122 CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
Photo 8.2 Powerhouse and tailrace of the Salleri Chialsa
mini-hydro scheme
8.2 Location of powerhouse
The location of the powerhouse is governed by the penstock
alignment since this building must be located at the end of
the penstock. Apart from this, the following criteria are recom-
mended for locating the powerhouse:
The powerhouse should be safe from not only annual floods
but also rare flood events. Discussions should be held with
the local community members to ensure that floodwaters
have not reached the proposed powerhouse site within at
least the past 20 years. For micro-hydro schemes of 50-100
kW it is recommended that the powerhouse be above the
50-year flood level.
It should also be possible to discharge the tailwater safely
from the powerhouse back to the stream.
If possible the powerhouse should be located on level ground
to minimise excavation work.
The proposed location should be accessible throughout the
year. At some places this may require constructing a new
foot trail.
The powerhouse should be located close to the community
that it serves, provided that the penstock alignment and
other parameters are feasible and economical. This will
reduce the transmission line cost, and if agro-processing
units are also installed in the powerhouse, the community
will not have to carry their grain for a long distance.
Other stability issues discussed in Chapter 9 should also be
addressed.
8.3 Design of powerhouse
8.3.1 GENERAL
A powerhouse that is similar to other local houses in the
community is generally economical and appropriate. The
community members will be able to construct such a building
with nominal supervision.
If a decision is made to construct the powerhouse similar to
other local houses, then the civil design input required is to
size the plan area of the building and design the machine
Photo 8.3 Powerhouse of the Jhankre mini-hydro
foundation. The area inside the powerhouse should be well
lit and ventilated with sufficient windows. Placing a few
transparent fibreglass sheets (skylight) in the roof will provide
additional illumination as can be seen in Photograph 8.3.
8.3.2 SIZE OF THE POWERHOUSE
The plan area of the powerhouse should be determined as
follows:
The size of the electro-mechanical equipment should be
obtained from the manufacturer.
All required equipment should be drawn to scale and placed
on the proposed powerhouse plan area. This may require a
few trials to determine the optimum layout.
Adequate space should be provided such that all equipment
is easily accessible. There should be a clear spacing of at
least 1 m around each item of equipment that has moving
parts (such as the generator, turbine and the belt drive).
Noted that if agro-processing equipment is installed, the
community members will regularly visit the powerhouse
(to process their grain). Therefore additional space is
required so that the powerhouse does not become
overcrowded and a potential area for accidents. It is
recommended that such additional space is provided as a
lobby at the entrance and the equipment is placed beyond
it. A lobby large enough for five people to wait with their
grain (about 3m x 3m) may be adequate in most cases.
Adequate windows should be provided for lighting and
ventilation. Note that the door and windows need to be
located such that they do not obstruct access to the
equipment. This requires co-ordinating the locations of the
equipment, windows and the door.
The powerhouse layout of the Jhankre mini-hydro scheme is
shown in Figure 8.1.
8.3.3 POWERHOUSE WALL AND OTHER DETAILS
Most houses in the hills of Nepal are constructed of stone
masonry in mud mortar. Wooden truss with corrugated iron
sheet (CGI), slates or straw thatching are used for the roofs. A
similar building is recommended for the powerhouse structure
with the following considerations: