3.1. A general evaluation of the region’s hydroenergy resources
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Streamflow energy. Like other kinds of renewable energy, streamflow energy – or hydro energy – is a derivative of solar energy. Of all the irradiance received by Earth from the Sun (173,000 TW), almost a quarter – 40,000 TW – is that part which is evaporated [19]. Only a very small fraction of this capacity (about 0.1%) can be used to man’s advantage: It is this part of the transformed solar-to-vapor energy that falls as precipitation on the Earth’s surface. Under natural conditions, or without interference from man, this water energy is spent on soil erosion, degradation of land relief, transfer of products of soil erosion, and on overcoming the various forces that resist water flow in rivers.
Unlike most other kinds of renewable energy, hydroenergy technologies, which make use of the energy of streamflow, are highly developed and widely employed at the present time. Hydro energy resources are capable of supplying the energy market with guaranteed capacities of energy available at competitive prices or, at times, even cheaper, like hydroelectric power installations in Russia’s Siberia or the major hydropower plants in China or Brazil. Hydroenergy covers approximately 20% of the global energy demand and is the main power source in more than 30 of the world’s countries. In the almost two thousand years of its development, hydro power has achieved considerable levels of energy efficiency, advancing from the wooden water wheel with a performance efficiency rate of 10% to the high-speed hydroturbine with efficiency rates reaching 95%.
Hydropower resources: General notions. The force that drives streamflow forward is the weight of the water. The power of streamflow is determined by the scope of its downward movement, i.e. by the difference between water levels at the origin of the stretch surveyed and at its end, as well as the values for the streaming water’s weight. If the fall of the stream on a river stretch equaling L meters is H meters, then, with flow rate Q, in m3/s, equaling its average value at the stretch’s beginning and end, the work performed by the streaming water (waterflow power) in one second N, in watts or J/s, on the stretch observed will equal:
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where ρ is water mass density, in kg/m3, and g is free fall acceleration, in m/s2.
Watershed energy E , in kilowatt-hours, is determined by the product of streamflow intensity N by time t , in seconds, and is:
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where W=Qt is the volume of the waterflow used, in m3.
The correlation described above determines potential, or theoretical complete, hydroenergy resources. When assessing potential water energy resources, consideration is not given to loss of streamflow, water head and water energy as the latter is converted from mechanical to electric power.
Before an evaluation of the potential streamflow resources of a river is performed, a so-called water resource cadastre has to be compiled, which will include a general description of the river and its basin, available hydrometric, hydrological, topographic and geological engineering data, etc. All of these records are summarized in a cadastral chart containing the river’s thalweg, a graph representing the accrual of catchment area from the river’s headstream to its estuary, a graph of average flow rate across a number of years, and unit power values for each river stretch (in kW/km). Power values for individual river stretches are then summed up and its overall power capacity and annual energy output can be calculated, with the capacity and output contingent on the watershed preserving the levels determined at original measurement. This method helps assess the potential overall hydro energy resources available in rivers and river basins of various regions or a whole country.
The particular quantity of hydro energy resources that can be used by hydroelectric power plants for the generation of electric power is called “technical resources.” The technical potential is always smaller than the entire theoretical potential because, for various reasons, not all river stretches can be used for the construction of hydroelectric power plants. Especially in densely populated areas, considerable volumes of water are also collected from many rivers to cover needs other than producing energy. Water stored in water reservoirs built on the sites of hydroelectric power plants is subject to evaporation and filtering, which leads to loss of water volumes. Furthermore, certain loss of water pressure takes place at hydroelectric power plants due to the resistance to the streamflow formed by the water conduits or by the backwater below the hydroelectric dams.
The USSR, with the prolonged stability of the country’s financial situation and the unchanging rate of the ruble, was afforded another durable notion: economic hydroenergy resources. Those were assumed to be such resources whose application was economically expedient. The method of comparative economic efficiency in use in Soviet energy economy was based on comparison of hydroelectric power plants under development with conventional thermal electric power plants, while the projected energy effect remained at known levels. Another method applied was the notion of absolute energy efficiency, where payoff period for a new hydroelectric power plant was not to exceed eight years and 44 days.
In today’s Russia, no evaluation studies for economic hydro energy resources are performed due to speedy and significant fluctuations in prices for construction materials and fuels. When the need arises for the construction of a power complex site, including a hydroelectric power plant, decision-making regarding the economic feasibility of the project depends on the calculations of its economic efficiency. The ground rule dictates that revenues received from the implementation of the project in question will exceed the revenues the same amount of money would accrue if it were saved in a bank.
Types of hydroelectric power plants. The capacities – and, correspondingly, the output and dimensions – of the modern hydroelectric power installations vary by hundreds of thousands of times, ranging from a few hundred watts to some 12,000 MW. These power plants can be classified by various characteristics and fall into different category types, depending on the levels of water head, power capacity, type of turbines installed, location of the hydroelectric dam and layout of the structures. These breakdowns, of course, are not absolutely independent, which can be seen in figures [3.1] and [3.2]. Therefore, a specification based on one principle will ultimately provide the description of the hydropower plant as a whole. For instance, an increased water head, with flow rate remaining the same, results in a linear increase in the hydropower plant’s capacity; its output will grow as well, but will be limited by the levels of the river’s stream flow.
If water head is increased from between two and five meters to between 10 and 15 meters, the hydropower plant will change classification from streamflow power plant (Fig. 3.1 a,b) to water reservoir power plant (Fig. 3.2). Accordingly, the type of the hydraulic turbine will change from horizontal downstream to vertical propeller or vertical runner-blade, like Kaplan turbine (Fig. 3.3). With water head exceeding 15 to 20 meters, turbine type changes to radial-axial (Francis turbine, Fig 3.4). Further increase in water head leads to hydropower plant changing its type to diversion power plant (Fig. 3.5). Furthermore, if water head exceeds 100 meters, turbine type may change to free-jet double-bucket (Pelton) turbine (Fig. 3.6). Fig. 3.7 is a chart showing the possible areas of application of different types of hydraulic turbines in accordance with the water head, rate of flow through the turbine and its power capacity. It should be noted, however, that considerations of costs and simpler maintenance and production routines may influence hydropower plant developers to make their choice of turbine type in contradiction to the chart presented in Fig. 3.7. The following rule of thumb applies for changes in dimensions of the main energy installations of a hydroelectric power plant: The higher the rate of flow through the power plant, the larger the scale of the hydraulic installations, including the size of the turbines themselves; and the higher the water pressure, the smaller the size of the main installations of the power plant and its turbines, provided the rate of flow remains the same.
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Fig. 3.1a. Run-of-river hydropower plant with a vertical turbine.
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Fig. 3.1b. Run-of-river hydropower plant with a bulb turbine
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Fig. 3.2. The principal layout of a reservoir-type hydropower plant.
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Fig. 3.3. Propeller hydroturbine and Kaplan (runner-blade) turbine
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Fig. 3.4. Radial-axial turbine.
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Fig. 3.5. General layout of a diversion-type hydropower plant.
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Fig. 3.6. Double-bucket (Pelton) turbine.
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Fig.3.7 Diagram for the determination of hydraulic turbine performance parameters based on different types of turbines
In addition to distinguishing hydraulic turbines by the types mentioned above, variations can also be found in their main principle of function. Several types of hydraulic turbines listed above are classified as “reaction turbines”, while the turbine based on Pelton buckets is an impulse turbine. Without delving into complicated mathematical descriptions, it is sufficient to say that reaction turbines are turbines which use both the impulse force of the head pressure of the water hitting the turbine blades and the reactive force of the outgoing water as it leaves the turbine’s blades going in the opposite direction. Impulse turbines use only the incoming water’s impulsive force applied against the turbine’s blades.
Hydroenergy resources of the Murmansk region. Complete potential hydroenergy resources of the rivers of the Murmansk region, based on a multi-year average annual output, are estimated at 19.3 TWh [20]. Taking economic reasons into consideration, only about a third of these resources could actually be put to use. This is roughly the level of hydroenergy resources development that the Murmansk region has achieved today. Seventeen hydroenergy power plants in operation in the Kola Energy System have a combined output of around 6 TWh in one average-flow year.
A brief time line of water energy development of the Kola Peninsula. The Kola Energy System was created in 1934 after a high-voltage power line connected the peninsula’s first two hydropower plants, the Niva-2 and the Lower Tuloma Hydroelectric Power Plant. Due to the lack of deposits of organic fuel resources on the peninsula’s territory, the development of the region’s energy economy had to rely heavily on the construction of hydroelectric power plants at the easily accessible and effective streams of the area’s large and medium-size rivers.
The annual growth rate for the installed energy capacity for that period was 50 MW (except in the wartime years, between 1941 and 1945) and was achieved primarily by means of the hydroelectric power plants. The share of thermal electric power plants during that time did not exceed 10%.
Between 1959 and 1973, the growing demand for energy and the impossibility of satisfying it solely using hydroelectric power plants led to the decision to build the Kirovsk State District Power Plant (now, Apatity Combined Heat and Power Plant). As the site reached it design capacity of 500 MW, the share of thermal power plants in the region’s energy system increased to 36%. At the same time, several hydropower plants were also undergoing development. Growth rate for the installed capacity of the region’s energy system was in that period around 100 MW per year, shared roughly half and half by the state district power plant and the hydroelectric sites.
In 1973, the first reactor block of the Kola Nuclear Power Plant went online with an operational capacity of 440 MW, and within a few years’ time, the plant reached its full design capacity of 1,760 MW. Thermal plants increased their share in the capacity balance of the peninsula’s energy system to 59%, and their contribution to the region’s combined energy output to 70%. Those years also saw the construction and development of the cascaded hydropower plants on the Teriberka River. This was the last power plant cascade built on the region’s territory in the 20th century. Installed capacity growth rate for the period of 1973 to 1984 was around 200 MW per year (accounted for, mostly, by nuclear power plants). The year 1990 was a record year for energy consumption in the Murmansk region: With the annual energy output of 19.6 TWh and a 2.9 TWh delivered to the neighboring republic of Karelia, energy demand in the Murmansk region reached its highest peak of 16.6 TWh. Since 1984, the energy system capacity for the region has remained practically unchanged.
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