Previously in our Renewable Energy blog series a few weeks back, we’ve talked about wind power, solar power and geothermal energy sources, considering pros, cons and the technology behind these concepts. In this post we will look at hydrogen fuel cells which is currently being researched to provide a renewable energy source in the automotive industry. To date, manufacturers have only experimented with this technology and it is yet to take off. However, hydrogen fuel cells have the potential to revolutionise the automotive industry.
Toyota Hydrogen Fuel Cell Car Source: www.telegraph.co.uk
Using electro-chemical reactions, electricity can be generated between hydrogen and air. Specifically, combining hydrogen and oxygen produced both water and electricity. A single fuel cell is made up of a positively charged anode and negatively charged cathode, both of which are in contact with an electrolyte that separates oxygen and hydrogen. Only certain ions are allowed to pass through a polymer membrane.
Hydrogen atoms enter the fuel cell through the anode side where they lose their electrons which pass through an external circuit, producing electricity. The positively charged ions pass through the polymer membrane to the cathode side where they are joined by oxygen atoms (producing water) and the electrons.
Source: National Energy Education Project
The maximum efficiency of a hydrogen fuel cell is 83%, significantly higher that 58% for an internal combustion engine. By weight hydrogen is also favorable over gasoline; one kilogram of hydrogen has the equivalent energy of one US gallon of petrol. However, storage can be more difficult since its volume can be four times bigger than petrol and it is highly flammable.
Hydrogen doesn’t exist as an element on its own however, as it forms bonds with other elements. Isolating hydrogen can be difficult and expensive. Extraction involves electrolysis which requires electricity. Of course this may not always be from a renewable source although hydraulic dams can be used. It is unlikely that electrolysis will be 100% renewable however and so hydrogen fuel cells do have a carbon footprint. Hydrogen fuel cells will also only operate within between 0 and 100 degrees centigrade. This is because they require pure water, so at low temperatures fuel cell vehicles may have trouble.
Apart from the production of hydrogen fuel cells vehicles, the only emissions are clean water. The range from a full charge is also comparable to that of petrol and diesel cars today operating.
So far only Japan has invested in building a hydrogen fuel cell supporting infrastructure and without this the development of this technology will be limited. There are less than 20 hydrogen refueling stations in the UK compared with over 5000 electric vehicle charging points. Like with all renewable energy, we need it to be adopted by the masses and not the few. Hopefully over the coming years we will see this as oil prices are predicted to rise and pollution is becoming more of a problem. Although it is possible that electric vehicles may beat hydrogen fuel cells to the mark with the number of electric vehicles available rapidly increasing and technology progressing quickly.