Achieving nearly zero-energy buildings (nZEB) is one of the main objectives defined by the European Union for achieving carbon neutrality in buildings. nZEBs are heavily reliant on distributed renewable generation energy sources, which create new challenges associated with their inherent intermittency. To achieve nZEB levels, demand management plays an essential role to balance supply and demand. Since up to two-thirds of the total consumed energy in buildings is dispended for Heating, Ventilation and Air Conditioning (HVAC) operations, intelligent control of HVAC loads is of utmost importance. The present work aims to offer a solution to improve a building microgrids’ flexibility by shifting thermal loads and taking advantage of room thermal inertia. Innovation is present in using the internet of things to link several decentralized local microcontrollers with the microgrid and in the applicability of different control algorithms, such as the pre-emptive heating/cooling of a room. The... [more]

Achieving carbon neutrality by 2050 is one of the European Union’s key priorities. Yet, the attitude of numerous politicians, of the professional community, and of society in general towards the threat posed by climate change is ambivalent. Arguments are frequently heard about the transition to a low-carbon economy that will be very costly, with increased unemployment, and that in reality climate change may not even be that severe. Added to this, there are human rights and freedoms, and in the case of architects and designers, the right to freedom of creation, to choice of materials, etc. The present article seeks to show that the issue of sustainable architecture and construction is not a whim, but an absolute necessity, and that true freedom lies in recognizing this fact and adapting our actions accordingly. However, even if we have the good intentions to adapt the needed actions, there is still the question of how to react in the right way, without causing myriad unwanted side-effec... [more]

Recent major advancements in drone charging station design are related to the differences in coil design between the material (copper or aluminum) and inner thickness (diameter design) to address power transfer optimization and increased efficiency. The designs are normally challenged with reduced weight on the drone’s side, which can lead to reduced payload or misalignment position issues between receiver and transmitter, limiting the performance of wireless charging. In this work, the coil combination was tested in vertical alignment from 2 cm to 50 cm, and in lateral misalignment positions that were stretched across 2, 5, 8, 10, and 15 cm ranges. Simulated and experimental results demonstrated improved transfer distances when the drone battery load was 100 Ω. With the proposed design, the vertical transfer power that was achieved was 21.12 W, 0.460 A, with 81.5% transfer efficiency, while the maximum lateral misalignment air gap that was achieved was 2 cm with 19.22 W and 74.15% eff... [more]

This work focuses on the modeling and simulation of constant pressure systems based on variable speed pumps, with the aim of studying and evaluating their performance from a multidisciplinary approach. Using the physical models of the Simscape library, from MATLAB/Simulink R2019b, two study cases are assembled consisting of: piping system, a hydropneumatic tank, centrifugal pumps with an induction motor, variable speed drives, and a control system. Case one is comprised of one pump at a fixed speed and another at variable speed, and case two with both pumps at variable speed. For the parameterization of the models, data from manufacturers and process requirements are used. The different stages of the control system are integrated and configured; these are constant V/f control, slip compensation, space vector modulation (SVM,) and pressure controller. The dynamic response of the system, power saving, transient current at startup, and harmonic distortion are evaluated. The results showed... [more]

The electric machines are the elements most used at an industry level, and they represent the major power consumption of the productive processes. Particularly speaking, among all electric machines, the motors and their drives play a key role since they literally allow the motion interchange in the industrial processes; it could be said that they are the medullar column for moving the rest of the mechanical parts. Hence, their proper operation must be guaranteed in order to raise, as much as possible, their efficiency, and, as consequence, bring out the economic benefits. This review presents a general overview of the reported works that address the efficiency topic in motors and drives and in the power quality of the electric grid. This study speaks about the relationship existing between the motors and drives that induces electric disturbances into the grid, affecting its power quality, and also how these power disturbances present in the electrical network adversely affect, in turn,... [more]

The energy efficiency of road refrigerated transport is still a less researched area, despite a significant amount of energy being used for cooling perishable goods inside the refrigerated vehicle. The refrigeration units of these vehicles continuously operate while en route from the cargo sender to the recipient, even during the vehicle’s forced stopovers due to the driver’s working time limitations. This article aims to summarize the impact of the parking sheds used in rest and service areas on the energy consumption of the vehicle’s refrigeration unit. The achievable cost savings by decreasing the energy consumption of the semi-trailer’s refrigeration units are also presented. We establish a mathematical model to calculate the heat balance and verify our approach. The calculation results, which were carried out under certain operating conditions of the refrigeration unit of a semi-trailer, provide an opportunity to achieve savings on a scale of 12.03%. Lastly, ideal locations of res... [more]

This study applies the Physical Optimum (PhO) as a reference value to rate the efficiency of two technical options for the oxygen supply of a hospital. The systematic comparison of the alternative processes using the PhO as a benchmark for the minimum input (exergy in this case) required to run a process with a certain benefit allows to determine the potential for optimization of each technology. Differences are analyzed by visualizing the losses of each individual production step in a process as well as by the resulting overall energy demand, including the primary energy. Possible alternatives are purchasing liquid oxygen from a cryogenic process or the production by means of Pressure Swing Adsorption (PSA) on site. The cryogenic production shows a lower exergy demand even though it also has a higher potential for optimization. Yet, the total losses, significantly impacted by the unavoidable transportation, sum up, resulting in the conclusion that the PSA is the preferable option over... [more]

The development of global and regional energy markets is one of the most important problems of the current state of global economic relations and is one of the highest-priority areas in the formation of national and regional strategies for the socio-economic development of any country. The role of energy supply is focused on monitoring and compliance with standards. However, in recent years, the importance of energy supply to the housing stock has increased significantly, which has led to an expansion of the role of management within the framework of the risk management function. Kazakhstan has a Unified electric power system, which is represented by a set of power stations, transmission lines, and substations that provide reliable and high-quality energy supply to consumers. Currently, the main task within the framework of the priority of the development of Kazakhstan’s energy sector is to build up the energy base and provide the growing needs of the population and the economy with th... [more]

This paper shows the technical−economic, operational and environmental feasibility of four off-grid hybrid power systems to supply energy to the Cerrito de los Morreños community in Ecuador. These configurations consist of combinations of diesel generators, solar photovoltaic systems, and battery energy storage systems. Each configuration was simulated and the results were analyzed for two different load conditions: (1) the existing load profile and (2) a reduced load profile by incorporating an energy efficiency initiative. Homer Pro software was used to perform the simulations. The planning horizon for the simulations was selected to be 15 years. The results showed the diesel/photovoltaic/battery configuration with energy efficiency showed the best performance, which was achieved with a photovoltaic system of 160 kWp, the existing generator of 165 kW and a storage system of 283 kWh. The stand-alone diesel generator and photovoltaic/diesel configurations showed higher Net Present Cost... [more]

Climate change already affects all inhabited regions of the world, with human influence contributing to many observed changes in climate extremes and to mitigate this trend, important decisions have been taken by different world organizations and countries to achieve global net-zero emissions. At the European Union level (EU27 countries), two of the main pillars for achieving carbon neutrality are: (1) The “Energy Efficiency First principle” in the formulation of energy policy and in taking relevant investment decisions and (2) the electrification of the energy sector, supported by generating electricity through endogenous renewable energy sources. In this context, a comprehensive review was carried out on what has been developed by the scientific community and main international energy organizations on the electrification of the energy sector. Additionally, with the purpose of better understanding the state of the art of a country regarding the decarbonization process, the Portuguese... [more]

Organic photovoltaic (OPV) solar cells represent an emerging and promising solution for low-cost clean energy production. Being flexible and semi-transparent and having significant advantages over conventional PV technologies, OPV modules represent an innovative solution even in applications that cannot be based on traditional PV systems. However, relatively low efficiencies, poor long-term stability, and thermal issues have so far prevented the commercialization of this technology. This paper describes two outdoor experimental campaigns that compared the operation of OPV modules with traditional PV modules—in particular crystalline silicon and copper−indium−selenium (CIS)—and assessed the OPV modules’ power generation potential in vertical installation and facing towards the cardinal directions.

Contact cooling using thermopressor technologies is a promising direction for the development of energy-efficient technologies. This technology is based on the implementation of the thermo-gas-dynamic compression effect in special contact heat exchangers that consists of increasing the pressure while decreasing the temperature during the evaporation of a finely dispersed liquid injected into a gas flow moving at a speed close to sound. Upon application of the thermopressor for charge air cooling of the engine, the following result was obtained: an increase in the air pressure after the turbocharger by 340 to 480 kPa. The thermopressor can be used as a boost stage after the turbocharger, resulting in the reduction of a basic turbocharger compression work and the increase of engine power output accordingly. Reducing the work allows for the same air flow rate on the internal combustion engine to reduce the compressor power by 10 to 12%. This increases the temperature of the exhaust gases... [more]

Performance guarantees and tests of thermal power plants are usually carried out at 100% rate output capacity. However, fossil-fired power plants have decreased full load hours, affecting energy efficiency, and are subjected to frequent load changes caused by variable renewable electricity and potential grid stability. Therefore, this study is conducted to calculate and draw the characteristic curves for all stable loads of coal-fired power units including the 60%, 75%, and 100% rate output. The study focuses on the corrected plant net heat rates—gross unit outputs, net standard coal consumption rates—throttle steam pressures, and corrected plant net efficiencies—carbonic emission rates. In addition, the experimental investigation for energy efficiency and carbonic emission of the latest larger-scale (+600 MW) coal-fired power generation units in Vietnam are also implemented using a performance guarantee calculation software called “PG_Cal” version 0.0, which is based on a mass and ene... [more]

Over the last few years, new materials have been developed which a priori, appear to improve passive energy efficiency in buildings. This article focuses on chromogenic devices that allow changing their optical properties in a reversible manner through some external stimulus. The covering of the envelopes may have different textures or colors, which determine the amount of solar radiation absorbed by the material compared to the incident radiation. In buildings with a high percentage of roof relative to façade, the surface finish plays an interesting role in the energy demand. In the present work, the influence of the application of thermochromic materials to the roofs of commercial buildings is analyzed. It has been demonstrated that the application of a thermochromic surface finish can produce savings of annual energy demand between 1% and 12% in kilowatt-hours and kilograms of CO2 and they become more significant for construction solutions with higher transmittances values. Then, th... [more]

An important instrument for achieving smart and high-performance buildings is Machine Learning (ML). A lot of research has been done in exploring the ML models for various applications in the built environment such as occupancy prediction. Nevertheless, the research focused mostly on analyzing the feasibility and performance of different supervised ML models but has rarely focused on practical applications and the scalability of those models. In this study, a transfer learning method is proposed as a solution to typical problems in the practical application of ML in buildings. Such problems are scaling a model to a different building, collecting ground truth data necessary for training the supervised model, and assuring the model is robust when conditions change. The practical application examined in this work is a deep learning model used for predicting room occupancy using indoor climate IoT sensors. This work proved that it is possible to significantly reduce the length of ground tr... [more]

A collection of twelve papers published in Energies, in a Special Issue on “Building Energy Audits-Diagnosis and Retrofitting”, was bound together and published in 2021, focusing on the built environment. The aim was to systematically collect and analyze relevant data for obtaining adequate knowledge on the energy use profile of buildings, and was extended for the sustainability assessment of the built environment. To date, all papers have been very well received, attaining a total of 97 citations and over 15,300 views. The papers addressed historic and various building types, baselines for non-residential buildings from energy performance audits and from in-situ measurements, monitoring and data analysis, assessment of indoor environmental quality, model calibration and verification of energy savings, along with an urban audit and rating method for assessing the sustainability of the built environment. Following on from the success of this Special Issue, the decision was made to reope... [more]

In this paper, a review of the adoption status of energy efficiency and renewable energy technologies is presented, specific to US residential buildings. Various technologies are reviewed and categorized as either their relative “higher adoption” or “lower adoption” rates within the US housing stock. More importantly, the review analysis investigates the main factors associated with their high or low adoption rates. Specifically, the paper provides a background of the historical progression of energy efficiency programs as well as sustainability certifications and standards for buildings. The review then analyzes specific building energy efficiency and renewable energy technologies applied to US residential buildings and their adoption rates. The review analysis indicates that building technologies are more frequently adopted for multiple reasons including requirements by codes and standards, incentives through green certifications, low implementation costs, and acceptance and populari... [more]

In the late 19th century, the three-phase induction motor was the central element of productivity increase in the second industrial revolution in Europe and the United States. Currently, it is the main load on electrical systems in global terms, reaching approximately 70% of electrical energy consumption in the industrial sector worldwide. During the 20th century, electric motors underwent intense technological innovations that enabled significant performance gains. Thus, this work analyses the performance changes in squirrel-cage rotor three-phase induction electric motors (SCIMs) with mechanical powers of 3.7 kW, 37 kW, and 150 kW and speed ranges corresponding to two poles and eight poles, connected to a low voltage at a frequency of 60 Hz and tested between 1945 and 2020. The study confirms accumulated performance gains of above 10% in some cases. Insulating materials for electrical conductors have gone through several generations (cotton, silk, and currently, varnish). Improvement... [more]

The paper discusses existing trends and prospects for decarbonization in the Commonwealth of Independent States (the CIS), an international organization that regroups Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Turkmenistan, and Uzbekistan. The CIS occupies a significant share of Eurasia, representing a large share of global energy consumption and production with a corresponding carbon footprint. These countries and their decarbonization prospects are rarely discussed in the English-language scientific literature. This paper fills in this gap by offering a comprehensive analysis based on statistical data, policy documents, and scenario-based future projections. The results underline that revisiting Nationally Determined Contributions, increasing energy efficiency, and decoupling GDP growth from greenhouse gas emissions are essential to the implementation of the Paris Agreement. The future energy mix should include larger shares of renewable energy... [more]

According to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment report, energy-efficient appliances can reduce global electricity consumption even though there is an expected increase in the number and ownership of appliances. The International Energy Agency (IEA) expects a high increase in energy efficiency in traditional appliances (refrigerators, washing machines, television, etc.), and in the number of new appliances installed (also called plug loads). The bibliometric study of publications related to energy-efficient appliances carried out in this paper shows that research on this topic is growing in developed regions (North America and Europe) and even more in some developing regions (Asia Pacific) with a high emphasis on China and India. The results indicate that, in general, policies are always implemented before the core of publications on the topic, with time spans ranging from 3 to 30 years. However, the trend seems to be changing with publications related t... [more]

A company’s productivity and success measure its effectiveness. This article presents the problem of economic efficiency and aspects related to environmental protection. The basic parameters analysed were the engine type and how it affects the environment. Over three months, the analysis was carried out and used the data envelopment analysis. As a result of the research carried out, the comparison of the amount of fuel used with the amount of transported goods should answer the following questions: What type of engine should be ordered for new trucks to show the best efficiency during operation? What is the efficiency of the currently used engines? How do they affect the environment? The method proposed in the article makes it possible to define the initial requirements for the definition of truck units, which is included in the conclusions of this paper.

This article aims to present changes in the use of electricity by service companies, resulting from regulations within the framework of increasing energy efficiency from the perspective of the implementation of the European Green Deal strategy. To achieve the above goal, the following research question was formulated: to what extent did the COVID-19 pandemic affect the implementation of energy transformation and electricity consumption among the surveyed group of recipients? It should be noted that, so far in the global environment, more and more electricity has been used every year, and this tendency is still continuous and growing. Therefore, in European Union countries, measures have been taken to balance demand and its rational use, resulting from the implementation of the European Green Deal strategy. According to the strategic goal of the indicated policy, EU countries are obliged to implement a sequence of actions enabling their transformation into a modern, resource-efficient,... [more]

Drivers for industrial energy efficiency are factors that promote the sustained adoption of energy-efficient measures and practices. Leveraging drivers to overcome barriers and encourage action which improves industrial energy efficiency can contribute to closing the energy efficiency gap. In fossil-fuel-based systems, this will also contribute to greenhouse gas abatement. A systematic literature review was used to investigate how knowledge about drivers is generated and whether prevalent drivers can be mapped to existing taxonomies. The systematic literature review confirmed that surveys and/or interviews with managers from countries who are members of the Organisation for Economic Cooperation and Development (OECD) are the most common way to gather data on drivers for industrial energy efficiency. This means the extant knowledge on drivers may be incomplete because contributions from some stakeholders, industry types and company sizes may be missing. The review also found economic dr... [more]

THe energy-efficient operation of microgrids—a localized grouping of consuming loads (domestic appliances, EVs, etc.) with distributed energy sources such as solar photovoltaic panels—suggests the deployment of Energy Management Systems (EMSs) that enable the actuation of controllable microgrid loads coupled with Artificial Intelligence (AI) tools. Such tools are capable of optimizing the aggregated performance of the microgrid in an automated manner, based on an extensive network of Advanced Metering Infrastructure (AMI). Modular adaptable/dynamic building envelope (ADBE) solutions have been proven an effective solution—exploiting free façade areas instead of roof areas—for extending the thermal inertia and energy harvesting capacity in existing buildings of different nature (residential, commercial, industrial, etc.). This study presents the PLUG-N-HARVEST holistic workflow towards the delivery of an automatically controllable microgrid integrating active ADBE technologies (e.g., PVs... [more]

Among all the activities in a society, construction has a key role in environmental, social, and economic pillars. Construction is also responsible for a considerable amount of waste production, energy consumption, pollutant gas emissions, and consumption of nonrenewable natural resources. Regarding energy consumption, a high demand for building operational energy has been observed in the last decades due to the more demanding requirements of the users with a continuous search for better thermal comfort in their homes, namely in developed countries. In Portugal, for instance, more than 20% of the electricity consumed is related to residential buildings, which is based on CO2 emissions and other pollutants that negatively affect the environment. Much of this consumed energy is a result of the HVAC systems installed inside buildings to provide users with thermal comfort. One exciting opportunity to mitigate buildings’ operational energy consumption while contributing to thermal user comf... [more]