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Alternate Energy. Energy Efficiency and Renewable Energy. Key Concepts. Energy efficiency. Solar energy. Types and uses of flowing water. Wind energy. Biomass. Geothermal energy. Use of hydrogen as a fuel. Decentralized power systems. The Importance of Improving Energy Efficiency.

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alternate energy

Alternate Energy

Energy Efficiency and Renewable Energy

key concepts
Key Concepts
  • Energy efficiency
  • Solar energy
  • Types and uses of flowing water
  • Wind energy
  • Biomass
  • Geothermal energy
  • Use of hydrogen as a fuel
  • Decentralized power systems
the importance of improving energy efficiency
The Importance of Improving Energy Efficiency
  • Energy efficiency
  • Net energy efficiency

Least Efficient

  • Incandescent lights
  • Nuclear power plants
  • Internal combustion engine
ways to improve energy efficiency
Ways to Improve Energy Efficiency
  • Cogeneration
  • Efficient electric motors
  • High-efficiency lighting
  • Increasing fuel economy
  • Alternative vehicles
  • Insulation
  • Plug leaks
hybrid and fuel cell cars
Hybrid and Fuel Cell Cars
  • Hybrid electric-internal combustion engine
  • Fuel cells
slide7

1

2

Hydrogen gas

3

4

H2

Cell splits H2 into protons

and electrons. Protons flow

across catalyst membrane.

3

1

O2

React with oxygen (O2).

2

Produce electrical

energy (flow of

electrons) to

power car.

4

H2O

Emits water

(H2O) vapor.

hybrid car
Hybrid Car

A

C

Electric motor

Traction drive provides additional power, recovers

breaking energy to recharge battery.

Combustion engine

Small, efficient internalcombustion engine powers

vehicle with low emissions.

D

B

Fuel tank

Liquid fuel such as gasoline,

diesel, or ethanol runs small

combustion engine.

Battery bank

High-density batteries power electric

Motor for increased power.

E

Regulator

Controls flow of power between electric

Motor and battery pack.

F

Transmission

Efficient 5-speed automatic transmission.

B

A

E

F

C

D

Fuel

Electricity

fuel cell car
Fuel Cell Car

Fuel cell stack

Hydrogen and oxygen combine

chemically to produce electricity.

Fuel tank

Hydrogen gas or liquid or solid metal hydride stored on board or made from gasoline or methanol.

A

C

D

B

Turbo compressor

Sends pressurized air to fuel cell.

E

Traction inverter

Module converts DC electricity from fuel

cell to AC for use in electric motors.

Electric motor/transaxle

Converts electrical energy to

mechanical energy to turn wheels.

B

A

E

C

D

Fuel

Electricity

slide10

Universal docking connection

Connects the chassis with the

Drive-by-wire system in the body

Body attachments

Mechanical locks

that secure the

body to the chassis

Rear crush zone

absorbs crash energy

Air system

management

Fuel-cell stack

Converts hydrogen

fuel into electricity

Drive-by-wire

system controls

Cabin heating unit

Side mounted radiators

Release heat generated

by the fuel cell, vehicle

electronics, and wheel

motors

Front crush zone

Absorbs crash energy

Hydrogen

fuel tanks

Electric wheel motors

Provide four-wheel drive

Have built-in brakes

slide11

1.4

1.2

Energy useper capita

1.0

Index of energy use per capita andper dollar of GDP (Index: 1970=1)

0.8

0.6

0.4

Energy useper dollar of GDP

0.2

0

1970

1980

1990

2000

2010

2020

Year

slide12

30

25

Cars

Average fuel economy

(miles per gallon, or mpg)

20

Both

15

Pickups, vans, and

sport utility vehicles

10

1985

1970

1975

1980

2005

2000

1990

1995

Model Year

slide13

2.2

2.0

1.8

1.6

Dollars per gallon (in 1993 dollars)

1.4

1.2

1.0

0.8

1920

1930

1940

1950

1960

1970

1980

1990

2000

2010

Year

using solar energy to provide heat
Using Solar Energy to Provide Heat
  • Passive solar heating
  • Active solar heating
slide15

Net Energy Efficiency

Super insulated house(100% of heat R-43)

98%

Geothermal heat pumps (100% of heating and cooling))

96%

Passive solar (100% of heat)

90%

Passive solar (50% of heat) plus high-

efficiency natural gas furnace(50% of heat)

87%

Natural gas with high-efficiency furnace

84%

Electric resistance heating (electricity from hydroelectric power plant)

82%

Natural gas with typical furnace

70%

Passive solar (50% of heat) plus high-efficiency wood stove (50% of heat)

65%

Oil furnace

53%

Electric heat pump (electricity

from coal-fired power plant)

50%

High-efficiency wood stove

39%

Active solar

35%

Electric heat pump (electricity

from nuclear plant)

30%

Typical wood stove

26%

Electric resistance heating (electricity

from coal-fired power plant)

25%

Electric resistance heating (electricity

from nuclear plant)

14%

slide23

Summer

sun

Heavy

insulation

Super window

Winter

sun

Super window

Stone floor and wall

for heat storage

PASSIVE

slide24

Heat to house

(radiators or

forced air duct)

Pump

Heavy

insulation

Hot

water

tank

Super-

window

Heat

exchanger

ACTIVE

slide27

R-60 or higher insulation

R-30 to

R-43 insulation

Small or no north-facing

windows or super windows

Insulated glass,

triple-paned or

super windows

(passive solar gain)

R-30 to

R-43 insulation

House nearly airtight

R-30 to R-43

insulation

Air-to-air

heat exchanger

slide28

Direct Gain

Ceiling and north wall

heavily insulated

Summer

sun

Hot air

Super

insulated

windows

Winter

sun

Warm

air

Cool air

Earth tubes

slide29

Greenhouse, Sunspace, or

Attached Solarium

Summer cooling vent

Warm air

Insulated

windows

Cool air

slide30

Earth Sheltered

Reinforced concrete,

carefully waterproofed

walls and roof

Earth

Triple-paned or

super windows

Flagstone floor

for heat storage

using solar energy to provide high temperature heat and electricity
Using Solar Energy to Provide High-Temperature Heat and Electricity
  • Solar thermal systems
  • Photovoltaic (PV) cells
solar energy calculation
Solar Energy Calculation
  • We live at about 40o N and receive about 600 W /m2
  • So over this 8 hour day one receives:
    • 8 hr x 600 W /m2 = 4800 W-hr /m2 = 4.8 kW-hr / m2
    • 4.8 kW-hr / m2 is equivalent to 0.13 gal of gasoline
    • For 1000 ft2 of horizontal area (typical roof area) this is equivalent to 12 gallons of gas or about 450 kW-h
slide35

Single Solar Cell

Boron-enriched

silicon

Sunlight

Junction

Cell

Phosphorus-

enriched silicon

DC electricity

slide36

Roof Options

Panels of

Solar Cells

Solar Cells

slide38

Trade-Offs

Solar Energy for High-Temperature

Heat and Electricity

Advantages

Disadvantages

Moderate net energy

Moderate environmental

Impact

No CO2 emissions

Fast construction (1-2 years)

Costs reduced with natural gas

turbine backup

Low efficiency

High costs

Needs backup or storage system

Need access to sun

most of the time

High land use

May disturb desert areas

producing electricity from moving water
Producing Electricity from Moving Water
  • Large-scale hydropower
  • Small-scale hydropower
  • Pumped-storage hydropower
  • Tidal power plant
  • Wave power plant
slide41

Trade-Offs

Large-Scale Hydropower

Advantages

Disadvantages

Moderate to high net energy

High efficiency (80%)

Large untapped potential

Low-cost electricity

Long life span

No CO2 emissions during operation

May provide flood control below dam

Provides water for year-round

irrigation of crop land

Reservoir is useful for fishing and recreation

High construction costs

High environmental impact from flooding land to form a reservoir

High CO2 emissions from

biomass decay in shallow tropical reservoirs

Floods natural areas behind dam

Converts land habitat to lake

habitat

Danger of collapse

Uproots people

Decreases fish harvest below dam

Decreases flow of natural fertilizer (silt) to land below dam

slide43

Gearbox

Electrical

generator

Power cable

Wind Turbine

basics of wind energy
Basics of Wind Energy
  • Velocity measured in meters per second (m/s)
  • Power is measured in Kilowatts (kW)
  • 1 m/s is a little more than 2 mile/hr (mph)
basics of wind energy1
Basics of Wind Energy
  • Kinetic Energy (of wind) is: 1/2 * mass * velocity2
  • KE = 1/2 mv2
  • The amount of air moving past a given point (e.g. the wind turbine) per unit time depends on the wind velocity.
  • Power per unit area = KE* velocity or P= mv2*v = mv3
  • So Power that can be extracted from the wind goes as velocity cubed (v3)
basics of wind energy2
Basics of Wind Energy
    • Power going as v3 is a big deal.
    • 27 times more power is in a wind blowing at
    • 60 mph than one blowing at 20 mph.
    • For average atmospheric conditions of density
  • and moisture content: Power /m2 = 0.0006 v3
sample wind problem
Sample Wind Problem
  • How much energy is there in a 20 mph wind?
    • 20 mph wind =10 m/s
    • Power = 0.0006 * v 3
    • Power = 0.0006 * (10) 3
    • Power = 0.0006 * 1000 = 0.6 kW/m2
    • Which is equal to 600 W/m2
    • This is identical to average solar power per square meter at our latitude.
sample wind problem1
Sample Wind Problem
  • Example calculation:
    • Windmill efficiency = 42%
    • Average wind speed = 10 m/s (20 mph)
    • Power * efficiency = 0.0006 x 1000 x 0.42 = 250 W/m2
    • 250 W/m2 / 1000 W/kW = 0.25 kW/m2
    • Electricity generated is then 0.25 kW-h/m2
    • If wind blows 24 hours per day then annual electricity generated would be about 2200 kW-h/m2
  • (0.25 kW-h/m2 x 24h/d x 365d/yr = 2190kW-h/m2 )
sample wind problem2
Sample Wind Problem
  • But, on average, the wind velocity is only this high about 10% of the time.
  • Therefore a typical annual yield is about 220 kW-h/m2
sample wind problem3
Sample Wind Problem
  • To Generate 10,000 kWh annual then from a 20 mph wind that blows 10% of the time
  • Windmill area = 10,000 kW-h/220 kW-h/m2= 45 /m2
    • Make a circular disk of diameter about 8 meters
    • This is not completely out of the question for some homes
    • Even a small windmill (2 meters) can be effective.
sample wind problem4
Sample Wind Problem
  • 20 mph 10% of the time      
  • 2500 kW-h annually
  • 40 mph 10% of the time      
  • 20000 kW-h annually
  • 20 mph 50% of the time      
  • 12500 kW-h annually
  • 4 small windmills at 20 mph 10% of the time      
  • 10000 kW-h annually
slide56

Trade-Offs

Wind Power

Advantages

Disadvantages

Moderate to high

net energy

High efficiency

Moderate capital cost

Low electricity cost

(and falling)

Very low environmental

impact

No CO2 emissions

Quick construction

Easily expanded

Land below turbines

can be used to grow

crops or graze livestock

Steady winds needed

Backup systems when

needed winds are low

High land use for wind farm

Visual pollution

Noise when located

near populated areas

May interfere in flights of migratory birds and kill

birds of prey

producing energy from biomass
Producing Energy from Biomass
  • Biomass and biofuels
  • Biomass plantations
  • Crop residues
  • Animal manure
  • Biogas
  • Ethanol
  • Methanol
slide58

Trade-Offs

Methanol Fuel

Advantages

Disadvantages

High octane

Some reduction in CO2 emissions

Lower total air

Pollution (30-40%)

Can be made from natural gas, agricultural

wastes, sewage sludge, and garbage

Can be used to produce

H2 for fuel cells

Large fuel tank needed

Half the driving range

Corrodes metal, rubber, plastic

High CO2 emissions if made

from coal

Expensive to produce

Hard to start in cold weather

slide59

Trade-Offs

Ethanol Fuel

Advantages

Disadvantages

High octane

Some reduction in CO2 emission

Reduced CO emissions

Can be sold as gasohol

Potentially renewable

Large fuel tank needed

Lower driving range

Net energy loss

Much higher cost

Corn supply limited

May compete with growing

food on cropland

Higher NO emission

Corrosive

Hard to start in

colder weather

slide60

Trade-Offs

Solid Biomass

Advantages

Disadvantages

Large potential supply in some areas

Moderate costs

No net CO2 increase if

harvested and burned

sustainably

Plantation can be located on

semiarid land not needed for

crops

Plantation can help restore

degraded lands

Can make use of agricultural,

timber, and urban wastes

Nonrenewable if harvested

unsustainably

Moderate to high environmental

impact

CO2 emissions if harvested

and burned unsustainably

Low photosynthetic efficiency

Soil erosion, water pollution, and loss of wildlife habitat

Plantations could compete with

cropland

Often burned in inefficient

and polluting open fires

and stoves

geothermal energy
Geothermal Energy
  • Geothermal heat pumps
  • Geothermal exchange
  • Dry and wet steam
  • Hot water
  • Molten rock (magma)
  • Hot dry-rock zones
the geysers geothermal site
The Geysers Geothermal Site
  • Covers an area of 70 square kilometers
  • Heat is recovered from the top 2.0 kilometer of crust
  • In this region the temperature is: 240 oC
  • The mean annual surface temperature is: 15 oC
  • The specific heat of the rock is: 2.5 J/cm3 oC
  • (specific heat is usually expressed in J/g oC)
  • Overall 2 % of the total available thermal energy in this region heats water for steam.
the geysers geothermal site1
The Geysers Geothermal Site
  • How many years can this source provide power for electricity generation at the rate of 2000 MW-yr?
    • (Total Capacity required is rate divided by efficiency)
    • Total Capacity required is 2000 MW-yr/0.02 = 100,000 MW-yr
    • 1 J/s = 1 W; 1 x 106 W = 1 MW; 1 yr = 3.15 x 107 s
    • 100,000 MW-yr = 1 x 105 MWyr
    • 1 x 105 MW-yr * 1 x 106 W/MW = 1 x 1011 W-yr
    • 1 x 1011 W -yr * 3.15 x 107 s/yr = 3.15 x 1018 W-s
    • = 3.15 x 1018 W-s * 1 J/ W-s = 3.15 x 1018 J (each year)
the geysers geothermal site2
The Geysers Geothermal Site
  • Volume of rock = 70 km2 x 2 km = 140 km3
  • Change in Temperature (D T) = 240 oC – 15 oC = 225 oC
  • Heat content (Q) = Volume * specific heat * D T
  • Q = 140 km3 * 1015 cm3/km3* 2.5 J/(cm3oC)*225oC
  • = 8x1019 J (Total Energy)
the geysers geothermal site3
The Geysers Geothermal Site
  • Hence the lifetime is:
  • Total Energy/ Energy used in a year = Lifetime of Energy Source
  • 8x10 19 J / 3.15 x 1018 J/yr = 26 yr
  • This shows that we can use this geothermal resource for 26 yr at that rate, after that it is used up.
geothermal power plants
Geothermal Power Plants

Dry Steam

Flash Steam

Binary Cycle

slide70

Geysers dry steam field,

in northern California

slide74

East Mesa, California

Flash Steam Plant

slide75

Hybrid Binary and Flash Plant

Big Island of Hawaii

slide78

Trade-Offs

Geothermal Fuel

Advantages

Disadvantages

Very high efficiency

Moderate net energy at accessible sites

Lower CO2 emissions than fossil fuels

Low cost at favorable sites

Low land use

Low land disturbance

Moderate environmental impact

Scarcity of suitable sites

Depleted if used too rapidly

CO2 emissions

Moderate to high local air pollution

Noise and odor (H2S)

Cost too high except at the most concentrated and accessible source

energy density of some materials
Energy Density of Some Materials
  • MaterialEnergy Density (kW-h/kg)
    • Gasoline 14
    • Lead Acid Batteries 0.04
    • Hydro-storage 0.3 / m3
    • Flywheel, Steel 0.05
    • Flywheel, Carbon Fiber 0.2
    • Flywheel, Fused Silica 0.9
    • Hydrogen 38
    • Compressed Air 2 / m3
the hydrogen revolution
The Hydrogen Revolution
  • Environmentally friendly hydrogen
  • Extracting hydrogen efficiently
  • Storing hydrogen
  • Fuel cells
the hydrogen revolution1
The Hydrogen Revolution

Primary Energy Sources

Hydrogen Production

Transport

Storage

Utilization

Photo-conversion

Sunlight

Electric utility

Wind

Electricity Generation

Commercial/Residential

Electrolysis

Vehicles and pipeline

Biomass

Transportation

Gas and solids

Reforming

Fossil fuels

Industrial

entering the age of decentralized micropower
Entering the Age of Decentralized Micropower
  • Decentralized power systems
  • Micropower systems
decentralized power systems
Decentralized power systems

Easy to repair

Much less vulnerable to power outages

Increase national security by dispersal of targets

Useful anywhere

Especially useful in rural areas in developing countries with no power

Can use locally available renewable energy resources

Easily financed (costs included in mortgage and commercial loan)

Small modular units

Fast factory production

Fast installation (hours to days)

Can add or remove modules as needed

High energy efficiency (60–80%)

Low or no CO2 emissions

Low air pollution emissions

Reliable

slide84

Wind farm

Bioenergy

Power

plants

Small solar cell

power plants

Fuel cells

Rooftop solar

cell arrays

Solar cell

rooftop systems

Transmission

and distribution

system

Commercial

Small

wind

turbine

Residential

Industrial

Microturbines

price comparison from 1998 study leveled costs includes start up costs
Price Comparison from 1998 Study       Leveled Costs: (includes start-up costs)
  • Wind: 4.3 cents per kWh
  • Coal: 6.2 cents per kWh
  • Photovoltaics: 16.0 cents per kWh
  • Advanced Gas Turbine: 4.6 cents per kWh
slide87

What Can You Do?

Energy Use ad Waste

  • Drive a car that gets at least 15 kilometers per liter (35 miles per gallon) and join a carpool.
  • Use mass transit, walking, and bicycling.
  • Super insulate your house and plug all air leaks.
  • Turn off lights, TV sets, computers, and other electronic equipment when they are not in use.
  • Wash laundry in warm or cold water.
  • Use passive solar heating.
  • For cooling, open windows and use ceiling fans or whole-house attic or window fans.
  • Turn thermostats down in winter and up in summer.
  • Buy the most energy-efficient homes, lights, cars, and appliances available.
  • Turn down the thermostat on water heaters to 43-49ºC (110-120ºF) and insulate hot water heaters and pipes.