IEC TS 62727:2012

IEC/TS 62727 ®
Edition 1.0 2012-05
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic systems – Specifications for solar trackers

IEC/TS 62727:2012(E)
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IEC/TS 62727 ®
Edition 1.0 2012-05
TECHNICAL
SPECIFICATION
colour
inside
Photovoltaic systems – Specifications for solar trackers

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
U
ICS 27.160 ISBN 978-2-83220-122-0

– 2 – TS 62727 © IEC:2012(E)
CONTENTS
FOREWORD . 5
1 Scope and object . 7
2 Terms and definitions . 7
2.1 Photovoltaics (PV) . 7
2.2 Concentrating photovoltaics (CPV) . 7
2.3 Concentrator module (CPV module) . 7
2.4 Concentrator assembly . 8
3 Specifications for solar trackers for PV applications . 8
3.1 Specification template . 8
4 Tracker definitions and taxonomy . 10
4.1 General . 10
4.2 Payload types . 10
4.2.1 Standard photovoltaic (PV) module trackers . 10
4.2.2 Concentrated photovoltaic (CPV) module trackers . 11
4.3 Rotational axes . 11
4.3.1 Single axis trackers . 11
4.3.2 Dual axis trackers . 12
4.4 Actuation and control . 14
4.4.1 Architecture . 14
4.4.2 Drive types . 14
4.5 Types of tracker control . 15
4.5.1 Passive control . 15
4.5.2 Active control. 15
4.5.3 Backtracking . 15
4.6 Structural characteristics . 16
4.6.1 Vertical supports. 16
4.6.2 Foundation types . 16
4.6.3 Tracker positions . 17
4.6.4 Stow time . 17
4.7 Energy consumption . 17
4.7.1 Daily energy consumption . 17
4.7.2 Stow energy consumption . 18
4.8 External elements and interfaces . 18
4.8.1 Foundation . 18
4.8.2 Foundation interface . 18
4.8.3 Payload . 18
4.8.4 Payload interface . 18
4.8.5 Payload mechanical interface . 18
4.8.6 Payload electrical interface . 18
4.8.7 Grounding interface . 18
4.8.8 Installation effort . 18
4.8.9 Control interface . 19
4.9 Internal tolerances . 19
4.9.1 Primary axis tolerance . 19
4.9.2 Secondary axis tolerance . 20
4.10 Tracker system elements . 20

TS 62727 © IEC:2012(E) – 3 –
4.10.1 Mechanical structure . 20
4.10.2 Tracker controller . 20
4.10.3 Sensors . 20
4.11 Reliability terminology . 20
4.11.1 Mean time between failures (MTBF) . 20
4.11.2 Mean time between critical failures (MTBCF) . 21
4.11.3 Mean time to repair (MTTR) . 21
4.12 Environmental conditions . 21
4.12.1 Operating temperature range . 21
4.12.2 Survival temperature range . 21
4.12.3 Maximum wind during operation . 21
4.12.4 Maximum wind during stow . 21
4.12.5 Snow load . 21
4.13 Functional tests . 22
4.13.1 Static load test . 22
4.13.2 Moment testing . 22
4.13.3 Limit switch operation . 22
4.13.4 Manual operation . 22
5 Tracker accuracy characterization . 22
5.1 Overview . 22
5.2 Pointing error (instantaneous) . 22
5.3 Measurement . 23
5.3.1 Overview . 23
5.3.2 Example of experimental method to measure pointing error . 23
5.3.3 Calibration of pointing error measurement tool . 24
5.4 Calculation of tracker accuracy . 24
5.4.1 Overview . 24
5.4.2 Data collection . 25
5.4.3 Data binning by wind speed . 25
5.4.4 Data filtering . 26
5.4.5 Data quantity . 26
5.4.6 Accuracy calculations . 26
6 Mechanical characterization . 27
6.1 General . 27
6.2 Backlash . 27
6.3 Stiffness . 27
7 Reliability testing . 28
7.1 Corrosion . 28
7.2 Component durability. 28
7.3 Extreme conditions tests . 28
8 Additional optional accuracy calculations . 28
8.1 Typical tracking accuracy range . 28
8.2 Tracking error histogram . 29
8.3 Percent of available irradiance as a function of pointing error . 29

Figure 1 – θ = Altitude angle = 0° (zenith angle = 90°) occurs when a vector normal to
the module face is pointing to the horizon. Altitude angle = 90° (zenith angle = 0°)
occurs when the module is facing the sky . 13
Figure 2 – Illustration of primary axis tolerance for a polar tracking axis . 19

– 4 – TS 62727 © IEC:2012(E)
Figure 3 – General illustration of pointing error . 23
Figure 4 – Two flat parallel plates at a specified distance, one having a pin hole for
sunlight to be tracked on specified-diameter circles that ultimately measure 0,1°, 0,2°,
and 0,3° accuracy rings (more if necessary) . 24
Figure 5 – Pointing error frequency distribution for the entire test period . 29
Figure 6 – Available irradiance as a function of pointing error . 30
Figure 7 – Available irradiance as a function of pointing error with binning by wind
speed . 30

Table 1 – Tracker specification template . 8
Table 2 – Alternate tracking accuracy reporting template . 27

TS 62727 © IEC:2012(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC SYSTEMS –
SPECIFICATIONS FOR SOLAR TRACKERS

FOREWORD
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The main task of IEC technical committees is to prepare International Standards. In
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• the required support cannot be obtained for the publication of an International Standard,
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• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62727, which is a technical specification, has been prepared by IEC technical committee 82:
Solar photovoltaic energy systems.

– 6 – TS 62727 © IEC:2012(E)
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/651/DTS 82/711/RVC
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
TS 62727 © IEC:2012(E) – 7 –
PHOTOVOLTAIC SYSTEMS –
SPECIFICATIONS FOR SOLAR TRACKERS

1 Scope and object
This technical specification provides guidelines for the parameters to be specified for solar
trackers for photovoltaic systems and provides recommendations for measurement
techniques. No attempt is made to determine pass/fail criteria for trackers.
The purpose of this test specification is to define the performance characteristics of trackers
and describe the methods to calculate and/or measure critical parameters.
This specification provides industry-wide definitions and parameters for solar trackers. Each
vendor can design, build, and specify the functionality and accuracy with uniform definition.
This allows consistency in specifying the requirements for purchasing, comparing the products
from different vendors, and verifying the quality of the products. In addition, this specification
will clarify terminology and definitions for trackers and provide examples of measurement
techniques.
This technical specification will be a foundation for other standards to follow, including (but
not limited to) design qualification and reliability.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply. For additional
tracker-specific terminology, see Clause 5.
2.1
photovoltaics
PV
devices that use solar radiation to generate electrical energy
2.2
concentrating photovoltaics
CPV
devices that focus magnified sunlight on photovoltaics to generate electrical energy. The
sunlight could be magnified by various different methods, such as reflective or refractive
optics, in dish, trough, lens, or other configurations.
2.3
concentrator module
CPV module
a group of receivers (PV cells mounted in some way), optics, and other related components,
such as interconnections and mechanical enclosures, integrated together into a modular
package. The module is typically assembled in a factory and shipped to an installation site to
be installed along with other modules on a solar tracker.
Note 1 to entry: A CPV module typically does not have a field-adjustable focus point. In addition, a module could
be made of several sub-modules. The sub-module is a smaller, modular portion of the full-size module, which might
be assembled into the full module either in a factory or in the field.

– 8 – TS 62727 © IEC:2012(E)
2.4
concentrator assembly
a concentrator assembly consists of receivers, optics, and other related components that have
a field-adjustable focus point and are typically assembled and aligned in field
EXAMPLE: A system that combines a single large dish with a receiver unit which must be
aligned with the focal point of the disk.
Note 1 to entry: This term is used to differentiate certain CPV designs from the CPV modules mentioned above.
3 Specifications for solar trackers for PV applications
a) Specification template
All trackers complying with this specification should provide, as part of their product marking
and documentation, a table in the form specified below (see Table 1). See later clauses and
subclauses of this Technical Specification for further explanation of individual specifications.
Some of the specifications within the table are optional; however, if a tracker manufacturer
chooses to include optional information, it should be reported and measured in the specific
way shown in Table 1 (and in some cases, also described later in this Technical
Specification).
Engineering safety factors should be dictated by appropriate local standards and applications
details and documented by the tracker manufacturer.
The specification template below is a visual example only and should not be read as a list of
requirements.
Table 1 – Tracker specification template
Characteristic Example Notes/Clause/Subclause
Manufacturer The XYZ Company
Model number XX1090
Type of tracker  CPV Tracker, Dual Axis 4.2, 4.3
Payload characteristics
Minimum/maximum mass 100/1 025 kg 4.8.3
supported
Payload center of mass 0-30 cm distance perpendicular to 4.8.3
restrictions mounting surface
Maximum dynamic torques Azimuth (Θ ): 10 kN⋅m 4.13.2, 7.3
z
allowed while moving
Θ , Θ : 5 kN⋅m
x y
[ should provide a set of diagrams to
clarify torques and which axes they
are relative to ]
Maximum static torques allowed [ should provide a set of diagrams ] 4.13.1, 7.3
while in stow position
Installation characteristics
Allowable foundation Reinforced concrete 4.6.2
Foundation tolerance in primary 4.9
± 0,5°
axis
Foundation tolerance in secondary ± 0,5° 4.9
axis
Electrical characteristics
Includes backup power? No N/A
TS 62727 © IEC:2012(E) – 9 –
Characteristic Example Notes/Clause/Subclause
Daily energy consumption 1 kWh typical 4.7.1
5 kWh maximum
Stow energy consumption kWh typical 4.7.2
1 kWh maximum
Input power requirements 100-240 VAC, 50-60 Hz, 5 A No specifics defined
Tracking accuracy
Accuracy, typical 0,1° 5.4.6
(low wind, min deflect point)
Accuracy, typical 0,3° 5.4.6
(low wind, max deflect point)
th
Accuracy, 95 percentile 0,5° 5.4.6
(low wind, min deflect point)
th
Accuracy, 95 percentile 0,8° 5.4.6
(low wind, max deflect point)
Mean wind speed during the “low 3 km/h 5.4.6
wind” test conditions
Accuracy, typical 0,7° 5.4.6
(high wind, min deflect point)
Accuracy, typical 1,0° 5.4.6
(high wind, max deflect point)
th
Accuracy, 95 percentile 1,1 5.4.6
(high wind, min deflect point)
th
Accuracy, 95 percentile 1,6° 5.4.6
(high wind, max deflect point)
Mean wind speed during the “high 12 km/h 5.4.6
wind” test conditions
Weight and area of payload 500 kg payload evenly distributed 5.4.2.1
installed during testing over a 50 m area
Payload center of mass installed Payload center of mass 20 cm above 5.4.2.1
during testing the module mounting surface
Control characteristics
Control algorithm Hybrid 4.5
Control interface None 4.8.9
External communication interface Ethernet/TCP-IP No specific description
Emergency stow provided? Yes, at wind speeds 100 km/h 4.6.4, 4.12.3
Stow time 4 minutes 4.6.4
Clock accuracy 1 second per year N/A
Mechanical design
Range of motion, primary axis ± 160° azimuth 4.6.3.3
Range of motion, secondary axis 10°-90° elevation 4.6.3.3
System stiffness Azimuth (Θ ): 0,05º / 1 000 N⋅m, Θ : 6.3
z x
0,1º / 1 000 N⋅m
Diagrams attached show applied
loads and observed deflection
Backlash 0,1° maximum 6.2
Environmental conditions
Maximum allowable wind speed Design values: 4.12.3

– 10 – TS 62727 © IEC:2012(E)
Characteristic Example Notes/Clause/Subclause
during tracking
80 km/h with 0 % terrain slope, open
country,
60 km/h with 8 % terrain slope,
suburban, urban
Tested to:
60 km/h with 0 % terrain slope, open
country
Maximum allowable wind speed in Design values: 4.12.4
stow
150 km/h horizontal wind,
120 km/h with 10 % slope
Tested to:
80 km/h with 0 % slope
Temperature operational range –20 °C to +50 °C 4.12.1
Temperature survival range –40 °C to +60 °C 4.12.2
Snow rating Up to 20 kg/m of snow load allowed 4.12.5

For an alternate template for the presentation of accuracy specifications see Table 2.
4 Tracker definitions and taxonomy
4.1 General
Solar trackers are mechanical devices used to point PV modules towards the sun or to direct
sunlight on PV cells or modules. Photovoltaic trackers can be classified into two types:
standard photovoltaic (PV) trackers and concentrated photovoltaic (CPV) trackers. Each of
these tracker types can be further categorized by the number and orientation of their axes,
their actuation architecture and drive type, their intended applications, and their vertical
supports and foundation type.
4.2 Payload types
4.2.1 Standard photovoltaic (PV) module trackers
4.2.1.1 Uses
Standard photovoltaic trackers are used to minimize the angle of incidence between incoming
light and a photovoltaic module. This increases the amount of energy produced from a fixed
amount of power generating capacity.
4.2.1.2 Type of light accepted
Photovoltaic modules accept both direct and diffuse light from all angles. This means that
systems implementing standard photovoltaic trackers produce energy even when not directly
pointed at the sun. Tracking in standard photovoltaic systems is used to increase the amount
of energy produced by the direct component of the incoming light.
4.2.1.3 Accuracy requirements
In standard photovoltaic systems, the energy contributed by the direct beam drops off with the
cosine of the angle between the incoming light and the module. Thus trackers that have
accuracies of ± 5° can deliver more than 99,6 % of the energy supplied by the direct beam. As
a result, high-accuracy tracking is not typically used.

TS 62727 © IEC:2012(E) – 11 –
4.2.2 Concentrated photovoltaic (CPV) module trackers
4.2.2.1 Uses
Concentrated photovoltaic trackers are used to enable the optics used in CPV systems. These
trackers point the concentrator modules at the sun or focus sunlight on PV collectors.
4.2.2.2 Type of light accepted
Direct solar radiation, as opposed to diffuse solar radiation, is the primary energy source for
CPV modules. Optics are designed specifically to focus the direct radiation on photovoltaic
cells. If this focus is not maintained, power output drops substantially.
If the CPV module concentrates in one dimension, then single axis tracking is required. If the
CPV module concentrates in two dimensions, then two axis tracking is required.
4.2.2.3 Accuracy requirements
In concentrator modules, tracking accuracy requirements are typically related to energy
production through the module acceptance angle. When the sun-pointing error is less than the
acceptance angle, the modules will typically deliver 90 % or more of the rated power output.
4.3 Rotational axes
4.3.1 General
Photovoltaic trackers can be grouped into classes by the number and orientation of the
tracker’s axes.
4.3.2 Single axis trackers
4.3.2.1 General
Single axis trackers have one degree of freedom that acts as an axis of rotation.
4.3.2.2 Single axis tracker implementations
4.3.2.2.1 General
There are several common implementations of single axis trackers. These include horizontal
single axis trackers, vertical single axis trackers, and tilted single axis trackers.
4.3.2.2.2 Horizontal single axis tracker (HSAT)
The axis of rotation for a horizontal single axis tracker is horizontal with respect to the ground.
IEC  1028/12
4.3.2.2.3 Vertical single axis tracker (VSAT)
The axis of rotation for vertical single axis trackers is vertical with respect to the ground.
These trackers rotate from east to west over the course of the day.

– 12 – TS 62727 © IEC:2012(E)
IEC  1029 /12
4.3.2.2.4 Tilted single axis tracker (TSAT)
All trackers with axes of rotation between horizontal and vertical are considered tilted single
axis trackers. Tracker tilt angles are often limited to reduce the wind profile and decrease the
elevated end’s height off the ground.
The polar aligned single axis tracker (PASAT) is a specific version of the tilted single axis
tracker. In this particular implementation, the tilt angle is equal to the latitude of the
installation. This aligns the tracker’s axis of rotation with the earth’s axis of rotation.
IEC  1030/12
4.3.2.3 Orientation – cardinal direction
The axis of rotation of single axis trackers is typically aligned along a true North meridian. It is
possible to align them in any cardinal direction with advanced tracking algorithms.
4.3.2.4 Module orientation with respect to rotational axis
The orientation of the module with respect to the tracker axis is important when modelling
performance.
Horizontal and tilted single axis trackers typically have the face of the module oriented
parallel to the axis of rotation. As a module tracks, it sweeps a cylinder that is rotationally
symmetric around the axis of rotation.
Vertical single axis trackers typically have the face of the module oriented at an angle with
respect to the axis of rotation. As a module tracks, it sweeps a cone that is rotationally
symmetric around the axis of rotation.
4.3.3 Dual axis trackers
4.3.3.1 General
Dual axis trackers have two degrees of freedom that act as axes of rotation. These axes are
typically normal to one another. The axis that is fixed with respect to the ground can be
considered the primary axis. The axis that is referenced to the primary axis can be considered
the secondary axis.
TS 62727 © IEC:2012(E) – 13 –
4.3.3.2 Dual axis tracker implementations
4.3.3.2.1 General
There are several common implementations of dual axis trackers. They are classified by the
orientation of their primary axes with respect to the ground. Two common implementations are
tip-tilt trackers and azimuth-altitude trackers (see Figure 1).
One convention for azimuth angle is “degrees east of north” (e.g. 0° azimuth is pointing north,
and 90° azimuth is pointing east).
One convention for altitude angle is “degrees up from the horizon” as illustrated below. Zenith
angle is the complement of altitude angle (zenith = 90° – altitude).
θθ = 0 = °
θ = 90°
θ =
IEC  1031/12
Figure 1 – θ = Altitude angle = 0° (zenith angle = 90°) occurs
when a vector normal to the module face is pointing to the horizon.
Altitude angle = 90° (zenith angle = 0°) occurs
when the module is facing the sky
The above sign conventions are assumed to be the ones used to describe angles, but a
different convention can be used as long as it is described. For example, the range of motion
of a tracker could be described as “azimuth from +20° to +340°,” or alternately, “azimuth
± 160° from south”.
4.3.3.2.2 Tip-tilt dual axis tracker
A tip- tilt dual axis tracker (TTDAT) has its primary axis horizontal to the ground. The
secondary axis is then typically normal to the primary axis.
The polar-style dual axis tracker is a particular type of TTDAT.
IEC  1032/12
– 14 – TS 62727 © IEC:2012(E)
4.3.3.2.3 Azimuth-altitude dual axis tracker
An azimuth-altitude dual axis tracker (AADAT) has its primary axis vertical to the ground. The
secondary axis is then typically normal to the primary axis.
IEC  1033/12
4.3.3.3 Orientation – cardinal direction
The axes of rotation of tip-tilt dual axis trackers are typically aligned either along a true north
meridian or an east-west line of latitude. It is possible to align them in any cardinal direction
with advanced tracking algorithms.
4.3.3.4 Module orientation with respect to rotational axes
The orientation of the module with respect to the tracker axis is important when modelling
performance. Dual axis trackers typically have modules oriented parallel to the secondary axis
of rotation.
4.4 Actuation and control
4.4.1 Architecture
4.4.1.1 General
There are two common actuation and control architectures: distributed actuation and ganged
actuation. These are implemented in many ways.
4.4.1.2 Distributed actuation
In a distributed actuation architecture, each tracker and each axis of rotation is independently
actuated and controlled.
4.4.1.3 Ganged actuation
In a ganged actuation architecture, many axes of rotation are simultaneously driven with a
single actuation system. This can be multiple axes on a single tracker or multiple trackers in
an array.
4.4.2 Drive types
4.4.2.1 General
There are three drive types used with solar trackers.
4.4.2.2 Electric drive
Electric drive systems transfer electrical energy to AC motors, DC brushed motors, or DC
brushless motors to create rotational motion. These motors interface with gearboxes that
reduce the rotational speed in exchange for additional torque. The final gearbox stage
delivers either rotary or linear motion that is used to drive a tracker axis.

TS 62727 © IEC:2012(E) – 15 –
4.4.2.3 Hydraulic drive
Hydraulic drive systems use pumps to generate hydraulic pressure. The hydraulic pressure is
transferred through valves, pipes, and hoses to a hydraulic motor or cylinder. The hydraulic
motor and cylinder adjust the mechanical advantage as needed to deliver the rotary or linear
motion to drive a tracker axis.
4.4.2.4 Passive drive
Passive drive systems use differential fluid pressure to drive a tracker axis. The pressure
differential is created by thermal gradients created by differential shading. The tracker moves
to bring the pressure differentials to equilibrium.
4.5 Types of tracker control
4.5.1 Passive control
Passive solar tracking typically relies on environmental forces to produce changes in fluid
density, which provide internal forces that can be used for mechanical advantage to position
the payload.
4.5.2 Active control
4.5.2.1 General
Active solar tracking uses supplied power to drive circuitry and actuators (motors, hydraulics,
and others) to position the payload.
4.5.2.2 Open loop control
Open loop control is an active method of tracking that does not use direct sensing of the sun
position, module power, et cetera as feedback. It uses mathematical calculations of the sun
position (based on the time of day, date, location, and so on) to determine where the tracker
should be pointing and drives actuators accordingly.
Note that open loop control in this context does not imply that the actuators themselves do not
provide feedback; the actuators could be servo motors with encoders and could themselves
be controlled via a closed-loop PID or similar controller.
Open loop in the context of tracker control refers to the control algorithm having no direct
feedback on the actual tracking error.
4.5.2.3 Closed loop control
This is an active method of tracking that utilizes some sort of feedback (such as an optical
sun position sensor or the module power output) to determine how to drive the actuators and
position the payload.
4.5.2.4 Hybrid control
This is an active method of tracking that combines the mathematical sun position calculations
(open loop ephemeris code) with the type of sensor data used in a closed feedback loop.
There are many different approaches to hybrid control.
4.5.3 Backtracking
Backtracking refers to intentionally positioning trackers somewhat off-sun, typically to reduce
shading from adjacent trackers in a close-packed installation during the early morning and
late afternoon when the sun is low on the horizon.

– 16 – TS 62727 © IEC:2012(E)
One method involves moving all the trackers in a field to a slightly higher elevation angle to
avoid shading. Another approach is for every other row to be inactive and positioned at 0°
(pointing at the sky) to allow the other rows clear line-of-sight to the sun without shading. This
is useful mainly in designs that do not have access to enough land area to be spaced far
enough apart to avoid shading in the early morning and late afternoon. Backtracking is
typically not applicable to CPV.
4.6 Structural characteristics
4.6.1 Vertical supports
4.6.1.1 General
Vertical supports transfer the load of the structure to the foundation. There are two common
types of vertical supports.
4.6.1.2 Pole-mounted trackers
A pole-mounted tracker transfers the load to the foundation via one or more poles. These
poles attach to or continue into one or more foundations.
All types of trackers (single axis and dual axis) can be mounted on poles.
4.6.1.3 Carousel-mounted trackers
A carousel-mounted tracker transfers the load to the foundation via a ring. This ring is then
attached to the foundation at multiple points.
Vertical single axis trackers and azimuth-altitude dual axis trackers are the only trackers that
can be carousel mounted.
4.6.2 Foundation types
4.6.2.1 General
The load placed on the tracker structure shall be sustained through its foundation.
Trackers can be mounted on roofs, ground/earth, and water and will be subject to location-
specific loading. As a result, there are many types of foundations used with trackers. The
foundation type used will depend on site-specific characteristics and the codes of the local
jurisdiction.
Foundation types are often categorized by whether or not they penetrate into the mounting
surface.
4.6.2.2 Penetrating foundations
4.6.2.2.1 Pile foundations
Pile foundations (also known as deep foundations) come in a wide variety of types. These
include but are not limited to concrete piles, driven piles, and drilled piles.
Pile foundations are common in ground-mounted and water-mounted applications. Hole
diameters, depth, concrete mixtures, rebar requirements, thread type, and other
characteristics are all determined by local site conditions.

TS 62727 © IEC:2012(E) – 17 –
4.6.2.3 Non-penetrating foundations
4.6.2.3.1 Ballasted foundations
Ballasted foundations (also known as shallow foundations) come in a wide variety of types.
Ballasted foundations are found in ground mount and roof mount applications. The area in
contact with the surface, total mass, material type, rebar requirements, and other
characteristics are all determined by local site conditions.
4.6.3 Tracker positions
4.6.3.1 Stow
The stow position is the position the tracker moves to when adverse weather conditions (e.g.,
high wind or heavy snow) are present or expected in order to avoid loads that might damage
the tracker or payload. Not all trackers will have a stow position, and the exact position will
vary depending on the tracker design.
4.6.3.2 Maintenance
The maintenance position is the position the tracker moves to for operations such as cleaning,
module installation, servicing, and so on. It could be the same position as the stow position or
a different position, and there could be multiple maintenance positions. When in this position,
there should be a safety interlock preventing sudden tracker motion without operator
interaction.
4.6.3.3 Range of motion
The range of motion is defined by the maximum motion of the tracker in each direction, in
each axis.
For example, a turret-style primary axis might have a range of motion of ± 135° from true
south [or in the reference frames defined above, +45° to +315° azimuth (east of north)]. An
elevation-style secondary axis might have a range of motion of 0° to 90°.
The range of motion specified in the requirements of Table 1 shall be tested and documented.
Note that the range of motion is not only defined by any mechanical limits: the presence of
electronic limit switches or software settings may be used to further restrict the range of
motion for reasons such as safety or reduction of shading.
If the tracker includes a controller, the range of motion should refer to the maximum range of
motion that can be commanded by the combination of hardware and software.
4.6.4 Stow time
The stow time is the time for the tracker with a standard payload to move from the position
farthest from the stow position to the stow position.
4.7 Energy consumption
4.7.1 Daily energy consumption
The daily energy consumption of a tracker is defined as the amount of energy in kWh that is
required to perform a full 24 h day of tracking (from start to stop at a typical tracking speed
and back to start by whatever speed is standard for that tracker) carrying a standard load.
The energy consumption will likely vary based on the wind loading and possibly also on cloud
cover and other weather conditions. The energy consumption
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