Persona: Valdés Fernández, Manuel Tomás
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Valdés Fernández
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Manuel Tomás
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Publicación Comparison of Different Technologies for Integrated Solar Combined Cycles: Analysis of Concentrating Technology and Solar Integration(MDPI, 2018-04-25) Sánchez, Consuelo; Abbas, Rubén; Muñoz Antón, Javier; Ortega, Guillermo; Rovira de Antonio, Antonio José; Valdés Fernández, Manuel Tomás; Barbero Fresno, Rubén; Montes Pita, María José; Muñoz Domínguez, Marta; Varela Díez, FernandoThis paper compares the annual performance of Integrated Solar Combined Cycles (ISCCs) using different solar concentration technologies: parabolic trough collectors (PTC), linear Fresnel reflectors (LFR) and central tower receiver (CT). Each solar technology (i.e. PTC, LFR and CT) is proposed to integrate solar energy into the combined cycle in two different ways. The first one is based on the use of solar energy to evaporate water of the steam cycle by means of direct steam generation (DSG), increasing the steam production of the high pressure level of the steam generator. The other one is based on the use of solar energy to preheat the pressurized air at the exit of the gas turbine compressor before it is introduced in the combustion chamber, reducing the fuel consumption. Results show that ISCC with DSG increases the yearly production while solar air heating reduces it due to the incremental pressure drop. However, air heating allows significantly higher solar-to-electricity efficiencies and lower heat rates. Regarding the solar technologies, PTC provides the best thermal results.Publicación Are Younger Students More Likely to Drop Out? Spanish Evidence on the Moderator Role of Gender and Social Origin(WILEY, 2024) Requena y Díez de Revenga, Miguel; Valdés Fernández, Manuel TomásEarly school leaving (ESL) is considered one of the most serious problems in the functioning of European education systems. In particular, Spain has traditionally exhibited one of the largest ESL rates in Europe. This study aimed to shed light on the role of the month of birth as a factor conditioning the probability of ESL. Using high-quality census data and a regression discontinuity design, we documented that Spanish males from lower social strata born before the school-entry cut-off are substantially more likely to be observed as early school leavers than their counterparts born after that date. We do not find such effect among females or males from other social strata. Overall, educational policy should target more seriously the inequalities associated with the month of birth as they do not vanish before affecting relevant decisions such as leaving education early, at least for males from lower social strata.Publicación The STEM leaky pipeline at labor market entry in Spain: The role of job competition and social origin(ELSEVIER, 2024) Valdés Fernández, Manuel Tomás; Solga, Heike; https://orcid.org/0000-0002-1589-4380The underrepresentation of women in STEM (Science, Technology, Engineering, and Mathematics) majors is well documented. Using high-quality Spanish data, this study examines whether female STEM graduates are less likely to pursue STEM careers than their male counterparts and considers the moderating role of labor market conditions and social origin. We find a pronounced gender effect in initial and subsequent job placement (4–5 years after graduation). Notably, female STEM graduates are less likely to work in STEM occupations, even if they started their careers in STEM. Exploiting the significant impact of the Great Recession on the Spanish labor market, our study reveals a significantly larger gender effect among individuals who graduated during the crisis compared to those who graduated during the subsequent economic recovery. Thus, job competition influences the magnitude of the gender effect. Finally, our intersectional analysis of gender and social origin suggests that the gender difference is larger among STEM graduates from low-SES backgrounds.Publicación Can a low emission zone improve academic performance? Evidence from a natural experiment in the city of Madrid(Springer, 2025-01-25) Valdés Fernández, Manuel Tomás; Cañizares Espadafor, María del Mar; Conte Keivabu, Risto; https://orcid.org/0000-0002-0623-1841In the last decades, various policies have been implemented to reduce air pollution exposure and improve public health outcomes. Among these, low emission zones (LEZs) have been shown to effectively enhance air quality and health outcomes. However, their potential positive externalities on other outcomes, such as academic performance, remain largely unexplored. This study examines the LEZ introduced in the city of Madrid in late 2018 and investigates its impact on the academic performance of students schooled in the designated area. Using a difference-in-differences design, we demonstrate the policy’s effectiveness in improving air quality during its first 4 years. Subsequently, we find a significant increase of 0.20 standard deviations in the average EvAU scores (a high-stakes examination for university admission) among high schools located within the LEZ, a critical advantage for students seeking entry into the most competitive university programmes. Notably, our findings reveal positive spillover effects in the surroundings of the LEZ area and a greater improvement with longer and earlier exposure to cleaner air. Overall, this study offers compelling evidence of the educational benefits resulting from the implementation of a low emission zone that successfully improves air quality.Publicación Sticky educational expectations: A cross-country comparison(Elsevier, 2021-10) Bernardi, Fabrizio; Valdés Fernández, Manuel TomásThis work studies the cross-country variability in the interaction effect between academic achievement and social origin on the configuration of the expectation of enrolment in the academic track of upper secondary education. Drawing on the Relative Risk Aversion Theory and the Compensatory Advantage model, we anticipate that academic achievement and social origin interact so that high-SES students’ expectations are irresponsive to low academic achievement. We call this phenomenon “stickiness in expectations”. However, we expect to observe sticky educational expectations of high-SES students particularly in those countries where the transition into the academic track of upper secondary education is consequential for their social status maintenance. To test this hypothesis, we use 2018 PISA data for 11 OECD countries and carry out a two-stage regression analysis. We estimate stickiness in expectations for each country using a counterfactual decomposition method. We then regress the country-specific estimate of stickiness in educational expectations on macro-level indicators of the risk of downward mobility associated with non-enrolment in the academic track and the economic capacity to compensate for low achievement in each country. We find sticky educational expectations in 6 of the 11 countries studied and show that stickiness is larger in those countries where not enrolling the academic track in Upper Secondary Education entails a larger risk of social status demotion for high-SES students.