How Do Solar Panels Work？

What is Solar Energy

Solar energy, in short, is energy from the sun. This energy radiates to the earth in the form of light and heat and is one of the most abundant and widely distributed renewable energy sources on earth. The main characteristics of solar energy include its universality, cleanliness, and immensity.

Solar energy is virtually ubiquitous and can be utilized wherever on the planet it can receive sunlight exposure. This makes solar energy a source of energy that is virtually unlimited geographically. No pollutants or greenhouse gas emissions are produced during the utilization of solar energy, making it environmentally friendly. It helps to reduce global greenhouse gas emissions and mitigate the problem of climate change.

It is estimated that the energy projected onto the Earth by the sun each year is equivalent to the heat generated by the burning of 130 trillion tons of coal, which is tens of thousands of times the total amount of all energy generated on Earth. This means that the potential of solar energy is enormous, and if it can be effectively utilized, it will be able to meet the long-term future energy needs of mankind.

In practice, solar energy is mainly converted and utilized through devices such as solar panels (also known as photovoltaic panels). Solar panels are able to convert sunlight directly into electricity for use in homes, businesses, and more. In addition, solar energy can also be converted into thermal energy through devices such as solar water heaters for heating, hot water, and other domestic needs.

Components of solar panels

Solar panels, also known as photovoltaic panels, are made up of the following key components:

• Photovoltaic cell (solar cell unit): this is the core part of a solar panel and is responsible for converting the sun's energy directly into electricity. Photovoltaic cells are usually made of semiconductor materials, such as monocrystalline silicon, polycrystalline silicon, amorphous silicon or thin film materials. These materials have a special photovoltaic effect that enables them to absorb light energy and release electrons when sunlight hits their surface, thus generating an electric current.
• Encapsulation materials: PV cells are very fragile and susceptible to external environmental influences such as water vapor, dust, and mechanical stress. Therefore, they are encapsulated in protective shells made of transparent, weather-resistant materials such as glass or transparent plastics. The encapsulation material not only protects the PV cells from damage, but also allows sunlight to penetrate to reach the cell surface.
• Backsheet: The backsheet is located on the backside of the solar panel and mainly plays a supporting and protective role. It is usually made of weather-resistant, insulating materials such as aluminum, polymers or composites. The backsheet prevents the external environment from eroding the photovoltaic cells and enhances the mechanical strength of the entire panel.
• Junction boxes and connectors: A junction box is a small box on a solar panel that contains the circuitry and terminals for connecting PV cells. It allows multiple PV cells to be connected in series or parallel to increase the output voltage or current. Connectors, on the other hand, are used to connect the solar panel to an inverter, grid, or other load device.
• Bezel: The bezel is the external frame of the solar panel, usually made of metal materials such as aluminum alloy or stainless steel. It not only enhances the overall structural strength of the panel, but also protects the internal encapsulation materials and PV cells from mechanical impact and damage.
• Anti-Reflection Film (Optional): In order to improve the conversion efficiency of solar panels, some manufacturers coat the surface of PV cells with an anti-reflection film. This film reduces the reflection of light on the surface of the cell so that more light is absorbed by the cell and converted into electricity.

Solar panels are complex systems consisting of multiple components that work together to convert the sun's energy into electricity. The quality and performance of these components have a direct impact on the efficiency and lifetime of the solar panel.

How solar panels work

The working principle of solar panel is based on the perfect combination of photoelectric effect and semiconductor technology. It skillfully captures the sun's rays and converts them into electrical energy that we can utilize.

Basics of the photoelectric effect

The photoelectric effect refers to the phenomenon that when light (especially ultraviolet, visible and some near-infrared light) strikes the surface of certain substances (e.g., metals, semiconductors, etc.), electrons on the surface of the substance absorb the energy of the photons and are excited to form an electric current or voltage. This is the basis for solar panels to be able to convert sunlight energy into electricity.

Composition and structure of solar panels

Solar panels are usually composed of multiple solar cells (also known as photovoltaic cells), each of which is made of a semiconductor material such as monocrystalline silicon, polycrystalline silicon or amorphous silicon. These semiconductor materials have a special pn junction structure, and when light hits the pn junction, the photoelectric effect occurs.

Solar panel working principle in detail

Generation of electrical energy

• Photon Absorption: When the sunlight irradiates the surface of the solar panel, the photons will penetrate the protective layer and encapsulation material, and reach the vicinity of the pn junction of the semiconductor material.
• Photoelectric effect: At the pn junction, photons interact with electrons in the semiconductor material. The energy of the photons is absorbed by the electrons, causing them to jump from the valence band to the conduction band, forming free electrons and holes (positively charged vacancies).
• Charge Separation and Electric Field Formation: Due to the special properties of the pn junction, free electrons and holes move towards the n-region and the p-region respectively under the action of an electric field, forming a potential difference, i.e. an electric field.
• Current generation: When the external circuit is turned on, electrons and holes move directionally under the action of the electric field, forming a current. This current is the electrical energy output from the solar panel.

Electrical energy output and conversion

• DC Output:The direct output of the solar panel is direct current (DC). The magnitude of its voltage and current depends on the area of the solar panel, light intensity, temperature and other factors.
• AC Conversion:Since most household appliances and power grids use alternating current (AC), the DC output from solar panels needs to be converted to AC through an inverter.An inverter is an electronic device that converts DC to AC and adjusts the voltage and frequency as needed to match the requirements of the grid or load.
• Connecting to the grid or load:The converted AC power can be directly connected to the power grid to supply local users or transmitted through the grid for use elsewhere.It can also be directly supplied to loads, such as household appliances, machinery and equipment.

Efficiency and energy loss of solar panels

Working efficiency of solar panels

The working efficiency of a solar panel, also known as the photovoltaic conversion efficiency, refers to the ability of a solar panel to convert the sun's light energy into electrical energy. It is usually measured by two dimensions: cell conversion efficiency and solar panel power generation efficiency.

Cell conversion efficiency:

• Definition: cell conversion efficiency is the ratio of cell power to cell area.
• Status: The cell conversion efficiency of solar panels on the market today is usually 18-24%. The higher the cell conversion efficiency of a solar panel with the same power, the smaller the panel size. For example, a 100W solar panel, if its total cell size is 97cm x 47.3cm (i.e., an area of 0.45881m²), then the efficiency of this solar panel cell is 21.80% (calculated as: 0.1kw/0.45881m² = 21.80%).

Solar panel power generation efficiency:

• Definition: solar panel power generation efficiency is the ratio of the actual output power to the maximum output power when in use.
• Influencing factors: Solar panel power generation efficiency is affected by a variety of factors, including the solar panel's own factors (such as whether the full power, the quality of the battery cell, the transparency of the encapsulation material, the current collection capacity of the battery cell, etc.) and external environmental factors (such as light intensity, temperature, etc.). For example, if the actual output power of a 100W solar panel is 60W, then its power generation efficiency is 60% (calculated as: 60W/100W=60%).

Energy loss:

Energy loss mainly comes from the reflection of the PV panel surface, cell efficiency limitations, temperature effects and shadow shading. Although the reflective film can reduce the reflection loss, but there is still part of the light energy loss. Low cell efficiency directly leads to low energy conversion rate. High temperature environments reduce cell conversion efficiency, and shadows and dirt are also important factors in energy loss.

Measures to reduce energy loss:

• Select high-efficiency batteries to improve the initial conversion efficiency. TOPBULL Select Lithium Batteries: 24V 100Ah LiFePO4 Lithium Battery
• Use heat dissipation measures to control temperature and maintain efficient working condition.
• Clean PV panels regularly to avoid shadows and dirt obscuration.
• Reduce the shadow effect by automatic tracking system and optimize the layout to reduce shading.

Can solar panels work in cloudy weather?

Solar panels are able to work continuously in cloudy conditions to provide clean energy for our lives, despite the challenge of significantly lower light intensity. Although the efficiency of solar panels is significantly lower on cloudy days compared to sunny days because clouds block most of the sunlight, reducing the number of photons that reach the panel surface, which in turn affects the photovoltaic conversion process. However, this does not mean that solar energy cannot be utilized at all on cloudy days.

There are a number of optimization measures we can take to maximize the efficiency of power generation on cloudy days. First, it is critical to select high-efficiency solar panels that have higher photoelectric conversion rates and better low-light performance to absorb and convert light energy even in low-light conditions. Secondly, increasing the mounting area of solar panels is also an effective means. By increasing the absorbing area, even if the efficiency of individual panels decreases, it can be compensated by the quantitative advantage, thus maintaining the overall power generation capacity.

In addition, it is vital to keep the surface of solar panels clean. Dust and dirt can impede light penetration and reduce the panel's power generation efficiency. Therefore, regularly cleaning the surface of solar panels to ensure that they are always optimized for light absorption is an important part of improving power generation efficiency on cloudy days. Finally, having an energy storage system is also an effective strategy for dealing with the challenges of cloudy days. Energy storage systems ensure the continuity and stability of the solar power system by storing excess power when the sun is shining and making it available for use on cloudy days or at night. Through a combination of these measures, we can better utilize solar energy resources and contribute to sustainable development.

Solar Panel Prices and Purchase

In recent years, the price of solar panels in the U.S. market has been gradually declining as the global cost of solar panel production decreases and competition in the market intensifies. This trend is influenced by a number of factors, including technological advances, scale effects, supply chain optimization, and changes in the global trade environment.

According to market analysis and forecasts, the price of solar panels in the U.S. market is expected to decrease further in the coming years, especially with the application of new technologies and the expansion of production capacity. The price of solar panels varies by brand, model, power and quality. High-end brands and high-efficiency solar panels are usually more expensive, while common brands and standard performance solar panels are relatively affordable.
When purchasing solar panels, consumers should first define their needs and budget, including the required power, size, installation method and expected service life.

Consumers should carefully compare different brands and models of solar panels, focusing on factors such as their conversion efficiency, quality certification, after-sales service and price, and choose products with better cost performance.

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