ENERGY• Energy is the ability to do work and transfer heat.– Kinetic energy – energy in motion• heat, electromagnetic radiation

– Potential energy – stored for possible use• batteries, fuels, glucose molecules

• Energy Quality– measure of an energy source’s ability to do useful

work• High quality (concentrated)• Low quality (dispersed)

Fig. 2-13, p. 44

Low-temperature heat (100°C or less) for space heating

Moderate-temperature heat (100–1,000°C) for industrial processes, cooking, producing

steam, electricity, and hot water

Very high-temperature heat (greater than 2,500°C) for industrial processes and producing electricity to run electrical devices (lights, motors)

Mechanical motion to move vehicles and other things) High-temperature heat (1,000–2,500°C) for industrial processes and producing electricity

Dispersed geothermal energyLow-temperature heat (100°C or lower)

Normal sunlightModerate-velocity windHigh-velocity water flowConcentrated geothermal energyModerate-temperature heat

(100–1,000°C)Wood and crop wastes

High-temperature heat (1,000–2,500°C)Hydrogen gasNatural gasGasolineCoalFood

ElectricityVery high temperature heat (greater than 2,500°C)Nuclear fission (uranium)Nuclear fusion (deuterium)Concentrated sunlightHigh-velocity wind

Source of Energy RelativeEnergy Quality

(usefulness)

Energy Tasks

U.S. Energy Flow - 2008

Source: Energy Information Administration / Annual Energy Review 2008 (in quadrillion Btu) http://www.eia.doe.gov/overview_hd.html

40.18

ENERGY LAWS: Two Rules We Cannot Break

• First law of thermodynamics: – We cannot create or destroy energy.• We can change energy from one form to another.

• Second law of thermodynamics: – Energy quality always decreases.• When energy changes from one form to another, it is

always degraded to a more dispersed form.• Energy efficiency is a measure of how much useful

work is accomplished before it changes to its next form.

Fig. 2-14, p. 45

Chemicalenergy(food)

Solarenergy

WasteHeat

WasteHeat

WasteHeat

WasteHeat

Mechanicalenergy

(moving,thinking,

living)

Chemical energy

(photosynthesis)

Energy Efficiency

“A measure of how much useful work is accomplished by a particular input of energy into a system.”

• can be technologically improved in some systems• can be calculated

Environmental Impact and Energy Laws

• High-Throughput Economies: – Convert energy and material in a manner that

promotes waste and pollution.

Recycleand

reuse

Low-quality Energy(heat)

Waste and

pollutionPollutioncontrol

Sustainable low-waste economyWaste

and pollution

Matter Feedback

Energy Feedback

Inputs (from environment)

Energyconservation

Matter

Energy

SystemThroughputs

Outputs(into environment)

• Matter-Recycling-and-Reuse Economies:– Mimics nature by recycling and reusing, thus reducing pollutants and

waste.

Sustainable Low-Throughput Economies: