This research consists of both theoretical and experimental sections presenting a novel scenario for the consumption of hydrogen in the polymer electrolyte membrane fuel cell (PEMFC). In the theory ...section, a new correction factor called parameter δ is used for the calculation of fuel utilization by introducing concepts of “useful water” and “non-useful water”. The term of “useful water” refers to the state that consumed hydrogen leads to the production of liquid water and external electric current. In the experimental section, the effect of the relative humidity of the cathode side on the performance and power density is investigated by calculating the parameter δ and the modified fuel utilization at 50% and 80% relative humidity. Based on the experimental results, the maximum power density obtained at 50% and 80% relative humidity of the cathode side is about 645 mW/cm2 and 700 mW/cm2, respectively. On the other hand, the maximum value of parameter δ for a value of 50% relative humidity in the cathode side is about 0.88, while for 80% relative humidity it is about 0.72. This means that the modified fuel utilization for 50% relative humidity has a higher value than that for 80%, which is not aligned with previous literature. Therefore, it is necessary to find an optimal range for the relative humidity of the cathode side to achieve the best cell performance in terms of the power generation and fuel consumption as increasing the relative humidity of the cathode itself cannot produce the best result.
Increasing the inlet air temperature causes a reduction in the air mass flow rate, and the efficiency and output power of a gas power plant will reduced. To compensate this power and efficiency ...decrease, different cooling systems can be applied to the inlet air flow. This paper introduces and analyzes different gas turbine cooling systems and studies their effect on the efficiency of Zanbagh power plant’s G11 gas unit by extracting the governing equations regarding the characteristic curve and coding in the MATLAB software. In average, the simulation results show that reduction of 1 °C of inlet air temperature between 14 °C and 50 °C causes an efficiency and power output increase by 0.085% and 0.16 MW, respectively. The maximum cycle efficiency increase applied to cool the inlet air is around 2.7%, which can be achieved using the wet compression method. In addition, this method can reduce fuel consumption by 5% in comparison to a normal cycle.
The proton exchange membrane fuel cell could be made more commercially viable by substituting the expensive platinic catalyst without loss of performance. This should be done simultaneously through ...optimization and use of a non-precious metal catalyst. In this study, multi-objective optimization of the catalyst layer was done on nonprecious metal catalysts. Nitrogen-doped graphene (NG)-based cobalt was synthesized as a non-precious metal catalyst. Differential equations were solved at the modeling stage by the shooting method, and objective functions were solved at the optimization stage using sequential quadratic programming. NG-based cobalt was evaluated in a cell and then compared with the platinum catalyst. Results present the synthesized non-precious catalyst as an appropriate replacement for existing precious metal catalyst. Also, the polarization curve demonstrates that the current modeling is in good agreement with NG-based cobalt catalyst. Finally, the Pareto curve at the voltage of 0.6 V (and 300 A/m
2
current density in the base case) indicated that the best tradeoff between cost and performance of the catalyst layer was achieved when the current density was increased in the range of 5% to 15%.
Ambient air temperature increase, in a gas power plant, causes the intake air mass flow rate to be decreased and can have a significant reducing effect on output power and efficiency. To compensate ...for this reduction, at different climate conditions, various systems can be used to cool the inlet air. To predict the performance of a gas turbine at off-design conditions (by changing surrounding conditions and/or the air cooling method), modeling of the unit performance is required. Due to the high consumption of water and electricity in the conventional cooling systems, in this paper, in addition to introducing an off-design algorithm, governing equations of each cycle elements were inferenced by their characteristic curve. By developing code in MATLAB software, the effect of applying a novel convergent–divergent system on GE-F5 gas units in Yazd Zanbagh power plants was studied. The results show that in a temperature range between 14 and 50 °C, for each degree decrease in ambient air temperature, an approximately 8.99 kW increase in output power can be obtained. The main advantage of this system is the capability of its application in both dry and humid regions. In addition, the refrigerant medium is not required, which makes this system desirable to use in arid areas.
It is widely known that organic and inorganic coatings absorb more of the solar spectrum, and due to a considerable share of 45% infrared radiation, the energy efficiency drop by the increasing of ...temperature should be considered. The purpose of this study is to implement a system to characterize silicon solar cell performance and increasing energy efficiency by imposing such coatings as infrared wave absorber to overcome the Shockley–Queisser limit. In other words, this research efforts to improve cell efficiency (coating effects) in addition to imposing the efficiency decreasing effects (temperature increasing). The core of the study is laboratory and experimental set-up measurements to find an organic absorber with the highest absorbance. Ruthenium-based dye, N719, has shown the best performance in experimental conditions and heat extraction to enhance cell energy efficiency. Due to increased absorption in a solar cell (SC), to control the temperature rise of the system, the fan is used as a cooling system. The imposing of N719 results in increasing energy efficiency by up to 1.38%. It is worth noting that a 1.60% increase in energy efficiency is observed due to temperature reduction by 2 degrees.
•A novel quasi-dynamic energy analysis of a BIPVT system considering triple benefits.•Developed thermodynamic and heat transfer model for BIPVT-DSF using MATLAB software.•Deep retrofit energy ...efficiency and renewable energy measure for existing building.•Sensitivity analysis for chimney and blanket modes of DSF with different layers.•Significant potential for improvement in building energy performance in Middle East.
This paper presents an energy analysis through simulating a building integrated photovoltaic thermal double skin façade (BIPVT-DSF) and aims to fill the gap for the development of a quasi-dynamic model for BIPVT systems in Middle Eastern climate condition. It considers cooling and thermal load reduction and power generation over a one-year period. The paper focuses on energy efficiency retrofitting within the Middle Eastern climate. The methodological approach is based on analytical modeling of the temperature and velocity profiles between the outer and inner façades through thermodynamic and heat transfer phenomena. The paper describes how significant potential exists for cooling load reduction. The results of this study provide wider investigations on the thermal energy performance of the BIPVT system based on hourly and daily frequencies. According to the quantitative outputs, a suggested BIPVT-DSF system has the capability of reducing annual cooling and thermal loads by 251,623 (kWh) and 17,811 (kWh), respectively. In addition, the paper concludes that a photovoltaic system with the peak power of 10.6 (kW) (a) can generate grid connected electricity of 18,064 (kWh) annually and (b) can improve the energy performance index of the existing building by 34.3 percent. Thus, BIPVT-DSF can be considered as an appropriate energy efficiency solution for the building sector in the Middle East region.
•4E analysis of a building integrated photovoltaic thermal system is investigated.•The scenario is based on the variation via glass windows and PV module surface area on the outer façade.•A scenario ...with the highest PV module surface area with a payback time of 1.58 (years) has been suggested.•The life cycle revenue of 55,157 ($) is suggested as a feasible retrofit measure as a result of the (4E) analysis.
In this research paper, energy, exergy, economic and environmental analysis of a building integrated photovoltaic thermal system is investigated. To cover the aim of the research, the impact of a system as a retrofit solution for the existing office building has been evaluated in different scenarios through various key performance indicators including generated electricity, energy and exergy efficiency, greenhouse gas emission reduction and life cycle cost. The scenario development for the analysis is based on the variation between glass windows and photovoltaic module surface area on the outer façade. According to the results of the study, a scenario with the lowest photovoltaic module and highest glass windows surface area has been suggested due to the highest energy efficiency, lowest initial investment, lowest energy consumption and emission for manufacturing. Besides, a scenario with the highest photovoltaic module and zero glass windows surface area has been suggested because of the highest lifetime generated and avoided energy and emission reduction, lowest payback time and greenhouse gas rate as well as highest life cycle revenue. In conclusion, a scenario with the highest photovoltaic module surface area with a payback time of 1.58 years and a life cycle revenue of 55,157 (USD) has been suggested as a feasible retrofit measure as a result of the energy, exergy, economic and environmental analysis.
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•Propose highly-efficient solar air heater with octagonal geometry and flat absorber.•Present an experimental study for 15 sunny days at three different airflow rates.•The proposed ...solar air heater achieved an average daily efficiency of more than 78%•Simple a payback and an internal rate of return of the project are 5.17 years and 23.91 %
This research study developed an innovative high-efficiency solar air heater (SAH) employing symmetrical geometry and a flat absorber plate. Also, an experimental setup of the proposed SAH was designed, fabricated and tested during the application in the winter season. Accordingly, comprehensive information including a list of measurement instruments, an experimental procedure, and a measurement strategy, is being presented. As a critical outcome, the maximum difference between ambient temperature and system outlet temperature for three different inlet airflow rates containing 0.046, 0.034 and 0.022 kg s−1 were 10.75, 14.24 and 18.56 °C, respectively. Moreover, the daily thermal efficiency of SAH has been analyzed. The empirical results reveal that the average daily energy and exergy efficiencies of the proposed SAH were 78.73 % and 32.87 %, respectively. Also, based on the results of economic feasibility study, the fabrication of the proposed SAH is cost-effective with a simple payback of 5.17 years, and an internal rate of return of 23.91 %. Finally, time-dependent mathematical modeling was developed, by coding in MATLAB software and solved by analytical methods, to investigate the dynamic heat transfer among system components as well as the hourly thermal performance. To validate the model, the deviation of actual against modeling values was examined by calculating the mean absolute percentage error. The results demonstrate that with an error of less than 3 %, the model has acceptable accuracy at predicting temperature values.
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•A Double skin Façade (DSF) was designed, fabricated and integrated with a double glazed window.•A numerical simulation was developed on the DSF.•The model predictions presented a ...good agreement with the experimental measurements.•The technical potential of energy saving by extension of the proposed system was estimated.
Peak loads in Iran’s national electrical grid are always appear during summers days where a significant part of them is due to cooling systems in the buildings. In this paper a prototype Double Skin Façade (DSF) integrated into a Double Glazed Window (DGW) has been designed and retrofitted to increase the efficiency of the cooling system of a typical sunshine oriented office room. Temperature profiles on inner and outer surfaces of this office have been recorded before and after implementing this energy saving method. On the other hand, a numerical simulation was developed in order to model the behavior of the system where the inputs of the model are environmental parameters such as solar irradiation, wind velocity and ambient air temperature. The simulated model was fully validated by implementing a local experimental setup. In this research, experimental temperature profiles are compared to the model based ones to evaluate the numerical model’s validity. By employing the final prediction errors the results show a good agreement between model and profiles. From energy saving point of view, thermo-graphical images showed that the designed system has the ability to save 0.27–0.42 kWhth/m2/day, by decreasing the air conditioning inlet temperature between 4 and 6 °C in summer days. Integration of the proposed DSF system into the buildings in suitable conditions, would potentially provide a nation-wide electricity consumption reduction up to 4283039.4 MWh alongside with its positive environmental benefits during hot season.
Natural gas pressure drops in city gate stations, in the natural gas distribution network, and bypassing through throttle valves. On the other hand, sudden gas pressure drop causes extreme ...temperature drop. To prevent natural gas from being hydrated in city gate stations, a water bath heater is used, leading to heating natural gas before the pressure reduction stage.
The main consequence of this research is the consideration of the challenge of low thermal efficiency in water bath heaters and the high potential of flue gases, which leads to the preheating of the gas by heat loss recovery and consequently improving the energy performance of the whole system.
In this study, a heat pipe heat exchanger was laboratory designed and constructed by using the ε-NTU method. The heat exchanger performs to recover partly the waste energy of flue gas emitted to the environment through heat pipes. This has been investigated in several experiments, based on conducted studies, measured data from a city gate station during a year, and also corresponding the experimental results with real conditions. In addition, to determine energy saving in fuel consumption, the city gate stations process was simulated in HYSYS software and evaluated according to gas temperature in new conditions.
As major findings applying heat pipes reduces natural gas consumption by 510,132 SCM a year; it also annually prevents 756 tons of CO2 from being emitted off a city gate station.
•The challenge of low thermal efficiency in water bath heaters is considered.•A heat pipe heat exchanger was laboratory designed and constructed by using the ε-NTU method.•The heat exchanger performs to recover partly the waste energy of flue gas through heat pipes.•The results show that applying heat pipes reduces natural gas consumption by 510,132 SCM a year.•It also annually prevents 756 tons of CO2 from being emitted off a city gate station.
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