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| CEST, Berlin| PDT, Los Angeles| EDT, New York
Nathalie Kermelk
Marian Willuhn
Dr. Thorsten Kray
Wind directionality and stowing
position: A new nexus for single-
axis tracker safety
29 July 20205 PM – 6 PM8 AM – 9 AM 11 AM – 12 PM
Ideematec
Philipp Klemm Markus Balz Hans Jürgen Sauter
&
WELCOME TO THE WEBINAR
“Wind directionality and stowing position: A new nexus for single-axis tracker safety“
IDEEMATEC – THE NEW DEFINITION OF DECOUPLED TRACKING
IDEEMATEC is a leading provider of solar trackers with +15 years of experienceand more than 2.5 GW of systems in operation on 6 continents.
IDEEMATEC – COMPANY PROFILE
#maximum economics #bifacial technology #safeguarding advantage
Outstanding technological innovations and over 50 patents deliver valuable benefits – through max. uptime availability
over the entire lifespan of a power plant.
SAFETRACK HORIZON – TECHNOLOGICAL BENEFITS
INSTALLED
TRACKER
+2.5 GW
PRODUCTION
CAPACITY P. WEEK
+60 MW
SIGNED & DELIVERED
YTD
+ 1.5 GW
EXPERIENCE
IN TRACKERS
+ 15 YEARS
COUNTRIES
CONTINENTS
25 / 6
WIND CLAIMS
WORLDWIDE
0
MARKET LEADER
MIDDLE EAST
AUSTRALIA
IDEEMATEC AT A GLANCE
WORLDWIDE PRESENCE – COMPANY PROFILE
AFRICA+130 MW
APAC+500 MW
EUROPE+375 MW
SOUTH AMERICA & MEXICO+100 MW
USA & CANADA+200 MW
MENA+810 MW
FOUNDED in Germany: 2003
REVENUE 2019: >100M US$
EMPLOYEES: 75 (2020)
+2.5 GW installed
safeTrack Horizon trackers H3/H4IDEEMATEC
Headquarter Germany
LOWEST cleaning solution capex 99.82% system availability globally
WIND DIRECTIONALITY AND STOWING POSITIONS: A NEXUS FOR SINGLE-AXIS TRACKERS
INVESTOR FOCUS:“A low-risk investment with steady and predictable cash flows for 20 to 30 years”.
MAIN TRENDS IN BANKABILITY
by Triana Group
by Solarbankability.eu
How the solar industry is responding to the increasing intensity of natural disasters
• Wind tunnel testing
• Compliance with UL standards:• UL 2703 (Grounding/Bonding Standards
for Rack Mounting System)• UL 3703 (Standard for Trackers)
• ASCE7 with CE marking
• SO Certifications – ISO 9001, ISO 14001 and ISO 18001
• Compliance with Eurocodes and SANS
• Number of utility scale projects in operation
• Technical due diligence on independent engineering reports by recognized firms such as: Leidos, Black & Veatch, Garrigues, TÜV SÜD, to name a few
49.80%Weather
36.10%Fire
9%Electrical Failure
2.30%Mechanical Breakdown
2.30%Lightning
0.50%Theft
PV CLAIMS IN NORTH AMERICA
Data taken from „Cell, Interrupted “ (2016) by GCube Insurance
Why worry about wind actions?
• It’s because without designing for the wind loads acting on a
single-axis tracker, wind-related damage of the structure may
occur.
• 50% of utility-scale PV failures have happened due to adverse
weather conditions1 where the vast majority of these failures can
be attributed to wind.
1 https://www.solarpowerworldonline.com/2018/01/solar-industry-responding-increasing-intensity-
natural-disasters/
Securing against wind related damage is crucial to the long term
profitability of a utility scale solar installation.
PV CLAIMS IN NORTH AMERICA
STOW STRATEGIES IN THE MARKET
30 degree stow
0 degree (flat) stow
https://www.solarpowerworldonline.com/2018/08/to-improve-solar-trackers-first-look-at-proven-fixed-tilt-strategies/
• Stow policy is associated with a critical wind speed
• Two distinct philosophies: stowing flat vs. stowing at high tilt
angles have high impact on associated wind actions
• A majority of tracker suppliers opt for either 30° stow or, in the
case of Ideematec, 0° stow
• Recent trend towards opting for a stow position of e.g. either -
30° or sometimes -10° (nose down) with the single-axis tracker
designed for worst-case wind actions from one 180° sector only
• To that extent the question arises whether the wind is really so
kind with us to not significantly change its direction during a
storm?
Jordan, Quweira 100 MW
ANALYSIS EXTRATROPICAL CYCLONE CIARA
by Triana Group
by Solarbankability.eu
Opting for a negative stow angle associated with a worst-case design for just one 180°
wind sector - does this strategy really work?
The latest major windstorm causing strong wind gusts in
Europe was the extratropical cyclone ‘Ciara’ on February
09/10 2020
The graph shows the variability of the maximum 3-second
gust within subsequent 10min intervals and of the wind
direction at the weather station in Werl, Germany, recorded
at 10m height
The curves show a mean wind direction swath of 60° over
the course of the storm with the gust wind speed above
20 m/s for most of the record
On a shorter timescale, consecutive data points show a
change in wind direction of up to 40°
ANALYSIS HURRICANE JEANNE
The graphs show wind data from Hurricane Jeanne that hit Vero Beach,
Florida on September 25/26 2004, recorded at 10m height
The green curve shows a mean wind direction swath of 135° over a 5
hour period
The yellow curve shows the 15-minute mean wind speed which
increased from 10 m/s to 20m/s over a 12 hour interval
At the same time, the maximum 3-second gust wind speed for each 15-
minute interval increased from 20m/s to 40m/s with the strongest gusts
almost reaching 50m/s during the wind direction swath
Opting for a negative stow angle associated with a worst-case design for just one 180°
wind sector - does this strategy really work?
VARIABILITY OF WIND SPEED AND DIRECTION DURING STORMS
• We have seen from legacy hurricane data that 3-second gust wind
speeds which were sustained above 20m/s featured a direction swath of
135° over a 5 hour period
• That being said, any tracker not designed for the full compass of wind
directions will sooner or later during a major wind event have to adjust
its stow position
• If a tracker needs to adjust stow position during a storm when conditions
are beyond its go-to-stow wind speed, it may be susceptible to failure
due to either aeroelastic instability or equivalent-static wind loading
exceeding the design wind loading.
• Therefore, at non-zero tilt angles only stow strategies are safe which are
designed for negative and positive tilt at the same time
Opting for a negative stow angle associated with a worst-case design for just one 180°
wind sector - does this strategy really work?
PRESSURE COEFFICIENTS ON PV MODULES
The design wind load of a PV module is defined according to the equation below:
w = Cp x qz x SW
• Cp [-] is a dimensionless pressure coefficient taken from a boundary layer wind tunnel study
• qz [kN/m²] is the velocity pressure at the reference height; in most wind tunnel studies this reference height corresponds to 10 m above ground;
in major wind loading codes such as EN 1991-1-1:2005 and ASCE 7-10 the velocity pressure is averaged over a duration of 3 seconds which is why
it is also referred to as gust pressure.
• SW is the partial (safety) factor or load factor according to the governing code
MODULE STRESS IN STOW POSITON
• Australian/ New Zealand Standard, AS/NZS 1170.2:2011 (R2016)
• Importance level 2
• Wind zone A4 (which represents most of the country in Australia)
• Terrain category 2
• Regional wind speed at 10 m height above ground V500 = 45 m/s
• Multipliers for terrain/ height, wind direction, shielding, and topography were
set to 1.0
• qz = 1.215 kN/m²
• Ultimate Limit States concept of AS/NZS 1170.0:2002 (SW=1.0)
• Spanish wind loading standard, UNE-EN 1991-1-4:2018
• Wind zone B (which represents most of the country in
Spain)
• Terrain category II
• vb,0=27 m/s (10 minute mean at 10 m height above
ground in terrain category II)
• Flat terrain
• qz = 1.072 kN/m²
• Ultimate Limit States concept of EN 1990 (SW=1.5)
MODULE STRESS IN STOW POSITON
• ASCE 7-16, the code addressing “Minimum design loads and associated
criteria for buildings and other structures”
• Risk Category II
• Basic wind speed of 115 mph or 51 m/s (which represents most of the
desert regions in the USA)
• Exposure C
• Wind directionality factor set to 0.85
• Velocity pressure exposure coefficient, topographic factor and ground
elevation factor were set to 1.0
• qz = 1.357 kN/m²
• Strength design (SW=1.0)
• At a 30° stow position, loads on modules are higher by a factor
of 1.8 compared with a 0° stow position.
• In outer zones and at 30° stow, design wind loading exceeds 2.4 kPa for all sample project
sites located in Australia, Spain and in the USA
• Generally speaking, the load bearing capacity of most modules corresponds to 2400 Pa
(for Uplift) if module rails in compliance with the manufacturer’s manual are used.
• However, for any deviation from the default mounting situation, e.g. if short module rails
or no module rails at all are present, the load bearing capacity may reduce to a range of
1400 Pa to 1800 Pa.
• Given these lower allowances for loads on PV modules, at some project sites stowing at
30° tilt may not be possible while stowing at 0° is.
MODULE STRESS IN STOW POSITON
https://www.pv-magazine.com/2018/12/26/filling-in-
the-microcracks/
STOWING STRATEGIES IN THE MARKET
The real benefit of 0° (flat) stow?
Less downtime / lower O&M costs Higher energy yields
www.ideematec.com 17
• Less stress on components
• Less stress on modules
• Less steel needed in installation
• Considerable BOS cost savings
• Higher efficiencies
• Safe positioning
• Less O&M costs
• New requirements:
-> larger modules
-> longer lifetime
Why 0° (flat) stow is the way forward?
0° single axis tracker – Based on a decoupled drive technology.
-> Avoids galloping and offers the most competitive and future-proof
solution for utility scale PV projects.
STOWING STRATEGIES IN THE MARKET
SAFETRACK HORIZON – OVERVIEW
• One Tracker: max. 6 tables
• One table: 30 m
• One tracker: max. 180 m length
• One tracker: one motorgearboxcontrolsensor
• 165 posts per MW
safeTrack Horizon
4 – 5 m span
SAFETRACK HORIZON – OUTSTANDING CONSTRUCTIVE FEATURES
• Decoupled drive system based on patented steel rope
technology
• Table fixation with ropes
• Geometry of rope system reduces forces
• High transmission between table and drive tube
• Patented self-adjusting-spring-system
• Load transfer by tension
• Ropes have a damping effect
• Unique technology such as in crane systems
safeTrack Horizon
SOLUTION - REDUCTION OF FORCES ON THE DRIVE TUBE
Ideematec‘s disconnected drive technology enables
the reduction of the forces on the drive tube:
-> to only 3.6 % of the forces acting on the table.
Winch
Roll pulley
Springs
SAFETRACK HORIZON – UNIQUE ROPE TECHNOLOGY
• Modules mounted
directly on drive tube
• Admission of the full table moment through
drive tube
• High risk of torsional galloping!
Standard „Torque Tube“ Tracker
• High winch ratio leads to less torsional moment
on driving tube!
• Winch transmission ratio is 1:28
• Low risk of torsional galloping!!!
IDEEMATEC safeTrack Horizon
SAFETRACK HORIZON – UNIQUE ROPE TECHNOLOGY
Gear transmission ratioTable : drive tube: = 1:1
IDEEMATEC safeTrack HorizonStandard „Tube“ Tracker
Gear transmission ratioTable : drive tube = 1:28 !!
• 100% of table loads go directly to the drive tube • Only 3,6% of table loads
occur on the drive tube
SOLUTION - HIGH NATURAL FREQUENCY AND DAMPING RATIO
• Ideematec‘s SafeTrack Horizon tracker comes with two
dampers on every post which gives a total of eight dampers
per table
• Since the critical wind speed for onset of aerodynamic
instability is significantly higher than the design wind speed,
wind-related failure cannot occur.
• Measurements were conducted on a REAL SYSTEM
• Stimulating the system to make torsional movement
• “Eigenfrequency” 2.5 Hz / damping ratio 15%
SOLUTION - HIGH NATURAL FREQUENCY AND DAMPING RATIO
HOW TO BEST SECURE YOUR PV PROJECT AGAINST HIGH WIND EVENTS
Ideematec‘s Safetrack Horizon system features
3 KEY DESIGN FACTORS to give it its high dynamic stability
-> 1: Reduction of forces on the drive tube
-> 2: High natural frequency
-> 3: High damping ratio
SAFETRACK HORIZON – UNIQUE ROPE TECHNOLOGY
Benefit of the unique rope design
→ Very low forces on gear box and tubes
→ high damping ratio and natural frequency
→ stiff table without axis flexibility
→ easy rotation impossible
→ flat table over whole 180m without
twists on the tracker ends
→ 0° position as stow position possible
STOW-POSITION at 0°
-> easy to define
-> easy to reach
SAFETRACK HORIZON – COMPARISON
0° STOW-POSITION
• no dependence on wind direction
• 360° safe protection – no safety gap
• lowest static forces on components
• lowest module stress
STOW-POSITION at inclination (30°-45°)
• Safety gap in case of changing wind direction
• If wind comes from the back the stability is worse compared
to 0° stow: VERY DANGEROUS!!!
• additional sensor for wind direction necessary
• higher static forces on components
• higher module stress
• more loss of energy if tracker moves to opposite direction of
the sun
Jordan, Quweira 100 MW
STOW ANALYSIS Conclusion
• The safest tilt angle for stow is 0° if combined with intelligent
load transmission or mechanical locking, high natural
frequency and high damping ratio.
• The 0° stow position leads to enormous material savings in
the structure and provides the best protection of photovoltaic
modules against damages such as micro cracks in cells as well
as back sheet and glass defects through sandblast abrasion.
• The 0° stow position is not vulnerable to changes of wind
direction as opposed to tracking systems which rely on stow
at a high tilt angle without being designed for the full
compass of wind direction.
sbp sonne works on increasing the use of renewable energy sources since 1985.
Solar experience:
25 countries and on 4 continents.Commercial Photovoltaic >10 000 MWCommercial CSP > 2 450 MWCommercial CSP technology prov. > 700 MW
sbp sonne numbers:
Founded / spin off 2009
Annual Turn Over ´17 4.2 Mio€Staff (Dipl. Ing/Masters 13, PhD 5 ) 20
Consulting engineers forrenewable energy
sbps reference / numbers
sbp sonne designs and optimizes solar applications:
Photovoltaic systems• fixed tilt, • one and two axis tracking, • building integrated photovoltaics (BIPV), • we further develop Argi PV and Floating PV systems.
Dish-Stirling systems, Central receiver systems, Parabolic trough and the solar updraft tower technology are the large scale Concentrated solar power applications.
Our highly qualified, motivated and constantly growing team is willing to contribute in research and development of any kind of technologies.
Consulting engineers forrenewable energy
Know How
Technical Expertise
Structural Engineering
Mechanical Engineering • Drives• Thermodynamics
Electrical & Cabling Engineering • Control system • PV solar field
Series Production/Automotive mass manufacturing
Software Development • Energy output optimization• FEM• Optics & solar tracking
Meteorology • Solar Radiation and Wind statistics
Consulting engineers forrenewable energy
Technical Ideematec - check
sbps check of IdeematecH4 and H4 plus
Innovative cable gear on each post ensures:
• SafeTracker enables that the torsional moments are largely derived directly to posts (without having to take the soft load path to the drive via a long torsion tube)
• Result in a high torsional stiffness, preventing most aerodynamic instabilities (divergence)
• The high natural frequency that can be achieved and the good damping properties also reduce the susceptibility to other forms of aerodynamic instability and thus allow a zero-degree stow strategy without excessive rocking.
• With the zero-degree Stow Strategy, Ideematec is on the right path to reduce costs and further technological developments in this direction are on the way - watch this space!
INNOVATION LEADING TECHNOLOGIES
PREVIEW – TO BE ANOUNCED SOON:IDEEMATEC’S STATE OF THE ART TRACKING SYSTEM
• Decoupled drive system
• Permanently locked
• Fixed tilt with tracking function
SAFETRACK HORIZON – AUSTRALIA, LIMONDALE – 349 MW
SOURCE: https://www.group.rwe/en/our-portfolio/innovation-and-technology/project-proposals/construction-projects-renewables/limondale-solar-plant
SAFETRACK HORIZON – JORDAN, BAYNOUNA – 250 MW
SAFETRACK HORIZON – SPAIN, TENDEIROS – 50 MW
SAFETRACK HORIZON – VIETNAM, HADO – 50 MW
&
STAY SAFE & THANK YOU FOR JOINING OUR WEBINAR