What do you think the power from a wind turbine looks like over the course of a month?

What do you think the power from a solar panel looks like over the course of a day?

There is a need to store energy if your supply isn’t constant

Grid Energy Storage
What is the maximum power capacity needed here?

Grid Energy Storage
What is unrealistic about this example?

Total Grid Energy Storage: >250 GW
 Most is pumped hydro

Pumped hydro storage:
(Example ---
Luddington, Michigan)

New Taum Sauk Reservoir

Pumped hydro storage: ~ 70-85% efficient
 First used in 1890’s in Italy and Switzerland
 ~22 GW of power storage in the US
 Largest is in Bath County, VA  3 GW

Batteries: 50 to >90% efficient
1917 English gasoline engine with 16 batteries that could supply
4.5 amps at 32 V for 7.5 hours

Batteries:

Batteries:

Batteries:
 Lead-Acid Battery

Traditional Batteries: Expensive, high maintenance, and limited lifetimes, but can supply large power for short amounts of time
 Many new compositions are being explored (lithium iron phosphate, sodium-sulfur, vanadium, etc.)
 A system in Puerto Rico has a capacity of 20 MW for 15 minutes (5 MWhr)
 A system in a remote area of Fairbanks (Alaska) provides
27 MW for 15 minutes (6.75 MWhr)

Experimental: Liquid Metal Batteries

Experimental: Liquid Metal Batteries
 Initially Magnesium/Anitmony; now Lead/Antimony
 Operates at 350-430 ° C (cooler than previous alloys)
 Energy storage efficiency of 70% (down to 60% after 10 yrs)
 Cost is $500/kWhr (needs to get down to ~$100/kWhr)

Experimental: Liquid Metal Batteries
 Liquid is mobile (so more efficient)

 Many computer systems are hooked to UPCs
(uninterruptible power supplies)

Compressed Air Energy Storage (CAES): Usually <60% efficiency
 McIntosh, Alabama  27 efficiency http://www.powersouth.com/mcintosh_power_plant/compre ssed_air_energy

Where is energy lost?

Where is energy lost?

Compressed Air: New technology involving adiabatic storage and retrieve (heat is retained with high insulation)
 German ADELE plant in development (2015?)
 Will operate at ~70% efficiency
But then need a way to store heat (as hot oil, up to 300 ° C, or as molten salt, up to 600 ° C)

Compressed Air Energy Storage: Good geologic locations are salt layers and aquifers
Why?

Compressed Air Energy Storage: Good geologic locations are salt layers and aquifers
Why?
How could you make a salt cavern?

Flywheels: Small, but fast retrieval of power
Beacon Power has a 20 MW flywheel energy storage plant in
Stephentown, NY

Flywheels:
Beacon Power has a 20 MW flywheel energy storage plant in
Stephentown, NY
What happens if it gets too big?

Size vs. Retrieval Time:

Total Grid Energy Storage: >250 GW

Hydrogen Storage: Energy can be converted into hydrogen by:
1) Steam reformation of hydrocarbons
2) Water electrolysis

Hydrogen Storage: Energy can be converted into hydrogen by:
1) Steam reformation of hydrocarbons (~65%-75% efficient)
Steam reacts with hydrocarbons (usually methane) to release hydrogen gas
Ex/ 2-step process starting with methane:
A) CH
4
+ H
2
O  CO + 3H
2
(“methanation”)
B) CO + H
2
O  CO
2
+ 3H
2
(“water-gas shift”)

Hydrogen Storage: Energy can be converted into hydrogen by:
2) Water electrolysis (~30-45% efficient): The decomposition of water (H
2
O) into oxygen gas (O
2
) and hydrogen gas (H
2
) by passing an electric current through the water.

Water electrolysis

Hydrogen Fuel Cells: The released hydrogen can then be compressed, transported and used for hydrogen fuel cell technology

Hydrogen Fuel
Cells:
In a hydrogen fuel cell, the reverse of hydrolysis happens
 The hydrogen and oxygen combine to make water, driving an electric current

Hydrogen Fuel Cell Cars: Target availability = 2015
Honda Clarity can now be leased in California for $600/mo
 Production costs have dropped from $1M/car to about
$120K/car

Electric Cars: Thomas Edison and a Detroit electric car, 1913

Electric Cars: Nissan Leaf – best selling electric car
 55,000 sold by March, 2013

Electric Cars: Tesla (Roadster - $110,00) and Model S Sedan
($57,000). Soon, the Bluestar (~$30,000) http://www.youtube.com/watch?v=oLiLGTqzfBU

98% of Evs use Lithium-ion batteries
 Expensive, but high energy density

Tesla ESS (energy storage system) uses 6831 lithium cells

87% of Hybrid Cars use NiMH (Nickel-Metal Hydride)
 Half the energy density and cost
 The Prius uses a battery back of 168 NiMH cells that are
1.2 V each

Salar de Uyuni (Andes Mountains, Bolivia), salt polygons:

Salar de Uyuni, mirror-like quality

Salar de Uyuni: Harvesting Salt

Salar de Uyuni, brine beneath salt crust

Lithium plant at Salar de Uyuni

Lithium plant at Atacama Salt Flats (Chile)

Hydrogen Fuel Cell vs. Electric Cars: EVs more efficient

It is still not clear which technology for cars will dominate:
Hydrogen Fuel Cells vs. Electric Cars
(Each has plenty of pros and cons)