Solar energy is the radiant energy released by the fusion process (the conversion of hydrogen gas into helium) in the core of the sun. The sun is a clean and inexhaustible renewable energy source that emits approximately 3.9x10 ²⁶ W of power. A very small amount of this energy emitted from the sun reaches the Earth. An average of 1,367 W of power falls on each square meter of the outer surface of the atmosphere. Some of this radiation, which usually consists of X-rays and ultraviolet rays, is absorbed by the atmosphere, while some are reflected.

The studies carried out by our Ministry in order to evaluate this huge and renewable energy source have gained speed recently. Countries have accelerated the transition to renewable energy in order to avoid the damages caused by fossil resources to the environment. In this way, many studies are being conducted on the production of heat and electricity from solar energy and its usage is increasing over the years. Although there is more than one method for the production of electricity from solar energy, the general tendency is to focus on photovoltaic systems where the light coming from the sun is directly converted into electricity. Studies on the utilization of solar energy have gained speed especially after the 1970s, solar energy systems have shown technological progress and decreased in terms of cost, and have established themselves as an environmentally clean energy source. In particular, being a clean energy source and operating at low cost after installation increases the importance of solar energy.

It is not possible to provide the energy required for industry, residences or individual purposes directly from the sun. For this reason, solar energy can be converted and used in various ways. Many technologies have been developed to benefit from solar rays. While solar energy technologies vary greatly in terms of method, material and technological level, some use solar energy directly in the form of light or heat energy, while other technologies are used to obtain electricity from solar energy. Areas of use of solar energy include direct or indirect electricity generation, hot water generation, space heating and cooling, process heat energy for industrial establishments and greenhouse heating.

Solar technologies are basically divided into two main groups.

1. THERMAL SOLAR ENERGY TECHNOLOGIES

are divided into two groups according to the temperature values obtained: low temperature applications and concentrator thermal systems.

1.1. Low Temperature Applications

Planar and vacuum solar collectors, solar pools, solar chimneys, water purification systems, solar architecture, product drying and greenhouse heating systems and applications such as solar cooking are applications aimed at obtaining low temperatures from solar energy. Among these application types, planar solar collectors are the simplest and most common method of utilizing solar energy. Planar solar collectors work on the principle of transmitting the solar energy coming to their surface to water, air or any fluid. These systems are mostly used for water heating in homes. The temperature they reach is around 70°C. Planar solar collectors generally consist of a transparent cover (flat glass or vacuum pipe), an absorber surface that collects solar radiation, carrier pipes integrated into the surface, insulation material and a case. Planar solar collectors are placed at a fixed angle to receive maximum sunlight depending on the latitude of the region. Planar solar collector systems are divided into two as natural circulation and forced circulation (circulation pump). These systems are used to provide hot water for homes as well as swimming pools and industrial facilities. 

1.2. Condenser Thermal Systems

Concentrator solar thermal energy technologies are used especially for the purpose of generating electrical energy. The installed capacities of production facilities based on these technologies are 10 MW and above. In concentrator solar thermal energy technologies, parabolic mirrors, dishes or heliostats are used as solar concentrators and electrical energy generation is carried out by the methods listed below;

1. Collecting solar radiation using a collector system
2. Concentrating solar radiation onto a receiver
3. Conversion of solar radiation into thermal energy with the help of a receiver
4. Transfer of thermal energy to a power conversion system
5. Conversion of thermal energy into electrical energy by a steam turbine-generator system.

concentrator thermal systems are basically applied in three parts: parabolic trough collectors, parabolic dish systems and central receiver systems.

2. PHOTOVOLTAIC SOLAR TECHNOLOGIES

Solar modules, the most basic components of photovoltaic solar technologies, convert solar energy directly into electrical energy.

In 1839, the French scientist Edmond The photovoltaic effect, which was discovered by Becquerel , was discovered by the light emitting electrode in a conducting liquid. In fact, the photovoltaic effect was observed in solidified selenium by WG Adams and RE Day in 1877. This development was followed by the selenium solar cell, which was developed by C. Fritts in 1883 and placed on a thin layer of gold with an efficiency of 1% gold. Following these developments, W. Hallwachs designed a semiconductor junction solar cell using copper and copper oxide. This effect began to be better understood with the photoelectric effect article, which was discussed from a quantum perspective by A. Einstein in 1904. The production of electricity from the sun, which began with the first Si pn junction solar cell produced by Bell Laboratories in 1954, has reached the present day and has been the subject of great developments and many studies.

The basic principle in photovoltaic solar technologies is photovoltaic conversion. This conversion occurs in two stages. In the first stage, the formation of charge pairs, which are positive-negative current carriers, and in the second stage, the separation of the pairs from each other by an electric field. While creating the PN junction, the n-type semiconductor material with excess electrons and the p-type semiconductor material with excess positive charge are brought together. There is a structurally created electrical field in this junction. All energy conversion events occur in this region. The solar photons coming to this junction give their energy to the electrons in this junction and the negative-positive charges formed with this energy are separated from each other by the existing electrical field. Thus, direct current is produced in the circuit. This produced direct current can be stored in a battery group when desired or can be given to the grid via DC/AC inverters .

photovoltaic solar technologies is silicon. Among the many semiconductor materials, the most suitable for producing solar cells are silicon, cadmium sulfide, gallium arsenide , and cadmium telluride. 

Solar cells are divided into two groups: crystalline and amorphous. The most common silicon solar cells are produced in different technologies such as single (mono) crystalline, poly ( poly ) crystalline, thin film and ribbon. The solar cell, whose surfaces are shaped as square, rectangular or circular, usually has an area of around 100 cm² and a thickness of 0.2–0.4 mm.

Solar modules are created by bringing solar cells together. Today, the surface area of solar modules used for electrical energy production has reached 2.1 m2 ^and their power has reached 675 Wp . By bringing solar modules together, high-power solar panels and solar power plants (SPP) can be installed. Depending on today's technologies and the type of installation (fixed system, sun-tracking systems), a SPP with a capacity of 1 MWe can be installed on an area of 13-25 acres. In particular, with SPPs installed on the roofs and facades of buildings, the required electrical energy can be produced at consumption points.

GEPA - Our Solar Energy Potential

 Our country has a significant solar energy potential due to its geographical location. According to the Turkey Solar Energy Potential Atlas (GEPA) prepared by our Ministry, the average annual total sunshine duration is 2,741 hours and the average annual total radiation value is calculated as 1,527.46 kWh / m2. The general potential view and monthly average global radiation distribution in GEPA are given below.

Date of Update: 26 December 2024