introduction to grid energy storagegeneral layout of a battery energy storage system for the grid....

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INTRODUCTION TO GRID ENERGY STORAGE

Roger LinNEC Energy [email protected] 2017

mailto:[email protected]

Energy Exchange: Connect • Collaborate • Conserve

• Grid Energy Storage Introduction– Why grid energy storage?– What is it and what are the different types?– Where is it used today?

• Understanding Energy Storage– The Fundamental Equation– Battery Based Energy Storage Systems– The Importance of Controls & Integration– SOC vs. DOD– Cycles, Degradation, & Useful Life– What’s the Best Battery?

• Energy Storage Economics– Understanding Energy Storage Costs– Understanding Energy Storage Value

Topics Covered

Why do we need energy storage on the grid?


• Today’s grids require more flexibility to address:– Increased renewable generation

• Compensating for variable energy resources

– Changing load patterns• Generation now distributed to load centers (PV)• EV chargers are shifting consumption patterns

– Aging transmission and distribution network• Infrastructure is aging and needs reinforcement• Upgrades in urban environments can be difficult

• Energy storage in the grid is a powerful tool– Increase flexibility of the system– Improve capacity utilization for generation,

transmission, and distribution infrastructure– Can be placed almost anywhere in the network

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Why Energy Storage for the Grid?

• Adding flexibility, efficiency, and reliability


• In our context, Energy Storage refers to the ability to hold electricity safely, reliably, and economically for future use. – If Energy Storage were cheap and abundant, it would change

the grid dramatically by:• Mediating between variable sources and variable loads.• Decoupling production from consumption.• Reducing price volatility.• Enabling 100% renewable generation.• Making the grid more efficient.• Increasing reliability.

• Today, only about 2.2% of electricity is stored world-wide(1)

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Introduction to Grid Energy Storage

• What is Energy Storage?

Adapted from: Introduction to Bulk Power Systems, B. Kirby, EUCI course, Jun 8-9 2009, Washington DC(1) Source: “Annual Electric Generator Report”, 2011 EIA – Total Capacity 2009; US Energy Information Administration, Form EIA-860, 2011.

Note: We will use the term Energy Storage but discuss specifically Electricity Storage, which is one type of Energy Storage. Other forms of Energy Storage include fossil fuels like oil/natural gas/coal, thermal storage, or power-to-gas, which will not be covered here.


• Energy Storage moves energy through time• With Energy Storage, the grid does not have to instantly balance

generation with consumption• It fundamentally changes system resource adequacy and the system

planning paradigm• It provides System Operators a powerful new tool for system security• It is a game-changer for the electricity grid…

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With Energy Storage, we need to think about the electricity grid in new ways!


• There are many types of energy storage that can be used in the grid– Pumped Hydroelectric Storage (PHS)– Compressed Air Energy Storage (CAES)– Flywheels– Batteries!

• Lead acid• Lithium ion• Sodium beta alumina• Flow batteries

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Other types of Energy Storage:

Fossil FuelsProbably the most abundant and well known form of energy storage –chemical energy storage in the form of oil or gas.

Thermal Energy StorageStoring Heat or Cold in molten salt or ice to either generate electricity or provide useful heat or cooling.

Power-to-Gas (PtG)Using electricity to create hydrogen gas, with possible methanizationstep, and feeding it into the gas grid

Note: These types will not be covered in this training module.

Energy Exchange: Connect • Collaborate • Conserve8

Pumped Hydro Energy Storage

Pumped hydro storage constitutes close to 99% of the worlds energy storage. Due to each facility’s sheer size and scale there are significant hurdles; it takes a lot of money and time to install. They are typically very high energy and can run for tens of hours, and can have a low per unit energy storage cost, but require special geologic conditions to build. There are about 132GW of pumped storage installed around the world as of 2012*.

Europe: 48.3GW

Japan: 26.7GW

Americas: 23.5GW

China: 21.0GW

RoW: 8.0GW

*Source: “International Energy Statistics”, www.eia.gov, Accessed Jan 14 2015.


Compressed Air Energy Storage

Compressed air energy storage, or CAES, uses large reservoirs of high pressure air to store energy. Electricity runs pumps that pressurize the reservoir. When needed, the air is expanded to run generators. CAES requires thermal management since lots of heat is created upon compression and needed back upon expansion due to thermodynamics – sometimes natural gas is burned to provide this heat. Typically high energy capability, and large scale (hundreds of MW).

InstallationsHuntorf, GermanyBuilt 1978321MW, 4 hours

McIntosh Alabama Built 1991110MW, 26 hours

There are only 2 commercially operating bulk CAES systems in the world today!


Flywheel Energy Storage

Notable Vendors

Flywheel systems consist of a rotating wheel, storing kinetic energy. Motors speed up the flywheel to store energy, and a generator slows it down to release energy. Beacon Power was the leader in this area, with two large plants in the US but is now defunct. Flywheels have very high power capability, but very low energy storage capability. Two commercial facilities in operation today:

Stephentown, New York, USABuilt 201120MW, 15 minutes

Hazel, Pennsylvania, USABuilt July 201420MW, 15 minutes

http://temporalpower.com/

http://temporalpower.com/


General layout of a battery energy storage system for the grid

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Battery Energy Storage

Battery Energy Storage Systems need power conversion equipment to connect to the grid and do not make use of any turbine or other generating equipment, unlike PHS or CAES.

While the transformers, power conversion systems, breakers and switches are all fairly common, the differentiating characteristics are primarily in the storage device, and in system design, which ties all the major components to the storage device in a seamless, safe and reliable system.

There are many battery energy storage sites in operation today as both pilot projects and commercial revenue projects… but more on that later.

The next slide will detail the different types of battery technologies.


• Lead Acid• Lithium Ion

– Nickel manganese cobalt (NMC)– Nickelate (LNO)– Nickel cobalt aluminum (NCA)– Iron phosphate (LFP)– Manganese spinel (LMO)– Titanate (anode) (LTO)

• Sodium Beta Alumina– Sodium sulfur– Sodium nickel chloride

• Flow– Vanadium redox– Zinc bromine– Iron chromium

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Battery Energy Storage

• Many types!A word on various battery typesWhile this tutorial will not contain an in-depth comparison of various vendors’ technologies, the generalizations below provide an introduction to each type of battery.

Lead AcidPoor cycle life, power, and energy density, but excellent cost per kWh. However poor deep discharge capabilities limit versatility. ‘Lead carbon’ variants improve upon performance but price also increases. Vendors include Ecoult/East Penn Mfg(using Furukawa technology), Enersys, GS Yuasa, and Axion Power.

Lithium IonMany types; LMO and NMC are most common, generally, but LFP and LTO have taken share in grid applications also. High power, efficiency (up to 90%), versatility (15 min to 4+ hrs) and maturity (used in many applications outside grid), but cost can be high as power to energy ratio decreases. Requires cell balancing electronics. Good to excellent cycle life. Majors include Samsung, LG, Panasonic/Tesla, BYD.

Sodium Beta AluminaMajor vendor is Japanese company NGK with their NAS battery. All operate at high temperatures (~300°C) and require 4-6 hours of energy storage per unit power. Good round trip efficiencies depending on operational profile, up to 85%, but drops if batteries must sit idle – heaters required to prevent ‘freezing’ will consume power constantly. Good to excellent cycle life.

Flow BatteriesWhile many types of flow batteries, low energy density and requirement to pump liquid electrolyte complicates operation for all. Low round trip efficiencies (60-70%). Exceptional cycle life, and good cost for high energy low power configurations. Technology improving but high cost currently. Vendors include Sumitomo, ViZn, Prudent, Primus, Redflow, Gildemeister, and UET.


• The vast majority of energy storage on the grid is in the form of PHS

– About 2.2% of electricity is stored world-wide, mostly in pumped storage(1).

• Only two CAES sites in operation today in revenue service

• Lots of battery energy storage projects today; many in revenue service

– Most in California in the United States– Lithium ion batteries as a category make up the largest

group; sodium beta alumina is the next• Find out more at:

– United States Dept of Energy’s Global Energy Storage Database

– http://www.energystorageexchange.org/– Contains a comprehensive listing of many storage projects

with details on each, along with other resources on energy storage!

– One can submit projects or corrections to projects to the Database administrator for inclusion.

• Some example projects follow…

Where is grid energy storage used today?

(1) Source: “Annual Electric Generator Report”, 2011 EIA – Total Capacity 2009; US Energy Information Administration, Form EIA-860, 2011.

Interior of a battery energy storage container from NEC Energy Solutions showing energy storage racks

http://www.energystorageexchange.org/


11 MW, 4.3 MWh Battery Energy Storage System

Image courtesy of NEC Energy Solutions©2017 NEC Energy Solutions, Inc. – Used with Permission


2 MW, 3.9 MWh Battery Energy Storage System



6 MW, 6 MWh Battery Energy Storage System



4 MW, 2 MWh Battery Energy Storage System



• There are many emerging technologies that have not been proven yet… some of these include:– aqueous sodium ion – liquid metal– zinc air– magnesium ion– lithium air– lithium solid polymer electrolyte– lithium sulfur

• All promise various improvements in cost, cycle life, energy density, and/or safety, but market validation of all these technologies is still underway

The future of energy storage?

Understanding Energy Storage

Adapted from: M. Hardin “Making Cents of Energy Storage”. Energy Storage North America Conference, Oct 2014.


• Power• Energy• Charge• Discharge

• C-Rate• State-of-Charge• Energy Density• Power Density• Depth-of-Discharge• Usable Energy

Some Basic Terminology

• Duration• Power to Energy Ratio• Response Time• Internal Impedance/Resistance

• Duty Cycle• Cycle Life• Calendar (storage) Life• Round Trip Efficiency• Levelized Cost of Energy (LCOE)

While you don’t need to understand all of these terms just yet, some are important



The fundamental equation



Power x Time = Energy




Watts x Hours = Wh




• Power is the RATE of energy delivered– Joule (J) = unit of energy– Watt (W) = Joule per second (J/sec)– 1 Hour (h) = 3600 sec

• Therefore:(J/sec) x (3600 sec) = W x 1 h = Wh




How much Energy is Delivered?

10 MW

5 MW

30 min 60 min 90 min 120 min





10 MW x60 min/(60 min/h)

= 10 MW x 1.0 h= 10 MWh

10 MW

5 MW






10 MW

5 MW






10 MW

5 MW


5 MW x 120 min/(60 min/h)= 5 MW x 2.0 h = 10 MWh




Why the confusion?




• Energy Markets sell in 1 hour increments– 50 MW x 1 h = 50 MWh

• Power (50 MW) = Energy (50 MWh)– Both Power and Energy values are “50”– No difference between MW and MWh– No requirement to understand the difference

Why the confusion?




Q: How long does it take to fill the tank if:– Tank is empty and holds 20 gallons– Pipe allows flow rate of 10 gal/min– The valve controls inlet to 5 gal/min– No water exits

• Amount of water able to be stored depends on size of tank

• Time required to fill/empty the tank dependent on size of pipe

• The rate of water flowing in and out is controlled by the valves

Outlet Pipe Size(Discharging Power)

Inlet Pipe Size (Charging Power)

Valves(Control System)

Size of Tank

(Energy Capacity)

The Water Tank Analogy



Q: How long does it take to fill the tank if:– Tank is empty and holds 20 gallons– Pipe allows flow rate of 10 gal/min– The valve controls inlet to 5 gal/min– No water exits

• Amount of water able to be stored depends on size of tank

• Time required to fill/empty the tank dependent on size of pipe

• The rate of water flowing in and out is controlled by the valves

A: 20 gal/ (5 gal/min) = 4 min

Outlet Pipe Size(Discharging Power)

Inlet Pipe Size (Charging Power)

Valves(Control System)

Size of Tank

(Energy Capacity)




Water Tank Energy Storage System Definition

Water Tank Energy Storage Capacity Total energy (Wh) system can store

Water Level State of Charge (SOC) % of Energy Storage Capacity available

Inlet/Outlet Pipes Power Conversion System (PCS) Converts power between storage and grid

Valves Control System Controls charging and discharging rates

WATER TANKEnergy Storage System

(ESS)

Note: We will be using the term “ESS” as a generic acronym for

any energy storage system. This is similar in letter but different in meaning from NECES’s GSS™

product family.



• Battery-based Energy Storage Systems (ESS)

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Battery & Enclosure

The importance of Controls and System Integration



Battery & Enclosure

Power Conversion System




Power Conversion System

Battery & Enclosure

Control System

Hardware




System Integration & Controls SW



• Key Takeaways

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Energy (Wh) = Power (W) x Time (h)

An ESS requires a storage medium, PCS, control system, and system integration

An ESS is greater than the sum of its parts


• What do these terms refer to?

• Why are they important?

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C-rate, Power:Energy Ratio, and Round Trip Efficiency


• “C-rate” refers to a battery’s discharge rate in amps in relation to its capacity (Ah). It is a way to compare different size batteries on a proportional basis.

– C-rate of “1C” means that if the battery capacity is 100Ah, the discharge rate is 100A.– C-rate of “2C” means that the discharge rate is 200A.– C-rate of “C/4” means that the discharge rate is 25A.

• A related term “Rate Capability” is the ability to discharge faster and still deliver expected capacity. This is important to understand.

– For instance if I discharge a 100Ah battery at 2C, how long will it last?• It depends on the battery type:

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• C-rate

100Ah Battery A discharges at 100A and lasts 1 hr, but at 200A lasts 15 minutes (not 30 minutes as you might expect)! 1C delivers 100Ah

2C delivers only 50Ah

100Ah Battery B discharges at 100A and lasts 1 hr, but at 200A lasts 29 minutes.

1C delivers 100Ah2C delivers 97Ah

Battery B has a higher Rate Capability.


• C-rate key takeaways

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C-rate is a metric to compare energy storage devices of different sizes in a proportional way

Discharging at 2C will not always give you 30 minutes of runtime!

C-rate does not take into account the energy delivered, only the Amp-hours delivered

*Depending on cost per unit power and energy, of course!


• What is Power:Energy ratio?– Essentially a measure of discharge power (W) compared to energy storage capacity

(Wh); a rating of the maximum discharge power you can achieve while receiving substantially all of the energy stored in the device.

– However unlike C-Rate, it takes into account the voltage at which each amp is delivered, and thus the amount of useful work that can be performed and is a better metric for energy storage.

• Why is this important?– Say you need a 1MW energy storage system. – Option A: Lithium ion with 1MW of power capability, and 1MWh of energy storage

capability. • It cannot do 1MW with less storage because the underlying device is not capable of discharging

at that power level. It simply does not have the “body weight” to generate that much power.– Option B: Lithium ion with 1MW of power capability, and 250kWh of energy storage

capability.• It can do 1MW with only 250kWh because it has a higher Power:Energy ratio. It is stronger per

unit “body weight”. It can also be said that it has a higher Rate Capability.– Let’s say Option A is $600/kWh and Option B is $2,000/kWh. Which one is better?

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• Power:Energy ratio


– Do the math:• Option A: $600/kWh x 1,000kWh = $600,000• Option B: $2,000/kWh x 250kWh = $500,000

– Option B is better even though the unit price is more than 3x of Option A!

• Now let’s say you again need a 1MW energy storage system.– But this time, you need at least 1 hour of energy storage (1,000kWh)!

• Which one is better?– Do the math:

• Option A: $600/kWh x 1,000kWh = $600,000• Option B: $2,000/kWh x 1,000kWh = $2,000,000

– Option A is better by far since the application requires more storage capacity.

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• Power:Energy ratio


0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 30 60 90 120 150 180 210 240 270 300 330 360

$/kW

Duration (minutes)

Simple cost per kW (Power) vs Duration (Energy)• Some more economic for power applications, some for energy

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Energy Storage Costs Vary By Technology

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 30 60 90 120 150 180 210 240 270 300 330 360

$/kW

Duration (minutes)

Modified Cost per kW (Power) vs Duration (Energy)

Green and blue curves are both the same capability, same C-rate, but one is more expensive than the other. Always choose the blue curve? Maybe not! Depends on performance over time. Consider… levelized cost of STORAGE.

Energy storage costs are coming down, but they vary in capability. Some are good for power, others for energy. Choose the right tool for the job!


• Power:Energy ratio key takeaways

46


Power:Energy Ratio is important to match applications with the best battery technology

A high power application would benefit from a high Power:Energy ratio battery*

A high energy application would benefit from a low Power:Energy ratio battery*



• Round Trip Efficiency (RTE) refers to the amount of energy (Wh) that can be returned after being stored.

• It is never 100% - there is always some loss in the storage of energy.– Storing and returning energy results in some of it being lost in heat or side

reactions– Power to Energy Ratio and Rate Capability are good indicators of the RTE

capability• Lower internal resistance means higher RTE; less wasted energy

– Operating at higher power and higher C-rates will lower RTE and vice versa; RTE can fluctuate in the same system depending on operating parameters.

• RTE% impacts the operational cost of an energy storage device, because for every Wh you put in, you only get a fraction of it back out!– This means that, on a net basis, all energy storage devices consume energy.– This energy consumption can be considered a “storage fee”.– Lower RTE means you pay higher storage fees!

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• Round Trip Efficiency


• RTE key takeaways

48


Round Trip Efficiency is never 100%

You want higher RTE’s since it will lower your “storage fees”

Energy storage type, system design, and operating parameters can impact RTE



SOC vs. DOD

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• What’s the difference?

• Who uses which metric and why?

• Which is more important for an ESS?

• Why should you care?



SOC% = 100% - DOD%

25% DOD 75% SOC

0% 25% 50% 75% 100%

• Depth of Discharge (DOD) = % of energy removed

• State of Charge (SOC) = % of energy remaining

SOC vs. DOD



75% DOD 25% SOC

0% 25% 50% 75% 100%

SOC% = 100% - DOD%

• Depth of Discharge (DOD) = “air in the tank”

• State of Charge (SOC) = “water in the tank”

SOC vs. DOD


SOC vs. DOD: Key Takeaways

52


SOC% = 100% - DOD%

SOC measures % energy remainingDOD measures % energy removed

Battery Suppliers use DOD, but SOC more important in understanding ESS


• Cycles, Degradation, & Useful Life

53


So… how long will the batteries last?



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100%

95%

90%

80%

85%

75%

500 1000 1500 2000 2500 3000 3500 4000 4500 55005000 6000

# Cycles @ 80% DOD

% R

emai

ning

Cap

acity

# Cycles vs. Capacity Degradation

EOL @ 80% Remaining Capacity

±1C at 25°C

What does this mean?



55


• Cycle – when a battery is discharged and recharged from an initial SOC and back

• Degradation – the loss of battery energy storage capacity over time which reduces the available % remaining capacity (also known as capacity “fade”)

• End of Life (EOL) – the point at which a battery degrades enough to reach a % remaining capacity which the manufacture defines as the end of its useful life



56


• “Battery Life” depends on a number of factors including but not limited to:

• Total nameplate energy capacity• Operating temperature • Power required per battery • Total energy charged + discharged during use• Operating SOC range • % Remaining capacity at End of Life



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• Most of the technical specifications required are provided• But we still must convert life cycles to energy throughput

100%

95%

90%

80%

85%

75%

500 1000 1500 2000 2500 3000 3500 4000 4500 55005000 6000

# Cycles @ 80% DOD

% R

emai

ning

Cap

acity



±1C at 25°C


• What if car warranties were based on 1,000 road trips of 18 miles each way?

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Cycles, Degradation, & Useful Life



• Total miles = 1,000 x 18mi/trip x 2 trips = 36,000mi

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• Total miles = 1,000 x 18mi/trip x 2 trips = 36,000mi

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# Cycles kWh/Cycle Total Energy Throughput



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Assuming an ESS has 1 MWh nameplate energy, lifetime energy throughput can be calculated as:6,000 cycles x 80% DOD x 1 MWh x 2 trips/cycleThroughput = 6,000 x 0.8 x 1 x 2 = 9,600 MWh

100%

95%

90%

80%

85%

75%

500 1000 1500 2000 2500 3000 3500 4000 4500 55005000 6000

# Cycles @ 80% DOD

% R

emai

ning

Cap

acity



±1C at 25°C For example only



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How many miles per year do you need to drive the car?

How many MWh/year are required to be charged and discharged in the energy storage application?

100%

95%

90%

80%

85%

75%

500 1000 1500 2000 2500 3000 3500 4000 4500 55005000 6000

# Cycles @ 80% DOD

% R

emai

ning

Cap

acity






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Throughput = 6,000 x 80% x 1.0 MWh x 2 = 9,600 MWh

Assuming application requires 960 MWh/year

80% nameplate capacity remaining in year 10(high level estimate)

100%

95%

90%

80%

85%

75%

500 1000 1500 2000 2500 3000 3500 4000 4500 55005000 6000

# Cycles @ 80% DOD

% R

emai

ning

Cap

acity






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Battery life depends on a number of factors

The impact of most factors can be minimized if the ESS is properly sized and controlled

Use cycle life data to calculate lifetime energy throughput & compare to application needs


What Can Energy Storage Do?

• Lots of possibilities!


Contact me for more information

Thank you!

Roger LinSenior Director, Product MarketingNEC Energy Solutions, Inc.155 Flanders RdWestborough, MA 01581+1 (508) [email protected]

mailto:[email protected]

introduction to grid energy storagegeneral layout of a battery energy storage system for the grid....

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