Monthly Archives: May 2011

Civil structures Ghunsa microhydro project (GMP).

The microhydro plant consists essentially of the all the components that a bigger hydropower plant will consist of. This article will try to give real impression of what micro hydro plant will look like in the field after construction.Ghunsa microhydro project has been used in this article. This project is located at an elevation of 3500m above sea level at Taplejung district of Nepal. The plant generates 35Kw.


Intake, gravel trap and settling basin.
Intake consists of a chamber to collect water. A gravel trap is generally provided to exclude coarse sediment to enter the water way. If water has sediments that need to be addressed, then a settling basin is also provided. The inake of GMP is at the right bank of Yamatari river. The water gets frozen in winter season. Settling basin has not been provided in this project as the water qualtiy is good.

Intake stucture

River protection for intake

intake gate.JPG

Intake gate

Gravel trap flushing

Trashrack at intake

Gravel trap after the intake

The waterways consists of canal joining intake and forebay. Depending upon the topography, the canal is in filling or cutting as shown in the figures.

Canal in cutting

Canal in filling. (Notice seepage!)

Canal in cutting

Forebay is a water tank to hold water for specific time. The water from forebay is then tranmitted to powerhouse using penstock pipes. The forebay consists of a spillway to divert excess water. This maintains constant head (elevation of water) for the trubines in the powerhouse.

The forebay with spillway in the left. It also consist of pipe spillway at the center.

Penstock pipes
Penstock pipes transmitts the flow from forebay to powerhouse. Saddle support and anchor blocks are provided to hold the penstock in the fixed alignment.

Penstock alignment

Anchor block in penstock alignment

Powerhouse and tailrace
The flow from penstock strikes the turbine and generator produces electricity. The flow is then discharged back to original river. The powehouse of GMP is near the southern end of Ghunsa village.


Penstock inlet at powerhouse

The penstock inside the powerhouse


Powerhouse with tailrace outlet

Most efficient trapezoidal section of canal

The most efficient trapezoidal section of canal can be calculated as follows

canal section.JPG
Base width of the canal=B
Side slope=m (1V:mH)
Flow depth = h
Wetted perimeter= P

The cross sectional area, A=By+my^2
ie B= (A-m*h^2)/h
ie B=A/h-m*h
Wetted perimeter P= B+2*h *sqrt(m^2+1)
For most efficient channel, dP/dh=0
ie -A-m*y^2+2 y^2 sqrt(m^2+1)=0
ie B= y(2*sqrt(m2+1)-1-m)
Therfoer B/y=2*sqrt(m2+1)-1-m is the required relationship

Breaking Excel passoword

The password protection of MS-Excel are not intended for security of data but for security of input and output of worksheet.

You can crack the password of the protected worksheet by using following VBA procedure.

Sub PasswordBreaker()
'Author unknown
'Breaks worksheet password protection.
Dim i As Integer, j As Integer, k As Integer
Dim l As Integer, m As Integer, n As Integer
Dim i1 As Integer, i2 As Integer, i3 As Integer
Dim i4 As Integer, i5 As Integer, i6 As Integer
On Error Resume Next
For i = 65 To 66: For j = 65 To 66: For k = 65 To 66
For l = 65 To 66: For m = 65 To 66: For i1 = 65 To 66
For i2 = 65 To 66: For i3 = 65 To 66: For i4 = 65 To 66
For i5 = 65 To 66: For i6 = 65 To 66: For n = 32 To 126
ActiveSheet.Unprotect Chr(i) & Chr(j) & Chr(k) & _
Chr(l) & Chr(m) & Chr(i1) & Chr(i2) & Chr(i3) & _
Chr(i4) & Chr(i5) & Chr(i6) & Chr(n)
If ActiveSheet.ProtectContents = False Then
MsgBox "One usable password is " & Chr(i) & Chr(j) & _
Chr(k) & Chr(l) & Chr(m) & Chr(i1) & Chr(i2) & _
Chr(i3) & Chr(i4) & Chr(i5) & Chr(i6) & Chr(n)
Exit Sub
End If
Next: Next: Next: Next: Next: Next
Next: Next: Next: Next: Next: Next
End Sub

This piece of code was found here