Nonrenewable Energy Resources All energy use has consequences

NONRENEWABLE RESOURCES= ONCE THEY ARE USED UP, THEY CANNOT BE REPLENISHED • Minerals • Fossil Fuels • Nuclear Fuels

Fossil Fuels Nuclear Fuels • Biological material that became fossilized millions of years ago • Radioactive materials that give off energy – Coal – Oil – Natural Gas • To access the energy contained in the chemical bonds, we burn these fuels & harness the heat energy • We harness the energy by transferring heat, just like with fossil fuels

Worldwide Energy Use • Basic unit of energy= joule (J) – 8 gallons of gasoline= 1 x 109 J (1 bill. Joules) – I gigajoule (GJ)= 1 billion joules – 1 exajoule (EJ)= 1 billion GJ Energy sources used in US & worldwide, in order of increasing importance= #1 Oil #2 Coal #3 Natural Gas

Commercial Energy Sources Subsidence Energy • Those that are bought and sold • Those gathered by individuals for their own needs • Rural areas of developing countries use wood, charcoal or animal waste for energy – Coal, oil, natural gas • Developed countries & some urban developing countries they use coal, oil & natural gas for electricity generation

Energy Consumption in the US since 1850

Energy use in U. S. • Midwest & southeast: coal primarily burned for electricity • West & northeast: use a mix of nuclear fuel, natural gas & hydroelectric dams • Highly populated areas tend to use less coal because it creates the most air pollution of any fuel • Northern areas use more oil & natural gas during winter months, southern areas consume more during summer months. • Type of energy used depends on ease of transportation and the amount of energy a given mass of fuel contains

The US produces 70% of its energy needs What we produce Where the energy is being used

Quantifying Energy Efficiency • The efficiency of obtaining the fuel • The efficiency of the process that converts it into the work that is needed – 2 nd Law of Thermodynamics: when energy is transformed, some of the energy is lost

• Every energy source, from coal to oil to wind, requires an expenditure of energy to obtain it. • The most direct way to account for energy required to produce a fuel is energy return on energy investment (EROEI) – EROEI= Energy obtained from the fuel___ Energy invested to obtain the fuel • Ex. In order to obtain 100 J of coal from a surface coal mine, 5 J of energy is expended. Therefore, EROEI= 20 J • A larger value for EROEI suggests a more efficient & more desirable fuel source

Efficiency of Transportation

Overall fuel efficiency of U. S. automobiles

Fuel efficiency Type of vehicle Miles per gallon on the highway Light trucks Small cars 20 45 Hybrid cars 50 Electric cars & plug-in hybrid Most efficient electric cars

ELECTRICITY GENERATION

• Coal, oil, and natural gas are primary sources of energy • Electricity if a secondary source of energy, meaning that we obtain it from the conversion of a primary source • Electricity is an energy carrier: something that can move & deliver energy in a convenient, usable form to end users • 40% of the energy used in the U. S. is used to generate electricity • However, because of lost energy, only 13% is available for end use! – 35% efficient

• Electricity can be produced by conversion of coal, natural gas, or wind, just to name a few. • Electricity is clean at the point of use – No pollutants are emitted in your home when you use the electricity • However, when it is produced from fossil fuels, pollutants are released • It is only 35% efficient but it is convenient

• 1. Fuel (coal, n. gas, wind) is delivered to a boiler, where it is burned • 2. Burning fuel transfers energy to water, which becomes steam. • 3. The kinetic energy contained within steam is transferred to the blades of a turbine – Turbine= a large device that resembles a fan or a jet engine

• 4. As the energy in the steam turns the turbine, the shaft in the center of the turbine turns the generator, which generates electricity. • 5. The electricity generated is transported along a network of interconnected transmission lines known as an electrical grid, which connects power plants together and links them with homes, businesses, factories, etc. , where it is converted into heat energy for cooking, kinetic energy in motors, radiant energy in lights, or used to operate electronic & electrical devices

• 6. The water used in the generation of electricity is sometimes cooled in a cooling tower or discharged into a nearby body of water. – Thermal pollution • Lowers the amount of dissolved oxygen

Electricity plants • They are not operational 24 hrs/day, 365 days/year – Have to be shut down for maintenance, refueling or repairs • When its time to start them up again, nuclear & coal-fired plants may take a number of hours or even a full day to reach full generation capacity – For this reason, electric companies tend to keep them running at all times

Energy math problem • If a power plant created 500 megawatts (MW) in an hour, then… – In a day it would generate 500 MW x 24 hrs= 12, 000 megawatt-hours (MWh) • Most home electricity is measured in kilowatthours (k. Wh) – 12, 000 MWh= 12, 000 k. Wh

Power vs Energy • Power measures the rate at which energy is being used • Units of power (equal to joules/sec): – Kilowatt – BTU • Unit of energy: – Joule • Energy is what you deliver and power is the rate at which you deliver it – The power rating of different appliances tells you how fast they consume this energy. A 100 watt bulb will use energy at a faster rate than a fluorescent bulb that has a power rating of 10 watts.

Cogeneration • The use of a fuel to generate electricity and produce heat is known as cogeneration – A method for obtaining greater efficiencies • Instead of releasing heat energy through cooling tower or flue gas, the heat energy is sent to nearby facilities to be used for water or space heating • Cogeneration= 90% efficient • Steam heating alone= 75% • Electricity generation alone= 35%

Trigeneration

Fuels used for electricity generation in the United States