Chapter 5 - Publications, US Army Corps of Engineers

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EM 1110-2-1701 31 Dec 1985 (2) For some run-of-river projects, a constant reservoir elevation can be specified, but for others, it may be necessary to develop a forebay elevation versus discharge curve. For run-of-river projects with pondage, reservoir elevation will vary from hour to hour, and the average daily elevation may vary from day to day. In the hourly modeling of peaking operations, this variation in elevation must be accounted for, and storage-elevation data must be provided in the model. However, when these proJects are being evaluated for energy ~tential, and daily, weekly, or monthly time intervals are being used, an average pool elevation should be specified. The average elevation can be estimated from hourly operation studies, and it may be specified as a single value or as varying seasonally (for example, assume a full pool in the high flow season and an average drawdown during the remainder of the year). (3) When using the flow-duration method, either a fixed (average) reservoir eleVatiOn or an elevation versus discharge relationship must be assumed for all types of projects. When using the hybrid methodg reservoir elevations are obtained for each interval from the historical record or from a base sequential streamflow routing study. (1) Three basic types of tailwater data may be provided: . a tailwater rating curve ● a weighted average or ‘block-loadedW tailwater elevation ● elevation of a downstream reservoir (2) For most run-of-river projects or projects with relatively constant daily releases, a tailwater rating curve would be used. At peaking projects, the plant may typically operate at or near full output for part of the day and at zero or some minimum output during the remainder of the day. In these cases, the tailwater elevation when generating may be virtually independent of the average streamflow, except perhaps during periods of high runoff. For projects of this type, a single tailwater elevation based on the peaking discharge is often specified. It could be a weighted average tailwater elevation, developed from hourly operation studies and weighted proportionally to the amount of generation produced in each hour of the period examined. In other cases, it might be appropriate to use a ‘block-loadedW tailwater elevation, based on an assumed typical output level (Figure 4-7). (3) There is sometimes a situation where a downstream reservoir encroaches upon the project being studied: i.e., the project being studied discharges into a downstream reservoir instead of into an open 5-30
EM 111O-2-17O1 31 Dec 1985 river reach. This encroachment may be in effect all of the time or just part of the time. During periods when encroachment occurs, the project tailwater elevation should be based on the elevation of the downstream reservoir. (4) In some cases, two or more different tailwater situations may exist at a single project during the course of the year. It may operate as a peaking project most of the year, and during this period a ‘block-loadedW tailwater elevation may be most representative. During the high flow season, the tailwater rating curve may best describe the projectts tailwater characteristics. Some energy models provide all three tailwater characteristics (rating curve, weighted average or block-loaded elevation, and elevation of downstream reservoir) and select the highest of the three fok each interval. (5) when SSR modeling is done on an hourly basis, it is necessary to reflect the dynamic variation of tailwater during peaking operations (i.e., the fact that the tailwater elevation response lags changes in discharge). A simple lag of the streamflow hydrographymay be applied to reflect the time required for tailwater to adjust to changes in discharges, or more sophisticated routing techniques may be applied, Section 4-5b provides additioml information on developing tailwater data. (1) The powerplant installed capacity establishes an upper limit on the amount of energy that can be generated in a period. Installed capacity is one of the variables considered in evaluating a hydro project, and it is common to make energy estimates for several alternative plant sizes. However, when other variables, such as dam height, storage volume, and project layout are being considered as well, a systematic approach is needed to minimize the number of power studies made. A frequently used procedure Is to assume a common plant sizing parameter for all project configurations, one which results in most of the energy being captured. This parameter could be a typical plant factor or, in the case of a duration curve analysis, a specific point on the flow-duration curve. Then, once the range of possible project configurations has been screened down to one or more most likely candidates, alternative plant sizes would be tested. (2) For preliminary studies, energy estimates are sometimes made without applying an installed capacity constraint. The resulting value, which represents the total energy potential of the site, can be used to select a range of plant sizes for more detailed study. (3) Formerly, plant capacity was specified in terms of both a rated or nameplate capacity and a somewhat higher overload capacity 5-31
Page 1 and 2: 5-1. CHAPTER 5 DETERMINING ENERGY P
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Page 5 and 6: EM 111O-2-17O1 31 Dec 1985 In this
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Page 23 and 24: ~ CASE 3: RATED AT MINIMUM HEAD I /
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Page 41 and 42: 450 400 1 * I USABLEHYDRO ENERGYIN1
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Page 45 and 46: EM 1110-2-1701 31 Dec 1985 (1) Head
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Page 51 and 52: 1500 \ \ 1400 \ \ 1300 \ \ 1200 i 1
Page 53 and 54: 1500 1400 {n\ 1 ‘\ l\ 1300 / \ I
Page 55 and 56: 1. (1) releases Compute Dependable
Page 57 and 58: 1300 , I 1200 i I I 1100 1000 300 2
Page 59 and 60: EM 1110-2-1701 31 Dec 1985 Figure 5
Page 61 and 62: kW=—= QHe (400 - 20 cfs)(31 feet)
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Page 79 and 80: TABLE 5-5 Factors for Converting Di
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Routing Worksheet EM 1110-2-1701 31
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Explanation of Data in Table 5-6 EM
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EM 1110-2-1701 31 Dec 1985 In the s
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Equation 5-16 would be revised to t
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EM 1110-2-1701 31 Dec 1985 follow a
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EM 111O-2-17O1 31 Dec 1985 the rese
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EM 1110-2-1701 31 July 1985 power (
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EM 1110-2-1701 31 July 1985 except:
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EM 111O-2-17O1 31 Dec 1985 heavily
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EM 1110-2-1701 31 Dec 1985 energy.
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1st reservoir storage above EM 1110
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EM 1110-2-1701 31 Dec 1985 (4) Figu
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EM 1110-2-1701 31 Dec 1985 maintain
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EM 1110-2-1701 31 Dec 1985 (3) Tabl
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EM 1110-2-1701 31 Dec 1985 (3) In s
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EM 1110-2-1701 31 Dec 1985 The back
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Maximize Maximize firm energy 74,00
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EM 1110-2-1701 31 Dec 1985 (2) The
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MAXIMUM POWER POOL POWER GUIDE CURV
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EM 111O-2-17O1 31 Dec 1985 . to exa
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EM 1110-2-1701 31 Dec 1985 (3) If t
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EM 111O-2-17O1 31 Dec 1985 (3) ~ It
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EM 1110-2-1701 31 Dec 1985 QHet (18
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EM 1110-2-1701 31 Dec 1985 Figure 5
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EM 1110-2-1701 31 Dec 1985 assured
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EM 1110-2-1701 31 Dec 1985 ● a hi
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i. Coordination with Other Entities
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EM 1110-2-1701 31 Dec 1985 TABLE 5-
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40, 35 .00 .00 30.00 25.00 20.00 15
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Chapter 5 - Publications, US Army Corps of Engineers

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