The Sun as an Energy Source

The Sun provides most of the energy that powers life and many of our energy resources. Its energy reaches Earth as electromagnetic radiation, mainly infrared (heat), visible light, and some ultraviolet.

How the Sun makes and sends energy

Inside the Sun, nuclear fusion joins hydrogen into helium and releases large amounts of energy.

In simple form: $\text{hydrogen} \rightarrow \text{helium} + \text{energy}$. This energy travels to Earth as radiation and warms the land, air, and oceans.

How sunlight drives our energy resources

• Solar cells (photovoltaic): light makes electrons move, producing electrical power.
• Solar thermal panels: sunlight heats water for washing and heating.
• Wind energy: the Sun heats Earth unevenly, creating moving air (wind) that turns turbines.
• Hydroelectric power: sunlight drives the water cycle (evaporation, clouds, rain); water stored behind dams spins turbines.
• Wave energy: winds transfer energy to the sea surface, creating waves.
• Biofuels and fossil fuels: plants use sunlight to store chemical energy; biofuels come from recent plants, fossil fuels from ancient plants.

In wind, hydro, and wave power, moving air or water turns a turbine connected to a generator to produce electricity.

Not from the Sun: geothermal (heat from inside Earth), nuclear fission in power stations, and tides (mainly caused by the Moon).

Advantages and limitations of solar-powered resources

• Renewable and widespread; no fuel cost and low air pollution during use.
• Variable: depends on time of day, seasons, and weather; storage or backup is needed.
• Space needed for panels, farms, or reservoirs; local wildlife and landscapes can be affected.

Common misconceptions

• Solar panels need light, not heat; they can work in cold places.
• Clouds reduce output but do not always stop it.
• Wind, waves, hydro, and biofuels are indirect forms of solar energy.
• Tidal energy is not solar; it is mainly due to the Moon’s gravity.