pubudu's small hydro ass

SMALL HYDRO PLANT DESING

Written by,

V.P.R. Ariyadasa09/8651

Coordinated by,

Prof. Udayanga Hemapala

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Contents

Page

1.0 Design details of a Mini Hydro Plant …………………………………………… 3

1.1 Location ………………………………………………………………… 3

1.2 Catchment area …………………………………………………………. 4

1.3 Rated flow design ………………………………………………………. 5

1.4 Selection of turbine …………………………………………………….. 6

1.4.1 Turbine efficiencies for part loads……………………………. 7

1.5 Summary of parameters……………………………………………….…. 7

1.6 Design of channel ……………………………….. ……………………… 8

1.7 Spill ways…………………………………… …………………………… 8

1.8 Design parameters for de-silting basin …………………………………… 9

1.9 Design of Weir & Intake …………………………………………………. 9

1.10 Design of Penstock ……………………………………………………… 9

2.0 Project Evaluation …………………………………………………………………. 10

Annexture 1 – Average rainfall data of Allakolla & Gomara

Annexture 2 – Flow duration curve design

Annexture 3 – Penstock Calculation

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1.0 Design details of a Mini Hydro plant

1.1 Location

The location of our project proposal is in kota ganga (river) in between ronmadaketiya and katawalamulla , galkotuwa GM divisional area.

Image 1 – Image taken from 1:50,000 map of selected locations

To access the site first need to take A26 Digana - Mahiyangana road. Then need to take left turn form the Karaliyedda Junction which leads to Ronmadaketiya three way junction. While taking right turn from Ronmadaketiya junction (0.9 Km travel)can reach to weir and form the left turn can reach to Power house (1.3 Km) at Ketawalamulla.

Weir location is 800 45’40”E & 70 22’N on 600m contour.

Power house location selected as 70 22’ 30”N & 800 45’E

The Google earth satellite image of selected locations is as follows. (The river flow, Plant & Weir locations and access path are drawn in the image layout)

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Image 2 – Image taken from Google Earth of selected locations

1.2 Catchment Area.

Demarcated catchment area is about 15.75 km2 and spread around Kaladuriya, Allakolla, Gomara, Randiwela, Katooloya areas.

Image 3: Demarcated catchments area

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With available rain fall data in Gomara and Allakolla the following design parameters were derived. (The entire data sheets are annexed as Annexed No:01)

Runoff for particular area Gomara and Allakolla was obtained typical rainfall runoff graph.

Rain fall

(mm)

Run-Off

(mm)

Run-off %

Area (km2)

Area %

year Avg

(mm)

year Max

(mm)

year Min

(mm)

Gomara 3,076

1,750 56.90% 6.7575 43%

8.27

39.71 0.00

Allakolla 2,979

1,700 57.07% 8.9925 57%

8.01

33.45 0.00

Catchment 3,020

1,721 57.00% 15.750 100%

Table 1: Summary table of annual rainfall data

As per the 1:50 000 geographical survey maps the approximate cannel and the penstock are selected as follows

Cannel Length 2.05 km running on 600 m contour curve. Penstock Length 300 m from 600 m contour curve to 500 m contour curve.

1.3 Rated Flow Design

The flow duration curve for the proposed project is plotted by using the annual rainfall data (annexed as Annexed No: 02) and rated flow is selected with the 15 % exceedance.

1.4 Selection of the turbine

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The selection of turbine is done by using the designed head (100 m) and the designed flow (1.3 m3)

Graph 1: Turbine selection graph

As per the turbine selection graph Francis Turbine is selected.

1.4.1 Turbine Efficiencies for Part Loads.

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Graph 2: Turbine efficiencies graph

Part load efficiencies are calculated based on the above graph.

1.5 Summery of Parameters.

No Parameter Value/Selection1 Net Head 104m2 Eff. Generator 96%3 Eff. Transformer 99%4 Designed Exceedance 0.07

5 Rated Flow 1.400 m3/s

6 Minimum Flow to be left 0.05 m3/s7 Annual Energy 5.33 MWh8 Plant Capacity 1 MW9 Turbine Type Francis

Table 2: Summary of the parameters

1.6 Design of Channel

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Length of the channel (L) = 2.05 KmDesign discharge of the channel (Q) = 1.4 m3/sAssumed velocity (V) = 1.5 ms-1

Cross sectional area of the channel (A) = Q/V = 1.4/1.5 = 0.93 m2

Cross sectional dimensions of the channel

Assume cannel profile as rectangular.

Hydraulic radius =0.35√A =0.337 mDepth =2r =0.675 m Width =4r =1.35 m

Channel bed slope (S) = {nv/R2/3}2Roughness coefficient (n) = 0.01 (For neat Concrete)

Velocity (V) = 1.5 m/s

S = [0.01 x 1.5/0.3372/3]2 = 0.00096 m

So, Head loss = Channel bed slope x Length of the cannel = 0.00096 x 2050 = 1.9668 m.

Required concrete volume:Assuming 0.3m free board (FB),= [(0.015 x0.95 x2) + (0.015 x1.3) ] x 2050

= 98.4 m 3

Image 4: Channel Design

1.7 Spill ways

Spill way span = FB/Slope = 300.0m

It is proposed to have evenly distributed six spill ways throughout the cannel length of 2, 050m.

1.8 Design parameters for De-silting Basing

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0.015 m0.95 m

1.3 m

0.015 m2050 m

Setting Speed of particles Vo = 5m/min; Assuming 0.8 mm pariclesCanel depth d = 0.65 mDesigned flow velocity = 0.3 ms-1 Length of basin L > DV/Vo = 2.34 m

Flow rate of 0.3 ms- 1 and Design flow of 1.3 m3 ,Width of the Basin = Q/VD = 3.7m; assuming basin pit of 0.5m

1.9 Design of Weir and Intake The location and the nature of the of the intake is to be properly selected with care consideration on following decisive factors and practical circumstances in the site.

Stream bed should be permanent as to avoid possible erosionShould be placed in a relative straight and narrow section of the stream and should avoid any bends along the streamIntake should not be oriented towards upstream to avoid possible damages due to debris and boulders carrying in during floodsBe placed so as to get the possible protection from existing boulders, if any.Weir is to be supported with timber padding to avoid damages due to debris and boulders in the upstream.Trash rack is necessarily to be placed at the intake to trap unnecessary debris entering into to the cannel.A provision to be allowed fro the minimum flow of 0.05m3 in the stream.

1.10 Design of Penstock

The length of the penstock is 300m & let assume the number of expansion joints to be 2. The relevant parameters of penstock are annexed as Annex no.2.

Image 5: A penstock

2.0 Project Evaluation

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Project Cost Calculation

Event Estimated Cost (Rs.)1. 33kV Distribution line (For 10 km) Mn. 21Substation and metering Mn. 3Electro mechanical Units in Power House Mn. 40Import and Supply of Penstock Mn. 8Penstock Path (Anchor Supports and Penstock Handling) Mn. 8Concrete Channel and Forbay Tank Mn. 8Weir and Intake Mn. 5Final Testing and Commissioning Mn. 3 Power House, Tail race Mn. 4 Access Road rehabilitation Mn. 3Contingencies Mn. 5

Total Cost Mn. 108Table 3: Project cost evaluation

Annual Energy generation = 4.5527 GWH

Tariff (For 1 KWH) =Rs 14.58 ( For year 1- 20)Total annual Income =Rs.14.58 x 4.5527 x 106

=Rs 66.37 Mn

Annual Operation and Maintenance cost with Project Monitoring Cost =Rs 7 Mn

Annual profit =Rs.59.37 Mn

Simple Pay Back Period =108 / 59.37=1 Year & 10 Months

Since the SPP is less than two years the Project is Viable.

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pubudu's small hydro ass

Documents

rated flow design

design of penstock

design details

designed flow

river flow

design of channel

image layout image

design of weir intake