Energy storage for smart grid and renewables v1

Energy Storage for Renewables and MicroGrids

John PappasCenter for Electromechanics

The University of Texas at Austin

Center Experience

• 100+ researchers into energy storage, smart grid, and energy technology

• Working for seven years on “Smart Grid” for DoD

• Storage programs in flywheels, batteries, ultracaps, compressed air, and thermal

Reconfiguration approach handles:• Fuel minimization• Power system protection• Damage mitigation

Reconfiguration via optimization

Using a power objective function

Subject to:

Long history in storage and load leveling systems

Transit Bus Flywheel Battery

• 2 kWhr, 150 kW• 30,000 rpm

Locomotive Load Leveling

• 140 kWhr, 2.5 MW• 15,000 rpm

Examples of demonstrated systems

Utility Storage Flywheel

• Pendulum-mounted steel and reinforced flywheel– Very large l/d– Sited in ground

• No additional containment• Vacuum barrier

– Surface mounted Motor/generator, bearings, gimbal

• Life cycle cost lower than batteries

• Initial cost competitive with batteries

Why CEM’s Focus on Utility Storage?

• Storage is widely recognized as critical in future power systems– Storage enhances insertion of renewables– Storage defers need for new transmission lines– Storage is needed for stability– Storage opens new opportunities for grid

optimization

Today’s Technology

• In today’s grid– Batteries– CAES– Flywheels– Pumped hydro– Thermal storage

• All work

So, impediment is not solely lack of technology

Critical Questions• Where to add storage to grid?– Sources• Does little for peak congestion

– Nodes• Likely requires largest scale

– Loads• Argument for PHEV’s

– May be better argument for stationary systems

• What are the real costs, who pays, who benefits?

“Which is best technology?” is not a critical question

Technology Comparisons

• Given differing maturities, direct technology comparison misleading

• Level playing field by comparing energy lostEnergy lost = Energy lost putting it into storage*

plusEnergy lost while in storage

plusEnergy lost retrieving from storage*

* Includes opportunity loss if there is a mismatch with the power demand

Basic Efficiency - Data Summary

Too much uncertainty to predict ultimate best choice

Turn around efficiency

Charge time (hr)

Self-discharge time (day)

Operating Power (MW)

Capital cost of storedEnergy ($/Whr)

Total stored energyAvailable (MWhr)

Initial Cost of power ($/W)

O&M , Installation, Space

Total initial cost ($)

Total initial cost ($/W)

CAES Tank Battery (Lead Acid)

Battery (NiCad)

Battery(Li lon)

Super Capacitor

Composite Flywheel

Steel Flywheel

0.55

4.0

2000

1

0.17

4

0.70

1,380,000

1.38

0.85

4.0

2000

1

0.2

4

0.225

1,025,000

1.03

0.58

4.0

33

1

0.46

4

0.225

2,065,000

2.07

0.90

4.0

2000

1

1.33

4

0.78

6,100,000

6.10

0.80

4.0

33

1

0.5

4

0.40

2,400,000

2.40

0.90

4.0

1

1

1.0

4

0.28

4,280,000

4.28

0.90

4.0

0.55

1

0.4

4

0.28

1,800,000

1.80

Initial Cost of Delivered Energy

R&D moving flywheel cross-over to 10+ hours

Cost

per

Watt

-hr (

$/W

hr)

Hours Stored10

4.00

3.00

2.00

1.00

0.50

0.00

CAESLead acidNiCadLi lonSuper CapComp FWSteel FW

9 8 7 6 5 4 3 2 1 0

Smart Grid

• Attributes– Permit active participation by consumers – Accommodate generation and storage options – Enable new products, services, and markets – Provide power quality – Operate efficiently – Reconfigure in response to system disturbances

• Technology– Traditional power engineering– Computing– Telecommunications

Smart Grid is Growing in Two Directions

• Top down– Large scale wind farms– Smart meters

• Bottom up– Microgrids

• Neighborhoods• Industry• Universities• DoD facilities• Urban environments

Microgrid Considerations

• Understanding source efficiency vs. power demand helps assess storage applicability

Spec

ific

Fuel

Con

sum

ption

(kg/

KWH

r) x

Power (MW)

0

Gas Turbine Performance0.7

0.6

0.5

0.4

0.3

0.25 10 15 20 25 30 35 40 45 50

(P1,x1)

(P2,x2)

Load Leveling Via Storage in Microgrid

• Analytical study comparing external storage vs. using microgrid as storage to achieve load leveling

Duty Cycle About the Mean Operating Point

0

0.3

0.2

0.1

0.010 20 30 40 50 60 70

Store Efficiency Function

Fuel consumption Function

Storage becomeseconomical

Load Leveling

Benefits From Point Design Analyses

• Analyses of specific technologies in a point application is the best way to make comparisons– Choice among storage technologies and no explicit storage

depends on temporal variations within a microgrid – Operating economics can be properly compared to other

technological imperatives• Storage system response times• Effect on operating cost of systems other than storage• Cost of space used for storage and other systems

• Technology choices are driven by very specific needs

Summary

• Storage critical for “Smart Grid”– Most agree, but assume different applications

• Excellent storage choices exist today• With R&D, better choices will exist in the future• Evolution of “Smart Grid” is a work in progress– Storage can help shape the evolution