Trigeneration: an alternative for energy savings
Joel Herna´ndez-Santoyoa,b,*, Augusto Sa´nchez-Cifuentesb,1
aGrupo de Exergia, Instituto Mexicano del Petro´leo, Eje Central La´zaro Ca´rdenas No 152, 07730,
Ciudad de Me´xico, Mexico
bFacultad de Ingenierı´a, Universidad Nacional Auto´noma de Me´xico, Mexico
Accepted 1 January 2003
Abstract
The design of new processes focused towards a more efficient use of energy, is nowadays highly
desirable. In this paper, the design of a system of trigeneration is presented as an alternative way of
improved energy use in cogeneration systems. Savings are observed by the decrease of the fuel fed
to the turbogeneration equipment. A regenerative-cycle cogeneration system and a new trigenera-
tion systemwere studied, showing their benefits as well as the operation criteria for both processes.
# 2003 Elsevier Ltd. All rights reserved.
Keywords: Cogeneration; Trigeneration; Absorption chiller; Energy saving
1. Introduction
The alternative to design a new process for the energy saving in industrial plants
(properly say in power plants), is born from the concern for having a bigger yield
from the processes, giving as a result, a lower consumption of the natural resources
and a more economic performance of the industry.
The combined generation of thermal energy and electric power is nowadays one of the
technologies often used in industrial processes: however, as with all processes, there are
inefficiencies in its operation. Nevertheless, a trigeneration process is an alternative
design to increase the efficiency in the thermal and electric generation. In recent years,
the trigeneration system has been used like power generation and secondly for air con-
ditioning [1]. Trigeneration, also referred to as district energy,2 achieves a higher effi-
ciency and smaller environmental impact than cogeneration.3 The installation of a
0306-2619/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0306-2619(03)00061-8
1 Tel.: +52-55-56223138 or 39.
2 District energy is a system where the generated energy is used elsewhere.
3 With respect to greenhouse gas emission to the environment, as CO2, NOX, and SOX.
* Corresponding author. Tel.: +52-55-30038420; fax: +52-55-30038067.
E-mail address: jsantoyo@imp.mx (J. Herna´ndez-Santoyo), augsan@servidor.unam.mx
(A. Sa´nchez-Cifuentes).
Applied Energy 76 (2003) 219–227
www.elsevier.com/locate/apenergy
220 J. Herna´ndez-Santoyo, A. Sa´nchez-Cifuentes / Applied Energy 76 (2003) 219–227
Nomenclature
Cp Calorific capacity (kJ/kg �C)
E Electric energy (kWe)
F Mass flow (kg/h)
H Enthalpy (kJ/kg)
HR Heat rate (kJ/kW-h)
k Air’s isentropic constant
P Pressure (kg/cm2)
Q0 Thermal power (kWt)
rp Pressure ratio
RT Refrigeration tons
S Entropy (kJ/kg K)
T Temperature (�C)
W Power (kW)
� quality vapour
Abbreviations and subscript
g gases
GT gas turbine
HP high-pressure steam
in input
l liquid phase
LP low-pressure steam
MP medium-pressure steam
MRA absorption chiller
out output
PC po...
