XVI - Energy Efficiency & Renewable Energy Resources

Question 1

Energy Efficiency

Answer 1

the percentage of total
energy input that does
useful work in an
energy conversion
system

Question 2

Energy efficiency examples

Answer 2

fuel cell 60%
steam turbine 45%
human body 20-25%
fluorescent light 22%
internal combustion engine 10%
Incandescent light 5%

Question 3

Net energy efficiency

Answer 3

determined by the efficiency of each step

in the energy conversion process

Question 4

Net energy efficiency in passive solar

Answer 4

sunlight 100%
10% waste hear
90% transmission

Question 5

Net energy efficiency in uranium

Answer 5

uranium

Question 6

Energy waste

Answer 6

43% of the energy
used in the U.S. is
unnecessarily wasted
by using inefficient
methods to produce
electricity, heat our
homes, & drive our
cars

Question 7

What is the importance of reducing energy

Answer 7

• nonrenewable fuels last longer
• time to phase in renewable energy resources
• decrease dependence on oil imports
• reduce local & global environmental damage
• slow global warming
• save money

Question 8

Ways to improve energy efficiency

Answer 8

Cogeneration
Energy conservation & use of energy efficient lighting & appliances
Better insulated homes
Increases in fuel efficiency of motor/ use of alternative fuel vehicles

Question 9

Passive solar heating

Answer 9

Sunlight is captured
directly within a
structure & converts it
into low–temperature
heat for space heating

Question 10

Where is heat released throughout the day?

Answer 10

Heat is stored in walls &
floors made of materials
like concrete, brick,
stone, or tires & is
released slowly
throughout the day

Question 11

Where can passive solar & superinsulated design the cheapest?

Answer 11

A passive solar &
superinsulated design
is the cheapest way to
heat a home in regions
where sunlight is
available more than
60% of daylight hours.

Question 12

Active solar heating

Answer 12

solar collectors absorb
solar energy & a fan or
pump supplies the
building’s space or
water heating needs

Question 13

Pros solar heating

Answer 13

• solar energy is free
• net energy yield is high for
passive & moderate for
active
• technology is well
developed & easily
installed
• takes up little land space
• does not emit polluting or
greenhouse gases

Question 14

Cons solar heating

Answer 14

• need to secure solar
rights
• solar collectors are
ugly to some people
• active systems are
costly

Question 15

How can solar energy be used to produce electricity?

Answer 15

Converted directly into electrical energy by photovoltaic cells
Sunlight striking silicon atoms creates an electrical current
Stored in batteries

Question 16

Components of solar energy

Answer 16

Power lines
Photovoltaic panels
Inverter
To breaker panel
Battery bank

Question 17

Inverter

Answer 17

Converts DC to AC

Question 18

Battery bank

Answer 18

located in shed outside house due to explosive nature of battery gases

Question 19

Mass generation of solar energy

Answer 19

Solar tower power

Solar thermal plant

Question 20

Methods of producing electricity from water

Answer 20

Hydroelectric dams
Tides & waves
Ocean thermal energy conversion & solar ponds

Question 21

Pros of hydropower

Answer 21

No emission/ pollution
High net energy yields for dams
Moderate yields for ponds

Question 22

Cons of hydropower

Answer 22

Flood upstream habitats & alter downstream habitats
Limited areas
Thermal energy from bodies of water can’t compete economically

Question 23

Pros producing energy from wind

Answer 23

• unlimited source of energy at favorable sites
• moderate to high net energy yield
• easy to build & expand
• emit no pollutants or greenhouse gases
• land can also be used for agriculture

Question 24

Cons producing energy from wind

Answer 24

• economical only in areas with steady winds
• back–up energy sources are necessary
• mass production takes up a great deal of land
space
• noise pollution
• may interfere with migrating birds

Question 25

Using wood pros

Answer 25

• a potentially renewable
energy resource
• high net energy yield if
burned near source

Question 26

Using wood cons

Answer 26

• currently exploited
in nonrenewable &
unsustainable ways
• single–species
biomass plantations
reduce biodiversity
• burning wood
produces air
pollutants such as
particulates

Question 27

What can be considered as biomass?

Answer 27

Wood
Charcoal
Agricultural waste
Timbering wastes
Animal waste
Aquatic plants
Urban wastes

Question 28

What can energy be produced from biomass?

Answer 28

Direct burning

Conversions to gaseous & liquid biofuels

Question 29

Gaseous biofuels

Answer 29

Synthetic natural gas

Wood gas

Question 30

Liquid biofiels

Answer 30

Ethanol
Methanol
Gasinol

Question 31

Solar hydrogen revolution

Answer 31

Producing energy using combustion of water

Question 32

The benefit of using hydrogen

Answer 32

• the source of hydrogen, water, is plentiful
• when burned, hydrogen produces no carbon dioxide,
but instead water vapor & nitrogen oxides
• using hydrogen for fuel would eliminate most air
pollution problems & reduce greenhouse gas emissions

Question 33

The problem

Answer 33

• hydrogen is really only a way to store energy; requires
energy source to split hydrogen from water
• currently nonrenewable energy sources are used to
produce hydrogen, negating many benefits

Question 34

Solution

Answer 34

• use renewable sources of energy, most notably solar,
to produce hydrogen for combustion
• currently it costs more to use solar energy than other
energy sources, but could be phased in over time