 In this video, we are going to learn the forms and characteristics of renewable energy sources. Learning Outcome After the end of this session, the learner will able to explain various forms of renewable energy sources with their characteristics. Content This video includes the classification of energy sources, significance of renewable energy sources, forms and characteristics of renewable energy sources. First we will see the classification of energy sources. Energy sources are mainly classified into two categories. The first category is renewable energy sources. The examples of renewable energy sources are solar energy, wind energy, geothermal energy, tidal energy, hydro energy and biomass. The second category is non-renewable energy sources. Examples of non-renewable energy sources are petroleum, nuclear, coal and natural gas. Renewable energy sources such as water, solar and geothermal which can be replenished or renewed naturally over the time. Energy produced from food crops and other plants are replenished every growing season. So biofuels are also classified into renewable energy sources. Whereas on other hand, non-renewable energy sources such as fossil fuels, nuclear material are removed or extracted from the earth crust and can be depleted. So these sources have been the most used type of energy in the modern era. Now we will see the forms of renewable energy sources. The most popular renewable energy sources are solar energy, wind energy, hydro energy, tidal energy, geothermal energy and biomass energy. Now we will see the solar energy. Solar energy is most abundant and freely available energy resources on the earth. The output of sun is 2.8 into 10 raise to 23 kilowatt whereas the energy reaching on the surface of earth is 1.5 into 10 raise to 18 kilowatt per year. The efficiency of solar panel is low. Today, the most of solar panels provides an energy efficiency rating from 11% to 15%. That is they convert the solar energy into electrical energy with 11% to 15% efficiency. The main part of solar power plant is solar photovoltaic system that is PV system which changes the sunlight into the electricity. The sunlight is caught by the solar panels and converted into usable electricity by the means of inverter. The electricity produced can then be used to power appliances at our homes directly or that electricity can be stored in a battery for use of latter when the sun is not shining. If we do not use or store the energy, the excess electricity can be directed back to the grids so that that excess electricity can be used at another location. These are the few characteristics of solar energy. The sun energy is available abundantly and is inexhaustible. The solar energy can be produced easily. It can also be used for storage for cloudy and rainy days. The figure shows typical layout of solar energy transmission. The first figure shows installed solar panels. When the solar panels are exposed to sunlight, they produce the electricity. That electricity is then transferred to the converter which converts the DC form into AC form. The converter is shown in figure 2. That AC current then transferred to the meter and then that can be used for household appliances. The excess electricity can also be transferred to the power grid as shown in figure. Now I want you to take a pause and think on how to increase the efficiency of solar panels. Take your time and note down the points. The efficiency of solar panel is very low. Can we change the orientation of panels according to the position of sun to increase the efficiency or the change in material can cause the increase in efficiency? Think on this. The next renewable energy source is wind energy. The wind energy is also byproduct of solar energy. Because of the energy reaching from the sun, the earth heats and cools unevenly which results in the pressure difference at two locations which causes the wind flow. A wind turbine is typically of 30 to 45% efficient which can be increased up to 50% at the peak wind time. According to IRENA's latest data that is International Renewable Energy Resource Agency's latest data, the production of wind electricity in 2016 accounted for the 16% of the total electricity generated by renewables. Wind turbines are classified into two general types. First is horizontal axis, second is vertical axis wind turbines. The first figure shows horizontal axis wind turbine. It is the most commonly used design configuration in wind turbines. When the rotating axis of the blades is parallel to the wind stream, the turbine is called horizontal axis wind turbine. The second diagram shows the vertical axis wind turbines. It is probably the oldest type of wind mills in which the axis of the drive shaft is perpendicular to the ground as shown in the figure. In western countries, they have installed vertical turbines along the roads so that the wind coming from the moving vehicle rotates the blades of the vertical axis wind turbine and they produce the electricity. This diagram shows the typical components of horizontal wheel turbine when the pressure due to air applied on the blades causes to rotate it. The rotary motion of shaft is transferred to the gearbox and generator which produce the electricity. These are the some characteristics of wind energy. The first one is high average wind speed is required that is cut off and cut on both speeds speed averages are high. The cut on speed is the minimum speed of wind required to the rotate of blades of wind mills and cut off speed is the highest speed at which the wind flow causes the cut off of electricity. It is low cost energy but it also requires high initial investment. The third most commonly used renewable energy sources is hydro energy. Hydro power is energy derived from the flowing water. The basic principle of hydro power is using water to drive turbines. The hydro energy power share of 60 to 70 percent of total world electricity generation and 50 to 60 percent of the electricity generated by renewables. Electricity is among the most cost effective means of generating electricity and is often preferred method were available. For example in Norway 99 percent of the electricity comes from hydro power. Hydro power plants consist of two basic configurations with dams and reservoirs or without. The currently installed capacity of hydro power energy in India has around 45700 megawatt. The figure shows the creation of head by constructing a dam where the potential energy of stored water is used to run the turbines with which the help of generator produce the electricity. These are the some characteristics of hydro energy. It requires high investment but it is also low cost energy resources that is the cost of per unit electricity generated is very low. It is easy to control and can be used for storage. These are the references. Thank you.