Paper No: 5 Water Resources and Management Module: 21 Hydropower Generation-I Development Team Principal Investigator Prof. R.K. Kohli & Prof. V. K. Garg & Prof. Ashok Dhawan Co- Principal Investigator Central University of Punjab, Bathinda Dr Hardeep Rai Sharma, IES Paper Coordinator Kurukshetra University, Kurukshetra Prof. Rajesh Kumar Lohchab, Guru Jambheshwar Content Writer University of Science and Technology, Hisar Content Reviewer Prof. ( Retd.) V. Subramanian, SES , Jawaharlal Nehru University, New Delhi Anchor Institute Central University of Punjab 1 Water Resources and Management Environmental Sciences Hydropower Generation-I Description of Module Subject Name Environmental Sciences Paper Name Water Resources and Management Module Hydropower Generation -I Name/Title Module Id EVS/WRM-V/21 Pre-requisites Objectives To understand the concept and components of Hydropower generation Keywords Hydropower, Rivers, Dams, Turbines, Power house, 2 Water Resources and Management Environmental Sciences Hydropower Generation-I Learning Objectives 1. To understand the history and basics of hydropower 2. To understand the role of solar power through water cycle in generation of hydropower 3. To explain the components of Hydroelectric Power Plant 4. To explain the advantages and disadvantages of Hydroelectric Power Plant Introduction Based on resources, power generation can be classified as coal and gas based thermal power plants (TPP), hydro power plants (HPP), nuclear power plants (NPP) and renewable energy based power generation plants. Power generation in India is unevenly distributed because hydro resources are available in Himalayan region, while fossil fuel resources are available in the central and western parts. For optimization of these resources, the power systems in our country were categorized into five power regions in the 1960s (Ramanathan and Abeygunawardena, 2007). That’s why regional power grids were developed. Later on in the 1980s a national grid was formed which strengthened the intraregional and inter-regional transmission systems. The Indian power system is also connected with the Bhutan and Nepal power systems. Hydro Energy Hydro power stations use the potential energy of water when it falls due to gravity. The fall and movement of water is part of water cycle. The force of moving water can be extremely powerful. Hydropower is a renewable source of energy. It is one of the cheapest sources of energy. Electricity production by hydropower is cheap because once a dam is built water is available free of cost. History of Hydropower From centuries hydropower has been used as source of energy. Greeks were using hydropower to produce flour from wheat 2,000 years ago. The force of falling water has been used to generate 3 Water Resources and Management Environmental Sciences Hydropower Generation-I electricity since late 19th century and first hydroelectric power plant was built on the Fox River in 1882. Hydropower Resource Potential of India India is ranks fifth in terms of hydropower potential in the world. It is mainly spread on six major river systems. The Ganga, Indus and Brahmaputra account for about 80% of the total potential of Indian hydropower (Ramanathan and Abeygunawardena, 2007). Rationale for hydropower Hydropower is an established technology with cost effective renewable source of energy. Other benefits of hydropower plants are: Water supply Flood and drought control, and irrigation Navigation and recreational activities Electricity production without interruptions Safe operation with minimum risks Environmental and socially sustainable Large energy storage and operation flexibility for balancing the seasonal load How Hydropower Works? Hydroelectric power is a form of solar energy. The hydrological cycle is a sun driven process of water transport from the oceans to the atmosphere and from the atmosphere back to the earth surface and oceans. The hydrological cycle discoverer, Bernard Palissy (1580 CE), declare that rainfall itself is adequate for the maintenance of rivers. It explains the nonstop movement of water on, above and below the earth surface. The water travels from one source to another i.e. from river to ocean, or from 4 Water Resources and Management Environmental Sciences Hydropower Generation-I the ocean to the atmosphere and back by evaporation, condensation, precipitation, infiltration, surface runoff and subsurface flow. During this it undergoes through liquid, solid (ice) and vapor (gas) phase. This cycle extend from an average depth of about one km in the lithosphere (the crust of the earth), to a height of about 15 km in the atmosphere. The water cycle maintain of life and ecosystems on the earth and used for households, industries, agriculture and production of power. Water Reservoirs A reservoir is an artificial lake constructing by making a dams across rivers to store water. It can also be formed on natural lake by constructing a dam at Lake outlet. They are used for power generation, downstream water supply, irrigation, flood control, canals and recreation. Reservoirs are highly managed structure used to balance the flow by taking in water during high flows and releasing it during low flows in controlled manner. Recreational uses of reservoir are fishing, boating bird watching, landscape painting, walking and hiking. Large reservoirs retain water for months or even years of average inflows basis and also provide flood protection and irrigation services. The design and provision of these services in a hydropower plant dependents on environment and social needs. Catchment Area and Watershed Catchment area is the area of land from which water is drain into river. It is also known as river basin, catchment basin, drainage basin, drainage area and watershed. It acts like a funnel and all water from this is channeled to a single point into a river. Catchment areas are topographically separated from each other by a ridge, hill or mountain and line which divide watershed or surface runoff between two adjacent river basins is called the topographic water divide, or the watershed divide or simply the divide. A network of rain gauges is placed to assess of water resources of a catchment. For each rain gauge catchment area should be small for accuracy and better results. Rain gauge density is expressed as area covered per gauge. According to IS: 4987-1968 the density of rain gauge network is one station per 520 km2 in plains, one in 260 to 390km2 in moderately elevated area i.e. up to 1000m and one in 130 km2 hilly area. 5 Water Resources and Management Environmental Sciences Hydropower Generation-I Hydrograph It is a graphical representation of discharge variation with time thus it is the representation of rainfall input of a catchment. The discharge recorded in hydrograph is the combined result of surface runoff, interflow and base flow. Direct and indirect methods of flow measurements are used to calculate the discharge of a stream. Direct measurement of discharge in a stream is carried out velocity method, dilution techniques, moving boat method etc. whereas indirect measurement of discharge is done by using hydraulic structures like weirs and gated structures and slope area method. Unit Hydrograph When one cm of rainfall is applied at a uniform rate at a specified time period over the catchment area uniformly is referred as unit hydrograph. Unit hydrograph are used to predict the flood in a catchment by a storm. Effective Rainfall Hydrograph Effective rainfall hydrograph (ERH) is the subtraction of initial losses and infiltration losses from the rainfall hydrograph. It causes direct runoff which includes both surface runoff and interflow. Effective rainfall is slightly higher than the excess rainfall. Hydropower Theory The dam holds the water to create the height difference necessary to maintain potential energy. Water flow continues to the river downstream of the dam. The two vital factors necessary for hydropower generations are the flow and the head of the stream or river. The flow is the volume of water which can be captured and re-directed to turn the turbine generator, and the head is the distance of water fall on its way to the generator. The larger the flow more will be the water, and higher the head higher will be the distance the water falls, thus the more energy is available for conversion to electricity. Double the flow and double will be the power, and double the head, double will be the power again. A low head site i.e. head of ≤10 meters, you need to have a good volume of water flow to generate electricity. A high head site i.e. head of ≥20 meters gravity will give you an energy boost. 6 Water Resources and Management Environmental Sciences Hydropower Generation-I Kinetic energy of falling water is harnessed to provide electrical power. It depends on flow and height of the falling water. Hydroelectric Power is a Function of Height and Volume. Power = Head x Flow x Gravity The theoretical power from a site is calculated by equation given below (Gaiusobaseki, 2010): P = ηρQgh Where:- P = Power (W) η = Dimensionless efficiency of the turbine (Approx 0.9) ρ = Density of Water (1000 kg/m3) Q = Volumetric flow rate (m2/s) G = Acceleration due to gravity (9.8m/s2) h = Height difference between inlet and outlet (m) Energy from Hydro-power The potential theoretical energy in a volume of elevated water can be calculated by: W = ρ V g h Where: W = energy (J) V = volume of water (m3) 7 Water Resources and Management Environmental Sciences Hydropower Generation-I The Physics of Hydropower: Based on the conservation of energy, hydropower energy transfer is as below: Potential Energy → Kinetic Energy → Mechanical Energy → Electric Energy Potential Energy: Head level is the difference between the maximum heights of water to the minimum height of the water. It is directly proportional to the potential energy. A high head level would mean that the potential energy of the hydropower system is very high. The effective head is the difference between the energy head at the entrance to the turbine and the energy head at the exit of the draft tube.