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Energy: What it is, how we use it, how we waste it

Which would you prefer to do?

Stick your hand in boiling water or steam?

What is “Energy?”

Energy is the amount of work a physical system is capable of performing so energy can be defined as that which changes the position, physical composition or temperature of an object

Energy comes in many flavorsForm What it is or does Example

Mechanical Motion: kinetic or potential

Moving car, coyote poised to fall

Chemical Potential energy in molecular bonds

Fossil fuels, food, explosions

Thermal Internal temp. of substances

Hot water, steam, body temperature

Electrical Electrons moving across potentials

Electric circuits, batteries, fuel cells

Radiant Electromagnetic light, heat

Sunlight, heat emitted by objects

Nuclear Potential energy in atomic nucleus

Nuclear fission & fusion

Gravitational Energy of place or position

Hydroelectricity, falling coyote

We tend to transform energy in order to make it usable

• We burn fossil fuels to generate usable heat energy to make steam to turn electrical turbines

•We split atomic nuclei to do the same thing

•We burn gasoline to create energetic gases that push pistons in internal combustion engines

•We transform liquids and gases moving at high velocities into rotational kinetic energy that turns shafts for various purposes

Energy is measured in many different units

Kilowatt-hours Barrels

Gallons

Therms

BTUs

CaloriesKilocalories (equals

one food calorie

Energy densities vary a great deal

•90 lbs of butuminous coal and lignite production

•125 lbs of oven-dried wood

•8 gallons of gasoline (enough to move an average passenger car ~150-200 miles)

•10 therms of dry natural gas

•11 gallons of propane

•2 months of dietary intake of a laborer

•20 cases (240 cases) of table wine

1 milllion BTU equals approximately:

You are a lightbulb (not a walrus), and as much as 10 “C” batteries

Power is a measure of the rate of energy production and consumption

A typical 100 watt light bulb consumes 100 watts of energy per hour (0.1 kWh)

A standard 1 GWe (gigawatt) nuclear power plant generates a billion watts of electrical energy per hour (1 million kilowatt-hrs)

A 150 horsepower car that gets 30 mpg, driven at 60 mph, consumes 2 gal/hr of gasoline; 2 gallons of gasoline contain about 73 kWh or 98 hp-hr of energy.

To use energy more efficiently, it helps to match power rates to requirements

Because an automobile has highly variable power requirements—from 1 mph to bursts of 80 mph, it requires a high peak power capacity—which is difficult to provide with electricity and which tends to lower the efficiency of energy use

By contrast, a vehicle that only needs a maximum speed of 30 mph also requires much variability in velocity and acceleration rates, and less peak power capacity (that is why hybrids rely much more on electric power system for local travel)

Meanwhile, we value energy for the services it can provide, not for its specific form

We burn fuel at 1,000+ degrees to boil water at 212° to make a hot drink at 120° which we radiate as body heat at 98.6°

Basic principle of energy use:

we take high quality energy sources, use them to do work for us, and degrade them into lower-

quality heat

Someday, all energy sources in the universe will probably dissipate as very low quality “heat”

House as an energy eco-system: energy goes in, does work, becomes heat, and escapes at <70°

There are various ways to increase the efficiency of energy use on both supply and demand sides:

•in the generation process;

•in matching source to need (e.g., solar for heating water & space);

•in more efficient combustion & distribution systems;

•in demand reduction through more efficient appliances, insulation, leak reduction, etc.

Houses are only one type of “energy ecosystem”

1. Set your thermostat lower2. Don’t heat the whole house 3. Wash cloths with the Cold/Cold setting and use full loads 4. Unplug computers, TV’s, Cable boxes, and other “energy vampire”

appliances when not in use 5. Turn off the lights when you leave the room 6. Take shorter showers 7. Trim those bushes on the south side of your home and open the

shades 8. Adjust water heaters down to 126 degrees 9. Clean heater and refrigerator filters & vents to maximize

performance 10. Cook more efficiently

Saving energy in the household

What is your consumption profile?