The history of solar power dates back to some of the earliest civilizations, which used magnifying glasses to concentrate the sun’s rays to light fires. However, solar power in today’s context is often traced back to the discovery of the photovoltaic effect, first observed by French physicist Alexandre-Edmond Becquerel in 1839.

Becquerel discovered that when a semiconductor material such as platinum or silver is exposed to solar radiation, an electrical current is formed. In the 1880’s, Charles Fritts expanded on Becquerel’s work by creating the first solar cell. Several scientists championed solar energy work until a breakthrough in 1954, when Bell Labs developed the first silicon photovoltaic cell. Today, photovoltaics is the most common way to harness solar energy.

Solar power is made possible by nuclear reactions happening at the Sun’s core. Hydrogen protons violently collide and fuse together to create helium, producing massive quantities of energy. This energy radiates from the sun out into the solar system through a spectrum of electromagnetic waves, otherwise known as electromagnetic radiation.

Solar energy plays a crucial role in creating and sustaining life on Earth. The greenhouse effect, for instance, is a phenomenon in which solar energy is absorbed by the Earth’s surface and radiated back into the atmosphere. Greenhouse gasses like water vapor and carbon dioxide trap the heat, creating a layer of insulation that keeps the planet warm and livable. Nearly all living creatures rely on solar energy, whether directly, through processes like photosynthesis, or indirectly as members of the food chain.

On Earth, solar photovoltaic (PV) and concentrated solar power (CSP) systems are used to convert sunlight into other forms of energy, such as electricity and thermal energy.

Solar PV uses the photovoltaic effect, the generation of voltage upon exposure to light, to create electricity. A solar panel or module is a common example of a photovoltaic system as it can house an array of photovoltaic cells (or solar cells). The number of PV cells can range from one to hundreds on a single PV panel.

Each PV cell contains a semiconductor that is made of silicon or other semiconductor materials that are used to create an electrical field. As sunlight is absorbed, electrons are knocked loose from the semiconductor and swept up in an electrical current moving toward an external device. This flow of energy is considered a direct current (DC), generating electricity proportional to the amount of sunlight received. The DC electricity can be converted to an alternating current (AC) through solar inverters, which allow for AC electricity to be produced at a set voltage.

Electricity that is generated by a solar panel system can be immediately used. Excess energy can be stored in a solar battery or sent to the electrical grid. Homeowners can receive energy credits on their electric bill in exchange for their solar array contributions. This is done through net metering. PV systems are the most common conversion method for smaller-scale applications and can be used for something as simple as powering a calculator. However, they can also be scaled for greater electricity generation. Some PV power stations can provide energy for entire towns.

Concentrated solar power (also called concentrated solar thermal power) uses mirrors to reflect and gather sunlight onto fluid-filled receivers. Solar heating raises the temperature of the fluid, generating thermal energy through hot water. The energy is used to power engines or spin turbines, which then generate electricity that flows to power plants or supplement electrical grids.

Typically, CSP is used for large-scale utility and industrial applications. Solar power plants, for instance, can produce hundreds of megawatts (MW) of electrical energy each year through CSP systems. However, CSP can also be used on a smaller scale for devices like solar cookers.

Both PV and CSP systems are considered active solar energy systems since they use solar technologies to directly produce energy.

Passive energy systems instead use sustainable design approaches like solar architecture to take advantage of the natural heating and cooling of the Earth. As the sun warms the Earth throughout the day, building materials such as wood, metal, and glass absorb the solar energy. When the sun sets and the atmosphere cools, the building materials emit their stored heat through conduction, convection, and radiation.

Architects and engineers can use this exchange of heat to create efficient and inexpensive solutions to heat and cool buildings. For instance, they may paint a roof white to reflect the sun’s energy or install a solarium to naturally heat parts of a building.

Several solar power advancements are taking shape across the international regulatory, business, and technology landscape. In the United States, the Department of Energy is working closely with the Biden administration to reduce hurdles for energy storage and improve decarbonization efforts. This comes at a time when states like California and Nevada—where tax credit incentives reward homeowners for going solar—face a unique issue: solar companies are having their energy needs exceeded by an excess of solar installations. 

In India, Adani Green Energy commissioned 1 gigawatt (GW) of solar power at the Khavda solar PV park in the state of Gujarat—a crucial step on its journey to building 30GW of capacity.² Meanwhile, UK-based Lightsource is developing a 560 MW solar PV park in Greece which will become the second-largest solar park in Europe, a title that is currently held by Witnitz solar park in eastern Germany.³

Solar-powered refrigerators are helping to fight malaria outbreaks in Africa by storing vaccines at a safe temperature.⁴ In Japan, plans are underway to beam solar energy straight from space down to Earth by 2025.⁵ These innovations are made possible by the shrinking cost of solar power, which has dropped by 90% in the last decade, and developments in energy storage systems.⁶