• Energy Research
• 2021-2025close
• Restricted close

Growing interest of the European Union to introduce new emission regulations seeking to lower the particle cut-off size down to the current limit set at 23 nm, has made crucial to achieve an extensive comprehension on their nature. In this regard, it is necessary to deepen their knowledge under different engine technologies, operating conditions, fuel properties and after-treatment devices and how their measure is affected by the sampling and dilution procedure. This paper provides a study on the sub-23 nm particles emitted from a small direct/port fuel injection, spark ignition engine fueled with gasoline, ethanol and a 30% v/v ethanol/gasoline blend, at different operating conditions. Particles were measured both upstream and downstream of a three-way catalyst. The conditions of the sampling were changed in order to investigate the volatile organic fraction. For this purpose, the exhaust gas sample was diluted through a Particulate Measurement Programme compliant system. The temperature of the first dilution stage and of evaporation chamber were changed to discriminate the volatile compounds by enhancing the condensation and the nucleation processes. An engine Exhaust Particle Sizer was used for the sizing and the counting of the particles in the range 5.6-560 nm. The results show a strong dependence of the sub-23 nm particle emissions from the engine operating condition and the fuel type. A moderate impact of the three-way catalyst was instead observed. Moreover, a significant effect of the dilution parameters in the sampling system was noted pointing out the importance to define an appropriate protocol for the measurement of the sub-23 nm particles.

Abstract Field experiences have shown that sub-synchronous oscillation (SSO) can occur in direct-drive wind farms with VSC-HVDC systems. Due to the complexity of the detailed wind farm model, a dynamic equivalent model, with a reasonable order reduction of the detailed model and still reflecting inside-wind-farm and wind-farm-grid SSO characteristics is essential. In this paper, based on the principle that similar matrices have identical eigenvalues, the SSO analysis of an N-machine wind farm with VSC-HVDC system is conducted by simplifying it into two single-machine systems. The modeling method of the two single-machine systems is presented. Four case studies are presented to verify the effectiveness of the proposed model when compared with the detailed model in various scenarios. The proposed model is also benchmarked with the output multiplication-based equivalent model (OMM). Comparison results show that although the system order is reduced significantly, the proposed simplified equivalent model can still reflect inside-wind-farm and wind-farm-grid SSO modes in various scenarios. Meanwhile, the rationality of the OMM in terms of the wind-farm-grid SSO analysis is verified theoretically.

Identifying sustainable factors that impact the intention to purchase organic food was the topic chosen for this study since organic food consumption is a very current subject. In fact, the demand for these unique products has been increasing over the last few years in Portugal and worldwide. The consumption of organic products is globally perceived as beneficial for health and the environment. Furthermore, producing these products values animal welfare and promotes economic development, improving the living conditions of rural populations in more peripheral regions. Thus, the general objective of this research was to contribute to the production of knowledge about the attitudes, preferences, habits, and behaviors of Portuguese consumers about organic food. The data was collected through an online questionnaire between January 9, 2024, and February 6, 2024. A sample consisting of 413 consumers of Portuguese nationality was selected. The average age was 44.7 years old (SD = 11.069), and the median and mode were 47 and 48, respectively. The majority of respondents lived in urban areas (69.2%) of the Bragança (64.0%), Porto (10.4%) and Vila Real (5.1%) districts. Most consumers had a positive level of knowledge about organic food (83.8%) and recognized the European Union organic logo (68.0%). Fresh vegetables (62.7%) and fresh fruits (59.6%) were the most frequently consumed products. These products were usually purchased directly from the producer (50.5%). This research showed that attitudes, environmental concerns, health awareness, and perceived price, in addition to having a positive impact, explained 57.5% of the intention to purchase organic food. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020) and SusTEC (LA/P/0007/2020) info:eu-repo/semantics/publishedVersion

Gli studi svolti sulle comunità energetiche si concentrano sulle relazioni tra consumatori e produttori di energia e l'attenzione viene posta soprattutto sull'energia vista come veicolo di sviluppo locale ed inclusione sociale. Allo stesso tempo, però, il tema del consumo di energia viene declinato anche dagli studi sulla povertà energetica, intesa come impossibilità di accedere alle risorse o di utilizzarle in modo adeguato. Spesso la povertà energetica è legata al concetto di povertà assoluta e rischio sociale, includendo problematiche economiche, sociali e culturali, le persone sperimentano livelli inadeguati di servizi energetici essenziali, causati da fattori multidimensionali, come un'elevata spesa energetica, redditi familiari bassi, edifici inefficienti dal punto di vista energetico, posizione geografica e differenze climatiche ed alti costi dell'energia. Ma se da un lato l'analisi basata su variabili economiche, reddito e spesa delle famiglie, garantisce "oggettività", dall'altro trascura aspetti non direttamente osservabili che attengono alla dimensione e composizione della famiglia, ai comportamenti, allo stato di salute delle persone e alla percezione della propria condizione e del proprio stile di vita. Il fenomeno della povertà energetica è di fatto ancora molto complesso e se le politiche di contrasto sono spesso legate ad un sostegno di tipo economico dato alle famiglie, al contempo diventa fondamentale favorire politiche di promozione ed informazione che possano valorizzare comportamenti ed interventi virtuosi; il capitale sociale definito da McMichael (2011) come "le connessioni tra gli individui, le reti sociali e le norme di reciprocità e fiducia che ne derivano", può rappresentare un valido supporto alle iniziative di contrasto alla povertà energetica, al fine di migliorare l'accesso a fonti energetiche efficienti per contribuire alla creazione di nuove prassi di comportamento positive.

Composting is an aerobic process that involves the decomposition of the urban waste leading, in accordance with the paradigm of the circular economy, to a stabilized final product rich in fertilizer properties. However, adopting this organic fertilizer may encounter significant barriers since many users still associate compost from organic municipal solid waste (OMSWC) with environmental and health hazards like soil contamination and bad odour. In this context, conveying information about compost use and properties with the appropriate communication channels could help overcome misguided beliefs about OMSWC. The present study investigated which drivers would encourage compost adoption and how the frequency of information through specific sources could influence the interest in using compost among potential users. Three main drivers were identified by surveying 59 potential compost users: providing a certification to the product, receiving more information about the origin of the material, and obtaining evidence about its positive effects on soil. Statistical analysis showed a positive association between frequent use of magazines/advertising as an information source and users' interest in adopting compost. In addition, results pointed out that potential users with higher education levels (with bachelor's degree or above) are more likely to use OMSWC than others. In conclusion, the present study suggests that it would be appropriate to redefine targeted communication campaigns to promote the benefits associated with the compost application for agricultural purposes.

Worldwide, the energy consumption of refrigeration systems increased by 50% in the last 20 years. Currently, active refrigeration systems are often used to maintain cold chains in industry. However, there are remarkable drawbacks in the operation of active systems such as susceptibility to blackouts in the power supply and vibrations during their operation. Therefore, to overcome the aforementioned problems, passive cold chain transport using latent thermal energy storage systems arose as a potential solution. However, these systems require long charging times due to the low thermal conductivity of most phase change materials. In that sense, this paper presents a novel design of a cold storage battery with metal foam enhanced phase change material. The peak efflux of energy and solidification time of the battery is correlated as a function of the inlet temperature and mass flow rate of the heat transfer fluid with a root mean square deviation of 11.4%. The solidification time prediction allows determining the geometry which results in the maximum efflux of energy density for a given energy density. Moreover, the cold battery is placed in an insulated container to analyse its performance during transport. Results show that the tested refrigeration battery can act as a standalone refrigeration system during 15 h. However, improvements in the design of the insulated container are suggested to increase the performance of the system along the discharging cycle.

For the design of ground-source heat-pump systems, the local subsoil is an invariant factor. To improve the evaluation of the local heat exchange capability, significant efforts recently have been devoted to identifying the ground thermal conductivity vertical profile. In recent years, an innovative method using hybrid optic fiber cables inserted into the ground has been developed. The technique relies on copper wires that thermally stimulate the ground. Optical fibers measure the temperature variation over time all along the cable at a high spatial and temporal resolution. In this work, the hybrid cable was grouted into a 125-m well located in the Po Plain in Northern Italy. The provided core defined the geological environment as a continuous succession of unconsolidated alluvial deposits of very limited thickness, grouped in 15 different granulometric units. Three enhanced thermal response test (ETRT) data sets were acquired in different seasons; for 5 days of heating followed by 5 days of recovery, the soil temperature was recorded continuously along the well, with a spatial resolution of 1 m. A new approach using a multiple linear regression is proposed to analyze the data sets to distinguish the thermal conductivity of each individual granulometric unit. The obtained thermal conductivity values were compared and discussed considering the standard thermal response test outputs and the thermal conductivity data obtained from direct measurements performed on the cores. The analytical method's reliability stands due to the high repeatability of the obtained results, despite the increased complexity of the treated geological setting.

More and more applications encompass battery energy storage systems (BESSs) based on Li-ion batteries. However, when designing the power converter of a BESS or when studying the interaction between BESSs and other application components, relying on a real battery makes the process cumbersome, expensive, and time-consuming. Moreover, the battery could even suffer damages. The aim of the work is to show that it is possible to exploit suitable battery models and related parameter identification methodologies, as well as power converters and related control techniques, to develop a hardware device that emulates any given battery. In particular, this paper shows the design and the experimental prototype of a Li-ion battery emulator that is capable of both sourcing and sinking power at kilowatt scale. Unlike other similar devices available in the market or described in the technical literature, the proposed device is low-cost, it injects power into the grid during sink operation, and it can also reproduce battery dynamics. Design criteria are given in the manuscript. The proposed battery emulator has been tested and experimentally validated. The obtained device allows reducing the cost, time, and complexity of performing system tests in Li-ion BESS applications.

The challenge of sustainable development and consumption is to satisfy current desires without impoverishing future generations and the planet in the long term. Therefore, new standards of sustainable practices are increasingly being promoted [1]. Environmental knowledge refers to an individual's perception and understanding of environmental issues, including understanding the causes and consequences of environmental problems and knowing the solutions needed to resolve them [2]. In this context, the more people know about environmental issues, their causes, and possible solutions, the more they will be willing to buy sustainable food [3]. This study aimed to determine the level of knowledge about ecological issues in Portuguese citizens with higher education and to analyze the impact of the interest and level of knowledge of environmental issues on the attitude of conscious purchase of food. To achieve these objectives, a quantitative and cross-sectional study was carried out based on a non-probabilistic sample of 295 individuals, selected for convenience. To collect the data, a questionnaire adapted [4] was placed online and shared in the social media between September 2022 and the first half of January 2023. The questionnaire was structured in 2 sections. The first section included questions that allowed the socioeconomic characterization of the respondent, namely, nationality, district of residence, gender, age, marital status, net monthly income of the household, household size and financial comfort. The second section consisted of 17 statements about sustainable food purchasing attitudes and behaviors, for which the respondent used a Likert-type scale ranging from 1 (completely disagree) to 7 (completely agree). Respondents were aged between 18 and 69 years old, recording an average of 32.29 years old (SD = 12.661). The majority lived in the North of Portugal, namely in Porto (24.9%), Bragança (23.5%) and Braga (10.9%) districts. In addition, the majority was female (72.7%), single (64.5%), lived in a household with up to 3 people (64.2%), with a monthly income of up to 1440 euros (54.3%). Despite the household income being relatively low, 63.1% of respondents consider living with some financial comfort. The results showed that respondents recorded a good level of knowledge of environmental issues (Mean = 5.21; SD = 1.436). Moreover, the value of Adjusted R2 shows that the interest and the level of environmental knowledge explain, in 64.2%, the conscious attitudes and behaviors with regard to the purchase of food. These results suggest that the participants of this study, that is, people with higher education adopt planning and organization practices in their food purchases, as well as adhere to and implement sustainable measures. Despite the encouraging results of the present study, in the future, Portuguese higher education institutions should adopt educational and awareness strategies aimed at improving students' knowledge of environmental issues, allowing the adoption of more sustainable behaviors. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020) and SusTEC (LA/P/0007/2020). info:eu-repo/semantics/publishedVersion