Solar energy is the only source of energy that humans have consciously and unconsciously utilized for living since the beginning of life on Earth. Various methods for harnessing solar radiant energy have existed since ancient times. Human efforts have always aimed to optimize the use of solar energy to meet daily needs.
Today, the application of this inexhaustible source of energy is not limited to using its radiant energy for lighting and heating needs. A significant milestone in solar energy use globally is the development of photovoltaic cells and the production of electricity using sunlight.
This article provides a comprehensive definition and examination of various aspects of solar energy use. If you want to know the complete history of solar energy up to the present day, stay with us.
What is Solar Energy?
Sunlight is like an endless spring of energy found abundantly on the surface of our planet. Every ray of sunlight that reaches Earth is composed of a vast number of energy packets. These packets are photons, which ultimately provide the energy for Earth.
Photons are the result of nuclear processes and reactions in the atoms at the center of the Sun. These reactions occur continuously due to the extremely high temperature and pressure in the Sun's core. In this process, hydrogen atoms are converted into helium atoms, releasing tremendous thermal energy. This thermal energy moves from the Sun's core to its surface and is ultimately emitted as radiant light and heat into the surrounding space.
The enormous amount of energy that reaches Earth's surface daily makes the Sun a renewable and clean energy source. Utilizing this renewable source not only reduces environmental pollution but also ensures energy security due to its inexhaustible nature.
In general, various technologies for harnessing energy from sunlight have been designed and developed to meet the heating and electricity needs of communities, achieving high efficiency over time.
History of Solar Energy Utilization
Humans have long sought to harness solar energy. The history of solar energy and its conscious use by humans dates back to 7000 years ago in China and 3000 years ago in ancient Egypt. During these times, people attempted to capture and store solar energy for heating and lighting by designing buildings and using appropriate construction materials. In ancient Greece and Rome, the use of solar energy in urban planning and building design was also noted.
With the onset of the Industrial Revolution and the emergence of fossil fuels like coal and oil, the use of solar energy declined. This shift was due to the easier access and lower costs of these resources, leading to increased reliance on fossil fuels. However, in the early 20th century, concerns about environmental pollution and the limitations of fossil fuel resources renewed interest in renewable energy.
In the 1950s, advancements in semiconductor technology improved the efficiency of solar cells, and this technology began to be used in satellites. By the early 1970s, rising oil prices and the energy crisis refocused global attention on renewable energy, including solar power.
In the 1980s, technological advancements related to solar energy and gradually decreasing costs expanded its use into various sectors. In the 21st century, with growing environmental concerns and climate change, solar energy has increasingly been recognized as a clean and renewable energy source.
Given the benefits of this renewable and clean energy source, its use is expanding in various industries such as construction, transportation, and manufacturing. It is anticipated that in the near future, solar energy will play a significant role in the global energy mix and become one of the primary sources of energy worldwide.
The utilization of solar energy has been conducted in various ways since the formation of human civilizations. The approaches to exploiting this energy can be categorized into two groups: active and passive techniques.
Active and passive solar energy utilization techniques are complementary and effective approaches that together allow for maximum exploitation of the abundant energy from the sun. The application of these techniques in buildings, industries, and other sectors plays a vital role in energy sustainability and reducing environmental impacts.
Active Solar Energy Utilization Techniques
Active solar energy techniques refer to methods that involve the use of mechanical and electrical equipment to collect, store, and convert solar energy. These techniques directly harness solar energy to generate electricity or thermal energy. The most important active techniques include:
Photovoltaic Solar Systems
Photovoltaic (PV) systems are among the most important and practical technologies for harnessing solar energy today. These systems utilize semiconductor materials with the photovoltaic effect to directly convert sunlight into electrical energy. The phenomenon where sunlight is directly converted into electrical current is known as the photovoltaic effect
Photovoltaic cells, which form the core of solar power generation systems, are typically made of silicon. These cells absorb photons from sunlight in specific layers, causing the separation of electric charges (electrons and holes), thereby creating an electrical potential.
When multiple photovoltaic cells are placed together and connected properly, they form solar panels. These panels, which are the primary units of PV systems, generate electrical energy in the form of direct current (DC).
To use the solar electricity generated by PV systems in alternating current (AC) consumer systems, electronic converters (inverters) are required. These inverters convert DC into AC with the specifications needed by the consumer.
Photovoltaic systems can independently and autonomously supply electricity to homes, buildings, and even national power grids. These systems are adaptable for use in residential solar setups, portable devices, or large-scale solar power plants.
Advantages of photovoltaic systems include their environmental friendliness, no need for fossil fuels, the ability to be used in remote and sparsely populated areas, and their flexibility in large-scale installations. However, initial investment costs and the relatively lower efficiency of photovoltaic systems compared to other energy sources are major challenges. Yet, with ongoing technological advancements and increased mass production, the costs are steadily decreasing, and the efficiency of these systems continues to improve.
Given the numerous benefits of photovoltaic systems and the rapid development of this technology worldwide, it is expected that these systems will play a significant role in future electricity generation, becoming a key part of many countries' energy portfolios.
Solar Thermal Systems
Another method of harnessing electricity from solar energy is through solar thermal power plants. Unlike photovoltaic systems, in this method, solar radiation is not directly converted into electrical energy. These power plants use the heat collected and stored from the sun to produce steam, which is then used to generate electricity.
In solar thermal power plants, specialized equipment called solar collectors are responsible for absorbing and storing heat from solar energy. These collectors use reflection and concentration of solar rays onto an absorber surface to capture the heat, which is then transferred to a fluid (usually water or oil).
Simply put, solar radiation is first concentrated at a point (the collectors) using mirrors or special lenses. The heated fluid in the solar collectors is then transferred to a heat storage tank via a heat exchanger. These storage tanks can retain the heat for extended periods and release it to the steam turbine system for electricity generation when needed.
The steam turbine system operates similarly to conventional thermal power plants. The hot steam produced in the heat exchanger enters the steam turbines, which spin to drive an electric generator, producing electricity.
Solar thermal power plants can operate in either direct or indirect modes. In the direct method, the heat is transferred to the steam turbines without storage. In the indirect method, the heat is stored in tanks first and then transferred to turbines as needed. Today, various technologies exist for solar thermal power plants, each with its own unique features. These include parabolic mirrors, solar towers, and linear mirrors.
Despite the high initial investment costs, solar thermal power plants offer several advantages, such as zero emissions, increased safety, and longer lifespan compared to other electricity generation methods. Additionally, with the ability to store heat, these plants can continue producing electricity even when the sun is not shining.
photovoltaic (PV) and solar thermal systems combination
Combination of photovoltaic (PV) and solar thermal systems plants are advanced systems that combine various technologies, including photovoltaic (PV) and solar thermal systems, to generate electricity. These plants achieve a higher overall efficiency compared to using either technology alone.
In these plants, sunlight is first concentrated by large parabolic mirrors and directed onto a heat-absorbing tube. This absorber tube, typically made of steel and coated with special materials, transfers the heat to a fluid, such as water or oil.
The heated fluid then enters a heat exchanger, where it produces steam. The steam drives a steam turbine, which, in turn, powers an electricity generator. This thermal section of hybrid plants operates similarly to traditional solar thermal power plants.
Simultaneously, another part of the solar energy—comprising radiant photons—is captured by photovoltaic panels, converting the sunlight directly into electricity.
The primary advantage of hybrid solar plants is their higher overall efficiency compared to standalone photovoltaic or solar thermal systems. This is because both the PV and thermal sections are utilized to harness the sun's energy simultaneously.
Other benefits of hybrid solar systems include the ability to store thermal energy for use during periods without sunlight, flexibility in design, and scalability. However, the initial installation and setup costs for hybrid systems are relatively higher than those of standalone photovoltaic or thermal systems. Additionally, their design and management tend to be more complex.
Solar Water Heaters
Solar water heaters are one of the most important applications of solar energy in daily life. These systems directly use the sun's energy to heat water, making them a clean and renewable alternative to conventional water heaters powered by fossil fuels.
The basic working principle of solar water heaters involves capturing and storing heat from sunlight. These systems use collectors exposed to direct sunlight to absorb solar energy in the form of heat. This heat is then transferred by a heating fluid (usually water) to a storage tank.
When hot water is needed, the stored heat in the tank is transferred to the hot water pipes, making solar-heated water available for use. The energy absorbed by the collectors is thus converted into hot water for the consumer.
In addition to the benefit of using clean and renewable solar energy, solar water heaters have other advantages. They require less maintenance and repairs compared to conventional water heaters and significantly reduce fuel and electricity costs.
Given the benefits of solar water heaters and the growing concerns about climate change and the depletion of fossil fuel resources, the use of this technology as a solution for providing hot water in residential, commercial, and industrial sectors is on the rise globally. It is expected that solar water heaters will soon become a common and cost-effective option for hot water supply.
Passive Solar Energy Utilization Techniques
Passive solar energy techniques refer to methods that harness solar energy without the need for mechanical or electrical equipment. These techniques rely on the design of buildings and the use of appropriate materials to absorb and store solar energy, which is then used for heating, cooling, and lighting purposes. The most important passive solar techniques include:
Passive solar building design
Passive solar building design is a method that effectively incorporates solar energy into the construction and design of buildings. This approach aims to optimize the use of solar energy for heating, cooling, and lighting within structures. By considering factors such as building orientation, window placement, and the use of thermal mass, buildings can be designed to naturally regulate temperature and reduce the need for artificial heating and cooling.
In passive solar building design, the building's location and orientation, the type of construction materials, the size and shape of windows, and shading elements are chosen in a way that optimizes the use of solar energy within the building. For example, placing windows facing south and using materials with thermal storage capabilities, such as brick or concrete, allow the building to absorb sunlight in winter, providing warmth. Additionally, using movable shades or curtains in summer prevents excess heat from entering the building.
Passive solar building design not only reduces energy consumption and heating/cooling costs but also decreases environmental pollution and enhances residents' comfort. Given the benefits in energy efficiency and environmental protection, solar building design has become a key topic in sustainable architecture and construction.
Use of Building Materials with Optimal Thermal Performance
Using building materials with optimal thermal performance is one of the most effective ways to enhance energy efficiency in buildings. These materials, with their specific properties, improve insulation, heat storage, and proper heat transfer within the building.
One of the key features of these materials is their low thermal conductivity. Low thermal conductivity means reduced heat transfer through the material, effectively resisting heat flow and minimizing the loss of heating and cooling energy in the building. Additionally, some of these materials, like brick, concrete, and stone, have high thermal capacity. This allows them to store heat. As a result, they can absorb solar energy during the day and release it into the building's interior at night. The use of materials with optimal thermal performance in building construction not only increases energy efficiency and reduces heating and cooling costs but also reduces greenhouse gas emissions and enhances the environmental sustainability of the building. Therefore, using these materials is a highly effective strategy for sustainable construction.
Applications of Solar Energy
Today, the applications of solar energy cover a wide range of residential, commercial, industrial, and agricultural uses. In the residential sector, solar systems are used for both electricity generation (solar homes) and providing necessary heating (solar heating systems). Solar panels installed on rooftops can meet a significant portion of household electricity needs. Additionally, solar water heaters for producing hot water are a common residential application of solar energy.
In the commercial and industrial sectors, solar energy plays a crucial role. Large-scale solar power plants are established to supply electricity to commercial, office, and industrial centers. Solar systems are also used for heating, cooling, and lighting commercial buildings. In industries, solar energy is applied in industrial processes such as steam generation and process heating. In the agricultural sector, solar energy has various applications. Solar-powered water pumps are used for irrigation and providing drinking water for livestock. Solar energy is also used for drying agricultural products and in cooling systems for maintaining products in storage. Additionally, in greenhouses, solar energy provides heating, lighting, and ventilation. Due to its unique features, solar energy is penetrating various economic sectors and is expected to see even greater expansion in its applications in the near future.
Modern Technologies in the Solar Energy Field
In recent decades, modern technologies in the solar energy sector have made significant progress. These advancements include increased solar panel efficiency, reduced production and installation costs, and the development of energy storage systems. Additionally, new technologies such as concentrated solar power (CSP) and advanced solar cells now offer greater energy production capabilities compared to the past. In this article, we will examine these innovations and their impact on the solar energy industry.
High-Efficiency Solar Panels
Throughout its development, the renewable energy industry has witnessed various technologies for manufacturing solar panels. Among these, high-efficiency solar panels represent a significant advancement in recent years. These panels have achieved a notable increase in the efficiency of converting solar energy into electricity. Advanced new solar cells, such as multi-junction cells and Concentrator Photovoltaics (CPV), have managed to achieve conversion efficiencies of over 37% in some cases. In contrast, silicon cells theoretically have the potential to produce electricity with efficiencies around 29%. However, this theoretical potential has not yet been fully realized in practice, with most commercially available cells achieving efficiencies between 22% and 24%.
In the previous section, we discussed advancements in solar cell technology. In addition to improvements in cells, significant progress has also been made in the design and manufacturing of solar panels. A solar panel consists of a certain number of solar cells that are connected to the junction in order to generate more electricity. Modern panels use advanced materials, optimized structures, and increased light absorption surfaces, which have all contributed to improving their efficiency. Some of the latest solar panels have demonstrated efficiency rates of over 22%, which is notably higher than previous generations. Overall, these remarkable advancements in high-efficiency solar cells and panels have played a crucial role in the widespread adoption of solar energy globally.
Energy Storage Systems
In recent years, significant advancements have been made in energy storage systems for solar power plants. These developments play a crucial role in enhancing the efficiency and reliability of solar energy electricity generation. One of the most important achievements in this field is the development of advanced lithium-ion batteries. These batteries can store large amounts of energy in a compact size and weight. Their charge and discharge cycles, as well as their efficiency, have also greatly improved, making lithium-ion batteries a primary choice for energy storage in solar power plants. In addition, hydrogen-based energy storage technology has also seen notable advancements. In these systems, solar energy is used to produce hydrogen through water electrolysis. The stored hydrogen can later be converted back into electricity via fuel cells when needed. This technology is especially suitable for large-scale energy storage.
Furthermore, innovations in newer storage technologies, such as Redox flow batteries, sodium-ion sandwich batteries, and compressed air energy storage, have been developed, each with its unique features. Overall, these advancements in energy storage systems have not only improved the efficiency of solar power plants but have also facilitated the broader use of this renewable energy source.
Solar Tracking System
The Solar Tracking System is one of the advanced technologies in the solar energy field that has seen significant development in recent years. These systems automatically adjust the position of solar panels to optimize their orientation relative to the sun, thereby increasing electricity production efficiency. There are different types of solar tracking systems, including single-axis and dual-axis trackers. Single-axis trackers adjust the panels' position along one axis (usually horizontally, from east to west as the sun rises and sets), while dual-axis trackers move the solar panels both horizontally and vertically (up and down) to maximize sunlight exposure throughout the day.
Modern advancements in solar tracking technology include the use of advanced sensors, intelligent algorithms to control panel movement, and renewable energy sources to power the tracking system. For example, the use of solar sensors and wireless sensor networks enables real-time, precise tracking of the sun's position. Additionally, utilizing renewable energy sources such as wind and solar power to operate the tracking system increases its efficiency and autonomy.
Studies have shown that solar tracking systems can increase electricity production by more than 35% on sunny days compared to fixed-panel systems. This is particularly cost-effective in regions with abundant sunlight, such as tropical and desert areas. However, the high installation and maintenance costs of these systems remain a significant challenge to their widespread adoption.
Advantages of Solar Energy
Solar energy, as one of the most important and cleanest renewable energy sources, offers numerous benefits, making it an attractive option for meeting the energy needs of communities. One of the most significant advantages of solar energy is its environmental friendliness. Unlike fossil fuels, which release greenhouse gases and pollutants during combustion, solar energy produces no environmental pollution. This plays a crucial role in reducing greenhouse gas emissions and combating climate change. Additionally, the source (sunlight) is unlimited and accessible to all, with minimal costs for extraction and use.
Furthermore, utilizing solar energy as a local energy source allows communities to achieve energy self-sufficiency. This can help reduce dependency on fossil fuel imports and increase energy security. In rural and remote areas without access to the national power grid, solar systems provide a highly effective solution. Overall, these features highlight the substantial advantages of solar energy, attracting the attention of communities worldwide.
Challenges and Obstacles in Solar Energy Development
Despite the numerous benefits of solar energy, there are still several challenges and obstacles hindering the widespread development of this renewable energy source. One of the most significant challenges is the high initial investment cost required for installing solar systems. Although the operational and maintenance costs of these systems are low, the upfront costs for purchasing solar panels, equipment, installation, and commissioning remain relatively high. This issue is especially a barrier for low- to middle-income individuals and households.
Additionally, the intermittency and variability of solar energy production, due to its dependence on sunlight, pose another challenge. On cloudy days or during the night, solar energy production decreases or halts altogether, increasing the need for energy storage systems.
Moreover, spatial limitations for installing solar power plants in residential and urban areas are another obstacle. In some regions, land ownership constraints also exist, preventing the establishment of large-scale solar power plants, which requires further planning and coordination.
Furthermore, the lack of public awareness about the benefits of renewable energy and insufficient government and policymaker support are among the key challenges facing solar energy development.
However, with ongoing technological advancements, increased production scales, and the implementation of supportive policies, there is hope that these challenges can be overcome in the near future, leading to more widespread use of solar energy.