Everything about the hydrogen car: what it is, how it works, its advantages and its future

From March, hydrogen cars will (really) be able to drive on Italian roads. A decree published in the Official Gazette provides for the raising of the maximum operating pressure of refuelling pumps from the current 350 bar to 700 bar. A necessary change to meet the technical requirements of vehicles available on the market. By doing so, modern cars powered by fuel cells will be able to refuel in a few minutes and in complete safety. The hydrogen era will, at last, begin.

Hydrogen is not renewable. It has to be produced

On Earth, hydrogen is not available in its natural form. It cannot therefore be considered a renewable source, at least in a primary sense. It is rather an energy carrier. At present it is produced through coal gasification and the chemical processing of hydrocarbons – both practices that are unsustainable, given the large quantities of carbon dioxide released into the atmosphere – or through steam reforming of natural gas – a procedure that involves reacting methane and steam at a temperature of between 700 and 1,100°C to produce syngas, a mixture of carbon monoxide and hydrogen – or, alternatively, through two environmentally compatible systems. The first involves harnessing algae, as well as sludge and wastewater, in dedicated bioreactors; the second relies on the electrolysis of water.

Wind or solar electrolysis is sustainable

The electrolysis of water involves a low-voltage current passing through the fluid and generating oxygen and hydrogen in gaseous form. In the past, the electricity consumed by this process had a greater value than that of the hydrogen produced; the energy balance was therefore negative and unsustainable. Producing one kilogram of hydrogen required at least 45 kWh, whereas today technology — aided by the availability of aqueous solutions of renewable alcohols such as ethanol, glycerol and other biomass-derived extracts — puts the energy requirement at 18.5 kWh. Energy that is increasingly supplied by renewable sources (wind and solar above all) and in some countries, such as Germany, is linked to the need to absorb production peaks, optimising the entire system and making hydrogen a source that is, lato sensu, "renewable".

A positive energy balance is possible

Producing hydrogen using renewable sources makes it possible to consider the energy balance positive. This is the view of, for example, Toyota, the world's first brand to bring a series-production fuel cell car to market, which is committed to creating a virtuous supply chain in the Japanese cities of Yokohama and Kawasaki thanks to the hi-tech Hama Wing wind power plant. For hydrogen to become cost-effective — and therefore economically sustainable as well — further developments are nonetheless needed. First and foremost, the expansion of refuelling points and fleets of cars and buses capable of ensuring an adequate throughput for each station. An approach that, in brief, would minimise financial risks and transform the distribution of this fuel from a niche technology into a mass-market solution. A horizon in which some manufacturers firmly believe, drawn by the goal of producing zero-emission vehicles — provided that the hydrogen does not, as mentioned, come from fossil fuels — with a generous range that can be replenished in just a few minutes.

The hydrogen car relies on electrochemistry

Hydrogen propulsion systems convert the chemical energy of this fuel into mechanical energy according to two basic approaches: by burning it in an internal combustion engine, as happens with Nasa rockets — the American space agency — or by reacting it with oxygen in a fuel cell — fuel cell in English — so as to produce electricity. Vehicles following the first approach are known as HICEVs (Hydrogen Internal Combustion Engine Vehicles), while the latter are known as FCEVs (Fuel Cell Electric Vehicles). The mobility of the future belongs to the latter, given the absence of emissions and the accessibility of the technology required to achieve noteworthy range from a single refuel.

Fuel cells produce energy. And water

Fuel cells, the heart of modern hydrogen cars, are electrochemical devices that make it possible to obtain electricity from the combination of hydrogen with oxygen, without any thermal combustion process. The reaction required to achieve this is based on the idea of splitting hydrogen molecules into positive ions and electrons; the latter, passing through an external circuit, provide an electric current proportional to the speed of the chemical reaction, which can be used for any purpose. This reaction produces a by-product, water, which can be released into the natural environment as it is perfectly compatible with it and entirely unaltered.

Hydrogen must be compressed

The technical problems associated with the use of hydrogen in road transport relate essentially to its low volumetric energy density — especially when compared with hydrocarbons — which requires particularly high pressures for storage or, alternatively, cryogenic treatment. No alternatives currently exist in the automotive sector, given that both the adoption of large tanks and storage in the form of ammonia, metal hydrides, synthetic hydrocarbons — such as methanol — or carbon and silicon nanotubes are poorly suited to use on board compact vehicles. Storage pressure therefore plays a central role in the use of hydrogen for transport, whilst also raising questions that concern not so much safety as the feasibility and sustainability of the system, since compressing hydrogen entails an expenditure of energy.

The hydrogen car shares the advantages of electric vehicles

A hydrogen-powered car is an electric car, but equipped with fuel cells rather than conventional batteries. In terms of driving experience nothing changes, given that advantages such as instant torque, linear power delivery, smooth acceleration and outstanding comfort are not in question. Moreover, the additional benefits are not lost either, such as free access to restricted traffic zones — for example Milan's Area C — free parking in paid bays and a five-year vehicle tax exemption across the whole country (lifelong in Lombardy and Piedmont). Once that period has expired, the amount payable is reduced by 75 per cent compared to the standard rate.

The hydrogen car refuels in just a few minutes

Compared to "conventional" electric cars, the hydrogen car can count on two fundamental advantages: refuelling in just a few minutes and an extended range. On the first point, thanks to the latest-generation refuelling systems it is possible to "fill up" in a time not unlike that of fossil fuels, while on the second point real-world ranges of around 600 kilometres are already achievable today. These are milestones still out of reach for battery-electric cars which, even when opting for high-capacity charging points — still far from widespread — require considerably longer energy replenishment times. The flip side is that hydrogen cars are expensive, partly due to their extremely limited uptake, with list prices starting at around 60,000 dollars (55,000 euros) in the United States for the Honda Clarity Fuel Cell and from 66,000 euros (plus local taxes) in Europe for the Toyota Mirai. In addition, the distribution network is in an almost embryonic state. The only facility in Italy currently capable of producing and storing hydrogen — thereby supplying vehicles ranging from public urban transport buses to a fleet of cars for hire — is the one in Bolzano, created through the H2 Alto Adige project. As mentioned at the outset, however, from 31 March things could change.

The United States also believes in the hydrogen car

The biggest brake on the uptake of hydrogen is linked to the high costs affecting both vehicle production and the construction of distribution infrastructure. The retail infrastructure is essentially yet to be invented almost everywhere, and beyond the legislative hurdles that until recently limited its potential, the investment required for each dispensing point remains a stumbling block. An obstacle that can nonetheless be overcome through public and private support, as the United States demonstrates, where, by mid-2017, thanks to initiatives from both car manufacturers and institutions, around sixty facilities are set to be operational, located primarily in California (48) and in five East Coast states — namely New York, New Jersey, Massachusetts, Connecticut and Rhode Island. Stations created with the aim of establishing a genuine "hydrogen corridor" stretching from the greater New York area to the greater Boston area.

27,000 hydrogen cars expected in Italy by 2025

Bob Carter, Vice President of Toyota America — the Japanese manufacturer is a firm believer in the Mirai hydrogen saloon — argues that "in the United States there are already 16,000 potential buyers of a fuel cell car. We simply need to guarantee them an acceptable refuelling network. After that, the market will start to grow inexorably." An assessment shared by rival Honda and, in the European context, one that finds particular support in Germany, where 22 operations are already active and the opening of fifty new filling stations is anticipated, and in Italy. The Strategic Plan for the Development of Alternative Fuels aims to bring 27,000 fuel cell vehicles onto Italian roads by 2025, a figure set to reach 8.5 million by 2050 — 20 per cent of the vehicle fleet — supported by a refuelling network of 5,000 stations. Staggering numbers that, if turned into reality, will exceed even the most optimistic expectations.