The sun's nuclear fusion process is the source of its renewable energy. Hydrogen atoms at the sun's core smash so furiously that their protons fuse, creating helium.

Known as a PP (proton-proton) chain reaction, this mechanism releases tremendous amounts of energy. Every second, the sun's core fuses around 620 million metric tons of hydrogen. Stars similar in size to our sun engage in the PP chain reaction, which provides them with a steady supply of energy and heat. These stars have temperatures of roughly 4 milion Kelvin (about 4 milion Celsius or 7 milion Fahrenheit).

CNO cycle causes energy production in stars around 1.3 solar radii in diameter. Carbon, nitrogen, and oxygen (C, N, and O) are used in the CNO cycle, which also transforms hydrogen to helium. The CNO cycle now generates less than 2% of the sun's energy.

Massive amounts of energy in the form of waves and particles are released during nuclear fusion via the PP chain reaction or the CNO cycle. Energy from the sun is constantly being dispersed across the solar system. Solar energy warms the planet, drives weather and wind, and keeps all living things alive.

The sun's electromagnetic radiation (EMR) carries away its energy, heat, and light.

Different frequencies and wavelengths make up the electromagnetic spectrum. The number of times a wave is repeated in a given amount of time is its frequency. Very short-wavelength waves are high-frequency because they have a high repetition rate. Longer wavelengths characterize low-frequency waves.

Most electromagnetic waves travel undetected by our senses. The sun's highest-frequency radiation is made up of gamma rays, X-rays, and UV rays. The atmosphere of Earth absorbs nearly all of the sun's ultraviolet (UV) rays. Sunburns can be caused by the passage of weaker UV rays through the atmosphere.

Infrared light, with its much lower frequency, is another type of energy the sun generates. Infrared light is the primary form of solar heat.

The visible spectrum, between infrared and ultraviolet, is where all the colors we perceive on Earth are located. The wavelengths of the colors red (closest to infrared) and violet (closest to UV) are the longest and shortest, respectively.

Renewable Solar Power

The Cause and Consequences of the Greenhouse Effect
Reaching the Earth, infrared, visible, and ultraviolet radiation all contribute to a process that warms the planet and allows life to exist; this is known as the "greenhouse effect."

Solar energy that reaches Earth is reflected back into space at a rate of about 30 percent. The rest is swallowed up by the atmosphere of our planet. The surface of the planet is warmed by the radiation, and then some of that heat is radiated back into space as infrared light. As they ascend, greenhouse gases like water vapor and carbon dioxide block their path.

The heat that is reflected back up into the sky is trapped by the greenhouse gases. They function much like the glass walls of a greenhouse in this respect. The planet stays habitable because of the greenhouse effect.

Photosynthesis
Solar energy is essential for the survival of nearly every living thing on Earth.

Solar power is used only by manufacturers. Through photosynthesis, plants take up light and transform it into food. Plants, algae, bacteria, and fungi are all examples of producers, often known as autotrophs. The autotrophs support all other organisms in the food chain.

Nutritional support comes from producers to consumers. Indirectly, the sun provides energy for herbivores, carnivores, omnivores, and detritivores. Plants and other producers are the main course for herbivores. Both producers and herbivores are fair game for carnivores and omnivores. Detritivores are animals that eat dead organisms and plants.

The Use of Fossil Fuels
All fossil fuels on Earth can be traced back to photosynthesis. Autotrophs are thought to have originated in aquatic environments some 3 billion years ago. Plants were able to grow and adapt thanks to the sun's rays. When autotrophs died, their bodies decayed and moved hundreds or even thousands of meters underground. For countless eons, this cycle remained unbroken.

Fossil fuels are the result of these remains being subjected to extreme heat and pressure. Petroleum, natural gas, and coal originated from microorganisms.

Humans have figured out how to get at these fossil fuels and turn them into useful energy sources. However, fossil fuels are a finite resource and can't be replaced. It takes millions of years for them to mature.

Using the Sun's Power

Solar energy is a renewable resource, and it may be harvested directly by a variety of technologies that can then be used to power buildings like homes, stores, and even medical facilities. Photovoltaic cells and panels, concentrated solar power, and solar-powered buildings are all examples of solar energy technologies.

Various techniques exist for collecting sunlight and transforming it into usable energy. The techniques can be classified as either active or passive solar energy systems.

Technologies that actively transform solar energy into another kind of energy, typically heat or electricity, are known as "active solar technologies." No additional components are required for passive solar technology to function. Instead, they use the weather to their advantage, heating up buildings in the winter and cooling them down in the summer.

Photovoltaics

Alexandre-Edmond Becquerel, a 19-year-old French physicist, devised photovoltaics, a type of active solar technology, in 1839. Silver chloride in an acidic solution, when exposed to sunlight with platinum electrodes attached, produced an electric current, as Becquerel observed. The term "photovoltaics" refers to the technology that uses sun energy to create electricity.

The most common method used to collect solar energy nowadays is photovoltaics. The solar panels that make up most photovoltaic arrays are essentially collections of solar cells.

A semiconductor, often silicon, is housed within each solar cell. The semiconductor releases electrons when exposed to light. These free electrons are shaped by an electrical field into a unidirectional current. A solar cell's current flows out of the device through metal contacts at its top and bottom. A solar-powered calculator is one example of an external item; a power plant is another.

The first widespread application of photovoltaics was aboard spacecraft. Wide "wings" of solar panels act as reflection surfaces on many satellites, including the International Space Station. Two solar array wings (SAWs) use over 33,000 solar cells each to power the International Space Station. All electricity used by the International Space Station comes from these solar cells, making it possible for astronauts to run the station, live in space for months at a time without risk, and perform scientific and engineering studies.

There are now photovoltaic power plants in every continent. Major hubs can be found in the USA, India, and China. Hundreds of megawatts of electricity are produced by these power plants and distributed to homes, businesses, schools, and hospitals.

It is possible to implement photovoltaics on a smaller scale. Electricity for buildings can be generated via solar panels and cells that are mounted on the roof or outside walls. Highways can be illuminated by placing these along the routes. Calculators, parking meters, trash compactors, and even water pumps can all be powered by solar cells because of their miniscule size.

Solar Power Concentration

Concentrated solar power (CSP) is another form of active solar technology. Focusing sunlight from a wide region onto a compact surface is the goal of Concentrating Solar Power (CSP) technology. A fluid is heated by this concentrated radiation source, which then powers an electric generator or powers some other operation.

Concentrated solar energy is used in solar furnaces, for instance. Solar furnaces come in a wide variety of designs, including as parabolic troughs, Fresnel reflectors, and solar power towers. The basic principle of energy collection and transformation is the same.

Heliostats are used on solar power towers; they are flat mirrors that rotate to track the sun's path across the sky. The mirrors are positioned in a circle around a "collector tower," focusing the sun's rays on a single point on the tower.

Traditional solar power towers focused sunlight into a water tank, where the resulting steam turned a turbine to generate electricity. Liquid sodium, which has a higher heat capacity and maintains heat for a longer period of time, has lately been used in some solar power towers. This means that the fluid may boil water and produce energy even when the sun is not shining, with temperatures ranging from 773 to 1,273 K (500 to 1,000° C or 932 to 1,832° F).

CSP is also used in parabola troughs and Fresnel reflectors, however the mirrors in these devices are structured differently. Curved like a saddle, parabola mirrors are used to reflect light in all directions. Fresnel reflectors are devices that concentrate sunlight onto a tube of liquid by using flat, thin strips of mirror. With their larger surface area, Fresnel reflectors may magnify the sun's rays by a factor of 30 or more.

It wasn't until the 1980s that the first concentrated solar power facilities appeared. The plants in the Mojave Desert in California make up the world's largest facility. More than 650 terawatt-hours of electricity per year are produced by this solar power plant. Spain and India have also created huge, efficient plants.

Small-scale applications of concentrated solar electricity are feasible. It can be used to produce heat for solar cookers. Solar cookers are used to boil water for sanitation and cooking food in rural areas of the world.

Compared to wood-burning stoves, solar cookers reduce habitat loss in forests since fewer trees need to be cut down to provide fuel. They are also safer and emit no smoke. Having a solar cooker means less time spent gathering firewood, which means more time for other activities like school, work, or family. Chad, Israel, India, and Peru are just a few of the places where you can find people using solar cookers.

Engineering of the Sun

Solar energy contributes to thermal convection, the transfer of heat from a warmer to a cooler region, throughout the course of a day. As soon as the sun comes up, it starts warming up the Earth and everything on it. These substances retain heat from the sun all day long. After the sun goes down and the air cools, the materials give up their heat to the atmosphere again.

Utilizing passive solar energy methods, one can harness the sun's heating and cooling potential.

Passive solar energy is used to heat and cool homes and other buildings. One such application is determining the "thermal mass" of a structure. The thermal mass of a building is its capacity to store heat generated during the day. Thermal mass can be anything from wood to metal to concrete to clay to stone to mud. The thermal mass radiates heat back into the space at night. The heated air is dispersed by corridors, windows, and air ducts, keeping the internal temperature constant and comfortable.

The use of passive solar technologies is commonplace in architectural planning. For optimal lighting, an engineer or architect could plot the building's location in relation to the sun's daily course before construction ever begins. This approach considers the location's latitude, altitude, and typical cloud cover. Insulation, thermal mass, and supplemental shading are further measures that can be taken during building construction or as a retrofit.

Cool roofs, radiant barriers, and green roofs are a few other examples of passive solar design. White roofs are cooler because they reflect the sun's rays rather than absorbing them. As less heat is transmitted through the white surface, less cooling power is required to maintain a comfortable interior temperature.

Like cool roofs, radiant barriers help reduce heat gain. Insulation is provided by highly reflecting materials like aluminum foil. The foil acts as a heat mirror, reflecting radiant energy rather than absorbing it. Radiant barriers aren't just for ceilings and attics; they can also be set up in the space between floors.

The term "green roof" refers to rooftops that are planted in their entirety. They need a layer of soil and water to grow, as well as protection from the elements. Green roofs not only provide vegetation but also minimize the amount of heat absorbed or wasted by a building. Plants on green roofs remove carbon dioxide from the air and release oxygen as a byproduct of photosynthesis. They clean the air and water from pollutants and even out the impact of the energy used in the area.

Since the Middle Ages, green roofs have been common in Scandinavia. Recently, they've gained popularity in other parts of the world, including Australia, Western Europe, Canada, and the United States. Ford Motor Company, for instance, planted 42,000 square meters (450,000 square feet) of greenery on the roofs of their assembly plant buildings in Dearborn, Michigan. The roofs absorb several centimeters of rainfall, which decreases stormwater runoff and helps cut down on greenhouse gas emissions.

The "urban heat island" effect can also be mitigated by installing green roofs or cool roofs. Consistently rising temperatures are not uncommon in crowded cities. Cities retain heat because of their built environment (asphalt and concrete, for example), tall buildings reduce the cooling effects of wind, and a large quantity of waste heat is produced by the city's industry, transportation, and population. Trees planted on rooftops or white roofs that reflect the sun's rays can help mitigate the effects of urban heat islands.

Solar Power and Humans

Since most of the world only sees sunlight for approximately half the day, solar energy devices need to incorporate ways to store the energy for use at night.

Paraffin wax or different types of salt are used in thermal mass systems to store the energy as heat. Excess energy generated by photovoltaic systems can be sent back into the grid or stored in rechargeable batteries.

Solar energy has many benefits and drawbacks.

Advantages
The fact that solar energy may be replenished over and over again is a big pro for its use. Sunlight will continue to shine for the next 5 billion years. An entire year's worth of solar energy for every person on Earth is absorbed by Earth's atmosphere in just one hour.

Renewable and non-polluting, solar power is the future. Once the infrastructure for solar technology is in place, it does not require any additional fuel to function. Neither greenhouse gases nor harmful substances are released. Using solar energy can lessen our ecological footprint significantly.

There are places where using solar power makes sense. The abundant solar energy can be used to power homes and buildings in locations with plenty of sunshine and little cloud cover.

In a world where 2 billion people still use wood for cooking, solar cookers are a welcome innovation. Cleaner and safer water and food can be prepared using solar cookers.

Solar energy is a great addition to other renewable energy sources like wind and hydro.

If solar panels are installed on a building and function properly, the building or home may even generate too much power. These property owners or business proprietors can offset or even eliminate their electricity costs by selling excess energy to the utility company.

Disadvantages
Getting the necessary equipment to harness solar energy is the biggest obstacle. The cost of solar technology equipment is high. The equipment can cost tens of thousands of dollars to buy and install in a single home. Although solar energy users can benefit from tax breaks and no longer having to pay for their electricity, the upfront cost is prohibitive for many.

Heavy solar energy equipment is another drawback. Roofs that are robust, large, and oriented toward the sun's path are ideal for retrofitting or installing solar panels.

Climate and cloud cover are two examples of uncontrollable environmental factors that affect the efficiency of both active and passive solar technologies. Studying local locations is necessary to establish the viability of solar electricity.

Solar energy is most practical when there is ample, reliable sunlight. The inconsistency of solar energy makes it impractical as a primary power source in the vast majority of the Earth's inhabited regions.

QUICK IDEA

Warm Water
The largest collection of photovoltaic panels is located near Yuma, Arizona at the Agua Caliente Solar Project. More than 600 gigawatt-hours of electricity are produced by the solar modules at Agua Caliente, which number in excess of 5 million.

QUICK IDEA

Chicago that's good for the environment
The green roof in Chicago's Millennium Park is one of the largest in the world, covering over a million square feet. Gardens, picnic spots, and an outdoor music venue are just some of the features that make up the 24.5 acres of vegetation above ground in an underground parking garage.