EE1508 Introduction to Engineering Mechanics
ENGINEERING AND CONSTRUCTION
At present, the demand for energy has gone high, and people are looking for alternatives. Hydroelectric power is one of the options used. In this paper, I will discuss hydroelectricity from developmental stage to completion and factors associated with this project. Some researchers have covered this topic in detail and have outlined economic and environmental factors associated with a hydropower.
Hydroelectricity takes advantage of waterfall to generate a mechanical energy, which is converted into electrical energy by various devices. Over thousands of years, people used wooden wheels to convert the energy of motion into mechanical energy. Today, people are using flowing water to generate electricity. It’s the largest source of renewables in many nations. For the project to succeed, you need to consider some factors such as the construction of the dam, river source, economic, and environmental factors to the ecosystem and the people around. Therefore, the project demands both engineering and structural design processes.
Hydroelectric power plants are of different categories depending on the amount of power required and amount of water. They range from micro to large size. Micro-plant is the smallest power plant that produces power of less than 100kW. It serves a small region. However, the large plant generates more power of up to 30MW. Study show that hydroelectric power contributes one-tenth of the total energy to the national grid. For that reason, our country needs to construct more hydroelectric power plants to generate more electricity by taking advantage of sites that have potential.
A report released by US Hydropower Resource Assessment indicates that over hundred projects have a capability of generating more than 2000MW. As a result; our proposed hydroelectric power plant is located on river Schuylkill. The site has an existing dam called Flat Rock Dam.
The dam and canal were built the late 1810s with a potential capacity of 2.5MW.After many years had passed; the dam collapsed due to structural failure, but later rebuilt. The site for our plant is well positioned. During those days, the canal served as a means of transport especially for transporting industrial materials.
Review of existing schemes
Moving around UK and Iceland, we came upon Dinorwig Electric Mountain and Irafoss hydroelectric power plants. Irafoss is located on river Sog, Iceland, with a generating capacity of 31.0MW. The plant is connected to two turbines. It takes advantage of falling water to generate electric power. As demand for power was increased, a third turbine was connected which contributed 16.0MW. The plant was established with the aim of providing electricity to the capital of Reykjavik.
In the UK, the Dinorwig and Electric Mountain get water from constructed dams to generate power. Water falls from the reservoirs is directed to the turbines through penstock. And in the case of excess power, the water is taken back to the reservoir. The Electric Mountain has a generating capacity of 1.3Kw.And the two stations have a total head of 38.0m.
Aim of the project
The two plants are performing strongly in their country, but our interest is to come up with a hydroelectric power plant that is located in our region. We are going to focus on Flat Rock Dam in Manayunk, Pennsslynania. The plant we construct has to give 2500MW. The project will only be viable after considering economic costs and environmental implications.
It is very critical to look at the environmental effects of hydroelectric power plant to the animals, plants, and humans. If the advantages are more than the disadvantage, then the project can move on. Also, we have considered the economic history and current economics of the community, and therefore confirm that our project has to continue. Our designed hydroelectric power plant has correct engineering specifications that will make the plant to operate effectively and efficiently.
A hydroelectric power plant is accompanied with many substantial impacts on the surrounding site area. A dam and canal are not only constructed to generate electricity but also for controlling overflowing water. The natural environment will be interrupted by the hydroelectric power plant. But in our case, we have an existing dam, and we expect the least impact to the ecosystem. It is extremely important to analysis the overall consequences accompanying existence of a dam for the purpose of electricity generation.
The construction of a hydroelectric power station affects both the river and the ecosystem. The dam interferes with the free movement of the river water. The water is forced to pile up behind the barrier in the reservoir thus creating more pressure on the surrounding land walls. The occupied land could have been used for other purposes such as farming, residence, etc.
With time, the dam is full of sediments that interfere with the general volume of water. And because of this little volume of water, the plant generates less power. Also, the sediments screen water that flow downstream. The screened water flows with high velocity thus destroying the floor of the river and loss of ecosystem.
The local climate has to change slightly depending on the size of the dam. We all know that water cools and warm faster than the land; the presence of the dam will obviously interfere with the local weather. The regions near the dam will experience moderate temperature than those residing far. Danjianakau reservoir in Hubei China is a better example since winter temperature has increased and summer temperature reduced all by one degree (Rashad & Ismail, 2000).
Finally, construction of a dam can lead to earthquakes. During construction, the heavy machines cause the earth to generate waves that interfere with inactive faults. Also, the stored water exerts pressure on the underneath mass thus inducing earthquakes. Researchers from different institutions found out that Koyna Dam in India induced earthquakes. The depth of water contributed to the generation of the induced earthquake.
Plants and animals are directly affected by the construction of the dam. The land occupied by the dam was originally home to various animals and plants. We earlier noted that a large area of habitat is destroyed by large-scale flooding and thereby destroying life. A forested area before construction of the dam, encourages trees harvesting before the flooding begins. Also, some areas with cold climate loss submerged trees and vegetation.
Emergence of vegetation
The constructed dams full of solid materials and nutrient encourages the growth of aquatic weeds. Some tropical areas have been highly affected by these weeds. The weeds occupy the surface of the water body hence interfering with the general working system of the dam. The notorious weed is the Water hyacinth. The weed is evidenced in Lake Brokopondo in Surinam. It has covered half of the lake.
These weeds have many negative effects on the dam, plant, and even to the neighboring area. The weed can lead to loss of water due to a high rate of evapotranspiration. Second, the weed interferes with plant components such as clogging in the screens. Third, the weed interferes with channels, especially for irrigation channels. Fourth, the weeds deny fish space and nutrients. Fifth, the weed provides a favorable environment for spread-disease-organisms such as the mosquitoes, among others.
It is extremely hard to do away with these weeds. The methods used to control them are tedious and expensive. Mechanical, chemical, and biological are the commonly used methods. The mechanical method is most applicable to shallow reservoirs. But chemical and biological methods are mostly used in deep dams. Chemical means seems to work best, but the side effect is too much to the environment. The biological method is the effective one since aquatic organisms and fish directly feeds on the plant thereby interfering with its growth (Zhong &Power, 1996).
Animals are most affected when a dam is build. When dam projects are proposed, people worry about the lives of animals. The process of moving these animals to a safer area is costly. In Africa, when Volta Dam was constructed, all animals were moved by rescue operations. Many animals loosed their life in the process of moving. Our environmental laws are not applicable to the world, and therefore many unique habitats are loosed (DOE, 2012)
Some fish such as Salmon have loosed their life-cycle due to dam construction. These fish hatched in freshwater at the upper-stream environment but spent most of their time in the sea. Also, eel fish that hatched in the sea then migrate to upstream. They (eel) have loosed their life-cycle. As such, dam construction interferes with the life of these fishes. The best scenario happened in Pacific Northwest of USA. Therefore, we need to avoid fish mortality by incorporating suitable screens in our power plant. They will prevent fish from passing through turbines.
However, construction of a dam may have a positive effect to the environment. When Lake Nasser in Egypt was constructed the fish production increased by 40 percent.
People are forced to move when a dam is constructed. For our case, the power plant will displace some people to new areas. According to Guo, Xiao, and Li (2000), the Three Gorges Dam Project in China displaced more than one million people. These people ended up living in merged villages. They loosed their ancestral roots. More studies show that in Africa, people lose their shrines, gods, and ancestral graves, and the culture of these people disappears.
Large scale-scale projects may have a positive effect to some people especially those residing at the downstream if the flood is well managed. Taking the case of the Three Gorges Dam in China, many peoples’ lives will be saved. It is estimated that over 15 million people will directly benefit from the project if it succeeds. Also, the project will increase recreational activities to the community.
Economic aspects of hydroelectric power
Economics involves the production, distribution, and consumption of goods and services by the society. It is important to understand the economics involved in constructing a hydropower plant in our local area (Manayunk). The economy of the area will change. Globally, hydroelectric power plants have changed the economies of many nations. Many people get employed, and new businesses emerge as the population of the region increases.
Flat Rock Dam Economics
Flat Rock Dam is our current project situated at Philadelphia on river Schuylkill. This site has an existing built dam but no electricity generated. We need to update and make some changes in our design so that we can understand the immediate environment, and know the economics involved in the maintenance of the dam, power distribution, and the best way to engage people in the project.
The dam is located in Manayunk town. The town has seen great development because of river Schuylkill. The river serves as a means of transport and trade. The name Flat Rock Dam was borrowed from the town because it was originally called Flat Rock town.
The dam was built the late 1810s and contributed to the prosperity of the town. Communication also improved within the town and neighboring areas.
The dam eased a difficult area of the watercourse where Rummell’s fall was. The region was only accessible when volume of water increased. Many settlers, especially from England, operated large numbers of mills within the town. Local people got jobs and other people engaged in businesses (Cushman, 1985).
We have evaluated the plant by considering the existence of the dam, land rights, and economic costs associated with maintenance and renovation of the dam. Flat Rock Dam is owned by Pennsylvania Department of Environmental Protection’s Bureau of Abandoned Mines Reclamation (BAMR). However, the boat launch and picnic area that links the pool and dam are maintained by the Lower Merion Township. Powerboats in the pool area are faced with controversy.
Politics are being played over the economic costs of maintaining and environmental implications of the dam. We, therefore, remain with the question of either make the dam to generate the power or just maintain it. Over the years, people have directly or indirectly benefited from the dam. Once, the dam was destroyed by the flood but rebuilt. The costs involved were high. In spite of rebuilding, the dam no longer generates electricity to the local people.
The dam is not serving the Manayunk people right. It has become a liability to the society. The available technological advancements show that the electricity produced by this dam will not be of use because the local people are served by other power plant stations from outside.
Building a hydropower plant
The proposed hydropower plant will be built on a new site. The knowledge and experiences gained from the above factors have led us to choose this site. The site is suitable to our design variables to the power plant. The engineering specifications are factored by considering the size and depth of the dam. The location of the dam is geologically fine to withstand the load of the water and structural components. The pressures exerted by water will not interfere with the retaining walls (Yeh, 1985).
The local people need a fluctuating power since most electricity is used during peak hours. The demand is usually high and therefore all power providers need to consider this when generating power. Some power providers have Natural gas-fired plant that automatically switches on to arrest the surge. However, these plants emit harmful gasses to the environment because of burned natural materials. Therefore, a hydroelectric power offers the best option since it addresses the demand with less or no harm to the environment.
All of the hydroelectric power plants in the country are overseen by the Idaho National Engineering and Environmental Laboratory (INEEL). The department has documented all data for all sites in the country and numerous variables concerning power production from each location. Major rivers that can allow dam construction in Pennsylvania are provided with potential power capacity (IHA, 2013). The figure below illustrates the power available from each river.
Figure 1.Potential megawatts of undeveloped hydropower sites.
The discussion below highlights viability of Flat Rock Dam in Manayunk in line with environmental factors and economic costs.
The INEEL has provided us with valuable data that will enable us to continue with our project so that can generate power of 2500MW.The Flat Rock Dam fits our site of the plant. The plant will be of great use to the community since the Sustainability Factor for the project is high. The table below provides a strong argument for the project to move on.
Figure 2. Project Environmental Sustainability Factors.
The figures from 0.1 to 0.9 indicate the Sustainability Factors for the project on the environment.0.9 shows that the project will have the least impact on the natural environment.
With 0.9 for Manayunk, the site remains ideal for a hydroelectric power plant. The environmental effects are minimal, and therefore the plant has to be built.
Construction of the plant
You need to consider various factors such as the size of the dam, retention capacity, the weir, and control gates in the development of the power plant. In our case, we need to achieve a maximum head of 6.4m and an average stream flow of 256.83 cubic meters per second. With this, we generate electric power of 2500Kw (Masters, 2013).
The calculation below leads us to the power generation of 2500Kw.
From the above calculation, we need to divert about 19% of the stream flow. Taking more than 19% of the water can cause harm to the environment.
Plant specifications are important because it’s from these specifications that we can achieve a power of 2500Kw. In our project, we need a head of 26.4m that will enable the facility to work effectively and efficiently to produce intended electric power. The presence of the dam is to facilitate the flow rate.
The figure below indicates all components of the designed power plant.
Figure 3.Internal section of a hydropower plant
It provides entrance to the incoming water to the power plant. It is composed of valves and control gates that regulate the flow of water. The valves come in different design types depending on the function. We have rotary, butterfly, and thru flow. For us, we are using thru flow because it has less head loss and leakage (EIA, 2011).
It is located adjacent to the intake and serves the following purposes; one allows the water to enter into the power plant. Second, diverts the flow of water in case of maintenance. Three, prevents solid materials for accessing the plant components. The second stage is the intake Weir which serves three purposes; allowing entry of water to the power plant system, diverting the flow of the water, and lastly holding sediments from accessing the system components. In our scheme, we will use side intake with Weir design. It is more flexible and most economical.
It is a hollow cylinder that carries the water from the reservoir to the turbines. Its construction is very important because the component determines the amount of the power that will be generated. Factors such as surface roughness, soil type, terrain, etc., play a big role in the design of the penstock. Therefore, the penstock should take a large share of the total cost of the plant (Dursun & Gokcol, 2011).
The turbine receives water from the penstock. The incoming water turns the turbine shafts, hence a mechanical energy is generated. In our plant, we have used medium head turbine so that the cross-flow serve us better.
It is the last component attached to the power plant that takes water back to the river.
Transformers, generators, and electricity production
The water from the penstock turns the shaft in the turbine to create mechanical energy. The mechanical energy is converted to electrical energy by generators and transformers.
It is a device that converts mechanical energy into electrical energy. It has a shaft, rotor, exciter, and a stator. The rotor has electromagnets that rotate inside the stator. As the electromagnets continue rotating, a magnet field is created, and an alternating current is generated.
It is a device that receives the voltage generated by the generator and steps up or down into a suitable form. The stepped up or down voltage is then transported to the regional grid. Once the voltage is at the regional grid, it’s distributed to various consumers.
The feasibility study conducted concerning the environmental implications and economic costs enabled us to implement the designed hydropower plant in our local region.The research carried out concerning the Flat Rock Dam found that the dam had little impact on the environment and the costs involved in the renovation are manageable and therefore enabled us to implement our project. The site chosen was suitable for the plant development because the required head was achieved by generating 2500MW (Castaldi, Windram &Ziatyk,2003).
From economic point of view, the hydroelectric power project would offer energy and employment to the community. The costs involved are very low as compared if we had to construct a new dam. Therefore, the costs involved in the project are justified because the community of Manayunk will benefit. From the two factors discussed above(economic costs and environmental implications) make the Flat Rock Dam to be a potential site for hydropower.
New technologies used in the development of hydropower with little or no harm to the fish provides new opportunities to the industry. The hydropower plant if well constructed and maintained so that environmental and cultural implications are few, the project can provide clean electricity at low cost. Harnessing flowing water from rivers to generate power is a better option instead of relying on natural fossil fuels that harm our climate and public health.
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