In this blog post, let’s explore how solar power converts sunlight into electrical energy, how it’s used in our daily lives, and what challenges must be overcome for it to become a major energy source in the future.
Fossil fuels have long been the most widely used energy source for producing the electricity we need most in our daily lives. However, the use of fossil fuels causes various environmental problems, and among these, carbon dioxide emissions have been identified as a major cause of global warming. To address these issues, countries around the world are investing heavily in the development and deployment of eco-friendly alternative energy sources, and solar power—a leading form of renewable energy—is expanding rapidly. In fact, global solar power generation in 2025 increased by approximately 600 TWh compared to the previous year, and solar power grew so rapidly that it accounted for about 70% of the annual increase in global electricity production. As of the end of 2025, the cumulative capacity of global solar power generation facilities was estimated to have reached approximately 2,800 GW. Solar power has now moved beyond being merely an alternative energy source of the future to establish itself as a vital power generation source within the global power system. So, how does solar power generation work, and how is it currently used in our daily lives? Furthermore, what improvements are needed to leverage solar power as an even more critical energy source in the future?
Solar power generation refers to the process of converting sunlight into electrical energy using solar cells. A solar cell is fundamentally composed of a structure where an N-type semiconductor and a P-type semiconductor are joined. The N-type semiconductor contains a relatively large number of charge carriers—electrons with a negative (-) charge—while the P-type semiconductor contains a relatively large number of holes, which are the empty spaces left behind when electrons are removed. A hole is not actually a newly created particle with a positive charge; rather, it is a concept where the space left behind by an electron is treated as if it carries a positive (+) charge. When photons—particles of light from the sun—reach the semiconductor of a solar cell, their energy causes electrons to move to a higher energy state, thereby creating electrons and holes. Due to the electrical properties inside the solar cell, electrons and holes move in different directions, and in this process, a potential difference—that is, a voltage—is formed between the electrodes. When the two electrodes are connected to an electrical device to form a circuit, electrons flow through the external circuit, generating an electric current that can be used to power the device.
A typical example of an electronic device that uses solar cells is a calculator. The several small square pieces located in the upper right corner of a calculator are solar cells, and each one is called a “cell,” which is the basic unit of a solar cell. Since calculators require only a small amount of voltage and power, they can operate adequately with just a few solar cells. On the other hand, in facilities like the International Space Station (ISS), where a very large amount of power is required to operate internal electronic equipment and support the astronauts’ daily lives, a much larger number of solar cells must be connected. Therefore, large solar panels are installed to generate the necessary power. As such, to produce more power, it is necessary to either use more solar cells or secure a larger surface area. However, simply increasing the size of the solar panel does not allow for an unlimited increase in power output. As the installation area of the solar panel increases, the costs and management issues associated with land, installation space, structures, and grid connections must also be taken into account. Therefore, in solar power generation, technologies that improve the efficiency of solar cells—along with tracking systems that adjust the orientation of solar panels according to the sun’s position—are utilized to produce more electricity within a limited area. Additionally, concentrated solar power (CSP) systems, which effectively concentrate sunlight using lenses or mirrors to generate electricity—much like how we used convex lenses in science class as children to focus sunlight onto a single point and burn a black plastic bag—are also being employed.
The amount of electricity demanded by society varies depending on the time of day. When electricity demand is high, a corresponding amount of power must be supplied; conversely, during periods of low demand, power generation must be adjusted accordingly. While some conventional power generation methods can respond to fluctuations in electricity demand by adjusting fuel input or the operating status of power generation facilities, solar power generation fundamentally depends on daylight hours and weather conditions for its output. It cannot generate power at night, and output decreases when there are clouds or rain. Due to these characteristics, as the share of solar power increases, it becomes crucial to store the generated electricity so it can be used when needed, or to regulate supply and demand by integrating with other power sources and the power grid. In the past, the capacity and high cost of batteries required for large-scale power storage were cited as major issues, but the situation is changing significantly as battery storage technology advances rapidly. In 2025, approximately 108 GW of new battery storage capacity was added worldwide, representing an increase of about 40% from the previous year. In particular, lithium iron phosphate (LFP) batteries are widely used, accounting for about 90% of new battery storage installations, and the practice of storing electricity during periods of high solar generation and supplying it during peak demand periods is rapidly expanding. Therefore, to efficiently utilize the sun as an abundant energy source, it is important not only to improve the power generation efficiency of solar cells but also to advance battery storage technology, power grids, and demand response technologies in tandem. Solar power is no longer merely a potential energy source for the future but is already rapidly increasing its share of global electricity generation; going forward, the roles of storage and power grids will become even more critical in building a stable and efficient energy system.
