alternate energy

Alternate EnergyAlternate EnergyEnergy Efficiency and

Renewable Energy

Key ConceptsKey Concepts

Energy efficiencyEnergy efficiencySolar energySolar energyTypes and uses of flowing waterTypes and uses of flowing waterWind energyWind energyBiomassBiomassGeothermal energyGeothermal energyUse of hydrogen as a fuelUse of hydrogen as a fuelDecentralized power systemsDecentralized power systems

The Importance of Improving Energy EfficiencyThe Importance of Improving Energy Efficiency

Energy efficiency Energy efficiency

Net energy efficiency Net energy efficiency

Least EfficientLeast Efficient Incandescent lights Incandescent lights

Internal combustion engine

Internal combustion engine

Nuclear power plants Nuclear power plants

Energy EfficienciesEnergy Efficiencies

Ways to Improve Energy EfficiencyWays to Improve Energy Efficiency

CogenerationCogenerationEfficient electric motorsEfficient electric motorsHigh-efficiency lightingHigh-efficiency lightingIncreasing fuel economyIncreasing fuel economyAlternative vehiclesAlternative vehiclesInsulation Insulation Plug leaksPlug leaks

Hybrid and Fuel Cell CarsHybrid and Fuel Cell Cars

Hybrid electric-internal combustion engine Hybrid electric-internal combustion engine

Fuel cells Fuel cells

1

2

3

4

1

2

3

4

H2

O2

H2O

Hydrogen gas

Emits water (H2O) vapor.

Produce electrical energy (flow of electrons) to power car.

React with oxygen (O2).

Cell splits H2 into protonsand electrons. Protons flowacross catalyst membrane.

ElectricityFuel

Combustion engineSmall, efficient internalcombustion engine powersvehicle with low emissions.

A Fuel tankLiquid fuel such as gasoline, diesel, or ethanol runs small combustion engine.

B

Electric motorTraction drive provides additional power, recoversbreaking energy to recharge battery.

C

Battery bankHigh-density batteries power electricMotor for increased power.

D

RegulatorControls flow of power between electricMotor and battery pack.

E

TransmissionEfficient 5-speed automatic transmission.

FA

B

C

D

EF

Hybrid CarHybrid Car

A

C

E

D

B

ElectricityFuel

A Fuel cell stackHydrogen and oxygen combinechemically to produce electricity.

B Fuel tankHydrogen gas or liquid or solid metal hydride stored on board or made from gasoline or methanol.

C Turbo compressorSends pressurized air to fuel cell.

D Traction inverterModule converts DC electricity from fuelcell to AC for use in electric motors.

E Electric motor/transaxleConverts electrical energy to mechanical energy to turn wheels.

Fuel Cell CarFuel Cell Car

Fuel-cell stackConverts hydrogenfuel into electricity

Front crush zoneAbsorbs crash energy

Electric wheel motorsProvide four-wheel driveHave built-in brakes

Hydrogenfuel tanks

Air systemmanagement

Body attachmentsMechanical locksthat secure thebody to the chassis

Universal docking connectionConnects the chassis with the Drive-by-wire system in the body

Rear crush zoneabsorbs crash energy

Drive-by-wiresystem controls

Side mounted radiatorsRelease heat generatedby the fuel cell, vehicleelectronics, and wheelmotors

Cabin heating unit

Year

1970 1980 1990 2000 20100

0.2

0.4

0.6

0.8

1.0

1.2

Ind

ex o

f en

erg

y u

se p

er c

apit

a an

dp

er d

olla

r o

f G

DP

(In

dex

: 19

70=

1)

2020

1.4

Energy useper dollar of GDP

Energy useper capita

30

25

20

15

10

1970 1975 1980 1990 2000 2005

Model Year

Av

era

ge

fu

el e

co

no

my

(mile

s p

er

ga

llon

, or

mp

g)

Cars

Both

Pickups, vans, andsport utility vehicles

1985 1995

Year1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

Do

llars

per

gal

lon

(in

199

3 d

olla

rs)

Using Solar Energy to Provide HeatUsing Solar Energy to Provide Heat

Passive solar heatingPassive solar heatingActive solar heatingActive solar heating

Net Energy Efficiency98%

96%

90%

87%

82%

70%

65%

53%

50%

39%

35%

30%

26%

25%

14%

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

Passive solar (100% of heat)

Passive solar (50% of heat) plus high-efficiency natural gas furnace(50% of heat)

Natural gas with high-efficiency furnace

Electric resistance heating (electricity from hydroelectric power plant)

Natural gas with typical furnace

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

Oil furnace

Electric heat pump (electricity from coal-fired power plant)

High-efficiency wood stove

Active solar

Electric heat pump (electricity from nuclear plant)

Typical wood stove

Electric resistance heating (electricity from coal-fired power plant)

Electric resistance heating (electricity from nuclear plant)

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

84%

1 ft2 of collector = 1 gallon of hot water 1 person uses about 20 gallons/day

Active and Passive Solar House in Belmont NY (upstate west of Alfred NY)

Passive Thermal Mass House

Passive Solar Heater

PASSIVE

Stone floor and wallfor heat storage

Super window

Wintersun

Summersun

Super window

Heavyinsulation

Hotwatertank

Pump

Heatexchanger

Super-window

Heat to house(radiators orforced air duct)

ACTIVE

Heavyinsulation

R-30 toR-43 insulation

Insulated glass,triple-paned orsuper windows(passive solar gain)

R-30 to R-43insulation

Air-to-airheat exchanger

House nearly airtight

R-30 toR-43 insulation

Small or no north-facingwindows or super windows

R-60 or higher insulation

Direct GainCeiling and north wall heavily insulated

Hot air

Super insulated windows

Cool air

Warmair

Summersun

Wintersun

Earth tubes

Greenhouse, Sunspace, orAttached Solarium

Summer cooling vent

Warm air

Cool air

Insulatedwindows

Earth Sheltered

Earth Triple-paned or super windows

Flagstone floorfor heat storage

Reinforced concrete,carefully waterproofedwalls and roof

Using Solar Energy to Provide High-Temperature Heat and ElectricityUsing Solar Energy to Provide High-Temperature Heat and Electricity

Solar thermal systems Solar thermal systems

Photovoltaic (PV) cells Photovoltaic (PV) cells

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

Solar Energy CalculationSolar Energy Calculation

Photovoltaic Array

Single Solar Cell

Boron-enrichedsilicon

Junction

Sunlight

Cell

Phosphorus-enriched silicon

DC electricity

Roof Options

Solar CellsPanels of Solar Cells

Solar Cell Roof

Moderate net energy

Moderate environmentalImpact

No CO2 emissions

Fast construction (1-2 years)

Costs reduced with natural gasturbine backup

Low efficiency

High costs

Needs backup or storage system

Need access to sunmost of the time

High land use

May disturb desert areas

Advantages Disadvantages

Trade-Offs

Solar Energy for High-TemperatureHeat and Electricity

Solar Steam Generator Barstow, California

Producing Electricity from Moving WaterProducing Electricity from Moving Water

Large-scale hydropower Large-scale hydropower

Small-scale hydropower Small-scale hydropower

Pumped-storage hydropower Pumped-storage hydropower

Tidal power plant Tidal power plant

Wave power plant Wave power plant

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-roundirrigation 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


Trade-Offs

Large-Scale Hydropower

Producing Electricity from WindProducing Electricity from Wind

Wind Turbine

Power cable

Electricalgenerator

Gearbox

•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 EnergyBasics 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)


•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


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 ProblemSample 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 )


•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


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.


•20 mph 10% of the time 2500 kW-h annually



•4 small windmills at 20 mph 10% of the time

10000 kW-h annually


Wind Farm

Moderate to highnet energy High efficiency

Moderate capital cost

Low electricity cost(and falling)

Very low environmentalimpact

No CO2 emissions Quick construction Easily expanded

Land below turbinescan be used to growcrops or graze livestock

Steady winds needed

Backup systems whenneeded winds are low

High land use for wind farm

Visual pollution

Noise when locatednear populated areas

May interfere in flights of migratory birds and killbirds of prey


Trade-Offs

Wind Power

Producing Energy from BiomassProducing Energy from Biomass

Biomass and biofuelsBiomass and biofuels

Biomass plantationsBiomass plantations

Crop residuesCrop residues

Animal manureAnimal manure

Biogas Biogas

Ethanol Ethanol

MethanolMethanol

High octane

Some reduction in CO2 emissions

Lower total airPollution (30-40%)

Can be made from natural gas, agriculturalwastes, sewage sludge, and garbage

Can be used to produceH2 for fuel cells

Large fuel tank needed

Half the driving range

Corrodes metal, rubber, plastic

High CO2 emissions if madefrom coal

Expensive to produce

Hard to start in cold weather


Trade-Offs

Methanol Fuel

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 growingfood on cropland

Higher NO emission

Corrosive

Hard to start incolder weather


Trade-Offs

Ethanol Fuel

Large potential supply in some areas

Moderate costs

No net CO2 increase if harvested and burnedsustainably

Plantation can be located on semiarid land not needed for crops

Plantation can help restoredegraded 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 withcropland Often burned in inefficientand polluting open fires and stoves


Trade-Offs

Solid Biomass

Geothermal EnergyGeothermal Energy

Geothermal heat pumpsGeothermal heat pumps

Geothermal exchangeGeothermal exchange

Dry and wet steamDry and wet steam

Hot waterHot water

Molten rock (magma)Molten rock (magma)

Hot dry-rock zonesHot dry-rock zones

Geothermal Power Plant-Geysers, California

•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 SiteThe 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)


•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/(cm3 oC)*225oC

= 8x1019 J (Total Energy)


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 PlantsGeothermal Power Plants

• Dry Steam

• Flash Steam

• Binary Cycle

Geysers dry steam field, in northern California

Binary Plant Soda Lake, Nevada

East Mesa, California Flash Steam Plant

Hybrid Binary and Flash PlantBig Island of Hawaii

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


Trade-Offs

Geothermal Fuel

Material Energy 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

Energy Density of Some Materials Energy Density of Some Materials

The Hydrogen RevolutionThe Hydrogen Revolution

Extracting hydrogen efficientlyExtracting hydrogen efficiently

Storing hydrogenStoring hydrogen

Fuel cellsFuel cells

Environmentally friendly hydrogenEnvironmentally friendly hydrogen

The Hydrogen RevolutionThe Hydrogen Revolution

Utilization

Electric utility

Transportation

Commercial/Residential

Industrial

Storage

Gas and solids

Transport

Vehicles and pipeline

Photo-conversion

Electrolysis

Reforming

Hydrogen Production

Ele

ctri

city

G

ener

atio

n

Primary Energy Sources

Sunlight

Fossil fuels

Biomass

Wind

Entering the Age of Decentralized MicropowerEntering the Age of Decentralized Micropower

Decentralized power systems Decentralized power systems

Micropower systems Micropower systems

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

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)

Decentralized power systemsDecentralized power systems

BioenergyPowerplants

Wind farm Small solar cellpower plants

Fuel cells

Solar cellrooftop systems

Commercial

MicroturbinesIndustrial

Transmissionand distributionsystem

Residential

Smallwindturbine

Rooftop solarcell arrays

•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

Price Comparison from 1998 Study Leveled Costs: (includes start-up costs)Price Comparison from 1998 Study Leveled Costs: (includes start-up costs)

Solutions: A Sustainable Energy StrategySolutions: A Sustainable Energy Strategy

• 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.

What Can You Do?

Energy Use ad Waste

alternate energy

Documents

dollarsusing solar energy

index of energy

heat r

passive solar house

typical furnacepassive

power car

cell splits h2

heatnatural gas