CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
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2. Site selection and planning
2.1 Overview
The selection of an appropriate site in most micro-hydropower
schemes is an iterative process. In the Nepalese context, usually
some community members who have had previous exposure
to micro-hydropower technology approach funding agencies,
consultants or manufacturers depending upon their financial
resources and the size of the scheme. The technicians of the
agency concerned undertake a site visit to assess whether
the site is feasible for a micro-hydro installation. Based on
the feasibility report submitted by these technicians, the
community members and others involved in the process decide
whether to proceed further with the development of the
scheme.
Once the decision is made to proceed with the scheme, and if
it is in the upper range of micro-hydro (say above 20 kW)
then a detailed survey of the project area is undertaken and a
detailed design report is prepared. The sanction of loans,
subsidy and grants by funding agencies and banks are based
on this report. There are frequent meetings between the
concerned parties during this stage. For the lower end of micro-
hydro (say less than 20 kW), usually the manufacturers
undertake both the design and installation.
Apart from socio-economic factors such as the need for
electricity, affordability, and supply and demand, technically
the selection of an appropriate site depends on the following
two factors:
Stream flow
Topography
As mentioned in Chapter 1, the power available from a micro-
hydropower scheme is a function of both the flow and the
head which depends on the topography. Micro-hydro becomes
technically viable only if the combination of head and flow
are such that the demand of the targeted community can be
met. Under normal circumstances, the low season flow of the
river should be used while calculating the power output.
However if a micro–hydro is planned to be connected into a
grid to be operated in a commercial basis, then the plant
capacity should be optimised based on variations in river
flow and the tariff offered. For example the optimum plant
capacity for grid connected small hydropower plants in Nepal
seem to correspond to 40 – 50 per cent flow exccedance given
the hydrological characteristics of the streams in hills and
mountains of the country and the buy back rate (tariff)
currently offered by Nepal Electricity Authority at
NRs 4.25/unit during 5 months of the dry season and NRs