Hopewell Valley Student Podcasting Network
Light Up Our World
Welcome to Chemistry Connections, my name is Sarah and I'm Akhansha and we are your hosts for episode #1 called “Light Up Our World”. Today we will be discussing the chemistry behind solar panels.
Segment 1: Introduction to Solar Panels
Solar panels are an alternative, renewable energy source that have gained popularity in recent years. In this episode, we will be explaining how solar panels receive light and produce electricity. But why are solar panels important? Electricity runs the modern world, being necessary for almost all of our daily activities. However, in this day and age, the source of electricity is just as important as electricity itself. *cough* Climate change *cough*. Solar panels provide an alternative pathway to gain energy without harming our world like other sources of electricity.
Segment 2: The Chemistry Behind TOPIC
So how do solar panels convert light into electricity? Solar panels are made of two types of semiconductors: P-type and N-type. Before we elaborate, we’d like to clarify what a semiconductor is. A semiconductor is a substance that has electrical conductivity between that of a conductor and an insulator. On the periodic table, elements that are semiconductors are silicon, germanium, tin, selenium, and tellurium.
The P-type layer is placed next to the N-type layer. In the P-type layer, atoms with one less electron in the outer shell compared to silicon, like boron and gallium, are added. This absence of an electron is referred to as a “hole” that is positively charged. In the N-type layer, atoms, like phosphorus, that have one more electron in the outer shell than silicon, are added. This creates an excess of electrons in the N-type layers since one electron is free to roam after phosphorus bonds with neighboring silicon atoms.
- Electrons in n-type layer travel to vacancies in p-type layer
- Depletion zone - area around junction between p-type and n-type layers where electrons fill holes
- When holes are filled in the depletion zone…
- Negatively charged ions in p-type part of depletion zone
- Positively charged ions in n-type part of depletion zone
- Internal electric field created that prevents more electrons from n-type layer from filling holes in p-type layer
- Sunlight ejects electrons from silicon, creating more holes
- Electrons are attracted to positive silicon nuclei (opposite charges attract)
- Energy is needed to break the attractive force between electrons and silicon nuclei
- Electrons closer to silicon nuclei will be harder for sunlight to eject (Coulomb’s law)
- Sunlight must have enough energy to remove electrons from silicon atoms
- Different types of solar radiation have different energies
- Higher-energy solar radiation (higher frequency light waves) may be more capable of ejecting electrons
- Solar radiation
- Also called electromagnetic radiation
- Light emitted by the sun
- the amount of solar radiation that reaches any one spot on the Earth’s surface varies based off of location, time of day, season, local landscape and local weather
- Solar radiation is captured and is turned into useful forms of energy
- Harder to remove electrons from elements neart the top right of the periodic table (increased Zeff, fewer E-levels)
- Ejection in electric field → field moves electrons to n-type layer and holes to p-type layer
- If n-type and p-type layers are connected with a wire, electrons travel from n-type layer to p-type layer by crossing depletion zone and then through wire out of n-type layer → electricity
- Two main types of solar energy technology: Photovoltaics (PV) and Concentrating Solar-Thermal Power (CSP)
- When the sun shines onto a solar panel, energy from the sunlight is absorbed by the PV cells in the panel
- This energy creates electrical charges that move in response to an internal electrical field in the cell, causing electricity to flow
- Concentrating Solar-Thermal power
- CSP systems use mirrors to reflect and concentrate sunlight onto receivers
- Receivers collect solar energy and convert solar energy to heat energy
- Heat energy can then be converted into usable electricity or can be stored for later use
Segment 3: Personal Connections
- Solar energy is becoming an increasingly popular form of energy
- Some government programs allow people to save money by switching to solar energy
- Door-to-door solar panels sales reps begging people to switch to solar
- Power outages wouldn't be an issue with solar panels
- Sarah made a solar-powered phone charger in eighth grade
- Climate change sucks
Thank you for listening to this episode of Chemistry Connections. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.
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