An introduction to energy storage technologies

Energy Storage Technologies learnings from other countriesBy Abhinav Bhaskar , Research Associate , The energy and resources institute with inputs from Shreya Agarwal

Contents

Why do we need energy storage ?

Technical and economical savings from energy storage

Types of storage based on application

Different technologies

Criteria for selection of energy storage technology

Economical evaluation of storage technologies

Thermal energy storage-LHES

Renewable energy potential of India

Source : http://mospi.nic.in/mospi_new/upload/Energy_statistics_2016.pdf

Renewable integration in the grid in India

Source : http://mospi.nic.in/mospi_new/upload/Energy_statistics_2016.pdf

Author

Difficulties with renewable integration in the grid

Decentralized electricity production and the introduction of variable , fluctuating source increase the difficulty of stabilizing the power network, mainly due to supply-demand imbalance.

Unpredictable character of renewables requires that network provisioning and usage regulations be established for optimal system operation.

Peak supply and demand of the renewable energy technologies like solar energy do not match and hence create a gap.

Why do we need energy storage ?

Source :http://www.theenergycollective.com/schalk-cloete/259876/intermittent-renewables-and-electricity-markets

THIS FIGURE FROM THE CALIFORNIA GRID OPERATOR SHOWS THE ANTICIPATED EFFECT OF INCREASING SOLAR GENERATION ON THE STATE’S NET LOAD (LOAD MINUS RENEWABLES) IN THE FUTURE. THE AMOUNT OF OTHER ELECTRICITY RESOURCES REQUIRED IN THE MIDDLE OF THE DAY IS REDUCED SIGNIFICANTLY, AND FAST-RAMPING GENERATORS ARE REQUIRED TO COMPENSATE FOR SOLAR BETWEEN 4 AND 8 P.M. (SOURCE: CAISO)

Diurnal variation in solar radiation

www6.cityu.edu.hk/bst/beet/project_page/research%20projects/solar%20utilization/solar%20utilization.htm

What is Energy storage ?

Conversion of excess electricity into a different form of energy which can be reconverted into electricity with minimum losses . This can be done to reduce the gap in supply and demand of electricity. It can be applied to both conventional sources of electricity and renewable energy sources .

It increases the dispatch ability, makes power available on demand and by reducing the gap between supply and demand reduces the need for newer power plants.

Technical and economic advantages of energy storage

Energy transfer

Conventional Energy production : Energy storage compensates for a temporary loss of production, spike in the peak demand and to avoid penalties by fulfilling a commercial agreement of pre-sold energy supply . The power level is comparable to a that stipulated and the quantity of stored energy should be a compromise between the desirable duration of backup power and the potential penalties.

Renewable energy production: Storage of electricity adds value to the supplied current by making it more predictable. Cost of buffer storage should be considered.

Network Savings

Power networks are comprised of many generating units, various levels of transmission and distribution lines and associated stations and sub-stations and a great many consumers with wide ranging power requirements.

End user demand in terms of ratio between peak and average levels often reaches a value of 10. This leads of over dimensioning of transmission equipment which are designed for peak load levels rather than average levels.

Storage helps compensate a local supply for load variations making it possible to operate transmission, sub-transmission and distribution networks with lighter designs.

Kinetic advantage

The flexibility of energy storage systems can help provide instant response to demand and as a consequence, add flexibility to the network in terms of load levelling. Network imbalance can be caused by a temporary production deficit, which could possibly be predicted.

Electricity storage systems

Low power application in isolated areas, essentially to feed transducers and emergency terminals.

Medium power applications in isolated areas (individual electrical systems , town supply)

Network connection application with peak levelling

Power quality control applications

The first two categories are for small scale systems where the energy could be stored as kinetic energy (flywheels) , chemical energy, compressed air, hydrogen (fuel cells) or in super capacitors or super conductors

Categories 3 and 4 are for large scale systems where energy could be stored as gravitational energy, thermal energy , chemical energy or compressed air (coupled with natural gas )

Characteristics of energy storage systems

Storage capacity : Quantity of available energy in the storage systems after charging. Discharge is often incomplete. Wst is the energy stored while Wut is the energy utilized.

Available power : Defines the constitution and size of the motor-generator in the stored energy conversion chain. Expressed as an average value, as well as peak value often used to express the maximum power of charge or discharge.

Power transmission rate: Time needed to extract the stored energy

Efficiency: The ration between the Wut/ Wst . Should be based on the complete cycle to account for the charging, no load and self discharge losses.

Characteristics of Energy storage

Cycling capacity (durability) : Number of times the storage unit can release energy level it was designed for after recharge. Expressed as the maximum number of cycles (N).

Autonomy : The maximum amount of time the system can continuously release energy. Expressed as a= Wut/ Pd ( restorable power / maximum discharge power).

Costs : Investment costs of storage is factored out using the following formula C=C1Wut + C2Pd . Operational costs are proportional to the investment costs , to the tune of 40% of the investment costs

Feasibility and adaptability to the generating source : Highly efficient storage systems need to be closely adapted to the type of application and to the type of production. Needs to be harmonized with the network.

Self-discharge : Portion of stored energy dissipated during non-use time.

Mass and volume density : Refers to the maximum amount of energy stored per unit mass of the storage system.

Environmental and operation safety

Reliability

Different types of energy storage systems

Pumped hydro energy storage (PHES )

Compressed air energy storage ( CAES)

Latent heat thermal energy storage (LHTES)

High temperature thermal energy storage with turbine

Kinetic energy storage system (Flywheels )

Thermal- STES- LHES

Mechanical- Flywheel

- CAES- Pumped hydro

storage

Electro chemical- Batteries

- Flow batteries

Chemical- Hydrogen

Electrical - Super capacitor

- SMES

Pumped Hydro Energy Storage: Overview

The most commercially developed technology.

PHS uses two reservoirs at different heights to store energy

As of 2012, 99% of the global storage is in the form of PHS.1

India’s estimated potential of pumped hydro storage plants is 94GW across 56 sites.2

Round trip efficiency: 70%-85% 3

1. Electric Power Research Institute (EPRI), USA2. http://indiaenergy.gov.in/supply_larhydro.php3. http://greeneconomypost.com/fifteen-grid-scale-energy-storage-solutions-watch-15924.htm#ixzz3zqwwIXOH

Pumped Hydro Energy Storage: Statistics

1. http://indiaenergy.gov.in/supply_larhydro.php2. http://people.duke.edu/~cy42/PHS.pdf3. Assessment of the Role of Energy Storage Technologies for Renewable Energy Deployment in India, Partnership to Advance Clean Energy - Deployment (PACE - D) Technical Assistance

Program, March 2014

StatisticsIndia’s Potential: 90GW across 56

sites1

Total global installed 142 GW across 40

countries 2

Capital cost of electricity is 150-

700$/kWh3

High environmental

Impact High capital investment

required

Occupy large space

Long time for construction

Pumped Hydro Energy Storage: Applications

APPLICATIONS

Load Leveling

Frequency stabilizatio

n

Spinning reserve

Storage media

Reactive power control

Black start

Pumped Hydro Energy Storage: Case Studies

DNVGL has developed Energy Island, North Sea off Dutch coast. It uses an inverse offshore pump accumulation station (IOPAC) on an artificially created island in conjunction with wind energy.1

The Energy Island is about 10 kilometers long and 6 kilometers wide. The water level in the ‘inner lake/ reservoir’ would be 32-40m below that of surrounding North Sea.

Energy Island’s maximum generation capacity is 1,500 MW, depending on the water level.

Annual storage capacity of more than 20 GWh.2

1. https://www.dnvgl.com/services/large-scale-electricity-storage-72722. http://www.windtech-international.com/product-news/news/products-news/kema-collaborates-on-large-scale-offshore-energy-storage-system

Pumped Hydro Energy Storage: Status

Ua:3

22GW

Austria:4 3.5GWFuture

Addition Plan: 5.5GW by

2020

Spain:3 5.4GW Future

addition plan: 720MW

Japan:2

27GW

China:1

24 PHS plants 16.95 GW

Future Target:50GW by 2020

1. http://www.sciencedirect.com/science/article/pii/S13640321120035892. http://www.tsp-data-portal.org/TOP-20-Capacity#tspQvChart3. http://www.store-project.eu/en_GB/current-situation-in-the-target-countries-spain4. http://www.store-project.eu/en_GB/current-situation-in-the-target-countries-austria

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwiczqfTu-PPAhWBvY8KHQiCAlUQFggiMAA&url=http%3A%2F%2Fwww.store-project.eu%2Fdocuments%2Fresults%2Fen_GB%2Freport-summarizing-the-current-status-role-and-costs-of-energy-storage-technologies&usg=AFQjCNFimpnwKCWOJoJi2Ctpfld542AbbQ&sig2=vumKfJOZKWVhCZ84MIPZ9w&cad=rjt

Pumped Hydro Storage Plants in India1

Srisailam Pumped Hydro Storage, 1,670 MW

Sardar Sarovar Pumped Storage Power Station, 1,450 MW

Nagarjuna Sagar Pumped Hydro Station Tail Pond Project700 MW

Bhira Pumped Storage Hydro Plant,150 MW

1. http://indiaesa.info/index.php/resources/india-energy-storage-projects.html

Flywheel Energy Storage System: Overview

Flywheel storage is a mechanical storage technology.

Flywheels are excellent for storing intermittent energy for short time periods.

As most energy is lost due to friction, flywheels are operated in enclosed vacuum spaces to minimize drag.

Image source: http://energystorage.org/energy-storage/technologies/flywheels

Flywheel Energy Storage Systems: Advantages & Disadvantages

Advantages

Low maintenance.

Long life (more than 20-25 years)

Low environmental impact

Excellent load following characteristics

No fuel, water or any resource consumption.

Disadvantages

• Add weight to cars. Especially problematic in racing cars

• High cost as compared to PHS and batteries

• Cost: 1400$/kW1

• Cannot hold power for long durations

1. Assessment of the Role of Energy Storage Technologies for Renewable Energy Deployment in India, Partnership to Advance Clean Energy - Deployment (PACE - D) Technical Assistance Program, March 2014

Flywheel Energy Storage System: Applications

Uninterruptible power supplies1

They consume less space than batteries. Preferred for use in backup systems like UPS for data centers

TransportUsed in hybrid electric vehicle to increase fuel efficiency. Such vehicles are called ‘flybrids’

Grid Energy StorageDue to fast response, low environmental impact, small footprint, these can be used for grid support

Wind TurbinesCan be used to store energy generated by wind turbines during low demand periods

NASA applicationsNASA developed flywheels for application as an energy storage media

These are well suited for applications that require high power, low energy and large number of cycles

1. http://www.datacenterknowledge.com/archives/2007/06/26/flywheels-gain-as-alternative-to-batteries/

Ancillary servicesThey have very fast response and ramp rate: can be used as back up power support/ spinning reserve

Frequency regulation

Flywheel Energy Storage Systems: Case studies

20MW, Stephentown, New York 1

For frequency regulation to NYISO

1. http://beaconpower.com/stephentown-new-york/2. http://www.activepower.com/data-center-case-studies/3. http://www.flybridsystems.com/LMP1test.html

Data center in Sweden using flywheel storage2

Flybrid LMP1 KERS has run for the first time in the Hope Racing LMP1 car. 3

It completed 21 laps of the circuit

Compressed air energy storage

The compression mode of a typical CAES plant is activated at the time when the low demand presents.

The surplus electricity is used to run a chain of compressors to inject the air into a storage reservoir (normally an underground cavern for large-scale CAES), and the stored compressed air is at a high pressure (typically 4.0-8.0 MPa) and the temperature of the surrounding formation.

Such a compression process can use intercoolers and after-coolers to reduce the working temperature of the injected air thus to improve the compression efficiency and minimising thermal stress on the storage volume walls .

When the power generation cannot meet the demand, the expansion mode will be engaged. The stored high pressure compressed air is released from the storage reservoir, heated, and then expanded through a high-pressure turbine which can be a steam turbine or a gas turbine .

Compressor train Expander/generator train

Fuel (e.g. natural gas, distillate)

CAES system

IntercoolersHeat recuperator

PC PG

Air Exhaust

AirStorage

Aquifer,salt cavern,

or hard mine

hS = Hours ofStorage (at PC)

PC = Compressorpower in

PG = Generatorpower out

Source : https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwi6473Er-PPAhXBQI8KHe9VCVoQFgg0MAM&url=https%3A%2F%2Fcmi.princeton.edu%2Fnews%2Fppt%2Fcaes05.ppt&usg=AFQjCNHodvVRn5QSZCCk6XDPx70nGLwsqA&sig2=yXXAc9TTNTofKjgDuzhFLA&cad=rjt

Source : http://www.eera-set.eu/wp-content/uploads/Overview-of-Current-Development-on-Compressed-Air-Energy-Storage_EERA-report-2013.pdf




Compressed air energy storage

Small scale CAES facilities

Small-scale CAES is now attracting the developers’ attention and the associated technologies are emerging. ACompressed Air Battery (CAB) systemisdevelopedby aUK based company -Energetix Group,with a power rating range between 2 kW and a few MW.

Commercial application of small scale CAES System by Energetix group




Useful links

http://www.store-project.eu/

http://energystorage.org/energy-storage/energy-storage-technologies

http://energy.gov/oe/services/technology-development/energy-storage

https://energy.mit.edu/area/power-distribution-energy-storage/

http://indiaesa.info/









Thank you

Abhinav Bhaskar,

Research Associate,

Energy and Environment Technology Development Division

The Energy and Resources Institute (TERI)

Darbari Seth Block, India Habitat Centre

Lodhi Road, New Delhi 110 003, India

Cell: +917042180747

Ph (Direct): +91 11 2468 2100 Ext 2268

Engineering

An introduction to energy storage technologies