Development of Analytical Tool for Energy Audit of Cogeneration plant (ATEAC)

Energy audit and management of a plant can be considered as a systematic
approach to maintain the performance of a plant at high efficiency. The tedious task
of energy audit of a cogeneration plant can be undertaken by aid of the analytical
method which represents the working principles of the respective equipment used in a
plant. The performance of the plant can be inefficient due to energy misusage and
energy lost and hence, identifying the operating parameters that cause energy losses
and misusage can be the technique for management of a cogeneration plant. This
research discusses an analytical method for energy audit of an existing cogeneration
plant in Universiti Teknologi PETRONAS (UTP). The analytical models were
developed for the gas turbine engine, heat recovery steam generator, steam absorption
chiller, air cooled chiller, cooling tower, and thermal energy storage. The study
involves the investigation of the energy lost and imbalances within the systems which
degrade the performance of the cogeneration plant. The models were defined based on
the principles of thermodynamics, mass and energy balance. The analytical models
were implemented using Matlab7.1 and the results were validated to that of the actual
operating data.
The results show that the analytical models developed are able to represent the
operating principles of all the systems in the plant. It was found that the performance
of the plant is not at optimum operation due to losses in the components of the plant.
The energy loss in the sub-systems of the cogeneration plant is found to be 35.23%.
The energy loss in the components of steam absorption chiller is 77.15% of the total
energy lost inside the components. The energy loss in air cooled chiller is found to be
70.6% of the total energy loss. The energy losses in the cooling tower due to
evaporated mass and convection heat transfer are 5.41% and 94.6% respectively. The energy losses in the thermal energy storage are found to be 5-22.4% of the total
energy lost in thermal energy storage. The analytical models also enable strategies for
optimization of the plant. Reduction in the amount of losses can be observed when
selected operating parameters are changed. It was found that by decreasing the inlet
temperature to the air compressor by 1-1.5 K, the net work of the turbine increases by
0.11-0.2%. In the air cooled chiller condenser, the energy loss can be decreased by
5.74-7.3% when the inlet air temperature is decreased by 1-1.5 K. In the cooling
tower, the energy lost by evaporated mass can be decreased by 1.01-1.5% at the same
inlet air temperature.
The analytical model can be used as a tool for energy audit and management of
the cogeneration plant. The energy conservation can be identified by quantifying the
percentages of energy losses in each component. The performance of the cogeneration
plant can be maintained at optimum by monitoring the operating parameters at
optimum levels.