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An introduction to energy storage technologies


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Collected information on energy storage technologies .

Published in: Engineering
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An introduction to energy storage technologies

  1. 1. Energy Storage Technologies learnings from other countries By Abhinav Bhaskar , Research Associate , The energy and resources institute with inputs from Shreya Agarwal
  2. 2. 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
  3. 3. Renewable energy potential of India Source :
  4. 4. Renewable integration in the grid in India Source :
  5. 5. 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.
  6. 6. Why do we need energy storage ? Source :
  8. 8. Diurnal variation in solar radiation
  9. 9. 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.
  10. 10. 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.
  11. 11. 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.
  12. 12.  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.
  13. 13. 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 )
  14. 14. 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.
  15. 15. 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
  16. 16.  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
  17. 17. 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 )
  18. 18. Thermal - STES - LHES Mechanical - Flywheel - CAES - Pumped hydro storage Electro chemical - Batteries - Flow batteries Chemical - Hydrogen Electrical - Super capacitor - SMES
  19. 19. 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), USA 2. 3.
  20. 20. Pumped Hydro Energy Storage: Statistics 1. 2. 3. 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 Statistics India’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
  21. 21. Pumped Hydro Energy Storage: Applications APPLICATIONS Load Leveling Frequency stabilizatio n Spinning reserve Storage media Reactive power control Black start
  22. 22. 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. 2.
  23. 23. Pumped Hydro Energy Storage: Status Ua:3 22GW Austria:4 3.5GW Future 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. 2. 3. 4.
  24. 24. status-role-and-costs-of-energy-storage-technologies&usg=AFQjCNFimpnwKCWOJoJi2Ctpfld542AbbQ&sig2=vumKfJOZKWVhCZ84MIPZ9w&cad=rjt
  25. 25. 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 Project 700 MW Bhira Pumped Storage Hydro Plant,150 MW 1.
  26. 26. 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:
  27. 27. 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
  28. 28. 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 Transport Used in hybrid electric vehicle to increase fuel efficiency. Such vehicles are called ‘flybrids’ Grid Energy Storage Due to fast response, low environmental impact, small footprint, these can be used for grid support Wind Turbines Can be used to store energy generated by wind turbines during low demand periods NASA applications NASA 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. Ancillary services They have very fast response and ramp rate: can be used as back up power support/ spinning reserve Frequency regulation
  29. 29. Flywheel Energy Storage Systems: Case studies 20MW, Stephentown, New York 1 For frequency regulation to NYISO 1. 2. 3. 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
  30. 30. 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 .
  31. 31. Compressor train Expander/generator train Fuel (e.g. natural gas, distillate) CAES system Intercoolers Heat recuperator PC PG Air Exhaust Air Storage Aquifer, salt cavern, or hard mine hS = Hours of Storage (at PC) PC = Compressor power in PG = Generator power out Source : PPAhXBQI8KHe9VCVoQFgg0MAM&
  32. 32. Source :
  33. 33. Source :
  34. 34. Source :
  35. 35. Source :
  36. 36. Compressed air energy storage
  37. 37. 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.
  38. 38. Commercial application of small scale CAES System by Energetix group
  39. 39. status-role-and-costs-of-energy-storage-technologies&usg=AFQjCNFimpnwKCWOJoJi2Ctpfld542AbbQ&sig2=vumKfJOZKWVhCZ84MIPZ9w&cad=rjt
  40. 40. role-and-costs-of-energy-storage-technologies&usg=AFQjCNFimpnwKCWOJoJi2Ctpfld542AbbQ&sig2=vumKfJOZKWVhCZ84MIPZ9w&cad=rjt
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  42. 42. Useful links     
  43. 43. 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 