Solar PV water pumping study - FINAL REPORT ... - UNDP, Namibia

Feasibility Assessment for the Replacement of Diesel Pumps with Solar Pumps
FINAL REPORT: September 2006
Comparative PV Pumping and Diesel Pumping Costing Tool for Namibia
USER INFORMATION
NOTES ON FORMULAE'S USED
The LOOKUP formula was initially used to draw information out of the tables. However, this formula requires that the
information is sorted in alphabetical order, which is not always the case. In that case it is safer to use the combination
MATCH - Looks up a value in an array and returns the row number. Note that the '0' as the last parameter defines that
an exact match needs to be found, instead of the closest match ('1' or '-1'). This is what also solves the issue of non
INDEX - Returns the value from a single cell in an array, where the row (from MATCH above) and the column (fixed)
The formulae's are interlinked to replace the standard Lookup formulae.
Linear and exponential regression formulae
LINEST: Fits a linear regression curve. There must be more x values than y values. The arrays may not contain '0'
values. There may not be any empty cells in the x value array
TREND: Linear forecast to extend a series of x and y values
LOGEST: Fits an exponential curve to a row of x and y values.
GROWTH: Exponential forecast, similar to TREND.
FINANCIAL DEFINITIONS
All costs are in Namibian dollars inclusive of VAT.
All Life Cycle Costing calculations are done in constant 2006 dollars (exclusive of inflation).
Escalation is defined as the percentage price increase (positive) / decrease (negative) over and above the
inflation/deflation rate. The nominal escalation rate includes the inflation rate, while the real escalation rate exlcudes the
Real rate and inflation
The real discount rate, real loan rate and the real escalation rate are calculated by subtracting the inflation rate from the
current rates. This is not quite correct. For the record: For example, the real discount rate is equal to ((1 + nominal
discount rate)/(1 + inflation rate) - 1). The difference however is so small and the interest ranges quite "large" that a
ASSUMPTIONS
The boreholes have a sufficiently strong yield to allow for generally higher flowrates of the diesel pump in comparison to
The water in the borehole is of reasonable quality.
The sizing of a diesel system which results in under-loading the unit does not negatively impact on the life expectancy of
the unit, nor does it change the service intervals (in terms of decarbonisation).
The “non-linearity” factor of taper thread rising main pipes does not lead to more than 5% losses.
Site establishment costs are excluded as well as engine house construction.
The pumping systems are complete at the exit of the borehole (i.e. the costs of the distribution and reservoirs are
excluded from the calculation).
None of the system components are stolen.
No insurance of the pumping systems were considered.
There are no costs for the local operator.
The minor service on diesel pumping systems does not require transport from/to site.
The road conditions to site are suitable for 4 x 2 vehicles.
ERRORS AND DISCREPANCIES
Developments of the diesel price. There may be no escalation for five years and there may be 20% escalation for the
next five years. The forecast of the oil price is not a feasible exercise.
The cost reduction between a DRWS and a Private installation is a rough estimate.
Inaccuracies in the PVP manufacturers data.
Poor assessment of the maintenance and replacement costs and intervals.
The life cycle costing is conducted on an annual basis. When the maintenance and replacement intervals become close
to one year then the inaccuracies increase as the interval in years has to be an integer. This inaccuracy can be remedied
by calculating the life cycle cost on a monthly basis but that has not been implemented.
COLOUR CODES
User can enter data in these cells: Contain numerical values
Highlighted cells to indicate essential information
Contain either empirical or system sizing data
These cells form named ranges (one dimesional)
These cells form named arrays (two dimesional)
EMCON: Areas under construction, uncertainties about the selected values, are highlighted in yellow
EMCON: Marked for deletion
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