How Solar Panels Generate Electricity
How Solar Panels Generate Electricity
Light is energy. That’s the basic concept behind using solar panels to generate electricity. But, while that simple concept is easy to grasp, it might seem much more difficult to understand how a solar panel takes light from the sun and turns it into electricity that can power a light bulb or a television. While there is a big gap between these two concepts, it’s relatively easy to get when you understand two things: the components in a solar panel system and how they work together.
How Do Solar Panels Work?
Solar panels absorb energy and convert it into electricity. Here’s how it works.
Energy from the Sun – The sun constantly generates energy. This energy moves through space as electromagnetic radiation and most of it is scattered when it hits the earth’s atmosphere.
Electromagnetic radiation travels in a line by going up and down like a wave. The distance between these waves is called the wave length, which is measured in nanometers (nm). And, here’s the important part. Solar cells only absorb wavelengths between 380 and 750 nanometers. This includes light on the spectrum of violet to red, which is about 7% of all total sunlight.
How Solar Panels Absorb Solar Energy – Solar panels are made up of groups of interconnected solar cells. These cells are made of semiconductor materials, which collect energy. How? When violet to red wavelengths hit solar cells, they scatter electrons from their weak bond with the light atom. These electrons are then caught up in the electric field of the positive and negative layers of the solar cell. They then flow through conductors attached to the cells to create an electric current.
Efficiency – Efficiency is the rate at which the solar cell absorbs energy, so the higher the efficiency, the more energy you generate.
- Solar cell efficiency – Solar cell efficiency is the efficiency of the solar cell. This rate is typically much higher than that of the total panel.
- Solar panel efficiency – Solar panel efficiency is the efficiency of all of the solar cells connected together. Solar cells lose efficiency when connected to each other, which means that some panels might boast a high solar cell efficiency and a much lower solar panel efficiency. The highest panel efficiency is about 24%.
Different Types of Solar Cells – Solar cells directly affect efficiency and DC power output. Most solar cells are made of N-type (neutral) and P-type (positive) semiconductor materials. These materials are typically made of Crystalline silicone which is available in polysilicon and monosilicon.
- Polysilicon – Polycrystalline silicon, also called polysilicon cells, are composed of a number of smaller crystals, and as a result, have a lower efficiency, meaning that they produce less power.
- Monosilicon – Monosilicon is a single crystal cell, which is more efficient. They’re typically used in premium (more expensive) solar panels, and often offset the additional costs with improved energy efficiency.
High quality solar cells feature layers of different materials designed to trap different wavelengths, so that the cell generates more power. This means that the cell is made of pancaked silicone materials, which have each been shown to trap a certain wavelength of light. This allows you to generate more electricity with one panel.
The Basics of Electricity
When your solar panels absorb energy they create DC electricity. As you probably know, the electronics in the average home use AC. How do you get from DC to AC?
Converting DC Power into AC Power – DC energy or Direct Current energy flows in the same direction, a bit like a one way street. When it flows into your inverter, the inverter uses electromagnetic switches that flicker on and off to reverse the direction of the current, so that energy is flowing one way and then the other way, which is known as Alternating Current (AC).
Measuring Electricity – A meter measures the output of your solar panel system in kilowatt hours, which is a measure of using 1,000 watts over the course of one hour. A standard meter tracks the energy used, the energy imported, and the energy exported (sent to the grid).
Using Solar Power – The solar system connects to a building’s electrical system through a circuit board. When lights and other electrical equipment are on during the day, they automatically use the solar power generated by the system.
- Feeding Power into the Grid – When the building isn’t using the PV power generated by the panels, it is automatically fed back into the power grid. You can think of it like a double basin fountain. When the fountain collects rain, it goes into the top basin, but when you collect too much rain, it simply overflows into the lower basin, and is still part of the system. Except with solar, you’re talking kilowatts and not raindrops.
The Components of a Solar Panel System
A solar panel system typically consists of four to seven components depending on the setup.
Solar Panels – Solar panels directly harvest energy from the sun using solar cells. These panels consist of photovoltaic modules which include 6 x 10 (or more) solar cells. PV modules are rated based on their DC power output and their efficiency.
Balance of Systems – The balance of systems or BOS includes all components of the solar panel system except for the photovoltaic panels. This includes wiring, switches, battery banks (when applicable), battery charging (when applicable), meters, charge controllers, and inverters.
- Inverter – Solar panels produce DC energy. The inverter converts DC power into AC power, which is used by most electronic devices.
- Switches – Switches are used to direct solar power where it needs to go.
- Meter – A solar meter tracks your energy usage, energy export, and energy import. Distributor – A distributor is any distribution system including wiring, switches, and cables.
- Battery – A battery or battery system stores power if you do not want to feed energy into the grid. However, most business systems do not use batteries.
- Charge Controller – A charger controller prevents energy surges and prevents batteries from overcharging.
While it initially sounds complicated, the components of a solar panel system are easy to understand. Solar panels collect the energy from the sun, the inverter converts DC to AC energy, and then it is either used or sold to the grid. And, now you know!