olar energy comes from the sun – the most abundant energy source on Earth. People harness the sun’s power in two ways: either use solar heat to power a steam or gas turbine (concentrated solar power, CSP) or collect sunlight to generate an electric current (solar photovoltaics, PV). Even though concentrated solar has massive potential, it is currently less prevalent since it is viable only when used for large-scale projects requiring heavy investments. Solar photovoltaics, on the other hand, is suitable for solar projects of various scales: residential, commercial, community, and utility-scale.
What is solar energy, and how is it better than fossil fuels?
Even though photovoltaics is less efficient than CSP, its flexibility, simpler installation process, and rapid technology development together make it the most promising renewable energy source. According to expert estimates, solar PV is already the cheapest source of new electricity in most regions, and its share of all electricity generated globally will increase 20-fold by 2050, reaching 38%. On the contrary, the percentage of fossil fuels – coal, oil, and gas – is expected to shrink dramatically from the current 59% to just 12% in 2050.
So how did solar panels manage to win over? The chief reason is undoubtedly the environmental damage associated with burning fossil fuels. The UN report states that they are the most significant contributor to climate change by a wide margin, producing over 75% of global greenhouse gas emissions and about 90% of all carbon dioxide (CO2) emissions. Solar panels, on the other hand, offer renewable power free of dangerous pollutants. But environmental friendliness isn’t the only competitive edge of solar power: solar PV is becoming the cheapest option for new electricity generation in many countries, International Energy Agency (IEA) says.
What are solar panels?
A solar panel, also known as a solar module, is a device that captures solar irradiance and converts it into electricity to power our homes. They are composed of a series of smaller units called solar (photovoltaic) cells. The panels are components of a solar system - an electric power system handling the entire process, from capturing solar radiation to powering our home appliances. Home solar systems usually include 20 to 25 solar panels, which is enough to meet the electricity needs of a typical home fully.
Solar panels can be installed either on the house roof or the ground. Roof-mounted solar options are more popular for home installations as they are cheaper and don’t take up valuable space on your property. However, rooftop solar panels are more challenging to access and repair. Ground-mounted solar modules are more expensive, but they work well for those with a weak or damaged roof.
How does a solar system work?
Let's now look in more detail at how solar panels work and how they convert sunlight into usable power.
The sun emits solar radiation
The sun emits electromagnetic waves called solar radiation. This power travels in all directions through the surrounding space, and only a tiny part reaches our planes. Nevertheless, its amount is still enormous: the solar radiation hitting the Earth’s surface in a single hour is greater than the entire world consumes in a year.
Working solar panels collect the sun’s power
Sunlight carries photons, which the solar panels capture to create an electric current. However, not all the light reaching them gets absorbed. The solar spectrum ranges from 100 nm and 1 mm, which includes ultraviolet, visible, and infrared radiation. Solar panels can harvest only a limited number of wavelengths, namely, visible light and almost half the infrared light - a range between 400 nm and 1100 nm.
Solar cells convert solar radiation into electricity using the photovoltaic effect
A solar cell consists of two layers of semiconductor material (most commonly silicon): p-type and n-type. The p-type layer is made by adding an atom with one less electron than silicon atoms, usually, gallium or boron. The n-type layer is fabricated by adding atoms with one more electron in its outer shell than silicon (typically phosphorus) so that one electron can’t form a bond with nearby silicon atoms and remains free. When put together, these two layers create an electric field.
Solar cells work by transforming the incoming sunlight into electrical current via a phenomenon called the photovoltaic effect. When sunlight hits the surface of a solar cell, it knocks the electrons loose from their atoms, forming “holes”—empty places left behind by the released electrons. The electrons and their holes start moving within a solar cell in opposite directions, which is how an electric current is generated.
The solar inverter transforms DC from solar panels to AC used by home appliances
The wiring attached to a solar panel captures the current and brings it to a solar inverter. Solar panels produce direct current (DC) electricity, but most home appliances need alternating current (AC) electricity. The inverter is a piece of solar equipment that converts DC to AC, thus making the power generated by solar panels suitable for our homes.
There are two types of inverters: string inverters and microinverters. A string inverter is linked to a string of solar panels called the solar array and works by converting the current from all the panels in one place. Microinverters, on the other hand, are installed near each solar panel and convert DC to AC separately for each panel.
Electricity from solar panels powers your home or is fed to the grid
After the electric current is converted from DC to AC by a solar inverter, it is suitable for home consumption and ready to power your home appliances. But sometimes, a solar system generates more electricity than is required, so if it is tied to the local utility grid, it can feed this excess power into it. This is particularly advantageous for those living in areas with net metering policies that offer solar owners credits for every excess kilowatt-hour of power they send to the grid. These net metering credits can be used to partly offset the overall monthly electricity bill.
Solar power that is neither utilized nor sent to the grid is used to charge a solar battery
Householders living in the states without net metering programs or simply wishing to achieve maximum independence from the grid can pair their solar panels with battery storage. When a solar system produces any surplus electricity, it is used to charge a battery instead of being sent to the grid and consumed later, for example, at night when a solar panel system does not work.
Types of solar panels & how they work
Even though almost all home solar panels sold today work on the same principle, they fall into several types depending on their manufacturing technology. In the residential market, the most popular options are monocrystalline, polycrystalline, and thin-film. Let’s look at how they differ.
Monocrystalline panels have black solar cells with rounded edges. These cells are made from a single silicon crystal, which results in higher purity of the silicon wafers. Monocrystalline panels are the most efficient and long-lasting but are also the most expensive.
Polycrystalline panels are characterized by blue-colored cells with straight edges. As the name implies, they are made of multiple silicon crystals. Polycrystalline modules are typically less efficient as the electrons must overcome more resistance as they travel through the lattice structure of the cells.
Thin-film solar panels are made of one or more layers of thin-film material deposited on plastic, glass, or metal. They are flexible and lightweight, which makes them a good choice for curved and weak roofs. As for the shortcomings, thin-film panels perform worse than crystalline options and take up much space; therefore, they are less suitable for domestic applications.
Solar panels store electricity generated from sunlight, providing renewable energy for various applications.
How much money does a home solar system save?
A solar system is no small investment but will pay off in the long run. By some estimates, Americans that chose to fit their house with solar modules save from $44 to $187 on their monthly electricity bills, which means you can save up to $2,200 annually!
Wrap-up: for all its technological complexities, solar is a consumer-friendly way to generate electricity at home
Solar power isn’t an easy thing to digest, as increasingly sophisticated technologies back it. But despite how complex it may initially seem, getting a general idea of how it all works makes it much easier to pick the best solution for your home. Besides, solar modules give little to no hassle once installed, as modern solar systems are designed to deliver the smoothest user experience possible.