4 research outputs found
Revisiting democracy: intersectionality, youth and the imperative of ‘Climate Justice’ – Sardinia’s ‘Europe Day’
No full textConferences can provide a platform to engage the youth in debates about the future of Europe. The Europe Day at the University of Cagliari in Sardinia focuses on themes that speak to Italy’s role in European integration. In the future, it could also deepen the understanding of the youth to the implications of climate change – and motivate young people to address these local, regional, national, European, and global concerns
Heating and air conditioning of battery electric city buses by reversible R744 heat pump modules
No full textStadtbusse weisen einen relativ hohen Energiebedarf zum Heizen und Klimatisieren des Fahrgastraums gegenüber anderen Fahrzeugarten wie Pkws oder Lkws auf, wofür die vergleichsweise große Außenfläche und die häufigen Türöffnungen ursächlich sind. Bei aktuellen batterieelektrischen Stadtbussen mit einem elektrischen Heizer reduziert sich an kalten Tagen mit Umgebungstemperaturen unter 0 °C die Fahrreichweite um etwa 50 %. Eine Wärmepumpe kann die Fahrreichweite in diesen Fällen deutlich erhöhen, wobei die derzeit eingesetzten Kältemittel R134a und R1234yf eine eingeschränkte Heizeffizienz aufweisen und darüber hinaus aus ökologischen Gründen umstritten sind. Mit dem natürlichen Kältemittel R744 (Kohlenstoffdioxid, CO2) werden diese Defizite aufgehoben. Ein modulares Wärmepumpen- und Klimaanlagensystem ermöglicht in einem Stadtbus die Verwendung von Pkw-Komponenten. Die Anzahl der Module kann bei den lokal begrenzten Einsatzgebieten von Stadtbussen an die jeweiligen Kundenbedürfnisse und klimatischen Bedingungen angepasst werden. Durch Skaleneffekte der Komponenten aus der Pkw-Produktion ist zudem von einer Erhöhung der Wirtschaftlichkeit auszugehen. Im Rahmen der vorliegenden Arbeit werden autarke, umschaltbare R744-Wärmepumpenmodule für Stadtbusse auf Basis von Pkw-Komponenten hinsichtlich der optimalen Modulanzahl und der Energieeffizienz wissenschaftlich untersucht. Bisher liegen keine wissenschaftlichen Untersuchungen zu modularen Konzepten in der Fahrzeugklimatisierung vor. Darüber hinaus werden die Heiz- und Kühlbedarfe des Innenraums bei realitätsnahen Einsatzszenarien analysiert und daraus Minimalanforderungen für batterieelektrische Stadtbusse abgeleitet. Diese Ergebnisse werden zur Bewertung der R744-Module herangezogen. Mit dem konzipierten Prototypen eines R744-Moduls wird die Funktionsfähigkeit nachgewiesen und Messungen zur Validierung eines Simulationsmodells durchgeführt. Das Simulationsmodell des R744-Prototypenmoduls liefert eine gute Übereinstimmung mit den Messdaten. Im Modell werden anschließend weitere Optimierungsmaßnahmen umgesetzt und darauf aufbauend die Maximalleistungen ermittelt sowie eine energieeffiziente Regelungsstrategie hergeleitet. Die Simulationsuntersuchungen haben gezeigt, dass im Heizfall bei geringen Lasten die aktive Anzahl an Modulen zugunsten eines energieeffizienteren Betriebs zu reduzieren sind, während im Kühlfall alle Module zu betreiben sind. In den Referenzstädten München, Stockholm, Ankara und Dubai sind drei Module zum Heizen und Kühlen eines charakteristischen Stadtbus-Innenraums für ein typisches Betriebsjahr erforderlich. Für Granada werden zwei Module und für Moskau vier Module benötigt. Die Fahrreichweite eines batterieelektrischen Stadtbusses kann im Heizfall bei -15 °C Umgebungstemperatur mit drei R744-Modulen um bis zu 52 % gegenüber einer R134a-Wärmepumpe mit elektrischem Heizer erhöht werden. Im Jahresenergievergleich dieser Technologien werden in den genannten gemäßigten bis kalten Referenzstädten 25 % des elektrischen Stroms zum Heizen und Klimatisieren und somit entsprechend Treibhausgas-Emissionen eingespart. Die vorgestellten R744-Wärmepumpenmodule auf Basis von Pkw-Komponenten stellen eine mögliche Schlüsseltechnologie zur Effizienzsteigerung und Verbreitung von batterieelektrischen Stadtbussen für einen Großteil der weltweiten urbanen Klimaregionen dar.City buses exhibit relatively high energy demands for heating and air conditioning the passenger cabin compared to other types of vehicles such as cars or trucks. This is due to the large external area and the frequent door openings. Heating a current battery electric city bus on cold days with ambient temperatures below 0 °C will reduce the driving range by approximately 50%. For this application a heat pump can increase the driving range significantly. The currently used refrigerants R134a and R1234yf have limited heating efficiency and are also topics of controversy due to their negative environmental impact. With the natural refrigerant R744 (carbon dioxide, CO2) these issues are resolved. A modular heat pump and air conditioning system makes it possible to use passenger car components in a city bus. The number of modules can be adapted to customer requirements and the climatic conditions determined for the locally limited areas where city buses are operational. Economies of scale will be achieved by using components from the passenger car industry. In the present work independent reversible R744 heat pump modules for city buses based on passenger car components are scientifically investigated with regard to the ideal number of modules and energy efficiency. So far, no scientific studies on modular concepts in vehicle HVAC systems are known. In addition, the heating and cooling demands of the cabin in realistic use cases are analysed and their minimum is deduced for battery electric city buses. This is used to evaluate the R744 modules. With the designed prototype of a R744 module the functionality is verified and measurements are taken to validate a simulation model. The simulation model of the R744 prototype module shows good correlation to the measurement data. Further optimisation steps are implemented in the model and, based on this, the maximum performance is determined and an energy-efficient control strategy is derived. The simulation studies have shown that in heating mode the active number of modules is reduced at low energy demands to ensure energy-efficient operation, while in cooling mode all modules should be activated. In the reference cities of Munich, Stockholm, Ankara and Dubai, three modules for heating and cooling a characteristic city bus cabin are required for a typical year of operation. Two modules are needed in Granada and four modules in Moscow. The driving range of a battery electric city bus can be improved in heating mode at -15 °C ambient temperature by up to 52% with three R744 modules compared to an R134a heat pump with electric heater. The comparison of annual energy consumption in the abovementioned moderately cold to cold reference cities shows that 25% of the electricity for heating and air conditioning as well as corresponding ratios of greenhouse gas emissions are saved. The presented R744 heat pump modules based on passenger car components represent a potential key technology for increasing the efficiency and market share of battery electric city buses for a large part of the world’s urban climate regions
Nocturnal secretion of TSH and ACTH in male patients with depression and healthy controls
No full textprofound alterations of the hypothalamic-pituitary-thyroid (HPT) and the hypothalamic-pituitary-adrenal (HPA) systems at the hypophyseal level have been described in affective disorder. To precisely characterize the basal alterations of both axes during sleep. we simultaneously investigated sleep EEG and the secretion of thyrotropin. ACTH and cortisol in nine drug-free male patients with depression in comparison to 10 healthy age and sex matched controls. In depressed patients the nearly diametrical nocturnal secretion of thyrotropin and ACTH was disturbed by significantly blunted thyrotropin values (TSH AUC 51.96+/-5.68 vs. 87.23+/-13.63. P<0.05) and elevated ACTH values (ACTH AUC 1804+/-161 vs. 1538+/-130. P<0.05) compared to controls. Moreover, cross correlation analysis revealed a highly negative association of 0 lag between thyrotropin and ACTH and between thyrotropin and cortisol in the control sample, indicating a physiological nocturnal negative correlation of HPT and HPA system. In the patients sample these associations were weak and reached not statistical significance. Therefore, as a descriptive tool, the ratio TSH/ACTH revealed a significant group difference between controls and patients in the first half of the night (TSH/ACTH AUC 6.50+/-0.42 vs. 3.35+/-0.31. P<0.05). Sleep-EEG analysis showed a shortened REM latency, a decrease of stage 2 and an increase of awake time in the patients. Our data support the hypothesis that both hypophyseal hormones reflect a common dysregulation of both systems in depression probably due to impaired action of TRH-related corticotropin-release- inhibiting-factor (CRIF). The ratio TSH/ACTH might be a tool to characterize alterations of both the HPT and HPA axis in depression during the first half of the night, (C), 2002 Elsevier Science Ltd. All rights reserv
IEA HPT Annex 54: heat pump systems with low-GWP refrigerants ; country report: Germany
No full textThis report provides a comprehensive, most up-to-date review of current research and the development of systems and their optimizations using low-GWP refrigerants for heat pump applications. It also includes a state-of-the-art review of life cycle evaluations of such systems using low-GWP refrigerants. It summarizes the collective efforts by researchers, engineers, and regulation committees across the industry. The report is comprised of the following chapters.
Chapter 1 provides two representative studies from teams in the United States. The first part summarizes the activities related to establishing a detailed database of alternative lower GWP refrigerants for various HVAC&R applications, including thermodynamic and transport properties. The goal is to identify the most suitable candidates for replacing traditional refrigerants based on thermodynamic performance and environmental benefits. It also considers the extent of potential system adjustments required to accommodate the new alternative refrigerants. The second part provides a comprehensive investigation of unitary air conditioners' life cycle climate performance. The review focused on life cycle climate performance methodologies, impacts of parameter and methodology selections, and a few representative case studies.
Chapter 2 provides a comprehensive update on research and development activities in Italy. Three research entities report their progress on low GWP refrigerants and their applications in various heat pump systems. The chapter covers condensation and boiling heat transfer coefficients measurements, and multiple experimental-oriented projects on long-term evaluations of novel heat pump systems using low GWP refrigerants.
Chapter 3 mainly describes the work in Japan, the first step of a two-step process on life cycle climate performance evaluation of heat pump-type air conditioners with next-generation refrigerants. It also presents an overview of a project to establish a new concept and hypothesis for life cycle climate performance evaluation, in which field data related to air conditioners is adopted.
Chapter 4 presents a study carried out by the France teams on finned tube heat exchangers using low GWP refrigerants. The study assessed the heat transfer performance during evaporation and condensation of R410A, R454B, and R32 in a finned tube heat exchanger. A 30-kW experimental setup was built to assess the heat exchanger performance with these three refrigerants. The simulations show that the same design of the finned tube heat exchanger can be used for R410A and R454B, but a design optimization is necessary with R32.
Chapter 5 presents a high-level summary of R&D progress across multiple institutions in Germany. Part one is a summary of the most recent large-scale heat pump monitoring project, a review of ongoing heat pump projects based on an analysis of the enArgus database, and a survey on heat pumps and their refrigerants as part of the market incentive program coordinated at the Federal Office for Economic Affairs and Export Control. In part two, within the last five years, the activities for heat pump research have changed. The activities cover more fundamental research up to the application of deployable heat pump demonstrators for white goods (e.g., dishwashers), mobile systems for electric-driven buses, or large capacity heat pumps systems for multi-family houses.
This report aims at providing a much-needed review and updates on component R&D using low-GWP refrigerants for heat pump applications. We hope it can be a good reference for researchers, engineers, and policymakers across the HVAC industry. We greatly appreciate the contributions of authors for each chapter. The report would not exist without their valuable efforts
