Renewable energy

Renewable energy

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  “Heaven’s light isour guide” RAJSHAHI UNIVERSITY OF ENGINEERING & TECHNOLOGY DEPARTMENT OF MECHATRONICS ENGNEERING 1st Year, Even Semester, Session: 2018-2019 Course No: ME 1256 Course Title: Thermodynamics and Heat Transfer Sessional. Assignment No: 01 Assignment Title: An assignment on Renewable Energy. SUBMITTED BY: A. K. M. MOHIBUR RAHMAN ROLL-1808030 SUBMITTED TO: Md. Robiul Islam Lecturer Department of Mechatronics Engineering Rajshahi University of Engineering & Technology Dip Kumar Saha Lecturer Department of Mechatronics Engineering Rajshahi University of Engineering & Technology
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  RENEWABLE ENERGY Introduction: Renewable energyis energy from sources that are naturally replenishing but flow-limited; renewable resources are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Renewable energy is the energy that is generated from natural processes those are continuously replenished. This includes sunlight, geothermal heat, wind, tides, water, and various forms of biomass. This energy cannot be exhausted and is constantly renewed. The term renewable energy is used to describe energy that is obtained from natural resources. Actually it comes from natural resources those do not deplete. It is sustainable and does not result in a high degree of pollution. Sources of renewable energy include sunlight, wind, water, biomass, and tides. Renewable energy is used for a variety of industrial and domestic activities. Many countries have been substituting non-renewable energy for renewable energy due to the latter’s low environmental impact. Renewable Energy sources: The major types of renewable energy sources are • Hydropower • Geothermal • Wind • Solar • Ocean • Biomass o Wood and wood waste o Municipal solid waste o Landfill gas and biogas o Ethanol o Biodiesel
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  1. Hydropower Energy: Hydropoweror water power (from Greek: ὕδωρ, "water") is power derived from the energy of falling or fast-running water, which may be harnessed for useful purposes. Since ancient times, hydropower from many kinds of watermills has been used as a renewable energy source for irrigation and the operation of various mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery at a distance. ❖ How hydropower is captured: A typical hydroelectric plant is a system with three parts: a power plant where the electricity is produced, a dam that can be opened or closed to control water flow, and a reservoir where water is stored. The water behind the dam flows through an intake and pushes against blades in a turbine, causing them to turn. The turbine spins a generator to produce electricity. The amount of electricity that can be generated depends on how far the water drops and how much water moves through the system. The electricity can be transported through long-distance electric lines to homes, factories, and businesses. Other types of hydropower plants make use of the flow through a waterway without a dam. Fig 01: Hydropower Plant.
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  2. Geothermal Energy: Geothermalenergy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of materials (in currently uncertain but possibly roughly equal proportions). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, drives a continuous conduction of thermal energy in the form of heat from the core to the surface. The adjective “geothermal” originates from the Greek roots “ge”, meaning earth, and “thermos”, meaning hot. ❖ How geothermal energy is captured Geothermal springs for power plants. Currently, the most common way of capturing the energy from geothermal sources is to tap into naturally occurring "hydrothermal convection" systems, where cooler water seeps into Earth's crust, is heated up, and then rises to the surface. Once this heated water is forced to the surface, it is a relatively simple matter to capture that steam and use it to drive electric generators. Geothermal power plants drill their own holes into the rock to more effectively capture the steam. Fig 02: Geothermal Plant.
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  3. Wind Energy: Windis a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetative cover. This wind flow, or motion energy, when "harvested" by modern wind turbines, can be used to generate electricity. Wind power is a sustainable and renewable energy, and has a much smaller impact on the environment compared to burning fossil fuels. ❖ How wind energy is captured: The terms "wind energy" or "wind power" describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity to power homes, businesses, schools, and the like. Wind turbines, like aircraft propeller blades, turn in the moving air and power an electric generator that supplies an electric current. Simply stated, a wind turbine is the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. Fig 03: Wind Mill.
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  4. Solar Energy: Solarenergy, radiation from the Sun capable of producing heat, causing chemical reactions, or generating electricity. The total amount of solar energy incident on Earth is vastly in excess of the world’s current and anticipated energy requirements. If suitably harnessed, this highly diffused source has the potential to satisfy all future energy needs. In the 21st century solar energy is expected to become increasingly attractive as a renewable energy source because of its inexhaustible supply and its nonpolluting character, in stark contrast to the finite fossil fuels coal, petroleum, and natural gas. ❖ How solar energy is captured: Solar radiation may be converted directly into electricity by solar cells (photovoltaic 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 different semiconductors. The power generated by a single photovoltaic cell is typically only about two watts. By connecting large numbers of individual cells together, however, as in solar- panel arrays, hundreds or even thousands of kilowatts of electric power can be generated in a solar electric plant or in a large household array. 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. Fig 04: Solar Plant.
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  ❖ How capturedsolar energy is converted into household works: Fig 05: Capturing Solar Energy.
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  5. Ocean Energy: Oceanenergy refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences. The movement of water in the world’s oceans creates a vast store of kinetic energy, or energy in motion. Some of this energy can be harnessed to generate electricity to power homes, transport and industries. The term ocean energy encompasses both wave power i.e. power from surface waves, and tidal power i.e. obtained from the kinetic energy of large bodies of moving water. Offshore wind power is not a form of ocean energy, as wind power is derived from the wind, even if the wind turbines are placed over water. The oceans have a tremendous amount of energy and are close to many if not most concentrated populations. Ocean energy has the potential of providing a substantial amount of new renewable energy around the world. ❖ How wave energy is captured: • Using Wave Profile Devices: The pitching and heaving of the waves causes a relative motion between an absorber and reaction point. The left hand wave energy device above, uses a heavy ballast plate suspended below the floating buoy. The buoy is prevented from floating away by a mooring line attached to a sea-floor anchor. This mooring line allows the point absorber to operate offshore in deeper waters. As the buoy bobs up-and-down in the waves, a oscillatory mutual force reaction is generated between the freely moving absorber and the heavy plate causing a hydraulic pump in between to rotate a generator producing electricity. The middle wave energy device operates in a similar manner to the previous floating buoy device. The difference this time is that the freely heaving buoy reacts against a fixed reaction point such as a fixed dead-weight on the ocean floor. As this type of point absorber is bottom mounted, it is operated in shallower near shore locations. Fig 06: Wave Profile Devices.
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  • Using OscillatingWater Column: As the incident waves outside enter and exit the chamber, changes in wave movement on the opening cause the water level within the enclosure to oscillate up and down acting like a giant piston on the air above the surface of the water, pushing it back and forth. This air is compressed and decompressed by this movement every cycle. The air is channeled through a wind turbine generator to produce electricity as shown. The type of wind turbine generator used in an oscillating water column design is the key element to its conversion efficiency. The air inside the chamber is constantly reversing direction with every up-and-down movement of the sea water producing a sucking and blowing effect through the turbine. If a conventional turbine was used to drive the attached generator, this too would be constantly changing direction in unison with the air flow. To overcome this problem the type of wind turbine used in oscillating water column schemes is called a Wells Turbine. Fig 07: Oscillating Water Column. • Using Wave Capture Device: The basic impoundment structure can be either fixed or a floating structure tethered to the sea bed. The wave overtopping device uses a ramp design on the device to elevate part of the incoming waves above their natural height. As the waves hit the structure they flow up a ramp and over the top (hence the name “overtopping”), into a raised water impoundment reservoir on the device in order to fill it. Once captured, the potential energy of the trapped water in the reservoir is extracted using gravity as the water returns to the sea via a low-head Kaplan turbine generator located at the bottom of the wave capture device.
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  Fig 08: WaveCapture Device. ❖ How tidal energy is captured: • Using Tidal Barrage: A Tidal Barrage is a type of tidal power generation that involves the construction of a fairly low dam wall, known as a “barrage” and hence its name, across the entrance of a tidal inlet or basin creating a tidal reservoir. This dam has a number of underwater tunnels cut into its width allowing sea water to flow through them in a controllable way using “sluice gates”. Fixed within the tunnels are huge water turbine generators that spin as the water rushes past them generating tidal electricity. Tidal barrages generate electricity using the difference in the vertical height between the incoming high tides and the outgoing low tides. As the tide ebbs and flows, sea water is allowed to flow in or out of the reservoir through a one way underwater tunnel system. This flow of tidal water back and forth causes the water turbine generators located within the tunnels to rotate producing tidal energy with special generators used to produce electricity on both the incoming and the outgoing tides. Fig 09: Tidal Barrage.
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  • Using TidalStream: A Tidal Stream Generation system reduces some of the environmental effects of tidal barrages by using turbine generators beneath the surface of the water. Major tidal flows and ocean currents, like the Gulf Stream, can be exploited to extract its tidal energy using underwater rotors and turbines. Tidal stream generation is very similar in principal to wind power generation, except this time water currents flow across a turbines rotor blades which rotates the turbine, much like how wind currents turn the blades for wind power turbines. In fact, tidal stream generation areas on the sea bed can look just like underwater wind farms. Fig 10: Tidal Stream.
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  6. Biomass Energy: Biomassenergy is any kind of energy that uses a biological organism (plant or animal) as its source. Because the definition of biomass is so broad, fuels that can be considered "biomass" include a wide variety of items and researchers are discovering new biomass energy sources all the time. Animal manure, landfill waste, wood pellets, vegetable oil, algae, crops like corn, sugar, switch grass, and other plant material—even paper and household garbage—can be used as a biomass fuel source. Biomass fuel can be converted directly into heat energy through combustion, like the burning of a log in a fireplace. In other cases, biomass is converted into another fuel source; examples include ethanol gasoline made from corn or methane gas derived from animal waste. ❖ How to produce Biomass energy: All biomass energy production methods ultimately rely on the process of photosynthesis in plants, where plants capture sunlight, carbon dioxide from the air, and water and use them to produce carbohydrates. These plant-based carbohydrates are the materials that are used to produce biomass energy. In general, the two methods for producing biomass energy are by burning the biomass directly and through the gasification of biomass. • Direct burning of biomass materials: The biomass materials are burned and the heat that is produced is used to heat water into steam. The steam is then sent through a steam turbine, which generates electricity. • Gasification: Wet biomass, such as manure or food waste, undergoes fermentation in a special tank, producing methane. Dry biomass, such as agricultural waste, is subjected to high temperatures in the absence of oxygen, producing synthesis gas (syngas). The gas produced through either process is then burned to produce electricity in a gas engine or a gas turbine. • Fuel Cells: If the syngas is pure, it can be utilized in fuel cells for electricity production. This is not yet a commercially-available technology.
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  ❖ Cycle ofBiomass: The Figure below shows how Biomass is cycle is continuing day by day: Fig 11: Cycle of Biomass.
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  Renewable Energy ata glance: Fig 12: A Village of Renewable Energy. Advantage and Disadvantage of different renewable energy sources: Fig 13: Advantages & Disadvantages.
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  Advantages of RenewableEnergy 1. Renewable energy is eco-friendly: It is a clean source of energy, meaning, it has low or zero carbon and greenhouse emission. Fossil fuels emit high levels of greenhouse gas and carbon dioxide, which are greatly responsible for global warming, climate change, and degradation of air quality. Fossil fuels also contribute to sulfur emission to the atmosphere leading to acid rains. Acid rains can cause damage to buildings. Solar and wind power are considered eco-friendly because they emit zero toxic gases to the environment. The use of renewable energy dramatically reduces the dependence on fossil fuel as a source of energy, hence, cutting back on air pollution. 2. It’s a renewable resource: This implies that they do not deplete over a lifetime and there is zero possibility that they will run out (sustainable source of energy). Sources of energy like fossil fuels (oil, gas, and coal) are considered limited resources and there is strong possibility that they will run out in the future. Renewable energy can help developing countries from over-reliance on fossil fuels. Powerful winds, heat emanating from beneath the earth, sunshine and moving water can guarantee a huge and steady energy supply to a nation for many years. 3. Renewable energy is a reliable source of energy: In the previous few decades, the use of fossil fuel has sharply increased. This over-reliance on fossil fuels has led to our security being threatened. Fossils fuels are prone to trade disputes, political instabilities, spike in energy prices and unnecessary wars. These variables affect a lot more than a nation’s energy policies; they can significantly drain a county’s economy. Although most argue that solar and wind energy are unreliable, a solid infrastructure puts this argument to rest. If solar and wind plants are distributed over a large geographical location, there can be minimal electricity generation interruption because weather disruptions in one location cannot be the same in other locations. 4. Leads to job creation: Renewable energy makes real economic sense because it is a cheaper alternative to most traditional sources of energy. Since the inception of renewable energy, new and stable jobs have been added to most world economies. For, instance, in Germany and UK, many jobs have already been created thanks to their relentless efforts to develop and encourage the use of renewable forms of energy. Experts project that with the ongoing rigorous campaigns to embrace renewable energy, thousands of stable jobs will be created. 5. Renewable energy has stabilized global energy prices: Change up to renewable sources of energy means stability of energy prices across the globe. This is because the cost of renewable energy depends on the initial cost of installation of renewable energy technologies as opposed to fossil fuels, which increase and decrease
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  depending on thecurrent inflation and availability of the resource. Respective governments would only need to cater to the initial costs and that’s it. 6. Less maintenance of facilities: Once infrastructure for the harnessing of the renewable resource is laid down, there is low to zero maintenance required. This means that the owners of the facilities will reap big profits while providing cheap electricity to the population. 7. Boosts public health: This is a no-brainer. If governments took upon themselves to build more renewable energy facilities, the population would enjoy the health benefits. According to a study by the U.S. Environmental Protection Agency, Americans spend approximately $361.7 to $886.5 billion every year on overall health of the population. A big chunk of this budget goes to mitigate and cure diseases related to fossils fuel use like heart diseases, cancer, and neurological disorders. Greenhouse, carbon and sulfur compounds emitted by fossils fuels are risky to our health if inhaled over time. This is reason enough to consider renewable energy moving forward. 8. Empowering of people in the countryside: Renewable energy generation mainly takes place in remote settings. This means that local towns would get a fair share of power generated, ultimately, catalyzing the regeneration of those depressed areas both socially and economically. Electrification of those areas will open up untapped opportunities for development through the advancement of greenhouses using geothermal power, district heating of towns and communities through hot water generated by the energy exploitation of forestry and agricultural biomass. Disadvantages of Renewable Energy 1. Not every form of renewable energy is commercially viable: Many forms of renewable energy must be collected at a specific location, which means distribution networks must be setup to take advantage of the power that can be generated. These networks require a massive fossil fuel investment that can take generations to neutralize with the use of renewable energy. From tidal power to geothermal, the commercial viability of many renewable energy resources is not available right now. 2. Many forms of renewable energy are location-specific: Even solar energy has limited potential in some locations. In Seattle, Washington, just 71 days per year are classified as “sunny,” or having a cloud cover that is less than 30%. Northern cities may go prolonged periods without any sunlight during the winter months. Because renewable energy is often location-specific, it may not be available for every community to use.
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  3. Many formsof renewable energy require storage capabilities: With traditional power resources, a home or business is connected to a local distribution grid so that it can be accessed 24/7. When using a renewable energy resource, back-up and storage resources must be included with the power generation opportunity. Sunlight doesn’t happen at night. Wind speeds are not always consistent. The storage capabilities that are required can push the cost of a new renewable energy system beyond what the average person or community can afford. 4. Pollution is still generated with renewable energy: Renewable energies are cleaner than most fossil fuels, but “cleaner” and “clean” are very different terms. A resource like biomass still burns waste products and puts pollution into the atmosphere. This includes carbon and methane, which are classified as greenhouse gases. The technologies and facilities that are used to build renewable energy resources require fossil fuels, as do the transportation and distribution networks. In many instances, renewable energy relies on fossil fuels, whereas fossil fuels do not rely on renewables. 5. Renewables often require subsidies to make them affordable: In the United States, an emphasis on biofuels and renewable energies led to the creation of ethanol as a crude oil replacement. Despite taxpayer-funded subsidies in place for this corn- based fuel, only 430,000 barrels per day were produced in 2007. That was enough to replace 2% of the oil that was being consumed while corn prices skyrocketed because of the crops being funneled into this renewable fuel. 6. Some forms of renewable energy require a massive amount of space: To produce 20 megawatts of energy, current solar technologies require 100 acres of space. In comparison, the footprint for a nuclear power plant is 1 square mile to produce 1,000 megawatts of energy. Solar is therefore 45 times less space efficient compared to nuclear power. Solar is even worse, requiring up to 360 square miles to produce the same energy as one nuclear power plant. 7. Low-efficiency levels: Renewable energy technologies are still significantly new to the market, meaning, they still lack the much-needed efficiency. This poses forecast problems and investors may shy away from investing their money for fear of not getting returns pretty quick. Conclusion: The advantages and disadvantages of renewable energy show us that this technology has great potential. We have yet to realize its full potential, however, because of certain limitations that come with renewables, with more investments into this technology, prices can be lowered, jobs can be created, and the transition toward the consumption of fewer fossil fuels can happen.