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.     

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.     

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.     

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 and exergy analysis at the utility and commercial sectors of Malaysia

In this paper, sectoral energy and exergy analysis model is applied to the utility and commercial sectors of Malaysia by considering the energy and exergy flows from 1990 to 2003. The energy and exergy efficiencies are determined for the sub-sectors and devices used in these two sectors. It has been found the hydroelectric power plant sub-sector is more energy and exergy efficient compared to the thermal power plant sub-sector. The energy and exergy efficiencies of utility and commercial sectors of Malaysia are compared with a few other countries around the world as well. The utility and commercial sectors of Malaysia are found to be more efficient than that of Thailand, Brunei, China, and Vietnam in 1999.     

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.     

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.     

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.     

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.     

An exergy analysis for cement industries: An overview

Cement production has been one of the most energy intensive industries in the world with energy typically accounting about 30-40% of the production costs. Reduction of the production cost is very much important. Therefore, many studies on the efficient use of energy were carried out in the past. Moreover, these studies, which are based on exergy analysis, focus on industrial applications only. This paper reviewed exergy analysis, exergy balance, and exergetic efficiencies for cement industry. It is found that the exergy efficiency for cement production units ranges from 18% to 49% as well as the exergy losses due to the irreversibility from kiln are higher than other units in cement production plant.     

An approach to the exergy analysis of photosynthesis

The present paper contributes to the classic thermodynamic analysis of photosynthesis. Photosynthesis is a complex endothermic process involving two kinds of matter; substance and radiation. This threefold study consists of: (1) an energy analysis (the energy conservation equation is developed to estimate the energy effects of the process); (2) entropy analysis (the changes of entropy are used to estimate the irreversibility of the component processes); and (3) exergy analysis (developed for thermodynamic evaluation of both kinds of matter). A simplified mathematical diffusive model of photosynthesis (controlled by diffusion of gases) is used to analyze key aspects of the problem. The corresponding terms of energy and exergy equations are compared and discussed. Photosynthesis is a highly irreversible process. In the calculation example the irreversibility loss is 97.4%. This increases slightly together with increasing temperatures of leaf and environment. On the contrary, the energy equation does not show any loss due to irreversibility.In the calculation example for the presented model, the exergy degree of perfection for photosynthesis is 2.61% and the energy degree of perfection is 35.4%. The rate of sugar production is 3.21 × 10⁻⁹ kmol m⁻² s⁻¹. Heat transferred to the environment by radiation and convection is respectively 6.4% and 65.3%. The exergies of the radiant and convective heat are 0.003% and zero, respectively. The impacts on several output parameters (e.g. leaf temperature, sugar rate, degrees of perfection, etc.) were determined: the effect of varying input conditions (e.g. environmental temperature and humidity, leaf absorptivity, intensity of solar radiation, coefficient of convective heat transfer, and CO₂ concentration). Some possibilities for further developing the exergy analysis are discussed.     

Understanding energy and exergy efficiencies for improved energy management in power plants

An extensive overview is provided of various energy- and exergy-based efficiencies used in the analysis of power cycles. Vapor and gas power cycles, cogeneration cycles and geothermal power cycles are examined, and consideration is given to different cycle designs. The many approaches that can be used to define efficiencies are provided and their implications discussed. Improvements of the management of energy in power plants that stem from understanding the efficiencies better are described. Examples are given to illustrate the efficiencies and their differences, with the results presented using combined energy and exergy diagrams. It is anticipated that the results will provide a convenient and practical tool for engineers and researchers dealing with the analysis, design, optimization and improvement of power cycles.     

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.     

An exergy analysis of a solar-driven ejector refrigeration system

Exergy analysis is used as a tool to analyse the performance of an ejector refrigeration cycle driven by solar energy. The analysis is based on the following conditions: a solar radiation of 700 W/m², an evaporator temperature of 10 °C, a cooling capacity of 5 kW, butane as the refrigerant in the refrigeration cycle and ambient temperature of 30 °C as the reference temperature. Irreversibilities occur among components and depend on the operating temperatures. The most significant losses in the system are in the solar collector and the ejector. The latter decreases inversely proportional to the evaporation temperature and dominates the total losses within the system. The optimum generating temperature for a specific evaporation temperature is obtained when the total losses in the system are minimized. For the above operating conditions, the optimum generating temperature is about 80 °C.     

An energy and exergy analysis of the supercritical water reforming of glycerol for power production

As a continuation of a previous work, a conceptual design is proposed for reforming glycerol using supercritical water to produce maximum electrical power in an energy self-sufficient system. The scheme of the process is simulated after discussing some routes to achieve the aim. The selected way takes advantage of the huge pressure energy of reformate products just at the outlet of the reforming process. The expanded product gas is used as a fuel gas to provide the thermal energy required by the reforming process. The evaluation of the thermodynamic performance of the process is carried out by an energy and exergy analysis. As relevant outputs measurements of the process performance, the net work and exergetic efficiencies as well as the mole fraction and molar flow-rates of hydrogen obtained. Glycerol feed concentration in aqueous solution at which no external heat source is needed was obtained, both for pure and pretreated crude glycerol, at 800 °C and 240 atm. The effect of the main operating parameters has been investigated by sensitivity analysis to identify optimal conditions that maximize power production. In the exergy analysis, the thermodynamic efficiencies used for the overall process and for its individual units are suitably discussed. The computation has been made with the aid of AspenPlus™, using the predictive Soave-Redlich-Kwong equation of state as thermodynamic method in the simulation of the supercritical region. The next study in this series of glycerol reforming using SCW will aim to maximize hydrogen production, including the syngas purification, to generate electricity via fuel cells.     

Exergy analysis of energy utilization in the transportation sector in China

As an emerging approach for unified resource accounting and energy-utilization assessment for the transportation sector, the exergy method to embody the second law of thermodynamics is investigated and applied to the energy-utilization assessment of the Chinese transport sector from 1978 to 2002. The exergy consumed by the sector in 2000 was 3.3 times that in 1978. The exergy of the oil consumed by transportation accounted for 30.5% of the total oil consumption in the whole country up to 2000, almost equal to the exergy of the net oil import. In terms of the exergy consumption intensity, taken as the exergy consumption per Converted Turnover, proposed to assess the overall effectiveness of the system, and conventional exergy efficiency to reflect the technical performance of involved transport vehicles, both the energy-utilization effectiveness and efficiency of the sector have been declining generally. Waterways transport was proved the most effective one, and railways, highways and civil aviation were the second, third and fourth, respectively. The historical evolution and structural variation of energy use in terms of the total exergy consumption, exergy efficiency and exergy consumption intensity are revealed and explored against drastic background transitions in related policies and socioeconomics.     

Discount rate for technology assessment: An application to the energy sector

When comparing the relative merits of technologies in the energy sector, analysis of a long time span is frequently required. Discounting of costs and benefits is usual in such analysis, and the choice of an appropriate discount rate can be vital. The available empirical evidence suggests that the appropriate real discount rate could vary widely depending on which concept it is based. For Australia, a value reflecting the social time preference rate could be as low as 2%, while one based on the social opportunity cost of capital would be considerably higher, probably 7–10%. A multiperiod linear programming model, MARKAL, suitable for energy technology assessment, was used to analyse the effect on the optimal long-term energy strategy for Australia, of using discount rates over the range 2–10%. The results indicate that capital-intensive technologies such as coal liquefaction and solar water heaters are disadvantaged when using high discount rates. This could result in energy strategies being pursued in which the level of oil imports is much     

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.     

An econometric study on long-term energy outlook and the implications of renewable energy utilization in Malaysia

We developed a comprehensive econometric model to study the long-term outlook of Malaysia's economy, energy and environment to 2030. Our projections under the reference scenario indicated that Malaysia's gross domestic production (GDP) is expected to average 4.6% from 2004 to 2030, and total primary energy consumption will triple by 2030. Coal import will increase following governmental policy of intensifying its use for power generation. Oil import is predicted to take place by 2013 and reach 45 Mtoe in 2030. Hence, in the near future, Malaysia's energy import dependency will rise. Carbon emissions will triple by 2030. On the other hand, our projections under an alternative renewable energy (RE) scenario showed that the utilization of RE is a strategic option to improve the long-term energy security and environmental performance of Malaysia. However, substantial governmental involvements and support, as well as the establishment of a regulatory framework are necessary.     

An empirical analysis of energy efficiency in China''s iron and steel sector

Using Malmquist Index Decomposition, this paper investigates energy efficiency of China's iron and steel sector during the period 1994–2003. Provincial panel data is employed, allowing various energy inputs and product outputs. The energy efficiency improvement is decomposed into two components: technical change (production frontier shifting effect) and technical efficiency change (catching up effect) over time. Our empirical results indicate that the energy efficiency in China's iron and steel sector increased by 60% between 1994 and 2003, which is mainly attributable to technical progress rather than technical efficiency improvement. The energy efficiency gaps among provincial iron and steel sectors during this period have widened. However, energy efficiency of iron and steel plants owned by the state has slowly improved in some regions, such as Shanghai, Liaoning, Beijing and Hubei. Nevertheless, technical efficiency in these four regions has decreased considerably. Energy efficiency in China's two largest private-own iron and steel bases (Heibei and Jiangsu) improved significantly.