Multi-objective optimization of steam power plants for sustainable generation of electricity

A unified framework that combines process simulation and multi-objective optimization is presented to simultaneously maximize the annual profit, while minimizing environmental impact (i.e., greenhouse gas emissions) of steam power plants with fixed flowsheet structures. The proposed methodology includes the selection of suitable primary energy sources (i.e., fossil fuels, biomass, biofuels, and solar energy) for sustainable electricity generation. For solving the problem of optimal selection of energy sources, a linear model is developed and included within a highly nonlinear simulation model for the parameter optimization of steam power plants that is solved by using genetic algorithms. This approach is robust and avoids making discrete decisions. Life cycle assessment technique is used to quantify the greenhouse gas emissions resulting from different combinations of energy sources and operating conditions of the power plants. The thermodynamic properties for liquid water and steam are calculated rigorously using the IAPWS-IF 97 formulation. An example problem of an advanced regenerative-reheat steam power plant is presented to illustrate the proposed method, which provides the Pareto optimal solutions, the types and amounts of primary energy sources as well as the optimal values of the operating conditions of the plant that simultaneously maximize the profit while minimizing environmental impact.     

The Efficiency of Different Technologies for the Preparation and Use of Wet Fuel in Power Engineering

We consider the possible technical solutions for the treatment moisture fuel from the standpoint of such general problems as a reduction in greenhouse gas emissions and lowering fuel costs with increased energy generation. The use of the biofuels, which is almost always highly wet, does solve these problems in perspective, but it results in an urgent problem regarding an increase of the energy efficiency of the suitable technologies. The practice shows that a reduction in the costs of fuel and energy production currently takes place with generation based on the cheap brown coal (lignite); however, it is necessary to increase qualitatively the efficiency of power plants in order to reduce fuel consumption, as well as atmospheric emissions. We consider the use of complex technologies of moisture fuel preparation for its efficient application via intensive drying with subsequent gasification in order to pass to the combined cycles with the gas turbines. A new technology for intensive energy-saving drying using superheated pressurized steam is presented. We present an analysis and comparison of the means of such approach to implementation and substantiate the selection of the optimal solutions, which are applicable not only to power engineering but also elsewhere in the utilization of moisture combustible materials and waste products.     

Life cycle assessment of membrane-based carbon capture and storage

Many investigations have conducted life cycle assessments (LCA) of the most commonly discussed routes of carbon capture and storage (CCS): post-combustion with amine wash separation; oxyfuel using cryogenic air separation and pre-combustion by integrated gasification combined cycle (IGCC) using physical separation. A research alliance developed corresponding separation systems using different types of membranes to allow a more energy efficient separation process: polyactive polymeric membranes for post-combustion, ceramic membranes for oxyfuel and metallic membranes for IGCC separation. By conducting an LCA, the study examines the actual greenhouse gas emissions and other environmental impacts of the new membrane separation technologies, together with concepts implementing the more common technologies. The reference systems represent today’s state-of-the-art supercritical coal fired power plant in Germany, together with a more advanced ultra-supercritical plant operating at 700 °C without CO₂ capture. The results demonstrate that among the three reference power plants the IGCC is the superior concept due to the highest efficiency. Regarding climate change, the IGCC power plants with CO₂ capture are still the best concepts. When other environmental impacts are considered, the capture technologies are inferior. The membrane concepts show the overall better results in comparison to the conventional capture technologies. The environmental impacts for membrane applications add a new range of findings to the field of CCS LCAs. Now the results for several different approaches can be compared directly for the first time.     

Choice of Life Cycle Assessment Software Can Impact Packaging System Decisions

A number of software packages are available that are designed to facilitate making environmental comparisons between different packaging options, to facilitate ‘green’ packaging design and assessment of the environmental aspect of sustainability. Some of these (e.g. SimaPro and GaBi) are full‐fledged ISO 14040/14044‐compliant programs for life cycle assessment (LCA). Others are more limited, but are designed to be much simpler to use (e.g. COMPASS and Package Modeling). A systematic comparison of the evaluation of several packaging systems using COMPASS, SimaPro, GaBi, and Package Modeling found significant discrepancies in LCA results from different software systems. Availability of common impact categories among the software limited comparisons to four categories: greenhouse gas emissions, fossil fuel/non‐renewable energy, eutrophication, and water depletion. Given a common set of basic packaging containers as input, results from the LCA software systems being studied disagreed on which container had the greatest environmental impact, and in some cases results were more than an order of magnitude different between software. Discrepancies in results occurred in all four impact categories, and all four software systems disagreed with each other at multiple points in the comparisons. If there is to be increasing use of LCA analysis in guiding packaging design, this issue must be fully understood and resolved. Copyright © 2015 John Wiley & Sons, Ltd.     

生命周期内混合动力燃气热泵碳排放研究

采用生命周期评价的方法,针对一种混合动力燃气热泵系统在全生命周期的碳排放进行了评估。基于生命周期（LCA）评价理论,确定了系统边界,建立了系统生命周期内碳排放核算模型。得到了系统在生产阶段、运输安装阶段、运行阶段和回收利用阶段的碳排放当量。结果表明:系统在运行使用阶段CO2-eq排放量最大,为35387.6kg,大约占据了整个生命周期的84％,主要来源为电力和天然气的使用; 生产安装阶段CO2-eq排放量次之,约为6187kg,运输安装及废弃阶段碳排放量很小,几乎可以忽略。因此,要降低系统在全生命周期中的温室气体排放量,应重点放在对电力和天然气的合理使用和新能源的开发上。对比分析了其与单独电力驱动热泵在全生命周期内的碳排放量。分析结果表明:在全生命周期内,混合动力燃气热泵与单独电力驱动热泵相比碳减排量约为20430.9kg。最后,进一步讨论了系统的碳减排方法和减排潜力。     

城市区域碳排放测量反演研究国际进展

城市聚集了世界50%的人口和70%以上的碳排放,然而,每个城市的碳排放不确定度很大,50%～100%的数据误差是很常见的。对温室气体浓度的时空分布特征及碳排放测量反演的基本思路进行了介绍。目前美国国家标准与技术研究院（NIST）正在资助开展若干个城市/城市群碳排放测量试点项目,利用自上而下的方法,基于温室气体浓度测量和精确的城市尺度大气输移扩散模式,反演推算城市区域的碳排放通量。对NIST正在开展的研究进行了综述,并对中国计量科学研究院未来在该领域的工作进行了展望。     

生物质增强聚乙烯醇在食品包装领域的应用研究进展

目的 研究定制猫眼彩盒的生产对环境的影响,为此类型包装材料对环境的影响评估以及生产工艺改进提供参考。方法 采用生命周期评价(LCA)方法定性、定量分析其对环境(9个环境因素)的影响,在e-Footprint软件上,在线完成全部生命周期评价,包括建模、计算分析、数据质量评估和LCA结果发布。结果 该类型产品对初级能源消耗、水资源消耗和气候变化的影响较大。每个彩盒消耗0.71 MJ初级能源和0.35 kg水,排放0.05 kg影响气候变化的气体。其中,白卡纸和定制猫眼膜的初级能源消耗占比分别为37%和35%,水资源消耗的79%来自白卡纸生产,影响气候变化气体的排放占比分别为29%和25%。结论 通过优化白卡纸和定制猫眼膜材料、结构以及生产工艺流程,可降低定制猫眼彩盒的能源消耗(含初级能源和水资源),减少温室效应气体的排放。     

Impact of including land-use change emissions from biofuels on meeting GHG emissions reduction targets: the example of Ireland

The greenhouse gases (GHG) emissions from land-use change are of particular concern for land-based biofuels. Emissions avoided by substituting fossil fuels with biofuels may be offset by emissions from direct and indirect land-use changes (LUC). There is an urgent need to investigate what impact land-use change emissions may have on the expansion of bioenergy and biofuels, in the context of EU mitigation policies. This paper focuses on Ireland, which faces a number of challenges in delivering its renewable energy and GHG reduction targets. The Irish TIMES energy systems model was used to assess the impact of a range of land-use change emissions’ levels on the evolution of Ireland’s low-carbon energy system. A reference scenario was developed where LUC is ignored and Ireland achieves a least-cost low-carbon energy system by 2050. If high indirect land-use change (ILUC) emissions are included, this results in a decrease by 30 % in bioenergy and a 68 % increase in marginal abatement costs by 2050. Hydrogen is used instead of bioenergy in the freight sector in this scenario, while private cars are fuelled by renewable electricity. If GHG emissions from ILUC were considered less severe, indigenous grass biomethane becomes the key biofuel representing 31 % of total bioenergy consumption. This is in line with recent research in Ireland of the key role that grass biomethane can play.     

Accounting for indirect land-use change in the life cycle assessment of biofuel supply chains

The expansion of land used for crop production causes variable direct and indirect greenhouse gas emissions, and other economic, social and environmental effects. We analyse the use of life cycle analysis (LCA) for estimating the carbon intensity of biofuel production from indirect land-use change (ILUC). Two approaches are critiqued: direct, attributional life cycle analysis and consequential life cycle analysis (CLCA). A proposed hybrid ‘combined model’ of the two approaches for ILUC analysis relies on first defining the system boundary of the resulting full LCA. Choices are then made as to the modelling methodology (economic equilibrium or cause–effect), data inputs, land area analysis, carbon stock accounting and uncertainty analysis to be included. We conclude that CLCA is applicable for estimating the historic emissions from ILUC, although improvements to the hybrid approach proposed, coupled with regular updating, are required, and uncertainly values must be adequately represented; however, the scope and the depth of the expansion of the system boundaries required for CLCA remain controversial. In addition, robust prediction, monitoring and accounting frameworks for the dynamic and highly uncertain nature of future crop yields and the effectiveness of policies to reduce deforestation and encourage afforestation remain elusive. Finally, establishing compatible and comparable accounting frameworks for ILUC between the USA, the European Union, South East Asia, Africa, Brazil and other major biofuel trading blocs is urgently needed if substantial distortions between these markets, which would reduce its application in policy outcomes, are to be avoided.     

规范空调排空方法，减少温室气体排放

空调器安装过程中采用自力排空的方法，会有氟里昂制冷剂排放到大气中，加剧了温室效应，给人类生存的自然环境造成破坏。建议有关部门尽快采取必要的措施，禁止空调安装过程中采用自力排空的方法，强制执行真空泵抽空排气，减少温室气体的排放。     

Carbon neutral hydrocarbons

Reducing greenhouse gas emissions from the transportation sector may be the most difficult aspect of climate change mitigation. We suggest that carbon neutral hydrocarbons (CNHCs) offer an alternative pathway for deep emission cuts that complement the use of decarbonized energy carriers. Such fuels are synthesized from atmospheric carbon dioxide (CO2) and carbon neutral hydrogen. The result is a liquid fuel compatible with the existing transportation infrastructure and therefore capable of a gradual deployment with minimum supply disruption. Capturing the atmospheric CO2 can be accomplished using biomass or industrial methods referred to as air capture. The viability of biomass fuels is strongly dependent on the environmental impacts of biomass production. Strong constraints on land use may favour the use of air capture. We conclude that CNHCs may be a viable alternative to hydrogen or conventional biofuels and warrant a comparable level of research effort and support.     

Sustainability evaluation framework for building cooling systems: a comparative study of snow storage and conventional chiller systems

In Canada, the residential building sector consumes 17 % of the total energy and 15 % of the total greenhouse gas emissions. In particular, the energy demand for cooling in the residential sector is increasing due to the large occupancy floor area and high usage of air conditioning. Minimizing energy use and greenhouse gas emissions is one of the highest priority goals set for national energy management strategies in developed countries including Canada. In this study, a framework based on the life cycle assessment approach is developed to assess the environmental impacts of different building cooling systems, namely conventional snow storage system, watertight snow storage system, high-density snow storage system, and the conventional chiller cooling system. Moreover, all these systems have varying energy requirements and associated environmental impacts during different phases (extraction and construction, utilization, and end of life) of the life cycle of a building. A low-rise residential building in Kelowna (BC, Canada) has been selected for the pragmatic application of the proposed framework. The annual cooling energy demand for the building is estimated for different phases. Subsequently, the life cycle impact assessment has been carried out using SimaPro 8.1 software and TRACI 2.1 method. For sustainability evaluation of different cooling systems over their life cycle, multi-criteria decision analysis has been employed using the ‘Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE II).’ The results showed that the snow storage systems tend to reduce greenhouse gas emissions and associated environmental impacts more than the conventional system.     

An algebraic targeting approach for effective utilization of biomass in combined heat and power systems through process integration

Green house gases (GHGs) pose some of the most profound impact on the environment. One viable alternative for reducing GHGs is the utilization of biomass to generate heat and power for processing facilities. The purpose of this paper is to address the utilization of biowaste or biomass source in a processing facility for combined heat and power (CHP). In particular, the paper addresses the following questions: How to incorporate biomass utilization in cofiring and energy production within an existing process? How to reconcile thermal demands with opportunities for power cogeneration through a process-integration framework? What are the economic factors that will insure the feasibility of biomass utilization and power cogeneration? What is the impact on GHG emissions and what are the necessary GHG emission pricing options? A systematic algebraic procedure for targeting cogeneration potential ahead of detailed power generation network design is presented. The approach presented here effectively utilizes biomass and biowaste sources as external fuel, and matches them with the use and dispatch of fuel sources within the process, heating and non-heating steam demands, and power generation. The concept of extractable power introduced by Harell and El-Halwagi AIChE Spring Meeting, New Orleans, March (2003) has been used as a basis of constructing this algebraic cogeneration targeting approach. Steam surpluses and deficits are identified by header balance. Flow balance is performed by cascade diagram techniques and extractable power is computed from net flows to target the cogeneration potential. Next, the paper discusses important economic factors (e.g., GHG pricing options) required for the cost-effective utilization of sole biomass feed or a co-fed mixture of biomass and fossil fuels for CHP. Two case studies are discussed to illustrate the presented approach. The first case study illustrates the developed targeting approach when no external fuel is required and all the higher pressure surplus streams are able to satisfy the lower pressure deficit headers. The second case shows the application of algebraic targeting to obtain the external fuel requirement when surplus headers are not able to meet the deficit demands. Further, this case shows the use of biomass for meeting the demands and the subsequent effects on economics and GHG emissions for the process.     

Rethinking investment planning and optimizing net zero emission buildings

Increased awareness of climate change has precipitated more stringent mitigation targets. Public sector institutions in Canada are committed to becoming carbon neutral to attain a leadership position in climate change mitigation-related initiatives. Recent statistics reveal that buildings account for the majority of the corporate carbon footprint of public sector institutions. Hence, there is an increasing interest towards developing net zero energy and net zero emission buildings to comply with climate action targets. With limited financial resources, public sector institutions must optimize investments into building energy retrofits by considering lifecycle cost (LCC), overall energy performance, and related greenhouse gas (GHG) emission. The aim of this paper is to develop an investment planning approach for net zero emission buildings (NZEB). First, an investment planning approach for NZEB is proposed. A typical recreational centre building in British Columbia, Canada, was used as the archetype to demonstrate the concept. Second, innovative and proven building energy retrofits were analysed using energy simulation software to assess the impact on energy consumption reduction, GHG emissions, and LCC. Third, impacts of geographical location, tariff regimes, and grid emission factors on energy retrofits were studied by locating the same building in other provinces of Canada. This study revealed that net zero energy investment has a strong correlation to the grid emission factor. The proposed approach in this paper will assist building managers and owners in retrofitting and budget planning.     

Optimal planning for the supply chain of biofuels for aviation in Mexico

There are great challenges to replace fossil fuels by biofuels, including the development of efficient technologies and adequate strategic planning. For the manufacture of biofuels at the industrial scale, there is a need to optimize the overall associated supply chain. Among biofuels, the global market for the aviation biofuel has increased drastically, mainly due to the forecasted growth of the aviation sector. Nevertheless, the supply chain for the aviation biofuel has specific characteristics, which are different from the case of bioethanol and biodiesel. Therefore, this paper presents a general optimization approach for optimizing the supply chain of aviation biofuels. A case study is presented accounting for the projection of the Mexican government for implementing the use of aviation biofuel in the airport network. The application of the proposed approach generates very interesting solutions, which are grouped in a Pareto front; from these results, it can be highlighted that the demand for aviation biofuel in the Mexican market can be satisfied with a gross economic benefit of M US$ 1681 per year, and savings of 93% of carbon dioxide emissions. The generated information can contribute to the establishment of the sustainable supply chain for aviation biofuels in Mexico.     

The effect of greenhouse gas policy on the design and scheduling of biodiesel plants with multiple feedstocks

With the increasing attention to the environmental impact of discharging greenhouses gases, there has been a growing public pressure to reduce the carbon footprint associated with the use of fossil fuels. In this context, one of the key strategies is the substitution of fossil fuels with biofuels such as biodiesel. The design of biodiesel production facilities has traditionally been carried out based on technical and economic criteria. Greenhouse gas (GHG) policies (e.g., carbon tax, subsidy) have the potential to significantly alter the design of these facilities, the selection of the feedstocks, and the scheduling of multiple feedstocks. The objective of this article is to develop a systematic approach to the design and scheduling of biodiesel production processes while accounting for the effect of GHG policies in addition to the technical, economic, and environmental aspects. An optimization formulation is developed to maximize the profit of the process subject to flowsheet synthesis and performance modeling equations. Furthermore, the carbon footprint is accounted for with the help of a life cycle analysis (LCA). The objective function includes a term which reflects the impact of the LCA of a feedstock and its processing to biodiesel. A multiperiod approach is used to discretize the decision-making horizon into time periods. During each period, decisions are made on the type and flowrate of the feedstocks, as well as the associated design and operating variables. A case study is solved with several scenarios of feedstocks and GHG policies.     

Design of biorefinery systems for conversion of corn stover into biofuels using a biorefinery engineering framework

Unlocking the potential and value of lignocellulosic residues is an important step in making biorefineries economically and environmentally promising. This calls for a holistic and systematic approach in designing sustainable industrial systems. In this work, biorefinery systems via biochemical route (acetone–butanol–ethanol or ABE system) and thermochemical route (gasification and mixed alcohols or GMA system) for converting corn stover into biofuels have been designed using a Sustainable Engineering Framework. The framework involves eight main steps: (1) design problem definition, (2) data collection, (3) process synthesis and simulation, (4) process integration, (5) resource recovery from residues, (6) utility system design, (7) economic and environmental modelling and (8) economic value and environmental impact margin analysis for decision making. Consideration of resource recovery from biorefinery waste streams has proven to be the key in making biorefineries self-sustaining and with low environmental impacts. Simultaneous economic and environmental feasibility assessment at the early stage of process design is highly envisaged. The cost of biofuel production in the ABE system has been found to be 49.2 US$/GJ and 69.9 US$/GJ in the GMA system. The greenhouse gas emissions are 46.2 g CO₂-eq/GJ for ABE and 19.0 g CO₂-eq/GJ for GMA, lower than gasoline (85 g CO₂-eq/GJ). The GMA system is not economically compelling though with high environmental benefit, while the ABE system has shown to be both economically and environmentally feasible.     

Modelling and optimisation of biomass supply chains: a review

A growing number of researchers are attracted by the domain of bioenergies, due to the problems induced by greenhouse gas emissions and increasing energy demand. One possible way of producing biofuels in a renewable way is to use biomass, however the economic viability of a biorefinery system depends critically on the cost of its supplies. As biomass is not very expensive, logistics is responsible of an important fraction of this cost. Models and methods to optimise biomass supply chains are surveyed in this article, after introducing some technical terms and describing the main activities in these chains. This review aims to give a comprehensive overview of the research in this field with a focus on optimisation modelling issues and solution approaches. Recent advances in the current research and possible new directions are sketched.     

Costing climate change

Debate over how, when, and even whether man-made greenhouse-gas emissions should be controlled has grown in intensity even faster than the levels of greenhouse gas in our atmosphere. Many argue that the costs involved in reducing emissions outweigh the potential economic damage of human-induced climate change. Here, existing cost-benefit analyses of greenhouse-gas reduction policies are examined, with a view to establishing whether any such global reductions are currently worthwhile. Potential for, and cost of, cutting our own individual greenhouse-gas emissions is then assessed. I find that many abatement strategies are able to deliver significant emission reductions at little or no net cost. Additionally, I find that there is huge potential for individuals to simultaneously cut their own greenhouse-gas emissions and save money. I conclude that cuts in global greenhouse-gas emissions, such as those of the Kyoto Protocol, cannot be justifiably dismissed as posing too large an economic burden.     

Switchgrass as an alternate feedstock for power generation: an integrated environmental, energy and economic life-cycle assessment

An environmental biocomplexity analysis is done on the environmental, energy, economic and technological implications of using switchgrass (Panicum virgatum) to replace coal in power generation. We evaluate cost, environmental impact and net greenhouse gas emissions. In the analysis, alternatives for production and transport are considered. The analysis shows that the most effective technologies for switchgrass preparation are harvesting loose material for hauling and chopping and then compressing it into modules and transporting. The GHG emission mitigation is found to be substantial with the mitigation contribution under cofiring found to be greater per ton of switchgrass than for switchgrass fired alone. This paper also analyzes the implications of switchgrass use under alternative cofiring ratios, coal prices, hauling distances and per acre yields.