Loctaion Selection for hydropower (1).pptx

hydropower plants

1. Location Selection for Hydropower

2. Contents Hydropower Location Selection Section.1 Scientific Methods Method of measuring water debit. Rain Probability Method. Section.2 Watersheds. Section.3 Mainstay Debit. 2

3. Scientific Methods Scientific method is the step taken to obtain scientific results by carrying out basic steps i.e. Hypothesis, Qualitative or Quantitative Analysis, Prediction and Verification. The scientific methods for measuring water debit are as follows: 3

4. Water Debit Available flow is of utmost importance for site selection. The study of any potential hydroelectric scheme must first of all address the availability of an adequate water supply. The amount of water and its annual distribution affects hydropower project viability. The hydropower project energy output depends on annual flow distribution, hence hydropower project without a reservoir can produce energy only from available water and cannot compensate during dry periods. Hydropower project with a reservoir can compensate during dry periods by using water stored during wet periods and is able to produce energy during peak demand. When selecting a site and estimating energy generation, it is crucial to consider hydrological flow and other factors that may reduce flow available for energy generation, including minimum flow leakage, and evaporation. (Malovic, Engelmann Pilger et al. 2015) 4

5. Water Debit Therefore to estimate the water potential one needs to know the variation of the discharge throughout the year. In the best circumstances the hydrologic authorities would have installed a gauging station, in the stretch of stream under consideration, and streamflow time series data would have been gathered regularly over several years. For an ungauged watercourse, where observations of discharge over a long period are not available involves the science of hydrology and will suffice to make use of one of the several approaches, explained later, to estimate the long term average annual flow and the flow duration Curve. ( Penche 1998) 5

6. Measuring Water Debit for Gauged Stations Hydrological or Hydrometeorological Services or related agencies have been established in countries for systematic water resources data collection, archiving and dissemination. Their primary role is to provide information to decision makers on the status of water resources and trends in water resources. Conventional water resources information comprises the statistics of a variety of meteorological and hydrological elements. The elements include the following: (WMO 2008) Precipitation River levels and flows Lake and reservoir levels Groundwater levels Evapotranspiration Sediment concentrations and loads in rivers Water quality of surface water and groundwater 6

7. Measuring Water Debit for Un-Gauged Stations 7 Often small streams suitable for micro hydropower projects are not gauged. Therefore, river flow data are not usually available. So, direct spot measurement of the river flows become essential to estimate what the low flows are and how the river flows vary throughout the year. In the absence of flow records, a minimum of one flow measurement per month for at least one year should be performed close to the proposed intake area so that the installed capacity can be finalized and the energy generation can be reliably estimated. Various flow measurement methods pertinent to micro hydropower projects are described herein. (Pandey and Karki 2016)

8. Conductivity Meter A conductivity meter measures the amount of electrical current or conductance in a solution. The meter is equipped with a probe, usually handheld, for field or on-site measurements. After the probe is placed in the liquid to be measured, the meter applies voltage between two electrodes inside the probe. Electrical resistance from the solution causes a drop in voltage, which is read by the meter. The meter converts this reading to milli or micro-Siemens ( mS or μS ) per centimeter. This value indicates the total dissolved solids. Flow measurement using conductivity meter is also known as the salt dilution method. This method involves pouring a salt solution some distance upstream and measuring the change in conductivity as the salt wave approaches the gauging location (where the probe is placed). The salt solution changes the conductivity of the river (as the salt wave travels downstream), and this change in conductivity can be related to the river flow if baseline conductivity of the river, the type and amount of salt added, and the water temperature are known. (Pandey and Karki 2016) 8

9. Conductivity Meter As the salt wave passes the measurement location, the conductivity of the river returns to its original level (i.e., baseline conductivity). Conductivity meters can be used in small, highly turbulent streams with rough, irregular channels and for flow measurements of a river. Table salt (sodium chloride, NaCl ) is the most commonly used salt because it is inexpensive and widely available. Stream flow is determined by using the following formula Q = M · k/A Area can be calculated from the following formula: A = (ΣC(t) − N · C0) · T where ΣC(t) = sum of conductivity values ( μS ), N = number of observations, C0 = base conductivity ( μS ), and T = time interval (seconds). Salt constant K is found by using following equation: K = k/(1 + αΔ T) where K = salt constant at temperature T, k = salt constant at temperature t, α = temperature compensation slope for salt and ΔT = Temperature Change The advantages of this method are that it is simple and fairly accurate. It is also reliable for a wide range of flows and measurements can generally be taken within 30 minutes. This method can be used in fast-flowing rivers ranging from 25 l/s to about 2.5 m3/s. (Pandey and Karki 2016) 9

10. Current Meter A current meter is the most commonly used instrument to measure the velocity at a point in the flow cross-section. A current meter is a mechanical device with revolving cups or a propeller attached to a shaft. These cups or propellers revolve when the instrument is immersed in flowing water because of flow velocity. The revolving frequency is dependent on flow velocity i.e. the higher the flow velocity, the faster the revolution. With the correlation between the revolutions of the cups or propeller, the flow velocity can be determined. During flow measurement using a current meter, the river section is divided into a number of strips (trapezoidal and triangular), and velocity corresponding to each strip is determined by using a current meter. Area of the segment can be found by multiplying segment width w, and segment depth d. (Pandey and Karki 2016) 10

11. Current Meter Then the flow through the hatched segment is: Q = w * d * v Thus, calculating the flow of each segment and adding all flows will result in total river. flow at the time of measurement. At least three sets of measurements should be taken during flow measurement to avoid error. The current meter is a suitable method of flow measurement for rivers with relatively higher flows. The current meter is most suitable for flow measurement in the velocity range between 0.2 m/s and 5 m/s where the accuracy can be as high as 98%. (Pandey and Karki 2016) 11

12. Float Method Float measurement is a simple method to measure flows in small rivers. In this method, any object that floats in water is released at the surface of the river, and its velocity is estimated by recording the time required for it to travel a certain distance. Thus, the surface flow velocity can be obtained by dividing the length of the river stretch that the floating object has traveled by the time taken. This value should be multiplied by following the correction factor to obtain the mean flow velocity of the river at the measurement location. And the discharge can be calculated by using the following equation: Q = A*k*V where Q = discharge of the river in m3/s, A = cross-section area of the stretch (m2; computation of cross-section was discussed earlier), V = float velocity or velocity of the floating object (m/s), and k = coefficient to correct the surface velocity .(Pandey and Karki 2016) 12

13. Representation of Discharge Data So, the table of stream discharges over a period of years at a particular site , which to be of any use has to be organised into a usable form. This can be done mainly by using two following methods: ( Penche 1998) Hydrograph Flow Duration Curve 13

14. Precipitation The precipitation is mainly in the form of rainfall. Though there is appreciable snowfall at high altitudes in the mountain range and most of the water comes through the snow-melt in summer. The total rainfall received in a given period at a location is highly variable from one year to another. The variability depends on the type of climate and the length of the considered period. Because of the strong variability of rainfall in time, the design and management of irrigation water supply and flood control systems are not based on the long-term average of rainfall records. ( Raghunath 2006) 14

15. Measurement of Precipitation Rainfall may be measured by a network of rain gauges which may either be of non-recording or recording type. The non-recording rain gauge mostly used is the Symon’s rain gauge . It consists of a funnel with a circular rim and a glass bottle as a receiver. The cylindrical metal casing is fixed vertically to the masonry foundation with the level rim. The rain falling into the funnel is collected in the receiver and is measured in a special measuring glass graduated in mm of rainfall. The rainfall is measured once in a day while during heavy rains, it must be measured three or four times in the day. The non-recording or the Symon’s rain gauge gives only the total depth of rainfall for the previous 24 hours ( i.e., daily rainfall) and does not give the intensity and duration of rainfall during different time intervals of the day. ( Raghunath 2006) 15

16. Self/Automatic Recording Rain Gauge This type of rain gauge has an automatic mechanical arrangement consisting of a clockwork, a drum with a graph paper fixed around it and a pencil point, which draws the mass curve of rainfall. From this mass curve, the depth of rainfall in a given time, the rate or intensity of rainfall at any instant can be determined. The self-recording rain gauge is generally used in conjunction with an ordinary rain gauge exposed close by, for use as standard, by means of which the readings of the recording rain gauge can be checked and if necessary adjusted. ( Raghunath 2006) There are three types of recording rain gauges as described below: Tipping bucket gauge Weighing gauge Float gauge 16

17. Tipping Bucket Rain Gauge This consists of a cylindrical receiver with a funnel inside. Just below the funnel a pair of tipping buckets is pivoted such that when one of the bucket receives a rainfall of 0.25 mm it tips and empties into a tank below, while the other bucket takes its position and the process is repeated. The tipping of the bucket actuates on electric circuit which causes a pen to move on a chart wrapped round a drum which revolves by a clock mechanism. This type cannot record snow. ( Raghunath 2006) 17

18. Weighing Rain Gauge In this type of rain-gauge, when a certain weight of rainfall is collected in a tank, which rests on a spring lever balance, it makes a pen to move on a chart wrapped round a clock driven drum. The rotation of the drum sets the time scale while the vertical motion of the pen records the cumulative precipitation. ( Raghunath 2006) 18

19. Float Rain Gauge In this type, as the rain is collected in a float chamber, the float moves up which makes a pen to move on a chart wrapped round a clock driven drum. When the float chamber fills up, the water syphons out automatically through a syphon tube kept in an interconnected syphon chamber. The clockwork revolves the drum once in 24 hours. This type of gauge is mainly used by Meteorological department. ( Raghunath 2006) 19

20. Representation of the Rainfall data So, the rainfall data over a period of time at a particular site , which to be of any use has to be organised into a usable form. This can be done mainly by using two following methods: ( Penche 1998) Hyetograph Mass-Curve 20

21. Watersheds It’s a land area that channels rainfall and snowmelt to creeks, streams, and rivers, and eventually to  outflow points  such as reservoirs, bays, and the ocean. Watershed is an area of land where water naturally drains to a one point Rainfall, snowmelt and other precipitation flows into Lakes, rivers , ocean and pond etc. Watershed boundaries are natural and have constructive features that directly flows water. It is normal for watersheds to cross state, boundaries and countries. 21

22. Importance of Watersheds It is important for watersheds to clean because this water is used for many purpose like drinking water. Wild Life also depends on watersheds for food ,water and shelter. Aquatic animal also depends on watersheds. 22

23. Factors harming Watersheds Non Point source Pollution is the largest cause of water pollution and biggest threat to the health of watersheds. Non Point source Pollution start with rainfall or Snowmelt moving over and through the ground. As water moves it kills natural and human made Pollutants from different places like road, parks and construction sites. Eventually water follows into lakes and rivers carrying these pollutant harming underground water also. 23

24. Objectives of Watershed Management To manage and utilize the runoff water for useful purpose. To Protect , conserve and improve the land of watershed for more efficient and sustained production. To check soil erosion and to reduce the effect of sediment yield on the watershed. 24

25. Mainstay Debit Hydrological planning is always associated with the characteristics of the watershed. Rainfall and watershed characteristics greatly affect the flow conditions. The fact of getting river flow data in many watershed areas is often incomplete. The availability of long-term river flow data at the site of the taking building is necessary for planning purposes of MHP. This is because the water building function depends heavily on water requirements throughout the season, so to get continuity of water supply according to the calculation planning required for reliable debit. The expected release of the mainstay debit is always available throughout the year with the risk of failure being calculated as small as possible. Mainstay debit data is generally required for hydro-power plant development planning, namely to determine the calculation of water supply in building intake (intake). 25

26. References Malovic , D., et al. (2015). Hydroelectric power: a guide for developers and investors, The World Bank. Penche , C. (1998). Layman's guidebook on how to develop a small hydro site, DG XVII, European Commission. WMO (2008). Guide to Hydrological Practices. Volume I. Hydrology–From Measurement to Hydrological Information, World Meteorological Organization (WMO) Geneva. Pandey, B. and A. Karki (2016). Hydroelectric Energy: Renewable Energy and the Environment, CRC Press. Raghunath , H. M. (2006). Hydrology: principles, analysis and design, New Age International. US Geological Survey, Water Resources of Pennsylvania SRBC Streamflow Information. Kunwor , A., Technical Specifications of Micro Hydropower System Design and its Implementation. 2012. 26

27. Thank You 27