Experimental tests of a small-scale microturbine with aLiquidDessicantCoolingSystem, Sci ...
[ Pobierz całość w formacie PDF ]
INTERNATIONAL JOURNAL OF ENERGY RESEARCH
Int. J. Energy Res. (2012)
Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/er.2914
RESEARCH ARTICLE
Experimental tests of a small-scale microturbine with a
liquid desiccant cooling system
M. Badami, M. Ferrero and A. Portoraro
*
,
â€
Dipartimento di Energetica, Politecnico di Torino, Torino, Italy
SUMMARY
In a trigeneration plant, the thermal energy recovered from the prime mover is exploited to produce a cooling effect.
Although this possibility allows the working hours of the plant to be extended over the heating period, providing summer
air conditioning through thermally activated technologies, it is rather dif
nd in the literature experimental data on
trigeneration plants operation, and the availability of performance characteristics at off-design conditions is anyway limited.
The paper has the aim of showing the experimental data of a real trigeneration system installed at the Politecnico di Torino
(Turin, Italy), composed of a natural gas 100 kW
el
microturbine coupled to a liquid desiccant system. The data are
presented for both cogeneration and trigeneration con
cult to
gurations, and for full and partial load operations.
An energetic and economic performance assessment at rated power operation is presented, and compared with the partial
load operation strategy. The primary energy savings are calculated through a widely accepted methodology, proposed by
the European Union, and through another methodology, reported in literature, which seems to the Authors more suitable
to describe the energetic performances of trigeneration plants. Copyright © 2012 John Wiley & Sons, Ltd.
KEY WORDS
cogeneration; trigeneration; combined heat cooling and power (CHCP); desiccant cooling; microturbine; economic assessment;
partial load; experimental test
Correspondence
*A. Portoraro, Dipartimento Energia, Politecnico di Torino, C.so Duca degli Abruzzi 24, Torino, Italy.
â€
E-mail: armando.portoraro@polito.it
Received 26 July 2011; Revised 7 November 2011; Accepted 12 February 2012
1. INTRODUCTION
Many authors have conducted detailed studies on this
subject; a comprehensive review of trigeneration plants,
based on prime movers, is reported in [1]; an analytic method
than can be used to evaluate the performances of small scale
trigeneration plants, by means of energetic indexes and for
different operation strategies, was presented in [2] and [3].
Other researches have dealt with the development of
simulation models (see [4,5]), that are able to reproduce the
behaviour of a CHCP plant, for different load requirements
and ambient conditions, while a modelling of a microgastur-
bine for the integration with an absorption chiller is presented
in [6]. A performance analysis of CHCP and CHP systems
operating following the thermal and electric load was
presented in [7], considering rated power operation
strategies. In [8], an exergy and thermoeconomic analysis
of a CHCP system has been performed, to investigate the
effect of several operational parameters such as the air
compressor pressure ratio and the turbine inlet temperature
on the rst and second laws efciencies.
All these studies were based on nominal data, but it
Reducing primary energy consumption and increasing the
ef
ciency of energy processes today represents an impor-
tant goal in many research areas.
Among the actual technologies that allow an ef
cient
exploitation of primary energy, the possibility of producing
thermal and electrical energy from the same process
(Combined Heat and Power production, CHP) is one of the
most interesting opportunities of reducing energy consump-
tion in both residential and industrial applications. Even
greater savings can be obtained thanks to the conversion of
thermal energy into cooling energy, by means of thermally
activated technologies (TAT); by this way, the cogeneration
concept is extended to trigeneration (Combined Heat,
Cooling and Power production, CHCP) and a CHP plant
can operate also in the summer season, by providing, for
example, air conditioning in tertiary applications. Intense
investigations on the performances of CHCP plants have
been carried out over the last few years to evaluate the real
energetic and economic convenience of this technology, with
respect to the separated cooling generation.
is
important
to underline that discrepancies between
manufacturers
’
data and on-
eld test data may occur. Thus,
Copyright © 2012 John Wiley & Sons, Ltd.
M. BADAMI, M. FERRERO AND A. PORTORARO
Experimental tests of a small-scale MGT with a liquid desiccant system
real operational data can differ from the datasheet
performances, and the results obtained from energetic and
economic assessments can be less representative than the
operational gures obtained from the real plants.
However, it is rather difcult to nd in the literature
experimental data on trigeneration plants operation, and the
availability of performance characteristics at off-design
conditions is anyway limited; on this subject, an energetic
assessment based on real operational data of a microturbine
(MGT) coupled to an absorption chiller is presented in [9]
and in [10], and an experimental characterization of the per-
formance of a CHCP systemmade up of an engine generator
coupled to a liquid desiccant system was conducted in [11].
The Authors
’
researches on trigeneration have been
focused on the study of the performance of two small-scale
trigeneration plants installed at the Politecnico di Torino
(Turin, Italy). The rst plant is constituted by an ICE
cogenerator capable of 126 kW
el
coupled to a liquid
desiccant system (hereafter ICE-D), while the second one
is made up of a 100 kW
el
natural gas microturbine with
an absorption chiller (hereafter MGT-A).
The rst work was presented in [12], where a preliminary
energetic analysis of performances on the nominal point was
carried out for the ICE-D plant. These energetic analysis were
dealt with in more depth in [13], where the Authors introduced
the calculation of the Primary Energy Savings (PES) by means
of two different procedures: a commonly accepted methodol-
ogy proposed by the European Union [14], and through the
TPES methodology, which was introduced in [15], and which
seems to be more appropriate to describe the energetic perfor-
mances of trigeneration plants. The analyses were conducted
in winter and summer nominal point condition. The Authors
compared the energetic and economic performance of the
ICE-D plant, with those of the MGT-A plant, in [16] and
[17]. PES and TPES indexes were calculated and compared,
considering the typical yearly operating hours of the Politec-
nico di Torino heating and cooling plants. The economic
analysis was aimed at investigating the effect of operating
the plants in the three hourly time bands foreseen by the elec-
tric energy contract undertaken by the Politecnico di Torino.
Recently, a modication in the MGT-A plant design
allowed the hot water recovered from the MGT to be sent
to the desiccant system (hereafter MGT-D plant). Several
experimental test sessions were conducted on the new
MGT-D plant layout, and the aim of this paper is
presenting the obtained experimental data in both cogenera-
tion and trigeneration congurations, at full and partial
load conditions. A preliminary energetic and economic
performance analysis of the plant was also conducted over
a whole year of operation. The results are thoroughly
discussed in the following sections.
conceived to provide an air
–
conditioning service to a small
building where several teaching classrooms are located. The
system is also used for didactics and scienticresearch.
The main components of the plant are a natural gas
microturbine and a desiccant cooling system. The main
technical data of these components are shown in Table I
and Table II. The electrical, heating and cooling capacities
of the plant are 100/170/80 kW, respectively. The heat is
recovered from an exhaust gas/water heat exchanger. The
cogenerator has an electronic power unit, made up of an
AC/DC-DC/AC converter, which allows the MGT to operate
at a nominal xed speed of 68000 rpm, while delivering
50Hz AC to the grid, also at partial load conditions.
The heat recovered from the prime mover is exploited in
the desiccant cooling unit, a Thermally Activated Technol-
ogy (TAT) device. Each unit is composed of two sections:
a conditioner and a regenerator. The conditioner is able to
produce a cooling effect from the dehumidication obtained
through the sorption of the humidity in an external airow of
5000 m
3
/h, by means of an LiCl-water solution. Then, the
moisture is desorbed from the solution in the regenerator,
by means of a second external 5000m
3
/h air ow [13]. The
treated air is then sent to the Air Handling Unit of the
building. The experimental data shown in this paper have
been obtained with three desiccant units in operation.
The plant congurations in cogeneration and trigenera-
tion mode are shown in Figure 1 and Figure 2, respectively.
The experimental data are acquired by a measurement
system. The measurement points (whose positions in the
Table I. Main manufacturer
’
s data of micro gas turbine.
Elliott Energy Systems -
TA100R
Manufacturer and model
Fuel Natural gas
Nominal fuel input power 345 kW
Gross electrical power 105 kW
el
Net electrical power 100 kW
el
Thermal power 170 kW
th
Speed 68000 rpm
Power electronic AC/DC - DC/AC converter
Fuel gas pressure delivered by the grid 0.02 bar
Fuel gas pressure delivered to the
combustion chamber
~ 5 bar
Table II. Main manufacturer
’
s data of each desiccant cooling
unit.
DuCool-Du Handling
DH3400
Manufacturer and model
5000m
3
/h
Process air mass
ow
2. PLANT AND MEASUREMENT
SYSTEM DESCRIPTION
5000m
3
/h
Regeneration air mass
ow
Dehumidi
cation nominal capacity
~ 42 kW
Desiccant solution
LiCl - water
LiCl solution mass concentration
40%
A small-scale trigeneration plant has been set up and installed
at
Number of operating units
3
the Politecnico di Torino, Turin, Italy. The plant was
Int. J. Energy Res.
(2012) © 2012 John Wiley & Sons, Ltd.
DOI: 10.1002/er
 Experimental tests of a small-scale MGT with a liquid desiccant system
M. BADAMI, M. FERRERO AND A. PORTORARO
Figure 1. Cogeneration mode. plant scheme with sensors and auxiliary component power.
Figure 2. Trigeneration mode. plant scheme with sensors and auxiliary component power.
plant scheme are shown in Figure 1 and in Figure 2) and
the relative parameters are summarized in Table III. A
Labview data acquisition tool has been setup in order to
sample and store the most important operating parameters.
Acquisition and control operations have been performed
either in a onsite or in remote mode.
trigeneration mode, on a typical summer
’
sday. Table IV
shows the ambient conditions for the two days. In each
experimental test, the system is operated at four different
loads: rated power and 80%, 60%, 40% of the rated power.
3.1. Cogeneration mode
3. EXPERIMENTAL DATA
The main experimental data obtained from the tests in CHP
conguration are presented in Table V. These data represent
a typical operating day in the winter period. The obtained
electrical and thermal efciencies are reported in Figure 3,
while several temperature trends are shown in Figure 4.
A set of experimental data is presented in this section. The
set refers to two operational tests that were carried out,
in cogeneration mode, on a typical winter
’
s day, and in
Int. J. Energy Res.
(2012) © 2012 John Wiley & Sons, Ltd.
DOI: 10.1002/er
Table III. Plant measurement system.
Measure Point
Parameter checked
Measurement system
Accuracy
T0
Outdoor air temperature (
C)
Resistance temperature detector class A
0.2
C
Compressor inlet temperature (
C)
0.2
C
T1
Resistance temperature detector class A
T8
Supply air temperature before desiccant conditioner (
C)
Resistance temperature detector class A
0.15
C@0
C
0.35
C @ 100
C
T9
Supply air temperature after desiccant conditioner (
C)
Resistance temperature detector class A
0.15
C@0
C
0.35
C @ 100
C
T3
EGT - Exhaust gas temperature (
C)
Thermocouple type K
1
C
Exhaust gases temperature before heat recover exchanger (
C)
1
C
T4
Thermocouple type K
T5
Exhaust gases temperature after heat recover exchanger (
C)
Thermocouple type K
1
C
Inlet natural gas temperature (
C)
0.5
C
T2
Thermocouple type K
T6
Hot water temperature before heat recover exchanger (
C)
Thermocouple type K
0.5
C
Hot water temperature after heat recover exchanger (
C)
0.5
C
T7
Thermocouple type K
T10
Regenerated fresh water temperature from cooling tower to
desiccant conditioner (
C)
Resistance temperature detector class A
0.15
C@0
C
0.35
C @ 100
C
T11
Regenerated fresh water temperature from desiccant conditioner
to cooling tower (
C)
Resistance temperature detector class A
0.15
C@0
C
0.35
C @ 100
C
p0
Outdoor air pressure (bar)
Absolute pressure transducer
0.4mbar @ 20
C
p2
Inlet natural gas pressure (bar)
Absolute pressure transducer
0,075% (deviation)
PQ
Electric power produced by alternator (kW
el
)
Voltmeter, ammeter and cos
j
-meter
Voltage and current
0.25% FS
Electric energy sold in grid parallel (kWh
el
)
Electric Meter
Power
0.50% FS
Power factor
1% FS
Harmonic distortion
0.20% FS
RH0
Outdoor air relative humidity (%)
Ta-Cr capacitive sensor
2%
RH8
Supply air before desiccant conditioner relative humidity (%)
Ta-Cr capacitive sensor
3%
RH9
Supply air after desiccant conditioner relative humidity (%)
Ta-Cr capacitive sensor
3%
Gas input to engine mass
ow (Sm
3
/h)
MF2
Diaphragm gas
ow meter
0,5%
Hot water
ow to desiccant regenerator (m
3
/h)
MF7
Constant electromagnetic
eld
0,2%
MF11
Regenerated fresh water
ow from cooling tower to desiccant
conditioner (m
3
/h)
Constant electromagnetic
eld
0,2%
GA
CO
2
,NO
x
, CO and O
2
concentrations in exhaust gases (ppm)
CO
2
,NO
x
, CO: Not Dispersive Infrared
technique;
O
2
: electro-chemical method
O
2
0.3 Vol.%
CO
20 ppm
NO/NO
2
5 ppm
 Experimental tests of a small-scale MGT with a liquid desiccant system
M. BADAMI, M. FERRERO AND A. PORTORARO
Table IV. Ambient conditions during tests.
Cogeneration
mode
Trigeneration
mode
p0 - average pressure (bar)
0.993
0.980
T0 - average temperature (
C)
2.5
29.0
RH0 - average relative
humidity (%)
80
55
Table V. Cogeneration mode experimental data.
% of rated power
100%
80%
60%
40%
Figure 4. Cogeneration mode: measured temperatures as a
function of P
el.
P
el,g
(kW)
100
79.9
60
40
P
el
(kW)
95.0
74.9
55.0
35.0
P
th
(kW)
174.9
167.3
154.0
146.9
P
fuel
(kW)
382.4
338.9
301.3
269.1
respectively; T
6
and T
7
are the inlet and outlet temperatures
of the water in the heat exchanger, respectively.
The fuel input power P
fuel
is determined as follows:
Z
24.8%
22.1%
18.3%
13.0%
el
EUF
70.6%
71.5%
69.4%
67.6%
T1 (
C)
11.3
11.8
11.9
11.3
p2 (bar)
1.180
1.178
1.178
1.180
P
fuel
¼
LHV
V
MF2
(2)
T2 (
C)
11.2
11.6
11.8
12.1
MF2 (m
3
/h)
34.3
30.5
27.1
24.2
where V
MF2
is the natural gas volumetric ow rate
measured during the test, corrected with temperature and
pressure of the fuel at test conditions, and LHV is the lower
heating value of the fuel, which is assumed equal to 9.45
kWh/Sm
3
. The pollutant emissions are expressed in parts
per million (ppm) and are referred to dry exhaust gases,
at 15% of O
2
content.
Some discrepancies between the measured data and the
manufacturer
’
s data of the microturbine can be observed:
at full load, the maximum power produced is about 95
kW
el,
while 100 kW
el
are reported in the mGT datasheet
(see Table I). Moreover, a net electrical efciency of
24.8% was calculated by means of the experimental data,
while a value of 29.0% can be deduced from the technical
data provided by the manufacturer.
GA - NO
x
(ppm)
15
13
14
19
GA - CO (ppm)
12
30
78
143
GA - O
2
(% vol)
17.8
18.2
18.5
18.8
MF7 (kg/s)
4.3
4.3
4.3
4.3
3.2. Trigeneration mode
In the summer season, the exhaust gases are all only used in
the desiccant unit to produce cooling power, and there is
therefore not surplus to use for heating purposes. The main
experimental data obtained from the tests in CHCP congu-
ration are presented in Table VI. These data represent a
typical operating day in the summer period. The obtained
electrical and thermal efciencies are reported in Figure 5,
while the main temperature trends are shown in Figure 6.
The thermal and fuel input powers are again calculated
using equation (1) and (2), respectively, while the cooling
power was calculated by means of the equation (3):
Figure 3. Cogeneration mode: electrical and thermal ef
ciency
of the microturbine.
The gross electrical power P
el,g
, produced by the MGT
generator, is measured by a grid analyzer; the total power
P
el
produced by the microturbine (taking into account the
auxiliaries consumption of the prime mover), is calculated
as the difference between P
el,g
and the power of the on-board
fuel compressor (5 kW). The net thermal power P
th
is
determined, from experimental data, using equation (1):
P
c
¼
V
air
r
air
h
8
h
9
ð
Þ
(3)
P
th
¼ m
MF
7
c
p;H
2
O
T
7
T
6
ð
Þ
(1)
where V
air
is the nominal volumetric ow rate of the
treated air for the three units, which is equal to 15000m
3
/h;
r
air
is the average density of the treated air;
h
8
and
h
9
are
where m
MF7
and c
p
;
H
2
O
are the mass ow rate and the
average specic heat at constant pressure of water,
Int. J. Energy Res.
(2012) © 2012 John Wiley & Sons, Ltd.
DOI: 10.1002/er
Â
[ Pobierz całość w formacie PDF ]