Solar Energy

A photovoltaic cell is built from a semiconductor, usually silicon, treated so one layer has extra free electrons and the other has gaps for electrons, called holes. When a photon of enough energy hits the cell, it knocks an electron loose from an atom, leaving a hole behind. The built-in electric field at the junction between the two layers pushes the freed electron one way and the hole the other, so instead of the electron just falling back into place, it gets shoved out into a wire. That flow of electrons through the external circuit is the current. A cold clear day beats a hot hazy one because output depends on light intensity hitting the cell, not temperature; haze scatters and blocks photons, while heat actually makes silicon slightly less efficient.

Concentrated solar power skips photovoltaic cells entirely. Curved mirrors, often arranged in a huge circular field, track the sun and focus its light onto a central tower or pipe filled with molten salt. The salt absorbs the concentrated heat and climbs to several hundred degrees Celsius. That heat boils water into steam, which spins a turbine exactly like in a coal or nuclear plant. Because molten salt holds heat for hours, the plant keeps generating electricity after sunset, something photovoltaic panels cannot do without a separate battery.

Both methods sit in the renewable column alongside wind and hydro: no fuel burned, no combustion emissions, but real costs in land use, manufacturing, and the materials used to build panels, mirrors, and storage tanks. The energy math that follows, converting rated wattage and sun hours into actual daily energy, is how this cost gets compared fairly against fossil and nuclear sources on a kilowatt-hour basis.