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Special Topic: Alternative Energy
Aaron Glieberman
August 10, 2010
In the news today
Portugal Gives Itself a Clean-Energy Makeover
NY Times August 10, 2010Front page story
Overview
- Energy overview, key concepts- State of energy usage- Types of alternative energy- Thought problems- Guest Speaker: Dr. Chris Bull, Ph.D.
- Guest Speaker: Gordon Barr
Energy Review
We’ve discussed numerous types of energy so far:
MechanicalChemicalElectromagneticThermal
Remember: conservation of energy
Key terminology and relationships
Force – phenomenon acting upon an object or particle that causes it to undergo acceleration, measured in newtons (N)
Work – energy transfer from one system to another, affecting the second system in a particular fashion (and often involving movement), measured in joules (J)
Power – rate of work done, measured in watts (W)
Key terminology and relationships
Force = m*a
Mechanical Work = F*d
Mechanical Power = Work/t
Electrical work = V*Q
Electrical Power = V*I = I2*R (remember: V= IR)
(also, electromagnetic)
Key terminology and relationships
In energy industry talk, energy usage is typically described in British thermal units (Btu) or kilowatt-hours (kWh),
megawatt-hours (MWh), etc.
1 British thermal unit = 1055 joules
1 kilowatt-hour = 3.6 megajoules = 3412 Btu
Energy “consumption”Petroleum used for transportation accounts for 27.9% of all supply in US
Coal used for energy accounts for 20.7% of all supply in US
By comparison, renewables for transportation and energy account for only 0.6% and 3.5%, respectively
We use more nuclear energy than renewable
Petroleum usage
Coal power plant
Coal power plant
Internal combustion engine
The dangers of modern energy sources
Pollution
- Both contribute substantially to greenhouse gasses, coal especially being the largest human-made contributor
- Ash, mercury, arsenic, selenium from burning coal can cause health problems
Limited supplies
- Spills – petroleum is extremely toxic
- Environmental toll from extraction, transportation, and processing of coal and petroleum
- Future mining efforts will eventually become more difficult
- If supply dwindles, this will drastically affect the economy, which depends on electricity and transportation
- Political considerations – self-dependency
Hubbert’s peak
Projections of world oil production
Deepwater Horizon oil spill
Largest marine oil spill in history of petroleum usage
April 20, 2010
Deepwater Horizon oil spill
Estimated total volume of 4-5 million barrels spilled
1 barrel = 42 US gallons = 159 L
How much oil is this?
April 20, 2010
168 million gallons of oil spilled
Deepwater Horizon oil spill
Estimated total volume of 4-5 million barrels spilled
April 20, 2010
BUT . . .
Significant, but not even that much compared to daily use
The alternatives
HydroelectricSolarWind
BiomassGeothermal
Hydrogen fuelElectric cars(Nuclear power)
The alternatives
Consider:
EfficiencyCostResource requirementsImpact
Hydroelectric
Generation of electrical energy using mechanical energy of moving water
Largest source of renewable energy in the world
HydroelectricTypical operation scheme
Dam is used to create a water reservoir that stores energy
Functions according to potential energy
Water flowing from high to low pressure turns a turbine, which is connected to a generator
Hydroelectric
Most simply, the power produced by hydroelectric means can be calculated as:
P = ρ*h*Q*g*e
h = height difference between upstream and downstream water
Q = flow rate of water
e = efficiency of system (turbine and generator)
ρ = density of water
g = acceleration due to gravity
Hydroelectric
Hydroelectric schemes can be large or small
Excess power generation can be used to pump water to higher ground, thus storing it for later
Tidal power utilizes a similar concept but may not require a dam, instead harnessing tidal flow to turn turbines
Additional concern over salinity of water
HydroelectricStrengths
Limitations
- Can have a significant environmental impact- Can only be in areas close to a river
- No carbon dioxide emissions- Can be used to control water flow in a river for other purposes (tourism, agriculture, flood reduction)
- Often requires significant land investment and long construction time
- Possibility for storage- Long-term
- Possibility for indirectly creating methane emissions- Potential for failure
Three Gorges DamYangtze river in China
- Largest electricity-producing plant in the world- Eventual production potential of 22,500 MW- Replacement for coal, reducing estimated coal consumption by as much as 31 million metric tons per year- Regulates water flow downstream, either providing water during the dry season or preventing flooding
Three Gorges Dam
However,
- Displaced 1.3 million people during construction
- Has directly affected habitat for much wildlife, including endangered species
- Some estimate that erosion and sedimentation will interfere with dam function
- Flooding in July 2010 has demonstrated that dam is not fool-proof
- Substantial environmental impact, such as deforestation
Solar Energy
Utilization of energy from the sun for lighting, thermal purposes or to produce electrical energy
Solar energy is an extremely abundant resource
Solar EnergyPhotovoltaic technology
Sunlight hits photovoltaic cells, generating an electric current
Solar EnergyPhotovoltaic technology
Solar EnergyConcentrating solar power (CSP)
Solar EnergyThe power produced by photovoltaic cells can be calculated as follows:
A single square inch of photovoltaic cell produces about 0.45 V and 0.224 A in full sunlight
This means that photovoltaic cells produce roughly:
P = 0.45 V * 0.224 A = 0.10 watts per square inch = 156 watts/m2
Cells can be arranged in series or in parallel to produce different voltages and currents
Solar EnergyOther applications
Water heating
Solar EnergyOther applications
Water treatment Cooking
Solar EnergyStrengths
Limitations- No energy source at night or in sunless weather conditions- Specialized technology that is difficult to manufacture
- Quiet- Electricity and heating capabilities- Abundant supply- No pollution during use- Low operating/maintenance requirements- Resource is most available during peak energy usage- Small-scale technology
- High installation costs that require solid investment- Generate DC current that must be converted to AC, reducing efficiency
Solar EnergySolar Impulse, a company in Switzerland, accomplishes first ever 24-hour flight by a solar-powered plane
Wind Energy
Generation of electrical energy from the mechanical energy in wind
Wind EnergyWind electric power generation
Wind rotates the blades, which then spin the internal rotor, shafts and generator
Gears, pulleys, or chains are necessary to convert the rotational velocities and to alter the axis of rotation
Note that wind speed and direction are not constant, so one calculates the capacity factor (the ratio between the actual productivity and the theoretical maximum productivity)
Capacity factors are normally 20-40%
Wind EnergyTwo designs for wind power utilize drag and lift
Lift-oriented wind turbine
Drag-oriented wind turbine
Wind Energy
The power produced by a wind turbine can be calculated as follows:
P = 0.5*ρ*A*v3*e
A = area swept by blades
e = efficiency of system (turbine and generator)
ρ = density of water
v = velocity of air
Wind EnergyStrengths
Limitations- Unattractive to some- Large capital cost
- World potential exceeds current world energy usage- No pollution during operation
- Possible harm to birds - Large land requirement (should be 10 times blade span away from one another)- Preferably located in windy regions, which might be far from urban centers
Combining wind and solarBluenergy Solar-Wind-Turbine
Geothermal Energy
Utilizing the energy from geothermal vents for heating or to produce electricity
Geothermal Energy
Heated steam from beneath the ground transfers its thermal energy to a fluid with low boiling point that drives a turbine at high pressure
Cooled substances from the earth return below
Energy efficiency of this technology is low, on the order of 10-20%
Surrounding rocks keep steam insulated as it is piped from the ground
Binary geothermal plant
Geothermal Energy
For generating electricity, deeper wells are typically drilled to harness higher heat
Direct applications – Low temperature (<300°C) and shallower implementations are often applied for small-scale use, especially geothermal heating
Geothermal EnergyStrengths
Limitations- Limited by location (must be near tectonic plate boundaries)- Low efficiency
- Relatively cheap- Reliable
- Some designs release fluids from the earth, which may include harmful emissions
- Constant supply of resource (high capacity factor)
Biomass Energy
Utilizing the chemical energy stored in biological substances for heating or to produce electricity
Biomass Energy
Covers a wide range of possible energy sources and corresponding technologies to harness the energy
Traditional cases have relied upon combustion to extract the energy
Newer focus in chemical and biochemical means of fuel conversion and energy extraction
Biomass Energy
Direct firing – biomass is burned at the bottom of a boiler, producing steam to turn a turbine
Co-firing – biomass is mixed with in traditional fossil fuel (usually coal) and directly burned to generate steam
Pyrolysis – biomass undergoes high temperature in an oxygen-depleted environment, yielding pyrolysis oil that is effective for burning
Gassification – application of thermal energy to biomass produces combustible gasses
Biomass Energy
Another nod towards synthetic biology
Engineer microbes to catalyze certain biochemical reactions, producing alcohols or other biofuels
Biomass EnergyStrengths
Limitations- Mostly results in combustion process, which releases greenhouse gasses
- Low efficiency
- Almost universally abundant- Reliable- Possibility for repurposing traditional “waste”- Can be utilized with modified fossil fuel equipment/infrastructure
- Fewer toxic byproducts compared to fossil fuels
Comparative costs
Comparative costsRETI Stakeholder Steering CommitteeRenewable Energy Transmission Initiative Phase 1A
16 May 2008
Fuel cell technology
Electrochemical process of producing electricity from a chosen fuel source
Fuel cell technology
http://auto.howstuffworks.com/fuel-efficiency/alternative-fuels/fuel-cell.htm
Also,
Hydrogen flows along one side of a maintained electric field, oxygen on the other
One example: Hydrogen fuel cell
Some hydrogen atoms selectively travel across the field to react with oxygen, producing a current as they move
Water is released as a byproduct
Electric cars
Electric cars
Generally speaking, cars that depend on batteries to store energy through chemical means and convert that energy to electrical while in use
Depends upon battery technology and energy efficicency
Energy conservation
Power requirements for common appliances
http://www.ge.com/visualization/appliances_energyuse/index.html
Power requirements for common appliances
Appliances plugged into a socket still use electricity even while turned off . . .
Power requirements for common appliances
Appliances plugged into a socket still use electricity even while turned off . . .
Power requirements for common appliances
Appliances plugged into a socket still use electricity even while turned off . . .
Light bulb comparisonEnergy Savings Calculator for Replacing Light Bulbs
Incandescent Light BulbsCFL(Compact Fluorescent Light Bulbs)
LED(Light-Emitting Diode Light Bulbs)
Life Span (in hours) 1,500 10,000 60,000 Watts 60 14 6 Cost $1.345 $2.98 $54.95 KWh of electricty used over 60k hours 3,600 840 360 Electricity Cost (@ $0.23 per KWh) $821.72 $191.73 $82.17 Bulbs needed for 60k hours of usage 40 6 1 Equivalent 60k hour bulb expense $53.80 $17.88 $54.95 Total 60,000 Hour Lighting Spend $875.52 $209.61 $137.12
Calculate Your Energy Savings
# of household light bulbs 30 30 30 Your estimated daily usage (hours) 5 5 5 Days in month 30 30 30
Household savings over 60,000 hours (energy + replacement) Household cost $26,265.54 $6,288.43 $4,113.65 Savings by switching from Incandescent $0.00 $19,977.11 $22,151.89
Monthly household energy savings KWh used per month 270 63 27 Electricity Cost (@ $0.23 per KWh) $61.63 $14.38 $6.16 Savings by switching from Incandescent $0.00 $47.25 $55.47
Yearly household energy savings KWh used per year 3,285 767 329 Electricity Cost (@ $0.23 per KWh) $749.82 $174.96 $74.98 Savings by switching from Incandescent $0.00 $574.86 $674.84 productdose.com comments:blue font = input your personal data here KWh = Kilowatt-hours Choose KWh rate type: * 2 black font = pre-calculated cells * change the data on the next tab. 1 = Average rateunderlined text = where to buy / product info 2 = Highest rateAll data from manufacturer as of 5/2/06 3 = Your own rate