If you walk you consume food (Chemical Energy) to give your muscles energy, this energy is converted in your body contracting your muscles moving your legs, propelling you along the path. Later you might perhaps consume a chocolate bar or two to provide a bit more energy when you are tired allowing you to go a bit further! Similarly the use of horses and other animals to ride or pull waggons use food as their transport fuel.
The majority of modern transport since the advent of steam engines and the internal combustion engines uses the chemical energy locked away in fossil fuels. These ancient stores of carbon-based fuel are burned to transfer the energy for traction. Electrical energy is also used to propel many form of transport (trains, trams, cars) and so do not directly burn fuels, however it is important to remember that most electricity around the word is generated by burning fossil fuels like coal, gas and oil.
Wind is an ancient source of power for transport on the seas and has been used for at least 7000 years. Whilst sailing harnesses a renewable resource (the wind) it also require significant effort from the crew of a ship and so requires food as a source of fuel.
In 1961 a nuclear reactor was first used in shipping to provide the source of energy to move in the seas, and ever since has been used in the military of a few nations for larger ships and submarines.
Solar PV should also be mentioned in passing, it is still not a practical source of energy for transport as insufficient energy can be captured by PV cells to provide enough power to move substantial objects, but use is increasing and in niche areas is providing some transport needs. Take a look at this wiki article for a good summary of where solar transport is at.
Aircraft are also large consumers of fossil fuels in turbine and jet engines. Unfortunately there is little choice here at the moment. This is because of the very high chemical energy content of what are fossil fuels, providing sufficient traction to lift off and move through the air. A small nuclear reactor could be used to power aircraft but the effects of radiation on the crew and passengers would prohibit their use not to mention the radioactive contamination of the land if one were to crash.
To put transport energy into context, the graph below taken from Without the hot air by David MacKay shows the energy used to move passengers using various form of transport. His book is excellent on all modes of energy use and power generation and I would warmly recommend it to those wishing to look into the subject in more depth, the website has all the material that is in the book.
The same data is shown below along with walking and cycling. What is most striking to me from the data is that the large 4x4 car is up there with ocean liners, small jets and helicopters, it would leave me asking "could I get by with a smaller car and leave the 4x4's to the farmers."
|Mode||Occupancy||Fuel||Energy (kWh/ person-km)||Energy (kWh/ 100-person-km)|
|Motorised Bicycle||1||Food & Electricity||0.1||1|
|Large 4x4 Car||1||Diesel||1.1||110|
|Local Bus||Variable Average||Diesel||0.32||32|
|Transit (Metro,Tram)||Variable Average||Electricity||0.12||12|
|High Speed Train||Full||Diesel||0.09||9|
|High Speed Train||Full||Electricity||0.04||4|
|Small Jet (Learjet)||8 Passengers||Aviation turbine Fuel||1.5||150|
|Small Turboprop||6 Passengers||Aviation Spirit||0.6||60|
|Helicopter||Variable Average||Aviation Spirit||1.5||150|
|Jumbo Jet||Full||Aviation turbine Fuel||0.42||42|
|Sea Bus||Variable Average||Diesel||0.21||21|
In the next article we use the information on energy requirements for the various modes of transport to calculate the environmental consequences of using them in terms of the emissions of greenhouse gases.