mechanical energy storage

1. Mechanical Energy Storage
Created by Nick Stroud

2. Three Types of Storage
• Pumped hydroelectric
storage (PHS)
• Compressed air energy
storage (CAES)
• Flywheels

3. 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.

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. FlowAir
• After 35 mph only 1/2 the
CO2 emissions of Prius
• Takes advantage of light
engine and light frame to be
efficient
• Uses fiberglass frame filled
with foam
• May lose efficiency in cold
weather

13. 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

14. 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

15. 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

16. 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

17. 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. Flywheels Vs. Batteries
Pros
• Not effected by
temperature changes
• No Memory Effect
• Made more
environmentally friendly
• Easy energy content
identification
Cons
• Shattering due to
overload
• Safety devices add lots
of mass
• Gyroscope (duel FES
systems)

20. 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

21. •Flywheels have High
volumetric density

22. Flywheel Projects
• Gyrobuses- used in
1950s in Switzerland
• Buses run off of
Flywheels
• Never gained economic
foothold
• Low fuel costs
compared to electricity

23. Flywheel Projects
• Flywheels used in electric
trains to carry over gaps and
regenerative breaking
• Some car models tried
(Rosen Motors)
• Formula 1 competition
• Used on systems that need
Uninterrupted power supply.
(maintenance 1/2 cost of
battery)
• Testing of fuses

24. Sources
• http://photo.proaktiva.eu/digest/2008_gyrobus.html
• http://eco-energy.info/asp/index.asp?uc=&k=3165
• http://www1.eere.energy.gov/femp/pdfs/fta_flywheel.pdf
• http://www.vyconenergy.com/pages/flywheeltech.htm
• http://www.isepa.com/about_isep.asp
• http://finance.yahoo.com/family-home/article/106040/Air-Cars:-
A-New-Wind-for-America's-Roads
• http://gas2.org/2008/07/15/an-air-car-you-could-see-in-2009-
zpms-106-mpg-compressed-air-hybrid/
• http://zeropollutionmotors.us/