Photovoltaic solar systems are the most common method of generating electricity from the sun. These systems consist of many components. Although almost everyone thinks of photovoltaic systems as consisting of solar panels, fundamental components such as batteries, inverters, and charge controllers are also very important for this system.
What is a Photovoltaic System?
Photovoltaic means electricity generation from light. The electricity generation is provided by photovoltaic panels (PV). Today, it is the most common system used in electricity generation from the sun.
Photovoltaic systems are divided into three according to the way the electricity produced is used. These are off-grid systems, grid-tie, and irrigation systems. Before introducing these systems to you, I would like to introduce the main system components used in solar PV systems.
Components of the Photovoltaic System
There are main 4 components used for photovoltaic system: Solar panels, solar inverters, solar batteries, and charge controllers. Let’s take a closer look at these components.
Solar panels, the most main part of photovoltaic systems, are the part where electricity is generated from the sun. The solar panel converts solar energy directly into electrical energy by means of solar cells made of semiconductor silicon material. Solar panels are available in different power capacities.
Commonly used solar panels in the market; 5W, 10W, 60W, 100W, 150W, 400W, 450W, 500 W power capacity solar panels. There are monocrystalline, polycrystalline, thin-film, and many other types of solar panels. Furthermore, there are new generation solar panels such as half-cut, bifacial, flexible, and perovskite solar panels.
Charge controllers regulate and stabilize the DC energy generated by the solar panel and create stable DC electrical energy for charging the batteries. In order to charge the batteries from a DC source, the charging current and voltage must be regulated and constant. The voltage and current produced by the solar panel are not constant, so the charge controller is needed for efficient charging of the batteries. Charge controllers also prevent reverse current flow from the battery to the panels. It also protects the battery from overcharging. The charge controller cuts off the electricity from the solar panel when the battery is fully charged. There are two types of charge controllers: PWM and MPPT charge controllers.
Batteries used for solar photovoltaic systems, are often called solar batteries. So the solar battery’s quality is very important for off-grid photovoltaic systems and hybrid systems (grid-tie systems with battery backup). Solar batteries should have high charge-discharge efficiency and a long lifetime. They must be resistant to temperature and adverse environmental conditions. We will discuss the technical details of solar batteries in another article. Commonly used solar batteries are gel batteries, lithium-ion, special OPZS type aqueous batteries, and some deep cycle lead acid batteries.
Inverters are electronic devices that convert DC electrical energy into AC electrical energy. Inverters that are used for photovoltaic solar energy systems, are called solar inverters. We can consider solar inverters in two categories: off-grid solar inverters and grid-tie solar inverters.
There are three types of solar inverters that are used for Off-Grid photovoltaic systems: square wave, modified sine, and full sine. Modified sine and full sine models are frequently used in off-grid solar systems. I will give details and technical specifications of all of these in a separate article.
Inverters, also called solar inverters, full sine models are of two types, MPPT and PWM. The new generation inverters used in solar systems are smart inverters that also include a charge controller. These types of inverters show the electricity production data of the solar panel, battery voltage values, and electricity usage to the user. These inverters also contain a convector (AC-DC converter) so that the batteries can be charged via an electric grid.
So grid-tie solar inverters are a bit different than off-grid inverters. These inverters are specially made for grid connections. They have features such as working in coordination with the grid and providing electricity transfer from the grid to the load as a result of power reduction in the panels. These are available in single-phase and three-phase types.
In these systems, the inverter power capacity should be parallel to the panel power, unlike in off-grid systems. Grid-tie inverters have remote monitoring features. So the user can remotely monitor parameters such as the electricity production of panels during the day, daily electricity consumption, and total electricity production. Wherever the users are in the world, they can monitor their production and consumption data.
Solar Photovoltaic Systems
Solar photovoltaic systems can be considered into two main categories: Off-Grid and Grid-Tied Solar PV Systems. Let me give you more details about these systems.
Off-grid solar systems are photovoltaic solar systems that are not connected to the electricity grid and store the electricity produced by solar panels by solar batteries and convert it into electricity by solar inverters that we use in our homes. Off-Grid solar systems basically consist of four main components: solar panels, solar battery groups, charge controllers, and solar inverters.
Let me explain how the off-grid solar system work. The electricity generated from the solar panel is regulated by the charge controller and stored in the solar batteries. This stored energy is converted into the electrical energy we use at home by solar inverters. This is somewhat similar to the principle of charging the car’s battery with the charging dynamo in vehicles. Solar Battery quality is very important for off-grid photovoltaic systems. Batteries with high charge-discharge efficiency, resistance to high temperatures and long life should be preferred.
Grid-Tied Solar PV Systems
These systems are actually power plant systems, whether small or large. Because the electrical energy produced from the panels is sold to the grid using single-phase or three-phase solar inverters. Grid-tied systems consist of four fundamental components: solar panels, inverters, bidirectional meters, and data loggers.
So how does the grid tie system work? Let me explain.
The electrical energy generated from solar panels is regulated by grid-connected inverters and converted into a form that can be transferred to the power line. The generated electricity is sold to the grid. When the weather is overcast or the production is low, the electricity need is met by transferring electricity from the grid to the load. If there is a problem caused by the grid, the inverter shuts itself off. So if there is a power cut in the grid, your home will also be cut off.
As you can see, photovoltaic systems are a technology that incorporates many different disciplines. Therefore, when designing the systems, the capacity calculation and quality of these basic components must be determined very well.