The most common renewable energy used is solar energy. In recent years, there is a growing need and focus for energy-saving materials. Solar panels are one of them.

The creation of electricity by burning coal or oil produces carbon dioxide which contributes to global warming, whereas electricity from solar radiation produces zero emissions. It also provides environmental benefits by reducing air pollution.

A photovoltaic system is used to convert light into electrical energy. The process of converting light(photons) to electricity(voltage) is known as the Photoelectric effect.

Photovoltaics

They can be installed on the roofs of residential or commercial buildings or available ground space. One of the main functions is that it converts energy from solar radiation into electricity with the use of solar panels.

Pros and Cons of Solar Panels

Pros :

• Durable and lasts longer.
• Require minimal maintenance.
• Projects range from small scale projects to large scale projects.
• Can be located at user’s site.
• Photovoltaic electricity can offset high electricity rates.
• Can be installed in any size.
• Efficient
• Produces clean energy with no emissions
• Sustainable
• Increases property value

Cons:

• Expensive upfront investment
• Occupies more space, minimizes ground/terrace open space.
• Energy storage is expensive

Photovoltaics and Its Components

Photovoltaics are silicon-based devices. They are available in a variety of sizes and shapes.

Under the presence of sunlight, they generate a low-voltage direct electric current by using solar cells.

• Solar panels
• Mounting racks
• Electric panels
• Invertors
• Wind deflectors

Solar Panels/Photovoltaic panels

Solar Panels – Solar Panels are made up of smaller units called PV cells or solar cells while solar cells are made from Silicon which is a semi-conductor. PV cells are connected in a series to generate a higher voltage and forms a panel. Each module comprises of 60 or more solar cells as per guidelines.

• Solar panel voltage depends on the number of solar cells. The more, the no, the higher amount of voltage.
• Solar cells comprises three layers –
  • negative N-type Layer : contains high concentration of electrons
  • P-N junction
  • positive P-type Layer : contains high concentration of holes

The cells are laminated with a protective layer of glass backed with metal sheething.

Invertors and DC wiring

DC wiring – Runs DC current to invertors.

Invertor plays an important role. An inverter converts the DC electricity from the photovoltaic array into an alternating current (AC) that can connect seamlessly to the electricity grid. The inverter also senses the utility power frequency and synchronizes the photovoltaic-produced power to that frequency. (from wbdg.org)

Two types of Invertors

• String Invertors
• Micro Invertors

Mounting Systems

Mounting Racks – The structures holding the panels/modules are called mounting racks. They can be directly attached to the roof/ground or any other structure, however, they must withstand wind loads.

Types of Mounting systems :

• Structurally attached
• Membrane integrated
• Ballasted
• Hybrid

Electric Panels

It also consists of electric panels and related equipment. Switches, fuses, transformers, etc.

Wind Deflectors

Minimize the wind load on the panels.

Types of Technology

• Crystalline Silicone modules
  • Photovoltaic cells are made from silicon crystals.(Mono or poly-crystalline silicon modules).
  • Commonly used in most applications and are expensive.
  • Highly efficient.
• Thin-film Modules
  • Made from amorphous thin-film silicon such as cadmium telluride.
  • Lower levels of efficiency and cheaper than crystalline silicon modules.
  • Requires more space than silicon modules.
  • Efficient in poor light conditions.
• Other technologies
  • Newer materials including copper indium selenide and copper indium gallium selenide.
  • Multilayer thin composites
  • Using Mirrors
  • Plastics, solar dyes, mirrors, etc.

Working

The electrons of the N-type layer try to reach the P-type material creating a negatively charged layer. Similarly, the holes of the P-type layer try to reach the N-type layer creating a positively charged layer. Thus creating a junction or depletion layer.

The photons from the solar rays hit the solar panels to reach the depletion layer containing neutral atoms. These atoms break when the photons from the sun rays strike the junction. This hits the electrons from the neutral atom leaving the holes behind and producing free charge carriers. Due to the presence of an electric field and the flow of electrons and holes, electricity (DC – Direct Current) is generated.

DC wiring is used that runs DC current to invertors and inverters convert DC to AC. AC wiring brings current to switches and switches bring power to the meter, utility meter and are interconnected to the grid.

Solar Panels and Applications

Factors to consider while installing a photovoltaic system are

• The site is to be free from shade from other buildings, trees etc. for most of the day.
• Ground areas are to be free from any obstructions.
• Structurally, the roof has to handle the weight of the system.
• Roof orientation – south face roof area, location and tilt angle
• Checking for wind loads, thermal forces, etc.
• Fire protection measures

Typical Installations are –

• Roof top/terrace system installation
• Ground mount installation
• Photovoltaic slates and tiles as roofing
• Photovoltaic glazing as cladding

1.For Roof Top Installations

• Residential applications – flat roof/sloped roof.
• Commercial and Industrial applications – Ground mounted/sloped roof mounted. Unused roof area for commercial buildings can be used to install these systems.
• Flush-mounted on tiles for sloped roofs.
• The roofing system has to be durable, take the load of the photovoltaic system and long-lasting.
• The materials used for the roofing system have to be fire-resistant to prevent short-circuits and fire.

Mounting options

• Railed Mounting systems – Attaching a set of standard rails to the roof. Each panel attaches the two rails with clamps. The rails are secured to the roof top by bolts and screws with flashing installed.
• Rail less /Ballasted Mounting system – Bolts and screws are directly attached to the roof and secured to the panel.
• Shared Rail systems – Similar to railed system, but here the rails are shared by the panels, thus minimizing the no.of rails used.

2.Ground Mount Installation

Commercial and Industrial applications – Ground mounted/sloped roof mounted. Ground areas specially to occupy photovoltaic systems for the use of solar energy.

Mounting options

• Foundation Mounts – Requires foundation with vertical pipes and rails in place to hold the system.
• Ballast footing mounts – Used where the soil is not good enough for foundation. It consists of pre-cast concrete blocks attached to the ground.
• Pole Mounts – simple steel pole is anchored to the ground on concrete and it supports the solar panel.
• Multi-pole Mounts – Similar to pole mounted but laid in a horizontal line on multiple poles.

3.Photovoltaic slates and tiles as roofing

Solar roof tiles are expensive than solar panels. They are shiny plain tiles and look similar to tradition roof tiles/fiber-cement tiles. The lower part of the tiles comprise photovoltaic cells which are connected to the system.

• Solar roof tiles are sleek and subtle.
• Ecological alternative to standard roofing.
• Durable.

4.Photovoltaic glazing as cladding

Photovoltaic cells are integrated into the glass of laminated or double-glazing systems. Also called solar singles or photovoltaic shingles.

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