Ies keysan 03_03

Ozan Keysan - IES SeminarMarch 2010

C-GEN Direct Drive System forMarine Renewables

March 2010

OZAN [email protected]

Institute for Energy Systems

The University of Edinburgh

March 2010 Ozan Keysan – [email protected]– IES Seminar

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Overview

C-Gen Concept Project Description

Overview of Current Systems Direct Drive Design Options Design Method Optimization Method

Questions


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Direct-Drive Systems Advantages

Minimum moving parts High reliability Higher efficiency

Disadvantages Not off the shelf components Difficult to assemble Increased mass (Structural) Enercon 6MW


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C-GEN Concept

Air-Cored PM No Attraction Force Easy Assembly Reduced Structure

Mass Modular Structure

Easy Assembly Custom Designs


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C-GEN Prototypes

20 kW – 1st Prototype

15 kW – Myres Hills

Linear Prototype


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Project Definition


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OYSTER

Oyster(1st version) Hydro-Electric Wave Energy Converter Launched November 2009 EMEC / Orkney 315kW

g


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OYSTER

Pros Simple/Robust No Offshore Electronics

Cons Reduced Efficiency Cost of High Pressure Pipe Installation

g


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Conceptual C-GEN Designs

Linear Partial Rotary Full Rotary

+ Easy to removefor maintenance

-End-stop problems-Exposed to sideway loading-Low active material utilization

+ Most efficient

-Heaviest type (structural mass)-Low active material utilization

+ No end-stop problems+Compact design+Max. material utilization

-Limited diameter-Reduced coil speed


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Direct Drive Case

Very low speed (~1rpm) High Torque Demand(~4MNm)

DD Generator 6m diameter, 120 tonnes Low Efficiency Material Cost > 10 years Electricity Income Economically Infeasible

g


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Single-Stage Gearbox

Direct Drive Maximum reliability High generator mass/cost

Single-Stage Gearbox More reliable than multi-stage Reduced generator size Higher utilization of magnetic material

g

Clipper Liberty 2.5MW


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Single-Stage GearboxSimulations with Different Gear

Ratios


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Optimum Design-OYSTER

Rating (4 x 300kW)

Diameter 4.1 m

Axial Length

0.9 m

Weight 14.6 t (2 x 7.3 t)0 10 20 30 40 50 60

70

75

80

85

90

95

100

Rotational Speed (RPM)

Eff

icie

nc

y(%

)

Efficiency vs. Rotational Speed


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SRTT

SRTT (2x550 kW) – 18 rpm Tests on 1/5th scale

Low installation cost Can be towed to shore Survivability mode

g

SRTT 1/5th Scale


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SRTT Stacking Options

X

RotorStructure

X

HubOuter Surface

FixedWindings

Radial Flux Axial Flux

Rotation Axis

Rotor

Stator Structure

Coils

Magnet


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Outer Stator Axial Flux

X

RotorStructure

X

HubOuter Surface

FixedWindings

•No stator structure•Lightest solution•Passive cooling with tidal current is possible•Minimum axial length•Identical machines (easy to control)


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Thermal Modelling

Increasing the thermal performance Utilizing tidal currents using cooling

ducts Water filled gap (Marinisation) Force cooling (fans, heat exchangers…)


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How to Stack?

Independent Flux Paths No Mass Advantage Increased Power Rating

Usual Stacking


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How to Stack?Independent

Flux PathsCombined Flux Path

Reduced Inner CoreThickness

Reduced Axial Length Reduced core mass

(up to %50)Core thickness

is limited by magnetic saturation

Inner Core thickness is not limited by

magnetic saturation


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How to Stack? – FEA


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Grid Connection

DCLink

Control

Inverter Step-upTransformer

AC/DC

Control

G

G

AC/DC

Control

G

G

AC/DC

Control

G

G

Modular structure enables various options Grouped/Separate Operation Common/Separate Inverter AC or DC Transmission

GAC

DC

Single SRTT

GAC

DC

Single SRTT

GAC

DC

Single SRTT

..

.

ACDC

OFFSHORE ONSHORE

Step-upTransformer


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Designs with Varying Radius

With increased diameter Active Mat. Mass Structural Mass Axial length Input (Fluid)

Power


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Optimum Design

Number of Stacks

6

Rating 550 kW

Diameter 3 m

Axial Length 0.7 m

Average Efficiency

89 %

Weight 13 t


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Advantages of Direct Drive

Less buoyancy required

Increased efficiency Minimum moving parts Redundant generators Center of gravity

lowered Passive cooling

SRTT 1/5th Scale


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AWS

AWS Linear PM Generator 2 MW – 2.2m/s Stator 5.6m Translator 8.4m

g

SRTT 1/5th Scale

1st Full Scale Prototype


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AWS Design OptionsSteel Core

Magnets

Coils

Runner

Steel CoreMagnets

Coils

Runner

TranslatorSupport

Pros Self-supporting core

structure Cons

Enclosed coils, decreased thermal performance

Weak translator support structure

Difficult disassembly

Pros Increased thermal

performance Strengthened

translator support Cons

Moment loading on translator


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AWS Design Options

Pros Better utilization of translator

support Eliminated side moment

loading Strengthened translator

support Cons

Increased active material mass


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AWS Design Options


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AWS Design Options

Number of Stacks

4

Rating (peak) 2 x 1MW

Translator Length

7.6 m

Stator Length 3 m

Average Efficiency

87 %

Total Weight 2 x 12 t


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SeaGen

MCT - SeaGen 2x600kW – 14 rpm 16m diameter blades Pitch controlled Mono-pole structure

Maintenance Mode High installation cost

g

SeaGen – Maintenance Mode


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Speed – Torque Characteristics of MCT

Nominal Nominal Speed:Speed: 14.3 RPM14.3 RPMTorque: Torque: 450 kNm450 kNmPower: 675 kWPower: 675 kW

MaximumMaximumSpeed:Speed: 17.5 RPM17.5 RPMTorque: Torque: 650 kNm650 kNmPower: 1200 kWPower: 1200 kW


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Optimization Method

? 22 variables Design Constraints Variable Speed


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Structural Modelling

Deflection in C-Core Magnetic Attraction Force

Deflection in Rotor Structure Torque Gravity


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Integrated Design

Coupled Models Electromagnetic Thermal Structural

Reduced Design Time Realistic Model More chance to find

the real optimum solution

Electromagnetic Structural

Thermal

Machine DimensionsMaterial PropertiesAmbient Conditions

Magnetic Attraction Forces

Structure Dimensions

EfficiencyPower Output

Power RequirementCurrent Density

Air gap Deflection

Structure Temperature

Total MassMaterial CostPower Output

Efficiency

Design Constraints


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Optimization Method

Genetic Algorithm

Initial Population Size: 2500Population Size: 400Mutation ratio: 0.03• For each design candidate, cost function is

calculated and designs with least value survives for next generation.


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Optimization Method

Most Efficient Lightest Smallest CheapestGenerator designs are

PROBABLY NOT the OPTIMUM

Solution

Objective Function should include;

Manufacturing Cost Electricity Income Design Constraints For All Speed Range


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Optimization Method

10

1 int )()}(.(.{)()(i incomesconstrakimaterial xfxfwpxfxF

Material Cost-Steel-Copper-Magnet (very expensive)

Constraints Penalty-Power output-Electrical limitations-Magnetic limitations-Structural limitations-Thermal limitations

Income from electrical generation-Availability-Energy Price -Losses

COST FUNCTION


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Optimum Design

Number of Stacks

8

Rating 575 kW (Nominal)1200 kW (Max.)

Diameter 3.2 m

Axial Length 0.7 m

Average Efficiency

89 %

Weight 15 t


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Summary

The C-Gen can be implemented to Marine Energy Converters More Reliable (Less Moving Parts) More Efficient Reduced mass compared to conventional DD systems

Integrated Model Approach + Genetic Algorithm Realistic Results Quick Not local minimums

Ozan Keysan - IES SeminarMarch 2010

Thank you for your attention

Technology

Ies keysan 03_03