In the present work the energetic and economical performance of different energy
systems for smart and micro-cogeneration has been analyzed. The analysis has been
carried out in order to compare the performance of energy systems under different
operating conditions and fuel feeding.
In particular, traditional energy systems (such as micro gas turbines and internal
combustion engines) and innovative energy systems (such as thermophotovoltaic
technology) have been analyzed.
In last years, the use of the traditional energy systems in residential smart and micro-
CHP has grown up and therefore they could be considered as a well-established technology.
For this reason, an analysis focused on the influence of the use of different fuels
(traditional fuels and fuels obtained from biomass) has been considered an interesting issue.
The analysis has been carried out following two different approaches: the development of a
zero-dimensional model implemented in MatLab environment and of a three-dimensional
model using the commercial code ANSYS CFX for thermofluiddynamic analyses.
The zero-dimensional model has been realized in order to investigate the performance
of an integrated system, which includes production, gathering, carriage and transformation
of biomass into renewable fuels and then into energy (both electrical and thermal) from an
energetic and economic point of view. The model allows the analysis of the main features
of the whole process in terms of efficiency of the transformation process and of efficiency
of different kinds of energy systems. The model has been applied to identify the system
configuration which maximizes economic profitability, with respect to the current scenario
which implies the fulfillment of environmental issues, of economic constraints, of reduced
impact on population and of high system efficiency. Moreover, the model is characterized
by a modular structure in order to simulate different plant layouts (different type of
biomasses, transformation processes and energy systems).
The three-dimensional model is focused on the CFD analysis of combustion in micro
gas turbines combustors. In particular, the behavior of combustors of two different 100
kWel micro gas turbines has been taken into consideration. The analyses have been carried
out in order to evaluate the combustor performances under different operating conditions in
terms of: thermal power, velocity and temperature profiles, concentration of chemical
species and formation of pollutant emissions such as CO and NOx. The analyses involve
the use of traditional fossil fuels, such as natural gas, and of fuels obtained from biomass
transformation processes, such as syngas from thermochemical gasification.
The innovative energy system analyzed in the present work is a thermophotovoltaic
system (TPV) applied to a condensing boiler for domestic application characterized by a
maximum nominal thermal power equal to 30 kWth. At first, the analysis has been
performed through the definition of different scenarios in order to investigate the energetic
and economic performance of TPV technology related to the actual values of system
efficiency and purchase costs and referred to a consolidated technology.
Moreover, a CFD analysis of the boiler has been carried out using the commercial code
ANSYS CFX. Numerical three-dimensional models have been developed to analyze the
boiler behavior both in the combustion chamber and in the water-gas heat exchanger. The
models allow the analysis of the whole boiler performance in terms of fluid dyynamic
behavior and heat transfer phenomena. At last, the models allow to estimate the deliverable
electric energy if TPV cells would be applied on boiler combustion chamber lateral walls