Alternate Energy Energy Efficiency and Renewable Energy.
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Transcript of Alternate Energy Energy 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
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%
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
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
Single Solar Cell
Boron-enrichedsilicon
Junction
Sunlight
Cell
Phosphorus-enriched silicon
DC electricity
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
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
Advantages Disadvantages
Trade-Offs
Large-Scale Hydropower
•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)
Basics of Wind EnergyBasics 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
Basics of Wind EnergyBasics of Wind Energy
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 )
Sample Wind ProblemSample 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 ProblemSample 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 ProblemSample 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
Sample Wind ProblemSample Wind Problem
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
Advantages Disadvantages
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
Advantages Disadvantages
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
Advantages Disadvantages
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
Advantages Disadvantages
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
•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)
The Geysers Geothermal SiteThe 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/(cm3 oC)*225oC
= 8x1019 J (Total Energy)
The Geysers Geothermal SiteThe 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.
The Geysers Geothermal SiteThe Geysers Geothermal Site
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
Advantages Disadvantages
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)
• 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