How Do Solar Panels Work? Solar Energy Explained

Solar panels absorb energy in the form of sunlight and convert it into usable electrical energy. They do this using many individual solar cells to harness as much of this energy as possible.

Sunlight (or solar energy) is an unlimited resource unlike fossil fuels like oil and natural gas. This means electricity created from solar panels is completely renewable. On a sunny day, 1000 W of solar energy hits the earth surface per m² that could be converted into usable electricity. In fact, the amount of sunlight that reaches the Earth’s surface in 90 minutes could fulfil the world’s energy consumption for an entire year.

Solar panel technology is now widely accessible across the globe. As of 2023, 6.8% of the UK's electricity is generated via solar energy. As this technology keeps improving, it can be useful to understand the science behind solar panels.

How Do Solar Panels Work? Step-by-step

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Solar panels convert our planet’s most abundant energy source, sunlight, into electricity that we can use to power our appliances. This process can be broken down into four key steps.

1. Absorbing sunlight: Sunlight shines onto a solar panel, which is made up of many smaller units called photovoltaic cells, also known as solar cells. Photovoltaic cells contain semiconducting materials, such as silicon, which can convert light into electricity.
2. The photovoltaic effect: Sunlight is made up of very small particles of energy called photons. When the semiconductors absorb photons, this causes electrons to become excited and move around. These excited electrons become free-flowing within the semiconductor. This is known as the photovoltaic effect.
3. Producing an electrical current: The free-flowing electrons are forced to flow in a specific direction within the semiconductor, producing a direct current (DC) of electricity.
4. Electricity for your home: The direct current passes through a power inverter which turns it into alternating current (AC) electricity. This is the form of current that is used by most household appliances.

Solar Panel Structure

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A solar panel is made from a sheet of individual solar cells that are organized into different configurations depending on their efficiency and performance requirements. The solar cells are held together during manufacture with layers of a highly transparent film.

Solar panels are designed to be placed outside so that they can be exposed to sunlight. Once encapsulated, the top and bottom surfaces are covered with high strength tempered glass and moisture-resistant polymer back sheets. These layers improve the durability of the solar panel and increase the lifetime of the solar cells in an outdoor environment.

When assembled, a solar panel houses the electrical connections and output wires in a junction box.

What is Solar Energy?

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Solar energy is a form of energy produced by the sun. The sun can be compared to a giant nuclear fusion reactor which is constantly producing energy in the form of photons.

The amount of solar energy the Earth receives is vastly greater than the current energy demand. On a clear sunny day, 1000 W/m² of solar power hits the earth's surface. It is no surprise that research is focused towards a ‘solar revolution’ which could one day see all our homes powered by sunlight alone.

The amount of energy that a photon has can be determined by its position on the electromagnetic (EM) spectrum. Some examples of high energy photons emitted by the sun include gamma rays, X-rays, and ultraviolet radiation (UV rays). Whereas the heat that we feel from the sun comes from lower energy photons which make up infrared radiation.

The majority of solar energy that makes it to Earth lies in the visible light region of the EM spectrum. Visible light photons have an energy which lies between infrared radiation and UV rays. Most solar panels are designed to absorb as much visible light as possible. However, there are panels in development which can also make use of UV or infrared light.

To make efficient solar panels, it is important to mimic the solar energy received on Earth as closely as possible. Solar simulators accurately replicate sunlight to help scientists test the efficiency of the solar cells they develop.

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