Introduction to PV cells

Solar Panels

Solar Power System Components

Kinds of Solar Power Systems

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Solar Photovoltaic (PV)

Introduction to PV cells

Solar energy from the sun is converted to electricity that can be used to power your home or building through the use of so-called Photovoltaic (PV) Cells or Photovoltaic (PV) Modules. The word "photovoltaic" comes from a combination of "photo", which means light, and "voltaic", which means electricity. Thus the word literally means electricty from light.

solar charger.
A solar cell made from a monocrystalline silicon wafer. From US DOE.

Photovoltaic cells are made up of semiconductor materials such as silicon. When light strikes this material, a certain amount of energy is absorbed by the semiconductor. This energy loosens electrons from the material. The now-flowing negatively-charged electrons move in only one direction due to the special characteristics of the semi-conducting material, thus generating direct current (DC) electricity. This current can then be used to power solar devices, whether a small solar calculator, a cellphone or laptop, or even an entire house. Solar cells are long-lived products, and are capable of producing electricity for more than twenty years while retaining much of their efficiency. Because of this, the typical warranty given by most manufacturers is 25-30 years.

solar charger.
In this image, PV cells in one of our solar Mobile Chargers are used to charge a mobile phone.

Solar Panels

Solar cells can charge not only small devices such as lights and chargers and calculators, but they can also be used to harness the power of the sun to produce electricity for your home or building.

Solar cells make up solar panels or modules, which are the cornerstone of such a solar power system. A solar array is created when several solar modules are wired together. The size of this array determines the amount of power (measured in watts or kilowatts) that will be produced by the system.

20w solar module.
Diagram of 20W (watt) Solar module. Several such 20W modules can be wired together to create a solar array.

Solar Power System Components

In addition to the solar panels, the solar power system may contain various other important components.

  • Charge controller - sits between the solar panels and any batteries that you are using to store the energy being generated by your system. Its function is to regulate the voltage generated from your solar panels and protect your batteries from being over and under charged, thus ensuring maximum battery life.

  • Batteries - are used to store the energy that is created by your solar power system.

  • Inverter - converts the DC (Direct Current) energy stored in your batteries and turns it into the AC (Alternating Current) power you use in your home.

Kinds of Solar Power Systems

There are different kinds of solar power systems, mainly based on the presence and configuration of the various components.

  • Stand-alone systems

    Such systems are not connected to the electrical grid, and are used when the home or building is isolated from any utility sources. In this case, the solar panels connect to the charge controller, and then to batteries, where they can be converted to AC by an inverter or used directly. These solar systems allow the isolated residence to function away from the electrical grid.

  • Grid-Tied Systems

    In this system, there is no battery. The solar panels connect directly to an inverter, and then to the utility grid. When you system is producing energy, the power generated is fed back to the grid, and if you are producing more electricity than you're using, your electricity meter can even spin backwards. In a sense, the grid in this case functions as your "battery".

  • Battery Backup System

    In this system, the solar panels charge your battery, which can then feed back to the grid when it's full. If the utility grid fails, then you will be able to use the batteries to continue to power your critical devices. The main disadvantage of this system is that your cost per watt will be much higher than the Grid-Tied Systems because of the costly battery apparatus.