3. INTRODUCTION
• Energy storage is accomplished by devices or
physical media that store some form of energy to
perform some useful operation at a later time. A
device that stores energy is sometimes called an
accumulator
• Storing energy allows humans to balance the supply
and demand of energy. Energy storage systems in
commercial use today can be broadly categorized as
mechanical, electrical, chemical, biological and
thermal.
4. Three Types of Storage
• Pumped hydroelectric
storage (PHS)
• Compressed air energy
storage (CAES)
• Flywheels
5. Pumped Hydroelectric
Storage (PHS)
• Used for load balancing of
energy
• Water is pumped up in
elevation during time of low
demand
• Water flows back down
during times of high demand
• Turbines recapture the
energy.
6. Pumped Hydroelectric
Storage (PHS)
• 70-85% of electrical energy
is recovered
• Energy loss due to
evaporation and
Pump/generator inefficiency
• Currently the most cost
effective way to store large
amounts of electricity
• Low energy density calls for
large bodies of water
• Never used in portable
technology
• 1000 kg at 100 ft = .272 kWh
7. Pumps: On the Grid
• The Us has 19.5 gigawatts
capacity
• 2.5% of baseload
• Technology is in use world
wide
• Hundreds of plants around
the world
• Man made reservoirs as well
as natural reservoirs
8. Future Of PHS
• This energy storage can
be used to level the grid
for renewable energy
• Wind power and solar
power are not
constantly on
• Using salt mines to
increase energy density
9. Compressed air
energy storage (CAES)
• Large tank is buried
underground
• During times of low
demand electricity
compresses air
• During times of peak
demand compressed air
is heated and released
http://www.sandia.gov/media/NewsRel/NR2001/norton.htm
10. Types Of CAES
• Adiabatic storage
• Heat from compression is
captured and stored in a
solid or liquid
• Hot Oil 3000C
• Molten Salt 6000C
• Heat is reincorporated
during release
• Close to 100% efficiency
• No utility scale plants
• Diabatic storage
• Heat is lost through
cooling
• Natural gas is burned to
reheat compressed air
• Very inefficient 38-68%
• Uses 1/2 gas of an all
gas plant
11. More about CAES
• Can use sandstone
layer to hold
compressed air
• USA has good ground
for this type of storage
• Can be used to level
load from wind and
solar
• 200-300 MW Plants
12. Compressed air in Cars
• Zero pollution Motors
• Stores air at around 300atm
• Under 35 mph it is zero
emissions
• Over 35 mph uses
combustion engine to
compress air
• Runs on many different types
of fuel
• 1 air tank + 8 gal gas= 848 miles
13. Fueling/Refueling
• Flex engine runs off of
gas, diesel, alcohol,
possibly even vegetable
oil
• Refueling air tank at
refuel station about 3
minutes
• Home refuel unit takes 4
hours, electrical cost $2
• 3 cents per mile
14. Future of Air Vehicles
• Flowair- release in 2010
• First needs to pass US safety
ratings
• 6 seats
• 106 mpg
• 800-1000 mile range
• Top speed 96 mph
• $17500
15. Flywheels
• Captures energy in a rotating
Mass
• Flywheel is charged using
electric motor
• Electric generator extracts
energy
http://en.wikipedia.org/wiki/Image:G2_front2.jpg#filehistory
16. Operation Of Flywheel
• Energy held in Spinning
Rotor (Steel or Carbon
composite)
• Steel rotors can spin at
several thousand rpm
• Carbon composite spin
up to 60k rpm
• Kinetic Energy 1/2mv2
http://www.aretepower.us/images/Composite%20Flywheel%20Rotor.jpg
17. Bearings
• Mechanical bearings not
practical
• Friction is directly
proportional to speed
• Magnetic bearings used
to minimize friction
• Rotor is suspended-
state of levitation
• Operates in a Vacuum
18. Superconductors
• New technology uses high temperature
superconductors (HTSC)
• HTSC operate at -1960C or -3210F
• Diamagnetism- creates a field of opposition to a
magnetic field
• Hybrid systems use conventional magnets to levitate
and superconductors to stabilize
19. Energy Stats
Composite Flywheel Li-ion Battery
Cycles 100,000 to 10 million Around 1200
Energy Density 130 Wh/kg 160 Wh/kg
Capacity Range from 3 kWh to
Max of 133 KWh
Equal to 13,825 18650
Li-ion
Over 4 times what is
used to power the Tesla
Charge Time 15 min Several Hours
Self discharge time “0 run down time”- Years 10-20 months
Energy Exchange Limited by generator Limited by chemical
process
