Physical structure and characteristics of energy storage systems
- 1. Physical structure and characteristics of energy storage systems Presented by Prof. (Dr.) P. K. Rout, ITER, SOA Deemed to be University & Mr. P. Bhowmik, CSIR, India
- 2. Introduction • Grid energy storage is a collection of methods used to store electrical energy within an electrical grid. • Electrical energy is stored during times when production (especially from renewable energy sources) exceeds consumption, and returned to the grid when production falls bellow consumption.
- 4. Different energy storage system categories
- 5. Benefits of Storage and managing peak load (1/2) • Electricity production need not be drastically scaled up and down to meet momentary consumption. • From the combination of generators and storage facilities, generation can be maintained at more constant level. • Fuel based power plants (i.e. coal, oil, gas, nuclear) can be more efficiently and easily operated at constant production level. • Peak generation or transmission capacity can be reduced.
- 6. Benefits of Storage and managing peak load (2/2) • More stable pricing can be offered to the bulk power consumers. • At any emergency condition vital needs can be reliably powered even at no generation condition (renewable sources concerned). • The French consulting firm ‘Yole Development’ figures this ‘stationary storage’ market could be $ 13.5 billion opportunity by 2023, compared with less than $ 1 billion in 2015
- 7. Forms of Storage • Compressed air energy storage (CAES) • Liquid air energy storage (LAES) • Super conducting magnetic energy storage (SMES) • Super capacitor energy storage (SCES) • Flywheel energy storage (FES) • Power-to-Gas (P2G) • Pumped-storage hydroelectricity (PSH) • Plug-in hybrid electric vehicles • Thermal storage
- 8. Compressed air energy storage (CAES) • Off-peak energy is used to compress air and can be released to meet peak load demand. • If the heat generated during compression can be stored and used during expansion, the efficiency of storage improves considerably. • There are three ways in which a CAES can deal with the heat. 1. Adiabatic 2. Diabetic 3. Isothermal
- 9. A schematic
- 10. Liquid air energy storage (LAES) • When it is cheaper (usually at night), electricity is used to cool air from the atmosphere to -195 degree centigrade where it liquefies. • Volume of liquid air comes down to 1000 times compared to ambient air, so can be kept in a large vacuum flask at atmospheric pressure. • At time of high demand the liquid air is heated again to turn it back into the gas. • The massive increase in volume and pressure is used to drive a turbine.
- 11. A schematic
- 12. Configuration
- 13. Super conducting magnetic energy storage (SMES) • Super Conducting Magnetic Energy Storage (SMES) system stores energy in the magnetic field created by the flow of direct current in a super conducting coil. • A coil when cryogenically cooled to a temperature bellow its super conducting critical temperature the it becomes a super conducting coil. • A typical SMES system includes three part- 1. Super conducting coil 2. Power conditioning system 3. Cryogenically cooled refrigerator
- 14. Configuration
- 15. A schematic
- 16. Advantages over other energy storage method • Time delay during charging and discharging is quite short. • Power is available almost instantaneously. • Very high power can be provided for a small period of time. • Loss of power is less than other storage methods because electric currents encounter almost no resistance.
- 17. Configuration of the coil • Configuration of the coil itself is an important issue from a mechanical engineering aspect. • There are three factors which affect the design- 1. Strain tolerance 2. Thermal contraction upon cooling 3. Lorentz forces in a charged coil
- 18. Current use • Several 1 MWh units are being used for power quality control where the ultra clean power is required, such as Microchip fabrication unit. • These facilities have also been used to provide grid stability in distribution system in Finland.
- 19. Super capacitor energy storage (SCES) • It works same as battery charging and discharging system but offers- 1. High life cycle (>500000 cycled times) 2. Quickly charge/discharge (>1000A) 3. Operating temperature range (-50℃-70 ℃ ) 4. Environment friendly
- 20. Configuration
- 22. Certain Limitations of Supercapacitor • Low energy density • Linear discharge voltage prevents use of the full energy spectrum. • Cells have low voltages • High self-discharge • Voltage is limited to 2.7 V only • We cannot go beyond three series connected capacitor without voltage balancing system to protect over voltage of individual capacitors.
- 23. Flywheel energy storage (FES) • It uses a flywheel for storing off peak energy in the form of kinetic energy. • It offers comparatively small power with a peak power of up to 20 MW • It practically used to compensate fluctuation of power in wind or solar power plant. 2 2 1 = IE
- 24. Configuration
- 25. Aspects of efficiency • The system has very low rotational losses due to the use of magnetic bearings which prevent the contact between the stationary and rotating parts, thus decreasing the friction. • In addition, because the system operates in vacuum, the aerodynamic resistance of the rotor is outstandingly reduced. • These features permit the system to reach efficiencies higher than 80%. • It provides 100% angular stability of grid.
- 26. Power-to-Gas (P2G) • It converts off-peak electrical power to a gas fuel, again which is used to generate electrical power during peak hours. • Typically the electrical power is used to split water into hydrogen and oxygen by means of electrolysis. • Hydrogen and Oxygen separately used to drive gas turbine. • The storage capacity of German natural gas network is more than 200,000 GWh which is enough for several months of energy requirement of German.
- 27. Configuration
- 28. Efficiency • In 2013 the round trip efficiency of P2G storage was bellow 50% • In 2015 a study published in ‘Energy and Environmental Science’ claims that efficiency can be reached up to 70% cost effectively.
- 29. Pumped-storage hydroelectricity • The method stores energy in the form of gravitational potential energy of water during off-peak hours. • During peak hours that potential energy of water is converted to electrical energy. • The same turbine is used as a pump when lifts water to high level reservoir from low level reservoir.
- 30. Configuration
- 31. Plug-in hybrid electric vehicles • Daily load leveling • Frequency regulation • Reserved power • Large-scale use: reduce battery costs through competition and mass production
- 32. Inside the campus of University of Delaware, United States
- 33. Thermal storage • Thermal Storage is mainly divided into two parts- 1. Hot thermal storage 2. Cold thermal storage
- 35. Hot thermal storage • Hot thermal storage is generally used with solar collectors. • Store heat energy in hot water for later use. • Reduce electricity demand for hot water
- 36. Cold thermal storage • A cold storage system generates ice to chill water for air conditioning. • Shift electricity demand for air conditioning from day to night.
- 37. Construction
- 38. State of Charge management between BES & CAES PCC computing state of charge K local parameter rtdv PI PWMPI n DESU − + vscV vscI current regulationvoltage regulation + − + −+ − 1errorv * 1errorv 2errorv * vscv errorirefi * i
- 39. SoC management during discharging
- 40. Evaluation of performance Management scheme Controller SoC equalization time (Sec) Mean equalization error (%) State of charge Proposed STDE 4.82 0.0250 Conventional PMS 9.34 (quasi) 1.8724
- 41. Parameters of an Energy Storage Device • Power Capacity: is the maximum instantaneous output that an energy storage device can provide, usually measured in kilowatts (kW) or megawatts (MW). • Energy Storage Capacity: is the amount of electrical energy the device can store usually measured in kilowatt‐hours (kWh) or megawatt‐hours (MWh). • Efficiency: indicates the quantity of electricity which can be recovered as a percentage of the electricity used to charge the device. • Response Time: is the length of time it takes the storage device to start releasing power. • Round‐Trip Efficiency: indicates the quantity of electricity which can be recovered as a percentage of the electricity used to charge and discharge the device.
- 42. Energy Storage Applications 1/11
- 43. Energy Storage Applications 2/11 Energy storage devices can accommodate a number of network requirements. These are: • Load management • Spinning reserve • Transmission and distribution stabilisation • Transmission upgrade deferral • Peak generation • Renewable energy integration • End‐use applications • Emergency back‐up • Demand Side Management (DSM)
- 44. 1: Load management 3/11 There are two different aspects to load management: 1. Load levelling: using off‐peak power to charge the energy storage device and subsequently allowing it to discharge during peak demand. As a result, the overall power production requirements become flatter and thus cheaper base load power production can be increased. 2. Load following: energy storage device acts as a sink when power required falls below production levels and acts as a source when power required is above production levels. Energy devices required for load management must be in the 1 MW to 100+ MW range as well as possessing fast response characteristics.
- 45. 2: Spinning reserve 4/11 Once again spinning reserve is classified under two categories: 1. Fast response spinning reserve: power capacity that is kept in the state of ‘hot‐stand‐by’. As a result it is capable of responding to network abnormalities quickly. 2. Conventional spinning reserve: power capacity that requires a slower response. Energy storage devices used for spinning reserve usually require power ratings of 10 MW to 400 MW and are required between 20 to 50 times per year.
- 46. 3: Transmission and distribution stabilisation 5/11 Energy storage devices are required to stabilise the system after a fault occurs on the network by absorbing or delivering power to generators when needed to keep them turning at the same speed. These faults induce phase angle, voltage and frequency irregularities that are corrected by the storage device. Consequently, fast response and very high power ratings (1 MW to 10 MW) are essential.
- 47. 4: Transmission upgrade deferral 6/11 ✓Typically, transmission lines must be built to handle the maximum load required and hence it is only partially loaded for the majority of each day. ✓Therefore, by installing a storage device, the power across the transmission line can maintained a constant even during periods of low demand. Then when demand increases, the storage device is discharge preventing the need for extra capacity on the transmission line to supply the required power. Therefore, upgrades in transmission line capacities can be avoided. ✓Storage devices for this application must have a power capacity of kW to several hundreds of megawatts and a storage capacity of 1 to 3 hours. Currently the most common alternative is portable generators; with diesel and fossil fuel power generators as long term solutions and biodiesel generators as a short term solution.
- 48. 5: Peak generation 7/11 Energy storage devices can be charged during off‐peak hours and then used to provide electricity when it is the most expensive, during short peak production periods.
- 49. 6: Renewable energy integration 8/11 In order to aid the integration of renewable resources, energy storage could be used to: 1. Match the output from renewable resources to the load required 2. Store renewable energy during off‐peak time periods for use during peak hours 3. Act as ‘renewable back‐up’ by storing enough electricity when it is available to supply electricity when it isn’t available 4. Smooth output fluctuations from a renewable resource A storage system used with renewable technology must have a power capacity of 10 kW to 100 MW, have fast response times (less than a second), excellent cycling characteristics and a good lifespan (100 to 1,000 cycles per year).
- 50. 7: End‐use applications 9/11 ✓ The most common end‐use application is power quality which primarily consists of voltage and frequency control. ✓Transit and end‐use ride‐through are applications requiring short power durations and fast response times, in order to level fluctuations, prevent voltage irregularities and provide frequency regulation. ✓This is primarily used on sensitive processing equipment.
- 51. 8: Emergency back‐up 10/11 ✓ This is a type of UPS except the units must have longer energy storage capacities. ✓The energy storage device must be able to provide power while generation is cut altogether. ✓Power ratings of 1 MW for durations up to one day are most common.
- 52. 9: Demand Side Management (DSM) 11/11 DSM involves actions that encourage end‐users to modify their level and pattern of energy usage. Energy storage can be used to provide a suitable sink or source in order to facilitate the integration of DSM. Conversely, DSM can be used to reduce the amount of energy storage capacity required in order to improve the network.
- 53. Energy Storage Plant Components Before discussing the technologies, a brief explanation of the components required to have an energy storage device are discussed. Every energy storage facility is comprised of three primary components: 1. Storage Medium 2. Power Conversion System (PCS) 3. Balance of Plant (BOP)
- 54. Storage Medium ✓The storage medium is the ‘energy reservoir’ that retains the potential energy within a storage device. ✓It ranges from mechanical (Pumped‐Hydroelectric Energy Storage), chemical (Battery Energy Storage) and electrical (Superconducting Magnetic Energy Storage) potential energy.
- 55. Power Conversion System (PCS) ✓It is necessary to convert from alternating current (AC) to direct current (DC) and vice versa, for all storage devices except mechanical storage devices e.g. Pumped‐Hydroelectric and Compressed Air energy storage. Consequently, a PCS is required that acts as a rectifier while the energy device is charged (AC to DC) and as an inverter when the device is discharged (DC to AC). ✓The customization of the PCS for individual storage systems has been identified as one of the primary sources of improvement for energy storage facilities, as each storage device operates differently during charging, standing and discharging ✓Development of PCSs has been slow due to the limited growth in distributed energy resources e.g. small scale power generation technologies ranging from 3 to 10,000 kW.
- 56. Balance of Plant (BOP) These are all the devices that: ✓ Are used to house the equipment ✓ Control the environment of the storage facility ✓ Provide the electrical connection between the PCS and the power grid • It is the most variable cost component within an energy storage device due to the various requirements for each facility. The BOP “typically includes electrical interconnections, surge protection devices, a support rack for the storage medium, the facility shelter and environmental control systems” .
- 57. Typical Suitability of Storage Technologies to Different Applications
- 58. Comparison of Energy Storage Technologies • PHES: Pumped‐Hydroelectric Energy Storage • UPHES: • CAES:Compressed Air Energy Storage • BES: Battery Energy Storage • FBES:Flow Battery Energy Storage • FES:Flywheel Energy Storage • SCES:Supercapacitor Energy Storage • SMES:Superconducting Magnetic Energy Storage • HESS:Hydrogen Energy Storage System • TESS:Thermal Energy Storage System • Evs:
- 59. Comparison of Energy Storage Technologies
- 60. Comparison of Energy Storage Technologies
- 62. Conclusion • Current renewable technologies require storage possibilities • Pumped-storage hydroelectricity is currently the only viable solution • Flywheels, SMES, SCES and batteries possess small potential • CAES shows the greatest potential
- 63. References • Arani, AA Khodadoost, G. B. Gharehpetian, and M. Abedi. "Review on energy storage systems control methods in microgrids." International journal of electrical power & energy systems 107 (2019): 745-757. • Aneke, Mathew, and Meihong Wang. "Energy storage technologies and real life applications–A state of the art review." Applied Energy 179 (2016): 350- 377.
- 64. Question? • What are the major parameters of an energy storage device? • What are the energy storage applications?