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What is Photovoltaics?

pv support system

How does photovoltaics works?

Photovoltaics is the process of generating electricity by conversion of solar radiation energy that is free. Photovoltaic cells are semiconductor elements conducting electrical charges, with their construction usually based on silicon (Si). The difference in electrical potentials occurring under the influence of incident light on this element contributes to generation of the electric current.

In order to produce more power, photovoltaic cells are connected into panels, i.e. a group of modules supplying one inverter, which converts direct current from the panels into alternating current used in the public grid. This means that the device continuously adjusts the parameters of the generated current to the parameters of the home network and also switches off when any failure is detected. It also monitors any parameters that may be useful for analyzing the performance of photovoltaics. 

What are the components of a photovoltaic (PV) system?

A complete system of photovoltaic installations includes: 

  • panels, 
  • inverter,
  • bi-directional electricity meter (electricity consumed/exported to the grid),
  • automation systems that ensure that the panels are properly loaded with the current,
  • batteries - additional power.  
  • mounting system - support structure. 

Installation of photovoltaic panels:

For a system powered by the sunlight, you can decide to install the components on the roof or the ground around the house. An important aspect is the proper choice of location. The amount of energy produced is strictly dependent on the orientation towards the sun. When choosing the location, one should follow several basic requirements:

  • The most sunlit direction is the south, so panels should be positioned towards the south. This is the optimum arrangement of the modules to ensure that the highest levels of current generation. A certain deviation to the west or east is also acceptable, positioning the panels towards the north or in the shaded area makes no sense.
  • The location of the installation can be far from the buildings of the target energy supply, as the cables in such installations can be distributed over any length, although in order to avoid energy losses, the cross-section of the cables should be increased.
  • The amount of electricity supplied by the installations is also highly dependent on the angle of inclination of the photovoltaic modules. This is largely due to the fact that the angle of incidence of the sun is not constant. In summer it is much higher above the horizon than in winter. The optimum position of the modules should be at an angle of 30-35◦ to the ground. In this position, the generation of electric energy from the installed power will be the highest. When the modules are placed on a flat roof or on the ground, the required angle is achieved by using a suitable supporting structure.
  • Factors such as wind (from which side it blows most often) or snow (in which part of the roof is most often overlaid) should also be taken into account. This refers to considerations for the fixing structure.
  • Do not install more photovoltaic panels than necessary, due to the risk that more energy will be fed into the network than we use.
  • Photovoltaic panels may overheat. Therefore, they must be installed so that they have adequate air supply and flow from all sides.

How are solar panels mounted?

The element that enables the panels to be mounted on the ground or building is a supporting structure, which at the same time is to ensure the stability of the whole system. Installation on the roof requires specifying the type of roofing cover and shape of the roof, whether it is flat, sloping or trapezoidal. The STRUT mounting system is recommended for the installation of any number of photovoltaic panels in a flat system.

PV mounting system

Note: Remember to select the appropriate surface category to choose a compatible mounting system.

After selecting the right components of the photovoltaic system, the assembly involves the following stages:

A special rack should be mounted on the roof or ground. It consists of mounting rails and mounting profiles. As an additional supporting element of the system one can use the roof feet and brackets, ST-ROF-330 and ST-ROF-AW-330 respectively, which provide better weight distribution of elements mounted on the roof, keeping the roofing structure intact and easy access to the roof surface without disassembling the previously installed components. The profiles are connected with screws and mounting accessories (see. below). 
strut channel for solar panels
On the prepared frame, photovoltaic panels are arranged in series and connected to the inverter.

Dense profile perforation allows for a wide range of position adjustment without drilling or welding.

  • Longitudinal profile perforation enables smooth adjustment of the angle of inclination of the structure.
  • The perforation of profiles also reduces the weight of the structure without reducing its strength. With this solution fitters do not have to carry heavy profiles and their work is more efficient.
  • It is possible to make assembly structures from different materials depending on the application.
  • STRUT mounting profiles are manufactured on top-class machines, which ensure high quality of products.
  • Profiles made of sheet metal with a hot-dip zinc coating guarantee long-term resistance to corrosion in various atmospheric conditions.
  • All STRUT mounting profiles are manufactured in Poland!

STRUT channel support system:

Discover the Alnor range, which will enables you to quickly install photovoltaic systems. Elements of the STRUT system are made of ordinary steel, carbon steel or structural steel and are protected against corrosion with Z100 zinc coating according to PN-EN 10346:2015 standard, with minimum weight of 100 g/m2 and nominal thickness of 7 um, or, with electrolytic zinc plating according to PN-EN ISO 2081:2011 or PN-EN ISO 4042:2001, with a minimum weight of 5 µm.

Dimensional deviations comply to the standards:

  • threads: PN-EN 10143:2008,
  • steel sheet thickness: PN-EN 10143:2008,
  • dimensions of other elements of the STRUT mounting system comply with tolerance class m according to PN-EN 22768-1:1999 standard.

Available corrosion protection materials and coatings are shown in the table below:

Description

Material

Standard

Corrosion protection coating

LDB, LDBST and LDBDT mounting rails

DX51D+Z100

PN-EN 10346:2015 Hot-dip zinc coating
with min. the thickness of 7 µm

W-LDB and WK-LDB wall brackets

S235JR PN-EN 10025-2:2007 Electrolytic zinc plating
with min. the thickness of 5 µm

Slide nuts SNP, SNL and SNKL

S235JR
spring: steel wire

 PN-EN 10025-2:2007
PN-EN 10270-1+A1:2017

 Electrolytic zinc plating
with min. the thickness of 5 µm

Threaded rod PG

mechanical properties classes
not lower than 4.6
PN-EN 898-1:2013 Electrolytic zinc plating
with min. the thickness of 5 µm


strut channel certificate
When installing the support system, the performance of the mounting rails must be taken into account.
Check strength parameters of STRUT channel system in the National Technical Assessment ITB-KOT-2019/0940

The characteristic and design strength of the supporting elements is determined by dividing the characteristic strength by a safety factor equal to:

  • 1.54 – for mounting rails and wall brackets,
  • 2.0 – for slide nuts.

loads allowed for mounting rails, i.e. the minimum stress required to cause element failure. Remember to choose the support system, for which strength tests have been performed.



The Profitability of an Investment in Photovoltaics


How to calculate the return on investment (ROI) - in order to estimate this parameter, use the following formula (every system will be different from the example below):

  • 1 kWh of energy with assumed price - PLN 0.6
  • a 4 kW photovoltaic system generates electricity valued as PLN 2200 per year
  • a 4 kW system will cost the investor about PLN 30000
  • with that price, the investor waits nearly 14 years for the return on investment (if electricity prices increase, this period will be shorter as well)

The more electricity a household consumes, the faster the PV investment will return pay for itself.

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