SESSION TITLEDr. H. Pirouz KavehpourProfessor & Vice Chair, Mech. & Aerospace Eng. University of California, Los AngelesUSA

Energy Storage System for Solar Energy Systems from Utility Scale to Small ScaleOver-rated and Under-rated Parameters and Alternatives to Batteries

Why Storage is Needed

Applications of energy storageLack of availabilityHigh cost of energy at different time (Energy business)Renewables

Agenda

Energy Storage technologiesApplications from utilities based to behind the meterReview of available technologies

Key ConceptsPower vs. EnergyDischarge timeChallenges

Conclusions

Energy Storage MethodsEnergy Storage

Mechanical Chemical Electromagnetic Thermal

Pumped Hydro

Compressed Air (CAES)

Flywheel Batteries Hydrogen

Capacitors

SensibleHeat

LatentHeat

Superconducting Magnetic Flow Batteries

Solid State

Brahim Dincer, Marc Rosen, (2011) “Thermal Energy Storage, Systems and Applications” Second Editions

Thermochemical

Energy Storage Technologies

Mechanical SystemsPump-HydroCompressed air energy storage (CAES)Flywheels

Non-Mechanical SystemsBatteriesSuper CapacitorsSuperconducting Magnetic Energy Storage

Pump-HydroWorks based on hydro-power plant concept

Compressed Air Energy Storage

Based on combination of gas turbine technology and Brayton Cycle

FlywheelBased on Newton’s first law

BatteriesSeveral types of batteries are available for different storage applications

• High power• High energy density

Other TechnologiesSuper Capacitors• Super-conducting Magnetic Energy Storage (SMES)

• High power• Very short discharge time

Energy Storage Space

Power vs. Energy• Power

• The ability to work• Unit: kW, MW• Large power is needed for for large

applications.• Utility scale storage provides high

power, while residential scale requires lower power.

• Energy• Energy is a property of objects which

can be transferred to other objects or converted into different forms, but cannot be created or destroyed.

• Unit: kWh, Jouls• Energy per unit time is Power.

We store Energy not Power

Discharge time• Time of dispatching the energy at a given power.• Different applications requires different discharge time.

• Residential ratchet charge requires short discharge times.• Frequency regulating requires very rapid discharge times.• For most of renewable energy, longer discharge times are desired.

• Batteries are not capable of longer discharge time yet.• Pump-hydro and CAES can provide longer times.

Key Challenges

“Important” Parameters• Efficiency• $/kW.hr• $/kW• LCOE

Efficiency of Energy Storage System

• “Round trip” Efficiency• Different than “thermodynamic efficiency”

• How important is efficiency?• Depends on whom you asked!

Cost of Energy Stored$/kW.hr

Cost of Power Produced$/kW

• Is this a correct formula?• Does this make sense for energy storage?

Levelized Cost of Energy• LCOE

• LCOE is equivalent to the cost of energy stored.• If LCOE is larger than cost of Energy purchased, energy storage business fails.

• Government incentives are important.• But is that all? LCOE doesn’t tell you everything you need to know!

Conclusions• Both power and discharge time are very important for an energy storage system.• Batteries are capable of very short to intermediate discharge times

• Very suitable for demand peak shaving and frequency regulations.

• Pump-hydro and CAES are suitable for high power, long discharge time.• Relatively longer ramp time, limits these systems to longer respond time applications.

• Efficiency is important only if it is worth it.• Cost, Cost, Cost!!!

HeadingTHANK YOUFOR ATTENDING THE PRESENTATION