Assignment Code: MRW-003/TMA/2023

Course Code: MRW-003

Assignment Name: Renewable Energy Systems

Year: 2023

Verification Status: Verified by Professor

Note:

1. For any question worth 5 marks the word limit is 200 words, for a 10-mark question it is 350 words.

2. All questions are compulsory. All questions carry equal marks.

Q.1 What are fossil fuels? Describe the process of formation of fossil fuels and their effect on the environment. 10

Ans) A fossil fuel is a hydrocarbon-containing substance that was naturally generated in the crust of the Earth from the remnants of deceased plants and animals. This material is then recovered from the crust of the Earth and burnt as a fuel. Coal, oil, and natural gas are the three primary types of fossil fuels. Burning fossil fuels can supply heat for direct consumption (such as in cooking or heating), provide power to motors (such as the internal combustion engines used in automobiles), or create electricity. Before being used as fuel, certain fossil fuels are processed further to produce derivatives such as kerosene, gasoline, and propane.

The anaerobic breakdown of deceased creatures that have been buried for a long time and contain organic molecules that were produced by photosynthesis is where fossil fuels come from. In order to transform these elements into fossil fuels with a high carbon content, a geological process that can take millions of years is often required. Fossil fuels are a sort of non-renewable energy source that are generated over a period of millions of years from the skeletal remains of species that have since died. Coal, oil, and natural gas were all formed from the remains of plants, animals, and microbes that existed in prehistoric periods and went through a natural process of transformation that culminated in their development. These remains include fossils.

The accumulation of dead organic materials in layers across the surface of the Earth, such as on peat bogs, swamps, and ocean bottoms, is the first step in the process that eventually leads to the production of fossil fuels. After a period of time, the organic matter will be pushed further and deeper into sedimentary layers of sand, clay, and rock, where it will be subjected to extreme heat and pressure. The transformation of biological materials into fossil fuels like coal, oil, and natural gas is brought about via a process known as diagenesis and burial. The dead remnants of plants that grew on land and were buried in swamps and marshes eventually turn into coal. The decomposition of very small marine creatures, such as plankton and algae, that occurred when they were deposited on the ocean floor results in the formation of oil and natural gas.

The use of fossil fuels has had a considerable influence on human civilization since they are the primary source of energy that is used for a variety of purposes, including transportation, industry, and the creation of electricity. However, the mining and combustion of fossil fuels have led to serious problems for the environment, including contamination of the air and water as well as emissions of gases that contribute to global warming. When fossil fuels are burned, enormous quantities of carbon dioxide are produced. Carbon dioxide is a greenhouse gas that contributes to both climate change and global warming. In addition, the extraction and transportation of fossil fuels can result in oil spills and other environmental catastrophes, which are detrimental to the health of ecosystems and the animals inside them. In addition, the mining of coal can cause damage to the surrounding community, as well as deterioration of the soil and contamination of the water.

Q.2 Describe the various types of solar radiation received by the earth. 10

Ans) Solar radiation may be defined as the form of energy, in the form of electromagnetic waves, that is emitted by the sun. When this energy reaches the atmosphere of the Earth, various components of the atmosphere and the surface of the Earth absorb it, reflect it, and disperse it. Visible radiation, ultraviolet radiation, and infrared radiation are the three primary forms of solar radiation that are received by the Earth.

Visible Radiations

The part of the sun's energy that can be seen with the naked eye is referred to as visible radiation. It encompasses hues ranging from violet to red and has a wavelength range of around 400 to 700 nanometers (nm). This radiation is what causes the sun's brilliance, and it is the most important source of light for the process of photosynthesis, which occurs in plants. The portion of the electromagnetic spectrum that can be seen by a human with their own eyes is referred to as the visible spectrum. The electromagnetic radiation with wavelengths falling within this range is referred to as visible light or just light.

The average human eye is sensitive to wavelengths ranging from around 380 to approximately 750 nanometers. This corresponds to a frequency range that is somewhere in the neighbourhood of 400–790 terahertz, depending on how precise you want to be. These limits are not precisely delineated, and they may be different for different people. These limitations of human perception can extend to 310 nm (ultraviolet) and 1100 nm under ideal circumstances. (near infrared). Some people believe that the visible spectrum and the optical spectrum are the same thing. However, some writers define the term optical spectrum in a broader sense, such that it also includes the ultraviolet and infrared regions of the electromagnetic spectrum.

Ultraviolet Radiation

When compared to visible radiation, the wavelength of ultraviolet (UV) light, which ranges from 100 to 400 nanometers (nm), is significantly shorter. This type of radiation may be further classified into three subgroups: UVA, UVB, and UVC. UVA rays have the longest wavelength and are considered to be the least dangerous to human health. UVB rays have a shorter wavelength than UVA rays, and they are responsible for sunburn and other skin damage. The wavelength of UVC is the shortest, and it is almost fully absorbed by the atmosphere around the Earth.

Infrared Radiation

Visible radiation has a wavelength that ranges from 700 nanometers to 1 millimetre, whereas infrared radiation has a wavelength that ranges from 1 millimetre to 1 metre (mm). Although it is not apparent to the naked eye, heat sensors are able to detect its presence. Infrared radiation is the principal factor that contributes to the greenhouse effect and is responsible for the warming of both the surface of the Earth and the atmosphere above it.

Q.3 Enlist the advantages and disadvantages of renewable energy. 10

Ans) The term "renewable energy" refers to power that comes from natural resources that may be regenerated over time. Some examples of such resources are sunshine, wind, water, and heat from geothermal sources. The following are some of the benefits and drawbacks of using renewable energy sources:

Advantages

1. Sustainability: Renewable energy sources are sustainable and can be replenished naturally, unlike fossil fuels, which are finite and will eventually run out.

2. Low or Zero Emissions: Because renewable energy sources do not release greenhouse gases or other hazardous pollutants, the usage of these sources can help alleviate the effects of climate change while also reducing pollution in the air and water.

3. Cost-effective: Renewable energy sources are becoming increasingly cost-competitive with fossil fuels and can reduce energy costs over time.

4. Job Creation: It is possible for the renewable energy industry to provide new jobs in the areas of manufacture, installation, and maintenance, which would be to the advantage of the surrounding communities.

5. Energy Independence: Using renewable energy sources can reduce a country's dependence on imported fossil fuels and increase energy security.

Disadvantages

1. Intermittency: It is important to keep in mind that renewable energy sources, such as wind and solar, are reliant on the prevailing weather conditions and the time of day. Because of this, it might be difficult to balance supply with demand, which necessitates the development of technologies for energy storage.

2. Land Use: Some renewable energy sources, like hydropower and bioenergy, need enormous land expanses in order to function properly, which can have negative effects on both the environment and society.

3. Upfront Costs: Renewable energy technologies often have higher upfront costs compared to traditional fossil fuel-based technologies.

4. Transmission Constraints: Some sources of renewable energy are situated in inaccessible regions, and as a result, the necessary transmission infrastructure may not be in place to bring the energy to the places where it is required.

5. Environmental Impacts: Although renewable energy sources do not contribute to the production of greenhouse gases, they may have significant environmental effects, such as the alteration of land use, the destruction of habitat, and the killing of birds and bats by wind turbines.

Q.4 Describe three basic types of solar cell and discuss about their efficiency. 10

Ans) The three basic types of solar cell and discuss about their efficiency are:

Monocrystalline Solar Cells:

Solar cells constructed from monocrystalline silicon are made from a single crystal of pure silicon. They have a high efficiency rate of 15-20 percent, which indicates that they are able to convert 15-20 percent of the energy that the sun provides into electricity. These cells are a consistent black tone, and their morphology is spherical and homogeneous. Because of their greater efficiency rates and the manufacturing procedure that goes into making them, they are often the costliest form of solar cell.

Polycrystalline Solar Cells:

Solar cells manufactured from polycrystalline silicon are composed of several crystals of silicon. They have an efficiency rate of 13-16 percent, which indicates that they are able to convert 13-16 percent of the energy from the sun into electrical energy. Because of the variety of crystal structures that were employed in the production of these cells, they have a look that is instantly recognisable as being blue and speckled. Solar cells made of polycrystalline silicon are often sold at a lower price point than monocrystalline solar cells.

Thin-Film Solar Cells:

The manufacturing process for thin-film solar cells involves the deposition of layers of photovoltaic material onto a substrate consisting of either glass or metal. They have an efficiency rate of 7-13 percent, which indicates that they are able to convert 7-13 percent of the energy from the sun into electrical energy. These cells are able to be flexible and lightweight, qualities that make them well-suited for usage in applications and devices that can be carried around. Solar cells made from thin films are often the most cost-effective form of solar cell.

The amount of sunlight that is successfully transformed into useable electrical energy is referred to as the efficiency of a solar cell. In other words, it assesses how well the solar cell is able to transform sunlight into energy. The efficiency of solar cells can change based on a number of different parameters, such as the kind of solar cell, the quality of the materials that are used, and environmental conditions such as temperature and shadowing. Some thin-film solar cells have an efficiency of roughly 7 percent, while high-end monocrystalline solar cells have an efficiency of over 20 percent. Commercially accessible solar cells fall somewhere in between these two extremes.

Solar cell efficiency has been steadily increasing in recent years because to developments in both technology and manufacturing techniques. Researchers and engineers are always attempting to create novel solar cell manufacturing processes and methods, as well as new materials, in the hopes of improving the efficiency of solar cells. When it comes to establishing whether or not solar cells are cost-effective, efficiency is one of the most important factors. If the efficiency rates of solar cells can be increased, then more power will be able to be generated from the same amount of surface area.

As a result, monocrystalline solar cells are often the most efficient, but also the most costly, type of solar cell, whereas thin-film solar cells are typically the least efficient, but also the least priced. However, the cost-effectiveness of solar cells is also contingent on other factors such as the manufacturing processes, the prices of installation, and the incentives offered by the government. It is anticipated that as technology continues to improve, the efficiency of solar cells will grow, making solar energy a more realistic choice for satisfying our requirements for energy.

Q.5 Name two different types of wind machine and describe any one of them in  detail. 10

Ans) Horizontal-axis wind turbines (often abbreviated as HAWTs) and vertical-axis wind turbines (VAWTs) are the two primary categories of wind generators (VAWTs).

HAWTs, which stand for horizontal-axis wind turbines, are the most prevalent form of wind turbine and are frequently implemented in large-scale wind generating projects. They are made up of a tall tower that has a rotor installed horizontally on top of it. The rotor has three blades that are attached to it. The force of the wind causes the rotor to rotate, and a generator at the foot of the tower is responsible for converting the rotor's rotational energy into electrical energy.

On the other side, vertical axis wind turbines (VAWTs) have their axis of rotation in the vertical plane and are not as often utilised. In addition to having the ability to be constructed to be more compact and aesthetically pleasing than HAWTs, these turbines are commonly referred to as "eggbeater" or "darrieus" turbines. VAWTs feature blades that are positioned vertically around a central shaft, and they have the capability of being constructed to collect wind coming from any direction.

HAWTs are generally rather massive, with rotor diameters that can range anywhere from 80 to 120 metres or even farther. The blades have a structure that is optimised for aerodynamic performance, and they are constructed out of lightweight materials such as carbon fibre or fibreglass.

When there is a breeze, the blades are pushed against by the wind, which causes them to revolve around the rotor. The rotor is linked to a shaft, which is coupled to a gearbox that raises the rotor's rotational speed. The speed at which the rotor rotates is increased by the gearbox. The gearbox then drives a generator, which turns the rotational energy into electrical energy that may be used to power homes, companies, or the electric grid.

This electrical energy can be utilised to power homes, businesses, or the electric grid. HAWTs are primarily intended to function at wind speeds ranging from 10 to 25 miles per hour, with a maximum wind speed of around 55 miles per hour. They may be set up singly or in vast arrays, and their typical placement is in places that experience high wind speeds on a regular basis, such as coastal areas or the peaks of mountains.

The horizontal axis wind turbine (HAWT) is now the wind machine design that is the most often used. HAWTs make use of aerodynamic blades (also known as airfoils) that are attached to a rotor and have the ability to be positioned either upwind or downwind. HAWTs generally have either two or three blades and may achieve high speeds at the blade tips when in operation. Those machines that have upwind rotors need a yaw, also known as a tail vane, to assist them orient themselves towards the wind, but those machines that have downwind rotors have coned blades, which allow the turbine to align itself on its own. Downwind rotors, on the other hand, have been known to "wander" about while attempting to align themselves with the wind under low speed situations, which reduces the amount of energy produced by low wind speeds. This is one of the disadvantages of using downwind rotors.

Q.6 Discuss, in detail the classification of hydro-electric power plants on the basis of the capacity for water flow regulation 10

Ans) The ability of hydroelectric power plants to control the flow of water is one of the criteria that may be used to categorise these facilities. Typically, the type of dam or other structures that are used to manage the flow of water serves as the defining factor for each of these groups. According to their ability to control the flow of water, the following are the primary categories of hydroelectric power plants:

Run-of-River Power Plants

These kind of hydroelectric power facilities do not store a significant amount of water behind a dam to use as a reservoir. They do this by harnessing the power of the river's or any other water source's natural flow to produce energy. It is possible to guide water into a canal or pipeline that feeds the turbines by utilising a weir or a small-scale diversion dam. These power plants do not have the capacity to store water or to manage water flow since they do not have a huge reservoir at their disposal. As a consequence of this, you will often see them put to use in places that have steady and reliable water flows, such as mountainous regions that receive a lot of precipitation.

Storage Power Plants

Hydroelectric power plants that store water have big dams and reservoirs that may be utilised to generate energy whenever there is a need for it. Storage hydroelectric power plants. The dam serves to hold water, which is then periodically released through the turbines in order to produce energy. These power plants have the ability to control the flow of water farther downstream, which can aid in the prevention of flooding and the cultivation of crops. Small-scale power plants all the way up to large-scale facilities that are capable of producing thousands of megawatts of electricity can fall under the category of storage power plants.

Pumped-Storage Power Plants

During periods of low demand, extra electricity generated by pumped-storage hydroelectric power plants is used to push water from a lower reservoir to a higher reservoir. This process is called "pumping." When there is a strong demand for energy, water is let out of the higher reservoir so that it may be used to create electricity. Through the utilisation of this method, extra electrical power may be saved and then utilised during times of high demand. In order to maintain a consistent supply of electricity and maintain grid stability, pumped-storage power facilities are often put into action.

Tidal Power Plants

Electricity may be produced by tidal power plants by using the movement of the ocean's tides. Large underwater turbines that are powered by the movement of the tidal current are utilised in these power plants. Tidal power plants are able to reliably generate energy thanks to the predictability of tides, which allows them to be employed in many locations.

Q.7 Describe, in detail the two types of classification of photovoltaic (PV) systems. 10

Ans) The two types of classification of photovoltaic (PV) systems are:

Stand-alone PV systems

Stand-alone photovoltaic (PV) systems, which are often referred to as off-grid PV systems, are intended to function apart from the conventional electrical grid. In most cases, these systems are utilised in secluded places that are geographically or economically inconvenient for connecting to the main power grid. Solar panels, batteries, charge controllers, and inverters are the components that make up stand-alone photovoltaic, or PV, systems.

The sunlight is turned into direct current (DC) power by the solar panels, which is then stored in the batteries. The charge controller is responsible for regulating the charging process in order to avoid the batteries from being overcharged or discharged. The DC electricity that is stored in the batteries is changed by the inverter into AC electricity, which can then be utilised to power various appliances and pieces of equipment.

In houses, chalets, and other distant areas where energy is required but grid connection is limited, stand-alone PV systems are a typical and popular choice for power generation. They are also utilised in poor nations to give rural areas that do not have access to the grid with power. This is done using solar panels.

Grid-connected PV systems

Solar photovoltaic (PV) systems that are designed to link to the electric grid are able to offer power to a variety of structures, including houses, companies, and other establishments. Solar panels, inverters, and a metering system are the components that make up these systems. The solar panels transform the sun's rays into direct current (DC), which is then sent into the inverter to be changed into alternating current (AC). After that, the AC power is either added to the electrical system of the building or sent back into the grid.

Solar photovoltaic (PV) systems that are linked to the grid are often installed on roofs or in open areas that get adequate sunlight. They have a variety of uses, including residential, commercial, and even industrial use. In some circumstances, the PV system may be able to send any extra power it generates back into the grid, which may result in a credit being applied to the building's monthly electricity bill.

Q.8 Discuss in detail: 10

i) Vibration based Energy Harvesting

Ans) The method of converting mechanical vibrations into electrical energy is known as vibration-based energy harvesting, and it makes use of a device that is referred to as a vibration energy harvester (VEH). This technology has the ability to provide a sustainable source of power for small electronic devices, sensors, and wireless sensor networks. These things are often utilised in sectors such as the automobile industry, the aerospace industry, and the structural health monitoring industry. The piezoelectric effect refers to the capacity of some materials to create an electrical charge in response to mechanical stress or vibration. This phenomenon is the foundation of the primary theory of vibration-based energy harvesting, which is based on this effect. Within a VEH is a piezoelectric material that, when subjected to mechanical vibrations, creates a voltage that may be used to power an electrical load. This voltage can be utilised to power an electrical load.

There are several types of VEHs that are used for energy harvesting, including:

1. Cantilever beam VEHs: The piezoelectric material that makes up this variety of VEH is affixed to a cantilever beam. A voltage is produced by the piezoelectric material in the beam whenever it is exposed to mechanical vibrations, and this voltage may then be utilised to power an electrical load.

2. Electromagnetic VEHs: Magnets and wire wound into coils make up the components of this kind of VEH. A current of electricity is created in the wire coil by the movement of the magnet in reaction to mechanical vibrations. This movement causes the magnet to move back and forth.

3. MEMS-based VEHs: This particular kind of VEH makes use of the technology known as micro-electromechanical systems, or MEMS, to transform mechanical vibrations into electrical energy. VEHs that are based on MEMS technology are often more compact and energy-efficient than other types of VEHs.

   
   

    

ii) Piezoelectric Energy Harvesting

Ans) The term "piezoelectric energy harvesting" refers to a procedure that makes use of a piezoelectric material in order to transform mechanical energy into electrical energy. Piezoelectric materials are materials that create an electric charge when subjected to mechanical stress, such as pressure or vibration. Examples of this type of mechanical stress include vibration and pressure. These materials have the capability of converting mechanical energy into electrical energy, which makes them ideal for applications involving energy harvesting because of this property.

Piezoelectric energy harvesting can be used in a variety of applications, including:

1. Harvesting energy from vibrations: Piezoelectric materials are capable of transforming mechanical vibrations into electrical energy and can be employed for this purpose. This is especially helpful in situations where there is the presence of mechanical vibrations, such as in industrial machinery or transportation systems.

2. Harvesting energy from pressure: Piezoelectric materials can also be used to convert pressure into electrical energy. This is useful in applications where pressure changes occur, such as in medical sensors or industrial pressure sensors.

3. Harvesting energy from temperature changes: Alterations in temperature can also be converted into electrical energy with the help of particular piezoelectric materials. This is helpful in applications where temperature fluctuations take place, such as in temperature sensors or heating, ventilation, and air conditioning (HVAC) systems.

Q.9 What is tidal energy? Enlist and describe the various components of tidal energy generation system. 10

Ans) Tidal energy is a type of renewable energy that generates electricity by utilising the strength of ocean tides. This type of energy is known as wave energy. Tidal energy systems are often made up of a number of different components, including the following:

1. Tidal Barrages: Large dams that are constructed across a bay or estuary are referred to as tidal barrages. These dams are designed to collect the incoming tidal water and channel it into the turbines that power the electrical generators. The Bay of Fundy in Canada and the Rance River in France are two examples of places in the world that have significant tidal ranges and hence are ideal locations for the construction of tidal barrages.

2. Tidal Turbines: Tidal turbines are quite comparable to wind turbines, with the primary difference being that they are built to function submerged under water. These turbines are installed in regions that have high tidal currents, such as tidal channels or straits, in order to harness the energy that the tides provide. Because of the tidal current that is flowing through the turbine, the blades are caused to rotate, which results in the production of energy.

3. Tidal Lagoons: Tidal lagoons are sheltered areas of water that are linked to the open sea by means of a strait or entrance that is only a few hundred yards wide. These lagoons produce power by utilising the rise and fall of the tides inside them. When the tide is high, water comes into the lagoon via the inlet, and when the tide is low, water flows back out of the lagoon through the inlet. This causes the turbines to spin, which results in the generation of energy.

4. In-stream Turbines: In-stream turbines are comparable to tidal turbines; however, in-stream turbines are more compact and are intended to be installed in rivers and streams in their natural environments. These turbines are able to harness the kinetic energy of the moving water and convert it into usable electrical energy. In-stream turbines are often installed in locations where there is an existing strong current, such as in a river that is running at a rapid pace or next to a waterfall.

5.  Oscillating Water Columns: Devices known as oscillating water columns employ the rise and fall of waves as a source of energy to create electricity. These machines have a chamber that is partly filled with water and have a column of air that is sealed off from the rest of the chamber. The chamber is moved up and down by the waves, which causes the air within the chamber to be compressed and then released. This action drives a turbine, which in turn generates energy.

Q.10 Enumerate the various resources of biomass giving details of each. 10

Ans) Biomass is a type of renewable energy resource that is obtained from living species, such as plants and animals, or from organisms that have just passed away. There are a wide variety of diverse sources of biomass, each of which possesses its own set of distinctive qualities and attributes.

The following are examples of some of the most popular sources of biomass:

Wood: Wood is one of the sources of biomass that is utilised the most frequently. In both industrialised and developing countries, it is frequently utilised as a fuel for the purpose of both heating and cooking. Stoves, boilers, and other types of heating appliances may all benefit from the combustion of wood, which can be sourced from forests, sawmills, and other locations.

Agricultural Crops: In addition to being a potential source of biomass, agricultural crops such as corn, sugarcane, and soybeans can also be utilised in this capacity. These crops' waste products, like as stalks, husks, and straw, may be converted into biofuels like ethanol and biodiesel through a processing step called fermentation. These fuels, in turn, can be used to power cars and produce energy.

Animal Waste: A source of biomass can be obtained from the waste products of animals, such as manure and many other organic materials. These materials, once processed, can be converted into biogas, which is then capable of producing either energy or heat as a by-product.

Municipal Solid Waste: Another potential source of biomass is municipal solid waste, which includes food leftovers and yard trash, among other things. These materials can be converted into biogas through the use of processing equipment, or they can be burnt in facilities that convert trash into energy to produce power.

Algae: A source of biomass, algae is a kind of plant that thrives in watery environments and grows quite quickly. It is possible to convert algae into other types of biofuels, such as biodiesel, which may then be used to power cars and create energy.

Forestry Residues: As a potential source of biomass, the remnants of forestry operations such as bark and sawdust can be utilised. These materials may be combusted in boilers or utilised in the production of wood pellets, each of which may be used as a fuel for the heating process