The paper presents a novel twofold use of the photographic technique for flow boiling heat transfer investigation in the horizontal mini-channel. The dedicated measurement system was constructed to record basic thermal and flow parameters, i.e., boiling liquid inlet and outlet temperatures and pressures, and also temperatures inside the heating block to calculate heat flux going into the liquid. A high-speed video camera equipped with synchronous movement system was applied to combine the recording of two-phase flow images with simultaneous local void fraction measurements both based on the same photographic data set. The data were collected, managed, and refined with the scripts developed in the MathWorks Matlab 2019b environment. The synchronous use of two intelligent techniques in the scripts, i.e., the background subtraction technique and the statistical analysis of individual pictures allowed obtaining reliable experimental results. The proposed method of the void fraction determi... [more]

The adoption of electric vehicles promises numerous benefits for modern society. At the same time, there remain significant hurdles to their wide distribution, primarily related to battery-based energy sources. This review concerns the systematization of knowledge in one of the areas of the electric vehicle control, namely, the energy management issues when using braking controllers. The braking process optimization is summarized from two aspects. First, the advantageous solutions are presented that were identified in the field of gradual and urgent braking. Second, several findings discovered in adjacent fields of automation are debated as prospects for their possible application in braking control. Following the specific classification of braking methods, a generalized braking system composition is offered, and all publications are evaluated primarily in terms of their energy recovery abilities as a global target. Then, conventional and intelligent classes of braking controllers are... [more]

High-frequency components of common-mode voltage (CMV) induce the shaft voltage and bearing current, which lead to premature failures in motors. In addition, due to non-zero average CMV, the low-frequency components of CMV, particularly the third-order harmonic component, have been reported to cause difficulties in common-mode filter design. Furthermore, the utilization of distant voltage vectors in the pulse-width modulation (PWM) with reduced CMV magnitudes gives rise to high output harmonic distortion compared to PWM ones without CMV reduction. In an attempt to solve the aforementioned issues, this article presents a PWM strategy that features reduced CMV magnitudes, zero average CMV, and improved output harmonic distortion for a five-level cascaded H-bridge (CHB) converter. In addition, the carrier rotation technique based on the phase-leg redundancy of the CHB topology is also combined with the proposed scheme to achieve equal power loss distribution among power switching devices.... [more]

The aim of this paper is to analyse and evaluate the deployment of smart platforms (operated by distribution system operators—DSOs—or by independent parties) in key jurisdictions that facilitate the trading of flexibility services—primarily by DSOs. We look at key innovation projects/initiatives from seven jurisdictions, including Australia, France, Germany, Great Britain, Japan, The Netherlands and Norway. We have deliberately selected 13 use cases that operate under different regulatory frameworks and market rules, and have been recently implemented (from 2017 onwards). With the selection of key use cases this study seeks to discuss the different smart architecture solutions and main capabilities across different demonstrators and their relationship to business as usual. It also analyses flexibility market designs, identifies main characteristics, and compares different price formation schemes and procurement methods. The value of flexibility for DSOs is also discussed.

In the current state of maturity of severe accident codes, the time has come to foster the systematic application of Best Estimate Plus Uncertainties (BEPU) in this domain. The overall objective of the HORIZON-2020 project on “Management and Uncertainties of Severe Accidents (MUSA)” is to quantify the uncertainties of severe accident codes (e.g., ASTEC, MAAP, MELCOR, and AC2) when modeling reactor and spent fuel pools accident scenarios of Gen II and Gen III reactor designs for the prediction of the radiological source term. To do so, different Uncertainty Quantification (UQ) methodologies are to be used for the uncertainty and sensitivity analysis. Innovative AM measures will be considered in performing these UQ analyses, in addition to initial/boundary conditions and model parameters, to assess their impact on the source term prediction. This paper synthesizes the major pillars and the overall structure of the MUSA project, as well as the expectations and the progress made over the f... [more]

The main goal of this work is the analysis of potential energy and green benefits of 3D printing on building construction. Current literature reports a considerable number of benefits for 3D printing, namely, reduction of material use, lower operational costs and time-saving. The authors also mention design freedom, higher efficiency, productivity and quality. This work presents the latest developments in 3D printing in civil engineering, namely, a review of the last 3D printing projects and the limitations of construction 3D printing with a focus on large-scale applications, technology costs, mix development and optimisation and thermal behaviour.

Low-voltage distribution grids face new challenges through the expansion of decentralized, renewable energy generation and the electrification of the heat and mobility sectors. We present a multi-agent system consisting of the energy management systems of smart buildings, a central grid controller, and the local controller of a transformer. It can coordinate the provision of ancillary services for the local grid in a centralized way, coordinated by the central controller, and in a decentralized way, where each building makes independent control decisions based on locally measurable data. The presented system and the different control strategies provide the foundation for a fully adaptive grid control system we plan to implement in the future, which does not only provide resilience against electricity outages but also against communication failures by appropriate switching of strategies. The decentralized strategy, meant to be used during communication failures, could also be used exclu... [more]

Eco-drive is a widely used concept. It can improve fuel economy for different driving behaviors such as vehicle acceleration or accelerator pedal operation, deceleration or coasting while slowing down, and gear shift timing difference. The feasibility of improving the fuel economy of urban buses by applying eco-drive was verified by analyzing data from drivers who achieved high fuel efficiencies in urban buses with a high frequency of acceleration/deceleration and frequent operation. The items that were monitored for eco-drive were: rapid take-off/acceleration/deceleration, accelerator pedal gradient, coasting rate, shift indicator violation, average engine speed, over speed, and gear shifting under low-end engine speed. The monitoring method for each monitored item was set up, and an index was produced using driving data. A fuel economy prediction model was created using machine learning to determine the contribution of each index to the fuel economy. Furthermore, the contribution of... [more]

Given the large demand nowadays for domestic hot water, and its impact on modern building energy consumption, air source transcritical CO2 heat pumps have been extensively adopted for hot water production. Since their system efficiency is limited by significant irreversibility, a CO2-based mixture could offer a promising drop-in technology to overcome this deficiency without increasing system complexity. Although many CO2 blends have been studied in previously published literature, little has been presented about the CO2/R32 mixture. Therefore, a proposed mixture for use in transcritical CO2 heat pumps was analyzed using energy and exergy analysis. Results showed that the coefficient of performance and exergy efficiency variation displayed an “M” shape trend, and the optimal CO2/R32 mixture concentration was determined as 0.9/0.1 with regard to flammability and efficiency. The irreversibility of the throttling valve was reduced from 0.031 to 0.009 kW⋅kW−1 and the total irreversibility... [more]

A mixture of canola oil (Co), n-hexane (Hex), and ethyl alcohol (Et) was proposed as a new energy material for powering diesel engines. For this purpose, surface tension, density, and viscosity measurements, as well as engine tests, were performed for 88%Co10%Hex2%Et and 83%Co15%Hex2%Et mixtures at 20 °C. The adsorption and volumetric properties of these mixtures were compared to those of individual mixture components, as well as diesel fuel (Df) and oleic, linoleic, α-linolenic, palmitic, and stearic acids. It was revealed that the values of surface tension, viscosity, and density of Co were higher than those of the Co components. The addition of 10% Hex and 2% Et to Co caused a more than twofold decrease in its viscosity, while the addition of 15% Hex and 2% Et caused a more than fourfold reduction of Co viscosity. In addition, a mixture of Co with 2% Et and 10% Hex had a density similar to that of Df. In turn, theoretical calculations showed that the addition of n-hexane and ethanol... [more]

The design of gear pumps and motors is focused on more efficient units which are possible to achieve using advanced numerical simulation techniques. The flow that appears inside the gear pump is very complex, despite the simple design of the pump itself. The identification of fluid flow phenomena in areas inside the pump, considering the entire range of operating parameters, is a major challenge. This paper presents the results of simulation studies of leakages in axial and radial gaps in an external gear pump carried out for different gap shapes and sizes, as well as various operating parameters. To investigate the processes that affect pump efficiency and visualize the fluid flow phenomena during the pump’s operation, a CFD model was built. It allows for a detailed analysis of the impact of the gears’ eccentricity on leakages and pressure build-up on the circumference. Performed simulations made it possible to indicate the relationship between leakages resulting from the axial and ra... [more]

Evidence collected by researchers over several decades suggests that the successful implementation of the Energy Efficiency Obligation Scheme (EEOS) may deliver significant, cost-effective energy savings over many years. However, before starting EEOS in Latvia, predictions by energy efficiency policy researchers envisaged that it is at high risk of savings shortfalls. This study aims to carry out an ex-post policy evaluation of EEOS in Latvia and assess its ability to deliver significant savings in the first phase of the new EEOS. This paper questions whether the new EEOS can reach savings goals without prior experience with voluntary agreement schemes and emulation of successful EEOS from other countries. The second goal of the research is to create a web-based optimization tool as an Interactive Learning Environment to help policymakers and EEOS-obliged parties to create goal-oriented strategies. The study has found that, contrary to expectations, Latvia has reached and even overfulf... [more]

With sustainable energy being the key to reaching climate neutrality, the utilization of non-wooden biomass is a necessity. This article compares the emissions and efficiency of combusting a number of types of agrobiomass and wood pellets. A comparison was made on a moving grate pellet burner mounted in a boiler, where flue gas had a vertical flow via two pass heat exchangers with turbulization elements. Tests were conducted on wood pellets (ENPlus), miscanthus straw pellets, sunflower husk pellets, and corn stover pellets. During combustion, both wood and miscanthus pellets met the PN-EN 303-5:2012 emission and efficiency requirements. Corn stover pellets met the requirement on the nominal capacity. Sunflower husk pellets are characterized by excessive CO and particulate matter emissions. Sunflower husk pellets were the most problematic fuel from the point of view of the results of this research. During combustion of the miscanthus straw pellets there was a need to decrease the nomina... [more]

Microgrids operating on renewable energy resources have potential for powering rural areas located far from existing grid infrastructures. These small power systems typically host a hybrid energy system of diverse architecture and size. An effective integration of renewable energies resources requires careful design. Sizing methodologies often lack the consideration for reliability and this aspect is limited to power adequacy. There exists an inherent trade-off between renewable integration, cost, and reliability. To bridge this gap, a sizing methodology has been developed to perform multi-objective optimization, considering the three design objectives mentioned above. This method is based on the non-dominated sorting genetic algorithm (NSGA-II) that returns the set of optimal solutions under all objectives. This method aims to identify the trade-offs between renewable integration, reliability, and cost allowing to choose the adequate architecture and sizing accordingly. As a case stud... [more]

The article presents the concept of application of a multiphase matrix converter (MMC)-based device working as a phase-shifting control device in a power system. A matrix M × M multiphase converter is a simple structure incorporating M × M bidirectional switches, connecting M input phases to M output phases (a square structure is used). The device, in this research and under proposed control, is able to build M output sinusoidal-shape phases (desired output) from parts of input voltages. The proposed MMC-based device can be considered as a new flexible AC transmission system (FACTS) apparatus. Three basic control systems that enabled the creation of output waveforms as the combination of input ones were presented. Both 6 × 6 and 12 × 12 matrix structures were introduced, since 3 × 6 and 3 × 12 transformers are already in use. The mathematical, Simulink, and laboratory models were built to extract characteristic features of the MMC. The chosen “area-based” control procedure was based on... [more]

This research presents the energy, exergy, economic, and environmental assessment, and multi-objective optimization of a flash-binary geothermal CCHP cycle. A sensitivity analysis of production well inlet temperature and cooling to power flow ratio on exergetic, economic, and environmental parameters was conducted. Furthermore, the effects of the inflation rate and plant working hours on economic parameters were investigated. Results showed that increasing the production well inlet temperature harms exergy efficiency and exergetic performance criteria and results in a gain in exergo-environmental impact index and heating capacity. In addition, the total plant cost increased by raising the production well temperature. Furthermore, increasing the cooling to power flow ratio caused a reduction in exergy efficiency, exergetic performance criteria, and produced net power and an enhancement in exergy destruction, cooling capacity, and total plant cost. The exergy efficiency and total cost ra... [more]

Underground coal gasification (UCG) technology converts deep coal resources into synthesis gas for use in the production of electricity, fuels and chemicals. This study provides an overview of the systematic methods of the in situ coal gasification process. Furthermore, the model of the porous structure of coal has been presented and the gas movement taking place in the carbon matrix—which is part of the bed—has been described. The experimental tests were carried out with the use of air forced through the nozzle in the form of a gas stream spreading in many directions in a porous bed under bubbling conditions. The gas flow resistance coefficient was determined as a function of the Reynolds number in relation to the diameter of the gas flow nozzle. The proprietary calculation model was compared to the models of many researchers, indicating a characteristic trend of a decrease in the gas flow resistance coefficient with an increase in Reynolds number. The novelty of the study is the dete... [more]

This work focuses on a signal-based diagnosis approach dedicated to proton exchange membrane water electrolyzer (PEM WE) anode pump fault. The PEM WE cell measurements are performed with an experimental test bench to highlight the impact of water flow rate in the anode compartment. This approach is non-intrusive, and it can detect anode flow rate variation during the electrolysis and is designed to fulfill online diagnosis requirements. Contrary to electrochemical impedance spectroscopy-based approaches (EIS), this method stands out from existing procedures as a result of its few requirements, excluding any signal with perturbing amplitude. Therefore, the electrolyzer remains continuously available, even while the analysis is performed. The empirical mode decomposition (EMD) is used to decompose the signal variation into a sum of amplitude modulation and frequency modulation (AM-FM) components, called intrinsic mode functions (IMFs). In this work, the PEM WE current signal is decompose... [more]

Brushless doubly-fed induction generators have higher reliability, making them an attractive choice for not only offshore applications but also for remote locations. These machines are composed of two back-to-back voltage source converters: the grid side converter and the rotor side converter. The rotor side converter is typically used for reactive current control of the power winding using the control winding current. A low voltage ride through (LVRT) fault is detected using a hysterisis comparison of the power winding voltage. This approach leads to two problems, firstly, the use of only voltage to detect faults results in erroneous or slow response, and secondly, sub-optimal control of voltage drop because of static reference values for reactive current compensation. This paper solves these problems by using an analytical model of the voltage drop caused by a short circuit. Moreover, using a fuzzy logic controller, the proposed technique employs the voltage frequency in addition to... [more]

The introduction of an energy storage system plays a vital role in the integration of renewable energy by keeping a stable operation and enhancing the flexibility of the power flow system, especially for an islanding microgrid which is not tied to a grid and for a self-contained microgrid which tries to stay independent from a grid as much as possible. To accommodate the effects of power fluctuations of distributed energy resources and power loads on power systems, a power flow assignment under power balance constraint is essential. However, due to power limitations of power devices, the capacity of storage devices, and power flow connections, the power balance may not be achieved. In this paper, we proposed a system characterization which describes the relation among power generators, power loads, power storage devices, and connections that must be satisfied for a system to operate by keeping SOC limitations of power storage devices. When we consider one power generator, one power loa... [more]

The paper provides an analysis of a transportation system with a long stator linear drive. The presented analysis for an in-house transportation system may be easily scaled into large transportation systems like maglev and hyperloop. It investigates the impact of the division of the stator into shorter parts which are sequentially supplied. Then it compares the concept of single-inverter and multi-inverter drive systems. The presented research includes the analysis of drive system power parameters. The drive system characteristics depending on the length of the active part of the linear motor are presented for each configuration, followed by a description of differences in the required inverter power and the obtained average thrust force. The paper proposes a new arrangement of the multi-inverter drive system incorporating multi-level inverters, which allows decreasing voltage oscillations in the DC circuit of drive inverters. The operation of the transportation system is presented in... [more]

Seawater represents a potential resource to ensure sustainable availability of water for population and irrigation purposes, especially in some areas of the world. Desalination processes allow the production of fresh water, but they generate also brine as waste product. Sustainable brine management should be identified to ensure proper disposal and potentially resource recovery. This experimental study showed that emerging technologies such as Microbial Desalination Cells (MDCs) may provide a valuable contribution to the sustainability of the seawater desalination sector. In this paper, we report results on lab-scale desalination brine treatments applying MDCs, which allow energy savings, resource recovery, environmental impact minimization, and reduction of the organic load in municipal wastewater. Our results showed that MDCs’ treatment allows the removal of approximately 33 g of salts (62% of the total)—including chlorides, bromides, and sulphates—from 20 mL of brine within 96 h. Th... [more]

It remains unclear whether the decision to cook with both polluting and cleaner-burning fuels (‘fuel stacking’) serves as a transition phase towards the full adoption of clean-cooking practices, or whether stacking allows households to enhance fuel security and choose from a variety of cooking technologies and processes. This paper offers a unique contribution to the debate by positioning fuel stacking as the central research question in the exploration of existing household survey data. This research analyses the World Bank’s Multi-Tier Framework survey data concerning energy access and cooking practices in Cambodia, Myanmar, and Zambia. Its novel approach uses fuel expenditure data to group urban households according to the intensity of biomass consumption (wood, charcoal) relative to modern fuel consumption (electricity, gas). The research explores how different fuel-stacking contexts are associated with factors related to household finances, composition, experiences of electricity,... [more]

The full electrification of ports is a promising prospect for saving energy and reducing greenhouse gas emissions. The control scheme of the reefer container is particularly important for the energy management of the port, as the operation of the reefer container is one of the main energy consumers of ports. This paper proposes a reefer container hierarchical control scheme that contains a day-ahead module and intra-day module which is used to generate a rough scheduling strategy based on forecast data and fine-tuning the strategy, respectively. The final strategy should realize the economical operation while ensuring that each reefer container does not exceed the temperature limit during operation. Numerical analysis on the reefer container park with 200 and 850 containers using the Time of Use (TOU) tariff and super-peak tariff is fully analyzed. In the case of 200 containers, the proposed method helps reduce operating costs by about 14.7%, and 18% in the scenario of 850 containers.... [more]

In the light of climate change, the drive for zero carbon buildings is known as one response to reduce greenhouse gas emissions. Within New Zealand, research on climate change mitigation and environmental impacts of buildings has received renewed attention. However, there has been no detailed investigation of zero carbon building practices. This paper undertakes an exploratory study through the use of semi-structured interviews with government representatives and construction industry experts to examine how the New Zealand construction industry plans and implements zero carbon buildings. The results show that New Zealand’s construction industry is in the early stage of transiting to a net-zero carbon built environment. Key actions to date are focused on devising a way for the industry to develop and deliver zero carbon building projects. Central and local governments play a leading role in driving zero carbon initiatives. Leading construction firms intend to maximise the carbon reducti... [more]