sign in sign up
<<
Home , Energy engineering, Salt bridge

Energy storage February 10, 2010

Outline Storage • Types of and measures • Operation of electric plants with Larry Caretto limited ability to store Mechanical 483 • Battery operation and limits Alternative Energy • Energy versus power metrics for energy Engineering II storage • Other systems: flywheels, compressed February 10, 2009 air, supercapacitator, pumped hydro

2

Why do we store energy? What kinds of energy stored?

• To be able to respond to changes in • containers store fuel energy demand in a more efficient manner • Batteries and supercapacitors store – use fluctuates over seasons and electrical energy hours of the day – use fluctuates over seasons • Flywheels and compressed air systems • Most transportation (land, sea, air) store needs to carry onboard energy supplies • storage as latent or • Solar and wind use energy storage to sensible used in heating and balance generation with use cooling systems

3 4

Energy Storage Measures Fuel Energy • Volumetric energy storage in Btu/gallon • Energy per unit (kJ/kg; Btu/lbm) – Gasoline: 109,000 to 125,000 • Energy per unit (kJ/m3; Btu/ft3) – Diesel fuel: 128,000 to 130,000 – Biodiesel: 117,000 to 120,000 • Rate of delivery of energy to and from – Natural gas: 33,000 to 38,000 at 3,000 psi, storage (kW/kg; Btu/hr⋅lbm) 38,000 to 44,000 at 3,600 psi, and ~73,500 • Efficiency (energy out/energy in) as liquefied natural gas (LNG) – 85% ethanol in gasoline: ~80,000 • Life cycles – how many times can the – 85% methanol in gasoline: 56,000 to 66,000 storage device be used – Hydrogen: ~6,500 at 3,000 psi, ~16,000 at – Particularly important for batteries 10,000 psi, and ~30,500 as liquid – Liquefied gas (LPG): ~84,000 5 6 http://www.eere.energy.gov/afdc/altfuel/fuel_comp.html

ME 483 – Alternative Energy Engineering II 1 Energy storage February 10, 2010

Electric Plants Electricity Load • Base load plants run continuously • Power demand varies by day and hour – Produce load that is required 24/7 – CA energy, peak MW growth: 1.25%, 1.35% – Most efficient plants • Renewable Portfolio Standards require • Peak load plants utilities to have renewable generation – Used to satisfy demand peaks – 20% of retail sales by December 31, 2010 in – Often gas turbines that are less efficient California (transmission problems?) – Hydroelectric plants run as peak plants – Papers from WCS AWMA October 2007 because of limited resource conference in next five slides • Distributed Generation – large users • CA Energy Commission – Dave Ashuckian generate their own power • SC Edison – James Woodruff 7 8

LADWP Electricity Rates • Residential normal meter: $0.07288/kWh • Residential time-of-service meter – Monday–Friday, 1–5 pm: $0.14377/kWh – Monday–Friday, 10 am–1 pm: $0.08793/kWh – All other times: $0.03780/kWh • Other services have demand charge (per kW) but lower service charge – High season (June to October) extra – Also have different rates for interruptible or non-interruptible 9 10 http://www.ladwp.com/ladwp/cms/ladwp001646.jsp

11 12

ME 483 – Alternative Energy Engineering II 2 Energy storage February 10, 2010

13 14

New South Wales California Supply Today Analysis of Alternatives

• Following charts from paper by Oxford Environmental Change Institute • Conclude that alternative and energy Harvey, A. and Koopman, S., (1993), ‘Forecasting Hourly Electricity Demand Using Time- Varying Splines’, Journal of the American Statistical Association, 88, 1228-1253. supplies can, when properly planned, meet needs for peak power – Based on models of supply and demand – Wind, solar photovoltaic, and domestic combined heating and power (dCHP) • dCHP not a renewable, but an alternative

15 16

http://www.eci.ox.ac.uk/research/energy/downlo 17 http://www.eci.ox.ac.uk/research/energy/downlo 18 ads/sinden-houseoflords.pdf ads/sinden-houseoflords.pdf

ME 483 – Alternative Energy Engineering II 3 Energy storage February 10, 2010

Supplemental Slides • Slides 52 and later will not be covered in lecture – Provide information on electrical generation system in US – Note sources of energy for generation – Shows electricity costs in various states – Discuss changes in electricity industry to encourage nonutility generators – Considers deregulation of electricity generation in late 1990s with successes and failures http://www.eci.ox.ac.uk/research/energy/downlo 19 20 ads/sinden-houseoflords.pdf

Battery Basics Battery Terms • Zinc/copper cell Reduction at : Oxidation at : • At cathode (left) positive pole, accepts negative pole, supplies ++ – –Cu + 2e → Cu circuit electrons circuit electrons –Cu++ from CuSO4 in solution Copper Zinc goes – electrons from circuit • At anode (right) deposits into solution on cathode at anode • Salt bridge transfers –Zn → Zn++ + 2e– = ++ Lower SO4 ions –Zn ions into Higher ZnSO4 in solution electrode Salt bridge – electrons into potential completes circuit potential circuit 21 in solution 22

Battery Terms II Nernst Equation

• Cell voltage based on standard • Cell potentials are based on a standard reduction potentials (gain of electrons) concentration (1 gram mole per liter), • When two half-cells are joined the pressure (1 atm) and temperature (25oC) reaction with the smaller reduction • Call this potential ΔEo RT ΔE = ΔEo − lnQ potential is run in reverse • Actual potential ΔE nF –Cu++ + 2e– → Cu (0. 34 v) – R = 8.414 J/gmmol·K, T = temperature in K –Zn ++ + 2e– → Zn (–0.76 v) – F = 96485.3415 A·s/gmmol (Faraday const) – Zinc reaction is reversed – n = electrons in reaction – Potential difference is 1.10 v – Q depends on concentrations 23 24

ME 483 – Alternative Energy Engineering II 4 Energy storage February 10, 2010

Battery Types Solar System Batteries

• Nickel Cadmium mature, relatively low • Optional – home systems can sell energy density, long life, lower cost, and high discharge rate excess power to utility • Nickel-Metal Hydride: higher energy • Can provide power during evening density than NiCd but lower cycle life hours for systems not linked to grid • Lead Acid: most economical where weight is not important • Also provide back-up power in cases of • Lithium : high energy density and light blackout weight • Lead-acid batteries uses because of low • Lithium Ion Polymer: Li-ion in smaller cost packaging

25 26

Battery Properties Battery Voltages

27 http://www.mpoweruk.com/chemistries.htm Reference: http://www.intersil.com/data/an/an126.pdf

Discharge Battery Discharge Rates

• Discharge • Manufacturer rates battery to have patterns: certain energy at specified discharge similar with rate known as the “C rate” different • Discharge at higher rates (e.g. 1.5C, batteries 2C, 10C, etc.) reduced capacity • Discharge at lower rates (e.g., C/1.5, C/2, C/10) increases capacity Reference: http://www. mpoweruk.com/ • Similar effect for charging battery performance.htm 29 30

ME 483 – Alternative Energy Engineering II 5 Energy storage February 10, 2010

Battery Discharge Rates Rate Effect

• Higher discharge rates give lower energy • Reference: http://www.na p.edu/books/0 309087007/ht ml/64.html

31 32 Reference: http://www.intersil.com/data/an/an126.pdf

Compare Ragone Plot

• Batteries versus other motive power • http://www.n ap.edu/book s/03090926 12/html/40.h tml http://www.thewatt.com/ modules.php?name=Ne 33 ws&file=article&sid=92634 &mode=nested

Utility Storage Applications

• Power Quality: applied for seconds or less, as needed, to assure continuity of quality power. • Bridging Power: seconds to minutes to assure continuity of service when switching from one source to another. • Energy Management: decouple the timing of generation and consumption of electric energy http://www.electricitystorage. 35 org/tech/technologies_comp 36 arisons_ratings.htm

ME 483 – Alternative Energy Engineering II 6 Energy storage February 10, 2010

Flow Batteries

• Charge and discharge placed in storage tanks – Polysulfide Bromide battery (PSB) – Vanadium battery (VRB) – Zinc bromide • Decouples energy capacity (due to storage tank size) and power (due to cell size) PSB • Sometimes described as fuel cells Schematic

37 http://www.electricitystorage.org/tech/technologies 38 _technologies_psb.htm

PSB Battery Reactions

• Charging reactions - + –Na2S4 + 2e + 2Na → 2Na2S2 - + –3NaBr → 2e + 2 Na + NaBr3 • Discharge reactions - + –2Na2S2 → Na2S4 + 2e + 2Na –NaBr + 2e- + 2 Na+ → 3NaBr VRB 3 Installation • External power charges electrolyte so (Reference next chart)

that tanks contain Na2S2 and NaBr3 • Charged power flow 39 40

Energy Storage Costs

• increases transmission capacity http://www.leonardo- http://www.energy.ca.gov/pier/notices/2005-02- 41 42 24_workshop/07%20Kuntz-VRB%20PacifiCorp%20Flow%20Battery.pdf energy.org/drupal/files/2007/Briefing%20paper%20- %20Flow%20batteries.pdf?download

ME 483 – Alternative Energy Engineering II 7 Energy storage February 10, 2010

Store Compressed Air

•Symbols • CAES: Compressed air energy storage –fully capable • Gas turbine with compressed air stored –reasonable in caverns; later combustion/expansion –feasible, but • Electricity peak shaving not quite… – 290 MW, Hundorf, Germany, 1978 –not feasible – 110 MW, McIntosh, AL, 1991 • $591/kW; comes online in 14 mins – 2700 MW (planned) Norton, OH •http://www.electricit ystorage.org/tech/te • 1500 psi air pressure, 2200 ft underground chnologies_compari 43 http://www.electricitystorage.org/tech/tec 44 sons.htm hnologies_technologies_caes.htm

Pumped Hydro

• Used by power companies to provide peak energy • Pump water uphill during off-peak hours • Use to generate power during peak periods – Same equipment used for pumping and generation – Efficiency range is 70% to 85% – 1566 MW in Castaic http://www.electricitystorage.org/tech/technologies_technologies_caes.htm 45 46

Flywheels Flywheels II

• Store • Efficiency is about 80% for energy out – Exchanged with motor-generator set divided by energy in –E = Iω2/2 I = kmR2 • Can store energy for up to six months • k = ½ for solid disk uniform thickness • Demonstration systems for power • k = 1 for wheel loaded at rim (bicycle tire) quality by Beacon in NY and CA – Centrifugal force = mRω2 can tear flywheel apart so materials that are less dense are • Safety is a concern for use on cars better – Large weight of containment vessels – Carbon fiber disks, loaded at rims, are reduces flywheel advantage of light weight state of the art 47 48

ME 483 – Alternative Energy Engineering II 8 Energy storage February 10, 2010

Pentadyne Power Supercapacitors

• Company in Chatsworth • Alternative material structures to makes flywheel energy conventional capacitors using storage products • Provides similar function: CE = Q – Used for uninterruptible – Q = charge, C = Capacitance, E = voltage power supply – Materials provide larger capacitance – 63 cm x 83 cm x 180 cm • Capable of rapid charging/discharge •590 kg weight – Can link units • Do not store energy for long times – > 99.8% efficiency • Extremely large cycle life – Sizes from 65 to 1000 kVA 49 50

SMES Thermal Energy Storage

• Superconducting • Used to shift energy use from peak storage – Especially used to reduce air conditioning • Store energy in magnetic field loads during summer • High power output for a short period of – Run air conditioning compressors during off peak hours to provide cold temperature time (similar to supercapacitors) energy storage in ice or eutectic salts • Requirement for extremely low – Use stored energy during peak hours to temperatures to maintain provide cooling without any electrical superconductivity compressor input • Used in some utility applications 51 52

Generation (trillion US Electric Generation Supplemental Slides kWh) 10 • Following slides not covered in lecture 9 • Provide more information on electrical 8 7 Data utility system in US and CaliforniaNote Pre-1973 forecast Pre-1973 forecast 6 growth rate is sources of energy for generation 7.8%/year 5

– Show electricity costs in various states 4

– Discuss changes in electricity industry to 3

encourage nonutility generators 2 – Consider deregulation of electricity 1 generation in late 1990s with successes 0 1945 1955 1965 1975 1985 1995 2005 and failures Year

53 Plotted from spreadsheet data downloaded from 54 http://www.eia.doe.gov/emeu/aer/elect.html

ME 483 – Alternative Energy Engineering II 9 Energy storage February 10, 2010

Total = 4.055 billion kWh US Electricity Electric Utility Plants = 63.0% Electricity Use by Sector Independent Power Producers Net Generation, and Combined Heat and Power 2005 Plants = 37.0% 4.0 Other 3.5 Direct Use 3.0 Industrial 2.5

2.0 Commercial 1.5

1.0

0.5 Residential Use (trillions of kilowatt hou kilowatt of (trillions Use

0.0 1994 1996 1998 2000 2002 2004 Plotted from data in spreadsheet downloaded http://www.eia.doe.gov/cneaf/ele55 from http://www.eia.doe.gov/cneaf/electricity/ Year 56 ctricity/epa/figes1.html epa/epa_sum.html

US Electrical Generation Residential Electricity Use 4.0 3.5 )

3.0 Total Nuclear Natural Gas Hydroelectric 2.5 Petroleum Non-hyrdo renewable

2.0

1.5

Plotted 1.0 Generation (trillions kWh (trillions Generation from data in spreadsheet 0.5 downloaded from http://www.eia.0.0 doe.gov/emeu 1990 1995 2000 2005 57 /aer/elect.html 58 Year

Non-hydro Renewable Electrical Generation 0.06 Generation Net US Summer Capacity (trillions kWh)

0.05

0.04 Total Waste Geothermal 0.03 Wood Wind Solar

0.02

Plotted from data in spreadsheet 0.01 downloaded from http://www.eia. doe.gov/emeu0.00 /aer/elect.html 1990 1995 200059 2005 http://www.eia.doe.gov/cneaf/electricity/epa/figes2.html 60 Year

ME 483 – Alternative Energy Engineering II 10 Energy storage February 10, 2010

Electric Industry Fuel Costs

http://www.eia.doe.g ov/cneaf/electricity/e pa/figes3.html 2006 data: gas and oil down; coal up slightly

http://www.cpuc.ca .gov/published/rep ort/GOV_REPORT .htm

61 62

Net Electricity by State 2005 Retail Electric Costs 2005

http://www.eia.doe.go http://www.eia.doe.go v/cneaf/electricity/epa v/cneaf/electricity/epa 63 64 /fig1p1.html /fig7p5.html

Retail Electric Costs 2006 Residential Electric Costs 2005

http://www.eia.doe.go v/cneaf/electricity/epa 65 66 /fig7p5.html

ME 483 – Alternative Energy Engineering II 11 Energy storage February 10, 2010

Commercial Electric Costs 2005 Industrial Electric Costs 2005

http://www.eia.doe.go http://www.eia.doe.go v/cneaf/electricity/epa v/cneaf/electricity/epa 67 68 /fig7p6.html /fig7p7.html

Electricity Sales (kWh/person) A Brief History

• Initial development of industry – Generation mostly by investor-owned, regulated monopolies – Some publicly owned utilities and rural cooperatives – Large industries generate for their own use • PURPA 1978 brings in other generators • EPAct 1992 deregulates generation at

http://www.energy.ca.gov/2007publications/CEC-100-2007-008/CEC-100-2007-008- Federal level CMF.PDF Figure ES-2 69 70

Who Makes Electricity? Non-utility Electric Producers

• Traditional electric utilities • Facilities qualifying under 1978 Public – 239 investor owned utilities supply about Utility Regulatory Policies Act (PURPA) 75% of ultimate customers • facilities producing steam – 2,009 publicly owned utilities and electricity, doing other business – 912 consumer owned rural electric • Independent power producers who sell cooperatives electricity wholesale – 10 Federal electric utilities • Exempt wholesale generators under • About 2,110 non-utility power producers 1992 Act (EPACT) as shown on next chart • http://www.eia.doe.gov/cneaf/electricity/page/prim2/toc2.html

http://www.eia.doe.gov/cneaf/electricity/p 71 72 age/prim2/toc2.html

ME 483 – Alternative Energy Engineering II 12 Energy storage February 10, 2010

Government Agencies What is PURPA?

• Federal Energy Regulatory Commission • Public Utility Regulatory Policies Act 1978 (FERC) regulates interstate – Requires utilities to change rate structures transmission of electricity, oil and gas from earlier ones that encouraged use • Costs per kWh declined with use based on model • State public utilities commissions valid from 1950-1970 regulate investor-owned utilities in state – Convert from oil to gas • State Independent System Operators – Require utilities to purchase power from qualified facilities (QFs) who generated it (ISO) operates transmission ines • Includes, solar, wind and generation • California Energy Commission (CEC) • Among requirements to be a QF is the production one-stop permits for new power plants of electricity and heat with stipulated efficiency 73 74

Effects of PURPA 1992 Energy Policy Act

• Started the development of a new • Required owners of transmission lines industry: non-utility power producers to accept power from other generators • Merged well with development of for ultimate customers (“wheeling”) stationary gas turbine technology for • Federal Energy Regulatory Commission cogeneration passed enabling regulations in 1996 • California incentives linked to PURPA • California legislature passed made it an international leader for solar restructuring legislation same year and wind electricity (about 85% of world • History of deregulation has been mixed wind and 95% of world solar in 1990)

75 76

http://www.eia.doe.gov/cneaf/electricity/pa ge/restructuring/restructure_elect.html

http://www.cpuc.ca .gov/published/rep April ort/GOV_REPORT 2007 .htm data

http://www.eia.doe.gov/cneaf/electricity/page/restructuring/restructure_elect.html

77 78

ME 483 – Alternative Energy Engineering II 13 Energy storage February 10, 2010

The California Experience The California Experience II

• Law passed in 1996 • Price caps drives electricity sales – 10% decrease in rates mandated until utilities outside of California paid off existing debt – Aluminum smelters made more money by • Open market started March 31, 1998 shutting down and selling electricity • Average wholesale price was $19.73/MWh • Wholesale price escalations not felt by compared to $24/MWh before deregulation LADWP, SCE, and PG&E customers • SDG&E first to raise prices on July 1, 1999 – Companies losing 20 to 30 cents on each kWh they sold – Wholesale price increases to $500/MWh in May 2000 (billed to SDG&E customers) – PG&E bankrupt, SCE close to it

79 80

The California Experience III The California Experience IV

• January 17, 2001 governor directs DWR • What went wrong? to enter into long-term contracts – Manipulation by power suppliers – Contract price was $70/MWh when – Fuel cost increases wholesale spot price was about $300/MWh – Customers shielded from price increases – Later spot prices declined to $35/MWh • When customers had to pay higher prices, electricity use decreased • Price increases due to manipulations by – Lack of new power plants to meet demand companies like Enron and real cost • Capacity increases not provided increases because of price increases in • Current status http://www.ferc.gov/ natural gas industries/electric/indus-act/wec.asp

81 82

83 84

ME 483 – Alternative Energy Engineering II 14 Energy storage February 10, 2010

The Pennsylvania Experience

• Legislation did not require utilities to divest generation facilities and allowed long-term contracts • State is net exporter of electricity http://www.c • Originally considered success story, just puc.ca.gov/p ublished/rep the opposite of California ort/GOV_RE PORT.htm • Subsequent price increases – utilities control large fraction of generation • Prices still lower than before deregulation 85 86

Electric Reliability Reliability Councils Council Regions • Set up to share power in a region • Link producers to produce system reliability – ERCOT – Electric Reliability Council of Texas – FRCC – Florida Reliability Coordinating Council – MRO – Midwest Reliability Organization – NPCC – Northwest Power Coordinating Council http://www.ei – RFC – Reliability First Corporation a.doe.gov/cn – SERC – Southern Electric Reliability Council eaf/electricity/ epa/fig3p2.ht – SPP – Southwest Power Pool ml – WECC – Western Energy Coordinating Council

87 88

http://www.ksg.harv ard.edu/hepg/Paper s/Pope_CA.price.spi California Climate vs. Demand ke.update_12-9- 02.pdf

89 http://www.energy.ca.gov/2005publications/CEC- 90 500-2005-201/CEC-500-2005-201-SF.PDF

ME 483 – Alternative Energy Engineering II 15