Table of Contents
Hydropower is a clean source of energy. It is a renewable energy source due to the hydrological cycle (Wagner & Mathur 2011, p.108). The hydropower schemes use turbines to convert the mechanical energy of water into electrical energy. The hydropower production is cost-effective in terms of maintenance, long-life, and installation, efficient, and environmental friendly (Blume 2016, p.35). However, the plants face problems such as that of unsustainability and uncertainty of power production since they are dictated by seasons. The challenges are probably why some developed countries are producing small power from hydropower sources. The paper thus focuses on shading more light on the sustainability and certainty of hydropower by presenting the system complexities, analysis, and suggesting possible solutions to the challenges.
There are several process both physical and control process involved in hydropower system. Some of the processes are thermodynamics, heat generations, heat transfer, and energy losses.
In hydropower schemes, the thermodynamics as a process is involved. Thermodynamics is useful in evaluating both the quality and quantity of the system; exergy and energy analysis (Doost & Majlessi 2015, p.99). There is need to maximize the highest power possible out of the hydropower plants. The First Law of Thermodynamic guides the energy conservation hence giving the balanced enthalpy in the system (Allen, Hammond, & McKenna 2017, p.510). The First Law of Thermodynamics is applied in determining the amount of the water that would be converted through the turbines to produce electricity. In energy conversion, some percentage is converted to useful work while other percentage goes to waste in forms of other energy. Therefore, this law of thermodynamics is essential in determining the efficiency by relating the input and the output. The analysis of the first law is commonly known as the energy analysis since it provides the analysis based energy and estimation of energy losses at various parts of the hydropower system or any other system.
The First Law of Thermodynamics as already stated is important for determining the efficiency of the system through the relating quantities at the start of the process and the end of the process. However, it does not provide anything on the quality of the system. It is for this deficiency that the hydropower system calls for the Second Law of Thermodynamic. It is the second law that optimization is performed (Allen, Hammond, & McKenna 2017, p.510). The second law applies in the exergy analysis. Exergy analysis considers the ambient environmental factors and other factors in the system and analyses them to achieve the points at which optimum values would be attained (Allen, Hammond, & McKenna 2017, p.510). Therefore, this law is applied for determining quality in the system; by first determining the parts of the system of high degradation and then making exergy adjustments. Thermodynamics is also important in evaluating the behavior of hydropower system in various states (Vereide, Tekle, & Nielsen 2015, p.1). In general, thermodynamics is applied in hydropower system for determination of the efficiency of the system and optimization of the output.
The energy loss is another physical process encountered in the hydropower system. The energy losses as already seen in the discussion of Thermodynamics is considered when conducting the Thermodynamic analysis. The diagram below is a diagrammatic representation of the hydropower components which helps in explaining the energy losses in the hydropower system.
Figure 1: Fundamental components of hydropower system (Gatte & Kadhim 2012, p.100).
Energy losses occur at various sections on parts of the system. For example, the civil construction of the system involves changing the direction water among others depending on the design. Turbulence results from the designing new direction flow of water (to the required direction). The sudden alterations of the direction of flow lead to energy losses (Gatte & Kadhim 2012, p.100). The energy losses thus begin from the structures put in place to direct water to the powerhouse for producing electricity. Before water enters the powerhouse, turbulence and friction are the major contributors to energy losses (Wagner & Mathur 2011, p.43). In the powerhouse, the kinetic energy rotates the turbines.
There are various turbines, and their efficiencies vary. For example, Turgo turbines efficiencies reach 87% (Gatte & Kadhim 2012, p.108). The efficiencies of other turbines may go up to 95% based on the design of the turbine (Wagner & Mathur 2011, p.43). Turbines lose power in the form of mechanical losses such as friction. The turbine rotates in magnetic coils in the generator to generate electrical energy. In the process of this conversion, energy losses occur in the form of friction losses, copper losses, and iron losses (Doost & Majlessi 2015, p.99). From the generators, power is transmitted through transformers which also experience magnetic and electrical losses. Therefore, energy losses are clear physical processes in the hydropower system and proper analysis and designs are necessary to optimize the power output.
Heat generation and heat transfer
Generators are among the most vital parts of the hydropower system since it where the mechanical energy in the turbine is transformed into electrical energy. In the process of this conversion, power losses are experienced through friction, copper, and iron losses. All these forms of losses turn to heat (Doost & Majlessi 2015, p.99). Therefore, in a pure hydropower system where electrical power is the kinetic energy of water is transformed directly into the electrical power, the primary source of heat generation is through generators. But if water is turned is heated in the boilers so that the steam is used in generating electricity then boilers become the major source of heat generation.
The heat generated calls for the cooling system to ensure that all the equipment work at their optimum point of operation as dictated by the Laws of Thermodynamics. The power plan generators are cooled through air-cooled radiators (Doost & Majlessi 2015, p.98). The heat from the radiators is passed to the heat exchangers where the heat transferred to the water (Vereide, Tekle, & Nielsen 2015, p.2). The water used in these heat exchangers is supplied from the nearest source of water such as lakes and rivers. The temperature of the water or fluid leaving the heat exchangers and the water entering the heat exchanges determine the rate of heat transfer (Doost & Majlessi 2015, p.105). The dominant heat transfer processes in the hydropower system are convection, radiation, and conduction (Vereide, Tekle, & Nielsen 2015, p.1). Heat transfer helps in cooling the system for the realization of better-operating conditions. The physical process relates to one another. Therefore, control processes are applied to coordinate the smooth working of the physical processes. For example, when heat generation is higher, a correspondingly high rate of heat transfer should be in place to avoid much accumulation of heat in the system. Physical and controlling processes thus work in conjunction.
The analysis of the hydropower system focuses on the controlling processes that dictate the performance of the system, sustainability, and energy performance issues.
There are many controlling processes applied in the hydropower system in ensuring that maximum energy is produced. The general outlook of the hydropower system is presented in Figure 1. The water in the channels is controlled through gates to ensure that only the required amount of water enters the power the channel which in turn rotates the turbines. Spillways along the power channels are constructed to allow overflow at specific points along the channel. The spillway has plays the role of the flow regulator. Amid floods, the intake can take water as much as twice the amount of the water it takes during the normal days (Gatte & Kadhim 2012, p.102). Thus, it is important to permit the overflow of the excess water. The gates are installed in the spillways to release the excess water. However, the emptied water is taken back to the channel with careful consideration to avoid damaging the channel.
During the rainy seasons, water is abundant, and peak production of power is achieved. However, the process changes during the dry seasons. It is during this off-peak season that pumped storage hydro power plants come into play. During the peak load periods, energy is produced from the water that falls from the higher source of water to the lower source of water. In the off-peak season, the process is reversed by pumping the water in the lower source of water (lake) to the upper lake (Blume 2016, p.38). Through this reverse process, the company can optimize the power generation. Figure 2 depicts a pumped storage hydro power plant. The controlling processes in the hydro power plants at the designing stages and operational stages follow the Thermodynamics requirements for the realization of better output. Other processes such as heat transfer, heat generation, cooling processes, and energy losses are as well taken into consideration to see that what best suits the generation of power at a particular site.
Figure 2: Typical pumped storage hydro power plant (Blume 2016, p.42).
The control processes in the hydropower plans have made useful realizations. Hydropower projects have a long life that goes beyond 50 years. For example, Darjeeling hydropower plant in India was constructed in 1897, but it is still in operation to date (Wagner & Mathur 2011, p.19). The maintenance, generation, and operation costs are lower when compared with other sources of energy such as nuclear power plants. Another important factor is that the hydropower plants have higher efficiencies going above 90% as opposed thermal energy which has efficiency up to 45% (Wagner & Mathur 2011, p.19). The storage-based hydropower projects often offer other advantages such as irrigation, flood control, recreation, and tourism among others. Also, in the controlling processes, sustainability is another issue to consider.
Sustainability and energy performance issues
Hydropower schemes in spite of the several advantages over sources of energy have possible environmental effects that are negative (Wagner & Mathur 2011, p.18). The construction of the hydropower plants, for example, transforms the environment in ways that may interfere with the ecosystem balance and results in sedimentation (Edeoja, Ibrahim, & Kucha 2015, p.23). All these challenges sustainability and performance of the system.
The sustainability of the hydropower plants is in jeopardy due to the current human activities that to some extent give little considerations to the degradation of the environment. According to Luis et al. (2013, p.2), of late, the most prominent problems experienced with the sustainability of the hydropower schemes are coping with reservoir sedimentation and loss of storage capacity. The two challenges are attributed to the uncontrolled deforestation and residential development among other human activities in the vicinity catchment areas which were once under protection. These activities result in the increment of sedimentation in the reservoirs hence threatening the energy performance and sustainability at large. Sedimentation leads to loss of the storage capacity of the reservoirs across the world (Edeoja, Ibrahim, & Kucha 2015, p. 23). The storage capacity loss in the reservoirs of the entire world is approximated as 1% (Luis et al. 2013, p.2). The sustainability problems and poor performance of hydropower schemes are attributed to multiple factors.
Another crucial factor is the effects of the global warming. Global warming results from carbon and greenhouse gases emissions which come from industrial productions and other human activities (Kaunda, Kimambo, & Nielsen 2012, p.3). Since hydropower plants depend on the hydrological cycle, the global warming due to climate change affects the schemes. In some regions, global warming will results in unreliability and unpredictability of the rainfall hence making hydropower as a source of energy undependable. On the other hand, it may accelerate the rate of flooding thus posing threats on the safety of the hydro plants because of the difficulty in controlling the flow in the dams (Edeoja, Ibrahim, & Kucha 2015, p.23). Therefore, the sustainability of the hydropower plants and its performance are in the hands of climate change and other human activities that lower the storage capacities of reservoirs as a result of sedimentation.
The major challenges facing the hydropower plants and system as a whole are the uncertain sustainability and unpredictability of the power production. The possible solutions that can help increase the predictability and sustainability of hydropower are the formation of new policies and embracing new technologies in the energy sector.
Creation of new policies
The new policies should be aimed at reducing the use of coal and other non-renewable sources of energy globally. Coal, natural gas, and other nonrenewable sources produce carbon dioxide and greenhouse gases which lead to global warming. And it is through the global warming that the climate change occurs to interfere with the productivity of the electricity in the hydropower systems. There are policies and treaties which have been put in place to encourage nations to reduce the emissions of the carbon dioxide and other greenhouse gases. For instance, the Kyoto Protocol Treaty of 1997 was signed by various countries mandating the developed countries to reduce greenhouse gases emissions as per the set standards (Kaunda, Kimambo, & Nielsen 2012, p.3). However, this treaty does not mandate the developing countries to limit the greenhouse gasses emissions, but encourages them to take part in the global warming reduction.
The new policies should thus be inclusive to take of the situation. The uncertainty of the hydropower production has probably led to low production of electricity from this source. For instance, by 2011, the United Kingdom was generating approximately 1.5% from hydropower plants (GOV.UK, 2013). This is probably due to the fear that it is uncertain based on some human activities. The friendly environment should be created for the production of energy in hydropower plants. Another policy that threatens hydropower schemes is the policy on potential small dams. Research on the energy potential of dams in the United States have shown 48,000 small dams which are lying idle; but if power is produced from all these dams, the power will be approximately 54,000 MW (Look & Alexander 2012, p.358). It is through the implementation of such policies that would enable various countries to harness hydropower from small dams in economic and sustainable means. The new policies should cover areas such as environmental conservation; this will help in reducing sedimentation which reduces the storage capacity of reservoirs. All these policies would help in reducing global warming and creating a better environment for the production of hydropower.
Embracing new technologies
Global warming and climate change are not only contributed in the line of power production but also in other sectors such as the automotive industry. The number of vehicles is increasing every year. These vehicles use fuels which emit a lot of greenhouse gases mainly carbon dioxide which in turn contributes to climate change (Mamalis, Spentzas, & Mamali 2013, p.1). And as already stated, the climate change causes unsustainability and unpredictability in the hydropower production. Adopting and embracing new technology will solve the problem. Battery-powered electric vehicles which do not produce the greenhouse effects are getting into the market in developed countries such as the United Kingdom (Sperling 2013, p.46). Governments should show commitment across the world by embracing the use of battery-powered electric vehicles.
Another technology that should be embraced is the use of solar energy and other clean energy available in the market rather than continuing to burn coal and natural gas. There is much development in the field of electricity generation through solar panels. Today, there are even sun-seeking solar panels. Therefore, light operations can be run using power from solar panels instead of using the unclean sources of energy. According to Pittock (2010, p.44), hydropower sustainablility can be realized through better management and implementation of certified and set standards. Thus, all what need to be done is embracing new technologies and creation of new policies to take of the climate change; hence realization of sustainability of hydropower.
Hydropower plants have physical processes such as thermodynamics, energy losses, heat generation, and heat transfer as well as control processes that coordinate the physical processes for the attainment of optimum power output. However, even with the control processes in place the sustainability of hydropower and its predictability of production, all seasons, are difficult to predict. Therefore, there is need to solve these problems because of the advantages of the hydropower such as the cost-effectiveness and environmental friendly. The problem of sustainability and uncertainty arise from the climate change due to global warming caused by human activities that result in greenhouse gases emission. New policies that aim at reducing global warming through environmental conservation and new technologies, for example, promoting use of electrically powered vehicle would help stabilizing hydro power production. Governments across the world and other stakeholders thus have roles to play such as enacting policies and ensuring adoption of new technology to conserve the environment for the sustenance of production of clean energy.
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