Society exergy analysis: a comparison of different societies

Data from exergy analyses for a number of different countries found in the literature are compared and the differences are discussed. In studies of Sweden, Ghana, Japan, Italy and Norway, the exergy in material flows had been considered, in addition to the flows of energy carriers. In other studies, the use of energy carriers was analyzed for the USA, Finland, Canada, Brazil, Turkey, the Organization for Economic Co-operation and Development (OECD) countries and the World. The exergy of material flows in these societies was estimated. The total annual exergy input per capita to the societies ranged over one order of magnitude. The total exergy efficiency varied from approximately 0.1 to 0.3, whereas the end-use exergy efficiency in general was slightly higher. It was found that different investigators had made somewhat different assumptions on exergy efficiencies in specific sectors, and these assumptions are discussed. However, the structure of the energy system appeared to be more important for the total exergy efficiency than the assumptions on the sectors. In particular, the residential–commercial sector represents major irreversibilities in many societies. In countries where electricity from thermal power plants has a significant contribution to the end use, this also caused large irreversibilities. Finally, the method of society exergy analysis is discussed. It is pointed out that, because of structural dissimilarities, different countries should be compared with care. However, the development within each society can be evaluated using exergy analyses. Furthermore, such analyses can be used as a means to increase the awareness of the notion of energy quality and degradation.     

End-use energy utilization efficiency of Nigerian residential sector

In this paper, the end-use efficiencies of the different energy carriers and the overall energy efficiency in the Nigerian residential sector (NRS) were estimated using energy and exergy analysis. The energy and exergy flows were considered from 2006 to 2011. The overall energy efficiency ranges from 19.15% in 2006 to 20.19% in 2011 with a mean of (19.96±0.23)% while the overall exergy efficiency ranges from 4.34% in 2006 to 4.40% in 2011 with a mean of (4.31±0.059)%. The energy and exergy efficiency margin was 15.58% with a marginal improvement of 0.07% and 0.02%, respectively when compared with previous results. The contribution of the energy carriers to the total energy and exergy inputs were 1.45% and 1.43% for electricity, 1.95% and 3% for fossil fuel and 96.6% and 95.57% for bio-fuel. The result shows that approximately 65% of the residence use wood and biomass for domestic cooking and heating, and only a fraction of the residence have access to electricity. LPG was found to be the most efficient while kerosene, charcoal, wood and other biomass the least in this order. Electricity utilization exergy efficiency is affected by vapor-compression air conditioning application apart from low potential energy applications. In addition, this paper has suggested alternatives in the end-use application and has demonstrated the relevance of exergy analysis in enhancing sustainable energy policies and management and improved integration techniques.     

Assessment of the energy utilization efficiency in the Turkish transportation sector between 2000 and 2020 using energy and exergy analysis method

Energy and exergy utilization efficiencies in the Turkish transportation sector over the period from 2000 to 2020 are evaluated in this study. A comparison of the overall energy and exergy efficiencies of the Turkish transportation sector with the other countries is also presented. Energy and exergy analyses are performed for four transport modes, namely roadway, railway, airway and seaway, while they are based on the actual data for 2000 and projected data for 2020. Roadway appears to be the most efficient mode when compared with railway, air and seaway. It is projected that about 15% of total energy resources will be used in this sector during 2020. The energy utilization efficiencies for the Turkish transportation sector range from 23.71% in 2000 to 28.75% in 2020, while the exergy utilization efficiencies vary from 23.65% to 28.85% in the same years, respectively. Exergetic improvement potential for this sector is estimated to be 700 PJ in 2020, with an average increase rate of 4.5% annually between 2000 and 2020. Road transport and oil-fuelled combustion engines offer the principal scope for exergetic improvement in the coming decades. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral energy and exergy utilization to determine how efficiently energy and exergy are used in the sector studied. It is also expected that this study will be helpful in developing highly applicable and productive planning for energy policies.     

Estimating the energy and exergy utilization efficiencies for the residential–commercial sector: an application

The main objectives in carrying out the present study are twofold, namely to estimate the energy and exergy utilization efficiencies for the residential–commercial sector and to compare those of various countries with each other. In this regard, Turkey is given as an illustrative example with its latest figures in 2002 since the data related to the following years are still being processed. Total energy and exergy inputs in this year are calculated to be 3257.20 and 3212.42 PJ, respectively. Annual fuel consumptions in space heating, water heating and cooking activities as well as electrical energy uses by appliances are also determined. The energy and exergy utilization efficiency values for the Turkish residential–commercial sector are obtained to be 55.58% and 9.33%, respectively. Besides this, Turkey's overall energy and exergy utilization efficiencies are found to be 46.02% and 24.99%, respectively. The present study clearly indicates the necessity of the planned studies toward increasing exergy utilization efficiencies in the sector studied.     

Exergy analysis of the energy use in Greece

In this work, an analysis is being done on the concept of energy and exergy utilization and an application to the residential and industrial sector of Greece. The energy and exergy flows over the period from 1990 to 2004 were taken into consideration. This period was chosen based on the data reliability. The energy and exergy efficiencies are calculated for the residential and industrial sectors and compared to the findings of a previous study concerning the exergy efficiency of the Greek transport sector. The residential energy and exergy efficiencies for the year 2003 were 22.36% and 20.92%, respectively, whereas the industrial energy and exergy efficiencies for the same year were 53.72% and 51.34%, respectively. The analysis of energy and exergy utilization determines the efficiency of the economy as a whole. The results can play an important role in the establishment of efficiency standards of the energy use in various economy sectors. These standards could be utilized by energy policy makers.     

Energy analysis and exergy utilization in the transportation sector of Jordan

The transport sector is responsible for about 37% of total final energy demand in Jordan, and thus it is considered an important driver for determining future national energy needs. This paper presents energy analysis and exergy utilization in the transportation sector of Jordan by considering the sectoral energy and exergy flows for the last two decades. The transportation sector, in Jordan, is a two-mode system, namely, road, which covers almost all domestic passenger and freight transport and airways. The latter is mainly used for international flights. The average estimated overall energy and exergy efficiencies were found as 23.2% and 22.8%, respectively. This simply indicates that there is large potential for improvement and efficiency enhancement. It is believed that the present technique is practical and useful for analyzing sectoral energy and exergy utilization to determine how efficiently energy and exergy are used in the transportation sector. It is also helpful to establish standards, based on exergy, to facilitate applications in different planning processes such as energy planning. A comparison with other countries showed that energy and exergy efficiencies of the Jordanian transport sector are slightly lower than that of Turkey, and higher than those incurred in Malaysia, Saudi Arabia and Norway. Such difference is inevitable due to dissimilar structure of the transport sector in these countries.     

Energy,exergy, and extended-exergy analysis of the Norwegian society 2000

The extraction, conversion, and use of energy carriers and materials in the Norwegian society in 2000 were investigated by Sciubba's method of extended-exergy accounting (EEA). In this method, extended-exergy (EE) values are assigned to labor and capital fluxes in addition to thermomechanical and chemical exergy values. The interchange of resources and products was quantified in terms of energy and exergy between seven sectors of the society and between the sectors and other countries. The extraction of resources from the environment and the discharge and deposit of waste were also included in the analysis. In the extraction sector, the exergy and EE conversion efficiencies both were 95%, and in the conversion sector both were approximately 76%. These two sectors are, respectively, dominated by oil and gas extraction and hydropower conversion. The third sector—agriculture, forestry, the fisheries, and food industry—had a lower exergy output to input ratio, 45%, whereas the EE conversion efficiency was 62%. A fourth sector, manufacturing industry, was dominated by paper, metal, and also chemical industry, and the efficiencies were 50 and 69%, respectively. In the transportation and service sectors, the labor and capital fluxes dominated the EEA, giving EE efficiencies of 63 and 75%, respectively, whereas the exergy efficiencies were 19 and 26%, respectively. In the seventh sector, the domestic sector (i.e. households), there was a close to zero energy and exergy output in this approach, since no products or resources were transferred to the other sectors except waste for re-circulation. However, the EE output of this sector was greater than the input, since labor is supplied from this sector to the other sectors.     

Assessment of the Turkish utility sector through energy and exergy analyses

The present study deals with evaluating the utility sector in terms of energetic and exergetic aspects. In this regard, energy and exergy utilization efficiencies in the Turkish utility sector over a wide range of period from 1990 to 2004 are assessed in this study. Energy and exergy analyses are performed for eight power plant modes, while they are based on the actual data over the period studied. Sectoral energy and exergy analyses are conducted to study the variations of energy and exergy efficiencies for each power plants throughout the years, and overall energy and exergy efficiencies are compared for these power plants. The energy utilization efficiencies for the overall Turkish utility sector range from 32.64% to 45.69%, while the exergy utilization efficiencies vary from 32.20% to 46.81% in the analyzed years. Exergetic improvement potential for this sector are also determined to be 332 PJ in 2004. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral and subsectoral energy and exergy utilization to determine how efficient energy and exergy are used in the sector studied. It is also expected that the results of this study will be helpful in developing highly applicable and productive planning for energy policies.     

A review and assessment of the energy utilization efficiency in the Turkish industrial sector using energy and exergy analysis method

Exergy has been seen a key component for a sustainable society, and in the recent years exergy analysis has been widely used in the design, simulation and performance evaluation of thermal and thermo chemical systems. A particular thermo dynamical system is the society of a country, while the energy utilization of a country can be assessed using exergy analysis to gain insights into its efficiency and potential for improvements.Energy and exergy utilization efficiencies in the Turkish industrial sector (TIS) over the period from 1990 to 2003 are reviewed and evaluated in this study. Energy and exergy analyses are performed for eight industrial modes, namely iron–steel, chemical–petrochemical, petrochemical–feedstock, cement, fertilizer, sugar, non-metal industry, other industry, while in the analysis the actual data are used. Sectoral energy and exergy analyses are conducted to study the variations of energy and exergy efficiencies for each subsector throughout the years studied, and these heating and overall energy and exergy efficiencies are compared for the eight subsectors. The chemical and petrochemical subsector, and the iron and steel subsector appear to be the most energy and exergy efficient sectors, respectively. The energy utilization efficiencies for the Turkish overall industrial sector range from 63.45% to 70.11%, while the exergy utilization efficiencies vary from 29.72% to 33.23% in the analyzed years. Exergetic improvement potential for this sector is also determined to be 681 PJ in 2003, with an average increase rate of 9.5% annually for the analyzed years. It may be concluded that the methodology used in this study is practical and useful for analyzing sectoral and subsectoral energy and exergy utilization to determine how efficient energy and exergy are used in the sector studied. It is also expected that this study will be helpful in developing highly applicable and productive planning for energy policies.     

Modelling the energy and exergy utilisation of the Mexican non-domestic sector: A study by climatic regions

This paper presents the development of a bottom-up stock model to perform a holistic energy study of the Mexican non-domestic sector. The current energy and exergy flows are shown based on a categorisation by climatic regions with the aim of understanding the impact of local characteristics on regional efficiencies. Due to the limited data currently available, the study is supported by the development of a detailed archetype-based stock model using EnergyPlus as a first law analysis tool combined with an existing exergy analysis method. Twenty-one reference models were created to estimate the electric and gas use in the sector. The results indicate that sectoral energy and exergy annual input are 95.37 PJ and 94.28 PJ, respectively. Regional exergy efficiencies were found to be 17.8%, 16.6% and 23.2% for the hot-dry, hot-humid and temperate climates, respectively. The study concludes that significant potential for improvements still exists, especially in the cases of space conditioning, lighting, refrigeration, and cooking where most exergy destructions occur. Additionally, this work highlights that the method described may be further used to study the impact of large-scale refurbishments and promote national regulations and standards for sustainable buildings that takes into consideration energy and exergy indicators.     

An application of energy and exergy analysis in residential sector of Malaysia

In this paper, the useful concept of energy and exergy utilization is defined, analyzed and applied to the residential sector of Malaysia by taking into account the energy and exergy flows for a period of 8 years from the year 1997 to 2004. The energy and exergy efficiencies are determined for the devices used in this sector and found to be 70% and 28%, respectively. Energy and exergy flow diagrams for the overall efficiencies of Malaysian residential sector are also illustrated in this paper. It is found that the current methodology applied in Saudi Arabia is suitable to analyze energy and exergy use in Malaysian residential sector. It has been found that the exergy efficiency of the Malaysian residential sector appears to be much lower than its corresponding energy efficiency. It has been observed that about 21% of total exergy losses are caused by refrigerator-freezer and 12% of total loss is caused by air conditioner. Washing machine, fan and rice cooker contribute about 11%, 10% and 8% of total exergy losses, respectively.     

Energy and exergy efficiencies in the Chinese transportation sector, 1980-2009

This paper aims at analyzing energy and exergy efficiencies in the Chinese transportation sector. Historical data is used to investigate the development of efficiencies from 1980 to 2009. Firstly, we calculate energy consumption values in PJ (petajoule) for nine transportation modes of five transportation sub-sectors. Then, the weighted energy and exergy efficiencies for each transportation mode, calculated by multiplying weighting factors with efficiency values of that mode, are summed up to calculate the weighted mean overall efficiencies for a particular year. We find that: (1) In 2009, the energy consumed in transportation sector was 12179.80 PJ, whereas that was 589.25 PJ in 1980. (2) Highways transport was the biggest energy consumer, which consumed 82.0% of total transport energy consumption in 2009. (3) Up to 2009, the oil consumed by transportation accounted for 75.1% of that in the whole country, which is more than the net oil import. (4) The average overall energy and exergy efficiencies are found to be 21.22% and 19.95%, respectively. (5) A comparison with other countries showed that energy and exergy efficiencies of the Chinese transportation sector are slightly lower than those of Jordan, Malaysian, Saudi Arabian and Norwegian, and higher than that incurred in Turkish.     

An application of energy and exergy analysis in agricultural sector of Malaysia

Thermodynamic losses usually take place in machineries used for agricultural activities. Therefore, it is important to identify and quantify the losses in order to devise strategies or policies to reduce them. An exergy analysis is a tool that can identify the losses occurred in any sector. In this study, an analysis has been carried out to estimate energy and exergy consumption of the agricultural sector in Malaysia. Energy and exergy efficiencies have been determined for the devices used in the agricultural sector of Malaysia, where petrol, diesel and fuel oil are used to run the machineries. Energy and exergy flow diagrams for the overall efficiencies of Malaysian agricultural sector are presented as well. The average overall energy and exergy efficiencies of this sector were found to be 22% and 20.728%, respectively, within the period from 1991 to 2009. These figures were found to be lower than those of Norway but higher than Turkey.     

An estimation of the energy and exergy efficiencies for the energy resources consumption in the transportation sector in Malaysia

The purpose of this work is to apply the useful energy and exergy analysis models for different modes of transport in Malaysia and to compare the result with a few countries. In this paper, energy and exergy efficiencies of the various sub-sectors are presented by considering the energy and exergy flows from 1995 to 2003. Respective flow diagrams to find the overall energy and exergy efficiencies of Malaysian transportation sector are also presented. The estimated overall energy efficiency ranges from 22.74% (1999) to 22.98% (1998) with a mean of 22.82±0.06%$22.82\pm 0.06\%$ and that of overall exergy efficiency ranges from 22.44% (2000) to 22.82% (1998) with a mean of 22.55±0.12%$22.55\pm 0.12\%$. The results are compared with respect to present energy and exergy efficiencies in each sub-sector. The transportation sector used about 40% of the total energy consumed in 2002. Therefore, it is important to identify the energy and exergy flows and the pertinent losses. The road sub-sector has appeared to be the most efficient one compared to the air and marine sub-sectors. Also found that the energy and exergy efficiencies of Malaysian transportation sector are lower than that of Turkey but higher than Norway.     

Energy and exergy utilization in agricultural sector of Saudi Arabia

This paper presents an analysis of energy and exergy utilization in the agricultural sector of Saudi Arabia by considering the sectoral energy and exergy flows for a period of 12 years between 1990 and 2001. Energy and exergy analyses are conducted for its two essential devices, namely tractors and pumps, and hence the sectoral energy and exergy efficiencies are obtained for comparison for a period of 12 years. Two main energy sources are diesel for tractors and electricity for pumps in the sector. It is found that the overall exergy efficiencies in this sector are slightly less than the corresponding energy efficiencies, e.g. 74.19–69.20% for exergy efficiency and 74.94–74.60% for energy efficiency from 1990 to 2001. The present technique is proposed as a useful tool in sectoral analysis of energy and exergy utilization, developing energy policies and providing energy conservation measures.     

Energy and exergy efficiencies in Turkish transportation sector, 1988–2004

This study aims at examining energy and exergy efficiencies in Turkish transportation sector. Unlike the previous studies, historical data is used to investigate the development of efficiencies of 17 years period from 1988 to 2004. The energy consumption values in tons-of-oil equivalent for eight transport modes of four transportation subsectors of the Turkish transportation sector, including hard coal, lignite, oil, and electricity for railways, oil for seaways and airways, and oil and natural gas for highways, are used. The weighted mean energy and exergy efficiencies are calculated for each mode of transport by multiplying weighting factors with efficiency values of that mode. They are then summed up to calculate the weighted mean overall efficiencies for a particular year. Although the energy and exergy efficiencies in Turkish transport sector are slightly improved from 1988 to 2004, the historical pattern is cyclic. The energy efficieny is found to range from 22.16% (2002) to 22.62% (1998 and 2004) with a mean of 22.42±0.14% and exergy efficiency to range from 22.39% (2002) to 22.85% (1998 and 2004) with a mean of 22.65±0.15%. Overall energy and exergy efficiencies of the transport sector consist mostly of energy and exergy efficiencies of the highways subsector in percentages varying from 81.5% in 2004 to 91.7% in 2002. The rest of them are consisted of other subsectors such as railways, seaways, and airways. The overall efficiency patterns are basically controlled by the fuel consumption in airways in spite of this subsector's consisting only a small fraction of total. The major reasons for this are that airways efficiencies and the rate of change in fuel consumption in airways are greater than those of the others. This study shows that airway transportation should be increased to improve the energy and exergy efficiencies of the Turkish transport sectors. However, it should also be noted that no innovations and other advances in transport technologies are included in the calculations. The future studies including such details will certainly help energy analysts and policy makers more than our study.     

Energy and exergy utilization efficiencies in the Japanese residential/commercial sectors

Unlike the manufacturing sector, the residential/commercial sectors of Japan struggle to meet their environmental requirements. For instance, their CO₂ emission levels have increased tremendously since 1990. This research estimates energy and ‘exergy (available energy)’ efficiencies in Japan's residential/commercial sectors during the period 1990–2006. Since an exergy analysis reveals ‘available energy losses’, it is an effective tool to achieve sustainable societies. The primary objective of this paper is to examine the potential for advancing the ‘true’ energy efficiency in Japan's residential/commercial sectors—by observing energy and exergy efficiency disparities. The results show large differences between the overall energy and exergy efficiencies in the residential (60.12%, 6.33%)/commercial sectors (51.78%, 5.74%) in 2006. This implies great potential for energy savings in both sectors. Furthermore, this research suggests that the residential sector may face more difficulties than the commercial sector, although the latter appears to be less energy-efficient, according to recent statistics. This is because the disparity between energy and exergy efficiencies has expanded in the residential sector since 2000. This study illustrates the importance of exergy analyses in promoting sustainable energy policies and new adaptation strategies.     

Assessment of the energy and exergy utilization efficiencies in the Turkish agricultural sector

This study deals with evaluating the energy and exergy utilization efficiencies in the Turkish agricultural sector over a 12‐year period from 1990 to 2001. In the energy and exergy analyses, two main energy sources, namely fuels and electricity, are taken into consideration, while the sectoral energy and exergy efficiencies are compared for this period. These main energy sources include diesel for tractors and other vehicles, and electricity for pumps. Overall energy utilization efficiencies are obtained to vary between 29.1 and 41.1%, while overall exergy utilization efficiencies are found to range from 27.9 to 37.4% in the analysed years, respectively. It may be concluded that the present technique proposed here may be used as a useful tool in analysing and evaluating the energy and exergy utilization efficiencies, identifying energy efficiency and/or energy conservation opportunities and dictating the energy strategies of countries. Copyright © 2005 John Wiley & Sons, Ltd.     

Analysis of sectoral energy and exergy use of Saudi Arabia

This paper presents the analysis of sectoral energy and exergy utilization of Saudi Arabia by considering the energy and exergy flows for the 12 years between 1990 and 2001. Sectoral energy and exergy efficiencies are obtained for the subsectors and the devices used in each sector. Energy and exergy flow diagrams for Saudi Arabia are also presented, respectively, to illustrate the situation on how energy and exergy efficiencies vary in each sector. The residential sector appears to be the most energy efficient sector, and the industrial sector to be the most exergy efficient. It is believed that the current methodology is useful for analyzing sectoral energy and exergy utilization, which will help Saudi Arabia with energy savings through energy efficiency and/or energy conservation measures. It is also be helpful to establish standards to facilitate application in various sectors and processes for a sustainable energy planning. Copyright © 2004 John Wiley & Sons, Ltd.     

Energy and exergy analyses of energy consumptions in the industrial sector in South Africa

The energy-utilization over a 10-year period (1994–2003) has been analysed for the South African industrial sector, which consumes more primary energy than any other sector of the economy. Four principal sub-sectors, namely iron and steel, chemical and petrochemical, mining and quarrying, and non-ferrous metals/non-metallic minerals were considered in this study. Primary-energy utilization data were used to calculate the weighted mean energy and exergy efficiencies for the sub-sectors and then overall values for the industrial sector were obtained. The results indicate that exergy efficiency is considerably lower than energy efficiency in all the sub-sectors, particularly in mining and quarrying processes, for which the values were approximately 83% and 16%, respectively. The performance of exergy utilization in the industrial sector can be improved by introducing various conservation strategies. Results from this study were compared with those for other countries.