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[en] Highlights: • Designing a waste heat recovery system based on a Rankine cycle in order to power production. • Energy and exergy analyses of the designed cycle in details. • Optimizing the recovery boiler pressure. - Abstract: The cement industry is one of the largest industries with regard to energy consumption. In the current study, the waste heat from the chimneys of Sabzevar cement factory was used to generate power with the use of the steam cycle in order to improve the energy efficiency. The results revealed that the increase in the boiler pressure decreased the total amount of the recovered energy due to the increase in the final temperature of the exhaust gases. But, the steam cycle efficiency was increased. Therefore, there would be an optimum pressure for the recovery boiler based on the energy and exergy analyses. Accordingly, the maximum exergy absorption from the waste heat of the chimneys of Sabzevar cement factory occurred at the pressure of 891.8 kPa. Considering the work consumption of air-cooled condenser fans, the maximum net power occurred at the recovery boiler pressure of 1398 kPa. The highest overall energy and exergy efficiencies also occurred at this pressure. Moreover, the effects of the important operating parameters, including the maximum cycle temperature, environmental temperature and condenser pressure on the optimum pressure were investigated. Results indicated that the boiler optimum pressure was independent from the operating parameters and remained constant, when these parameters changed.
[en] Highlights: • Chemical Looping Air Separation (CLAS) method used for oxygen production. • Copper-based CLAS system has lower energy consumptions than cryogenic air separation. • Efficiencies of oxy-combustion and gasification plants were improved by CLAS method. - Abstract: Chemical Looping Air Separation (CLAS) is a promising solution for energy efficient large scale oxygen production in comparison to the existing technologies (e.g. cryogenic air separation). This paper is evaluating the copper-based CLAS system used in conjunction with two power generation technologies based on coal oxy-combustion and gasification processes. Since the power generation sector is facing significant environmental constraints in term of reducing greenhouse gas emissions, the evaluated power plant concepts are equipped with carbon capture. As benchmark cases used to quantify the efficiency improvements as well as the CO2 capture energy penalty, similar power generation schemes with and without carbon capture were considered using cryogenic air separation as oxygen production method. Firstly, the assessment was concentrating on a CLAS system with 100 t/h oxygen output to assess the main issues (conceptual design, ancillary mass & energy consumptions, thermal integration) and then the system was scaled-up to match the oxygen consumption of large scale power plants with 400–500 MW net power output and 90% carbon capture rate. As the evaluations show, the CLAS system is increasing the net power efficiency by about 3 percentage points for the oxy-combustion plant and about 1.4 percentage points for the gasification plant.
[en] An increasing number of studies have analysed the scope for, and the barriers to, transitions toward sustainability in the context of developing countries building on analytical perspectives from the sustainability transitions literature. This paper introduces a special issue on sustainability transitions in developing countries, which takes stock of this emerging field of research and presents new empirical research that contributes to further advancement of our understanding of the conditions in which sustainability transitions are likely to take place in developing countries and what is involved in these transformative processes. This introductory paper presents the five papers contained in the special issue. The first paper comprises a review of the existing literature on the subject, and the other four papers present new empirical research. The key findings of the papers are discussed in relation to previous research in the field specifically related to four crosscutting themes: (i) global-local linkages and external dependencies; (ii) stability and non-stability of regimes; (iii) undemocratic and non-egalitarian nature of regimes; and (iv) nurturing the development of niches versus the execution of individual projects. The introductory paper concludes by presenting a research agenda, which aims to provide promising avenues for future research on sustainability transitions in developing countries.
[en] Highlights: • Environmental collaboration is championed as the solution to water problems. • We conducted an international systematic literature review of empirical studies. • 22 broad themes were found to influence the success and failure of effective collaboration. • Importance, agreement, and compatibility of the themes vary greatly. • More research is needed on how to prioritise different themes and the politics at play. - Abstract: Bold and inventive solutions are urgently needed to safeguard the future use of water. In response, collaborative-innovation is increasingly championed. If stakeholders including water utilities, supply-chain companies, research institutions and local communities work together, share their experiences and pool ideas, meaningful change could happen, it’s argued. But effective collaboration is far from easy. For every incentive that drives collaboration forward, another barrier blocks its path. Whilst the literature offers many possible factors that influence the success (or failure) of collaborative-innovations, it remains unclear which factors are most important, where the highest agreement and disagreement exists, and if accommodating one factor creates problems for another. This is important because its not always practical, nor necessary, to apply everything from the academic literature. In this paper, we report findings from an international systematic literature review that brings together a range of studies that cross the water collaboration and water innovation divide. We identify 22 broad themes that are spread (unevenly) across the entire collaborative-innovation process; highlight how the level of attention given to each theme varies greatly; and where disagreement exists. Our research provides practical insights on how to create more effective collaborative-innovations in water and where future research should be directed.
[en] Highlights: • Grasslands were contracted to individual households on the Qinghai-Tibetan Plateau. • Two distinct types of privately-owned grassland properties, the individually owned (IPP) and the jointly managed (JPP), developed. • The social, economic and ecological consequences of IPP and JPP were reviewed. • IPP can cause net losses. • JPP should be encouraged in this important socio-economic and environmentally-sensitive region. - Abstract: Land degradation neutrality (LDN) was introduced to provide a policy framework to achieve Sustainable Development Goal (SDG) 15. Land use policy and management changes can alter the status of land-based natural capital, and exert an influence on ecosystem functioning and interactions with a socio-ecological system. Over the last 30 years, continued efforts to maintain the socioeconomic sustainability of the Qinghai-Tibetan Plateau (QTP) led to the implementation of a unique ownership policy of individual households that were contracted to use defined grassland properties rather than collective nomadic practices. Two distinct types of privately-owned grassland properties now exist: individual private property (IPP) and jointly managed private property (JPP). The influence of IPP (vs. JPP) on grassland degradation has been the subject of a limited number of studies that are reviewed in this paper to help estimate some baseline indicator values for LDN on the QTP. Grasslands under IPP were more degraded according to soil and vegetation measurements, which were indicative of excessive vegetation removal and trampling due to grazing pressure. This pressure occurred because livestock mobility was limited by the imposed restrictions of fencing. A review of the associated socioeconomic status of this practice suggests that the disruption of social networks by the imposition of property lines between individual households acted to limit cultural transmission and collective benefits, such as the sharing of labour, pasture and food. Moreover, IPP seemed to lack the necessary resilience that is required to support the communities and their livestock. Although studies in the QTP are relatively scarce, research suggests that the notion that grassland contracts would address the region’s social, economic and environmental problems should be revisited because there is a significant difference in LDN indicator values for IPP and JPP, and evidence of significant degradation in the decades before the 2015 baseline when the UNCCD adopted LDN and SDGs. Evidence suggests that JPP is a more resilient system, capturing the environmental benefits of nomadism and the socioeconomic benefits of land contracts. Given that some of the grasslands are already contracted to individual households, creative JPP property arrangements should be respected. A reconsideration of whether the not-yet-contracted grasslands should be contracted individually rather than jointly, is required if LDN is to be achieved on the QTP by 2030. If the current policy is maintained, research evidence suggests that JPP should be encouraged, and policy makers should seek better ways of ensuring long-term sustainability and that LDN is achieved to maintain the natural capital and associated ecosystem services of the QTP.
[en] Highlights: • Modeling and simulation of various sCO2 power cycle was conducted. • Thermodynamic result of individual power cycle was compared via enthalpy distribution diagram. • LCOE on individual power cycle was calculated by total revenue requirement. - Abstract: The supercritical CO2 Brayton power cycle is well known as a promising power generation technology, and researches for applying it to various applications are being actively carried out. In this study, performance analysis of coal-fired power plant combined with supercritical CO2 Brayton power cycle was performed. If various existing supercritical CO2 Brayton power generation cycles are applied to coal-fired power generation systems, the expected power generation efficiency and levelized cost of electricity (LCOE) are thoroughly estimated. In conclusion, it is expected that the power generation efficiency is improved by 6.2–7.4% compared to the steam Rankine cycle applied to the existing coal-fired power plant, and the LCOE of the coal-fired power plant combined with the supercritical CO2 Brayton cycle is reduced by about 7.8–13.6% compared to that of coal-fired power plant combined with steam Rankine cycle. In addition, design criteria for retaining the economic dominance were presented through sensitivity analysis of factors affecting O&M cost and capital cost.
[en] Highlights: • Heat storages and electric boilers are best solutions for peak-load situations. • CCS technology is too immature, unreliable, costly, and has too large space demand. • Solar heat is unfavorable at Helsinki latitude due to bad coincidence with demand. • Multicriteria method was developed for treating conflicting experts’ preferences. - Abstract: Climate change mitigation requires reducing dependence on fossil fuels and transition to low carbon energy production technologies. Nearly half of the global final energy consumption is thermal energy produced from technologies with high carbon dioxide emission. As such, it is imperative to employ carbon-neutral heat production to achieve a sustainable energy system. This paper presents a real-life case of applying multicriteria decision analysis for evaluating carbon-neutral heat-only production technologies in a major district heating system in Finland. A group of 10 experts from the energy company contributed in defining the alternative technologies and multiple economic, technological, and environmental evaluation criteria. The experts also provided the criteria measurements and preference information for different criteria. The alternatives were compared using Stochastic Multicriteria Acceptability Analysis (SMAA). SMAA is a simulation based method for decision problems where different kind of uncertain information is represented by probability distributions. Because the preferences of the experts were highly conflicting, the SMAA method was extended within this study to treat conflicting preferences. The most preferred alternatives were short-term heat storages and electric boilers based on renewable power. These alternatives may be considered attractive future solutions particularly in balancing peak load heat consumption and production.
[en] Highlights: • The proposed system efficiently produces exportable upgraded coal and electricity. • Energy efficiency of the proposed highly-integrated system reaches 79.6%. • Equivalent energy conversion ratio for lignite upgrading soars to 100.8%. • Produced upgraded coal is more economical for energy transmission in China. - Abstract: Effective upgrading for efficient utilisation of lignite is of great significance for countries that highly dependent on coal for power generation. This work proposed and evaluated an integrated system for lignite upgrading and utilisation using pre-drying, low-temperature oxidative pyrolysis (LTOP) and power generation, beneficially converting lignite into an exportable thermal coal while generating power locally. In the proposed system, LTOP was adopted to upgrade lignite, and the pre-drying process would reduce the moisture content of lignite prior to LTOP and boiler using steam bleeds from the conjunct steam turbine, saving a part of reaction heat consumed by moisture evaporation. The energy of raw syngas produced in LTOP process was efficiently utilised by co-combusting with a portion of pre-dried lignite in boiler, and the sensible heat of upgraded coal was recovered by preheating the feed/condensate water of steam turbine unit. With the developed models and process simulation, the mass and energy balance of the proposed integrated system for upgrading Zhundong lignite (ZD) in conjunction with a 600 MW supercritical electric power plant were determined. Detailed thermodynamic analysis showed that the proposed system produces annually 1.66 million tonnes of exportable upgraded coal with lower heating value (LHV) of 29.45 MJ/kg, as well as 3118.5 GWh electricity, with overall energy efficiency at 79.6% and the ratio of produced electricity over the energy of upgrade coal product at 22.9%. As a considerable technical route for long-distance energy transportation, economics of deploying the proposed systems in north-western China and exporting the upgraded coal (TR-I) to the eastern seaboard over a distance of 3000 km was quantified, and compared with the option of adopting ultra-high voltage (UHV) electric power transmission (TR-II). It was shown that, the overall CAPEX of TR-I is ∼59% less than that of TR-II and the gross cost of electricity (COE) of TR-I is ₵5.20/kWh, also much lower than that of the TR-II.
[en] Highlights: • Subentry electricity consumption is considered for campus building benchmarks. • New methods of electricity benchmarking for complex campus buildings are proposed. • A rating system is established based on new benchmarks. - Abstract: Publicising the energy consumption of buildings is an effective way to promote building energy efficiency in colleges and universities. The aim of this study is to propose a method for developing electricity benchmarks for complex campus buildings. This study uses various statistical methods to determine such benchmarks. The determination of new electricity benchmarks includes the following steps: (a) determination of the factors influencing electricity consumption, (b) standardisation of indicators, and (c) calculation and correction of the electricity benchmarks. Thirteen complex buildings from the hot summer and cold winter zone of China were selected as samples to illustrate the standardisation process. The total electricity and subentry electricity benchmarks are determined based on multiple linear regression analyses. Multi-factor analyses of variance were used to identify the categorical factors that have significant influences on electricity consumption and on the correction of benchmarks. Finally, a rating system for the evaluation of electricity consumption was also established that applied the corrected electricity benchmarks.
[en] Highlights: • AHPs are reexamined in this paper using a time-weighted bin temperature analysis. • The COP is strongly dictated by the evaporator temperature and the glide of the working fluid. • The actual AHP performance may vary considerably depending on ammonia purity. • It is concluded that deployment of AHPs may be restricted geographically. • In many regions of the U.S, AHPs may significantly underperform baseline technology. - Abstract: Natural gas-driven absorption heat pumps (AHPs) are under renewed scrutiny as a viable technology for space conditioning and water heating for residential and commercial applications because of natural gas production trends, pricing, and the speculation that it might be a “bridge fuel” in the global transition toward energy sustainability. Since any level of natural gas combustion contributes to atmospheric carbon dioxide accumulation, the merits of natural gas–consuming absorption technology are reexamined in this paper from the point of view of expected efficiency as a driver for AHPs throughout the United States using a time-weighted bin temperature analysis. Such analyses are necessary because equipment standards for rated performance are restricted to one set ambient condition; whereas in actual practice, the AHP must perform over a considerably wider range of external conditions in which its efficiency may be vastly different from that at the rated condition. Quantification of variations in efficiency and system performance is imperative to address how to provide the desired application with the least environmental impact. In this paper, we examine limiting features in AHPs and relate them to systemic performances in 16 cities across all 8 climate zones in the United States, each containing 15 bin temperatures. The results indicate that the true expectation for AHP performance is significantly less than what might be optimized for the rated condition. Statistical measures of the variation in water heating COPs show that for most cities, the COP at the rated conditions is outside the 95% Confidence Interval. It is concluded that deployment of AHP water heaters may be restricted geographically by outdoor temperature constraints.