Energy Storage in Offshore Wind Generation. Alan Ruddell UK Innovation Forum Birmingham, 28 November 2012

Transcription

1 Energy Storage in Offshore Wind Generation Alan Ruddell UK Innovation Forum Birmingham, 28 November 2012

2 Scope of the presentation Part 1: Overview of Energy Research at STFC Energy Research unit Research into materials for hydrogen storage Spinout company: Cella Energy Spinout company: Cryox Part 2: Supergen Wind Energy Assessment of storage technologies and systems Modelling of energy storage Simulation of offshore network Cost-benefit analysis

3 STFC Energy Research Unit Established over 25 years ago Research topics in renewable energy includes wind energy, grid integration, energy storage, and hydrogen energy systems Provides information to assist policy makers and researchers to identify key research challenges Provides the UKERC Research Atlas Research Register, Landscapes, Road Maps and Energy Data Centre

4 STFC Research into materials for hydrogen storage ISIS pulsed neutron source enabled studies of hydrogen storage materials University of Oxford synthesised many new materials for hydrogen storage Experiment cycles hydrogen in and out of candidate materials, while observing what is happening at the atomic level Materials identified contain a higher density of hydrogen (illustrated as white spheres) than liquid hydrogen itself The material is not easily recyclable Ultra-lightweight materials, Li4BN3H10 (left) and LiNH2 (right), offer significant hydrogen storage potential, around 12 wt%

5 STFC spin-out: Cella Energy Encapsulation & nano-structuring of chemical hydrides in plastic 1 gm of pellets will store/produce 1 litre of hydrogen Performance already 9 wt% hydrogen (DOE s 2017 target for vehicles is 5.5 weight % hydrogen) Initial target markets Battery replacement (3 x specific energy of lithium-ion) Emission abatement (increase efficiency and reduce particulate emissions) Space radiation shielding (high hydrogen materials are best for low weight) Longer-term: Hydrogen Zero Emission Vehicles, with pellets handled as a fluid

6 STFC spin-out: Cryox Spin-out from MRI and STFC space cooler technology Shop-front for STFC cryogenic technology Planck spacecraft Distance from Earth: 1.4 Million km Commercialisation of cryogenic & superconducting technology Cryo-cooling, superconductivity, cryogen-free systems Advanced cryostats, high efficiency process equipment Cryo-mechanisms, cryogenic materials, cryogenic modelling For example, Cryox has been involved with Converteam in development of superconducting wind turbine generators >5MW 50% smaller generators, reliable direct drive ~200 tons less weight in the nacelle (results in 4:1 saving below) Reduced rare earth materials Lifetime efficiency gains

7 Supergen Wind Energy Connection theme In collaboration with Durham University, University of Manchester (Theme Leader), University of Strathclyde Potential needs for energy storage for offshore connection Phase 3: Assessment of storage technologies and systems Wind turbine rotor inertial storage Flywheel energy storage Ultracapacitor energy storage Lithium-ion battery energy storage Power electronic interfaces Future research (Phase 4) Modelling of energy storage Simulation of offshore network Analysis of benefits

8 Energy storage and wind turbines: the present scene Numerous demonstrations of energy storage with wind turbines in evaluation / planned. Most are relatively small-scale Single wind turbines. e.g. 0.5MW, 30s. Power from a single wind turbine, especially fixed speed, can have high variability. Storage avoids local network power quality disturbance Standalone (e.g. wind-diesel) power systems. e.g. 0.5MW, 30s. Storage enables maximum wind penetration and fuel savings. Remote wind farms e.g. 10MW, 5 20MWh. Combining the outputs of wind turbines results in lower statistical power variation, due to lack of correlation introduced due to distance. In addition the use of control systems with variable speed operation means that the power output is smoothed by rotor inertia. However wind farms may be at the end of long feeders, and storage avoids grid reinforcement EPRI (2004) report discusses the integration of wind power onshore in the electrical network & quantifies the benefits of electrical storage technologies. A CEC/US-DOE project is to demonstrate the use of an ultracapacitor energy storage module in support of a selection of distributed energy resources, including a wind turbine that could potentially be configured as an electric microgrid. Cigre Brochure 370 Integration of Large Scale Wind Generation Using HVDC and Power Electronics discusses future requirements in transmission and distribution applications. Many technical papers analyse the feasibility of including storage in FACTS, including STATCOMs with possible application to wind farms.

9 Potential needs for energy storage in a far-offshore connection / transmission scheme Research basis for Theme 3: HVDC VSC 900MW +/- 320kV up to 150km transmission Offshore a.c. network: 690V/33kV/132kV Ref: North Sea Offshore Transmission Basic Connection Schemes, Theme 3, Olimpo Anaya-Lara, Strathclyde) Offshore Network OT -> DC Td1 Onshore Grid 1 (UK) Offshore Wind Farm Integration of energy storage Turbine trips Stability Power High (per turbine) Low-medium (per wind farm) Storage time Seconds - minutes Seconds Response Sub-second Sub-second Cycling Low High Storage technology Supercapacitor, Flywheel, Battery Power Storage time Response Cycling Storage technology Avoiding curtailment High Hours Minutes Low Flow cell Battery

10 Capacity [Wh] Storage capacity 1,000, ,000 10,000 Capacity vs Power 1 second 10 seconds For a 2MW wind turbine operating at rated power: 1 second of storage is around 500Wh 100 seconds 1, Power [MW]

11 rotor inertia constant [s] Wind turbine rotor inertial storage Relationships between turbine power, rotor diameter, mass, inertia can be derived (based on fit to data for available turbines) The rotor inertia constant generally increases with turbine power However the inertia is highly sensitive to rotor diameter and tip speed for any power (as shown by the spread for 2011 Vestas turbines) Tip speed Power Rotor diameter Rotor mass Total rotor inertia constant The total inertia constant can be around 10 seconds for large wind turbines. This can be used to reduce torque transients, optimise energy capture, and smooth power output Only a fraction of the total rotor inertia could be available as on demand storage The rotor would be operated above the optimum speed, resulting in loss of energy production References: EWEA, Wind Energy The Facts (2009); De Haan (2011); Wu (2011); Rawn (2010); Ramtharan (2007); Li (2004); Stock (2012) Rated power [MW] formula Vestas 2011

12 Flywheel energy storage Manufacturers include: Beacon Power, Vycon, Kinetic Traction Systems, Piller, Temporal Power and Active Power Applications include UPS, transportation, hybrid vehicle, rail trackside support, and grid support Commercialisation has been slow Manufacturer Beacon Power Rotor Type Carbonfibre Composite Rotor Bearings Speed (rpm) 16,000 Active Magnetic Power Rating 100kW Energy 25 kwh (15 min) Standby Loss 2% of rated power (2kW) Main application grid-stabilisation Vycon Energy 4340 Steel 36,750 Active Magnetic 300kW 1.1 kwh (40 s) UPS market Beacon Power 100kW / 25kWh flywheel Kinetic Traction Systems (KTS) Carbon fibre 36,000 Magnetic and hydrodynamic 200kW 1.5kWh (30 s) 1% of rated power (2kW) railway regenerative braking

13 Flywheel energy storage High cycling capability > 100,000 full cycles Lifetime of 15-20yrs some components need replacing more regularly Low maintenance required Operating temperature typically C to 45 0 C Round trip efficiency of 85-90% Very high standby power losses. Usually not specified. Loss can range from 1% - 2% per minute Multiple modules used for high power/energy systems Installation costs are usually not published a Beacon Power flywheel cost $1,630 per kw in 2007 Possible future performance improvements: reduction of losses superconducting magnetic bearings permanent magnet bearings (Temporal Power) Power Blueprint Energy flywheel performance characteristics (2012) Characteristic Energy Storage Mass Volume Specific power Power density Specific energy Energy density Current spec. 120 kw 0.77 kwh 150 kg 103 litres 800 W/kg 1,165 W/litre 5.1Wh/kg 7.5 Wh/litre Round trip efficiency 86%

14 Ultracapacitor energy storage aka electric double layer capacitors (EDLC), supercapacitors, electrochemical capacitors Major manufacturers include: Maxwell (USA), IOXUS (USA), NESSCAP (S.Korea), EPCOS (Europe) and Okamura Laboratory (Japan) Commercialisation and market growth is rapid: in the last 10 years the market has grown 25% per year, and the growth rate is increasing (NESSCAP) over the last 10 years the cost has fallen by 99% and is continuing to fall, due to automation of the manufacturing process and development of more efficient technologies the cost of ultracapacitors is falling at a faster rate than the cost of batteries Ultracapacitor modules used in wind turbine blade pitch control systems Reduces lifetime maintenance costs Durable and reliable > 1,000,000 cycles Eliminates reliance on batteries or maintenance issues with hydraulic systems High performance in all weather conditions from -40 to +65 C Parameter Capacitance Rated voltage Continuous current Weight Maximum energy Specific power Specific energy Spec. 94 F 75 V 48 A (@ 15 C) 25 kg 73 Wh 2,100 W/kg 2.9 Wh/kg

15 Ultracapacitor energy storage Ultracapacitors use electrodes of ultra-high surface area activated carbon The surface area of a carbon electrode is m 2 / g Provides much greater charge storage than that of traditional capacitors Main advantages: No maintenance required after installation Lifetime of years High cycle life 500,000-1,000,000+ cycles between max. voltage Vr and ½Vr Round-trip efficiency 90% + Rapid load response / high power potential Wide operating temperature range -40 C to +65 C Wide range of environmental conditions (including the vibrations to be expected on offshore turbines) 1/5th the weight of an equivalent battery system (for the wind turbine pitch control application) Main disadvantages: High cost ($6000 per kwh in 2010) Low energy Moderate self-discharge typically up to 2% per day for capacitors (much higher in modules with cell balancing) Future developments: development of electrode materials with higher surface area including using carbon nanotube technology may result in dramatic improvement of x10 energy density

16 Lithium ion battery energy storage AES Energy Storage has 70 MW of grid storage in operation in: 6 US systems and Chile provides ancillary services stores excess wind power during curtailment Laurel Mountain Wind farm: 61 turbines, 98MW AES energy storage: approx 32MW / 8MWh / $23M A123 Systems supplies lithium ion batteries to system developers is to supply 6 systems to Northern Powergrid for peak load shifting, voltage fluctuations systems use stacks of multiple cells A123 Lithium ion cell 3.3V 2.5Ah (8.25Wh nom.) 26mm dia x 65mm long, 76 g 2,600 W/kg 5,800 W/litre > 1000 full cycles Xtreme Power - Dynamic Power Resources (DPR) DPR containerised module 1.5MVA, 1MWh Container size 40x11x11 ft, total weight 100,000 lbs Overall system approx. 33 W/kg; 11 W/litre Overall system round trip efficiency > 90% Uses XP s 12V 1kWh PowerCell module Wind farm applications, e.g. Maui 20MW wind farm (2011), storage 10 MW / 20 MWh stores excess power during curtailment periods also provides ramp control, frequency and voltage ancillary services Xtreme Power DPR C Containerised Unit

17 Energy storage interfaces power electronics ABB power electronics systems for energy storage interfacing and grid stabilisation: PCS100 voltage source converter (LV or MV with transformer; 100kVA 10MVA is based on IGBT technology, and provides an interface for batteries, flywheel, supercapacitors DynaPeaQ includes energy storage, provides active / reactive power. Combines SVC-Light (STATCOM) with lithium-ion battery storage. Typical power 5-50MW for 5-60 minutes (5MWh) generator line P load Q load load P inj Q inj Energy storage SVC Light

18 Size comparison of flywheels and Li-ion batteries systems (20MW / 5MWh system 15min storage) Beacon Power 1 st large scale system 20MW / 5MWh Installed July 2011 in New York cost $69M Provides fast-response frequency regulation Plant connected to NYSEG network at 115kV A large space is required! AES Energy Storage / A123 Systems Li-ion battery plant Phase 1 + 2: 20MW / 5 MWh (Phase 1: 8MW shown) Battery only costs generally around $1M / MW 2MW / 0.5MWh in container module (each 53ft long) Provides ancillary services and regulation Smaller than flywheel system 1 MW module: Power electronics interface and ancillaries Ten 100kW flywheels (blue lid, underground) The complete 20 MW system comprises 20 modules

19 Storage Technology choice Key considerations for offshore installation: Power / energy density Maintenance requirements Lifetime Environmental characteristics Cost Storage technology choice Ultracapacitors (high power / seconds ) Lithium-ion batteries (minutes) BorWin Alpha platform 400MW HVDC 130km offshore Photos: Wind Power Monthly and ABB

20 Energy density [Wh/kg] Storage Technologies gravimetric density Ragone chart: Gravimetric density lithium-ion cell flywheel Maximum Power density [W/kg] ultracapacitor 1 second 10 seconds 100 seconds Ultracapacitor offers high power density

21 Energy density [Wh/litre] Storage Technologies - volumetric density Volumetric density lithium-ion cell flywheel ultracapacitor 1 second 10 seconds 100 seconds Maximum Power density [W/litre] Ultracapacitor offers high power density

22 Phase 4: Simulation studies Task Energy storage sub-systems Define perfomance characteristics Develop Simulink models Task Simulation of power systems Investigate power system performance Range of network and turbine faults and over-frequency events Range of storage capacity & power ratings Produce storage power - time profile & frequency of occurrence Task Cost-benefit analysis Simulate operation using power time profiles Analyse storage lifetime expectation Assess capability / degradation

23 Sources of information: Storage technologies and applications Investire : Storage technologies for renewable energy available from UKERC (UK Energy Research Centre): Research Atlas and Landscapes available from Electricity Storage Association: Technology comparison available from EPRI-DOE Handbook of Energy Storage for Transmission & Distribution Applications available from DOE Energy Storage Systems Program (ESS) at Sandia Laboratories available from DOE Energy Storage database available from

24 Acknowledgement Supergen Wind Energy Research is funded by the Engineering and Physical Sciences Research Council