PHYS1211 learning Goals

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1. Wind Power

Types of energy available from air

Air has various components of energy that are present and that can be drawn from it, some of these basic energies drawn from air include; air energy, compressed air energy storage, liquid air energy and natural energy. Among air energy is the most notable with wind energy being the most preferred and the one that is often commonly used in ensuring that there is enough energy (Prakash, and Dhal, 2021). All these are what is summed up as the forms of energy that is present in the air and what is called the various forms of energy in the air.

Estimation of power from a wind Turbulence

Under perpetual acceleration, kinetic energy of a body with mass m and velocity v is equivalent to the work done W in moving that object from rest to a distance s under a force F, i.e.

E = F = Fs. As per the Newton’s Law, we have: F =ma

This implies that; E =mas utilizing the third equation of motion: V² = U²+2as

Making a the subject, we get; a = $frac{(V2 – U2)}{2S}$ but since the preliminary velocity of the object is zero, i.e. U = 0, a = $frac{V2}{2s}$ Substituting it in equation (1), we get that the kinetic energy of a mass in motions is: E = $frac{1}{2}$mv² …………(2)

The power in the wind is given by the rate of change of energy: P = $frac{text{dE}}{text{dt}}$ = $frac{1}{2}$mv²$frac{text{dm}}{text{dt}}ldotsldotsldots(3)$ From all these equation factoring the density of air ρ. it can be deduced that the power;

P = ½ρAV³

Betz’s Law and what it means.

Betz’s law states that as air flows through a certain region and wind speed reduces due to energy loss due to turbine extraction, the airflow must disperse to a larger area. Resulting from this, any turbine’s efficiency is limited to a maximum of 59.3% due to geometry. This is a clear indication and illustration that a wind turbine can only collect 59 percent of the wind’s energy, the other version of this is what is defined as the power coefficient, represented as;

C_Pmax = 0.59, the representation C_p is often different from all the wind turbulence.

Why wind turbines cannot reach 100% efficiency.

It is important to note that the wind turbines cannot reach 100% efficient, this is due to such reasons like; the moving parts of the machines may have friction and also the is lost at the gears, and chances are that the alternator is often not 100% efficient in their making hence, all these factors contribute to the fact that the wind turbines cannot be 100% efficient.

Pros/cons of VAWTs and HAWTs

VAWTs: Advantages of Vertical Axis Wind Turbines (VAWTs) are as follows; these turbines have less apparatuses than those with a horizontally oriented rotating motor and blades. Since the gearbox and generator are close to the ground, the tower’s supporting strength isn’t as imperative. While disadvantages of VATs; the fact that not all of the blades create torque at the same time; vertical systems’ energy production efficiency is limited. Also, the wind turbines are located closer to the ground (M. Saad, 2014). The bearings can also wear out easily.

HAWTs: Advantages of Horizontal Axis Wind Turbines include; high power output as they can generate as high as between 2 to 8 MW all in regard to the usability. It also very efficient as it has a high conversion rate, statistically they can transform close to 50% of received wind into electricity. It is very reliable as their existence is perceived to be of maturity level and finally, they can be seen to be having a high operational speed that would not only impact their receive platform but also help them provide optimal performance.

Ways in which HAWT converts wind KE into electricity and the explanations for active blade twist and yaw control.

A wind turbine catches the wind and changes it into sustainable energy. The wind causes the rotor to spin, and the movement of the blades powers an energy-generating generator. Kinetic energy is created by the blades rotating. This is the energy that we transform into electricity. Magnets traveling through fixed coils of wire known as the stator convert wind energy into electricity. AC power is generated as the magnets travel through the stator.

After that, it’s converted to DC power. This can be used to charge batteries that store electrical energy or to feed power into the grid through a grid-interactive inverter.

The reasons for active blade twist and yaw control could always be very varied, but then if a rotor blade is struck at an angle of attack that is too steep, the blade will stop providing lift (Kurulekar et al., 2021). As a result, the rotor blade must be twisted to provide an ideal angle of attack along the blade’s length.

References

Prakash, S. J., and Dhal, P. (2021). Investigation of wind renewable energy system in Muppadal wind power station. 2021 7th International Conference on Electrical Energy Systems (ICEES). https://doi.org/10.1109/icees51510.2021.9383705

Kurulekar, M., Kumar, K., Joshi, S., Kurulekar, M., and Kulkarni, A. (2021). undefined. Materials Today: Proceedings. https://doi.org/10.1016/j.matpr.2021.04.061

M. Saad, M. M. (2014). Comparison of horizontal Axis wind turbines and vertical Axis wind turbines. IOSR Journal of Engineering, 4(8), 27-30. https://doi.org/10.9790/3021-04822730

2. Solar Power

Variances between metals, insulators and semiconductors in terms of the mobility of their electrons

Metals are defined as elements with free valence as they are very conductive because they have unbound electrons and partially filled valence bands. When a little quantity of electric current is applied to metals, the free electrons flow and act as a conductor. In metals, there is no prohibited energy gap and because of this, the number of electrons available for conduction increases, enhancing the material’s conductivity.

As for Insulators the valence band is totally fille while the conduction band is empty. As a result, there is a significant energy gap. There is no flow of electrons from the valence band to the conduction band because the energy difference between the conduction band and the valence band is greater (Platzer, and Hildebrandt, 2021).

The valence band of a semiconductor is totally filled with electrons, while the conduction band is empty. The energy difference between the bands is smaller. There is no electron transport from the valence band to the conduction band when the temperature is 0K.

Ways in which incoming solar photons can cause the movement of electrons in a circuit connected to a PV cell.

The “photovoltaic” action converts photons into electrons in photovoltaics (photo meaning light, and voltaic meaning electricity). The photovoltaic effect occurs when photons from the sun impact the surface of a silicon semiconductor material, causing free electrons to be liberated from the atoms. The term “photovoltaic” merely refers to the conversion of sunlight into electricity. An electric potential is produced between n- and p-type semiconductor layers when two different p–n semiconductor layers are brought into contact. Electrons pass across the junction and leap to the p-type semiconductor, leaving a static positive charge behind (Meyer, 2021).

Idea behind a solar furnace

A solar furnace is defined as a heating system that concentrates the sun’s rays using a concave mirror. Heliostats reflect the sun’s rays onto a series of parabolic mirrors in a solar furnace. The sun’s rays are then focused onto a furnace at the top of a tower by the parabolic reflectors. The furnace runs at a high temperature, usually above 800⁰C. The temperature of the molten salt in the furnace rises from around 300⁰ to over 600⁰C. The generator creates energy when the steam turbine is linked to an alternator through a gearbox. To cool the steam back down to condensate, modular cooling towers are employed. The generator’s generated power is sent into an electrical transformer, which boosts the voltage.

The economics of solar PV, and how it is growing

As technology advances and the cost of power provided by fossil fuels rises, solar energy becomes more economically appealing. Hundreds of billions of dollars in investment capital will very certainly increase worldwide solar-generating capacity by 20 to 40 times its current level by 2020. Solar energy generated by your solar panels may be used to offset your home’s electricity use and lower your utility bills over time. This can also help you save money on your energy costs each month.

References

Platzer, W. J., and Hildebrandt, C. (2021). Absorber materials for solar thermal receivers in concentrating solar power systems. Concentrating Solar Power Technology, 511-544. https://doi.org/10.1016/b978-0-12-819970-1.00001-3

Meyer, R., Schlecht, M., Chhatbar, K., and Weber, S. (2021). Solar resources for concentrating solar power systems. Concentrating Solar Power Technology, 73-98. https://doi.org/10.1016/b978-0-12-819970-1.00014-1

3. Hydro power

The two key kinds of turbines, and how they extract energy from water

Hydro turbines are allocated into two types: impulse and response. The type of hydropower turbine chosen for a project is determined by the height of standing water (known as “head”) and the volume of water flowing through the site. Further reflections include the depth to which the turbine must be buried, efficiency, and cost.

The runner of an impulse turbine is usually moved by the velocity of the water, and it discharges to atmospheric pressure. Each bucket on the runner is struck by the water stream. The water falls out the bottom of the turbine housing after striking the runner because there is no suction on the down side of the turbine. An impulse turbine is best suited to applications with high head and low flow.

The combined action of pressure and flowing water generates electricity in a reaction turbine. Rather than striking each blade separately, the runner is positioned immediately in the water stream running over them (Chidambaram et al., 2021). In comparison to impulse turbines, reaction turbines are often utilized at sites with lower head and larger flows.

Geothermal energy is based on the use of heat from inside the Earth to generate electricity. However, a toaster will not fit inside the nearest magma pocket. Seismic action tears up the rocks in some locations, such as Iceland and California, allowing water to circulate near geologic hotspots. Steam then rises to the surface, where it may be used to power turbines.

The other way is solar wind hybrid, her we build a tall tower with an upper lip, then spray it with a fine mist of water. The heat from the air is absorbed by the mist, which then evaporates. As a result, cold, dense air flows to the structure’s bottom, where it is directed via massive wind turbines that generate energy.

Comprehend the basic design elements of a Francis turbine.

Francis turbines are a hybrid of impulse and reaction turbines, in which the blades revolve utilizing both the reaction and impulse force of water flowing through them to produce additional energy. The Francis turbine is most commonly used to generate energy in medium and large-scale hydropower plants. Heads as low as 2 meters and as high as 300 meters can be utilized with these turbines. Furthermore, these turbines are advantageous since they function equally effectively when oriented horizontally as they do when oriented vertically.

The water enters these turbines radially, which means it enters perpendicular to the rotating axis. The water always flows inwards, towards the center, once it enters the turbine (Francis, Umesh, and Shivakumar, 2021). The water exits the turbine axially, parallel to the rotating axis, after passing through the turbine

Understand the implications of Bernoulli’s Equation for hydroelectric power.

The water enters these turbines radially, which means it enters perpendicular to the rotating axis. The water always flows inwards, towards the center, once it enters the turbine. The water exits the turbine axially, parallel to the rotating axis, after passing through the turbine. The Bernoulli equation is a crucial formula that connects a fluid’s pressure, height, and velocity at a single point in its flow (Johansen, 2021). In an idealized system, the connection between these fluid conditions along a streamline always equals the same constant along that streamline. Bernouli’s Equation: ρ + ½ρV² + ρgh = constant

References

Chidambaram, P., Thamilarasan, K., Barath Kumar, J., and Auxcilia Mary, L. (2021). A review on turbines in power production using wind and hydro energy. Materials Today: Proceedings. https://doi.org/10.1016/j.matpr.2020.12.1242

Johansen, K. (2021). Blowing in the wind: A brief history of wind energy and wind power technologies in Denmark. Energy Policy, 152, 112139. https://doi.org/10.1016/j.enpol.2021.112139

Francis, S., Umesh, V., and Shivakumar, S. (2021). Design and analysis of vortex Bladeless wind turbine. Materials Today: Proceedings. https://doi.org/10.1016/j.matpr.2021.03.469