Energy harvesting is a promising approach to power novel instrumented implants that have passive sensory functions or actuators for therapeutic measures. We recently proposed a new piezoelectric concept for energy harvesting in total hip replacements. The mechanical implant safety and the feasibility of power generation were numerically demonstrated. However, the power output for the chosen piezoelectric element was low. Therefore, we investigated in the present study different geometry variants for an increased power output for in vivo applications. Using the same finite element model, we focused on new, customised piezoelectric element geometries to optimally exploit the available space for integration of the energy harvesting system, while maintaining the mechanical safety of the implant. The result of our iterative design study was an increased power output from 29.8 to 729.9 µW. This amount is sufficient for low-power electronics.

Although products can contribute to ecosystems positively, they can cause negative environmental impacts throughout their life cycles, from obtaining raw material, production, and use, to end of life. It is reported that most negative environmental impacts are decided at early design phases, which suggests that the determination of product sustainability should be considered as early as possible, such as during the conceptual design stage, when it is still possible to modify the design concept. However, most of the existing concept evaluation methods or tools are focused on assessing the feasibility or creativity of the concepts generated, lacking the measurements of sustainability of concepts. The paper explores key factors related to sustainable design with regard to environmental impacts, and describes a set of objective measures of sustainable product design concept evaluation, namely, material, production, use, and end of life. The rationales of the four metrics are discussed, wit... [more]

Electricity supply quality (ESQ) is critical for healthy economic production, and regional differences in ESQ can widen economic development gaps. To contribute to a more equitable regional development, this study first develops a Gini index of ESQ distribution to measure the inequality among different cities. Then, an econometric model based on the Cobb−Douglas production function is established to quantify the effects of ESQ on regional economy. Finally, we estimate the impacts of ESQ improvement on reducing the economic inequality. The main results show that: (1) Substantial differences exist among the regional ESQ, and the national GDP-based ESQ Gini index was 0.720 in 2018. (2) A GDP-based Lorenz curve has a higher Gini coefficient than the population-based one does, while inequalities in cites are greater than those in rural areas. (3) The ESQ has significant impacts on the regional economic output, and a 1% reduction in the ESQ will, on average, reduce the city-level output by 0... [more]

A comprehensive monitoring program is an integral part of the safe operation of geological CO2 storage projects. Noble gases can be used as geochemical tracers to detect a CO2 anomaly and identify its origin, since they display unique signatures in the injected CO2 and naturally occurring geological fluids and gases of the storage site complex. In this study, we assess and demonstrate the suitability of noble gases in source identification of CO2 anomalies even when natural variability and analytical uncertainties are considered. Explicitly, injected CO2 becomes distinguishable from shallow fluids (e.g., subsea gas seeps) due to its inheritance of the radiogenic signature (e.g., high He) of deep crustal fluids by equilibration with the formation water. This equilibration also results in the CO2 inheriting a distinct Xe concentration and Xe/noble gas elemental ratios, which enable the CO2 to be differentiated from deep crustal hydrocarbon gases that may be in the vicinity of a storage r... [more]

China intends to develop its renewable energy sector in order to cut down on its pollution levels. Concentrated solar power (CSP) technologies are expected to play a key role in this agenda. This study evaluated the technical and economic performance of a 100 MW solar tower CSP in Tibet, China, under different heat transfer fluids (HTF), i.e., Salt (60% NaNO3 40% KNO3) or HTF A, and Salt (46.5% LiF 11.5% NaF 42% KF) or HTF B under two different power cycles, namely supercritical CO2 and Rankine. Results from the study suggest that the Rankine power cycle with HTF A and B recorded capacity factors (CF) of 39% and 40.3%, respectively. The sCO2 power cycle also recorded CFs of 41% and 39.4% for HTF A and HTF B, respectively. A total of 359 GWh of energy was generated by the sCO2 system with HTF B, whereas the sCO2 system with HTF A generated a total of 345 GWh in the first year. The Rankine system with HTF A generated a total of 341 GWh, while the system with B as its HTF produced a total... [more]

In order to explore the changes that autonomous vehicles would bring to the current traffic system, we analyze the car-following behavior of different traffic scenarios based on an anti-collision theory and establish a traffic flow model with an arbitrary proportion (p) of autonomous vehicles. Using calculus and difference methods, a speed transformation model is established which could make the autonomous/human-driven vehicles maintain synchronized speed changes. Based on multi-hydrodynamic theory, a mixed traffic flow model capable of numerical calculation is established to predict the changes in traffic flow under different proportions of autonomous vehicles, then obtain the redistribution characteristics of traffic flow. Results show that the reaction time of autonomous vehicles has a decisive influence on traffic capacity; the q-k curve for mixed human/autonomous traffic remains in the region between the q-k curves for 100% human and 100% autonomous traffic; the participation of a... [more]

This paper develops simplifying entropic models of irreversible closed cycles. The entropic models involve the irreversible connections between external and internal main operational parameters with finite physical dimensions. The external parameters are the mean temperatures of external heat reservoirs, the heat transfers thermal conductance, and the heat transfer mean log temperatures differences. The internal involved parameters are the reference entropy of the cycle and the internal irreversibility number. The cycle’s design might use four possible operational constraints in order to find out the reference entropy. The internal irreversibility number allows the evaluation of the reversible heat output function of the reversible heat input. Thus the cycle entropy balance equation to design the trigeneration cycles only through external operational parameters might be involved. In designing trigeneration systems, they must know the requirements of all consumers of the useful energies... [more]

Wastewater and sewage sludge contain organic matter that can be valorized through conversion into energy and/or green chemicals. Moreover, resource recovery from these wastes has become the new focus of wastewater management, to develop more sustainable processes in a circular economy approach. The aim of this review was to analyze current sewage sludge management systems in Scandinavia with respect to resource recovery, in combination with other organic wastes. As anaerobic digestion (AD) was found to be the common sludge treatment approach in Scandinavia, different available organic municipal and industrial wastes were identified and compared, to evaluate the potential for expanding the resource recovery by anaerobic co-digestion. Additionally, a full-scale case study of co-digestion, as strategy for optimization of the anaerobic digestion treatment, was presented for each country, together with advanced biorefinery approaches to wastewater treatment and resource recovery.

The underlying objective of the paper is to identify and evaluate in the research process vital factors that impact the development of design and construction enterprises of photovoltaic farms on the energy markets, in particular narrowed down to renewable energy sources (RES) markets, including energy coming from photovoltaic sources. The first part of the paper, the epistemological one, introduces a scientific discourse pertaining to conditionings and restrictions related to RES markets in the dimensions of sustainable development. This has been done with the use of literature query, legislative and administrative acts, and reports drawn up for the European Commission. In this reference, we summarized the EU’s essential measures aimed at promoting the idea of sustainability. The second part of the paper, the empirical one, presents a summary of the results obtained within the research pertaining to “opportunities and threats in managing projects of photovoltaic farms in production en... [more]

Gas-fired heat pumps are a potential replacement for condensing boilers, utilizing fossil-fuel resources more efficiently and reducing the amount of biogas or hydrogen required in sustainable gas grids. However, their adoption has been limited due to their large size and high capital cost, resulting in long payback times. For adsorption-based heat pumps, the major development challenge is to maximize the rate of heat transfer to the adsorbent, whilst minimizing the thermal mass. This work develops a modular finned-tube carbon−ammonia adsorption generator that incorporates the adsorbent in highly compacted 3-mm layers between aluminum fins. Manufacturing techniques that are amenable to low cost and high-volume production were developed. The module was tested using the large temperature jump (LTJ) method and achieved a time constant for adsorption and desorption of 50 s. The computational model predicted that if incorporated into two adsorption generators of 6 L volume each, they could b... [more]

There is very little knowledge on the occupant actual hot water comfort (temperature and flow), usage practice, and routines (temporal and spatial distribution of hot water usage in a household). This paper describes the results from the total and hot water measurements in two Danish detached houses. The results show that, at the draw-off points, the temperature of 55 °C is never asked by the occupants, not even in the kitchen sink. The domestic water temperature differentiates depending on the function of the draw-off point, with the shower and kitchen taps being most energy- and water-intense. They constitute around 90% of the hot water use in the house. Shower units on average demand for highest temperature (i.e., 35.5 °C to 40.4 °C). Hand washing operates, on average, at temperature between 20.5 °C to 26.5 °C. Average water temperature at the taps located in utility room varies between 23 °C to 26 °C. These in-depth insight in the total and hot water use in two new-built low energy... [more]

The multi-winding medium frequency transformer (MMFT) has attracted widespread attention, since its application in power electronic transformers can simplify the system structure and reduce the volume and weight. However, the special working conditions of MMFT due to high voltage and high power density increase the difficulty of insulation design for MMFT. For this issue, this paper presents a comprehensive analysis of electric filed characteristics for MMFT. First, the electric field model of MMFT is established using the 2-D finite element method. Based on it, the influences of connection mode, core structure, and hollow winding on the electric field characteristics of MMFT are studied, including the overall electric field distribution, maximum electric field intensity, and the electric field intensity along a fixed path. The results show that there are differences in the maximum electric field intensity for different connection modes and different core structures, which provides ref... [more]

For integrating large batteries in the medium voltage grid, current fed solid-state transformers offer galvanic isolation and a significant weight and size reduction. While the power losses increase with frequency and flux density, the core volume is contrariwise. Therefore, a design optimisation to achieve minimum losses and/or a minimum volume is essential. An optimisation strategy is proposed in this paper to find the optimum operating frequency and core flux density under certain practical constraints such as winding voltage per turn, clearance between transformer windings, saturation flux density and minimum efficiency. Differently from previous works, the proposed strategy provides a holistic approach for the design considering all main power losses from all main components using nonsinusoidal voltage waveforms and different operating conditions. Analytical equations for the power losses calculation and the cores design are derived and validated using ANSYS and MATLAB Simulink so... [more]

Lignocellulosic rice processing residue was pretreated in liquid hot water (LHW) at three different temperatures (140, 160, and 180 °C) and two pretreatment times (10 and 20 min) in order to assess its effects on hydrolysates composition, matrix structural changes and methane yield. The concentrations of acetic acid, 5-hydroxymethylfurfural and furfural increased with pretreatment severity (log Ro). The maximum methane yield (276 L kg−1 VS) was achieved under pretreatment conditions of 180 °C for 20 min, with a 63% increase compared to untreated biomass. Structural changes resulted in a slight removal of silica on the upper portion of rice husks, visible predominantly at maximum severity. However, the outer epidermis was kept well organized. The results indicate, at severities 2.48 ≤ log Ro ≤ 3.66, a significant potential for the use of LHW to improve methane production from rice processing residue.

This paper examines a microconstruction consisting of nickel (Ni)/chromium (Cr) alloy thin-film. The total length of the microconstruction was 28 mm, the width was 0.2 mm, and the height was designed to be 1 μm. A thin-film of Ni/Cr alloy was co-sputtered on a silicon dioxide wafer patterned with photoresist via a RF magnetron sputtering system. The RF power ratios applied to the 4 inch target of Ni and Cr were 300 W:100 W (3:1), 300 W:150 W (2:1), and 150 W:150 W (1:1). The electrical resistance of the manufactured microconstruction was calculated and measured through Hall measurements. The temperature generated by applying 1−10 V to the microconstruction electrode was observed by using an infrared camera, and was summarized using a linear equation according to the power applied to each sample.

The article presents the issue of designing a network of electric vehicle charging stations (EVCSs) for servicing passenger and commercial vehicles and taking into account the already existing locations. The authors propose a five-stage multicriteria- and GIS-based EVCS location methodology (5MAGISEV) for designing the EVCS network that includes defining potential EVCS locations (stage 1), constructing a family of evaluation criteria (stage 2), generating alternatives (stage 3), selecting an appropriate multiple criteria decision aid method (stage 4) and conducting a multicriteria evaluation of alternatives (stage 5). The methodology was verified by its experimental application for solving the problem of EVCS location in Poznan, Poland. As a result of its application, a set of over 155,000 alternatives was generated in view of different EVCS location determination policies. A family of eight criteria with subcriteria was proposed to assess the solutions, including the evaluation of the... [more]

The cyclic carbonation-calcination of CaCO3 in fluidized bed reactors not only offers a possibility for CO2 capture but can at the same time be implemented for thermochemical energy storage (TCES), a feature which will play an important role in a future that has an increasing share of non-dispatchable variable electricity generation (e.g., from wind and solar power). This paper provides a techno-economic assessment of an industrial-scale calcium looping (CaL) process with simultaneous TCES and CO2 capture. The process is assumed to make profit by selling dispatchable electricity and by providing CO2 capture services to a certain nearby emitter (i.e., transport and storage of CO2 are not accounted). Thus, the process is connected to two other facilities located nearby: a renewable non-dispatchable energy source that charges the storage and a plant from which the CO2 in its flue gas flow is captured while discharging the storage and producing dispatchable electricity. The process, which... [more]

Nowadays products are developed at a rapid pace, with shorter and shorter times between concept and go to market. With the advancement in technology, product designers and manufacturers can use new approaches to obtain information about their products and transform it into knowledge that they can use to improve the product. We developed the Poket Framework platform to facilitate the generation of product knowledge. In order to increase the reliability and safety in operation of electrical equipment, an evaluation is proposed, through tests and studies, using the original Poket Framework platform. Thus, several tests and studies were performed, which included testing and analyzing the correct integration in several use cases and remote data acquisition, and testing and analysis of the Poket Framework using literature established data sets of household appliances and electrical systems. Possible evolutions and Poket platform extensions are also considered.

Mining design is usually evaluated with different multiple-criteria decision-making (MCDM) methods when it comes to large open pit or underground ore mines, but it is not used on quarry sites. Since Croatia is mostly mining stone, the implementation of such methods in decision making of the quarry mine design is imperative but left out. In this paper, the PROMETHEE II and AHP decision-making methods are implemented on the quarry site to find out the best final quarry design contour. By implementing the MCDM methods, the best quarry model was chosen based on 22 different criteria parameters out of three final quarry designs. The chosen model is not only financially sound but also has the least environmental impact.

The separation of solution gas has great influence on the development of gas-bearing tight oil reservoirs. In this study, physical simulation and high-pressure mercury intrusion were used to establish a method for determining the porous flow resistance gradient of gas-bearing tight oil reservoirs. A mathematical model suitable for injection−production well networks is established based on the streamline integral method. The concept of pseudo-bubble point pressure is proposed. The experimental results show that as the back pressure decreases from above the bubble point pressure to below the bubble point pressure, the solution gas separates out. During this process, the porous flow resistance gradient is initially equal to the threshold pressure gradient of the oil single-phase fluid, then it becomes relatively small and stable, and finally it increases rapidly and exponentially. The lower the permeability, the higher the pseudo-bubble point pressure, and the higher the resistance gradie... [more]

Rotational Piezoelectric Energy Harvesting (RPZTEH) is widely used due to mechanical rotational input power availability in industrial and natural environments. This paper reviews the recent studies and research in RPZTEH based on its excitation elements and design and their influence on performance. It presents different groups for comparison according to their mechanical inputs and applications, such as fluid (air or water) movement, human motion, rotational vehicle tires, and other rotational operational principal including gears. The work emphasises the discussion of different types of excitations elements, such as mass weight, magnetic force, gravity force, centrifugal force, gears teeth, and impact force, to show their effect on enhancing output power. It revealed that a small compact design with the use of magnetic, gravity, and centrifugal forces as excitation elements and a fixed piezoelectric to avoid a slip ring had a good influence on output power optimisation. One of the i... [more]

Small-scale electrical power generation (<100 kW) from biogas plants to provide off-grid electricity is of growing interest. Currently, gas engines are used to meet this demand. Alternatively, more efficient small-scale solid oxide fuel cells (SOFCs) can be used to enhance electricity generation from small-scale biogas plants. Most electricity generators require a constant gas supply and high gas quality in terms of absence of impurities like H2S. Therefore, to efficiently use the biogas from existing decentralized anaerobic digesters for electricity production, higher quality and stable biogas flow must be guaranteed. The installation of a biogas upgrading and buffer system could be considered; however, the cost implication could be high at a small scale as compared to locally available alternatives such as co-digestion and improved digester operation. Therefore, this study initially describes relevant literature related to feedstock pre-treatment, co-digestion and user operational... [more]

In this paper, a design driven comparison between two 190 kVA industrial three-phase two-level voltage source converter (2L-VSC) designs based in silicon carbide (SiC) and silicon (Si) for 690 V grids is presented. These two designs were conceived to have the same nominal power, while switching at reasonable switching speeds and requiring the same case to ambient thermal impedance. Under these conditions, the designs were studied to detect the potential gains and limitations that a pragmatic converter design could feature when using these two technologies regarding cost, efficiency, size and weight. To achieve this, experimentally determined semiconductor characteristics were used to perform simulations, the results of which were then used to design the essential parts of the converter. These designed parts were then corroborated with manufacturers, from which physical characteristics of all designed components were obtained. The results show that the SiC based design presents substant... [more]

In comparison to lignocellulosic biomass, which is suitable for thermo-chemical valorization, the organic fraction of municipal solid waste (OFMSW) is mainly treated via composting or anaerobic digestion (AD). An efficient utilization of OFMSW is difficult due to variations in its composition. Based on the characteristics of OFMSW, hydrothermal treatment (HTT) experiments at temperatures < 200 °C as an alternative OFMSW-processing were evaluated in this study. The raw OFMSW was characterized with a dry matter (DM)-based organic dry matter (oDM) content of 77.88 ± 1.37 %DM and a higher heating value (HHV) of 15,417 ± 1258 J/gDM. Through HTT at 150, 170 and 185 °C, the oDM contents as well as H/C and O/C ratios were lowered while the HHV increased up to 16,716 ± 257 J/gDM. HTT led to improved fuel properties concerning ash melting, corrosion stress and emission behavior. Negative consequences of the HTT process were higher contents of ash in the biochar as well as accumulated heavy me... [more]

This study was aimed at identifying the causes of continuous failures, fires, and explosions of electrical and electronic systems in educational facilities that result from lightning, which occurs frequently during the summer. The study is also aimed at suggesting prevention measures for such damage. The installation status and problems of lightning protection systems (LPSs) were examined by analyzing the damage compensation data of the Korea Institute of Educational Facility Safety, a questionnaire and field survey, and related laws. A total of 49,989 educational facilities responded to the questionnaire. The survey indicated that out of all the educational facilities, 21% had external LPSs, 6.2% had internal LPSs, 4% had both internal and external LPSs, and only 2.5% had installed bonding in addition to internal and external LPSs. The LPSs were not installed properly because the heights of most educational facilities are less than 20 m although the Building Act stipulates that LPSs s... [more]