ABSTRACT
After the COVID-19 pandemic has spread throughout the world, many research institutions and industrial organizations are putting great efforts into producing environmentally friendly solutions for the transportation sector. This paper presents a newly developed combined solid oxide fuel cell system with a turbofan engine that can use five alternative fuels, such as dimethyl ether, methanol, hydrogen, methane, and ethanol, with different blending ratios to form five fuel blends. The proposed system is studied in this paper using exergoenvironmental analysis (which is known as environmental impact assessment by exergy) in order to quantify and evaluate the environmental impact. The combined turbofan has an exergetic efficiency of 82%, with total fuel and product exergy rates of 905 and 743 MW, respectively. The total environmental impact caused by emissions and exergy destructions has a range of 4000 to 9000 Pt/h for all the fuel blends. The specific exergoenvironmental impact values of electricity production vary from about 3 to 8 mPt/MJ for solid oxide fuel cells and 10 to 25 mPt/MJ for the three turbines. The exergoenvironmental impact of the thrust force is a minimum of 34 Pt/(h.kN) for the RF1 fuel and a maximum of 87 Pt/(h.kN) for the RF4 fuel. © 2022
ABSTRACT
Economic crises face a new foe worldwide, along with the fact that the Kingdom of Saudi Arabia (KSA) is facing problems to sustain its role in international energy prospects due to unavoidable domestic challenges caused by a fast-growing population. The challenges are unemployment for the youngsters, two-thirds of the total population, and emerging demand for energy consumption at the domestic level at unsustainably high rates. Besides this, KSA spends a considerable amount, around 9% of the GDP, to subsidize the energy sectors (oil products and electricity). All these aspects call for a selective study to pinpoint the factors which can directly or indirectly influence to sustain the Saudi economy in the long run. To help cater to the growing demand for rigorous study on areas for energy rationalization in the Qassim region, the objectives of this work are to perform a thorough study of energy and exergy analysis of various electrical household appliances and exergy analysis of the residential sector (RS). In this study, an independent survey of 100 dwellings was conducted to collect data related to essential parameters of residential energy consumption. The collected data has been analyzed to determine energy consumption indicators and perform exergy analysis. The average monthly and yearly energy consumption per dwelling was between 30,832 to 36,166, and 1500 to 4500kWh, respectively. The average hourly electrical energy consumption during the working days was 4.12kWh, and during the curfew due to the Coronavirus (COVID-19) 4kWh. The breakdown of this end-use of residential energy is mainly distributed for air conditioning, water heating, lighting, and all other domestic appliances with 67.34%, 9.31%, 8.18%, and 15.17%, respectively. The calculated total energy efficiency of 142.9% for KSA in this study showed a significant discrepancy compared to the previously reported value of 77.52%. Calculated total exergy efficiency falls between 11.13% and 11.38% for the Qassim region. Energy policymakers can use clear energy consumption indicators and exergy efficiency present in this study. They can help to establish energy efficiency standards to be used for various economic sectors. © 2022 THE AUTHORS
ABSTRACT
Solar Air Heater (SAH) technology as a drying method for agricultural commodities is only active during the day and is highly dependent on the weather. Therefore, this study aims to investigate the effect of SAH coupled with phase change material (PCM) types of paraffin wax, soy wax, and palm wax as store energy materials to enhance the performance of conventional SAH. The PCM containers placed in the SAH are ex-bottles of milk cans which are numerous in the country due to the increase in consumption of milk by the people as an immunity enhancer during the Covid-19 pandemic. This is expected to improve the 3R (Reduce, Reuse, Recycle) strategy implemented to reduce environmental pollution. The tests conducted showed that the three types of PCM effectively improved the performance of SAH in drying agricultural commodities. The highest energy efficiency was achieved with paraffin at 30 %, 23.28 %, and 33.67 % while the highest exergy efficiency was achieved with palm wax at 20.27 %, 18.86 %, and 28.96 %, in three days respectively at different solar irradiation conditions.
ABSTRACT
After the COVID-19 pandemic has spread throughout the world, many research institutions and industrial organizations are putting great efforts into producing environmentally friendly solutions for the transportation sector. This paper presents a newly developed combined solid oxide fuel cell with a turbofan engine that can use five alternative fuels, such as dimethyl ether, methanol, hydrogen, methane, and ethanol, with different blending ratios to form five fuel blends. The proposed system is studied in this paper using exergoenvironmental analysis (which is known as environmental impact assessment by exergy) in order to quantify and evaluate the environmental impact. The combined turbofan has an exergetic efficiency of 82%, with total fuel and product exergy rates of 905 and 743 MW, respectively. The total environmental impact due to emissions and exergy destruction has a range of 4000 to 9000 Pt/h for all the fuel blends. The specific exergoenvironmental impact values of electricity production vary from about 3 to 8 mPt/MJ for solid oxide fuel cells and 10 to 25 mPt/MJ for three turbines. The exergoenvironmental impact of thrust force is a minimum of 34 Pt/(h.kN) for RF1 and a maximum of 87 Pt/(h.kN) for RF4.
ABSTRACT
With increasing energy use and outbreaks of respiratory infectious diseases (such as COVID-19) in buildings, there is a growing interest in creating healthy and energy-efficient indoor environments. A novel heating system named low-temperature radiant floor coupled with intermittent stratum ventilation (LTR-ISV) is proposed in this study. Thermal performance, indoor air quality, energy and exergy performance were investigated and compared with conventional radiant floor heating (CRFH) and conventional radiant floor heating with mixing ventilation (CRFH + MV). The results indicated that LTR-ISV had a more uniform operative temperature distribution and overall thermal sensation, and air mixing was enhanced without generating additional draft sensation. Compared with CRFH and CRFH + MV, the indoor CO2 concentration in LTR-ISV can be reduced by 1355 ppm and 400 ppm, respectively. Airborne transmission risk can also be reduced by 5.35 times. The coefficient of performance for CRFH, CRFH + MV, and LTR-ISV during working hours was 4.2, 2.5, and 3.4, respectively. The lower value of LTR-ISV was due to the high energy usage of the primary air handing unit. In the non-working hours, LTR-ISV was 0.6 and 1.3 higher compared to CRFH and CRFH + MV, respectively. The exergy efficiency of LTR-ISV, CRFH, and CRFH + MV was 81.77 %, 76.43 %, and 64.71 %, respectively. Therefore, the LTR-ISV system can meet the requirements of high indoor air quality and thermal comfort and provides a reference for the energy-saving use of low-grade energy in space heating.
ABSTRACT
The pressing global challenges, including global warming and climate change, the Russia-Ukraine war, and the Covid-19 pandemic, all are indicative of the necessity of a transition from fossil-based systems toward bioenergy and bioproduct to ensure our plans for sustainable development. Such a transition, however, should be thoroughly engineered, considering the sustainability of the different elements of these systems. Advanced sustainability tools are instrumental in realizing this important objective. The present work critically reviews these tools, including techno-economic, life cycle assessment, emergy, energy, and exergy analyses, within the context of the bioenergy and bioproduct systems. The principles behind these methods are briefly explained, and then their pros and cons in designing, analyzing, and optimizing bioenergy and bioproduct systems are highlighted. Overall, it can be concluded that despite the promises held by these tools, they cannot be regarded as perfect solutions to address all the issues involved in realizing bioenergy and bioproduct systems, and integration of these tools can provide more reliable and accurate results than single approaches. © 2022 BRTeam. All rights reserved.
ABSTRACT
Because of the significant public concern regarding climate change (and global warming), greenhouse gas (GHG) emissions have been successfully employed to communicate environmental impacts. This study develops a life cycle assessment of the equipment and energy flows of a combined cooling, heating and power system, expressing the environmental impacts as GHG emissions. Environmental data was used as input to an exergoenvironmental assessment based on the SPECO methodology. The GHG emissions associated with the consumption of natural gas and grid electricity are 0.258 and 0.227 kg CO2-eq/kWh, respectively. The internal combustion engine is responsible for the highest share of GHG emissions (15.95 kg CO2-eq/h), of which 15.80 kg CO2-eq/h is due to the formation of pollutants and the remainder refers to equipment. From the combined analysis of exergoenvironmental parameters, strategies that increase energy use and decrease irreversibilities should focus on the absorber heat exchanger, the steam generator, and heat recovery unit. Some of the recent energy policy responses to the COVID-19 crisis include the deployment of energy solutions such as combined energy systems, and exergoenvironmental assessments can promote the adoption of these more efficient systems.
ABSTRACT
Economic crises face a new foe worldwide, along with the fact that the Kingdom of Saudi Arabia (KSA) is facing problems to sustain its role in international energy prospects due to unavoidable domestic challenges caused by a fast-growing population. The challenges are unemployment for the youngsters, two-thirds of the total population, and emerging demand for energy consumption at the domestic level at unsustainably high rates. Besides this, KSA spends a considerable amount, around 9% of the GDP, to subsidize the energy sectors (oil products and electricity). All these aspects call for a selective study to pinpoint the factors which can directly or indirectly influence to sustain the Saudi economy in the long run. To help cater to the growing demand for rigorous study on areas for energy rationalization in the Qassim region, the objectives of this work are to perform a thorough study of energy and exergy analysis of various electrical household appliances and exergy analysis of the residential sector (RS). In this study, an independent survey of 100 dwellings was conducted to collect data related to essential parameters of residential energy consumption. The collected data has been analyzed to determine energy consumption indicators and perform exergy analysis. The average monthly and yearly energy consumption per dwelling was between 30,832 to 36,166, and 1500 to 4500kWh, respectively. The average hourly electrical energy consumption during the working days was 4.12kWh, and during the curfew due to the Coronavirus (COVID-19) 4kWh. The breakdown of this end-use of residential energy is mainly distributed for air conditioning, water heating, lighting, and all other domestic appliances with 67.34%, 9.31%, 8.18%, and 15.17%, respectively. The calculated total energy efficiency of 142.9% for KSA in this study showed a significant discrepancy compared to the previously reported value of 77.52%. Calculated total exergy efficiency falls between 11.13% and 11.38% for the Qassim region. Energy policymakers can use clear energy consumption indicators and exergy efficiency present in this study. They can help to establish energy efficiency standards to be used for various economic sectors.
ABSTRACT
The paper contains a response to the comment by Popovich and Mincheva, focusing on the different meanings of the analysis according to the First and the Second law of thermodynamics and their complementary and never alternative nature.
ABSTRACT
Considering a simple regenerative Brayton cycle, the impact of using different fuel blends containing a variable volumetric percentage of hydrogen in methane was analysed. Due to the potential of hydrogen combustion in gas turbines to reduce the overall CO2 emissions and the dependency on natural gas, further research is needed to understand the impact on the overall thermodynamic cycle. For that purpose, a qualitative thermodynamic analysis was carried out to assess the exergetic and energetic efficiencies of the cycle as well as the irreversibilities associated to a subsystem. A single step reaction was considered in the hypothesis of complete combustion of a generic H2/CH4 mixture, where the volumetric H2 percentage was represented by fH2, which was varied from 0 to 1, defining the amount of hydrogen in the fuel mixture. Energy and entropy balances were solved through the Engineering Equation Solver (EES) code. Results showed that global exergetic and energetic efficiencies increased by 5% and 2%, respectively, varying fH2 from 0 to 1. Higher hydrogen percentages resulted in lower exergy destruction in the chamber despite the higher air-excess levels. It was also observed that higher values of fH2 led to lower fuel mass flow rates in the chamber, showing that hydrogen can still be competitive even though its cost per unit mass is twice that of natural gas.
ABSTRACT
The use of Stirling-cycle-based heat pumps in high-temperature applications and waste heat recovery at an industrial scale is of increasing interest due to the promising role in producing thermal energy with zero CO2 emissions. This paper analyzes one such technology as developed by Olvondo Technology and installed at the pharmaceutical company AstraZeneca in Sweden. In this application, the heat pump used roughly equal amounts of waste heat and electricity and generated 500 kW of steam at 10 bar. To develop and widen the use of a high-performance high-temperature heat pump that is both economically and environmentally viable and attractive, various analysis tools such as exergy analysis and life cycle assessment (LCA) can be combined. The total cumulative exergy loss (TCExL) method used in this study determines total exergy losses caused throughout the life cycle of the heat pump. Moreover, an LCA study using SimaPro was conducted, which provides insight into the different emissions and the overall environmental footprint resulting from the construction, operation (for example, 1, 8, and 15 years), and decommissioning phases of the heat pump. The combined results were compared with those of a fossil fuel oil boiler (OB), a bio-oil boiler (BOB), a natural gas-fired boiler (NGB), and a biogas boiler (BGB).
ABSTRACT
According to the second law of thermodynamics, all human activities cause exergy destructions, adding to additional root causes for carbon dioxide emissions responsibility. It means that current carbon dioxide concentrations are accurately observed, but the root causes and their potential solutions against global warming fall short of achieving the goals of the Paris agreement by almost 45% in terms of decarbonization efforts, as shown in this paper. This result applies to all activities, including the green facility concept. In this respect, the primary aim of this paper is to raise awareness about the essence of the Second Law of Thermodynamics in expanding the green facility concept to reach more effective and sustainable rating methodologies concerning the climate crisis. A new evaluating and rating model with a set of exergy-based green building metrics that relate additional carbon dioxide emissions to irreversible exergy destructions has been developed. Examples about apparently green buildings according to the First Law of Thermodynamics are given by showing that these buildings are not green due to additional carbon dioxide emissions responsibility due to exergy destructions. An airport terminal building case is elaborated. It has been shown that although part of the electricity comes from a third-party wind energy provider, it ends up with carbon dioxide emissions responsibility because it is not entirely used in exergy-rational demand points and compares less favorably with an on-site cogeneration system using natural gas by about 30% more emissions responsibility. The results and derivations of new metrics are discussed, which shed light on adding new criteria to existing green building certification programs.