ANALYSIS OF A NEW TYPE OF MICRO-HYDRO POWER PLANT

ABSTRACT

Various types of micro-hydro power plants are used to provide the population with electricity using hydropower. These hydroelectric power plants differ from each other in design, capacity and installation area. This article analyzes various micro hydroelectric power plants. As a result of these analyses, a new type of micro-hydro power plant was analyzed. As a result of the research, the technical parameters of a new type of micro hydroelectric power plant were analyzed. Based on these parameters, a three-dimensional model of a new type of hydroelectric power plant was created.

АННОТАЦИЯ

Для обеспечения населения электроэнергией с помощью гидроэнергетики используются различные типы микроГЭС. Эти гидроэлектростанции отличаются друг от друга конструкцией, мощностью и площадью установки. В данной статье анализируются различные микроГЭС. В результате этих анализов был проанализирован новый тип микроГЭС. В результате исследований были проанализированы технические параметры микроГЭС нового типа. На основе этих параметров была создана трехмерная модель гидроэлектростанции нового типа.

Keywords: hydroelectric power plant, power of micro-hydro power plant, hydro turbine.

Ключевые слова: гидроэлектростанция,  мощность микроГЭС, гидротурбина.

Micro hydro is one of the solutions, as an important and promising power resource to meets electricity needs in rural areas, due to its ability to penetrate the limitations of transportation and technology access. In fact, micro hydro power plant (MHPP) is able to generate the power up to 100 kW [1].

The choice and installation of micro hydropower plants depends on the selected geographical area. Depending on the selected geographical area, the type of hydroelectric power plant is selected. Micro HPPs are divided into  reaction and impulse ones according to the principle of operation.

Bulb turbine: The turbine and generator are a sealed unit placed directly in the water stream.

The bulb turbine is a variation of the propeller-type turbine. In the bulb turbine arrangement, the generator is encapsulated and sealed within a streamlined watertight steel housing mounted in the center of the water passageway. The generator is driven by a variable-pitch propeller located on the downstream end of the bulb. Unlike the Kaplan turbine, water enters and exits this unit with very little change in direction. The compact nature of this design allows for more flexibility in powerhouse design. Bulb turbines can, however, be somewhat more difficult to access for service, and they require special air circulation and cooling within the bulb. [2].

Kaplan Turbine: Both the blades and the wicket gates are adjustable, allowing for a wider range of operation. The inlet guide-vanes can be opened and closed to regulate the amount of flow that can pass through the turbine. When fully closed they will stop the water completely and bring the turbine to rest.

Depending on the position of the inlet guide-vanes they introduce differing amounts of ‘swirl’ to the flow, and ensure that the water hits the rotor at the most efficient angle for the highest efficiency. The rotor blade pitch is also adjustable, from a flat profile for very low flows to a heavily-pitched profile for high flows (see Fig.1). [2].

Figure 1. Kaplan Turbine

Francis Turbine: A Francis turbine has a runner with fixed blades, usually nine or more. Water is introduced just above the runner and all around it which then falls through, causing the blades to spin. Besides the runner, the other major components include a scroll case, wicket gates, and a draft tube. Francis turbines are commonly used for medium- to high-head (130- to 2,000-foot) situations though they have been used for lower heads as well. Francis turbines work well in both horizontal and vertical orientations.

Pelton Turbine: A Pelton wheel has one or more free jets discharging water into an aerated space and impinging on the buckets of a runner. Pelton turbines are generally used for very high heads and low flows. Draft tubes are not required for an impulse turbine because the runner must be located above the maximum tailwater to permit operation at atmospheric head. he operation of a Pelton turbine is fairly simple. In this type of turbine, high speed jets of water emerge from the nozzles that surround the turbine. The high speed water jets are created by pushing high head water (such as water falling from high heads) through nozzles at atmospheric head. The maximum output is obtained from a Pelton turbine when the impulse obtained by the blades is maximum, meaning that the water stream is deflected exactly opposite to the direction at which it strikes the buckets at. As well, the  efficiency of these wheels is highest when the speed of the movement of the cups is half of the speed of the water jet, as seen in fig. 2[3].

Figure 2. Pelton Turbine

Cross-Flow Turbine: A cross-flow turbine is drum-shaped and uses an elongated, rectangular section nozzle directed against curved vanes on a cylindrically shaped runner. It resembles a "squirrel cage" blower. The cross-flow turbine allows water to flow through the blades twice. On the first pass, water flows from outside of the blades to the inside; the second pass goes from the inside back out. A guide vane at the entrance to the turbine directs the flow into a limited portion of the runner. The cross-flow turbine was developed to accommodate larger water flows and lower heads than the Pelton can handle. In this type of turbine, water enters as a flat sheet instead of a round jet - as is the case in Pelton turbines. The first impact the water has with the blades produces more power than the second hit. [3].

Their main disadvantage is that these micro-hydro power plants require high kinetic and potential energy of water to generate electricity. However, in order to obtain the kinetic and potential energy of water of great value, it is necessary to build a reservoir of a certain height h. Studies have shown that it is possible to create a structure that allows electricity to be generated from the energy of slow-flowing rivers and canals.

 As a result of research, a two-turbine two-generator micro-hydro electric power station was built. The advantage of this design is that two-way power can be obtained from a micro hydroelectric power station.

To be more precise, electricity is generated as a result of the parallel operation of generators installed in the input and output turbines of a micro hydroelectric power station The following fig.3. showқ  drawing and model of a micro HPP with a dual generator with two turbines.

Figure 3. 3D model  of a micro HPP with a dual generator with two turbines

Power of input and output turbines of Micro HPP

                                                             (1)

                                                            (2)

where: 𝜂 - efficiency of micro HPP,Q - water flow through a certain section, m³/s

H - head of water supplied to the hydraulic turbine, m

Taking into account the above formulas, the total capacity of the micro HPP is:

                                                              (3)

When determining the head, it is necessary to take into account the total (static) head and the working (dynamic) head. Total head is the vertical distance between the top of the supply pipe (water intake mark) and the point where water is released from the turbine.

The operating head is the total head minus head or hydraulic losses due to friction and turbulence in the pipeline.

These losses depend on the type, material of the pipe, diameter, length of the pipe, number of bends, etc. To determine the actual power, it is recommended to calculate the working head H.

                                                (4)

where: h_fr.los  - friction losses in the conduit; h_ad.los - additional or local losses associated with clogging of the water intake, bifurcation at constrictions and expansions, gate valves, valves, etc. The magnitude of the head loss due to friction in the conduit can be determined by the expression:

                                                                (5)

where: J - hydraulic gradient, L - conduit pipe length

The following practical formula can be used to determine the hydraulic gradient:

                                                                 (6)

where:  V - flow velocity, D - diameter of the conduit pipe, a - coefficients of the material from which the conduit is made.

Additional or local losses in the conduit pipe  are determined from the expression:

                                                           (7)

where: 𝜀_x - hydraulic resistance

References:

1. Jahidul Islam Razan, Riasat Siam Islam, Rezaul Hasan, Samiul Hasan, and Fokhrul Islam. A Comprehensive Study of Micro-Hydropower Plant and Its Potential in Bangladesh, Renewable Energy Volume 2012,10 pages.
2. Palakshappa K, Rudresha N, Vijay Kumar M, Feasibility Study on Proposed Micro Hydro Electrical Power Plant @ Kappadi (Byndoor), Karnataka, India. Proceedings of the International Conference on Industrial Engineering and Operations Management Bangkok, Thailand, March 5-7, 2019.
3. Romy Marliansyah, Dwini Normayulisa Putri, Andy Khootama, Heri Hermansyah, Optimization potential analysis of micro-hydro power plant (MHPP) from river with low head. 5th International Conference on Energy and Environment Research, ICEER 2018.
4. Md. Shad Rahman, Imtiaz Muhammed Nabil, M. Mahbubul Alam, Global Analysis of a Renewable Micro Hydro Power Generation Plant, Proceedings of the 1st International Conference on Mechanical Engineering and Applied Science (ICMEAS 2017).