Fuel Choices Flashcards
What is a fuel?
A fuel is a substance with stored energy that can be released relatively easily ( through a combustion reaction) for use as heat or power.
What are the different forms of energy?
Potential energy (energy that is stored in chemical bonds) or kinetic energy(energy associated with movement.
Total energy of an object?
The sum of its potential and kinetic energy
What is the law of conservation of energy?
Energy is neither created nor destroyed, it simply changes from one form into another. When this happens the total quantity of energy remains the same.
Second law of thermodynamics?
The quality of usability of energy gets worse because whenever energy is converted from one form to another, low temperature heat is also produced which is difficult to use again.
What is a fossil fuel?
A fuel that has been produced over a long time by the breakdown of organic material. This process can take many thousands of years.
Examples of fossil fuels
Coal crude oil and natural gas.
Why is there a push in society to reduce our dependence on fossil fuels?
- Increasing concern over the effects of gases released into the atmosphere by the combustion of fossil fuels. In particular, CO2 is believed to contribute to atmospheric warming (the greenhouse effect) and SO2 is known to cause acid rain.
- They are a non renewable energy resource, they are used up faster than they can be produced and are limited supplies so they will not be able to meet the long term energy needs of society.
Why can chemical energy in fossil fuels be considered trapped solar energy?
Fossil fuels retain the chemical energy they stored from photosynthesis while living
Why does black coal have a higher heat value than brown coal and is a better fuel?
Black coal contains less water and has a higher carbon content. When coal is burnt, the energy released causes water to vaporise, reducing net amount of heat released.
What observations indicate coal station is inefficient?
LOSS OF HEAT ENERGY AS STEA, IS SEEN rising from cooling tower
What is crude oil made of?
Mixture of hydrocarbon molecules that are members of the homologous series of alkanes.
Process of extracting crude oil?
The process of separating compounds by using their small differences in their boiling temperatures is called fractional distillation and is carried out in a fractionating tower.
LPG constituents??
Propane and butane
Disadvantage of using LPG?
Engine conversion required (expensive), large tanks are required, must have high pressure to see the gas in liquid form, risk of explosion is higher.
Natural gas constituents?
Mainly methane with small amounts of other hydrocarbons such as ethane and propane. Used for home heating and cooking
What is coal seam gas?
When natural gas is found in coal deposits where it is bonded to the surface of the coal.
What is shale gas?
Where natural gas is trapped in shale rock
Difference in coal power plant and gas fired power station?
steam is not used for spinning turbines in a gas fired power station. Instead hot gases from combustion expand air in a combustion turbine, spinning propeller like bladed attached generator. amount of co2 released is half that of coal fired power plants.
Non renewable sources definition
Those that are used at a rate faster than they can be replaced.
Renewable resources defintion
They are continually being replaced by natural processes within a relatively short period of time
Sustainable definition
Sustainable is able to support energy and resources into the future without depletion. A sustainable energy future means providing for the needs of today’s society without compromising the ability of future generations to meet their own needs.
What are biofuels?
Fuels derived from biological materials or biomass.
Why can biofuels be considered to be carbon neutral?
As all these fuels are produced naturally, it is considered that the use of these fuels will not contribute to atmospheric carbon dioxide. In order to produce the fuels, plants have photosynthesised and removed some atmospheric carbon dioxide to produce glucose. Burning biofuels simply replaces the carbon dioxide and thus biofuels can be considered carbon neutral.
Why are biofuels actually not carbon neutral?
However when sourcing plants to be used as fuels, energy is needed in growing and harvesting them. This energy production produces greenhouse gases.
Land issues with biofuels?
To produce biofuels, land used can be either for fuels or crops, not both.
Biogas composition?
Gaseous mixture of methane and co2. Generated when organic wastewater is digested an eraobically by the action of microorganisms
Biodiesel
Manufactured from vegetable oil or animal fat, produce by a reaction between vegetable oils (esters) and an alcohol, usually methanol.
Comparison sources
p: produced from crude oil
B: produced by reaction of vegetable oils from plant matter with alcohols
Chemical structure comparison
P:non polar molecules with only dispersion forces between them, hence lower melting point and viscosity than biodiesel
B: Polar ester link causes stronger intermolecular forces to exist, dipole dipole, resulting in higher melting point and viscosity than petrodisel
Flow along fuel lines
P:flows better at low temperatures than biodiesel as less viscous, because the molecules are smaller and non polar with weaker dispersion forces between them/
B: does not flow as well in cold climates and at low temperatures due to higher viscosity resulting from the stronger dipole dipole forces between he polar ends of the molecules
Hygroscopic properties?
Biodiesel is hygroscopic so it absorbs water in storage due to polar ends of biodiesel molecules, reducing efficiency with which it burns
Environmental impacts of petrodisel
Energy is used when extracting and producing these fuels. The greenhouse gases co2 and h2o are released in this process, greenhouse gases are also emitted when the fuels are combusted
Environmental impacts of biodiesel
Although the production process may result in the generation of greenhouse gases, biodiesel is more carbon neutral beteecause Co2 and h2O released on combustion are converted by photosynthesis into more plant matter
