Herein, a fuel cell power system that works in CHP mode has been considered to provide electrical, heating, cooling and domestic hot water loads of buildings. The buildings tolerate hot summers and mild winters during their operation life. In previous research, the PEM fuel cell system was designed and number of fuel cell stacks to provide the required energy of the building was estimated. As a complementary investigation, the thermodynamic and environmental analysis of the mentioned system has been conducted in this research. Results have shown that for a 12 fuel cell stacks at a nominal capacity of 8.5 kW, the mass production of monoxide carbon, monoxide nitrogen and dioxide carbon are equal to 1272.621 (kg/year), 1609.056 (kg/year) and 26107.23 (kg/year), respectively. The mass production values are acceptable since it is within limitation ranges mentioned by many environmental protocols

Keivani Hafshejani, Maryam.

Ojakeh, Mojtaba.

Pourmahmoud, M.

shahrekord university of medical scinces

                                         VOL. 9, NO. 4, APRIL 2014                                                                                                                       ISSN 1819-6608            ARPN Journal of Engineering and Applied Sciences  ©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved.  www.arpnjournals.com   526THERMODYNAMIC AND ENVIRONMENTAL ANALYSIS OF A FUEL CELL POWER SYSTEM USED IN A BUILDING IN AHVAZ  M. Pourmahmoud1, M. Ojakeh2 and M. K. Hafshejani3 1Mechanics group, Andimeshk Branch, Islamic Azad University, Andimeshk, Iran 2Physics group, Dezful Branch, Islamic Azad University, Dezful, Iran 3Shahrekord University of Medical Sciences, Shahrekord, Iran E-Mail: maryam.keivani@yahoo.com  ABSTRACT Herein, a fuel cell power system that works in CHP mode has been considered to provide electrical, heating, cooling and domestic hot water loads of buildings. The buildings tolerate hot summers and mild winters during their operation life. In previous research, the PEM fuel cell system was designed and number of fuel cell stacks to provide the required energy of the building was estimated. As a complementary investigation, the thermodynamic and environmental analysis of the mentioned system has been conducted in this research. Results have shown that for a 12 fuel cell stacks at a nominal capacity of 8.5 kW, the mass production of monoxide carbon, monoxide nitrogen and dioxide carbon are equal to 1272.621 (kg/year), 1609.056 (kg/year) and 26107.23 (kg/year), respectively. The mass production values are acceptable since it is within limitation ranges mentioned by many environmental protocols.  Keywords: fuel cell power system, CHP mode, environmental analysis, mass production.  INTRODUCTION With the huge growth of energy demands in the beginning of the 21st century, the environmental considerations have become the center of interest for many energy engineers. A large effort has been conducted on generating clean energy without substantial environmental pollution or hazardous mass products. These difficulties, far from finding effective solutions, are continuously increasing, which suggests the need of new technological alternatives to guarantee the reliability and robustness of the technology.  In this regard, one of these technological alternatives is named on-site generation or distributed generation. It is well-established that many developed countries provide most portion of their energy by large centralized power plants. Interestingly these plants negatively affect environment and pollutions (Rosen et al., 2005). In this regard, cogeneration heat and power (CHP) systems are considered as an important issue in the field of non-Renewable sources.  Among several well-known cogeneration systems which are commonly employed in resilience buildings, the fuel cell systems are of the most important ones due to their benefits such as cost effectiveness (Rosen et al., 2005; Silveira et al., 1997). The use of fuel cells, micro gas turbines and internal combustion engines for OS-CHP, or on-site combined heat and power production in residential building, has been studied by several researchers ((Ehyaei and Bahadori, 2006; Ehyaei and Mozafari, 2010; Saidi et al., 2005a; 2005b; Renedo et al., 2006; Khan et al., 2004; Dentice et al., 2003; Miguez et al., 2004a; 2004b; Gigliucci et al., 2004; Kong et al., 2004; Maribu et al., 2007; Maidment and Tozer, 2002; Ziher and Poredos, 2006; Cardona et al., 2000) In the previous research, authors has considered the design and operating conditions of a CHP fuel cell system emphasis on entropy production (Pourmahmoud et al., 2014). The schematic diagram of the proposed system is illustrated in Figure-1. As seen in this schematic figure, the configuration of the designed system includes the fuel cell stacks, the burner, the steam reformer, the heat exchanger, the battery. In this system, the water heater was suggested to produce the electrical power of the building as well as some parts of the power required by the heat pump. The mechanical refrigerator needed for heating, cooling and DHW systems. The remaining part of the power for heat pump and mechanical refrigerator is provided by the exhaust gases. It should be mentioned that the consuming fuel of the burner and the reformer is natural gas.    Figure-1. Configuration of CHP fuel cell system.  The present research is aimed to shed light on the other aspects of the proposed CHP fuel cell (Pourmahmoud et al., 2014). As a complementary investigation, in this paper the environmental analysis of the mentioned system has been conducted.  System characteristics The operation of the CHP fuel cell system which is presented in Figure-1 can be described as the following:                                          VOL. 9, NO. 4, APRIL 2014                                                                                                                       ISSN 1819-6608            ARPN Journal of Engineering and Applied Sciences  ©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved.  www.arpnjournals.com   527first, the natural gas is fed through line (1) to the burner and the reformer sections. In the burner, natural gas is reacted with the air and burns. This generated heat is used to provide energy needs for the reformer section. In the reformer unite; the natural gas is reacted with the produced steam in the heater. In this stage, the produced hydrogen gas (H2) by reformer, is fed to PEM fuel cell (line 11). This hydrogen is reacted with air (line 7), to produce electrical power and hot water. Remaining part of air is discharged to atmosphere. For cooling of fuel cell, water is pumped to fuel cell (line 16), which is warmed up and fed to heat exchanger. In heat exchanger, this water is mixed with a part of hot water which produced in PEM (line 19) and is fed to storage tank through. Remaining part of produced water by PEM fuel cell, change to steam in heater, and is used in reformer. In previous research, the fuel cell stack with a nominal power of 8.4 kW is considered here, employing natural gas as fuel. Based on previous findings (Pourmahmoud et al., 2014), we understand that the maximum electrical power requirement is 32.96 kW, occurring between the hours of 7 and 8 p.m. in July. It is found that the maximum heating load is 1590 kW, occurring at 5 a.m. in January (Pourmahmoud et al., 2014). However, the maximum cooling load is 2028 kW, occurring at 3 p.m. in July (Pourmahmoud et al., 2014). Furthermore, the maximum domestic hot water energy requirement is 0.926 kW, occurring between 5 a.m. and 11 p.m. in January (Pourmahmoud et al., 2014).  A method to meet the energy needs of the residential building under consideration is to employ a number of fuel cell stacks to produce electricity to meet the electrical energy needs of the building, and to provide some part of the heating and cooling energy needs through a heat pump (Pourmahmoud et al., 2014). Results show that all the energy needs of the building can be met with 12 fuel cell stacks at a nominal capacity of 8.4 kW (Pourmahmoud et al., 2014). RESULTS AND DISCUSSIONS The variation of carbon monoxide and nitrogen monoxide mass production of the proposed CHP fuel cell system with respect to the variation of the ambient air temperature is illustrated in Figure-2.  From this figure, it can be observed that when the ambient temperature increases from 1oC to 40oC, the carbon monoxide mass production by each fuel cell stack increases from 0.0277(kg/sec) to 0.0316(kg/sec). In addition mass production of monoxide nitrogen increases from 0.0518(kg/sec) to 0.0557(kg/sec). Monoxide carbon and monoxide nitrogen mass production due to number of fuel cell stacks to meet the energy loads during the hours is shown in Tables 5-6 and 7-8, respectively. Maximum monoxide carbon and maximum monoxide nitrogen mass production occurs at 15 hour in 15 July and is equal to 0.378 (kg/sec) and 0.6672 (kg/sec), respectively.    Figure-2. variation of mass production with respect air temperature in one unit of CHP fuel cell stack.  Table-1. Carbon monoxide mass production from fuel cell stacks which operate in the residential building in kg/sec (January-June).  Hour Jan Feb Mar Apr May Jun 2 0.196 0.168 0.1132 0.0584 0.0294 0.0596 4 0.196 0.196 0.1132 0.0582 0.0293 0.0594 6 0.196 0.196 0.1132 0.0582 0.0293 0.0594 8 0.1686 0.168 0.0849 0.0292 0.0295 0.0598 10 0.1128 0.1128 0.0286 0.0297 0.0891 0.1208 12 0.0852 0.0566 0.0287 0.0604 0.151 0.1836 14 0.0286 0.0285 0.0582 0.0912 0.2128 0.2772 15 0.0286 0.0286 0.0582 0.122 0.2121 0.31 16 0.0286 0.0285 0.0582 0.0912 0.1812 0.2772 18 0.0852 0.0568 0.0288 0.0912 0.15 0.1842 20 0.1132 0.1132 0.0287 0.0596 0.0894 0.152 22 0.1686 0.1405 0.0568 0.0295 0.0592 0.09 24 0.168 0.168 0.0849 0.0292 0.0294 0.0596                                          VOL. 9, NO. 4, APRIL 2014                                                                                                                       ISSN 1819-6608            ARPN Journal of Engineering and Applied Sciences  ©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved.  www.arpnjournals.com   528Table-2. Carbon monoxide mass production from fuel cell stacks which operate in the residential building in kg/sec (July-December).  Hour July Aug Sep Oct Nov Dec 2 0.0602 0.0598 0.0594 0.0287 0.0849 0.168 4 0.06 0.0596 0.0295 0.0287 0.1132 0.168 6 0.06 0.0594 0.0295 0.0287 0.1132 0.1674 8 0.0909 0.09 0.0594 0.0287 0.0852 0.1405 10 0.153 0.1515 0.09 0.0582 0.0286 0.1128 12 0.2799 0.2763 0.1824 0.0885 0.0287 0.0283 14 0.3454 0.3421 0.2456 0.12 0.0584 0.0287 15 0.378 0.3732 0.2456 0.09 0.0584 0.0287 16 0.3454 0.3421 0.2448 0.12 0.0584 0.0286 18 0.2808 0.2772 0.183 0.0885 0.058 0.0568 20 0.1848 0.183 0.1204 0.0586 0.0287 0.0846 22 0.1216 0.1204 0.0894 0.0576 0.057 0.112 24 0.0906 0.06 0.0594 0.0287 0.0568 0.1395  Figure-3 shows that unlike monoxide nitrogen and monoxide carbon, mass production of dioxide carbon decreases when the inlet air temperature increases from 1oC to 40oC, it decreases from 0.802 (kg/sec) to 0.79843 (kg/sec). As we know, increasing ambient air temperature led to reduction heat rate burner and increasing mass flow rate of fuel. So mass production of dioxide carbon by burner increases. In the other hand, with increasing ambient air temperature, outlet pressure of compressor and power of compressor increase. So, net power of the system and outlet dioxide carbon of the reformer decrease. Increasing of mass production of dioxide carbon by burner is less than decreasing mass production of dioxide carbon by reformer. Therefore, total mass production of dioxide carbon by system decreases with increasing ambient air temperature. This variation is shown in Figure-3.  Furthermore, it should be noted that dioxide carbon mass production from fuel cell stacks which operate in the residential building is shown in Tables 1-5.  Table-3. Monoxide nitrogen mass production from fuel cell stacks which operate in the residential building in kg/sec (January-June).  Hour Jan Feb Mar Apr May Jun 2 0.3654 0.3132 0.2096 0.1066 0.0535 0.1076 4 0.3654 0.3605 0.2096 0.1064 0.0534 0.1074 6 0.3654 0.3647 0.2096 0.1064 0.0534 0.1074 8 0.2096 0.21 0.0527 0.0537 0.1611 0.2172 10 0.3132 0.3132 0.1572 0.0534 0.0536 0.108 12 0.1578 0.1052 0.0529 0.1086 0.2715 0.3282 14 0.1575 0.105 0.0529 0.1635 0.271 0.3282 15 0.0527 0.0527 0.1064 0.1635 0.3815 0.4923 16 0.0527 0.0527 0.1064 0.2184 0.3808 0.548 18 0.0527 0.0527 0.1064 0.1635 0.3258 0.4932 20 0.2096 0.2096 0.0528 0.108 0.1614 0.2725 22 0.3132 0.3132 0.1575 0.0533 0.0536 0.108 24 0.3132 0.261 0.105 0.0536 0.1072 0.1626                                            VOL. 9, NO. 4, APRIL 2014                                                                                                                       ISSN 1819-6608            ARPN Journal of Engineering and Applied Sciences  ©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved.  www.arpnjournals.com   529Table-4. Monoxide nitrogen mass production from fuel cell stacks which operate in the residential building in kg/sec (July-December).  Hour July Aug Sep Oct Nov Dec 2 0.1086 0.108 0.1074 0.0528 0.1575 0.3132 4 0.1084 0.1076 0.0536 0.0528 0.21 0.3132 6 0.1084 0.1074 0.0536 0.0528 0.21 0.3132 8 0.1632 0.1626 0.1074 0.0529 0.1575 0.2615 10 0.2735 0.273 0.1626 0.1064 0.0528 0.2096 12 0.4968 0.4941 0.3264 0.1605 0.0529 0.0525 14 0.6116 0.6028 0.4352 0.2164 0.1066 0.0528 15 0.6672 0.6576 0.436 0.1626 0.1066 0.0528 16 0.6105 0.6028 0.436 0.2168 0.1066 0.0528 18 0.4959 0.4941 0.3276 0.1608 0.1062 0.1052 20 0.3288 0.3276 0.2172 0.1068 0.0527 0.1572 22 0.1629 0.1084 0.1074 0.0529 0.105 0.261 24 0.218 0.2172 0.162 0.1058 0.1052 0.2092    Figure-3. Variation of mass production of dioxide carbon with respect air temperature in one unit of CHP fuel cell stack.                                                  VOL. 9, NO. 4, APRIL 2014                                                                                                                       ISSN 1819-6608            ARPN Journal of Engineering and Applied Sciences  ©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved.  www.arpnjournals.com   530Table-5. Dioxide carbon mass production from fuel cell stacks which operate in the residential building in kg/sec (January-June).  Hour Jan Feb Mar Apr May Jun 2 5.6119 4.8102 3.2056 1.601 0.8003 1.5998 4 5.6119 5.6119 3.2056 1.6012 0.8004 1.6 6 5.6119 5.6119 3.2056 1.6012 0.8004 1.6 8 4.8096 4.8102 2.4042 0.8005 0.8002 1.5996 10 3.206 3.206 0.8011 0.8 2.4 3.198 12 2.4039 1.6028 0.801 1.599 3.9975 4.7946 14 0.8011 0.8012 1.6012 2.3979 5.5951 7.1892 15 0.8011 0.8011 1.6012 3.1968 5.5958 7.987 16 0.8011 0.8012 1.6012 2.3979 4.797 7.1892 18 2.4039 1.6026 0.8008 2.3979 3.9985 4.794 20 3.2056 3.2056 0.801 1.5998 2.3997 3.9965 22 4.8096 4.008 1.6026 0.8002 1.6002 2.3991 24 4.8096 4.8102 2.4042 0.8005 0.8003 1.5998  Table-6. Dioxide carbon mass production from fuel cell stacks which operate in the residential building in kg/sec (July-December).  Hour July Aug Sep Oct Nov Dec 2 1.5992 1.5996 1.6 0.801 2.4042 4.8102 4 1.5994 1.5998 0.8002 0.801 3.2056 4.8102 6 1.5994 1.6 0.8002 0.801 3.2056 4.8102 8 2.3982 2.3991 1.6 0.8009 2.4039 4.008 10 3.9955 3.997 2.3991 1.6012 0.8011 3.206 12 7.1874 7.1901 4.7958 2.4009 0.801 0.8014 14 8.7813 8.7846 6.392 3.1988 1.601 0.8009 15 9.5784 9.5832 6.3912 2.3991 1.601 0.8009 16 8.7813 8.7846 6.3928 3.1988 1.601 0.8011 18 7.1865 7.1892 4.7952 2.4006 1.6014 1.6026 20 4.7934 4.7952 3.1984 1.6008 0.801 2.4045 22 3.1972 3.1984 2.3997 1.6018 1.6024 3.2068 24 2.3985 1.5994 1.6 0.801 1.6026 4.009  CONCLUSIONS Herein, the environmental consideration of a polymer electrolyte membrane (PEM) fuel cell power system, which is proposed for domestic application, has been investigated. The system was proposed to meet the energy requirements of the building in Ahvaz. Environmental analysis of this CHP system shows that by increasing of ambient air temperature from 1oC to 40oC, production of nitrogen monoxide and carbon monoxide increases by 7.5% and 14.06%, respectively and production of carbon dioxide decreases by 0.48%. It has been found that mass production of monoxide carbon, nitrogen monoxide and carbon dioxide are equal to 1272.621 (kg/year), 1609.056 (kg/year) and 26107.23 (kg/year), respectively. This data is useful for design reliable systems that pass the environmental protocol limitations.  REFERENCES  Rosen M.A., Lee N.M. and Dincer I. 2005. Efficiency analysis of a cogeneration and district energy system. Applied Thermal Engineering. 25: 147-159.                                            VOL. 9, NO. 4, APRIL 2014                                                                                                                       ISSN 1819-6608            ARPN Journal of Engineering and Applied Sciences  ©2006-2014 Asian Research Publishing Network (ARPN). All rights reserved.  www.arpnjournals.com   531Silveira J.L., Walter A.C.S. and Luengo C.A. 1997. A case study of compact cogeneration using various fuels. Fuel. 76: 447-451.  Ehyaei M.A. and Bahadori M.N. 2006. Selection of micro turbines to meet electrical and thermal energy needs of residential buildings in Iran. Energy and Buildings. 39: 1227-1234.  Ehyaei M.A. and Mozafari A. 2010. Energy, economic and environmental (3E) analysis of a micro gas turbine employed for on-site combined heat and power production. Energy and Buildings. 42: 259-264.   Saidi M.H., Ehyaei M.A. and Abbasi A. 2005a. Optimization of a combined heat and power PEFC by exergy analysis. Journal of Power Sources. 143: 179-184.  Saidi M.H., Ehyaei M.A., and Abbasi A. 2005b. Exergetic optimization of a PEM fuel cell for domestic hot water heater. ASME journal of fuel cell technology. 2: 284-289.   Renedo C.J., Ortiz A., Monana M., Silio D. and Perez S. 2006. Study of different cogeneration alternatives for Spanish hospital center. Energy and Buildings. 38: 484-490.   Khan K.H., Rasul M.G. and Khan M.M.K. 2004. Energy conservation in buildings: cogeneration and cogeneration coupled with thermal energy storage. Applied Energy. 7: 15-34.  Dentice M., Accadia D. and Sasso M. 2003. Micro-combined heat and power in residential and light commericial applications. Applied Thermal Engineering. 23: 1247-1259.  Miguez J.L., Murillo S. and Porteiro J. 2004a. Feasibility of a new domestic CHP tri generation with heat pump: I. Design development. Applied Thermal Engineering. 24: 1409-1419.  Miguez J.L., Murillo S. and Porteiro J. 2004b. Feasibility of a new domestic CHP tri generation with heat pump: II. Availability analysis. Applied Thermal Engineering. 24: 1421-1429.  Gigliucci G., Petruzzi L. and Cerelli E. 2004. Demonstration of a residential CHP system based on PEM fuel cells. Journal of Power Sources. 131: 62-68.   Kong X.Q., Wang R.Z. and Huang X.H. 2004. Energy efficiency and economic feasibility of CCHP driven by sterling engine. Energy Conversion and Management. 45: 1433-1442.   Maribu K.M., Firestone R., Marnay C. and Siddiqui A.S. 2007. Distributed energy resources market diffusion model. Energy Policy. 35: 4471-4484. Maidment G.G. and Tozer R.M. 2002. Combined cooling heat and power in supermarkets. Applied Thermal Engineering. 22: 653-665.   Ziher D. and Poredos A. 2006. Economics of a three-generation system in a hospital. Applied Thermal Engineering. 26: 680-687.   Cardona E., P. Sannino, A. Piacentino and F. Cardona. 2006. Energy saving in airports by three-generation. Part II: Short and long term planning for the Malpensa 2000 CHCP plant. Applied Thermal Engineering. 26: 1437-1447.   Bejan A. 1988. Advanced Engineering Thermodynamics. John Wiley and Sons, New York, USA.  Mozafari A., A. Ahmadi and M.A. Ehyaei. 2010. Optimization of micro gas turbine by exergy, economic and environmental (3E) analysis. IJ Exergy. 7: 1-19.  

Thermodynamic and environmental analysis of a fuel cell power system used in a building in ahvaz

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shahrekord university of medical scinces