How Solar Works
How do home solar panels, inverters and battery systems work?
How Solar Works
To understand if solar makes sense for you and your home, it's important to know how solar works. Now you don't need to understand every detail to save money with solar, but if you've ever wondered how and why those solar panels on roofs work we've got you covered.
Looking for a quick answer on how solar works?
- Solar panels absorb photons (solar energy) from the sun and in doing so generate an electric current. The current generated is direct current or DC.
- Inverter(s) convert DC electricity into alternating current (AC) electricity. There are two main types of converters: string inverters, and micro inverters.
- The converted energy can then be used to power your home!
- A net meter measures your electricity flow - to and from your home.
Want more detail? We'll walk you through how solar works by first addressing what solar energy is.
What is Solar Energy?
Did you know that all of the energy we use comes from the sun?
You probably know that's true for solar panels, but the sun is also the ultimate source for energy generated by wind, water and fossil fuels.
Here's how it works.
Heat from the sun drives the air currents and water cycles that turn wind turbines and power hydroelectric dams. Meanwhile, the sun's rays also grow the plants that ultimately become wood, coal and gas.
The sun has produced energy for billions of years and naturally energizes all of the plants on the planet. These plants give energy to animals and power the human body. This is done by a process called photosynthesis.
For decades now, scientists have unlocked the secrets of how a plant creates energy through photosynthesis and they can duplicate that process using modern technology in silicon. This process of creating electricity from the sun can power our homes and cities.
So, what if we could open the most direct path between the sun and the energy we use every day?
Let's take a step back so we can understand the sun's real power and potential.
The sun is a massive, flaming sphere of gasses, 330 thousand times more massive than Earth. At its core, the sun is 27 million degrees Fahrenheit, which is 60 thousand times the temperature of your oven when you bake a pizza! The sun gives off lots of energy into space as heat and light, called solar energy.
Right now, we aren't using all this energy―instead, we mostly rely on coal, oil, natural gas and other sources. But these resources aren't renewable, which means they'll eventually run out. Not only are these non-renewable resources going to run out, burning them pollutes our planet and contributes to climate change.
The sun's energy, on the other hand, will not run out for the next five billion years. That makes it a renewable resource.
How Do Solar Panels Work?
Solar panels are made up of smaller units called solar cells. The most common solar cells are made from silicon, a semiconductor that is the second most abundant element on Earth. In a solar cell, crystalline silicon is sandwiched between conductive layers. Each silicon atom is connected to its neighbors by four strong bonds, keeping the electrons in place and restricting current flow.
Here's the key: A silicon solar cell uses two distinct layers of silicon. An n-type silicon has extra electrons, and p-type silicon has extra spaces for electrons, which we'll call holes. Where the two types of silicon meet, electrons can wander across the p/n junction, leaving a positive charge on one side and creating negative charge on the other.
You can think of light as the flow of tiny particles called photons shooting out from the sun. When one of these photons strikes the silicon cell with adequate energy, it can knock an electron from its bond, leaving a hole. The negatively charged electron and location of the positively charged hole are now free to move around. But because of the electric field at the p/n junction, they'll only go one way. The electron is drawn to the n-side, while the hole is drawn to the p-side.
The mobile electrons are collected by thin metal fingers at the top of the cell. From there, they flow through an external circuit, doing electrical work, like powering a lightbulb. Then they return through the conductive aluminum sheet on the back. Each silicon cell only puts out half a volt, but you can string them together in modules to get more power. Twelve photovoltaic cells are enough to charge a cell phone, while it takes many modules to power an entire house.
Electrons are the only moving parts in a solar cell, and they all go back where they came from. There's nothing to get worn out or used up, so solar cells can last for decades.
So what's stopping us from being fully reliant on solar power?
The most obvious of those is that solar energy is distributed across the planet unevenly. Some areas are sunnier than others. The distribution is also inconsistent over time. Less solar energy is available on cloudy days, at night or in the winter. So a total reliance would require efficient ways to get electricity from sunny to cloudy locations through effective storage of energy.
The efficiency of the cell itself is a challenge, too. If sunlight is reflected instead of absorbed, or if dislodged electrons fall back into a hole before going through the circuit, that photon's energy is lost. Most commercial systems currently hover around 15-25% efficiency.
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