Supercapacitors for EV and Grid-Scale Energy Storage Silverberg 8 Oct 2015

Outline Context – Why do we need energy storage? – What is a supercapacitor? – What can supercapacitors do for us? Research: Graphene supercapacitors Industry: Sunvault, Maxwell, Volvo

Functions for Energy Storage Portable electronics (5-100 Wh, <50 cm 3 ) Transport (50 – 100 kWh, 500 kg)  main, regenerative, start/stop Grid-scale (MWh, cost)  meeting peak load, smoothing renewable

Grid-Scale Energy Storage DoE, 2013

Key Metrics for Comparison *Cycle life

Electric Vehicle Energy Storage Li-ion battery

Zhang et al Key Metrics for Comparison *Energy density

Capacitor

Supercapacitor Energy density increase to ~5-10 Wh/kg

Battery vs. Capacitors Li-ion BatteryCapacitorSupercapacitor Charge Time 600 s0.001 s10 s Cycle Life ,000 Specific Energy 150 Wh/kg0.01 Wh/kg5 Wh/kg Specific Power 1 kW/kg10 kW/kg Energy Cost $1/Wh$5000/Wh$20/Wh

Solar Power Smoothing

UCSD microgrid provides 90% of campus power 22 kW CPV with 2.5 kWh supercap Scale of problem is TBD

Regenerative Braking ARTEMIS by INRETS

Regenerative Braking

Philadelphia SEPTA subway 10-30% reduction in grid-use Also acts as grid storage

Future Application: EV/Small Grid-Scale Storage Li-ion BatteryCapacitorSupercapacitor Charge Time 600 s0.001 s10 s Cycle Life ,000 Specific Energy 150 Wh/kg0.01 Wh/kg5 Wh/kg Specific Power 1 kW/kg10 kW/kg Energy Cost $1/Wh$5000/Wh$20/Wh

Graphene Specific Capacitance  Specific Energy

Theoretical single layer graphene: over 100 Wh/kg Zhang et al Graphene, theory Graphene, expt Energy Density is the key

Graphene supercapacitors >100 Wh/kg

Graphene UCLA

Graphene UCLA

com/web20/video-updates/ SunVault “The company has had 4 different names since 2010 and 2 different business lines. There is little technical detail in the company's press releases and website to support its claims. The majority of the company's stock is held by third parties with little information available on them.” – Seeking Alpha “A company no one has ever heard of is using technology no one has ever heard of to make a car with 1,000 lb-ft of torque that will blow the doors off any Tesla, Ferrari or McLaren every made. And it will be ready in 6 months.” –Ecomento “Sunvault Energy Inc (OTCMKTS:SVLT) Stock Surges For No Apparent Reason” - HotStocked

Volvo Energy Panels, 2013

Maxwell & GM Partnership, Sep 2015 Start-stop technology

Outlook Continued use for high power, low energy applications – Regen braking – Start/stop – High-frequency smoothing With further energy density improvements – EV power – Larger grid-scale applications

Supp: Parameters for Supercap Optimization