Energy Overview

Topics Covered Energy Resources and Consumption Energy Concepts Energy Forms Power Units Conversions Laws of Thermodynamics Energy Consumption History Industrial Revolution Exponential Growth Energy Crisis Present Global Energy Use Future Energy Needs

Energy Measures Joule (J) – basic unit of energy Amount of energy used when a 1-watt electrical device is turned on for 1 second Gigajoule (GJ) – 1 Billion (1x109) Joules 1 GJ = as much energy as 8 Gal of gasoline Exajoule (EJ) = 1 Billion (1x109) Gigajoules US uses “quad” = quadrillion Btu= 1.055 EJ Btu = British thermal unit = 1 Btu = 1055 J

Energy The ability to do work or transfer heat Most energy comes from the sun’s electromagnetic radiation (carried by photons) http://www.redorbit.com/education/reference_library/space_1/universe/2574668/electromagnetic_radiation/

Power Power is the rate at which work is done Energy = Power x time Power = Energy / time

Relationship to Joules Common Energy Units Unit Definition Relationship to Joules Common Uses calorie Amount of energy it takes to raise 1 gram of water 1 o C 1 calorie = 4.184 J Energy transfer in ecosystems, human food consumption Calorie Food Calorie – always shown with a capital C 1 Calorie = 1000 calories = 1 kilocalorie (kcal) Food labels, human food consumption British Thermal Unit (Btu) Amount of energy it takes to heat 1 lb of water 1 F 1 Btu = 1055 J Energy transfer in AC, home and water heaters Kilo-watt hour (kWh) Amount of energy expended by using 1 kilowatt of electricity for 1 hour 1 kWh = 3,600,000 J or 3.6 Megajoules (MJ) Electrical appliances, kWh per year

Relationship to Joules Unit Definition Relationship to Joules Common Uses Watt (thermal) Power produced as heat One joule of energy transferred or dissipated in one second (J/s) Nuclear power plants produce heat measured in thermal watts Watt (electrical) Power produced as electricity same Kilo =1,000 = 103 1 kW = 103watts Mega =1,000,000= 106 1 MW = 106watts

Energy Forms Mechanical Two types: potential and kinetic Thermal Description Mechanical Two types: potential and kinetic Thermal Heat is the internal energy in substances – the vibration and movement of the atoms and molecules within substances Chemical Stored in bonds between atoms in a molecule Electrical Results from the motion of electrons Nuclear Stored in the nuclei of atoms; it is released by splitting or joining atoms Electromagnetic Travels by waves

First Law of Thermodynamics Energy is neither created nor destroyed. (Just like matter) Ex: Potential energy in a piece of firewood is converted into heat energy.

Second Law of Thermodynamics When energy is transformed, the quantity of energy remains the same, but its ability to do work diminishes.

Entropy Second Law of Thermodynamics All Systems move toward randomness, unless new energy from an outside system is added Entropy – Randomness Your room! A log being burnt A pot of boiling water

Energy Efficiency Ratio of the amount of work that is done to the total amount of energy that’s introduced into the system initially. Ex: Fireplace that’s 70% efficient might use 2 kg of firewood to heat a room to 20˚C (68˚ F). A fireplace that’s 10% efficient would require 14 kg to reach 20˚C (68˚ F).

Energy Efficiency 2 Chemical energy  Electricity Coal-burning power plant can convert 1 metric ton of coal containing 24,000 megajoules (MJ) into 8400 MJ of electricity. 8400 MJ is 35% of 24,000 MJ, the process is 35% efficient. (65% is lost as heat) 10% is lost as heat and sound in powerlines – 90% efficient Incandescent bulbs are 5% efficient. Total energy efficiency: .35 x .90 x .05 = .016  1.6% efficient Coal  Electricity x Transport x light bulb efficiency = overall efficiency

Energy Quality The ease at which an energy source can be used for work. High-quality energy source has a convenient, concentrated form. Ex: Gasoline is good quality because it’s concentrated 44 MJ/kg and easy to convert to work Wood 20 MJ/kg more difficult to convert to work

Energy Use Americans use 10,000 watts of energy continuously 24/365 Most of our energy comes from nonrenewable sources (finite) 2 Types Fossil Fuels – ancient solar energy stored in chem. Bonds is burned and harness heat energy Nuclear – Radioactive Materials

Pre-Industrial Revolution: Wood Industrial Revolution: Coal Middle of 20thCentury: Petroleum Late 20thCentury: Natural Gas and Coal

Worldwide Energy Use Each Country is Different – Use based on: What’s available What’s affordable Environmental Impacts (Developed Countries) World Use = 495 EJ per year 75 GJ per person per year 3 largest sources - oil, coal and natural gas

Developed and cities of developing countries – use fossil fuels Developing rural areas still use wood, charcoal and animal waste Commercial Energy Sources – Bought and sold such as coal, oil and natural gas. Sometimes wood, charcoal and animal waste Subsistence Energy sources – gathered by individuals for their own immediate needs

US Energy Use Patterns US has greatest total energy consumption Canada greatest energy per capita

Energy Types and Quality Best suited for purposes based on Energy-to-mass ratio Speed at which they provide/cut off the energy supply Run a car on coal or firewood? Why or why not?

Quantifying Energy Efficiency 2 Processes Obtaining the fuel Converting the fuel into work Energy Return on Energy Investment – EROEI EROEI = Energy obtained from the fuel / Energy invested to obtain the fuel Ex: To obtain 100 J of coal from a surface coal mine, 5 J of energy is expended 100 J/5 J = 20

Efficiency and Transportation 30% of Energy use in the US is for transportation (movement of people and goods) and uses petroleum Public ground transportation is more efficient than traveling with one person in a car and air travel. Energy expended for different modes of transportation in the US Mode MJ per passenger-kilometer Air 2.1 Passenger Car (driver alone) 3.6 Motorcycle 1.1 Train (Amtrak) Bus 1.7

Transportation Contd ½ of all personal vehicles sold are mini-vans, SUVs and pick-up trucks (AKA light trucks) Poor gas mileage – 20 mpg Small cars – 45 mpg 2-3% are hybrids – 50 mpg

Electricity Generation by coal, natural gas, or wind No pollutants emitted when used Pollutants released when fossil fuels are burned More efficient to transfer to home directly – least transfers – most efficient

Grid A network of interconnected transmission lines Connects power plants and links with users

Electricity Efficiency Coal burning – 35% efficient Gas combustion – Combined cycle natural gas – 60% efficient Gas combustion turns first turbine and steam from excess heat turns second turbine Typical US power plants have 500 megawatt capacity (max output) Capacity Factor – Fraction of time a plant is operating