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The operation of tidal pumping station has an energetic impact on energy course of massive water pumping for a long time. Thus, a multi-objective optimal operation model was developed to optimize the operation scheme and reduce the energy consumption of the tidal pumping station. In the model, a day is divided into several sub-periods according to the regulation of water level in tidal reach. The partition of sub-periods, the number and blade angle of operating units in each sub-period are adjusted to minimize daily operation energy consumption. And the less switching times, the better the reliability and durability of the unit, the lower the failure rate. Therefore, the reduction of wearing parts' service life is quantified for each switching time in the form of cost. A case study is performed with the tidal pumping station of the South-to-North Water Transfer Project in China. In this paper, energy consumption and switching times are quantified as costs respectively, and the result shows that the daily energy consumption could be saved about 2.28%–6.56%, and the switching times reduced at least 60%. Therefore, this paper could provide an effective optimal operation scheme for the tidal pumping station whose operation is affected by tides. [ABSTRACT FROM AUTHOR]

• A fault-tolerant gait for quadruped robots with 2 locked legs is designed. • The gait pattern is designed using the mobility analyzed by the G F set theory. • The trajectory planning method for the fault-tolerant gait is proposed. • Positive static stability margin can be satisfied all throughout the gait. • The gait allows the robot to walk omnidirectionally and adapt to rough terrains. Fault-tolerant gaits can give legged robots the ability to walk under fault conditions, and hence prolong the service life. However, for quadruped robots with two locked legs, fault-tolerant gaits can be rarely found. This paper proposes a novel fault-tolerant gait for quadruped robots with two locked legs using the G F set theory. First, a quadruped robot and eight stages of its fault-free static gait are introduced. Then, the G F set theory is applied to analyze the robot's mobility stage by stage, which takes the mobility loss caused by the two locked legs into account. By taking full advantage of the mobility, the fault-tolerant gait pattern and trajectory planning method are developed. Further, the omnidirectional locomotion capability, adaptability to rough terrains, energy consumption, speed and influences of locking angles of the fault-tolerant gait are addressed to show its performances. Finally, the fault-tolerant gait and its performances are validated by three simulations. The results show that the robot with the fault-tolerant gait can walk omnidirectionally and adapt to rough terrains while keeping the static stability margin positive. [ABSTRACT FROM AUTHOR]

The operation of solar photovoltaic installations for many years may lead to problems such as reduced energy efficiency and aging of components. Under this framework, replacing certain components in the facility to extend the service life of the power plant is viewed, in some cases, as a feasible strategy. However, despite its enormous strategic interest for the solar PV industry, we find that revamping PV installations has been the focus of very few scientific publications, and even less so when it comes to analyzing real facilities. Thus, this paper performs a techno-economic analysis of three revamping strategies at a real PV power plant located in the south-east of Spain. The strategies consist of substituting, in each case, the PV modules, the inverter, and both components. The simulated results show that the highest production value by installed power is obtained when both the modules and the inverter are replaced. In the same vein, the economic analysis reveals this scenario as the most favorable in terms of profitability. Based on the results obtained, an interesting future line of research would be focused on the extension of the analysis at country level to study the joint impact of numerous revamping actions. • Techno-economic analysis of revamping projects of a real solar PV power plant. • Replacing modules and inverter emerges as the most feasible strategy. • Study's applicability extends to other revamping initiatives and geographical regions. • Economic outcomes allow the most cost-effective alternatives to be determined. • This research can contribute to efficient and sustainable energy planning. [ABSTRACT FROM AUTHOR]

• Development of simulation model for meshed district heating networks. • Investigation of the replacement of a heating plant by a geothermal plant. • In winter, this causes 25% higher mass flows and 16% higher pressures at GT plant. • 42% of CO 2 emissions and 29% of primary energy consumptions can be saved annually. • Supply with 2 different temperatures cause pipe life service reduction of 39–49 %. The geothermal energy production is expanding. How can these systems best be integrated into existing structures? To answer this question, a simplified district heating network model was set up and applied as well as validated to an existing 2000 customer district heating network in Bavaria. The network is powered by gas-fired heating and cogeneration plants. A geothermal plant with a significantly lower supply temperature will replace a heating plant. This paper investigates the arising operating conditions due to the replacement. Therefore, profiles of temperature, mass flow and pressure are analyzed. Furthermore, potential damage caused by temperature changes, a reduction in the supply temperature of the cogeneration plant as well as resulting CO 2 emissions, primary energy consumption and necessary pumping power are examined. The results show that a geothermal plant with a lower supply temperature can be integrated into an existing district heating network, taking all operational restrictions into account. The resulting electricity demand for pumping in the network is approx. 5% higher than with a gas-fired heating plant. In return, annual savings of e.g. 116,000 tCO 2 as well as about 437 GWh primary energy can be achieved. [ABSTRACT FROM AUTHOR]

Abstract: The paper deals with the development of a tool used for the life cycle assessment of residential buildings located in three different European towns: Brussels (Belgium), Coimbra (Portugal) and Luleå (Sweden). The basic tool focuses on the structure and the materials of the buildings and permits the evaluation of the Embodied energy, Embodied carbon and yearly energy consumption. For that purpose, a different set of original data is taken into account for each location, in which the monthly temperatures, energy mix, heating and cooling systems are defined. The energy consumption, being for heating space or water, for cooling or for lighting is transformed into CO2 emissions to deduce the Operational carbon as well. The influence of the energy mix can therefore be assessed in the basic tool. As a matter of fact, the heating and cooling systems habitually used in the three countries are also of great importance. The District Heating system, is, for instance, incorporated in the basic tool. The presence of solar water heater or photovoltaic panels is also strongly influencing the operational carbon. After a short literature review on building LCA and the description of the basic tool, the software Pleiades + Comfie combined with Equer is used to achieve the complete LCA for one building using two different load bearing frames. The results of the calculations for Brussels climate are verified against these software results. The dependence of the results to parameters such as climate, energy mix and habits is then discussed in the companion paper. [Copyright &y& Elsevier]

Abstract: European Union countries’ current energy policies for the transport sector promote, amongst other initiatives; urban mobility plans, the renewal of fleets of cars and industrial vehicles and the introduction of biofuel. From the point of view of eco-efficiency and Life Cycle Assessment (LCA), energy policies must go further. The objective of this paper is to analyse the current transport model and the policies on energy efficiency being promoted in the EU from a LCA point of view. Special attention has been paid to private vehicles, in assessing the environmental impact of the various stages of manufacture, their use and disposal, and the consequences of plans to renew fleets. How old should a vehicle ideally be so that when it is changed, the embodied energy in the materials of the vehicle is less than the gain in energy efficiency due to changing the model for example? In addition the paper analyses the different means of transport in the energy consumption–time ratio from a LCA viewpoint. The fact that reducing transport times leads to greater energy consumption gives rise to the question: how long does nature take to repair the environmental damage caused? [Copyright &y& Elsevier]

• A novel frosting suppression control strategy for air source heat pump is developed. • Frosting suppression can be effectively achieved by using the control strategy. • Heating duration under the novel control strategy is increased by up to 157.68 % • Daily defrosting duration and energy consumption are reduced by 36.30 % and 32.96 % • The novel control strategy can meet required heating capacity with a high COP value. Effective frosting suppression was crucial to further wider applications of air source heat pumps (ASHPs). However, existing frosting suppression measures may not be fully implementable in practice due to various reasons such as short service life, complex manufacturing process and high costs. A condensing-frosting performance map was obtained in a previous study to enable a comprehensive evaluation of the frosting suppression and heating performances of a variable speed (VS) ASHP unit. Therefore, the maps could also provide a basis for developing a novel control strategy for frosting suppression, while still meeting the requirement of desired output heating capacity. As a result, an experimental study on developing a novel control strategy based on the condensing-frosting performance maps has been carried out using an experimental VS ASHP unit, and the study results are presented in this paper. The experimental results suggested that the experimental VS ASHP unit under the proposed novel control strategy could not only achieve effective frosting suppression, but also output the required heating capacity at high COP values whenever possible. By using the developed novel control strategy, the heating duration in one cycle could be increased by up to 157.68 %, and the daily defrosting frequency, duration and energy consumption reduced by up to 59.09 %, 36.30 % and 32.96 %, respectively. The proposed novel control strategy was straightforward and simple to implement, and could contribute to the further development of frosting suppression for ASHPs. [ABSTRACT FROM AUTHOR]

The operational energy use is responsible for an important share of the life cycle environmental impact of buildings. In the national LCA method for buildings in Belgium, as in most environmental impact assessments, operational energy use and associated impacts are kept unchanged throughout the 60-year service life of the building. The energy mix will however change over the building life cycle and this will influence the impact of the operational energy use. The overall aim of this paper is to analyse how long term temporal changes in the electricity mix in Belgium might influence the life cycle environmental impact of buildings using an attributional approach. This paper focuses on three aspects. First, it analyses future scenarios for the Belgian electricity mix as it is uncertain how it will change over time. Second, the environmental impact of these changes in the mix is evaluated using the Belgian life cycle impact assessment method for buildings considering a broad set of indicators. Finally, it is investigated how these changes in the electricity mix during the building service life can be included in the attributional life cycle assessment and how this influences the overall environmental impact of the operational phase. Within this study, three dynamic scenarios are defined and compared with the static approach, i.e. current electricity mix remains unchanged during the next 60 years. The analysis reveals differences in the building life cycle environmental impact of −29% and +34% compared to the current static approach, while differences in the life cycle carbon footprint range from −59% to +33%. This highlights the importance of considering changes in the electricity mix in LCA of buildings and in considering a broad range of environmental indicators instead of solely focussing on greenhouse gas emissions when making policy decisions. In general, a major challenge for the next decade seems to be phasing out nuclear power, without increasing the environmental impact of the electricity mix. [Display omitted] [ABSTRACT FROM AUTHOR]

Concrete is one of the most widespread construction materials in the world, but its production is responsible for significant amounts of energy consumption, and even greater greenhouse gas emissions. However, the substitution of Portland cement with fly ash (FA) reduces both the energy consumption and the greenhouse gas emissions generated during the production of clinker. Currently, most studies of FA concrete focus on mechanical properties, sustainability assessments (environment, society and economy) of FA during its life cycle have not been reported. This paper presents a life cycle sustainability assessment (LCSA) that brings together environmental, economic and social impacts using a proposed three-dimensional coordinate diagram to combine the different units into a single sustainable value. The assessment method is applied to different substitutions of FA in concrete to ascertain the optimum substitution percentage across these three factors. Monte Carlo simulation is then used to evaluate the durability of concrete structures with different FA addition in order to calculate their service life. A case study is conducted of a bridge structure with different FA substitutions; this demonstrates that the addition of FA would improve the sustainability of concrete significantly in the short term. However, when the durability and service life of the structure are taken into account, without maintenance, the use of FA concrete may not improve the environment performance due a potentially shortened service life, but it can reduce the social burden and save costs significantly over the long term. [ABSTRACT FROM AUTHOR]

• MSD is being redefined because of current tendency to modify existing aircraft. • Numerical methods and real-time condition monitoring: two completely opposite trends. • Assessment of numerical methods was performed through comparison of the SIFs results. • Overall deviation within obtained and referent results was quite acceptable. • State of the art numerical methods SMART and XFEM showed minimal deviation. In the face of enormous costs of developing new aircraft, high fuel prices, increasingly demanding environmental standards, harsh economic race and the fight against competing manufacturers, today's aviation is adapting not by producing brand new, more advanced aircraft, but through modifying existing ones by incorporating new more energy efficient engines, in accordance with today's leading criterion that requires minimal fuel consumption, enabling at the same time the longest possible range. The structure of these "new" aircraft is metallic and almost identical as it has been for decades, but now with the new requirement that its service life has to be extended, as long as it is economically justified. In such environment, it is clear that one of the leading tasks is to have the best possible assessment of the negative impact of the mechanism of Multiple Site Damage (MSD), which represents an introduction to the phenomenon of Widespread Fatigue Damage (WFD), the most insidious degradation mechanism of a metallic structure, whose significance was supposed to be diminished in recent decades with accelerated growth in the application of the composite structures. In line with the aforementioned trends, this paper aims to evaluate to what extent today's numerical methods are capable to contribute to the assessment of behavior of such phenomena and which of the proposed approaches could be used for investigating of the fracture problems, both accurately and efficiently. This assignment was conducted through numerical computations of stress intensity factors (SIFs) for two penny shaped cracks in elastic solid estimated by the methods that the authors of this paper consider to be the most relevant in the last few years. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive literature review and a full process-based life-cycle analysis (LCA) of three types of batteries, viz., (1) valve-regulated lead-acid (VRLA), (2) flow-assisted nickel–zinc (NiZn), and (3) non-flow manganese dioxide–zinc (MnO 2 /Zn) for stationary-grid applications. We used the Ecoinvent life-cycle inventory (LCI) databases for the VRLA battery, coupled with inventory data from the CUNY Energy Institute (EI) for the NiZn and MnO 2 /Zn batteries under development there. In doing so, two indicators were tracked: the cumulative energy demand (CED) and global warming potential (GWP) of the upstream processes for producing, manufacturing, and transporting the finished product, as well as the effects of end-of-life impacts. We conducted a normalization of CED and GWP according to Wh of battery capacity to illustrate the effects of discharge rate on this commonly reported metric. We subsequently normalized according to the cumulative kWh of electricity throughput (kWh throughput ) to account for cycle life and efficiency data. This was done considering slow- and fast-discharge parameters for PbA chemistry and for current- and projected- parameters for the NiZn and MnO 2 /Zn chemistries to examine all possible effects. Additionally, the effects of recycle content on reducing CED and GWP were considered. Discharge rate was seen to have a significant effect for the VRLA system, with impacts over 41–46% higher in terms of CED and GWP at the 2-h discharge time, versus an 8-h discharge time, when considering the entire life cycle (kWh throughput normalization). With kWh throughput normalization, the NiZn- chemistry under development has lower CED and GWP than PbA-VRLA batteries for both current and projected targets of round-trip efficiency and cycle life. MnO 2 /Zn performs poorer than VRLA currently (41–52% higher CED and 35–38% higher GWP), but performs significantly better than VRLA when using projected targets (43% lower CED and 47% lower GWP). The energy requirement for battery production and transport is most significant for PbA and MnO 2 /Zn batteries. This is the case for PbA due to its relatively short service life– and this battery was found to be most sensitive to changes in battery service life and efficiency. For MnO 2 /Zn this was a result of low specific energy. [ABSTRACT FROM AUTHOR]

Large spherical valves are the key parts of heavy energy equipments, which play an important role in energy storage and transportation. Valve body parts are the core components of large spherical valve, which directly determine the quality and service life of large spherical valve. In this paper, three processing technologies for one large spherical valve body are proposed, which are die forging, ring rolling and combined ring rolling. Based on SIMUFACT software platform, FE simulations for forming processes with three technologies are carried out, and the forming effects of three processing technologies are evaluated by compare the forming forces, forming accuracies and material utilizations among three forming processes. It is obtained that combined ring rolling technology has less force consumption, well forming accuracy and high material utilization compared to the other two technologies, and it can be regarded as an advanced processing technology for low-consumption, high-performance production of large spherical valve body. [ABSTRACT FROM AUTHOR]

Highlights: [•] This paper quantifies the impact on battery degradation from delivering V2G services. [•] Battery degradation is most dependent on energy throughput. [•] Degradation is most sensitive to depth of discharge when providing ancillary services. [•] V2G services will require multiple battery pack replacements over vehicle lifetime. [Copyright &y& Elsevier]

Abstract: Space heating accounts for a large portion of the world''s carbon dioxide emissions. Ground Source Heat Pumps (GSHPs) are a technology which can reduce carbon emissions from heating and cooling. GSHP system performance is however highly sensitive to deviation from design values of the actual annual energy extraction/rejection rates from/to the ground. In order to prevent failure and/or performance deterioration of GSHP systems it is possible to incorporate a safety factor in the design of the GSHP by over-sizing the ground heat exchanger (GHE). A methodology to evaluate the financial risk involved in over-sizing the GHE is proposed is this paper. A probability based approach is used to evaluate the economic feasibility of a hypothetical full-size GSHP system as compared to four alternative Heating Ventilation and Air Conditioning (HVAC) system configurations. The model of the GSHP system is developed in the TRNSYS energy simulation platform and calibrated with data from an actual hybrid GSHP system installed in the Department of Earth Science, University of Oxford, UK. Results of the analysis show that potential savings from a full-size GSHP system largely depend on projected HVAC system efficiencies and gas and electricity prices. Results of the risk analysis also suggest that a full-size GSHP with auxiliary back up is potentially the most economical system configuration. [Copyright &y& Elsevier]

Abstract: In this paper, by predicting the real time variation in wears of piston-ring face, ring-groove and cylinder bore altogether, the changing end gap of each ring and the changing volume of gas reservoir are calculated. Next, the calculated amount of parts’ wear and oil consumption are compared with the amount of normal wear of each part and normal oil consumption. Then, the durability limit of a piston-ring pack-cylinder bore system is predicted. Finally, the life time of a test engine in terms of abnormal oil consumption caused by the accumulated wear of ring faces and cylinder bore is estimated. [Copyright &y& Elsevier]

Abstract: Our environment is an important resource, not only for use in development, but to conserve. In the 1990s, the importance of our environment became underscored for conservation efforts in many areas. Among them, the building construction industry had played a role in impoverishing the environment, for the sake of improving our quality of life, but at a great cost of impact to the environment. It is therefore incumbent upon the industry to endeavor to mitigate effects from building constructions to our environment. During the life cycle of a building, it consumes energy and other natural resources. But it is difficult to evaluate their effects on the environment during the entire course of a building''s life span, without much time and effort. An easy to handle program is necessary for the calculation of effects to the environment during the life cycle of a building. Many of the software programs developed for these kinds of assessments can only be used with significant restrictions because of their differences in design for scope and content. This paper presents foundations for the development of a Life Cycle Assessment (LCA) program for buildings, focusing on their energy consumption and carbon dioxide emission levels, with a comparison of domestically and foreign designed programs. [Copyright &y& Elsevier]

Abstract: Small, portable electronic devices need power supplies that have long life, high energy efficiency, high energy density, and can deliver short power bursts. Hybrid power sources that combine a high energy density fuel cell, or an energy scavenging device, with a high power secondary battery are of interest in sensors and wireless devices. However, fuel cells with low self-discharge have low power density and have a poor response to transient loads. A low capacity secondary lithium ion cell can provide short burst power needed in a hybrid fuel cell–battery power supply. This paper describes the polarization, cycling, and self-discharge of commercial lithium ion batteries as they would be used in the small, hybrid power source. The performance of 10 Li-ion variations, including organic electrolytes with Li x V2O5 and Li x Mn2O4 cathodes and LiPON electrolyte with a LiCoO2 cathode was evaluated. Electrochemical characterization shows that the vanadium oxide cathode cells perform better than their manganese oxide counterparts in every category. The vanadium oxide cells also show better cycling performance under shallow discharge conditions than LiPON cells at a given current. However, the LiPON cells show significantly lower energy loss due to polarization and self-discharge losses than the vanadium and manganese cells with organic electrolytes. [Copyright &y& Elsevier]

The composite single-cone bit is a new structure of single-cone bit, which breaks the limitation of the one-piece cone structure of existing single-cone bit. The new bit structure makes it possible to apply PDC cutters with strong wear resistance to single cone bit. PDC cutter is more suitable for rock breaking by scraping. In this paper, rock breaking and comparative drilling experiments of composite single-cone bit are carried out. The experiments verified the working principle of the new composite bit. The effective combination of fixed and unfixed cutting structures in the new bit can form complex cross-scraping. The comparative drilling experiments show that the new composite bit has higher rock breaking efficiency than the common single-cone bit, and it is more energy-saving for cross-scraping. The application of PDC cutters can improve the wear resistance of bit cutters and prolong the service life of bit. The research results can provide basic support and reference for subsequent research on the design, development, and application of this new type of bit. • The composite bit proposes a combination of fixed and unfixed cutting structure. • PDC cutters are directly used on the single-cone bit. • The cutters of the composite single-cone bit form complex cross-scraping. • The composite single-cone bit has higher rock breaking efficiency and saves energy. • The application of PDC cutters improves the wear resistance of bit cutters and can prolong the service life of bit. [ABSTRACT FROM AUTHOR]

• Mxene nano-sheets used for the first time as solid lubricant in machine elements. • Improved frictional performance in highly loaded rolling contact verified. • Extended service life of thrust ball bearings by a factor of 2.1. • Improved energy efficiency by a 3.2-fold reduction of frictional torque. Solid lubricants like carbon-based materials, transition metal dichalcogenide compounds, polymers and soft metals, each with their specific merits and limitations, pursue the goal of reducing friction and wear between two rubbing surfaces under substantially dry conditions. Newly emerging early transition metal carbides and carbonitrides, such as Ti 3 C 2 T x -nanosheets (MXenes), seem to be a promising candidate to be used as a solid lubricant due to their weakly bonded multilayer structure with self-lubricating character. For the first time, this paper aims at addressing the application of MXene nanosheets in higher loaded rolling-sliding contacts of machine elements by investigating their friction and wear behavior in thrust ball bearings under ambient conditions. Thereby, a reduction of the frictional torque by a factor of up to 3.2, an extension of the service life by about 2.1 times and a decrease of the linear cumulative wear rate by up to 2.9 compared to uncoated references have been verified. Thus, the Ti 3 C 2 T x -coating already featured results comparable to reports on graphene, amorphous carbon coatings or advanced transition metal dichalcogenide, which demonstrates the tremendous potential of MXene nanosheets as outstanding, next-generation solid lubricant in machine elements. [ABSTRACT FROM AUTHOR]

A common practice in Life Cycle Assessment (LCA) of buildings is to consider a default value for their lifespans. However, statistical data show longer lifespans and it is proved that the higher they are the lower the environmental impacts. Therefore, the common practice of considering a default value for lifespans in buildings LCA involves a high risk of programmed obsolescence in the building sector. This paper addresses a new approach to estimate buildings lifespans based on their structures durability. We use a comparative case study of refurbishment vs. new construction to illustrate its use. The lifespans of the refurbished and the new buildings are estimated by applying degradation models of reinforced concrete structures. Two thermal performance levels are evaluated: standard and passive, in both alternatives, the refurbished and the new building. Comparisons are also made with other approaches to determine buildings lifespans based on default value and statistical data. Results show that a new building can have a lifespan more than six times longer than a refurbished one. A strong dependence of LCA results on the lifespan is revealed. Its value can alter the order of preference of the solutions when comparing alternatives and therefore default value approaches are unadvisable. There is in our case study a 11% potential of environmental improvement for new buildings behaviour by changing current practices and extending buildings' lifespan up to their physical limit. • The lifespans of a new and an existing building of the 50s can differ up to 176 years. • The physical durability of new buildings can be up to 210 years. • Extending the service life of new buildings can reduce annual impacts up to 11%. [ABSTRACT FROM AUTHOR]