Solar PV Basic Concepts

We will start discussing the basic concepts regarding solar PV. These are the most basic concepts that will serve as the foundation for all the following chapters. We will be discussing about the solar resource, how to optimize the available solar resource through tilt and orientation, how the PV modules convert sunlight into electricity and lastly, the different types of solar PV systems: on-grid, off-grid & hybrid systems and their applications: residential, commercial and utility-scale.

Solar Resource

The sun is a sphere of hot gas and plasma that produces energy through nuclear fusion at its core. The sun fuses 620 million metric tons of Hydrogen gas per second to form Helium. This process converts some of the mass to energy which is radiated outward from the core.

The solar radiation emitted by the sun gets spread out in space, which means that the solar radiation received by an object decreases as it gets farther from the sun. Fortunately, the Earth’s distance from the sun is just inside the Goldilocks’ Zone. This zone is the region around a star where the received radiation is not too much or too less, allowing liquid water, and therefore, also life, to exist.

In 14 and a half seconds, the Sun provides as much energy to the Earth as humanity uses in a day. This just shows the huge potential of solar energy as an energy source. In 2011, the annual global energy consumption is at 17 TWy (TeraWatt-year, which is equivalent to 8.766 x 1012 kiloWatt-hours). The total energy potential of all the energy sources available on Earth is shown below:

The solar irradiance or the power per unit area received from the sun outside the Earth’s atmosphere is equal to 1.36kW/m2. This value is called the solar constant because, as the name suggests, it is a fairly constant value that does not change significantly. The radiation at the Earth’s surface, however, varies greatly due to: