Grid extension is another option for rural electrification in
Kenya. As of this writing, a fixed monthly cost of $1.59 and consumption
tariff of $0,03/kWh for the first 50 kWh, $1.36 for consumption
between 50 and 1500 kWh are charged by KPLC (Kenya
Power and Lighting Company) [50,51]. There is also an additional
upfront connection fee of $825, which is an obstacle for low income
potential customers in rural areas [51].
Considering the above mentioned costs, customers in rural areas
will pay roughly ten times more if the electricity is provided by a
hybrid renewable power system such as the one proposed in this
paper. In some literature this number is predicted to be twenty
times more in a micro-grid [51]. However, grid extension needs a
long term planning, proper infrastructure and expertise. Besides
that, it is expensive and needs a long term investment. In the report
prepared by Alliance for Rural Electrification [7] the cost of grid
extension including the materials, labour and other costs is stated
to be $12,550 per kilometre. Concerning this number and also
considering the optimized system as a reference the break-even
point of the grid extension is 3 km which is a relatively short distance.
It is evident that the proposed stand-alone system is more
viable for remote and rural areas with low-consumption
consumers.
5.2. Sensitivity results
As stated previously, the optimization results are based on the
verified prices and the estimated prices taken from different
websites and contacting with several companies [52]. Due to the
uncertainties related to the cost assumptions, a sensitivity analysis
has been done to attain a more realistic system design.
The capital cost and the O&M cost of the biogas engine generator
set varies dramatically in the market. This is due to the difference
in the prices offered by manufacturer and also the cost of
the O&M of the engine and the digester system. Due to the transportation
cost and market fluctuations, the diesel price also can
vary significantly locally and from time to time [53].
The sensitivity results for the three chosen parameters are
shown in Fig. 11. The optimization results, which are described in
the previous section, are based on the values mentioned in Table 5
(the diesel price of 1.1 $/L, the biogas system capital cost of $1500