18.0 Energy Storage

1. 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

2. 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. http://news.nationalgeographic.com/news/2010/03/100325-presidio-texas-battery/ 100326

3. 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 100326

4. 18.0 About This Presentation • 18.1 General • 18.2 History • 18.3 Flywheels • 18.4 Ultracapacitors • 18.5 Pumped Hydro • 18.6 Compressed Gas Storage; H2 • 18.7 Superconductors • 18.8 Ice Storage • 18.9 Financial Storage • 18.10 Renewable Energy Funding • 18.11 Issues and Trends • 18.0 Conclusion 090330

5. 18.1 Energy Storage • 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 070403 www.strawbilt.org/systems/ details.solar_electric.html

6. 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 1960 080331

7. 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 used • Lead-acid; Nickel-cadmium; Lithium • Nickel-metal hydride • Zinc-air • Best suited to storage periods of 1 second to 60 days • Self-discharge and sulphation occur with time • Desulphator circuits can reduce sulfates for longer life 070403

8. 18.2 Flow Batteries • Flow batteries use pumped electrolytes that move outside of the battery case • Polysulfide 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 050404

9. 18.3 Flywheels • Flywheels store energy as angular momentum • Best suited to storage periods of 1 second to 10 minutes • High temperature superconducting bearings reduce bearing friction to 2% of speed drop per day • Ball bearings are so inexpensive that the performance gains of magnetic bearings are irrelevant • The flywheel case is designed with a shield to contain a failed rotor and its pieces if it shatters and blows up • Batteries are much cheaper than flywheel systems • Test buses used flywheels that were spun up by electricity at bus stops; no wires along streets 070403 http://www.et.anl.gov/sections/te/research/flywheel.html

10. 18.3 Flywheels & Trains • 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/ 050404 http://www.uptenergy.com/en/traction/casestudy2.htm http://www.et.anl.gov/sections/te/research/flywheel.html

11. 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 capacitance • Electrolytes are sulfuric acid or potassium hydroxide 030331 http://aries.www.media.mit.edu/people/aries/portable-power/

12. 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 090331

13. 18.5 San Luis, California “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 http://www.usbr.gov/power/data/sites/sanluis/sanluis.htm Note the disparity between motor and generator!?! Perhaps stream flow into storage?

14. 18.5.1 Hydro Examples 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 050404 http://www.mwhglobal.com/

15. 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 http://www.acfnewsource.org/science/energy_mine.html http://www.caes.net/mcintosh.html 080331 http://unisci.com/stories/20013/0802016.htm

16. 18.6.1 Compressed Air Energy Storage 030331 http://www.sandia.gov/media/NewsRel/NR2001/norton.htm

17. 18.6.2 Compressed H2 and NG Storage • Hydrogen is normally stored in 8-inch tubes and tanks • H2 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. 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 pump • This load-shifting provides the economic incentive to use the system • Could also be done with liquid nitrogen storage http://en.wikipedia.org/wiki/Liquid_nitrogen_economy 070403

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

20. 18.7.1 Superconductor Example • 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 030331 http://www.imagesco.com/articles/supercond/08.html

21. 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 080331

22. 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 used • Energy flow moves the meter higher for purchased energy and lower for energy sold from the local site • The 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 070403

23. 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 $38M • Geothermal $33M • Hydrogen Research $24M • Hydropower $4M • Solar Energy was separated out at $112M to $87M in 1997 to $ 116M in 1999 • The major budget item in 1999 was biofuels $89M, followed by PV at $79M • Budget at 4/2007 at ~$307M vs. ~$200M 080331

24. 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 070403

25. 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 them • Newer technologies may increase energy storage density at a lower cost; both are needed for a viable product 080331

26. Questions? Olin Engineering Complex 4.7 kW Solar PV Roof Array 080116

27. 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] 030319

28. References: Websites, etc. http://www.mhi.co.jp/tech/htm/8353t/e835305t.htm liquid air energy storage http://unisci.com/stories/20013/0802016.htm on compressed air storage http://www.aip.org/isns/reports/2001/025.htmlon compressed air storage http://www.sandia.gov/media/NewsRel/NR2001/norton.htmon compressed air storage http://www.eere.energy.gov/der/compressed_air.html http://www.hepi.com/basics/history.htm batteries http://www.et.anl.gov/sections/te/research/flywheel.html flywheels http://www.aspes.ch/faq.html http://www.netl.doe.gov/publications/proceedings/01/hybrids/Hybrid%20Workshop%20Group%203%20Breakout%20NREL.pdf http://www.netl.doe.gov/publications/proceedings/01/hybrids/ http://www.electricitystorage.org/sitemap.htm http://www.uptenergy.com/en/traction/casestudy2.htm on electric Chinese bus http://www.acfnewsource.org/science/energy_mine.html ______________________________________________________________________________ www.dieoff.org. Site devoted to the decline of energy and effects upon population www.ferc.gov/ Federal Energy Regulatory Commission www.google.com/search?q=%22renewable+energy+course%22 solstice.crest.org/ dataweb.usbr.gov/html/powerplant_selection.html 080331