Evaluation of Redundancy for Power Generating Unit in a Cogeneration Power Plant

Redundancy system is very useful to enhance the performance and reliability
of the power generation system of a cogeneration plant. However, the associated
operating cost of redundancy system is very high. The common redundancies used in a
cogeneration power plant are public utility and generator set. In order to select the best
redundancy options which incurs minimum operating cost, it is required to evaluate the
cost of different redundancy options. In this paper, net present value model (NPV) is
developed to evaluate the cost of redundancy considering availability and reliability of the
cogeneration system. Two steps applied to evaluate the redundancy cost of the
cogeneration system. The first step is predicting the number of failures and downtime
hours using availability and reliability analysis because redundancy is frequently used
when the system failed. The second step is evaluating the cost of redundancy using NPV
model. The results indicate that the use of public utility as redundancy option is costly
compared to generator set option for long period of time. The major operation cost of
public utility is contributed by the maximum demand charge cost which is about 57.9% of
the total cost of redundancy. The study will be useful as a guide for the cogeneration
operation to evaluate and select the redundancy option.