The word “energy” means the ability to do work. The need for energy in the world increases to a very high dimension because of natural growth and the use of new technology. The source of the combustible fuels we depend on, such as coal, gas, and oil, are finite. The increased burning of fuels raises concerns over global warming and air pollution. Due to the over-dependency of fossil fuels for energy, they are running out, it is necessary to find alternative energy sources, and one alternative source is the sun.
Solar energy is radiant light and heat from the sun that is harnessed using a range of ever-evolving technologies such as solar heating, solar thermal energy, solar architecture, and artificial photosynthesis.
It is also an essential source of renewable energy, and its technologies are broadly characterized as either passive solar or active solar depending on how they capture and distribute solar energy or convert it into solar power.
Learning objectives
By the end of this lesson, you should be able to:
The sun is an extremely powerful energy source, and the sunlight is by far the largest source of energy received by Earth. The solar radiation or sunlight that reaches the ground consists of nearly 50 percent visible light, 45 percent infrared radiation, and smaller amounts of ultraviolet and other forms of electromagnetic radiation. Solar energy is simply the light and the heat that come from the sun. Solar energy is the cleanest and most abundant renewable energy source available.
Forms of solar energy
As illustrated above, the solar panel is responsible for collecting sunlight or solar radiation and convert into electrical energy. The solar charge controller regulates the flow of current from the solar panel to the battery. The controller monitors the voltage of the battery and reduces the current when the battery is fully charged. The battery stores energy for later use. An inverter converts direct current (which solar generates) to alternating current (which is used in the electrical grid). The meter measures the amount of energy used by home appliances like fridges, bulbs, and television.
Solar energy can be in any of the following forms;
Solar radiation can be converted either into thermal energy or electrical energy.
Thermal energy
The most common devices used to capture solar energy and convert it to thermal energy are flat-plate collectors, which are used for solar heating applications. Due to the intensity of solar radiation at Earth’s surface being low, these collectors must be large in area. For instance, a collector must have a surface area of about 40 square meters (430 square feet) to gather enough energy needed for one person.
The most widely used flat-plate collectors consist of a blackened metal plate, covered with one or two sheets of glass, that is heated by the sunlight falling on it. The heat of the sunlight is then transferred to air or water, called carrier fluids, that flow past the back of the plate. This heat can be used directly or may be transferred to another medium of storage. The storage of heat for use at night or on cloudy days is accomplished by using insulated tanks to store the water heated during sunny periods. Flat-plate collectors typically heat carrier fluid to temperatures ranging from 66 to 93 degrees Celsius. The efficiency of such collectors ranges from 20 to 80 percent, depending on the design of the collector.
Another method of thermal energy conversion is found in solar ponds, which are bodies of saltwater designed to collect and store solar energy. The heat extracted from these ponds enables the production of chemicals, food, textiles, swimming pools, and livestock. Solar ponds are fairly expensive to install and maintain and are generally limited to warm rural areas.
Electricity generation
Solar radiation may be converted directly into electricity by solar cells. In such cells, a small electric voltage is generated when light strikes the junction between a metal and a semiconductor (such as silicon) or the junction between two semiconductors. The power generated by a single photovoltaic cell is about two watts. The energy efficiency of most present-day photovoltaic cells is only about 15 to 20 percent, and since the intensity of solar radiation is low, to begin with, large and costly assemblies of such cells are required to produce even moderate amounts of power.
Larger units of photovoltaic cells have been used to provide power for water pumps and communications systems in remote areas and communication satellites.
Classic crystalline silicon panels and emerging technologies using thin-film solar cells, including building-integrated photovoltaics, can be installed by business owners and homeowners on their rooftops to replace the conventional electric supply.
Concentrated solar power plants employ concentrating, or focusing collectors to concentrate sunlight received from a wide area into a small blackened receiver, thereby considerably increasing the light’s intensity in order to produce higher temperatures. The arrays of carefully aligned mirrors or lenses can focus enough sunlight to heat a target temperature of 2,000 degrees Celsius or more. This heat can then be used to operate a boiler, which in turn generates steam for a steam turbine electric generating power plant. For producing steam directly, the movable mirrors can be arranged so as to concentrate large amounts of solar radiation upon blackened pipes through which water is circulated and thereby heated.
Other applications
Solar energy is used to produce salt from seawater by evaporation. Solar-powered desalination units transform saltwater into drinking water by converting the Sun’s energy to heat, directly or indirectly, to drive the desalination process.
Solar technology has also emerged for the clean and renewable production of hydrogen as an alternative energy source.
Factors affecting the performance of solar power system
1. Weather change
As heat exposure can prematurely degrade solar cells' daily production, high temperatures lead to a drop in voltage and a drop in overall power. Solar cells perform better in cold rather than in hot climates. Therefore, a rise in temperatures above 25 degrees Celsius leads to solar panel output decay.
2. Shading
When the shadow falls on even a small part of the solar panel, the current through the entire string is reduced. The shaded cells affect the current flow of the whole solar power system.
3. Roof orientation
The angle of inclination of the solar panels should be actively adjusted according to changes in seasons, latitude and longitude, and sunshine hours.
4. Cleanliness of solar panel
The cleanliness of the solar panel surface is directly connected to photoelectric power conversion. Sandstorms, polluted environments, and rainfall are a few factors that may play a role in reducing the efficiency of solar modules.
Advantages and disadvantages of solar energy
The advantages of solar energy are;
The disadvantages of solar energy include;
Summary
