Application of Flywheels in Electric Grids With High Penetration of Renewable Energies

Transcription

1 Application of Flywheels in Electric Grids With High Penetration of Renewable Energies Marcos Lafoz CIEMAT. Madrid (Spain) 1

2 General concept of a flywheel A Kinetic Energy Storage System (KESS), also known as a Flywheel, is based on a simple principle: To storage energy in a rotating mass which is driven by an electrical machine. This machine exchanges power with the grid through two power converters connected by a dc-link. Levitation Guidance Electrical Machine Rotating Mass Machine-Side Converter dc link Control System Grid Side Converter External commands Guidance 2

3 Characteristics of Flywheels 1. Power and energy densities are high. 2. Power and energy are independent. 3. Continuous operation is possible. Very high number of cycles (charge-discharge frequency). 4. Fast response and overload capacity. 5. Not very high thermal dependant. 6. The technology is cost-effective when large scale application. 7. It has an interesting extension when combining with some other systems like batteries, hydro-pump or CAES, for many applications. 3

4 Flywheels Potential Applications FIELD Transportation Grid Stability Power generation Renewable Energies Critical loads Energy efficiency Smart Grids Hybrid storage systems DESCRIPTION Peak power leveling, power line stabilization, energy management and braking energy recuperation Power support during short peak consumptions in heavy loads, frequency regulation, voltage regulation (reactive power support) Big generators starting and power support during transients PV Solar: Power smoothing during transients (clouds) Wind: Power smoothing during transients (wind blasts) Wind Stand-alone: Reduction of Diesel start/stop Wave energy: Low frequency power oscillations smoothing Uninterruptible power supplies for high power/short term loads Increase the efficiency of reversible industrial systems (cranes and elevators) Stabilization and controllability of Distributed Generation Systems Combination of this fast energy storage devices with others 4

5 Frequency regulation becomes a problem in some grids Frequency regulation is mainly provided by the regulation groups (thermal, hydraulic, gas) and power from renewable energies goes directly to the electric grid. The higher is the wind power, the lower is the regulation capability. Reducing fossil fuel or conventional groups means reducing the electric grid regulation capability. Weak electric grids will be the first in being sensible to this problem: Islands, for instance.

6 EXAMPLE 1. Self.-sufficient energy in El Hierro Island El Hierro Island (Spain) Complete dependency on fuel until 2000 Very good renewable resources Initial situation Surface 278 km 2 Popullation Electricity demand: 35 GWh (2005) Installed power (Diesel): MW Punta de demanda: 6.3 MW

7 EXAMPLE 1. Self.-sufficient energy in El Hierro Island El Hierro Island (Spain) Upper deposit Lower deposit Mini hydro-electric plant Pumping plant Energy is managed from the wind by the pump-turbine plant. Hydro-Wind Plant Complete dependency on fuel until 2000 Valverde Wind plant 11MW of wind energy installed. Stability of the system is achieved by means of: 1. Hydro-pumping storage 2. Flywheel storage. Every turbine is equipped with a flywheel to increase the inertia. La Estaca port

8 EXAMPLE 2. Frequency regulation in Lanzarote Fuerteventura Increase the inertia to ensure the frequency and the voltage regulation of the system. 1.65MW 18MJ 2.9 ton 3,600 rpm Lanzarote 8

9 Power compensation in wave energy generation x Disposición óptima Disposición no-optima Potencia (W) tiempo (s) BUOY PLATE La fluctuations of the generated power are important, especially when a direct-drive is used in the power takeoff part. Flywheels are a good option for this since the storage and release of power is constant with some seconds of continuous cycles 9

10 CIEMAT developments in flywheels 2010 SA2VE: Railway substation. Energy saving. OMEGA-PLUS. ACE2 ENERGY 200MJ First prototype of Kinetic energy storage device (1999) SEDUCTOR Wind-Diesel Generation TOTAL POWER 350 kva DC VOLTAGE V RPM ACEBO: Renewable and SmartGrid applications OMEGA-MOTOR ENERGY - TOTAL POWER 120 kva DC VOLTAGE 1000 V RPM OMEGA ENERGY 5MJ TOTAL POWER 120 kva DC VOLTAGE V RPM ACEBO ENERGY 10MJ TOTAL POWER 25 kw DC VOLTAGE 1000 V RPM

11 After the experience in previous projects with Flywheels In 2010 CIEMAT started the ACEBO project(low Cost Kinetic Energy Storage System), a second generation flywheel, which is mainly based on the following concepts: 1. The technology has to be robust and competitive with other storage technologies (batteries and ultracapacitors). 2. Easy and cheap implementation 3. Power and energy high densities and independency 4. Modularity and flexibility in the design and the applications 5. Integration of the power electronics and the control with the mechanics 6. Easy to maintain with reduced OPEX. 7. Idle losses (during no operation) has to be reduced as maximum to improve the global efficiency 8. Additional value of the grid-connection converter to operate under unbalance loads conditions, isolated from the grid or frequency and voltage support 11

12 The ACEBO Technology description Once selected the power and energy range, dimensions of the flywheel and the bearings are defined. Electrical machine is designed to accomplish the requirements (power and speed). Rotor is constructed from the more convenient diameter for fabrication Conventional ceramic bearings Swithed reluctance machine Performance Summary Overall Energy 10 MJ Maximum Power 25 kw Nominal Voltage 1,000 V Maximum RPM 9,000 12

13 Power electronics and control Application of Flywheels in Electric Grids The ACEBO Technology description Integration of the electrical machine, the flywheel, levitation, power electronics and control in the same housing. Modular mechanical battery. Electrical machine Flywheel Magnetic levitation of the flywheel releases axial forces from the bearings and a reduced pressure atmosphere is provided inside of a vacuum chamber to reduce the aerodynamic losses 13

14 The ACEBO Technology description Half-Bridge topology used to drive the machine PWM commutation signals Control commands SRM current experimental results Alarms IGBT DSP TI28335 Power electronics and control Electrical machine Flywheel Analog current measurements Temperature measurements Analog voltage measurements 14

15 ACEBO Control and Communication Monitoring and control environment 15

16 The ACEBO Characterization Supplying times when operating with constant power at different levels (levels without overloading the machine). For example, the system can deliver 10 kw to the grid for about 5 minutes. Operation curves within the speed range maintaining constant current at different levels The available reserve energy is the kinetic energy stored in the flywheel at the speed of rpm. This amount of energy could be used in over-discharged situations with reduced delivered power levels. 16

17 The ACEBO Characterization Acceleration time= 27 s Self-discharging time= 38,2 min The flywheel is maintained between 90% and 100% of SOC waiting for the load to supply, which corresponds with a range of speed between 8700 and 9000 rpm. The system requires an average power of 390W to maintain that range of SOC (State of Charge). Losses Mechanical Losses (P mech ) Control Consumption (P control ) Average electrical losses (P acc ) Average maintaining power (P maint ) Quantity 210 W 150 W 30 W 390W Efficiency at different percentages of the nominal current E electric : Electrical energy used in deceleration processes E mechanicalstore : Kinetic energy stored in the flywheel 17

18 The ACEBO Testing area at CIEMAT ACEBO device during the testing at CIEMAT Lab. The facility includes a security pit and a separate control room. 18

19 The ACEBO Testing area at CIEMAT ACEBO prototype inside the testing security pit at CIEMAT Facilities Grid-side converter 19

20 The ACEBO flywheel will be integrated at the end of this year in a microgrid in CEDER Soria (Spain). 20

21 Additional valuesacebo Operability: Unbalanced loads The grid converter of the storage system provides additional values to compensate unbalanced loads or provide reactive power. This is specially important in very weak electric grids where phase voltages could be modified by unbalanced loads. Energy storage Grid currents Unbalanced load Load currents ACEBO Energy storage device 21

22 ACEBO Operability: Off-Grid operation The case of frequency and voltage support is specially important when the system turns into a off-grid mode. Tensión-Corriente-carga TENSIÓN Y CORRIENTE EN LA CARGA Tension-carga(V) Corriente-carga(A) 400 TRANSITORIO DE LA TENSION EN LA CARGA CUANDO DESAPARECE LA RED Tiempo(s) 350 TENSION EN LA CARGA EN EJES d-q Tension Carga(V) Tiempo(ms) Voltage transition when grid is disconnected and the storage system is stablishing the grid. Tensión-carga(V) Tiempo(s) Voltage and current in the load and module of the peak voltage when the grid is restablished. 22

23 Thankyoufor yourattention 23