Energy Storage Alternatives for Household and Utility-scale Applications

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Energy Storage Alternatives for Household and Utility-scale Applications Marc Secanell Energy Systems Design Laboratory, http://www.

1 Energy Storage Alternatives for Household and Utility-scale Applications Marc Secanell Energy Systems Design Laboratory, Department of Mechanical Engineering, University of Alberta, Edmonton, Canada Solar Energy Society February 25, 2015

2 Overview 2 About the presenter Introduction Why do we need energy storage? How much energy storage do we need? Choosing among options Small scale/residential energy storage Electrochemical batteries Flywheels Large scale/grid scale energy storage Pumped-hydro Synthetic fuels, e.g., solar hydrogen Conclusions

3 About the presenter 3 Experience 2013-Present, Associate Professor, University of Alberta, Department of Mechanical Engineering o Teaching: Energy conversion, Thermo-fluid systems design, Electrochemical systems o Research: Director of Energy systems design laboratory , Assistant Professor, University of Alberta, Department of Mechanical Engineering , Assistant Research Officer, National Research Council, Institute for Fuel Cell Innovation Education Ph.D. Mechanical Engineering, University of Victoria, Canada, 2008 M.A.Sc. Mechanical Engineering, University of Victoria, Canada, 2004 B.Eng., Universitat Politècnica de Catalunya, Barcelona, 2002

Energy systems design laboratory: Overview 4 Mandate: "To design energy systems that can meet society s needs while minimizing their cost, environmental and socio-political impact.

4 Energy systems design laboratory: Overview 4 Mandate: "To design energy systems that can meet society s needs while minimizing their cost, environmental and socio-political impact." 10 researchers 1 Post-doctoral fellow 3 Ph.D. students 5 M.Sc. students 1 undergraduate students Open for collaboration with local industry Website:

5 Energy systems design laboratory: Expertise 5 Computational Design and Optimization of Energy Systems Polymer electrolyte fuel cell design Flywheel design Computational Analysis of Energy Systems Developing energy system models and simulation software, e.g., openfcst Clean hydrogen production processes Experimental Testing of Energy Systems Fuel cell fabrication and testing Hydrogen electrolyzer fabrication and testing Flywheel fabrication an testing

6 Overview 6 About the presenter Introduction Why do we need energy storage? How much energy storage do we need? Choosing among options Small scale/residential energy storage Electrochemical batteries Flywheels Large scale/grid scale energy storage Pumped-hydro Synthetic fuels, e.g., solar hydrogen Conclusions

7 Why do we need energy storage? 7 Our current energy infrastructure can be simplified to:

8 Why do we need energy storage? 8 Energy supply: ***Includes geothermal, solar, wind, heat, etc. Source: International Energy Agency, Key World Energy 2014.

9 Why do we need energy storage? 9 Our energy storage are our coal, oil and natural gas reserves Heating: Natural gas pipeline Transportation: Gas stations, refineries Electricity: Electrical grid The electrical grid is the largest just-in-time supply system in the world Electricity demand matched by turning on/shutting down power plants o Power plants with largest inertia, e.g., nuclear and coal, are not usually shut down Current storage in U.S. can provide 2.3% of the grid power capacity, i.e GW Energy vs. power Energy = Joules or kwh = how much water is in the bathtub Power = Energy / Time = MW = how fast is the water draining

thermal for DHW Global goal to increase renewable energy production worldwide Reduce GHG

10 Why do we need energy storage? Increased use of renewable energy in households Solar PV to produce electricity Solar thermal for DHW Global goal to increase renewable energy production worldwide Reduce GHG emissions Distributed and large-scale solar PV, wind farms, 10 Source: Mill Creek NetZero greenedmonton.ca Source: International Energy Agency, Key World Energy 2014.

11 Why do we need energy storage? 11 Renewable energy resources are intermittent They cannot be switched on/off on demand o Reduce our current ability to match supply and demand Resource is intermittent and hard to predict High energy demand hours/months do not match with high energy production hours o Solar: Highest production hours from solar would be 10-16h but highest demand hours would be 18-22h Source: Fraunhofer Institute for Solar energy systems (ISE) Electricity production from solar and wind in Germany in 2011

12 Power produced (MW) Why do we need energy storage? 12 Wind production in Alberta, first week of January 2010 Data from Alberta Electric System Operator Variability leads to curtailment At very high production times, AESO cannot accept all wind power due to oversupply and transmission limitations (2-10% not used) 600 Wind power production from Jan 01 to 07, 2010 (MW) Time in minutes

13 Energy storage options: All-electric 13 Option 1: All-electric energy storage/transportation

14 Energy storage options: All-at-once 14 Option 2: Electric and fuel energy storage system e -

15 Choosing among options 15 Questions you should ask (yourself) when selecting an energy storage option How much energy do we want to store? o Specific energy and energy density (in kwh/kg or kwh/m 3 ) o Discharge depth limit How much power do you need the system to provide? o Specific power and power density (in W/kg and W/m 3 ) How much of the energy stored do you expect to recover, and after how long? o Turnover efficiency o Losses during charge, no-load (self-discharge) and discharge How long do you want your system to last? o Durability (cycling capacity) What type of energy do we want to store? What do we want to use the stored energy for? How much are you willing to pay up-front (capital cost)? Overall?

16 How much do we want to store? 16 Household storage: In 2011, the average Canadian household consumed 105 GJ/yr o ~ 40% (actually 38%) electricity o 45% natural gas o Rest wood, oil and propane NG used for heating Electricity used for heating (in some provinces), appliances, etc. If we want to store only necessary electrical power we would need: 32 kwh/day Source: Statistics Canada, Households and the Environment: Energy Use, 2011

17 Power produced (MW) How much do we want to store? 17 Grid level storage Wind power in Alberta Total capacity: 1,434 MW (9% total capacity) Provided 5.1% of the energy in Alberta In Jan 01-07, 2010, average power MW, peak 500 MW Curtailment of wind power generation due to oversupply and transmission constraints Wind power production from Jan 01 to 07, 2010 (MW) ~20 TJ = 5,555,556 kwh = 5.56 GWh Time in minutes

18 How much do we want to store? 18 If I produce electricity using renewable energy, then I can be energy independent and zero-emissions Not so quickly What about transportation, heating and industrial applications? Source: Statistics Canada, Households and the Environment: Energy Use, 2011

19 Choosing among options 19 The answer to these questions leads to different energy storage options Source: Fraunhofer institute

20 Choosing among options 20 Cost is different per unit energy and per unit power Source: H. Ibrahim, Renewable and Sustainable Energy Reviews, 12: , 2008

21 Choosing among options 21 Capital cost are not the full story Cost also depends on the durability of your technology Source: H. Ibrahim, Renewable and Sustainable Energy Reviews, 12: , 2008

22 Energy storage options 22 Electricity must be stored in some other energy form, e.g., chemical, kinetic, potential and thermal In this presentation we will focus on one of the most mature and one of the most risky for residential and grid-scale storage Flywheel energy storage (residential scale) Chemical energy storage (residential and grid-scale) o Batteries o Hydrogen Pumped hydro (grid scale) Many other available Compressed air energy storage (grid scale) Thermal energy storage (TES) (grid and residential scale) Ultra-capacitors (residential scale)

23 Overview 23 About the presenter Introduction Why do we need energy storage? How much energy storage do we need? Choosing among options Small scale/residential energy storage Electrochemical batteries Flywheels Large scale/grid scale energy storage Pumped-hydro Synthetic fuels, e.g., solar hydrogen Conclusions

Electrochemical batteries: How they work 24 Energy is stored in the form of chemicals inside the battery During discharging the positive electrode is reduced and the negative electrode oxidized

24 Electrochemical batteries: How they work 24 Energy is stored in the form of chemicals inside the battery During discharging the positive electrode is reduced and the negative electrode oxidized During charging the positive electrode is oxidized and the negative electrode is reduced Example: Lead-acid battery Negative electrode (discharge): Pb s + SO 2 4 PbSO 4(s) + 2e Positve electrode (discharge): PbO 2 (s) + 4H + + SO e PbSO 4(s) + 2H 2 O Source:

25 Electrochemical batteries: Energy storage capacity Different types of batteries depending on Positive and negative electrode materials Electrolyte: Medium transporting ions, e.g., H +, SO 4 2- Most common rechargeable (secondary) batteries: 25 Source: Linden and Reddy, Linden s Handbook of Batteries, 4 th ed., 2011

26 Electrochemical batteries: Energy storage capacity Specific energy numbers based on optimal discharge conditions Performance might be significantly different due to type of discharge o Rate of discharge o Continuous or intermittent temperature of the battery during discharge service life (number of cycles) 26 Source: Linden and Reddy, Linden s Handbook of Batteries, 4 th ed., 2011

27 Electrochemical batteries: Ratings 27 Decision matrix based on all factors: Source: Linden and Reddy, Linden s Handbook of Batteries, 4 th ed., 2011

28 Electrochemical batteries: Advantages and disadvantages Advantages and disadvantages change with type of battery Advantages Moderate capital cost per unit energy (specially for lead-acid) Easy to extend due to modular installation Disadvantages Poor cost per cycle (specially for lead-acid) Low energy density (only applicable to small scale applications) Safety as some use dangerous materials and some can ignite (e.g., Li-ion) For kwh scale, Lead-acid batteries remain the best compromise between cost and performance Lithium-ion has better performance and durability but is more expensive Austin Utilities Energy Storage Pilot o Four lead-acid 9.2 kw/23.6 kwh Silent Power storage units installed in municipal buildings for peak demand management. 28

speed rotor: High-strength composite materials Source: M. Krack, M.

29 Flywheels: How they work 29 Electrical energy is stored in the form of kinetic energy in a high speed rotor Rotor types: Low speed rotor: Steel rotor High speed rotor: High-strength composite materials Source: M. Krack, M. Secanell and P. Mertiny, Rotor Design for High-Speed Energy Storage Flywheel Systems, InTech, 2012

30 Flywheels: How they work 30 Decoupling of power and energy storage Power rating controlled by motor/generator Energy storage controlled by rotor size and speed Energy storage is given by: E = 1 2 I zzω 2 [J] where ω is the rotational speed in rad/s and I zz is the moment of inertia, i.e. I zz = 1 2 πρh(r o 4 r i 4 ) where ρ is the density of the material, and h and r are the rotor height and radius More info see: M. Krack, M. Secanell and P. Mertiny, Rotor Design for High-Speed Energy Storage Flywheel Systems, InTech, 2012

31 Flywheels: Energy storage capacity 31 Flywheel speed, and rotor size and weight control the maximum energy storage A flywheel of 45 cm radius and 20 cm height rotating at 30,000 rpm stores 35.2 kwh This is more than the 32 kwh/day needed to power your house for one day Source: M. Krack, M. Secanell and P. Mertiny, RotorDesign for High-SpeedEnergy StorageFlywheel Systems, InTech, 2012

32 Flywheels: Advantages and disadvantages 32 Advantages: Cheap, non-toxic raw materials Minimal cycling degradation Energy and power requirements are decoupled High volumetric power density o 310 Wh/kg Low capital cost per cycle Disadvantages: Rapid self-discharge. It can be minimized by: o Operating under vacuum o Using magnetic bearings o Physically decoupling the motor during operation Safety o Robust enclosure necessary High capital cost per unit energy

33 Flywheels: Commercial examples 33 Temporal Power, Canada In the grid: Hydro One uses flywheels for frequency regulation on a feeder that is connected to two 10-megawatt wind farms in southwest Ontario VYCON Tech. REGEN kinetic energy storage system at the Los Angeles County Metropolitan Transportation Authority (Metro) saves nearly 20% in energy consumption Source: Source:

34 Flywheel prototype (UAlberta) 34 Proof of concept (University of Alberta) Dual rotor with 5cm height and 10-17cm and 17-20cm radii Magnetic and low-friction ceramic bearings Operated at 0.13 bar pressure A 5.5 kw motor type Kontronik PYRO Up to 12,000 rpm thus far Collaboration with Dr. Pierre Mertiny

35 Flywheel prototype (UAlberta) 35 Energy storage thus far 31 Wh Theoretical 138 Wh (at 30,000 rpm)

36 Overview 36 About the presenter Introduction Why do we need energy storage? How much energy storage do we need? Choosing among options Small scale/residential energy storage Electrochemical batteries Flywheels Large scale/grid scale energy storage Pumped-hydro Synthetic fuels, e.g., solar hydrogen Conclusions

Pumped-hydro storage 37 During periods of low electricity demand, water is pumped from a low to a high reservoir. When demand increases, the flow is reversed.

37 Pumped-hydro storage 37 During periods of low electricity demand, water is pumped from a low to a high reservoir. When demand increases, the flow is reversed. In US, 95% of current energy storage provided by pumped hydro Racoon Mountain Pumped-Storage Plant Source: Estany Gento Sallente water pumping station (Catalonia) Capacity: 6.5e6 m 3

38 Pumped-hydro storage: How it works 38 Parameters influencing the plant are: Reservoir height Flow rate (reservoir available volume) Pump/turbine/generator efficiencies o Overall 70-80% possible Mathematically, E T = η T η g ρgh T V P T = η T η g ρgh T Q T E p = η p η m ρgh p V P p = η p η m ρgh p Q p where V is the available volume, Q p and Q T are the flowrates, in m 3 /s and η p, η m, η T and η g are the pump, motor, turbine and generator efficiencies

Pumped-hydro storage: Example 39 Estany Gento Sallente (Catalonia) Capacity lower reservoir 6.5e6 m 3 Change in height: 370 m Storage capacity (assuming η=80%) o 18.86 TJ (2-5 TJ more likely) vs.

39 Pumped-hydro storage: Example 39 Estany Gento Sallente (Catalonia) Capacity lower reservoir 6.5e6 m 3 Change in height: 370 m Storage capacity (assuming η=80%) o TJ (2-5 TJ more likely) vs. 20 TJ for Alberta wind energy Assuming 80% efficiency, a height of 100m and a depth of 50m, the reservoir would need to cover a square of 1 km by 1 km Grid scale storage can be accomplished but requires large storage facilities Estany Gento Sallente water pumping station (Catalonia)

Negligible cycling degradation Lowest capital cost per unit power and low capital cost per unit energy

40 Pumped-hydro storage: Advantages and disadvantages Advantages Large energy storage and power potential o 1 TJ = 277,777 kwh High overall efficiency (70-80%) Small self-discharge (due to evaporation) Negligible cycling degradation Lowest capital cost per unit power and low capital cost per unit energy (but a lot of energy ) Disadvantages Requires a mountainous topology Requires large land area (km 2 scale) 40

Solar Hydrogen: Overview 41 Store energy as compressed hydrogen in underground reservoir Electrochemical or photo-electrochemical converter used to split water

41 Solar Hydrogen: Overview 41 Store energy as compressed hydrogen in underground reservoir Electrochemical or photo-electrochemical converter used to split water into hydrogen and oxygen and stored Hydrogen converted to electriciy when required using a fuel cell Source: Shell Corp., HyUnder Project Launch, November 2012

Solar Hydrogen Production: Using electricity Electricity is used to split water in the anode producing protons and oxygen At the cathode protons are combined to produce hydrogen

42 Solar Hydrogen Production: Using electricity Electricity is used to split water in the anode producing protons and oxygen At the cathode protons are combined to produce hydrogen Hydrogen can be produced at high pressure for storage or injection into the natural gas pipeline 42 Anode: 2H 2 O O 2 + 4H + + 4e Cathode: 4H + + 4e 2H 2 Source:

43 Solar Hydrogen Production: Using electricity 43 Goal: 80-85% (HHV) efficiencies with hydrogen at pressures of 300bar. Examples (Study performed in 2004): Manufacture Model Stuart (alkaline) Teledyne (alkaline) Proton (PEM) Norsk (alkaline) Avalance (alkaline) System Energy [kwh/kg] Hydrogen Prod. [kg/hr] Conversion efficiency Energy efficiency Hydrogen pressure [atm] Up to 680

Solar Hydrogen Production: Direct conversion 44 A photo-voltaic cell in immersed in water The PV cell provides the potential difference necessary to drive the water oxidation reaction 12.

44 Solar Hydrogen Production: Direct conversion 44 A photo-voltaic cell in immersed in water The PV cell provides the potential difference necessary to drive the water oxidation reaction 12.4% solar-to-fuel efficiency demonstrated in % solar-to-fuel efficiency using non-precious materials demonstrated in Anode: 2H 2 O O 2 + 4H + + 4e Cathode: 4H + + 4e 2H 2 Source: K. Maeda, J. Photochemistry and Photobiology C: Photochemistry Reviews. 12, 237 (2011).

45 Hydrogen energy content 45 Specific energy and energy density 0.54 MJ/kg (Li-ion) vs MJ/kg 1.44 MJ/L (Li-ion) vs MJ/L (1 atm) or 1 MJ/L (100 bar) Large volume reservoir and compression required Compression 5-15% loss Hydrogen to carbon ratio Hydrogen (H 2 ) Gasoline (C 8 H 18 ) 1:0 2.25:1 Freezing point [ºC] Boiling point [ºC] Net enthalpy of combustion NTP * [MJ/kg] Heat of vaporization [kj/kg] (LHV) (LHV) NTP [kg/m 3 ] Liquid density [kg/m 3 ]

Hydrogen storage underground: Examples 46 Previous underground storage of hydrogen and synthetic gas (H 2 -CO) mixes In England, at Teesside, Yorkshire, the British company ICI has stored 1 million

46 Hydrogen storage underground: Examples 46 Previous underground storage of hydrogen and synthetic gas (H 2 -CO) mixes In England, at Teesside, Yorkshire, the British company ICI has stored 1 million Nm 3 of nearly pure hydrogen (95% of H 2 and 3-4% of CO 2 ) in three salt caverns at about 400 m in depth for a number of years. In France, the gas company Gaz de France has stored a synthetic "town gas" 50-60% hydrogen in an aquifer of 330 million Nm 3 capacity between 1956 and No gas losses or safety problems have been reported In Germany, at Kiel, a 62% H 2 town gas was stored in a salt cavern of m 3 at bar In 2007, Praxair opened an underground cavern hydrogen storage facility in Texas Sources:

47 Solar hydrogen utilization 47 Consumed as a fuel for heat, chemical products or electricity For electricity, in a fuel cell for higher efficiency: 40-60% H 2H 2 2 e O 2 4H 4e 2H 2 O H 2 O 2 e - H + H 2 O e -

Disadvantages Cost (85% is the cost of the electrolyzer unit) Low overall efficiency o If heat: 60% o If electricity:

48 Hydrogen storage: Advantages and disadvantages Advantages Large energy storage and power production potential Negligible self-discharge Hydrogen can be used also for other application such as heating and transportation Disadvantages Cost (85% is the cost of the electrolyzer unit) Low overall efficiency o If heat: 60% o If electricity: 25-40% Source: Source Cell-Bus/BCTransit_fuel_cell_bus.jpg

energy storage (1/2 day) Li-ion battery Cost: $38,500 Toyota Mirai 60 kwh energy storage (2 days) 5kg of H 2 in 700 bar compressed tank

49 Hydrogen storage: A possible road to mobile energy storage In Canada, 30% of energy consumption is due to the transportation sector Dependant exclusively on fossil fuels Hydrogen fuel cells are one of the main alternatives for zero-emission vehicles Chevy Volt 16 kwh energy storage (1/2 day) Li-ion battery Cost: $38,500 Toyota Mirai 60 kwh energy storage (2 days) 5kg of H 2 in 700 bar compressed tank Cost: $57,500 Grid storage: To store 20 TJ you need 347,222 Chevy Volts Source: 49 Source:

50 Hydrogen storage at UAlberta 50 Fabricating and testing Fuel cells Electrolyzers Cost main drawback of the technology Cost due to expensive catalyst materials Research on Low catalyst loading electrodes Mathematical modelling and design of fuel cells and electrolyzers Improving fuel cells for low temperature operation 1.7 μm

51 Conclusions 51 Currently, fossil fuels are our energy storage To increase the use of renewable energy sources, more energy storage is needed It is estimated that without storage only 20% of energy can come from renewable sources Many energy storage options available Residential scale o 32 kwh/day required o Available options: Batteries, flow batteries and flywheels Grid scale o Several GWh required (20 TJ) o Available options: Pumped-hydro, compressed air, flow batteries and hydrogen

52 Acknowledgement 52

53 Thank You

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