Solar energy is the most plentiful energy resource on the planet.
The energy absorbed by the Earth from the sun in one hour is about equivalent to the energy needed for one year of human activity.
Solar energy is widely used for power production, as previously stated.
Solar technologies, according to the International Energy Agency (IEA), have the potential to reduce carbon dioxide emissions in the power sector by 14% by 2050, based on the BLUE Map scenario.
Solar energy may be utilized for more than just power production; it can also be used for heating and desalination.
Solar energy's primary benefits are its widespread availability and accessibility, but its intermittency makes prediction difficult.
Solar energy may be harvested using a variety of methods and converted into the energy kinds needed.
Solar Energy Production.
PV panels are used to convert solar irradiation directly into energy.
Special kinds of semiconductors are utilized in PV cells.
The energy for electron transport is provided by sun irradiation on the semiconductor, which results in an electrical current .
Although several novel technologies, like as organic cells, are being explored, the most common kinds of PV technologies are crystalline and thin film.
The IEA estimates that crystalline silicone and thin film technologies account for 85 percent 90 percent and 10 percent 15 percent of the global PV cell market, respectively.
Table 1.1 shows the efficiencies of PV cells depending on their technology.
PV cell efficiencies are poor, as shown in Table 1.1; as a result, the produced power for each surface area is often low or insufficient.
Concentrators may be used in conjunction with PV cells to solve this issue.
Solar radiation is focused using optical instruments in this arrangement, increasing the amount of energy delivered to a particular region.
When using concentrators, it is essential to lower the temperature of the PV cells since their performance degrades at high temperatures.
Heat systems are combined with PV cells for cooling in such methods, as shown, by harvesting the absorbed thermal energy.
The recovered thermal energy is sometimes sold as a byproduct.
Temperature, solar irradiation, dust buildup, shadowing, and soiling of PV panels all influence the performance of PV cells in producing energy.
The amount of energy generated by a PV cell is highly dependent on solar irradiation (solar power per unit of area).
More energy is available for conversion to electricity when solar irradiation rises.
In addition to solar irradiation, the temperature of the PV cell has an effect on the output power since it affects the cell's efficiency.
Higher efficiency is usually achieved by lowering the cell's temperature.
Because of the PV cell's significance in producing energy, many methods for thermal management of PV cells exist, including using water flow, phase change materials (PCMs), and heat pipes.
The presence of grit or dust on the surface of PV cells may prevent sunlight from entering the cell, lowering the energy received and, as a result, lowering the output power.
The dust reduction factor is usually equal to 0.93, which means that the input solar irradiation for a cell is reduced by 7% .
Spraying water on the surface of PV cells is recommended to combat dirt and dust buildup, and it may also help with temperature management.
Another unfavorable factor that reduces PV cell performance is shadowing.
According to certain research, when 5-10% of a solar panel array is shaded, the produced energy may be decreased by up to 80%.
In addition to direct techniques, certain technologies may be used to convert solar energy to electricity in an indirect manner.
Solar energy is utilized to power thermal power plants in these technologies.
Concentrators must be utilized to generate a large amount of thermal energy in a small amount of area.
Concentrated solar power methods are divided into three categories: linear parabolic collector systems, solar towers, and parabolic dish collectors.
A linear concentrator with a parabolic cross-sectional form makes up a linear parabolic collector.
On a single axis, the concentrator's surface follows the path of the sun.
This concentrator is mounted on a support structure, which keeps it stable and allows it to operate well in adverse circumstances like as wind.
The received sunlight is concentrated on a tube along the focal point in these concentrators.
There is a working fluid within the tube that gets heat from focused sun irradiation.
The reflecting panels of parabolic dishes rotate along two orthogonal axes to follow the sun's path.
The panels direct the sun's rays toward a receiver at the focal point.
High-temperature thermal energy is transmitted to the working fluid by using these concentrators.
Heliostats, or flat-surfaced reflecting panels, are used in solar tower systems to concentrate the sunlight.
These panels spin on two axes, focusing solar energy on the receiver at the top of the tower, which is situated in the system's center.
The concentrated solar energy is absorbed by the fluid within the solar receiver, which raises its temperature and pressure.
To increase efficiency, solar thermal energy systems may be combined with existing thermal power plants.
In certain gas turbine cycles, solar energy is used to pre-heat the compressed air that enters the combustion chamber, as illustrated below.
In certain setups, the presence of a thermal energy storage unit may enhance the system's efficiency and allow it to operate at night.
Solar energy may be utilized alone to generate electricity, in addition to hybrid systems that employ both fossil fuels and solar thermal energy.
Solar energy is used in these systems to raise the temperature and pressure of air (or another working fluid) to levels suitable for use in a power generating turbine.
To extract more energy per unit of area, solar concentrators are used.
Heat recovery may increase the efficiency of these cycles.
A schematic illustration of a Brayton cycle with heat recovery and intercooling units may be seen here.
Other concepts, such as utilizing supercritical fluids and merging Brayton cycles with other cycles, such as Rankine cycles, have been used to improve the efficiency of these cycles in addition to heat recovery units.
The primary thermal input to run the Rankine cycle in these setups comes from the gas turbine's output hot gases.
These designs often have greater efficiency than basic Brayton cycles.
Thermostats and air conditioners.
Around 2010, the proportion of energy consumption in the construction industry in global final energy utilization, which refers to final energy consumption by end users, was 35.3 percent.
Renewable energy systems, particularly solar technology, may be utilized to supply energy for heating and cooling in a variety of industries.
In order to gather, store, and distribute thermal energy to buildings, renewable-based heating technologies are utilized, while cooling systems are used to provide cooling capacity.
Solar energy may be utilized to heat a building in a variety of ways, including a Trombe wall, an unglazed transpired solar façade, and a solar chimney.
Trombe walls are made up of a huge wall, an air duct, and an exterior layer of glass.
A Trombe wall is shown schematically here.
The big wall is utilized to collect and store the energy of the sun that flows through the glass in these kinds of systems.
A part of the absorbed heat is transmitted to the interior space through conductive and convective heat transfer processes.
Furthermore, cold air enters the channels via a lower vent, is heated, and rises owing to the buoyancy effect before exiting the channel through an upper vent.
An unglazed transpired solar façade is made out of metal sheet walls having holes in them, which are used to capture solar thermal energy and heat the building.
A fan is employed to circulate the air flow, as illustrated below.
A solar chimney works by turning thermal energy into kinetic energy, which is then used to circulate air.
Other technologies for air heating in buildings, such as solar roofs, are available in addition to these techniques.
The use of solar thermal energy in buildings is not restricted to air heating; it may also be utilized to heat water.
In most instances, water is collected using collectors that face the sun.
Many designs for solar water heating systems have been suggested, with direct and indirect water heating methods being the most common.
Water passes through a collector and absorbs thermal energy in direct water heating systems, while heat exchangers are used to transmit the thermal energy of the applied collectors in indirect water heating systems.
Solar energy may be used for cooling.
In thermally driven cooling processes, solar cooling systems use the absorbed heat from sunshine.
In these systems, there are two primary processes.
Thermally powered sorption chillers are utilized in closed cycles to produce chilled water for use in space conditioning facilities.
Water is often used as a refrigerant in open cycle solar cooling systems, and a desiccant is used as a sorbent for air purification in ventilation technologies.
One of the most significant benefits of solar cooling systems over alternatives is their naturalness.
Because the greatest needed cooling demand corresponds with the strongest sun irradiation, using these kinds of systems may reduce peak electrical demands on the electrical network as compared to traditional cooling systems.
In addition, during cold seasons, solar cooling methods may be used for heating, including water heating.
Desalination.
The development and use of desalination systems is necessitated by the rising trend in global population and the resulting rise in the demand for consumable freshwater.
Desalination is a procedure that eliminates salt from salty feed-water, resulting in usable water for drinking and agricultural.
Thermal and membrane technologies are the most common kinds of desalination systems.
Around 73 percent of the world's desalination units were based on membrane technology as of the end of 2016, with the other ones being thermal.
Both directly and indirectly, renewable energy technologies may be used for desalination.
In general, direct techniques utilize the thermal energy of renewable energy sources for water evaporation and salt removal, while indirect techniques use renewable energy sources to produce the necessary power for membrane technology.
For desalination plants, solar energy is one of the most appealing renewable energy sources.
The sun provides the heat needed for saline water evaporation in thermal desalination systems.
Solar thermal desalination systems that use thermal energy storage units like PCMs can operate at night.
Despite the fact that using thermal storage to enhance the efficiency of solar thermal desalination units has increased their prices, they are still economically viable for large-scale systems.
Solar energy may be used for indirect water desalination in addition to thermal desalination devices.
Membrane-based desalination machines utilize energy produced by PV panels or solar thermal power plants in these kinds of desalination systems.
~ Jai Krishna Ponnappan
