Energy Storage Technologies Rich Christie EE 500E October 16, 2008
Energy Policy Seminar � US Energy Policy: Priorities for the Next Administration � Organized by The Forum On Science Ethics and Policy (FOSEP) � When: Thursday, October 16, 2008, 7-9pm � Where: UW Campus, Kane Hall, room 130 � Panelists from science, policy, economy and industry. 10/20/2008 2
Overview � Purpose of Energy Storage � Types of Energy Storage • Pumped Storage Hydro (PSH) • Compressed Air Energy Storage (CAES) • Battery Energy Storage Systems (BESS) • Flywheel Energy Storage Systems (FESS) • Superconducting Magnetic Energy Storage (SMES) • Ultracapacitors 10/20/2008 3
Purpose of Energy Storage � Focus is Large Scale Utility Storage • Many small scale applications: cell phones, substation power supply, hybrid electric vehicles, uninterruptible power supplies � Purpose • Peak shaving • Investment deferral • Generation shaping 10/20/2008 4
time 5 Daily Load Shape Peak Shaving 10/20/2008 P
time 6 Charging Discharging Daily Load Shape Peak Shaving Charging 10/20/2008 P
Peak Shaving � Benefits • Supply cheap off-peak power to on-peak times • Keep base load units on line during off-peak � Issues • Need high price differential to be economic • Round trip efficiency must be high • Enables base load - CO2 release may increase • Daily load shape sets storage and power requirements • Major motivator for existing storage facilities 10/20/2008 7
Investment Deferral � Idea: Optimal utilization of transmission investment Transfer Only a few hours at maximum load % Above 10/20/2008 8
Investment Deferral � Storage allows line to operate closer to average power output Storage Transfer % Above 10/20/2008 9
Investment Deferral � Benefits • More capacity (MWh transferred) from same line • Can defer transmission construction • Transmission losses reduced for same energy transfer • Also provides peak shaving benefits � Issues • How does storage capture value of investment deferral and reduced losses in deregulated market? 10/20/2008 10
Generation Shaping � Wind energy is random, intermittent, over large scales and short times (10 minutes) � Load is slowly varying over 10 minutes � Wind variation must be met by change in controllable output � Generation kept on line and off market to provide response to wind costs money and emissions 10/20/2008 11
12 t t Storage P P Generation Shaping t � Storage a solution P t t P P 10/20/2008
Generation Shaping � Benefits • Smooth, controllable wind farm output • Reduces wind farm transfer requirement � Issues • Adds to wind farm costs, and thus cost of wind power • Regulation currently estimated to add 10% to cost of wind – not enough to pay for storage 10/20/2008 13
Overview � Purpose of Energy Storage � Types of Energy Storage • Pumped Storage Hydro (PSH) • Compressed Air Energy Storage (CAES) • Battery Energy Storage Systems (BESS) • Flywheel Energy Storage Systems (FESS) • Superconducting Magnetic Energy Storage (SMES) • Ultracapacitors 10/20/2008 14
Pumped Storage Hydro � Store energy as gravitational potential energy of water � Need large reservoirs separated by height: 1m 3 H 2 O at 100m = 0.272 kWh � 70-85% round trip efficiency • Electrical losses • Hydraulic losses • Evaporation � Geographically constrained locations 10/20/2008 15
TVA 16 Raccoon Mountain Pumped Storage Plant, Tennessee Pumped Storage Hydro 10/20/2008
Pumped Storage Hydro Ffestiniog Pumped Storage Scheme, Wales, Great Britain http://en.wikipedia.org/wiki/Image:Stwlan.dam.jpg 10/20/2008 17
Pumped Storage Hydro Tianhuangping pumped storage hydroelectric project , China 10/20/2008 18
Pumped Storage Hydro � Machinery • 1890s – separate pumps and generators • 1960s – reversible machines • 1980s – variable pitch impellers • Future – Constant speed generation, variable speed (frequency) pumping 10/20/2008 19
Pumped Storage Hydro Kazunogawa PSH, Japan, 2000. High head, reversible Francis Vane http://www.power-technology.com/projects/kazunogawa/kazunogawa2.html 10/20/2008 20
Pumped Storage Hydro � 37 sites in US, including Grand Coulee Dam � 19.5 GW - 2.5% of base load generation - in US (2000) (EU – 5.5%, about 21 GW) � Capital cost about $600/kW (range 160-2,000) � (2000 is underground generation, open air reservoirs) (energystorage.org) � Scheduling similar to Optimal Power Flow � “Fuel” cost = off peak price / efficiency 10/20/2008 21
Pumped Storage Hydro Innovation � Underground reservoir – old mines � Use of brine as a working fluid 10/20/2008 22
Pumped Storage Hydro Future � Most economic energy storage technology � Geographically constrained � Environmental opposition � Underground may relieve both problems at increased cost � Expect continued expansion 10/20/2008 23
Compressed Air Energy Storage � Concept: • Compress air into a large volume with off- peak electricity • Use air to burn natural gas on-peak • Natural gas burns with improved efficiency • About 2/3rds of output from natural gas, 1/3 from energy storage � Cost: 1991 110 MW plant $591/kW = $889/kW today. (www.electricitystorage.org) 10/20/2008 24
Compressed Air Energy Storage 25 Expander Combustion Turbine Fuel Compressor 10/20/2008 Air
Compressed Air Energy Storage G 26 Expander CAES Storing Storage Compressor M 10/20/2008 Air
Compressed Air Energy Storage CAES Generating Fuel Compressor Expander G M Storage 10/20/2008 27
Compressed Air Energy Storage � CAES: • 0.69kWh off peak electricity + • 1.17 kWh natural gas = • 1.00 kWh on-peak electricity � Combustion Turbine • 1.67 kWh natural gas = • 1.00 kWh electricity 10/20/2008 28
Compressed Air Energy Storage Recuperator heats expanding air with turbine exhaust 10/20/2008 29
Compressed Air Energy Storage http://www.bine.info/pdf/publikation/projekt0507englinternetx.pdf 10/20/2008 30
Compressed Air Energy Storage � Storage is in a salt cavity or abandoned salt mine � Issue is what to do with heat of compression – current CAES dissipate it � Future CAES with adiabatic storage could dispense with natural gas 10/20/2008 31
Compressed Air Energy Storage � Future • Storage in porous aquifer – no cavern required • Used for natural gas storage • Greatly expands potential geologic storage sites • 70-80% of US may be suitable • Not greenhouse gas free (could be) • A number of projects on drawing board 10/20/2008 32
Battery Energy Storage Systems � Lead Acid (Note battery seminar coming) � Flow Batteries � Hydrogen Economy 10/20/2008 33
Battery Energy Storage Systems � Since the 1970s several large scale lead-acid battery systems have been installed in the US � Largest is 20 MW in Puerto Rico (PREPA), used to provide spinning reserve and frequency control � 1/6 to ¼ cheaper over 20 year lifetime than competing resources � Japan said to have 150 MW in BESS 10/20/2008 34
PREPA Battery System � 6000 cells in 6 1000 cell strings � DC 2kV � Two 10 MVA converter-inverters � Capital cost 1,070 $/kW in 1991 (1,400 today) Other BESS costs given as 201-707$/kW by energystorage.org. 10/20/2008 35
Battery Energy Storage Systems 36 10/20/2008
Flow Batteries � Idea is to store reactants externally, pump into reactor to make electricity � As opposed to, e.g. lead acid batteries where reactants and electrolyte are all in one volume � Decouples power rating (size of reactor and pumps) and energy storage (size of tanks) � Just like a fuel cell, but with different reactants. 10/20/2008 37
Flow Batteries � Vanadium Redox Batteries (VRB) leading contender � Developed in Australia, licensed to Sumitomo (Japan) and VRB (Vancouver, BC) � 500 kW installations � Cost 350-600 $/kW (VRB quote) $170/kWh incremental 10/20/2008 38
Flow Batteries http://www.electricitystorage.org/pubs/2001/IEEE_PES_Summer2001/Miyake.pdf 10/20/2008 39
Flow Batteries These compounds are in H 2 SO 4 . http://www.electricitystorage.org/pubs/2001/IEEE_PES_Summer2001/Miyake.pdf 10/20/2008 40
Other Flow Batteries � Regenesys – Polysulfide Bromide • 15 MW and 12 MW plant construction in UK, US (TVA) • US construction halted when environmental review showed leak would result in bromine gas release • Technology now dead 10/20/2008 41
Other Flow Batteries � Sodium-Sulfide (NaS) • Liquid sulfur, liquid sodium • 6 MW 8 hour unit installed for Tokyo Electric • 89% efficient 10/20/2008 42
Other Flow Batteries � Fuel Cells • Require separate electrolyzer • Round trip efficiency low • Hydrogen storage a problem • Vital part of the hydrogen economy (all energy transportation in hydrogen) 10/20/2008 43
Flyw heel Energy Storage � Energy storage as rotational kinetic energy of a spinning mass � Fast response � High self-discharge (rundown) � Steel or composite rotors in vacuum � Magnetic or superconducting levitating bearings 10/20/2008 44
45 Flyw heel Energy Storage 10/20/2008
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