18.0 Energy Storage

Frank R. Leslie, B. S. E. E., M. S. Space Technology, LS IEEE

3/26/2010, Rev. 2.0

fleslie @fit.edu; (321) 674-7377

www.fit.edu/~fleslie

Crude oil $81 on 3/26/10

In Other News . . .

Texas-Size Battery The hoped-for remedy is a battery, a Texas-size

battery, which could eventually end up playing an important role in wider use of green power generation such as solar and wind. The U.S. $25 million system, which is now charging and is set to be dedicated April 8, will be the largest use of this energy storage technology in the United States.

The four-megawatt sodium-sulfur (NaS) battery system consists of 80 modules, 8,000 pounds (3,600 kilograms) each, constructed by the Japanese firm NGK-Locke. They were shipped to Long Beach, California, in December and transported to Texas aboard 24 trucks.

The cost of the battery system includes $10 million just to construct the building in which it will be housed and the new substation it requires.

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http://news.nationalgeographic.com/news/2010/03/100325-presidio-texas-battery/

18 Overview: Energy Storage

Energy is stored to use it at a different time than when it was generated

The process of converting the energy to storable form means that some energy is lost due to inefficiency and heat

Additional energy is lost when the energy is released or recovered due to a second inefficiency

Ideally, storage is avoided to have a more efficient process

Time-of-day metering is likely in the future as metering becomes electronic and inexpensive (like a thermostat)

Shifting the energy from usage peaks to low-use times helps the utility, and customers would be rewarded by lower charges

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18.0 About This Presentation

18.1 General18.2 History18.3 Flywheels18.4 Ultracapacitors18.5 Pumped Hydro18.6 Compressed Gas Storage; H2

18.7 Superconductors18.8 Ice Storage18.9 Financial Storage18.10 Renewable Energy Funding18.11 Issues and Trends18.0 Conclusion

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Renewable energy is often intermittent (like wind and sun), and storage allows use at a convenient time

Compressed air, flywheels, weight-shifting (pumped water storage) are developing technologies

Batteries are traditional for small systems and electric vehicles; grid storage is a financial alternative

Energy may be stored financially as credits in the electrical “grid”

“Net metering” provides the same cost as sale dollars to the supplier; 37 states’ law; new law needed in Florida

18.1 Energy Storage

www.strawbilt.org/systems/ details.solar_electric.html070403

18.2 Battery History

Alessandro Volta made primary batteries of dissimilar metals (silver, zinc, and a salt water wet paper between them) about 1800 (try touching a dime and a nickel in contact to your tongue)They were “piled” up, and became known as a voltaic pile

(from whence came the atomic pile) Johann Ritter developed a rechargeable (secondary) cell

about 1802, but there was no generator to recharge them yet George Leclanche’ “wet” cells used carbon rods and zinc

He made a wet paste that could be sealed into the cell, thus making a convenient portable energy source; no spilling

In 1860, the secondary or rechargeable battery was further developed by Raymond Gaston Planté (lead sheets & acid)

A lead paste on the plates provided more active surface area and allowed longer discharge life in 1881 (Faure)

Germans made the gel-cell with a sealed case in 1960080331

18.2 Electrochemical Batteries

Batteries (groups; from artillery guns) of cells are used separately or in a case containing several cells; a 12V car battery has six 2V cells inside the case

Large batteries are often use separate 2V cells placed next to each other in a rectangle

Various cell chemistries are usedLead-acid; Nickel-cadmium; LithiumNickel-metal hydrideZinc-air

Best suited to storage periods of 1 second to 60 days Self-discharge and sulphation occur with timeDesulphator circuits can reduce sulfates for longer life

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18.2 Flow Batteries

Flow batteries use pumped electrolytes that move outside of the battery casePolysulfide Bromide (PSB), Vanadium Redox

(VRB), Zinc Bromine (ZnBr), and Hydrogen Bromine (H-Br) batteries are examples

A “filling station” could exchange spent electrolyte for new “charged” electrolyte

The power and energy ratings are thus independent since the power is from the battery electrodes while the electrolyte may be replaced periodically

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18.3 Flywheels

070403 http://www.et.anl.gov/sections/te/research/flywheel.html

Flywheels store energy as angular momentumBest suited to storage periods of 1 second to 10

minutes High temperature superconducting bearings reduce

bearing friction to 2% of speed drop per dayBall bearings are so inexpensive that the performance

gains of magnetic bearings are irrelevantThe flywheel case is designed with a shield to contain

a failed rotor and its pieces if it shatters and blows upBatteries are much cheaper than flywheel systemsTest buses used flywheels that were spun up by

electricity at bus stops; no wires along streets

18.3 Flywheels & Trains

050404 http://www.et.anl.gov/sections/te/research/flywheel.html

This trackside flywheel system provides stabilization of voltages on the track system by being both motor and generator

Similar types are used to stabilize renewable energy outputs

Buses have been operated that use flywheels charged by electricity at the bus stops, thus avoiding the cost of overhead trolley wires

http://www.uptenergy.com/

http://www.uptenergy.com/en/traction/casestudy2.htm

18.4 Ultracapacitors

Ultracapacitors are very high capacitance units Best suited to storage periods of 0.1 second to 10

seconds Stored energy is 0.5 C V2

Capacitances now reach 2.7 kF (kilofarad)Carbon electrode surface areas 1000m2 to

2000m2 per gram provide high capacitanceElectrolytes are sulfuric acid or potassium

hydroxide

030331 http://aries.www.media.mit.edu/people/aries/portable-power/

18.5 Hydro Pumped Storage

Special turbines can run either to spin an alternator or to act as a pump

This reversibility allows excess electrical energy to be used to pump water to a higher storage reservoir to be used as an energy source later

Since 2.31 ft of elevation has a bottom pressure of one pound per square inch (psi), a head height of 200 ft is equivalent to 86 psi

Japan built a 30MW seawater pumped hydro system at Yanbaru in 1999

Worldwide, pumped hydro is about 90GW, ~3% of total storage, the most widespread high-energy storage technique

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18.5 San Luis, California

http://www.usbr.gov/power/data/sites/sanluis/sanluis.htm

“Each of the eight pumping-generating units has a capacity of 63,000 horsepower [47 MW] as a motor and 53,000 kilowatts as a generator. As a pumping station to fill San Luis Reservoir, each unit lifts 1,375 cubic feet per second at 290 feet total head. As a generating plant, each unit passes 1,640 cubic feet per second at the same head.”Bureau of Reclamation

Note the disparity between motor and generator!?! Perhaps stream flow into storage?

18.5.1 Hydro Examples

http://www.mwhglobal.com/

Pumped hydro systems are installed world wide, but there are limited locations where new dams may be installed

Opposition to dams is increasing, thus political rather than technical factors are restricting the new installations

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18.6 Compressed Air Pumped Storage

"The world's first compressed air energy storage plant was in Germany," Lee Davis (plant manager for the Compressed Air Energy Storage (CAES) Power Plant in McIntosh, Alabama). "The Alabama CAES plant was the first in the United States when it opened in 1991.“

Electrical motors compress air to 1078 psi within underground salt caverns (100 MW); heat is lost in the cavern

On release, natural gas is burned to heat the air again, which then passes through a turbine, spinning an alternator (326 MWe)

The Norton Energy Company plans a similar site using an abandoned limestone mine 35 miles south of Cleveland, Ohio

080331 http://unisci.com/stories/20013/0802016.htmhttp://www.caes.net/mcintosh.html

http://www.acfnewsource.org/science/energy_mine.html

18.6.1 Compressed Air Energy Storage

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http://www.sandia.gov/media/NewsRel/NR2001/norton.htm

18.6.2 Compressed H2 and NG Storage

Hydrogen is normally stored in 8-inch tubes and tanksH2 pressures range

from 2000 to 10,000 psi

Nickel-metal hydride is a solid pellet or powder storage

CNG or compressed natural gas is stored at 3000 psi

080331 http://tbn0.google.com/images?q=tbn:wNbQtldsA8JF3M:http://cache.viewimages.com

18.6.3 Liquid Air Energy Storage

Mitsubishi Heavy Industries is developing LASE (Liquid Air Storage Energy)

The system makes liquid air at nights and weekends for vaporization and electricity generation

The turbine is based upon a rocket motor pumpThis load-shifting provides the economic

incentive to use the systemCould also be done with liquid nitrogen storage

070403 http://en.wikipedia.org/wiki/Liquid_nitrogen_economy

18.7 Superconductors

Since a superconductor has essentially zero resistance, a current once started will flow “forever”

At a later time, energy could be extracted from the superconductor

Since the superconductors must be kept far below usual air temperature (~20K to 80K), energy must be used to compress the gas and make it liquefy

Newer superconductors are being investigated to find ones with a higher critical temperature near room temperature

080331 http://www.accel.de/pages/2_mj_superconducting_magnetic_energy_storage_smes.html

18.7.1 Superconductor Example

030331 http://www.imagesco.com/articles/supercond/08.html

A current is induced in the superconductor toroid by inserting a magnet briefly

Once replaced in the liquid nitrogen, the current circulation can be detected by a compass

Current decay is on the order of 50% in 1020 years

18.8 Ice Thermal Energy Storage

Air conditioning systems have a high afternoon load to offset the sun heating of the building and the higher outside temperature

Freezing ice during the night provides a latent heat absorber at lower energy prices, assuming demand charges or time-of-use rates are imposed

During the day, the ice is melted as the refrigerant is condensed as it passes through pipes in the ice

The overall process thus provides air conditioning at a lower cost

Bayside High School in Palm Bay FL uses this method

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18.9 Financial Storage

Storage of energy as a credit from the utility company can be the most efficient method

No batteries are required with grid intertie, but might be used to provide backup power

In net metering states, a single electrical energy meter is usedEnergy flow moves the meter higher for purchased energy

and lower for energy sold from the local siteThe utility company can avoid meter-reading costs by

reading the meter once a year Since the values are only in accounting books, there is no

energy loss (likely used by the neighbors) However, ~16 states have yet to regulate the charges, and

some utilities may pay $0.023/kWh but charge $0.07 or higher The nonnet-metering system should be designed to reduce the

bill to nearly zero but never sell energy into the utility system

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18.10 Renewable Energy Funding

President Clinton served from 1992 through 2000 During 1992-1999, the Dept. of Energy Renewable Energy

budget varied from $388M to $488M, reaching its low of $363M in 1997

The 1999 DOE RE budget shows these top areas:Electric Energy Systems $38MGeothermal $33MHydrogen Research $24MHydropower $4M

Solar Energy was separated out at $112M to $87M in 1997 to $ 116M in 1999The major budget item in 1999 was biofuels $89M,

followed by PV at $79M Budget at 4/2007 at ~$307M vs. ~$200M

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18.11 Issues and Trends

Energy storage provides energy at a different time than when it was generated (time-shifting)

Conventional storage systems such as batteries and pumped hydro continue to dominate due to cost

Short-term storage or energy-smoothing devices like flywheels and ultracapacitors work well in the 10-second time range

Unneeded generators are often kept in “spinning reserve”, motoring without load to act as generators if additional power is required (air and bearing losses)This also stores reactive power (v.a.r.s or vars)

Energy storage will smooth peaks and valleys of availability, but load shifting by the users is more useful

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18 Conclusion: Energy Storage

Energy storage is to be avoided due to the losses, but may be economic when load time-shifting is possible

Energy must be stored in vehicles since they cannot obtain sufficient power from wind or sun on the vehicle Special student SunRayce PV cars are fragile

and light, and cannot be used in normal highway traffic without a significant death rate

Protected by team cars travelling with themNewer technologies may increase energy storage

density at a lower cost; both are needed for a viable product

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Olin Engineering Complex 4.7 kW Solar PV Roof Array

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Questions?

References: Books

Boyle, Godfrey. Renewable Energy, Second Edition. Oxford: Oxford University Press, 2004, ISBN 0-19-26178-4. (my preferred text)

Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76, 333.79’4’0973.

Duffie, John and William A. Beckman. Solar Engineering of Thermal Processes. NY: John Wiley & Sons, Inc., 920 pp., 1991

Gipe, Paul. Wind Energy for Home & Business. White River Junction, VT: Chelsea Green Pub. Co., 1993. 0-930031-64-4, TJ820.G57, 621.4’5

Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136

Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-12-656152-4.

Texter, [MIT]

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References: Websites, etc.

http://www.mhi.co.jp/tech/htm/8353t/e835305t.htm liquid air energy storagehttp://unisci.com/stories/20013/0802016.htm on compressed air storagehttp://www.aip.org/isns/reports/2001/025.html on compressed air storagehttp://www.sandia.gov/media/NewsRel/NR2001/norton.htm on compressed air storagehttp://www.eere.energy.gov/der/compressed_air.htmlhttp://www.hepi.com/basics/history.htm batterieshttp://www.et.anl.gov/sections/te/research/flywheel.html flywheelshttp://www.aspes.ch/faq.htmlhttp://www.netl.doe.gov/publications/proceedings/01/hybrids/Hybrid%20Workshop%20Group%203%20Breakout

%20NREL.pdfhttp://www.netl.doe.gov/publications/proceedings/01/hybrids/http://www.electricitystorage.org/sitemap.htmhttp://www.uptenergy.com/en/traction/casestudy2.htm on electric Chinese bushttp://www.acfnewsource.org/science/energy_mine.html

______________________________________________________________________________www.dieoff.org. Site devoted to the decline of energy and effects upon populationwww.ferc.gov/ Federal Energy Regulatory Commissionwww.google.com/search?q=%22renewable+energy+course%22solstice.crest.org/dataweb.usbr.gov/html/powerplant_selection.html

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