Midterm Exam Review SYST 6820 Assessing Sustainable Energy Technologies

Midterm Exam Review

SYST 6820

Assessing Sustainable Energy Technologies

Exam Covers Renewable Energy Renewable

Hydro Power Wind Energy Oceanic Energy Solar Power Geothermal Biomass

Sustainable Hydrogen & Fuel Cells Nuclear Fossil Fuel Innovation Integration

Distributed Generation Presentations

Exam Setting

Tuesday, March 14, 11:00 AM – 12:15 PM 75 minutes max

Closed book, closed notes, calculator OK One 8½ × 11 inch reference sheet allowed

Both sides; apply ink any way you want Composition of exam

~ 50% qualitative Short essay, short answer, multiple choice, T/F/Explain

~50% quantitative

How to Study

1. Homework

2. Lectures

3. Textbook Lectures

Homework

Textbook

Sweet Spot

Review for Exam

Introduction Renewable

Hydro Power Wind Energy Oceanic Energy Solar Power Geothermal Biomass

Introduction toSustainable Energy

Sources of New Energy

Boyle, Renewable Energy, Oxford University Press (2004)

Global Energy Sources 2002


Primary energy consumed per capita

BP website (BP.com)

Oil & Gas Production Forecasts


Environmental Concerns

Wikipedia.org, Climate Change, Global Warming articles

Political Concerns

Business Opportunities

Hydro Power

Hydrologic Cycle

http://www1.eere.energy.gov/windandhydro/hydro_how.html

Hydropower to Electric Power

PotentialEnergy

KineticEnergy

ElectricalEnergy

MechanicalEnergy

Electricity

Renewable Energy Sources

Wisconsin Valley Improvement Company, http://www.wvic.com/hydro-facts.htm

Conventional Impoundment Dam

http://www1.eere.energy.gov/windandhydro/hydro_plant_types.html

Diversion (Run-of-River) Hydropower

Pumped Storage Schematic

Efficiency of Hydropower Plants Hydropower is very efficient

Efficiency = (electrical power delivered to the “busbar”) ÷ (potential energy of head water)

Typical losses are due to Frictional drag and turbulence of flow Friction and magnetic losses in turbine &

generator Overall efficiency ranges from 75-95%

Boyle, Renewable Energy, 2nd edition, Oxford University Press, 2003

Hydropower Calculations

P = power in kilowatts (kW) g = gravitational acceleration (9.81 m/s2) = turbo-generator efficiency (0<n<1) Q = quantity of water flowing (m3/sec) H = effective head (m)

HQP

HQgP

10

Boyle, Renewable Energy, 2nd edition, Oxford University Press, 2003

Impacts of Hydroelectric Dams

Ecological Impacts

Loss of forests, wildlife habitat, species Degradation of upstream catchment areas due to

inundation of reservoir area Rotting vegetation also emits greenhouse gases Loss of aquatic biodiversity, fisheries, other downstream

services Cumulative impacts on water quality, natural flooding Disrupt transfer of energy, sediment, nutrients Sedimentation reduces reservoir life, erodes turbines

Creation of new wetland habitat Fishing and recreational opportunities provided by new

reservoirs

Environmental and Social Issues Land use – inundation and displacement of people Impacts on natural hydrology

Increase evaporative losses Altering river flows and natural flooding cycles Sedimentation/silting

Impacts on biodiversity Aquatic ecology, fish, plants, mammals

Water chemistry changes Mercury, nitrates, oxygen Bacterial and viral infections

Tropics Seismic Risks Structural dam failure risks

Hydropower – Pros and Cons

Positive NegativeEmissions-free, with virtually no CO2, NOX, SOX, hydrocarbons, or particulates

Frequently involves impoundment of large amounts of water with loss of habitat due to land inundation

Renewable resource with high conversion efficiency to electricity (80+%)

Variable output – dependent on rainfall and snowfall

Dispatchable with storage capacity Impacts on river flows and aquatic ecology, including fish migration and oxygen depletion

Usable for base load, peaking and pumped storage applications

Social impacts of displacing indigenous people

Scalable from 10 KW to 20,000 MW Health impacts in developing countries

Low operating and maintenance costs High initial capital costs

Long lifetimes Long lead time in construction of large projects

Wind Energy

Becoming a Significant Power Source

Wind could generate 6% of nation’s electricity by 2020.

Wind currently produces less than 1% of the nation’s power. Source: Energy Information Agency

Advantages of Wind Power

Environmental Resource Diversity &

Conservation Cost Stability Economic Development

Siting a Wind Farm Winds

Minimum class 4 desired for utility-scale wind farm (>7 m/s at hub height) Transmission

Distance, voltage excess capacity Permit approval

Land-use compatibility Public acceptance Visual, noise, and bird impacts are biggest concern

Land area Economies of scale in construction Number of landowners

Power in the Wind (W/m2)

Density = P/(RxT) P - pressure (Pa) R - specific gas constant (287 J/kgK) T - air temperature (K)

= 1/2 x air density x swept rotor area x (wind speed)3

A V3

Area = r2 Instantaneous Speed(not mean speed)

kg/m3 m2 m/s

2006 5 MW 600’

2003 1.8 MW 350’

2000 850 kW 265’

Recent Wind Turbine Capacity Enhancements

0

500

1000

1500

2000

2500

Vestas V80 2 Vestas V80 2 MWMW Wind Turbine Power Curve Wind Turbine Power Curve

KW

MPH

5040302010

Wind Energy and the Grid

Dispatchability When the wind blows (night? Day?) Intermittence Grid connectivity- Lack of Transmission Predicting the Wind-We’re getting better

Base Load – Coal

Gas/Hydro

Gas

Electricity Demand and Supply Must Be Instantaneously Balanced

3500

4000

4500

3000

Wind Energy Storage Pumped hydroelectric

Georgetown facility – Completed 1967 Two reservoirs separated by 1000 vertical feet Pump water uphill at night or when wind energy production exceeds demand Flow water downhill through hydroelectric turbines during the day or when wind energy

production is less than demand About 70 - 80% round trip efficiency Raises cost of wind energy by 25% Difficult to find, obtain government approval and build new facilities

Compressed Air Energy Storage Using wind power to compress air in underground storage caverns

Salt domes, empty natural gas reservoirs Costly, inefficient

Hydrogen storage Use wind power to electrolyze water into hydrogen Store hydrogen for use later in fuel cells 50% losses in energy from wind to hydrogen and hydrogen to electricity 25% round trip efficiency Raises cost of wind energy by 4X

Wind Farm Economics

Example 200 MW wind farm

Fixed costs - $1.23M/MW Class 4 wind site

33% capacity factor 10 miles to grid 6%/15 year financing

100% financed 20 year project life

Determine Cost of Energy - COE

Wind Farm Economics

Total Capital Costs $246M + (10 x $350K) = $249.5M

Total Annual Energy Production 200 MW x 1000 x 365 x 24 x 0.33 = 578,160,000 kWh

Total Energy Production 578,160,000 x 20 = 11,563,200,000 kWh

Capital Costs/kWh 3.3¢/kWh

Operating Costs/kWh 1.6¢/kWh

Cost of Energy – New Facilities Wind – 4.9¢/kWh Coal – 3.7¢/kWh Natural gas – 7.0¢/kWh

@ $12/MMBtu

Wind Farm Economics

Federal government subsidizes wind farm development in three ways 1.9 ¢/kWh production tax credit

33.5% subsidy 5 year depreciation schedule

29.8 % subsidy Depreciation bonus

2.6% subsidy

Oceanic Energy

Tidal Forces


Natural Tidal Bottlenecks


1. Tidal Turbine Farms

Advantages of Tidal Turbines

Low Visual Impact Mainly, if not totally submerged.

Low Noise Pollution Sound levels transmitted are very low

High Predictability Tides predicted years in advance, unlike wind

High Power Density Much smaller turbines than wind turbines for the

same power

http://ee4.swan.ac.uk/egormeja/index.htm

Disadvantages of Tidal Turbines High maintenance costs High power distribution costs Somewhat limited upside capacity Intermittent power generation

2. Tidal Barrage Schemes

Tidal Barrage Energy Calculations

ARE

gRARmgRE21397

2/)(2/

R = range (height) of tide (in m)A = area of tidal pool (in km2)m = mass of waterg = 9.81 m/s2 = gravitational constant = 1025 kg/m3 = density of seawater 0.33 = capacity factor (20-35%)

kWh per tidal cycle

Assuming 706 tidal cycles per year (12 hrs 24 min per cycle)

AREyr2610997.0

Tester et al., Sustainable Energy, MIT Press, 2005

Advantages of Tidal Barrages

High predictability Tides predicted years in advance, unlike wind

Similar to low-head dams Known technology

Protection against floods Benefits for transportation (bridge) Some environmental benefits

http://ee4.swan.ac.uk/egormeja/index.htm

Disadvantages of Tidal Turbines High capital costs Few attractive tidal power sites worldwide Intermittent power generation Silt accumulation behind barrage

Accumulation of pollutants in mud Changes to estuary ecosystem

3. Wave Energy

Wave Structure


Wave Power Calculations

2

2es TH

P

Hs2 = Significant wave height – 4x rms water elevation (m)

Te = avg time between upward movements across mean (s) P = Power in kW per meter of wave crest length

Example: Hs2 = 3m and Te = 10s

m

kWTHP es 45

2

103

2

22

Global Wave Energy Averages

http://www.wavedragon.net/technology/wave-energy.htm

Average wave energy (est.) in kW/m (kW per meter of wave length)

Tapered Channel (Tapchan)

http://www.eia.doe.gov/kids/energyfacts/sources/renewable/ocean.html

Oscillating Water Column

http://www.oceansatlas.com/unatlas/uses/EnergyResources/Background/Wave/W2.html

Ocean Wave Conversion System

http://www.sara.com/energy/WEC.html

Wave Dragon

http://www.wavedragon.net/technology/wave-energy.htm

Wave DragonCopenhagen, Denmarkhttp://www.WaveDragon.net

Click Picture for Video

Wave Energy Environmental Impact Little chemical pollution Little visual impact Some hazard to shipping No problem for migrating fish, marine life Extract small fraction of overall wave energy

Little impact on coastlines

Release little CO2, SO2, and NOx

11g, 0.03g, and 0.05g / kWh respectively


Wave Power Advantages

Onshore wave energy systems can be incorporated into harbor walls and coastal protection Reduce/share system costs Providing dual use

Create calm sea space behind wave energy systems Development of mariculture Other commercial and recreational uses;

Long-term operational life time of plant Non-polluting and inexhaustible supply of energy


Wave Power Disadvantages

High capital costs for initial construction High maintenance costs Wave energy is an intermittent resource Requires favorable wave climate. Investment of power transmission cables to shore Degradation of scenic ocean front views Interference with other uses of coastal and offshore

areas navigation, fishing, and recreation if not properly sited

Reduced wave heights may affect beach processes in the littoral zone


Solar Power

http://www.c-a-b.org.uk/projects/tech1.jpg

1. Solar Photovoltaic (PV) Energy

Light & the Photovoltaic Effect

Certain semiconductor materials absorb certain wavelengths The shorter the wavelength the greater the energy Ultraviolet light has more energy than infrared light

Crystalline silicon Utilizes all the visible spectrum plus some infrared radiation

Heat vs. electrical energy Light frequencies that is too high or too low for the

semiconductor to absorb turn into heat energy instead of electrical energy

Cross Section of PV Cell

http://en.wikipedia.org/wiki/Solar_cells

Silicon Ingots & Wafers

http://www.sumcosi.com/english/products/products2.html

Creating PV Cells

Solar PV Systems Cells are the building block of PV systems

Typically generate 1.5 - 3 watts of power Modules or panels are made up of multiple cells Arrays are made up of multiple modules

A typical array costs about $5 – $6/watt Still need lots of other components to make this work Typical systems cost about $8/watt

Solar Cell Efficiencies

Typical module efficiencies ~12% Screen printed multi-crystalline solar cells

Efficiency range is 6-30% 6% for amorphous silicon-based PV cells 20% for best commercial cells 30% for multi-junction research cells

Typical power of 120W / m2 Mar/Sep equinox in full sun at equator


Solar Panel Efficiency

~1 kW/m2 reaches the ground (sunny day) ~20% efficiency 200W/m2 electricity Daylight & weather in northern latitudes

100 W/m2 in winter; 250 W/m2 in summer Or 20 to 50 W/m2 from solar cells

Value of electricity generated at $0.08/kWh $0.10 / m2 / day OR $83,000 km2 / day

http://en.wikipedia.org/wiki/Solar_panel

Cost Analysis

US retail module price = ~$5.00 / W (2005) Installations costs = ~$3.50 / W (2005) Cost for a 4 kW system = ~$17,000 (2006)

Without subsidies Typical payback period is ~24 years

Honda 4 kW system = ~$12,500 (2007) With subsidies

Payback is ~12 years


Solar PV Energy Payback

Expected lifetime of 40 years Payback of 1-30 years

Typically < 5 years Solar cells 6-30× energy required to make

them


2. Solar Thermal Energy

Solar Thermal Collectors

Focus the sun to create to create heat Boil water Heat liquid metals

Use heated fluid to turn a turbine Generate electricity

Solar Thermal Dish Schematic

Parabolic Trough Cross-Section

http://www.irishsolar.com/howdoes/how_does_1.htm

Geothermal Energy

Earth Dynamics

http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm

Earth Temperature Gradient

http://www.geothermal.ch/eng/vision.html

Geothermal Site Schematic

Boyle, Renewable Energy, 2nd edition, 2004

Global Geothermal Sites

http://www.deutsches-museum.de/ausstell/dauer/umwelt/img/geothe.jpg

Methods of Heat Extraction

http://www.geothermal.ch/eng/vision.html

Dry Steam Schematic


Single Flash Steam Schematic


Hot Dry Rock Technology

Fenton Hill plant http://www.ees4.lanl.gov/hdr/

Environmental Impacts

Land Vegetation loss Soil erosion Landslides

Air Slight air heating Local fogging

Ground Reservoir cooling Seismicity (tremors)

Water Watershed impact Damming streams Hydrothermal eruptions Lower water table Subsidence

Noise

Benign overall

http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm

Renewable?

Heat depleted as ground cools Not steady-state

Earth’s core does not replenish heat to crust quickly enough

Example: Iceland's geothermal energy could provide 1700 MW for

over 100 years, compared to the current production of 140 MW

http://en.wikipedia.org/wiki/Geothermal

Cost Factors

Temperature and depth of resource Type of resource (steam, liquid, mix) Available volume of resource Chemistry of resource Permeability of rock formations Size and technology of plant Infrastructure (roads, transmission lines)

http://www.worldbank.org/html/fpd/energy/geothermal/cost_factor.htm

BIOENERGY

Bioenergy Cycle

http://www.repp.org/bioenergy/bioenergy-cycle-med2.jpg

US Energy Cropland

http://www.cbsnews.com/htdocs/energy/renewable/map_bioenergy_image.html

Biomass Resources

Energy Crops Woody crops Agricultural crops

Waste Products Wood residues Temperate crop wastes Tropical crop wastes Animal wastes Municipal Solid Waste (MSW) Commercial and industrial wastes

http://www.eere.energy.gov/RE/bio_resources.html

Bioenergy Technologies


Biorefinery

http://www.nrel.gov/biomass/biorefinery.html

Biomass Direct Combustion


MSW Power Plant


Landfill Gasses


Sugar Platform

1. Convert biomass to sugar or other fermentation feedstock

2. Ferment biomass intermediates using biocatalysts

• Microorganisms including yeast and bacteria;

3. Process fermentation product • Yield fuel-grade ethanol and other fuels,

chemicals, heat and/or electricity

http://www.nrel.gov/biomass/proj_biochemical_conversion.html

Gasification

Biomass heated with no oxygen Gasifies to mixture of CO and H2

Called “Syngas” for synthetic gas Mixes easily with oxygen Burned in turbines to generate electricity

Like natural gas Can easily be converted to other fuels,

chemicals, and valuable materials

Pyrolysis

Heat bio-material under pressure 500-1300 ºC (900-2400 ºF) 50-150 atmospheres Carefully controlled air supply

Up to 75% of biomass converted to liquid Tested for use in engines, turbines, boilers Currently experimental

http://www1.eere.energy.gov/biomass/pyrolysis.html

Anaerobic Digestion

Decompose biomass with microorganisms Closed tanks known as anaerobic digesters Produces methane (natural gas) and CO2

Methane-rich biogas can be used as fuel or as a base chemical for biobased products.

Used in animal feedlots, and elsewhere

http://www1.eere.energy.gov/biomass/other_platforms.html

BioFuels

Ethanol Created by fermentation of starches/sugars US capacity of 1.8 billion gals/yr (2005) Active research on cellulosic fermentation

Biodiesel Organic oils combined with alcohols Creates ethyl or methyl esters

SynGas Biofuels Syngas (H2 & CO) converted to methanol, or

liquid fuel similar to diesel

http://www.eere.energy.gov/RE/bio_fuels.html

Environmental Issues Air Quality

Reduce NOx and SO2 emissions Global Climate Change

Low/no net increase in CO2

Soil Conservation Soil erosion control, nutrient retention, carbon

sequestration, and stabilization of riverbanks. Water Conservation

Better retention of water in watersheds Biodiversity and Habitat

Positive and negative changes

http://www.eere.energy.gov/RE/bio_integrated.html

Crop Erosion Rates

Michael Totten, Conservation International, January 27, 2006

SRWC = Short Rotation Woody Crops

Biocide Requirements

Michael Totten, Conservation International, January 27, 2006

Short RotationWoody Crops

Multiple benefits would accrue:

www.bioproducts-bioenergy.gov/pdfs/NRDC-Growing-Energy-Final.3.pdf.

Benefits of Bioenergy

Rural American farmers producing these fuel crops would see $5 billion of increased profits per year.

Consumers would see future pump savings of $20 billion per year on fuel costs.

Society would see CO2 emissions reduced by 6.2 billion tons per year, equal to 80% of U.S. transportation-related CO2 emissions in 2002.

Ethanol Production

Ethanol Production

Corn kernels are ground in a hammermill to expose the starch

The ground grain is mixed with water, cooked briefly and enzymes are added to convert the starch to sugar using a chemical reaction called hydrolysis.

Yeast is added to ferment the sugars to ethanol.

The ethanol is separated from the mixture by distillation and the water is removed from the mixture using dehydration

Ethanol Production

Energy content about 2/3 of gasoline So E10 (10% ethanol, 90% gasoline) will cause

your gas mileage to decrease 3-4% Takes energy to create ethanol from starchy

sugars Positive net energy balance Energy output/input = 1.67

MTBE

MTBE (methyl tertiary-butyl ether) A chemical compound that is manufactured by the chemical

reaction of methanol and isobutylene Used almost exclusively a fuel additive in gasoline It is one of a group of chemicals commonly known as

"oxygenates" because they raise the oxygen content of gasoline.

At room temperature, MTBE is a volatile, flammable and colorless liquid that dissolves rather easily in water.

Source: EPA (http://www.epa.gov/mtbe/gas.htm)

Cellulosic Ethanol

Ethanol produced from agricultural residues, woody biomass, fibers, municipal solid waste, switchgrass

Process converts lignocellulosic feedstock (LCF) into component sugars, which are then fermented to ethanol

Source: American Coalition for Ethanol (http://www.ethanol.org/documents/ACERFSSummary.pdf)

Summary

For Every Renewable Energy Tech Why is this technology interesting? How does the technology work? What back-of-envelope calculations apply? What are its environmental impacts? What are its economic implications? What are its advantages? What are its disadvantages? What policy issues are involved?

Good Luck!

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Midterm Exam Review SYST 6820 Assessing Sustainable Energy Technologies