How Hydrogen Cars Work ?

The number of vehicles on the road is skyrocketing with time. As per the society of India Automobile Manufacturers, about 26 million vehicles were sold in India in the year 2018-19. As per some other reports, about 6 cars are sold every minute in India. These volumes are massive and the results are visible in the form of overcrowded roads. The huge pollution created by these vehicles has become a great concern for the people. Automotive researchers all over the world are working hard to produce vehicles which can run on sustainable energy sources. Even governments are supporting them in this endeavour. They have realized the great potential of hydrogen to be used as clean source energy. This sector is also attracting huge investments, which is promoting the innovation and advancement of the existing technologies. The Hydrogen cars are less polluting and can cover the long-distance without refuelling. The refuelling of these cars can be done within 5 minutes. This provides them an edge over the electric cars, which need to be charged for long hours before the rides. Today we will discuss the technical details of hydrogen cars.

Types of Hydrogen Cars

Hydrogen can be used as fuel in two ways.  It can either be used directly for combustion as gasoline or can be used to power hydrogen fuel cells. Both of these methods are clean and do not cause any carbon emission. They also decrease our dependency on fossil fuels.

1) Hydrogen Combustion Engine Cars

• A Four Stroke Engine

Hydrogen is a highly reactive gas and burns easily in air. It also has a very high calorific value, which makes it suitable for being used as a fuel. The Hydrogen combustion engines are very similar to the petrol engines. They have all the same parts as of 4 stroke engines, and they work on the same cycles. In these engines Hydrogen can be injected directly or through port injection method. These engines need special gas injectors to cater to Hydrogen fuel.

These engines require better valves and gaskets to prevent any leakage of Hydrogen from the combustion chamber. They also require an engines oil which can work well at higher temperatures. These engines are easy to manufacture since they can be built easily on the existing manufacturing setups. The greatest advantage of these engines is that the combustion product of Hydrogen is pure water. Although these engines do not cause any carbon emissions, the high-temperature combustion leads to the emission on NOx. The ideal air-fuel ratio for Hydrogen is 34:1, but it can burn as lean as 180:1. The higher flame propagation speed and huge calorific value may cause overheating issues, which may lead to auto-ignition of charge at the heated corners. The other disadvantage of Hydrogen is its higher volume. If we are injecting Hydrogen in the air before the combustion chamber, at the air-fuel ratio of 34:1, it will occupy almost 30 percent of the space inside the combustion chamber. This will limit the space for Oxygen leading to poor efficiency of these engines. To eliminate this problem, direct injection is used in these engines. In case of direct injection, the combustion chamber is first filled with air and then the Hydrogen is injected. This ensures the proper air presence for combustion. To prevent overheating and NOx formation, these engines need to be run at lean air-fuel ratios. This reduces its power output. To match the power of gasoline engines, these engines have to be made larger. Some manufactures are also working on using water injectors in the Hydrogen combustion engines. The water injected along with fuel helps in cooling of the engine cylinder, preventing any possibility of premature ignition or NOx formation. This improves the efficiency of the engine by about 5 percent. 

Read More:
   1. Catalytic Converters
   2. Hydrogen Fuel Cell Cars
   3. Crash Tests And Global NCAP Ratings

2) The Hydrogen Fuel Cell Cars

The Hydrogen fuel cells are a hot topic today. The automobile giants like Toyota are investing a lot in building fuel cell based cars. These cars would be driven by a motor, which would be powered by Hydrogen Fuel Cells. This technology has been used for a long period by NASA, for its space programs. These cars would have a sealed fuel tank to store pressurized Hydrogen. This Hydrogen and the Oxygen from atmospheric air would be used in the fuel cell to produce an electric current. This current would power the motor and charge the battery. The emission from the fuel cells would consist only of water and nothing else. This will completely eliminate the emission of pollutants like CO, NOx, PM and SOx from the vehicles. These vehicles will cover 200-300 km on a single filling. Their efficiency would be far better than the gasoline or Hydrogen combustion engines. They would not have the reciprocating parts, which will eliminate the vibrations and the noise. They would not require long charging hours like electric cars. The driving experience of these cars would be just like electric cars. But these cars would not have issues like fast battery discharging in a cold climate or long charging times as of their electric counterparts. 

How does a Hydrogen Fuel Cell Work?

A hydrogen fuel cell is a combination of anode, cathode and a polymeric electrolyte. The polymeric electrolyte is also called proton filter membranes since they allow only protons to move through them. The hydrogen fuel is supplied to the anode while Oxygen is supplied to the cathode. At the anode, the Hydrogen ionizes to produce an H+ ion and an electron. The H+(proton) moves through the polymeric membrane towards the cathode. It does not allow electrons to move through it. The electron moves through an external circuit, to which the motor is connected. This moving electron is called current and it runs the motor, which helps in propelling the vehicle. The by-product if the fuel cell is only pure water, which is non-polluting. 

Fuel Cell Electric Vehicles (FCEVs) Vs Electric Vehicles (EVs)

The FCEVs are being looked upon as a competitor of Electric vehicle. Many experts are saying that it's not EVs but FCEVs which are going to be the future of mobility. There are many arguments in support and against this idea.  Let's compare both these based on certain factors:

Performance

The FCEVs are very similar to electric vehicles in terms of performance and drivability. They are also free from reciprocating engine parts making them smooth and vibration-free.

Range 

The Hydrogen Fuel cell vehicles have a higher range as compared to electric vehicles. The FCEVs generally offer a range of about 300 miles while an electric car would need a huge battery to match this.

Refuelling Time

The greatest advantage of an FCEVs is its quick refuelling time. Normally it takes around  5 minutes to fill its gas tank completely. For Electric Vehicles the charging may take around 6-8 hours with domestic charger while it may take 1 hour with superchargers.

Cost

The FCEVs are currently not manufactured on a large scale. This makes them costlier as compared to electric cars. However, we may expect their prices to fall down with the commencement of their mass production.

Infrastructure

Currently, the world lacks infrastructure for FCEVs. We need to build a network Hydrogen filling stations all across the globe. We also need to set-up production and distribution channels to deliver Hydrogen to these filling stations. At other hands, the Electric Vehicle infrastructure is quite developed. We can charge our electric vehicles easily with our domestic electricity. EV charging stations are also being developed at a fast pace. 

Emission

Both these vehicles are considered emission-free and generate zero harmful emission during their operation. The end product of a Fuel Cell Electric Vehicle is water vapour which is perfectly clean and does not cause any pollution. Electric vehicles at other hands do not have any end product during their operation. However, the generation of electricity with coal and petroleum do generate a lot of pollution. Similarly, the production of Hydrogen also generates a lot of Carbon dioxide causing air pollution.

Cost Of Operation

The operational cost of FCEVs is also very high as compared to the EVs. This is due to the high prices of Hydrogen. The lack of facilities to generate, store and transport Hydrogen increases its cost. The Electricity at other hands is cheaper and easily available all across the globe. The current operational cost of an FCEV is approximately four folds higher than that of an Electric Vehicle. The current Hydrogen production processes are inefficient and require a lot of energy. The most efficient Hydrogen production process is hydrolysis but it is just 80% efficient and needs a large amount of electricity for it. Apart from this, the produced Hydrogen needs to be stored at a pressure 700 times that of the atmospheric pressure for its transportation. The transportation is done through road transports adding further to the cost. The electricity at other hands can be generated very easily and transported through the power grids available across the globe. This makes it way more cheaper source than Hydrogen.

Toyota's Mirai

Front Ducts For Air Intake

At the time when all the companies of the world are thinking about electrical vehicles, Toyota is busy working on Hydrogen fuel cell technology. It has made a significant improvement in this field. Toyota's Mirai is a futuristic car based on fuel cell technology. It utilizes fuel cell stacks developed by Toyota to produce electricity.

This electricity is used to run the motor of the car. Each fuel cell stack consists of 370 cells of thickness 1.34 mm each. The cell stacks can generate a power of 114 kW. The stack is so small that it can be placed under the driver's seat. This lowers the centre of gravity of the car. The air needed for the cells is supplied through the ducts in the front of the car.

For the storage of Hydrogen fuel, it uses a three-layered tank. The internal layer is lined with a polymer to hold the Hydrogen. The middle layer is made of carbon-reinforced polymers to provide strength to the tank. The outer layer is made from glass reinforced polymers to prevent abrasion.  The Hydrogen us filled in the tank at a pressure of 70 MPa and it can store about 5 kg of Hydrogen at the same. The total internal volume of the tanks is 122.4 litres and it takes about 5 minutes to fill it. As claimed by the company, this car can go up to 312 miles in a single filling. The top speed of the car is 111 mph and it can accelerate from 0  to 60 km/hr in 9 seconds. 

The Hydrogen car is a futuristic concept. In spite of being so useful, they are out of the reach of the common man. The availability of  Hydrogen gas is the greatest issue. A lot of research is going on in this field to make this technology viable. Hope we would soon see some remarkable developments in this area.