Power Grid Load Leveling

1
Power Grid Load Leveling

• Cody Hyman

2
Division of Power Generation

• The Base Load Power Plants
• Always active and feeding the grid
• Mostly Coal and Nuclear
• Intermediate and Peaking Power Plants
• Activated when power demand increases
• Includes smaller fossil fuel plants and
  hydroelectricity
• Supplemented by forms of Alternative Energy

Source http//www.opc.com/PoweringGeorgia/Typesof
PowerPlants/index.htm
3
Basic Load Principle

• The greater the demand for power, the more
  current the power plants must provide
• Power companies need to provide a relatively
  constant AC voltage and frequency to customers
• The power transmission and distribution grid of a
  developed nation like the US is an incredibly
  complex and constantly changing circuit

4
The Day and Night Cycle

• Large Fluctuation Between Day and Night Power
  Demand (lowest demand may be around 60 of peak
  demand)
• Grid must quickly compensate for changes in
  demand
• Additionally, demand varies by other factors
  including the local climate and season

5
Demand Throughout the Day
Image taken from California ISO state grid data
for 13 October 2009 Current grid data can be
found at http//www.caiso.com/outlook/outlook.html
6
Effects of Unbalanced Generation and Load

• If demand is too great, outages occur
• Dropouts, brownouts, and blackouts
• Rolling blackouts are created intentionally to
  keep the grid partially up while demand is too
  great for the grid to support
• Most surplus energy, if there is any, is lost

7
How the Load is Leveled

• Organizations managing the grid predict load
  curves
• ex the California ISO
• Number of connected generators is varied
• Spinning reserves and peaking plants supply extra
  power during peak demand
• Stored energy is sometimes fed into the grid

8
Storing Surplus Energy

• Some energy can be stored for use during peak
  hours
• Only a small fraction is stored currently due to
  the expense of storing energy
• Intermittent power sources such as wind and solar
  may suddenly stop generating power, causing a
  large droop in the grid
• Storage methods include
• Batteries (Very efficient, but expensive)
• Pumping water for hydroelectricity
• Gas Compression1
• Flywheels (Steadying Voltage and UPSs)

HowStuffWorks. Grid Energy Storage
lthttp//science.howstuffworks.com/earth/green-tech
nology/sustainable/community/grid-energy-storage.h
tm gt.1-http//www.mercurynews.com/business/ci_132
10674?nclick_check1
9
The Potential Impact of EVs

• Great increase in total grid demand as more
  electric vehicles are put on the road
• Off-Peak Night Charging to fill valleys in the
  demand curve
• The Pacific Northwest National Lab estimate
  approximately 70 of an EV based American road
  transportation system could be charged on current
  generation capacity
• Would decrease the amount of necessary grid
  expansion

PHEV Projections obtained from PNWNL
lthttp//www1.eere.energy.gov/vehiclesandfuels/avta
/pdfs/phev/pratt_phev_workshop.pdfgt
10
A Rough Estimate of EV Energy Requirements

• PNWNL estimates the following energy requirements
  for hybrid electric vehicles with an average
  generator to battery efficiency of around 68-70
  (includes transmission and distribution losses as
  well as charger and battery inefficiencies)
• Compact Cars 0.26kWh/mi
• Mid-Sized Cars 0.30kWh/mi
• Mid-Size SUVs/Vans 0.38kWh/mi
• Full Size SUVs 0.46 kWh/mi
• The U.S. Bureau of Transportation Statistics
  estimates that in the U.S. During 2006, there
  were 1.683x1012mi driven in passenger cars and
  1.089x1012mi driven in other 2-axle 4 wheeled
  vehicles (vans and SUVs)

Per Mile Energy Costlt http//www1.eere.energy.gov
/vehiclesandfuels/avta/pdfs/phev/pratt_phev_worksh
op.pdfgtBTS Mileage Datalt http//www.bts.gov/publ
ications/national_transportation_statistics/html/t
able_01_32.htmlgt
11
A Rough Estimate of EV Energy Requirements

• A rough assumption based on my own calculations
  of the data puts annual passenger car/SUV demand
  at 900-1000TWh (1PWh)
• Peak Generation Output of US Generators is approx
  1.1TW, assuming maybe 900GW are in operation at
  all times, around 7900TWh could be generated
  annually.
• The EIA also estimates the addition of around
  20GW of generation capacity annually
• Current demand averages around 640-780GW
• In reality only some regions can currently cope
  with a heavy EV demand (Midwest has the capacity
  to currently support a full conversion to EVs,
  the West Coast does not)

Power Generation Data from U.S. Energy
Information Administration (EIA)
12
Vehicle-To-Grid

• Potential to sell electricity from an EV back to
  the grid during peak demand hours
• A single EV can likely supply around 10kW
• Also could be used as a source of emergency power
  in the event of a blackout. A nation of electric
  cars could potentially power the grid for up to 5
  hours

Image Source University of Delawarelthttp//www.ud
el.edu/V2G/page2/page9/files/pasted-graphic-1.jpggt
13
A Smarter Grid

• A growing number of regions across the world are
  implementing modern technology to power
  distribution and metering
• Smart meters can be used to provide time-specific
  electricity rates and cause non-essential power
  usage to be rescheduled to non-peak hours
• Pricing changes or appliance-specific lockouts
  will influence
• Example Increased cost of running large
  appliances during peak load hours
• Smart Meters will likely be essential to the
  implementation of a national EV fleet and V2G
  technology

14
Smart Meters
Source B.B.S. Electronics lthttp//www.bbsgroup.com
.sg/images/AMRsolution.jpggt
15
Implementation of Smart Metering

• Some regions and nations are actively installing
  smart meters
• Ontario, Canada will have converted entirely over
  to smart meters by 2010
• California and Texas also have large scale
  implementation of smart meters
• Also used extensively in the UK and Australia

Image Source https//www.horizonutilities.net/HHS
C/assets/images/SmartMeter.jpg
16
Sources

• Types of Power Plants, Oglethorpe Power
  lthttp//www.opc.com/PoweringGeorgia/TypesofPowerPl
  ants/index.htmgt
• Current Demand Outlook, California ISO
  lthttp//www.caiso.com/outlook/outlook.htmlgt
• Blackouts, Virginia Department of Emergency
  Management lthttp//www.vaemergency.com/threats/bla
  ckout/gt
• Pratt, et. al., Potential Impacts of High
  Penetration of Plug-in Hybrid Vehciles on the
  U.S. Power Grid, Pacific Northwest National
  Laboratory, June 2007, lthttp//www1.eere.energy.go
  v/vehiclesandfuels/avta/pdfs/phev/pratt_phev_works
  hop.pdfgt
• U.S. Bureau of Transportation Statistics 2006
  Vehicle Milage Data lthttp//www.bts.gov/publicatio
  ns/national_transportation_statistics/html/table_0
  1_32.htmlgt
• Vehicle-To-Grid Technology, University of
  Delaware lthttp//www.udel.edu/V2G/gt
• Vehicle-To-Grid Technology Diagram, University of
  Delaware ltSource University of
  Delawarelthttp//www.udel.edu/V2G/page2/page9/files
  /pasted-graphic-1.jpggt
• Energy Information Administration Data
  lthttp//www.eia.doe.gov/gt