A highly efficient and low-emission concept is the fuel cell gas turbine GT hybrid.. Hybrid systems are comprised of fuel cells integrated with a GT engine.. Both experimental and theore
Trang 1Fuel Cell/Gas Turbine Hybrid
S Samuelsen and J Brouwer,University of California, Irvine, CA, USA
& 2009 Elsevier B.V All rights reserved.
Introduction
With increasing energy demands, dwindling fossil energy
resources, and environmental concerns associated with
criteria pollutants and greenhouse gases, significant
at-tention in the power generation community has been
focused on increasing efficiency and reducing emissions
A highly efficient and low-emission concept is the fuel
cell gas turbine (GT) hybrid
Hybrid systems are comprised of fuel cells integrated
with a GT engine A variety of potential configurations have
been proposed and a number of cycles have been
investi-gated The advantage sought is a synergism that yields a
performance that exceeds the simple sum of the two
sys-tems Both experimental and theoretical analyses of hybrid
systems have demonstrated that, when appropriately
com-bined, remarkable performance attributes can result In
particular, hybrid systems are capable of (1) unusually high
fuel-to-end-use efficiency and (2) virtually zero emission of
criteria pollutants The environmental and energy-efficient
performance suggests that hybrid systems can contribute to
(1) new and secure fossil-fueled energy infrastructure,
(2) sustainable power generation when operated with
re-newable fuels, and (3) the provision of transportation fuels
including the introduction of the hydrogen economy
Theoretical analyses and early experimental results
show that no fossil fuel-based technology can compete
with the high efficiency and environmental performance
of hybrid systems In addition, the market applications for
hybrid technologies range from stationary to mobile, in
size from kilowatts to megawatts, and operate on fuels
from coal and biomass syngas fuels to natural gas and
hydrogen For stationary applications, prototypes have
been tested and the first commercial unit has been
deployed in a distributed generation installation In addi-tion, concepts are being actively developed for hybrid central plant installations For mobile applications, hybrid technologies are projected to meet the power and pro-pulsive requirements of locomotives, ships, and aircraft and thereby meet the expanding demands for high fuel-to-electricity efficiency and reduced environmental sig-nature for such systems
Although the potential for hybrid systems is signifi-cant, the front-end risk associated with developing the technology is considerable Broad investment in research
by industry, national laboratories, and universities is re-quired to meet the market penetration that is anticipated for hybrid technology
The Concept
Hybrid fuel cell GT systems are comprised of two major components: a high-temperature fuel cell (HTFC) and a
GT engine The concept was first conceived in the mid-1970s By 1998, more than 10 hybrid concepts had been patented, offering variations in fuel cell type, the position
of key components in the integrated system, and system operating pressure The basic concept is illustrated in
Figure 1, where a fuel cell replaces the combustor of a typical Brayton (GT) cycle This leads to direct fuel-to-electricity production from the fuel cell (in the place of chemical-to-thermal energy conversion of a combustor), with the waste heat of the fuel cell being used to provide all the compression power and the generation of add-itional electricity through a turbogenerator Note that electrochemical production of electricity lowers emis-sions and increases efficiency As a result, around 80% of
C Air
C
Fuel
~80%
~20%
Cathode Electrode Anode
Figure 1 Basic design concept of a hybrid gas turbine (GT) fuel cell system.
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