Solar energy

The Sun gives us light and heat.

The Sun gives us light and heat. This is called solar energy.

Humans use many ways to catch solar power. We use active solar tools. These tools use machines like pumps or fans. One way is using photovoltaics. These are parts that turn light into power. We can also use solar thermal energy. This is a way to use heat. It can heat water for our homes. Some buildings use passive solar ways. They use special parts to stay warm. They might use stone to store heat. We call this thermal mass. This helps keep a room at a good temperature.

Solar energy is the light and heat that comes from the Sun. This energy is a renewable resource, which means it will not run out. We can use it to make electricity or to heat our homes. Scientists divide solar methods into two main groups. Active solar uses machines like pumps or fans to move energy. Passive solar uses smart building designs to catch heat naturally.

The way solar energy works starts when sunlight hits our planet. The Earth receives 174 petawatts of solar radiation at the top of the atmosphere. About 30% of this light bounces back into space. The rest is absorbed by the land, the clouds, and the oceans. The oceans cover about 71% of our globe. This absorbed energy keeps the Earth's surface at an average temperature of 14 °C.

People have worked to catch this energy for a long time. In 1878, Augustin Mouchot showed a solar steam engine in Paris. Later, an inventor named Frank Shuman built a solar engine in 1897. He used boxes filled with ether to catch the heat. By 1912, he patented a system that used water instead. Shuman built the first solar thermal power station in Maadi, Egypt. His plant used special troughs to pump water from the Nile River.

There are many amazing numbers tied to solar power. In 2002, the energy hitting Earth in one hour was more than the world used in a year. To get all our energy from the sun, we would need 450,000 square kilometers of land. That is about the same size as the country of Sweden. China is currently the world leader in solar hot water systems. They have 309 gigawatts of these systems installed.

You can see solar energy working in many everyday things. Solar water heaters use the sun to make warm water for showers. Some buildings use thermal mass, like stone or cement, to store heat. This helps keep rooms at a comfortable temperature. You can even use trees to help manage heat. Deciduous trees have leaves in summer to provide shade. In winter, their bare limbs let the sunlight pass through to warm the building.

Solar energy is the radiant energy received from the Sun's light and heat. It is a vital renewable resource because it is inexhaustible and clean. We can harness this energy through various technologies to create electricity or thermal energy. Scientists categorize these technologies into two main groups: active solar and passive solar. Active solar techniques use mechanical devices like pumps, fans, or photovoltaic systems to capture and distribute power. Passive solar techniques focus on design, such as using specific building materials or natural air circulation.

The process begins when solar radiation reaches the Earth's upper atmosphere. The Earth receives approximately 174 petawatts (PW) of this incoming radiation, also called insolation. About 30% of this light is reflected back into space. The remaining 122 PW is absorbed by the atmosphere, the land, and the oceans. Since oceans cover about 71% of the globe, they absorb a massive amount of this energy. This absorbed sunlight keeps the Earth's average surface temperature at 14 °C.

This absorbed energy drives many natural cycles on our planet. As the oceans and land warm up, the air above them also warms. This warm air contains evaporated water and begins to rise. This process is known as convection, or atmospheric circulation. When this air reaches high, cold altitudes, the water vapor condenses into clouds. This eventually leads to rain, completing the water cycle. The heat released during condensation can even amplify convection to create winds and cyclones.

Humans have been exploring solar technology for over a century. In 1878, Augustin Mouchot demonstrated a solar steam engine in Paris. Later, an inventor named Frank Shuman developed a solar engine in 1897. His early version used boxes filled with ether to capture heat. By 1912, he improved this system to use water instead. Shuman even built the world's first solar thermal power station in Maadi, Egypt. His plant used parabolic troughs to pump water from the Nile River to cotton fields.

The scale of solar energy is truly enormous. In 2002, the amount of solar energy hitting Earth in just one hour was more than the entire world used in a year. Specifically, the Earth absorbs about 3,850,000 exajoules (EJ) of solar energy every year. Plants also play a role through photosynthesis, converting solar energy into biomass. This process captures about 3,000 EJ of energy per year. While the potential is huge, we are limited by geography, cloud cover, and available land.

Solar thermal technology is a major way we use this energy today. These systems can provide heat for water, buildings, and industrial processes. Solar water heaters are very common, especially in middle latitudes. They include evacuated tube collectors, glazed flat plate collectors, and unglazed plastic collectors. China is the global leader in this field, with 309 gigawatts of installed capacity. In places like Israel and Cyprus, over 90% of homes use solar hot water systems.

We can also use solar energy to manage the temperature of our homes. One method is using thermal mass, which involves materials like stone, cement, or water. These materials absorb heat during the day and release it when it is cooler. Another method is the solar chimney, a vertical shaft that uses rising warm air to circulate air through a building. Even planting deciduous trees can help. Their leaves provide shade in the summer, but their bare branches let sunlight through in the winter.

Solar energy is connected to almost every other form of renewable energy. Aside from geothermal and tidal power, most renewables come from the Sun, either directly or indirectly. The International Energy Agency notes that developing affordable solar technology provides huge benefits. It can increase energy security by using local, inexhaustible resources. It also helps reduce pollution and lowers the costs of mitigating global warming. As technology improves, solar energy remains a key part of a sustainable future.