide most FCEVs with around 300 of range miles - as opposed to the half an hour rapid charge for a battery electric car offering around 100 miles of driving. Look out for older 35 MPa units however, as these will only provide a half-fill, so limiting driving range. Once completed, the user simply unlocks the nozzle and replaces it at the pump before driving off on hydrogen fuel cell electric power with zero harmful emissions.
Find hydrogen refuelling stations in the UK via Zap Map by clicking on the map below.
How does a fuel cell car work?
The basic principle of a fuel cell car is that a fuel cell is used to produce an electro-chemical reaction. 'Chemical' because it involves two chemicals - in this case hydrogen from the fuel tank and oxygen from the air - combining, and 'electrical' since electricity is also produced during the reaction.
A fuel cell is similar to a electro-chemical cell (or battery) in that it has a positively charged terminal - anode - a negatively charged terminal - cathode - and in between is an electrolyte - in most cases a PEM (Proton Exchange Membrane). What makes it different from a battery is that a fuel cell only converts energy (hydrogen to electricity), without having also to store the energy within the cells.
Like an individual cell within a battery, as a fuel cell doesn't create a huge amount of electricity by itself (typically a few volts), a number of cells are combined into 'fuel cell stacks' to generate the voltage required.
Within the fuel cell stack, hydrogen is fed to the anode which, once it reaches a catalyst, is divided into hydrogen ions and electrons. The positively charged hydrogen ions are then attracted to the negatively charged cathode, but to get there have to pass through the PEM which only allows hydrogen ions through.
As the electrolytic membrane is impervious to electrons, they are forced to make their way around to the cathode via an external circuit, and in doing so create the electric current which drives the car or charges the on-board battery. Once hydrogen reaches the other side of the membrane, it combines with oxygen - taken from the outside air - and creates water (H2O), which is expelled through the exhaust.
Are fuel cell cars better for the environment?
In terms of tailpipe emissions definitely 'yes', as the only emission from a hydrogen fuel cell car is water vapour. Like fully electric vehicles, FCEVs are therefore a technology that can be used to improve air quality.
In terms of non-tailpipe emissions, most hydrogen is generated using fossil fuels (typically by reforming natural gas), though an increasing amount is being made using renewable electricity (via electrolysis). While the more renewably generated hydrogen the better from an environmental point of view, the emissions generated during hydrogen production (from natural gas) are generally less than burning petrol or diesel in an internal combustion engine.
Some experts maintain that hydrogen fuel cell vehicles are less efficient overall when compared to a battery electric vehicle (BEV). This is true in the sense that electricity taken from the national grid and stored in a BEV battery involves fewer steps than using the electricity to first generate hydrogen, which is then used to generate electricity in a fuel cell.
However, while fuel cell production costs remain high (see below), current FCEVs have significant performance advantages over BEVs: the range of most FCEVs is around three times that of the average BEV and refuelling times are significantly shorter.
The current thinking is that BEVs will be used for shorter, lighter work - commuting, running to the shops or school etc. - with FCEVs used for long-distance or heavy duty applications. The technology is already regularly found in trials for buses and lorries where the green credentials combine with high power and long range capabilities.
What are the costs of a fuel cell car?
For those who are tempted by fuel cell technology, only a few models are commercially available. Unfortunately, these remain expensive compared to similarly sized petrol, diesel or even battery electric rivals. Toyota's Mirai, for example, costs around ￡60,000 with Toyota expected to lose money on every one sold. This price includes the ￡4,500 Category 1 UK Plug-in Car Grant (PiCG) which includes the Mirai as an eligible vehicle.
In the UK, it isn't yet possible to buy a FCEV outright; Hyundai and Toyota only offer cars on lease. While this is mainly due to the limited refuelling infrastructure, it also protects owners from any technical and durability issues associated with a new technology.
Hydrogen is sold in kilograms rather than volume (litres or gallons), and current prices are around ￡10 to ￡15 per kg. As the Mirai's tank holds approximately 5 kg, a full hydrogen refill would cost between ￡50 and ￡75 meaning that hydrogen FCEVS are more expensive per distance able to travel than both internal combustion vehicles and BEVs. With increased hydrogen use though, costs are likely to come down in the future. Manufacturers are removing this problem though by incorporating fuel costs into the cost of the lease. Therefore, you won't need to pay anything 'at the pump' and the entire motoring costs are paid in one lump sum each month.
The rest of the car's running costs again bear a close resemblance to BEVs: servicing costs are significantly less than an internal combustion car because of reduced numbers of moving parts, while consumables such as brake pads are used less because of brake energy recuperation. FCEVs are also exempt from the London Congestion Charging Zone and, with no CO2 emissions, are exempt from paying Vehicle Excise Duty (VED or road tax).