Know the basics of how solar panels work.
How solar panels work to produce electricity from sunlight is one of the most frequently asked questions by many people. This is because solar power is one of the few renewable, low-carbon energy resources with technological maturity to meet ever-growing global demand for electricity. Solar panels work through a phenomenon called photoelectric effect, which is the ability of matter to emit electrons when a light is shone on it. It is a property exhibited by some special materials when exposed to light that causes them to absorb the tiny particles or packets of energy called photons, with which the light is composed of, and release electrons from their atoms. When these free electrons are captured usable electric current results.
What is a solar panel?
Before I go to explain ‘how solar panels work’ let’s first look at what is a solar panel.
Solar panels are made up of many Photovoltaic or solar cells. Just like the cells in a battery, the solar cells in a solar panel are small devices designed to generate electricity. However, while a battery’s cells make electricity from chemicals, a solar panel’s cells generate electricity by capturing sunlight instead. Solar cells are made of special materials called semiconductors. Silicon is the most commonly used semiconductor for making solar cell. Silicon carries millions of tiny atoms that have charged electrons. The most common design of solar panels today uses two different types of silicon – positively charged (P-type) and negatively charged (N-type). This is to create solar cell made up of two different layers, a layer of positively charged silicon and a layer of negatively charged silicon sandwiched together. To achieve this, small quantities of other elements is squeezed into the silicon layers. The silicon in the top layer is combined with phosphorus atoms which contain more electrons to create a negatively charged silicon (N-type) layer and the bottom layer gets a dose of boron, which contain less electrons to create a positively charged silicon (P-type) layer. When these two different layers of opposite charges are separated and placed side by side inside a solar cell it creates an electric field across the cell just like in a battery. This unique configuration enables a reaction that produces electricity when the silicon cells are exposed to sunlight.
Each Photovoltaic or solar cell generates very little power (a few watts) and so they are grouped together as modules. In order to maximize output dozens of the solar cells are packaged together into solar modules, which in turn are packaged into solar panels that are mounted on a rooftop and arranged to maximize their hours of exposure to direct sunlight.
How solar panels work to convert sunlight into electricity?
Now that we know what is a solar panel let’s take a look how solar panels convert solar energy to electricity. In simple terms, a Photovoltaic (PV) solar panel converts the sun’s rays into electricity by using the photons or particles of light from the sun to knock electrons free from the silicon atoms in the solar cells resulting in usable electricity. This electricity can then be used to supply renewable energy to homes or businesses. Let’s take a closer look at how solar panels work when the sunlight strikes a cell in solar panel.
Sunlight is composed of minuscule particles called photons or “packets” of energy, which radiate from the sun in the form of electromagnetic radiation. As these light particles hit the solar cell, the energy from the photons is transferred to the loose electrons in the silicon atoms. The energized electrons are then able to escape their bond with the atoms and move freely from one layer to the other layer of the cell providing a flow of electricity. Because of the way the cells are made with layers of material with differing atomic structures, it creates an electrical imbalance within the cell, which acts a bit like a slope down which the the free electrons are forced to move in one direction creating a direct current, or DC. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit and when the electrons flow through such a circuit in one direction, they generate Direct Current electricity, or DC. This DC current is then sent to an inverter which converts the direct current into Alternating Current (AC) for use in businesses and homes.
How solar power is integrated into the electricity grid
Now that we have the basic idea of how solar panels work for generation and flow of solar electricity, let’s take a look into how this solar power is integrated into the electricity grid for backup power when the sun isn’t shining or if extra power is needed.
The electricity generated by rooftop solar panels first supplies on-site needs, with the grid supplying additional electricity as needed. When the homes or businesses generate more electricity from their solar systems than their own requirements, the excess power is automatically fed back into the public grid, and a credit is allowed for this contributed electricity. At night when the solar system is not generating power in real time, the grid will provide energy for lights and other appliances as usual, in exchange for the excess energy it shared with the grid during the day. For this an export / import meter is installed by the power company to monitor how much is being imported or exported during the day.
Integration with the grid of a rooftop solar system with a larger amount of solar power provides many benefits. One of the biggest benefits that such solar system provides to the grid is that it often produces electricity when—and where the power demand is at its peak and most valuable. For example, in many regions demand on the electricity system peaks in the afternoon on hot, sunny days, when air conditioning use is high and when rooftop solar system is performing powerfully. Such systems, therefore, help utilities meet peak demand without firing up the expensive and more polluting power plants. Rooftop systems also reduce the strain on the power transmission and distribution equipment as homes and businesses first draw power from own system instead of relying completely on the electricity grid.
Here is a quick sum up on how solar panels work,
- The particles of sun light (photons) hits the solar cells of the solar panel;
- The energy from the photons is transferred to the loose electrons in the atoms of the semiconductor material with which the solar cells are made of;
- The energized electrons escape their bond with the atoms and the free electrons move in one direction from one layer to the other oppositely charged layer of the solar cell thereby generating DC current;
- The DC current is then passed through an inverter which converts the Direct Current into Alternating Current (AC) for use in homes and businesses;
- Any excess electricity that’s not used is fed back into the grid;
- Whenever more power is needed than the solar system can produce or when the solar system is not generating power in real time the required power is drawn from the grid;
- An export / import meter monitors the energy exported compared to the energy imported from the grid;
Now that I have explained what is a solar panel and how solar panels work to convert sunlight into usable energy, you might wonder why solar panels aren’t the primary source of power in the world. The problem is that it is still not a very efficient process for generating power. The amount of electricity created by solar panels is relatively low compared to the size of the panels. This is because the angle of the solar panels is very important for efficiency of the panels. The rated capacity of a solar panel is measured with sun-rays from direct perpendicular sun. If the panels are not facing the sun just right, the efficiency can drop considerably thereby reducing the amount of energy produced by the panels. However, with technological advances and improving efficiency, the production volume is steadily increasing resulting in reduction in the capital costs of solar panels. In any event, solar energy is gradually becoming a viable alternative in many situations. According to a recent report, more American homes than ever are investing in solar panels. As per a 2014 statistics, there were over 20,000 megawatts of cumulative solar electric capacity operating in the United States and around 650,000 homes and businesses had gone solar. The growth of solar capacity was also projected to double in the next two years. In fact, a report from the International Energy Agency indicates that solar energy could become the largest global source of electricity by 2050. In short, with solar technology improving everyday and costs dropping rapidly solar energy is truly the wave of the future.