Here Comes the Sun

Sunlight: From Space to Your Roof

Person soaking up midday sun in a green backyard, showing how solar energy reaches everyday spaces.

Imagine a clear day in your backyard. You feel the warmth of sunlight on your skin. That warmth is solar radiation—energy that travels 93 million miles from the sun to Earth.

Every second the sun sends about 173 000 terawatts of power toward our planet. Humanity uses roughly 18 terawatts at any given moment, so one hour of sunshine could supply a year of global energy needs.

The Sun’s Gift: What Solar Radiation Really Means

Split view of bright sky and hazy city, highlighting how weather and air quality change sunlight.

The quality and timing of sunlight vary. Clouds, seasons, and pollution all influence how much energy reaches the ground.

Across the United States, daily solar energy ranges from 4 to 7 kilowatt-hours per square meter. Arizona and Nevada enjoy abundant rays, while Seattle gets far less, yet usable sunlight still falls everywhere.

Two Ways to Catch a Ray: PV vs. Solar-Thermal

Rooftop photovoltaic panels at sunrise, symbolizing direct solar-to-electric conversion.

Humans capture sunlight in two main ways. First, photovoltaic (PV) panels convert light straight into electricity—ideal for roofs, schools, and calculators.

Field of parabolic mirrors in desert, illustrating large-scale solar-thermal power.

Second, solar-thermal systems use the sun’s heat to warm fluids. The hot fluid makes steam, spins turbines, or heats buildings. PV suits small spaces but loses efficiency when hot; solar-thermal excels at large scales yet needs more maintenance.

Efficiency: How Much Do You Really Get?

Engineer with tablet beside vast solar array, emphasizing real-world panel performance.

A typical silicon PV panel captures about 20 percent of incoming light. Large solar-thermal plants can reach roughly 40 percent. Even those modest numbers add up quickly because sunlight is plentiful.

Inside a Solar Cell: Feynman’s Photoelectric Effect

Microscopic silicon lattice with bouncing photons and flowing electrons, visualizing the photoelectric effect.

A photon strikes silicon and frees an electron. Engineers build an electric field that guides these electrons in one direction, creating current without moving parts.

Retro-futuristic lab scene showing scientist observing electrons knocked free by light.

Einstein explained this photoelectric effect and won the Nobel Prize for it. Each solar panel repeats the process millions of times per second, turning sunlight directly into usable power.

Why Silicon? Simple Chemistry, Big Results

Playful diorama of cooking silicon wafers, underscoring the element’s abundance and usefulness.

Silicon is the world’s second-most common element and is easy to refine. Its ideal band gap and ability to be doped with impurities make it both affordable and efficient for solar cells.

Sunlight travels from the solar core to your roof in eight minutes. Thanks to decades of research and clever engineering, we now capture that light and turn it into clean energy—every day, wherever the sun shines.