Supercapacitors for EV and Grid-Scale Energy Storage

Silverberg8 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 cm3)• 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. 2015

Key Metrics for Comparison

*Energy density

Capacitor

C = = E = ½ CV2

• Energy density: 0.01 Wh/kg• Power density: 10 kW/kg• 500,000 cycles

Supercapacitor

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

Battery vs. Capacitors

Li-ion Battery Capacitor Supercapacitor

Charge Time 600 s 0.001 s 10 s

Cycle Life 1000 500,000 500,000

Specific Energy 150 Wh/kg 0.01 Wh/kg 5 Wh/kg

Specific Power 1 kW/kg 10 kW/kg 10 kW/kg

Energy Cost $1/Wh $5000/Wh $20/Wh

Solar Power Smoothing

Solar Power Smoothing

UCSD microgrid provides 90% of campus power

22 kW CPV with 2.5 kWh supercap

Scale of problem is TBD

0 100 200 300 400 500 600 700 800 900 1000010203040506070

Time (s)

Velo

city

(km

/h)

Regenerative Braking

ARTEMIS by INRETS

Regenerative Braking

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 Battery Capacitor Supercapacitor

Charge Time 600 s 0.001 s 10 s

Cycle Life 1000 500,000 500,000

Specific Energy 150 Wh/kg 0.01 Wh/kg 5 Wh/kg

Specific Power 1 kW/kg 10 kW/kg 10 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. 2015

Graphene, theory

Graphene, expt

Energy Density is the key

Graphene supercapacitors

2007200820092010201120122013201420150

100

200

300

400

500

600

GSCsTypical SupercapacitorGraphene Theoretical

Year

Spec

ific

Capa

citr

ance

(F/g

) >100 Wh/kg

Graphene supercapacitors @ UCLA

https://vimeo.com/51873011

Graphene supercapacitors @ UCLA

http://www.sunvaultenergy.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