Solar panel
🏷️ Tào lao
A: What is a solar panel made of?
B: Solar panel is made 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
A: What is the role of silicon in the solar cell?
B: In a solar cell, crystalline silicon is sandwiched between conductive layers. Each silicon atom is connected to its neighbors by four strong bonds, which keep the electrons in place. So no current can flow. Here’s the key, a silicon solar cell uses two different layers of silicon. An N-type silicon has extra electrons and P-type silicon has extra spaces for electrons, called 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 a negative charge on the other
A: I still don’t understand. Could you explain more?
B: You can think of light as a flow of tiny particles called protons shooting out from the Sun. When one of these protons strikes the silicon cell with enough energy, it can knock an electron from its bond, leaving a hole. The negatively charged electron and the location of the positively charged hole are now free to move around
A: Where do they go?
B: Because of the electric field at the P/N junction, they only go one way. The electron is drawn to the N side while the hole is drawn to the P side.
A: How do these moving electrons create electricity for usage?
B: 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 before returning through the conducted aluminum sheet on the back
A: How much power does a silicon cell produce?
B: Each silicon cell only puts out half of a volt
A: How can the silicon cell can create a large amount of power?
B: You can string them together in modules to get more power
A: Is this power depleted completely?
B: No, electrons are the only moving parts in a solar cell and they all go back where they came from. There is nothing worn out or used up, so solar cells can last for decades
A: So what’s stopping us from being completely reliant on solar power?
B: There are political factors at play, not to mention businesses that lobby to maintain the status quo. But for now, let’s focus on the physical and logistical challenges and the most obvious of those is that solar energy is unevenly distributed across the planet. Some areas are sunnier than others. It’s also inconsistent. Less solar energy is available on cloudy days or at night. So a total reliance would require efficient ways to get electricity from sunny parts to cloudy ones and effective storage of energy. The efficiency of the cell itself is a challenge too
A: Why is that?
B: If sunlight is reflected instead of absorbed or if dislodged electrons fall back into a hole before going to the circuit, that proton energy is lost. The most efficient solar cell yet still only converts 46% of the available sunlight to electricity, and most commercial systems are currently 15-20% efficient
A: So is it possible for us to rely completely on solar power?
B: In spite of the limitations, it actually would be possible to power the entire world with today’s solar technology
A: What should we do?
B: We would need the funding to build the infrastructure and a good deal of space, estimates range from tens to hundreds of thousands of square miles
A: That’s a lot
B: It seems like a lot, but the Sahara desert alone is over three million square miles in area. Meanwhile, solar cells are getting better, and cheaper, and are competing with electricity from the grid. Innovations like floating solar farms may change the landscape entirely