Amit Nirmal |
Sterling Strips LtdSterling Strips Ltd is a is a multi-disciplinmulti-disciplineded
E.P.C, planning, design and engineering E.P.C, planning, design and engineering
company providing comprehensive services company providing comprehensive services
Boiler Design, Manufacturing Boiler Design, Manufacturing & Commissioning& Commissioning
Solar PV Structural EPCSolar PV Structural EPC
Turnkey ProjectsTurnkey Projects
Shirsh EnergyShirsh Energy is a system is a system Integrator for SolarIntegrator for Solar
Rooftop and other services on turnkey basis. Rooftop and other services on turnkey basis.
Sterling Strips LtdSterling Strips Ltd is a is a multi-disciplinmulti-disciplineded
E.P.C, planning, design and engineering E.P.C, planning, design and engineering
company providing comprehensive services company providing comprehensive services
Boiler Design, Manufacturing Boiler Design, Manufacturing & Commissioning& Commissioning
Solar PV Structural EPCSolar PV Structural EPC
Turnkey ProjectsTurnkey Projects
Shirsh EnergyShirsh Energy is a system is a system Integrator for SolarIntegrator for Solar
Rooftop and other services on turnkey basis. Rooftop and other services on turnkey basis.
PV array mounting optionsPV array mounting options
Engineering variables for designing theEngineering variables for designing the
mounting system mounting system
Design methodology for Mounting structuresDesign methodology for Mounting structures
Construction MethodologyConstruction Methodology
Installation OverviewInstallation Overview
Photovoltaic module mounting systems arePhotovoltaic module mounting systems are
one piece of a solar electric project that one piece of a solar electric project that
generally does not receive a lot of attention generally does not receive a lot of attention
But a mounting system is an importantBut a mounting system is an important
component that shouldn’t be
Ground Mounting Ground Mounting Roof-top Mounting
Top-Down Rail System
Rack Mounts: Adjustable- & Fixed-Tilt Top-of-Pole Mounts
Commercial mounting systems Tracking System
Single Axis Dual Axis
One of the most common
and very popular PV module mounting methods is the
“top-down” rail system,
since modules attach from their upper side to the rails with specified clamps.
This versatile system can be
used with almost all roofing types.
Top-down rail mounts are popular in both home and business scale
It consist of 4 main
component
Feet or posts (also called
“footings” or “stand-offs”) that are typically secured to the roof’s rafter system;
Extruded aluminium
rails fastened to the feet or posts and the array;
End-clips that secure the
ends of the PV array to the rails;
Mid-clips that hold the
junction of two modules
Array is mounted
parallel to the roof plane
PV modules are
attached to the
rails from the front side, instead of the back
Rail systems typically result in only 3 to 6 inches of space between the back of the modules and the roof surface.
Rack mounts can be tailored to fit a variety of
situations, accommodating both ground mount and roof-mount applications.
Biggest benefit to racks is that they can allow
for a variety of specific tilt angles.
The PV array can be set at an optimal tilt
angle based on the site’s latitude or, if
adjustable racks are chosen, repositioned seasonally to optimize energy output.
Main Components : legs, beams & Clamps for
Since these mounts tilt the array away from
the mounting surface, the backs of the modules can usually be conveniently accessed to get to
the wiring, junction boxes, and grounding
points, making installation and maintenance easier.
The increased distance from the mounting
surface also facilitates greater airflow along the back of the modules and results in a lower array temperatures compared to the parallel-to-roof method.
Same structure can be used for Ground
Mounted or Roof mounted in some situations it can be used on side of buildings.
Many designs require ordering a specific rack with mounting hole spacing that matches the PV module’s mounting holes. In roof mounted systems, rack mounts have less layout flexibility than top-down rail systems.
The top-of-pole
mounting solution is a favourite among many installers
Top-of-pole arrays are
viable for locations with enough land space and where possible
aesthetic concerns are not an issue.
The footing for the pole is encased in
concrete according to manufacturer’s
specifications for the array size and the site’s soil and wind-loading conditions.
Components
•Pole
•mounting sleeve which slips on top of the pole
•All necessary bracing and cross members, as well as
The ability to adjust the array tilt seasonally
is a natural function of any top-of-pole mount.
In cold climates, top-of-pole mounts are one
of the most convenient racking options if snow needs to be periodically cleared from the array.
Top of-pole arrays can also be used with
tracker systems to help boost PV production even more
Array sits several feet from the ground,
allowing for the greatest amount of airflow, top-of-pole mounted arrays operate at lower temperatures than roof- and
ground-mounted arrays.
This reduces the amount o power lost when
Top-of-pole mounts generally are not viable
options in urban or suburban areas due to the yard space required.
Additional excavation required to place a pole
and trench to the electrical distribution can make top-of-pole mounts more costly in
These solutions include
Custom designed and
fabricated mounting structures,
Integrating the PV array
into the roofing material, and using a
Non penetrating ballast
system for flat-roof applications.
Ballast mounts rely on the weight of the ballast, modules, and racking rather than fasteners and roof penetrations to secure the array.
The most common
type of commercial racking system is the ballast rack, which
uses the weight of the modules and rack in conjunction with
ballast to securely keep the arrays in place.
Masonry blocks are placed in
ballast pans that are located
either directly under, or in front of and behind the PV array
These racks can add a significant
roof load, up to 146.47 Kg per
square meter, depending on the array engineering requirements.
Single Axis Tracker system
Trackers are used to minimize the angle of incidence
between the incoming light and a photovoltaic panel.
The single-axis method follows the sun’s path
from east to west, with the array tilted at a fixed or manually adjustable angle off the horizon.
This approach is common in large-scale,
commercial installations but can be used in residential applications as well.
Dual-axis trackers adjust the PV array to track
the sun’s path from east to west and adjust the array’s tilt to account for the change in the sun’s altitude.
1. Maximum design wind speed. 2. Snow Load
3. Exposure category. 4. Soil class.
5. Module type and quantity. 6. Desired tilt angle.
7. Ground clearance.
This is the highest wind gust speed probable
in 50 years, averaged over a 3-second gust at a height of 10 metre. Refer IS 875 for info.
Because wind speeds vary (they are generally
higher close to the coast and at high
elevations), this is critical information for an engineer
Maximum design wind speeds can be found
deals with wind loads to be considered when designing buildings,
Location ( this determines basic wind speed) Calculate design wind speed
Calculate Design
By Conducting FEA for structures we can
Approximately know the reaction forces which
will be responsible for uplift of structure
Stresses in each members, that then can be
compared with IS 875, IS800 andIS801 for
validation
Overall displacement and pinpoints exactly where
we have focus for optimizing the structure
Can be used for studying combinations of Wind,
A good PV mounting system must be capable of one thing above all: It must stand safely.
Measured in pounds per square foot (or
Kg/m2), the weight of snow on a structure can stack up, depending on your location.
Snow can be five to more than 15 times
heavier than a PV module, and the rack must hold the additional weight.
ASCE (American Society of Civil Engineer)
Standard 7-10 includes common snow-load values
This is related to wind loading and takes into
account the turbulence at the site due to surrounding objects (trees, buildings, etc.).
Terrain in which a specific structure stands
shall be assessed from IS 875 section 3, typically there are 4 categories of terrain.
This is necessary for determining specifics for
anchors, which behave differently in different soils.
Soil test report is necessary in determining
the anchoring which can Ramming or Piling
Soil report typically consists of Safe Bearing
Capacity, Moisture Content, Cohesion Value of soil to hold the structure etc.
Acquire a specification sheet for your
modules for the rack manufacturer, who will need at least
minimum the number of modules, plus module depth, height,
This will be based on your location’s latitude
and the seasonal variation in solar gain
The height to the lower edge of the first row
of modules (800mm to 1000mm is typical).
This basic design decision should be based on site conditions:
potential snow accumulation, ground covering ( accessibility) aesthetics, etc.
This information can help the rack
manufacturer design an efficient layout, with strings contained within a row or sub array for less trenching and conduit.
Preliminary
Sitting: Review property lines, shading, setbacks,
right-of-ways, or easements; and check for underground utilities.
Civil engineering: Will grading, storm water runoff
mitigation, or environmental reviews be needed? Check with local permitting, planning, and inspection agencies.
Site access: Is the site accessible to heavy construction
machinery if needed?
Accessibility: Will the array need fencing for security from
theft and/or animals, and to comply with Standards ?
Be sure there is sufficient space so the fence will not shade
Design
Site-specific info: Catalogue wind speed, snow loads,
soil conditions, etc.
Electrical interconnection: Determine distance and
route to the interconnection point, and placement of electrical equipment including combiner boxes,
disconnects, inverters, and other BOS components.
Orientation Height
Layout
Columns : Can be hot rolled or Cold Rolled
section
Link or Brackets : Preferably Cold rolled as
good strength and weight factor
Link can tilting also for having seasonal tilt in
zenith
Beams: Preferably Cold rolled as good
strength and weight factor
This code applies to general construction in
steel
The provisions of this code generally .apply to
riveted, bolted and welded constructions, using hot rolled steel sections.
This code gives only general guidance as
regards the various loads to be considered in design , For actual loads to be used reference may be made to IS : 875
This code applies to the design of structural
members cold-formed to shape from carbon or low-alloy, sheet or strip steels used for load carrying purposes in buildings.
It may also be used for structures, other than
building provided appropriate allowances are made for dynamic effects.
Hot dip Galvanized Steel or Aluminum for on
grid mounting structures
Aluminum / Galvanized Steel or Stainless
Steel in Off grid installations.
Fasteners : All Stainless Steel preferred
Galvanization : Upto 80-90 Microns but will
depend upon the soil and Chloride , moisture content of soil & Ph Value of soil.
Surface preparation
Caustic cleaning- A hot alkali solution often is used to
remove organic contaminants such as dirt, paint markings, grease and oil from the metal surface.
Acid pickling- Scale and rust normally are removed
from the steel surface by pickling in a dilute solution of hot sulphuric acid
Fluxing- Fluxing removes oxides and prevents further
oxides from forming on the surface of the metal prior to galvanizing.
Galvanizing- the material is completely immersed in a bath
consisting of a minimum of 98% pure molten zinc.
Fabricated items are immersed in the bath until
Inspection
coating thickness and coating appearance
A variety of simple
physical and laboratory tests may be performed to determine thickness, uniformity, adherence and appearance.
Structures are modularly constructed into
different parts and installed on site using fasteners.
Cold Rolling methodology is used in making
brackets, beams and struts.
Hot rolled or cold rolled can be used in
Marking of Site as per layout for pole
mounting
Ramming or Piling of Poles / Post or Column Checking Alignment of Poles
Mounting of brackets
Mounting of Aligner (Tilting link) Mounting of Beams
Mounting of Struts
Mounting of Panels and supporting it with
