THE SOURCE OF ALL ENERGY WEEK 3 lECTURE 3

Slide 1: 

Energy

Fundamental law: Conservation of energy: 

Fundamental law: Conservation of energy Manifestations: Work, motion, position, radiation (light), heat, chemical and nuclear energy, mass itself Sources: Petroleum, coal, moving water, nuclear, solar Uses: Transportation, generation of electricity, heating, cooling, lighting

Work : 

Work An applied force acting through a distance parallel to the force Units of work (and energy) = joule (J) Requires movement in same direction as force Zero distance, no work Displacement perpendicular to applied force, no work

Power : 

Power The rate at which work is done Units: watts (W), horsepower (hp) Example: Walking versus running upstairs The “power bill” - you pay for energy

Motion, position and energy: 

Motion, position and energy Work and energy related Energy = ability to do work Work = process of changing energy level Next: Relationship between work and energy associated with position Relationship between work and energy of motion

Potential energy: 

Potential energy Energy associated with position Gravitational potential energy Measuring h - need reference height Also: elastic (springs) and electric (charges) potential energy Work can change PE Kinetic energy can change into potential energy

Kinetic energy: 

Kinetic energy Energy associated with motion Results from work or change in potential energy Speed squared! (Double speed, KE increases by 4)

Energy forms: 

Energy forms Mechanical energy Kinetic plus potential energy Chemical energy Energy involved in chemical reactions Radiant energy Electromagnetic energy Visible light = small part Electrical energy Charges, currents, etc. (See Lecture 7) Nuclear energy Energy involving the nucleus and nuclear reactions

Energy conversion: 

Energy conversion Any form of energy can be converted into another form Energy flows from one form to another in natural processes Example - pendulum

Slide 10: 

DIFFERING FORMS OF ENERGY

Energy conservation : 

Energy conservation Energy is never created or destroyed Energy can be converted from one form to another but the total energy remains constant

Energy sources today: 

Energy sources today Primarily wood to coal to petroleum with increasing industrialization 89% can be traced to photosynthesis Uses 1/3 for heating 2/3 in engines and generators

Petroleum : 

Petroleum Oil from oil-bearing rock Organic sediments transformed over time by bacteria, pressure and temperature Natural gas formation similar, except at generally higher temperatures Petroleum and natural gas often found together Supplies are limited

Coal: 

Coal Accumulated plant materials, processed over time by pressure and temperature Progression: peat to lignite to sub-bituminous to bituminous Impurities Minerals lead to ash Sulfur leads to sulfur dioxide gas (pollutant) Petroleum, natural gas and coal = fossil fuels

Moving water: 

Moving water Renewable with rainfall Hydroelectric plants generate ~3% of US’s total energy consumption Growth potential limited by decreasing availability of new sites

Nuclear : 

Nuclear Based on nuclear fission reactions of uranium and plutonium Water heated in reactor and then used to produce steam to turn generating turbines Safety of nuclear power generation is controversial

Modern Solar Technologies: 

Modern Solar Technologies Solar Cells Polycrystalline compounds that generate electricity when exposed to light Power Tower Steam produced by focused sunlight generates electricity Passive Applications Natural energy flow without mechanical devices Active Applications Solar collector; sunlight heats air or liquid material Wind Energy Sunlight differentially heats earth’s surface creating winds Wind then generates electricity Biomass Utilizes material formed by photosynthesis Agriculture and Industrial Heating Utilizes sunlight rather than traditional energy sources Ocean Thermal Energy Conversion (OTEC) Generates electricity form the temperature difference between water depths

Geothermal Energy: 

Geothermal Energy Energy from beneath the earth’s surface Dry steam Hot water Hot dry rocks Geopressured resources Difficulty in obtaining and economically utilizing

Hydrogen: 

Hydrogen Used directly in fuel cell or burned to release heat Produces no pollutants Only emission is water Problem is that hydrogen does not exist on or under earth’s surface in usable amounts Must be obtained from chemical reaction