Write any two sources of electrical energy.

Hydroelectric power plants harness the natural flow of water to produce electricity, a process that has been instrumental in meeting the world's energy needs. These facilities take advantage of the kinetic energy carried by large volumes of moving water, typically from rivers or reservoirs. Here's how they operate: water flows through turbines, causing them to spin, which in turn activates generators to produce electricity. This renewable form of energy is esteemed for its relatively low emissions of greenhouse gases, especially when compared to fossil fuel-based power plants. Moreover, the infrastructure built for hydroelectric facilities, such as dams and reservoirs, can also provide additional benefits such as water storage for irrigation and flood control.

Solar panels are becoming an increasingly familiar sight on rooftops and in solar farms worldwide. They capture sunlight, a plentiful and renewable resource, and convert it directly into electricity. This is made possible by an array of solar cells composed mainly of silicon. Each cell works by absorbing photons from sunlight, which in turn frees electrons in the silicon, generating a flow of electric current. Solar panels are a clean and sustainable alternative to traditional energy sources, reducing reliance on fossil fuels and decreasing the carbon footprint associated with energy consumption.

At the heart of every solar panel is the photovoltaic effect, a physical and chemical phenomenon that converts light into electrical energy. This remarkable process occurs when materials such as silicon absorb photons, which carry energy from sunlight. The interaction between the photons and the silicon material causes electrons to become excited and jump from their atomic orbits, leaving behind what we call 'holes.' The electron-hole pairs are then separated by an internal electric field within the photovoltaic cell, creating voltage. When an external circuit is connected to a solar panel, this voltage drives an electrical current, powering our homes and devices with energy harnessed from the sun.

Renewable energy sources include wind, solar, hydro, and geothermal power among others. These sources are considered 'renewable' because they are naturally replenished on a human timescale. Unlike finite fossil fuels, such as coal and oil, renewable resources are less likely to run out. By transitioning to renewables, we can reduce the environmental impact associated with traditional forms of energy. This shift not only helps in mitigating air pollution and decreasing greenhouse gas emissions but also promotes energy security and fosters sustainable economic growth through the creation of 'green' jobs in the renewable energy sector.