energy storage presentation - solar energy at sdsu

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

1


Overview

•! Benefits of Storage

•! Storage Technologies

•! AB 2514

•! Future Research and Projects

2


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

3


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

4


Energy Storage vs Peaker Plant

5


Energy Forecasting

•! When forecasts are high, plants ramp down

their utilization rate

•! Adjusting output lowers efficiency

•! Stresses systems and decreases the lifespan

of equipment

6


Renewable Energy Storage

•! Renewables produce intermittent output

•! Renewable energy production time-shift to

peak demand

•! Power becomes dispatchable and more

predictable

7


Off peak storage

•! Time shift of energy

production

•! Increased efficiency

and utilization rate of

baseload plants

8


Storage Technologies

•! Pumped Hydro

•! Thermal

•! Batteries

•! Compressed Air

•! Molten Salt

•! Flywheels 9

www.storagealliance.org

Current as of April 2010


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 10

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


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

11


Thermal Storage

•! Stored primarily as

cooled fluid or ice

produced at night to

offset air conditioning

electricity demand

12


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%

13


Molten Salt

•! Andasol solar power station in

Spain consists of two 50 MW

solar thermal trough plants

utilizing molten salt storage

•! Storage almost doubles

operational 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

14


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

15


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 operation for 50 minutes

16


Batteries

•! Electrical energy

stored in chemical

form

•! Several different types

of large scale batteries

available

17

www.electricitystorage.org


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

18


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


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 20


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

21


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

22


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

23


Future Research and Projects

•! Vehicle-to-grid

•! Phase Change Materials for Energy Storage

•! Concentrating Solar Brayton CAES

•! Advanced Adiabatic CAES

•! Iowa Stored Energy Park

24


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

25


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

26


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

27


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%

28


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

29

energy storage presentation - solar energy at sdsu

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