Energy Storage November 12 th , 2010 SDSU Energy Discussion Group - - PowerPoint PPT Presentation

SDSU Combustion and Solar Energy Laboratory

Energy Storage November 12th, 2010

SDSU Energy Discussion Group Brian Gehring, Graduate Student

• Prof. Fletcher Miller, Advisor

San Diego State University

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SDSU Combustion and Solar Energy Laboratory

Overview

• Benefits of Storage
• Storage Technologies
• AB 2514
• Future Research and Projects

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SDSU Combustion and Solar Energy Laboratory

Benefits of Storage

• Forecasting of electricity demand is difficult
• Makes the electricity grid more flexible, efficient and

reliable

• Production from renewables is sporadic and unpredictable
• Store energy at night when cost and demands are low
• Smarter grid with fewer new power plants
• Lowers capital costs for utilities by reducing annual

peaking requirement – fewer peaker plants available

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SDSU Combustion and Solar Energy Laboratory

Energy Forecasting

• When forecasts are

low, peaker plants are put into operation to meet demand

• Peaker plants are less

efficient and smaller plants are excluded from controlling emissions

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SDSU Combustion and Solar Energy Laboratory

Energy Storage vs Peaker Plant

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SDSU Combustion and Solar Energy Laboratory

Energy Forecasting

• When forecasts are high, plants ramp down

their utilization rate

• Adjusting output lowers efficiency
• Stresses systems and decreases the lifespan
• f equipment

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SDSU Combustion and Solar Energy Laboratory

Renewable Energy Storage

• Renewables produce intermittent output
• Renewable energy production time-shift to

peak demand

• Power becomes dispatchable and more

predictable

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SDSU Combustion and Solar Energy Laboratory

Off peak storage

• Time shift of energy

production

• Increased efficiency

and utilization rate of baseload plants

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SDSU Combustion and Solar Energy Laboratory

Storage Technologies

• Pumped Hydro
• Thermal
• Batteries
• Compressed Air
• Molten Salt
• Flywheels

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www.storagealliance.org Current as of April 2010

SDSU Combustion and Solar Energy Laboratory

Pumped Hydro

• Water is pumped uphill to a reservoir when demand is low, and allowed to run

down through turbines when power is needed

• Most widely utilized energy storage technology
• 98% of total worldwide energy storage capacity
• Limited by existing reservoirs
• Recovers 75% of energy consumed
• High dispatchability, can come online in as little as 15 seconds

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http://www.tva.gov/power/pumpstorart.htm

SDSU Combustion and Solar Energy Laboratory

Pumped Hydro

• SDG&E has contracted with

San Diego Water Authority to build a pumped hydro project

• Will take advantage of 770 ft

elevation difference between Olivenhain reservoir and Lake Hodges

• Will produce 40MW for 8-10

hours

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SDSU Combustion and Solar Energy Laboratory

Thermal Storage

• Stored primarily as

cooled fluid or ice produced at night to

• ffset air conditioning

electricity demand

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SDSU Combustion and Solar Energy Laboratory

Molten Salt

• De-couples the production of

solar energy from producing power

• 60 percent sodium nitrate and

40 percent potassium-nitrate

• Can store energy for up to a

week

• Insulated tanks keep salt from

freezing

• Studies by Sandia show that

two tank storage system could have annual efficiencies as high as 99%

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SDSU Combustion and Solar Energy Laboratory

Molten Salt

• Andasol solar power station in

Spain consists of two 50 MW solar thermal trough plants utilizing molten salt storage

• Storage almost doubles
• perational hours per year
• Full thermal reservoir allows

7.5 hours of full load production

• Each plant has two tanks for

molten salt storage measuring 14m in height and 36m in diameter

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SDSU Combustion and Solar Energy Laboratory

Plants with Molten Salt Storage and Capacities

• Solar II – Power tower in Barstow, CA
• Andasol – Trough in Granada, Spain
• Nevada Solar One – Trough in Nevada
• Exteresol I – Trough in Spain
• La Florida – Trough in Spain
• 10MW – 3hrs
• 2x50MW – 7.5hrs
• 64MW – 30mins
• 50MW – 7.5hrs
• 50WM – 7.5hrs

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SDSU Combustion and Solar Energy Laboratory

Steam Accumulator

• PS 10 solar thermal power

tower in Spain

• Stores heated water in four

pressurized tanks at 50 bar and 285°C

• The water evaporates and

flashes back to steam when the pressure is lowered

• Storage capacity is 50% load
• peration for 50 minutes

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SDSU Combustion and Solar Energy Laboratory

Batteries

• Electrical energy

stored in chemical form

• Several different types
• f large scale batteries

available

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www.electricitystorage.org

SDSU Combustion and Solar Energy Laboratory

Sodium-Sulfur Batteries

• Operating temperatures of 300-350°C
• 89-92% efficient
• Liquid sodium serves as the negative electrode and liquid

sulfur serves as the positive electrode

• Currently 270 MW installed capacity in Japan, 9 MW in

USA

• 7.2 MW installed to support 11 MW wind power farm in

Minnesota

• Rubenius will install 1GW of NaS batteries in Mexicali,

Mexico from single manufacturer - NGK Insulators

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SDSU Combustion and Solar Energy Laboratory

Compressed Air Energy Storage (CAES)

19 www.caliso.com

• Electricity is used to

compress air into large storage tanks or underground caverns

• Compressed air spins

turbines when energy is needed

SDSU Combustion and Solar Energy Laboratory

CAES

• Diabatic Storage
• Currently only one system in US -110 MW

system in McIntosh, Al

• Dissipates heat with intercoolers
• Achieves 53% thermal efficiency
• Requires fuel
• Caverns created by solution mining,

available in 85% of the United States

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SDSU Combustion and Solar Energy Laboratory

Flywheels

• Convert electrical

energy into kinetic energy and back again

• Good for power

conditioning and short term storage

• Efficiency can be as

high as 90%

• Typical capacities run

from 3 kW to 133 kW

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SDSU Combustion and Solar Energy Laboratory

Storage Costs

• CAES and Pumped Hydro $5/kWh

– Depends on availability of geology

• Molten Salt - $50/kWh
• Batteries - $100-200/kWh
• Flywheels - $200-500/kWh

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SDSU Combustion and Solar Energy Laboratory

AB 2514

• Requires investor-owned and publicly owned utilities

to procure new grid connected energy storage systems or the services of such systems with a minimum capacity of:

– 2.25% of peak load by 2014 – 5% of peak load by 2020

• California has 1500 MW of storage or <1% of peak

load

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SDSU Combustion and Solar Energy Laboratory

Future Research and Projects

• Vehicle-to-grid
• Phase Change Materials for Energy Storage
• Concentrating Solar Brayton CAES
• Advanced Adiabatic CAES
• Iowa Stored Energy Park

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SDSU Combustion and Solar Energy Laboratory

Vehicle-to-Grid

• Uses plug in electric vehicles as an energy storage device
• Cars are parked 95% of the time
• Electricity could flow from the car to the power lines and back

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SDSU Combustion and Solar Energy Laboratory

Phase Change Energy Storage

• Takes advantage of heat of fusion of

materials

• Less heat transfer fluid needed, smaller

storage tanks

• Smaller temperature change between

charges

• Capable of storing large amounts of energy

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SDSU Combustion and Solar Energy Laboratory

Concentrating Solar Brayton CAES

• Air is compressed into a salt mine cavity during the night
• During the day, the compressed air is sent to parabolic dishes and heated
• Expanded air drives a turbo-alternator
• Each compressor storage system will serve 30 dishes

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SDSU Combustion and Solar Energy Laboratory

Advanced Adiabatic CAES

– Retains heat produced by compression – Heat stored in a solid such as concrete or a liquid such as molten salt – No utility scale plans to date, efficiency expected to approach 70%

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SDSU Combustion and Solar Energy Laboratory

Iowa Stored Energy Park

• Will use energy stored

from a large wind farm to compress air into an aquifer of sandstone capped by shale

• Storage will amount to a

20 week supply

• 270 MW of generating

capacity

• Anticipated completion

date of 2012

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