Assessing the sustainability of the UK society using thermodynamic concepts: Part 2

By building on the first part of our analysis, this second part attempts to provide a further understanding of the UK society's metabolism, its impact and offer policy suggestions that could promote a shift towards sustainability. The methodologies employed in this second part include Exergy Analysis (EA) and Extended Exergy Analysis (EEA). Exergy inputs and outputs amounted to 17423.9 and 11888.7 PJ, respectively, with energy carries, mainly fossil fuels, being both the predominant inputs (15597.1 PJ) and outputs (5147.1 PJ). Exergy consumption and efficiency for various economic sectors and subsectors have been calculated with the residential and service sector showing the lowest exergy conversion efficiencies (11.2% and 12.3%, respectively) while certain industrial subsectors, such as the aluminium and iron/steel industries showed the highest exergy conversion factors (67.0 and 62.1%). Extended exergy efficiencies were somewhat different owing to the different calculation procedure. Extended exergy efficiencies were 91.4% for the extraction sector, 38.9% for the conversion sector, 49.1% for the agriculture sector, 31.5% for the transportation sector, 38.6% for the industrial sector and 80.0% for the tertiary sector.     

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.     

Performance and thermo-economic assessments of geothermal district heating system: A case study in Afyon,Turkey

In this study energy, exergy and exergoeconomic analysis of the Afyon geothermal district heating system (AGDHS) in Afyon, Turkey is performed through thermodynamic performances and thermo-economic assessments. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, exergy losses and loss cost rates. Energy and exergy losses throughout the AGDHS are quantified and illustrated in the flow diagram. The energy and exergy efficiencies of the overall system are found to be 37.59% and 47.54%, respectively. The largest exergy loss occurs in the heat exchangers with 14.59% and then in the reinjection wells with 14.09%. Besides, thermo-economic evaluations of the AGDHS are given in table. Energy and exergy loss rates for the AGDHS are estimated to be 5.36 kW/$ and 0.2  kW/$, respectively.     

Physical sustainability assessment for the China society: Exergy-based systems account for resources use and environmental emissions

As a physical assessment of the sustainability of the China society, presented in this paper is an exergy-based systems account for resources use and environmental emissions of the China society in 2006 as the most recent year with statistics availability. Exergy analysis is applied to elucidate the resources flows from the natural environment into the society, between other countries or regions and the society, between the sectors of the society, and the emissions outflows into the natural environment from different sectors. For the China society broken down into seven sectors (i.e., extraction, conversion, agriculture, industry, transportation, tertiary and households) as one of the most complicated cases, systems account of environmental emissions as greenhouse gases and “three wastes” is carried out for the first time, combined with an updated resources account. The total societal exergy consumption amounts to 101.1 EJ, of which 93.6% is due to resources use accounted as 94.6 EJ, of which 23.2% is by the industry sector, 22.8% by conversion, 20.4% by households, 12.3% by agriculture, 9.0% by tertiary, 6.9% by extraction and 5.4% by transport, and 6.4% due to environmental emissions accounted as 6481.6 PJ, including greenhouse gas emissions of 5706.1 PJ, with the highly remarkable fraction of 49.05% from CH₄ of the same importance as 50.91% from CO₂ and only 0.04% from N₂O, and “three wastes” emissions of only 775.5 PJ. The extraction sector is shown as the leading emitter with 32.6% of the total emissions, followed by the industry with 20.0%, agriculture with 17.3%, and conversion sector with 16.8%. To characterize the network performance in context of environmental resources from a systems ecological perspective, exergy-based ecological efficiency and resources conversion coefficient are found as 88.8% and 91.3% for the extraction sector, 29.0% and 30.0% for the conversion sector, 31.5% and 33.5% for the agriculture sector, 34.8% and 36.1% for the industry sector, 16.3% and 17.3% for the transportation sector, 38.4% and 38.5% for the tertiary sector, and only 1.3% and 1.3% for the households sector, respectively. Comparisons with other societies and with China society in previous years are made to further illustrate the physical sustainability of the societal system on the international and development horizons.     

A harmonized calculation model for transforming EU bottom-up energy efficiency indicators into empirical estimates of policy impacts

This study is an impact analysis of European Union (EU) energy efficiency policy that employs both top-down energy consumption data and bottom-up energy efficiency statistics or indicators. As such, it may be considered a contribution to the effort called for in the EU's 2006 Energy Services Directive (ESD) to develop a harmonized calculation model. Although this study does not estimate the realized savings from individual policy measures, it does provide estimates of realized energy savings for energy efficiency policy measures in aggregate. Using fixed effects panel models, the annual cumulative savings in 2011 of combined household and manufacturing sector electricity and natural gas usage attributed to EU energy efficiency policies since 2000 is estimated to be 1136 PJ; the savings attributed to energy efficiency policies since 2006 is estimated to be 807 PJ, or the equivalent of 5.6% of 2011 EU energy consumption. As well as its contribution to energy efficiency policy analysis, this study adds to the development of methods that can improve the quality of information provided by standardized energy efficiency and sustainable resource indexes.     

Thermal modeling of a packed bed thermal energy storage system during charging

The process of charging of an encapsulated ice thermal energy storage device (ITES) is thermally modeled here through heat transfer and thermodynamic analyses. In heat transfer analysis, two different temperature profile cases, with negligible radial and/or stream-wise conduction are investigated for comparison, and the temperature profiles for each case are analyzed in an illustrative example. After obtaining temperature profiles through heat transfer analysis, a comprehensive thermodynamic study of the system is conducted. In this regard, energy, thermal exergy and flow exergy efficiencies, internal and external irreversibilities corresponding to flow exergy, as well as charging times are investigated. The energy efficiencies are found to be more than 99%, whereas the thermal exergy efficiencies are found to vary between 40% and 93% for viable charging times. The flow exergy efficiency varies between 48% and 88% for the flows and inlet temperatures selected. For a flow rate of 0.00164 m³/s, the maximum flow exergy efficiency occurs with an inlet temperature of 269.7 K, corresponding to an efficiency of 84.3%. For the case where the flow rate is 0.0033 m³/s, the maximum flow exergy efficiency becomes 87.9% at an inlet temperature of 270.7 K. The results confirm the fact that energy analyses, and even thermal exergy analyses, may lead to some unrealistic efficiency values. This could prove troublesome for designers wishing to optimize performance. For this reason, the flow exergy model provides the most useful information for those wishing to improve performance and reduce losses in such ITES systems.     

Performance investigation of thermal energy storage system with Phase Change Material (PCM) for solar water heating application

In order to harvest solar energy, thermal energy storage (TES) system with Phase Change Material (PCM) has been receiving greater attention because of its large energy storage capacity and isothermal behavior during charging and discharging processes. In the present experimental study, shell and tube TES system using paraffin wax was used in a water heating system to analyze its performance for solar water heating application. Energy and exergy including their cost analyses for the TES system were performed. Accordingly, total life cycle cost was calculated for different flow rates of the Heat Transfer Fluid (HTF). With 0.033 kg/min and 0.167 kg/min flow rates of water as HTF, energy efficiencies experienced were 63.88% and 77.41%, respectively, but in exergy analysis, efficiencies were observed to be about 9.58% and 6.02%, respectively. Besides, the total life cycle cost was predicted to be $ 654.61 for 0.033 kg/min flow rate, which could be reduced to $ 609.22 by increasing the flow rate to 0.167 kg/min. Therefore it can be summarized that total life cycle cost decreases with the increase of flow rate.     

Exergy analysis of cogeneration power plants in sugar industries

In this paper, exergy analysis of a heat-matched bagasse-based cogeneration plant of a typical 2500 tcd sugar factory, using backpressure and extraction condensing steam turbine is presented. In the analysis, exergy methods in addition to the more conventional energy analyses, are employed to evaluate overall and component efficiencies and to identify and assess the thermodynamic losses. The analysis is carried out for a wide range of steam inlet conditions selected around the sugar industry’s export cogeneration plant. The results show that, at optimal steam inlet conditions of 61 bar and 475 °C, the backpressure steam turbine cogeneration plant perform with energy and exergy efficiency of 0.863 and 0.307 and condensing steam turbine plant perform with energy and exergy efficiency of 0.682 and 0.260, respectively. Boiler is the least efficient component and turbine is the most efficient component of the plant.     

The potential biomass for energy production in the Czech Republic

Biomass production is a promising alternative for the Czech Republic's (CZ) agricultural sector. Biomass could cover the domestic bio-energy demand of 250 PJ a⁻¹ (predicted for 2030), and could be exported as bio-fuels to other EU countries. This study assesses the CZ's biomass production potential on a regional level and provides cost–supply curves for biomass from energy crops and agricultural and forestry residues. Agricultural productivity and the amount of land available for energy crop production are key variables in determining biomass potentials. Six scenarios for 2030 with different crop-yield levels, feed conversion efficiencies and land allocation procedures were built. The demand for food and fodder production was derived from FAO predictions for 2030. Biomass potential in the CZ is mainly determined by the development of food and fodder crop yields because the amount of land available for energy crop production increases with increasing productivity of food and fodder crops. In most scenarios the NUTS-3 regions CZ020, 31 and 32 provided the most land for energy-crop production and the highest biomass potentials. About 110 PJ a⁻¹, mostly from agricultural and forestry residues, can be provided from biomass when the present Czech agricultural productivity is maintained. About 195 PJ a⁻¹ (105 PJ from energy crops) can be provided when production systems are optimised with regard to fertilizer regimes and 365 PJ a⁻¹ (290 PJ from energy crops) when the yield level of Dutch agriculture is reached. Costs for woody biomass decrease with increasing plantation yield and range between 2.58 and 4.76 € GJ⁻¹. It was concluded that Czech agriculture could provide enough biomass for domestic demand and for export if agricultural productivity is increased.     

Understanding energy systems change in Canada: 1. Decomposition of total energy intensity

Between 1995 and 2010, the total energy intensity (E/GDP, PJ/Gross Domestic Product in 2002$) of the Canadian economy declined by 23% or − 2.64 MJ/$. To understand why, the Logarithmic Mean Divisia Index (LMD-I) method was used to decompose a large body of government statistical data supporting the observed E/GDP decline. The analysis shows that (a) 48% (1.27 MJ/$) of the decline was associated with an inter-sector structural change in the economy (i.e. an increased contribution to the total GDP of the low energy-using commercial and institutional sector compared with the high energy-using manufacturing and heavy industry sectors); (b) 24% (0.62 MJ/$) was attributed to the impact of the Canadian GDP growing faster than population; (c) 22% (0.58 MJ/$) of the decline was associated with an overall decrease in business energy intensity. A deeper analysis of business sectors shows a positive impact of 0.4 MJ/$ from increased energy intensity in the oil and gas sector, offset by a 0.98 MJ/$ decline due to energy intensity declines in the other business sectors; (d) 6.3% (0.17 MJ/$) of the decline was associated with an improvement in the energy intensity of households, mostly from residential energy use rather than personal transportation energy use. These results provide insights for policy makers regarding those aspects of the Canadian economy that contribute to, or work against, efforts to transform energy systems toward sustainability.     

EUBIONET III—Solutions to biomass trade and market barriers

The EUBIONET III project has boosted (i) sustainable, transparent international biomass fuel trade, (ii) investments in best practice technologies and (iii) new services on biomass heat sector. Furthermore, it identified cost-efficient and value-adding use of biomass for energy and industry. The aims of this article are to provide a synthesis of the key results of this project. Estimated annual solid biomass potential in the EU-27 is almost 6600 PJ (157 Mtoe), of which 48% is currently utilised. The greatest potential for increased use lies in forest residues and herbaceous biomass. Trade barriers have been evaluated and some solutions suggested such as CN codes for wood pellets and price indexes for industrial wood pellets and wood chips. The analysis of wood pellet and wood chip prices revealed large difference amongst EU countries, but also that on the short term prices of woody and fossil fuels are barely correlated. Sustainable production and use of solid biomass are also deemed important by most European stakeholders, and many support the introduction of harmonised sustainability criteria, albeit under a number of preconditions. The study identified also that a number of woody and agro-industrial residue streams remain un- or underutilised. The estimated European total potential of agro-industrial sources is more than 250 PJ (7.2 Mtoe), the amount of unutilised woody biomass (the annual increment of growing stock) even amounts to 3150 PJ (75 Mtoe). Finally 35 case studies of biomass heating substituting fossil fuels were carried out, showing that the potential to reduce GHG emissions ranges between 90 and 98%, while costs are very similar to fossil fuel heating systems. Overall, we conclude that solid biomass is growing strongly, and is likely to heavily contribute to the EU renewable energy targets in the coming decade.     

Energy and exergy analyses of OMW solar drying process

The energy and exergy analyses of the drying process of olive mill wastewater (OMW) using an indirect type natural convection solar dryer are presented. Olive mill wastewater gets sufficiently dried at temperatures between 34 °C and 52 °C. During the experimental process, air relative humidity did not exceed 58%, and solar radiation ranged from 227 W/m² to 825 W/m². Drying air mass flow was maintained within the interval 0.036–0.042 kg/s. Under these experimental conditions, 2 days were needed to reduce the moisture content to approximately one-third of the original value, in particular from 3.153 g_water/g_{dry matter} down to 1.000 g_water/g_{dry matter}.Using the first law of thermodynamics, energy analysis was carried out to estimate the amounts of energy gained from solar air heater and the ratio of energy utilization of the drying chamber. Also, applying the second law, exergy analysis was developed to determine the type and magnitude of exergy losses during the solar drying process. It was found that exergy losses took place mainly during the second day, when the available energy was less used. The exergy losses varied from 0 kJ/kg to 0.125 kJ/kg for the first day, and between 0 kJ/kg and 0.168 kJ/kg for the second. The exergetic efficiencies of the drying chamber decreased as inlet temperature was increased, provided that exergy losses became more significant. In particular, they ranged from 53.24% to 100% during the first day, and from 34.40% to 100% during the second.     

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 use and carbon dioxide emissions from steel production in China

In 1996, China manufactured just over 100 Mt of steel and became the world's largest steel producer. Official Chinese energy consumption statistics for the steel industry include activities not directly associated with the production of steel, ‘double-count’ some coal-based energy consumption, and do not cover the entire Chinese steelmaking industry. In this paper, we make adjustements to the reported statistical data in order to provide energy use values for steel production in China that are comparable to statistics used internationally. We find that for 1996, official statistics need to be reduced by 1365 PJ to account for non-steel production activities and double-counting. Official statistics also need to be increased by 415 PJ in order to include steelmaking energy use of small plants not included in official statistics. This leads to an overall reduction of 950 PJ for steelmaking in China in 1996. Thus, the official final energy use value of 4018 PJ drops to 3067 PJ. In primary energy terms, the official primary energy use value of 4555 PJ is reduced to 3582 PJ when these adjustments are made.     

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 situation in Mozambique: A review

The need to increase energy security and promote development, especially in rural areas has forced many developing countries in southern Africa, like Mozambique to take several actions toward development of several infrastructures and legislations for production and use of liquid biofuels. The main objective of this study is to present the energy situation in Mozambique and assess the potential for energy generation from widely available renewable sources including residues from agricultural crops and forest industry. The country is endowed with great potential for biofuels, solar, hydro and wind energy production. The energy production today is, however, far from fulfilling energy needs of the country, and the majority of people are still not benefiting from these resources. The potential of total residues from agricultural sector and forest industry is estimated to be around 128 PJ. This amount of energy covers almost half of the combined production of charcoal and firewood which amounted to approximately 298 PJ in 2006. However, such amount of energy resources is wasted and is not visible on national energy statistics.     

Overall thermal energy and exergy analysis of hybrid photovoltaic thermal array

In this paper, overall thermal energy and exergy analysis has been carried out for different configurations of hybrid photovoltaic thermal (PVT) array. The hybrid PVT array (10.08 m × 2.16 m) is a series and parallel combinations of 36 numbers of PV modules. A one-dimensional transient model for hybrid PVT array has been developed using basic heat transfer equations. On the basis of this transient model, an attempt has been made to select an appropriate hybrid PVT array for different climatic conditions (Bangalore, Jodhpur, New Delhi, and Srinagar) of India. On the basis of high grade energy (i.e. overall exergy gain), case-III has been selected as the most appropriate configuration because overall exergy for case-III is 12.9% higher than case-II. The overall thermal energy and exergy gain for Bangalore is 4.54 × 10⁴ kW h and 2.07 × 10⁴ kW h respectively which is highest in comparison to the other cities.     

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.     

α–h Diagram and principle of exergy coupling of GAX cycle

Ammonia absorption chiller systems of a single-stage cycle and a Generator Absorber heat exchanger cycle (GAX) were simulated and studied. At heat source temperatures of T_H = 120 °C, T_M = 25 °C and T_L = 5 °C, the coefficient of performances of the two cycles are 0.589 and 0.776, the GAX cycle is higher 31.8% than the single-stage cycle. And the exergy efficiencies of the two cycles are 15.4% and 27.4%, the GAX cycle is higher up to 77.9%. This paper proposes a new method that adopts the energy quality factor α as a evaluation criterion and also uses the α–h diagram as a thermodynamic analysis tool graphically, and a concept that divides absorption cycle to a heat pump subcycle and a heat engine subcycle. By means of the α–h diagram, the thermodynamic frameworks of the two cycles were illustrated. The comparison analysis indicates that the improvement of cycle performance depends on its thermodynamic perfectibility. In fact, the exergy demand of heat pump subcycle in the GAX cycle is as the same as that of the single-stage cycle, however, the energy cascading use and the exergy coupling framework of the heat engine subcycle in GAX cycle is retrofitted, so that the exergy consumption is reduced and the increased benefit is obtained from the overall cycle.     

Energy and exergy of potato drying process via cyclone type dryer

This paper is concerned with the energy and exergy analyses of the single layer drying process of potato slices via a cyclone type dryer. Using the first law of thermodynamics, an energy analysis was performed to estimate the ratios of energy utilization. An exergy analysis was accomplished to determine the location, type and magnitude of the exergy losses during the drying process by applying the second law of thermodynamics. It was concluded that the exergy losses took place mostly in the 1st tray where the available energy was less utilized during the single layer drying process of potato slices. It is emphasized that the potato slices are sufficiently dried in the ranges between 60 and 80 °C and 20–10% relative humidity at 1 and 1.5 ms⁻¹ of drying air velocity during 10–12 h despite the exergy losses of 0–1.796 kJ s⁻¹.