California's Electricity Demand Patterns

• Typical spring day demand: starts growing 6 AM, rises again 6 PM
• Wind power: variable, often picks up at night, feeds CA power grid
• Solar panels: kick in 7 AM, generate until sunset ~7 PM
• Neither wind nor solar meets peak demand on most days
• Power companies rely on fossil fuels (natural gas) to fill gap
  • Gap widens significantly during peak electricity usage times
  • Fossil fuels storable in barrels/tanks, unlike renewable energy
• Major gap in renewable energy system: inability to store solar/wind energy
• Risk: continued fossil fuel dependence without energy storage solutions

Lithium-Ion Battery Limitations for Grid Storage

• Batteries improved immensely in recent years, particularly lithium-ion
• Use chemical reactions to store energy
• Individual homes with solar panels often use lithium-ion storage
• Grid-scale problems with lithium-ion:
  • Scale issue: need massive amounts not currently available
  • Lithium scarcity: only found in few places on Earth
  • Better suited for mobile applications (electric cars, portable electronics)
  • Relatively light weight advantage wasted on stationary power grids

Pumped Storage Hydro Technology

• Long-established technology: first built in Europe, US built first in 1929
• Major expansion in 1970s-80s for nuclear power storage
• Global presence: 39 facilities in US alone
• Operating mechanism:
  • Low demand: renewable/fossil fuel energy pumps water uphill to higher reservoir
  • Converts electrical energy to potential energy
  • High demand: water released downhill, converts to kinetic energy
  • Spins turbine, generates electricity for grid
• Efficiency: ~90% (only 10% energy loss)
• Combines water, mountain, gravity into battery system
• Construction challenges:
  • Requires mountains
  • Must hollow out mountain for pumps
  • High cost
  • Limited geographic availability

Alternative Gravity-Based Storage Solutions

Energy Vault - Gravity Energy Storage

• Uses gravity without water or mountains
• Process: renewable energy lifts heavy concrete blocks into air (potential energy)
• Energy release: blocks dropped, spin turbine, convert back to electricity
• Claimed efficiency: >80%
• Still in testing phase

Quidnet - Geomechanical Pumped Storage

• Underground water storage system
• Pumps water underground into pressurized hole using renewable energy
• Stores as potential energy
• Releases water back to surface to spin turbine and generate electricity

Other Emerging Storage Technologies

Thermal Energy Storage

• Uses renewable energy to super-heat salt
• Insulates heated salt
• Releases heat to create steam/hot air for turbine operation
• Converts renewables to thermal energy storage

Iron-Air Batteries

• Utilizes rust chemical reaction for energy storage/discharge
• Converts rust formation process into useful energy storage mechanism

Industry Development and Future Outlook

• All technologies in various development stages
• Attracting investor interest
• Multiple solutions needed: one size doesn't fit all power grids
• Grid requires patchwork approach like renewable energy overall
• Testing multiple solutions helps determine optimal mix for future grid needs