Hybrid and Hydrogen Cars

Changing the way that we power our cars is one of the most promising ways of reducing pollution yet keeping our mobility.  Hybrid cars are already available and some companies have produced some experimental hydrogen cars that have shown their enormous potential.  How they work is described next.

Hybrid Cars

The main source of power in a hybrid car is the internal combustion engine.  However, in order to stretch the fuel as far as possible, the wheels are also driven by an electric motor.  Depending upon road conditions, demand on the engine etc, a computer decides whether to use petrol or electric power. 

Different hybrid systems work in different combinations. Some will use the petrol engine only when moving off from rest and at low speeds, but when accelerating, its computer asks the electric motor to chip in with extra help. As cruising speeds are reached, the electric motor is turned off, leaving petrol power only. When the driver starts to slow down the electric motor becomes a generator and transfers the kinetic energy of the car into the battery as electric power. This is called 'regenerative braking'. Whenever the car comes to a stop, the computer turns off the engine to save fuel and CO2 emissions.

Other hybrid cars combine the electric motor, the internal combustion engine and the battery so that the electric motor can operate on its own when light acceleration is needed at lower speeds. Once the vehicle reaches higher speeds, the internal combustion engine starts up and takes over. Under hard acceleration, both the internal combustion engine and the electric motor can work together to provide the needed power. These hybrids are able to generate and consume electricity at the same time.

Hybrid cars can achieve 83mpg and carbon dioxide output of 80g/km in the combined cycle - that's considerably better than a small diesel car which can manage a hugely impressive 64mpg and 119g/km.  There are two hybrid cars available for sale already and other companies are planning to introduce some soon.

Hydrogen Cars

There are two ways that hydrogen cars could work: with a modified internal combustion engine or with fuel cells.  Hydrogen cars hold a lot of promise as there are no harmful emissions, no depleting of resources, and no danger to the atmosphere.  Having said this one disadvantage of hydrogen cars is that energy is needed to produce the hydrogen so whilst the car itself may be clean (electric cars have this problem as well) pollutants may have been generated whilst producing the hydrogen.

BMW have developed a hydrogen car which as two fuel induction systems: one for petrol and one for hydrogen.  It is more space efficient to store the hydrogen in liquid form, which means a specially insulted tank is needed since the hydrogen is very cold, -253 °C! 

BMW, in partnership with the Shell Oil Company, have developed a way of filling cars up with hydrogen at a petrol station.  The world's first fully automatic hydrogen filling station was opened in May 1999 at the Munich Airport.

BMW have also been part of developments that have resulted in using solar power to produce hydrogen.  Heat from the sun is captured using solar panels.  This energy is then used to split water into hydrogen and oxygen (a process called electrolysis).  The hydrogen is then stored at the low temperatures required to save space.  This method is promising since the energy that is acquired for electrolysis is obtained using solar energy therefore avoiding producing pollutants.

A small company in America, The Hydrogen Car Company has also produced hydrogen cars using a modified internal combustion engine.  They have been able to show that you can have a high performance sports car and still be environmentally friendly.  They have produced a modified Shelby Cobra.  Its performance figures are on a par with normal Cobras as it has a top speed of 140mph and can reach 60mph in 4 seconds.  Shelby Automobiles produce the cars then the Hydrogen car company carry out the modifications. 

Two disadvantages are the range of the hydrogen fuel tank (about 80 miles in the Cobra and 240 miles in the BMW) and the cost.  The tank is also placed in the boot so it reduces luggage space.  It costs about £26,700 pounds to convert a Cobra.  The costs of hydrogen cars would come down once they were being produced on an assembly line though.

Hydrogen cars fitted with fuel cells have a longer range and are favoured by most of the large car companies.  The same amount of hydrogen will take a fuel cell car at least twice as far as one with a converted internal combustion engine.  Fuel cells have made electric cars much more practical because they don't need large banks of batteries to keep them going.  This is because fuel cells make electricity as the car goes along road.

Recent developments in technology have greatly increased the amount of power that a stack of cells – small enough to fit under a car’s bonnet – can provide. This has opened up the prospect of non-polluting electric cars with the levels of performance we expect from conventional vehicles.  Car manufacturers expect to start mass-producing fuel cell hydrogen cars between 2012 and 2020.