INEES Workshop, 24.09.2012
Technical Considerations for Wind
Power in Hot Climates
Presented by M.Eng Robert Rudolf
Prepared by Florian Roscheck & R. Rudolf
A Challenging Environment
>High Temperatures
> Machine Cooling & Lubrication considerations
> Material Strength Issues
> Accelerated Corroision
>Accelerated Erosion
>Rain Impact (tropical climates)
>Sand Abrasion (deserts)
>Structural Considerations
>Application not suitable for concrete
>Storm Loads may > IEC design loads
>Complex Ground Conditions
>Electrical Grounding in Sand
Source: http://www.companysj.com/v244/hurricane.html {{PD}}
16.03.2012 . Page 2 .
Existing Wind Parks
Name
Tehachapi Pass Wind
Farm
Ashegoda Wind Farm
Sir Bani Yas Island Wind Farm
Power
700 MW [1]
120 MW [2]
30 MW [3]
Location
Near Mojave desert,
California, USA
Tigrai State, Ethiopia
Western coast of Abu Dhabi,
United Arab Emirates
Date est.
1980s
2009 (first phase)
In development
http://clui.org/ludb/site/tehachapi- http://ees.kuleuven.be/liveli Masdar Power: Working to Power The
wind-farm, 2012-09-14
hood2013/excursions/index. Future
html, 2012-09-14
16.03.2012 . Page 3 .
Global Highest Temperature Map
Sir Bani Yas Island
Tehachapi Pass
Ashegoda
Source: NASA maps
by Jesse Allen and
Robert Simmon
16.03.2012 . Page 4 .
Global Wind Map
Sir Bani Yas Island
Tehachapi Pass
Ashegoda
Source: Global Energy
Network Institute
16.03.2012 . Page 5 .
Global Wind & Max. Temp. Overlay Map
Sir Bani Yas Island
Tehachapi Pass
Ashegoda
Source: Global Energy
Network Institute
16.03.2012 . Page 6 .
Risks – High Temperatures
> IEC 61400 guarantees performance only to 40C
> De-rating above 40°C, shut-down above
45°C (Vestas V52)
> Following Components are typically
cooled
> converter/inverter
> control system electronics
> transformer
> generator
> Hot climates may require additional
systems
> Oil Cooler
16.03.2012 . Page 7 .
Cooling Systems
> High Power Demand
> 1% efficiency loss * 3MW 
30kW add. cooling requirement
> Water-based systems risk freezing,
corrosion, flooding
> Move to refrigerant-based
systems to reduce maintenance
> High cooling requirement  high air
flow
> Intake and exhaust need to filter
out sand, prevent clogging
> High air flow through nacelle 
increased risk of corrosion
16.03.2012 . Page 8 .
Enercon Cooling System
16.03.2012 . Page 9 .
Risks – Material Failure
> Material Limits – (applicable to plastics & composites)
Material
Glass transition temperature
PA-6 (dry)
78 °C
PVC
80 °C
ABS
110 °C
Epoxy Resin (Nordex, Repower) 50 - 260 °C (65°C is min.
allowed)
Polyester Resin (LM)
> Component Limits
Component
Max. operating
temperature
Generators [4]
180 °C
Oil [5]
80 °C
Encapsulated electrical
components [6]
40 °C
16.03.2012 . Page 10 .
http://www.eng.cam.ac.uk/news/stori
es/2007/bamboo_wind_turbines/
Lubrication Issues [6]
> Gear box of turbine has to be lubricated
> Problem: High oil temperatures reduce lifetime of oil
> If max. rated oil temperature constantly exceeded by
10°C, oil lifetime is reduced by a half.
> Mineral oils can be used up to 80 °C oil temperature
> For hot climates, oil cooler may be needed for lubrication
system
> Risk in sandy environment: Cooling system can be blocked
16.03.2012 . Page 11 .
Lubrication Cont‘d. [6]
>
Major Bearings & Powertrain lubrication are critical to component life
http://www.windsupco.com/lubri
cs.php
>
>
Gearbox lubrication is critical to component lifetime
Problem: High oil temperatures reduce lifetime of oil
> Mineral oils can be used up to 80 °C oil temperature
> If max. rated oil temperature constantly exceeded by 10°C, oil lifetime is reduced by a
half.
> Problem of sandy environment: Cooling system can be blocked  insufficient
maintenance & bearing wear
16.03.2012 . Page 12 .
16.03.2012 . Page 13 .
http://www.windsupco.com/lubrication_basi
cs.php
Risk – Corrosion
> Effects of oxygen
concentration and
temperature on the
corrosion of low-carbon
steel pipes are indicated in
the diagram below.
>
16.03.2012 . Page 14 .
Source:
http://www.engineeringtoolbox.com/oxyg
en-steel-pipe-corrosion-d_1170.html
Risk –Abrasion,Rotor Performance
> Turbine design life is 20 years [1]
> Surface finish of blades deterioriates very rapidly
> Up to 20% loss of performance after 1 year [1]
> Tremendous loss of production (and ROI)
> Countermeasure: wear-resistant tapes & paints on leading edge
> Cost is approx. 1k euro/yr. (lasts approx. 5 yr.)
16.03.2012 . Page 15 .
Aerodynamic Performance
Comparison for „Clean“ vs. „Rough“
> Thicker blade has marginally better „clean“ flow performance &
marginally worse „rough“ AEP
16.03.2012 . Page 16 .
Concrete Towers & Foundations
> Are concrete towers practical for the Desert?
> Thermal Cracking issues (bad combination with high
fatigue loads of W.T. @ 2-3 million load cycles)
> High temperatures complicate construction
> Fast set  less time to grow crystals  less
strength
> 10°C higher temp.  10% lower ultimate
compressive strength
> Risk of plastic shrinkage cracking [7]
> If not, other alternatives (Guyed towers & Lattice towers)
are needed to support current trends in upscaling and lowwind-specific turbine design
16.03.2012 . Page 17 .
Foundations – Lightning [7]
>
>
>
>
>
Turbines need lightning protection
Foundation is part of lightning protection earthing system
Required resistance of earthing system <= 10 Ω (low)
Problem: Dry soil -> high resistance
Solution: Earth electrodes with high soil contact -> low
resistance
16.03.2012 . Page 18 .
Hot Climate Regions are prone to
Extreme Weather
53m/s
52m/s
83m/s
78m/s
16.03.2012 . Page 19 .
IEC Class 1A rating not strong enough
Source: Vergnet Wind Turbines
16.03.2012 . Page 20 .
Survival Strategy: Retreat!!!
16.03.2012 . Page 21 .
Survival Strategy: Retreat!!!
16.03.2012 . Page 22 .
Erosion
> Large Wind Farms in proximity to agriculture or residential
areas could exacerbate wind-driven erosion due to
considerable turbulence [8]
Tehachapi Mountains,
Source: The American West at Risk,
http://www.theamericanwestatrisk.com/photos.
html, 2012-09-14
16.03.2012 . Page 23 .
Tehachapi Mountains,
Source: Wind-Works.org,
http://www.windworks.org/articles/TehErosi
on.html
Questions?
> What was least clear?
> What was most interesting?
> Anything come to mind that we should include?
....Thanks!
16.03.2012 . Page 24 .
Appendix I - Sources (1/2)
[1]
Hill, J. S. : Wind Energy Research to Maximise Power Generation; in: Clean Technica,
2011-12-15, http://cleantechnica.com/2011/12/15/wind-energy-research- to-maximisepower-generation/
[2]
Tigrai Online: Ashegoda Wind Farm in Tigrai State starts generating 30 MW in test
phase, 2012-02-27, http://www.tigraionline.com/articles/article120235.html
[3]
Dodd, J. : Masdar sets tender for 30MW Abu Dhabi Project; in: Wind Power Monthly,
2011-07-09, http://www.windpowermonthly.com/go/middleeastafrica/news/
1074347/Masdar-sets-tender-30MW-Abu-Dhabi-project/
[4]
Biechl, H. : Erwärmung elektrischer Maschinen, Teil 1, Fachhochschule Kempten, 2008
[5]
Conversation via E-Mail with Castrol
[6]
Hinrichs, J., Miller, J., Petersen, Lars, Petersen, Lennart, Vajhøj: Auswirkungen von
heißen klimatischen Bedingungen auf Windenergieanlagen, Fachhochschule Flensburg,
2012
16.03.2012 . Page 25 .
Appendix II - Sources (2/2)
[7]
http://www.concretenetwork.com/hot-weather-concreting/problem.html
[8]
16.03.2012 . Page 26 .
Appendix III:
16.03.2012 . Page 27 .
Wind  Water