131 research outputs found
Procjena optimizacijskog potencijala postavki dinamičke kontrole solarnih kombi-sustava pomoću računalnih simulacija
Before improving the control settings of solar heating systems with the help of sophisticated predictive algorithms, it is reasonable first to determine or at least estimate the theoretical potential of these improvements and then to decide if they are worthy of implementation. An approach is proposed in this paper which enables the estimation of the theoretical potential of the dynamic control settings optimization for solar heating combisystems. Dynamic optimization was carried out for a solar combisystem with a solar fraction of approximately 35% for the period of an entire year. The theoretical potential of the optimization of the boiler controller settings as well as the fluid mass flow in the collector loop and, consequently, in store loop, was estimated. The solar thermal combisystem was simulated in TRNSYS and optimization was carried out by the binary (n-ary) search algorithm programmed in GenOpt (Generic optimization software). The results showed that the extended fractional savings for the considered combisystem with dynamically optimized mass flow in the collector loop was only 0.3 percent points larger than that for the system with an optimized, but fixed mass flow. The optimization potential of the boiler controller settings turned out to be more promising, showing an improvement of 4.4 percentage points in thermal fractional savings for the system with two instant electrical heaters versus the initial system with a heated volume in the store.Prije poboljšanja kontrolnih postavki solarnog toplinskog sustava pomoću sofisticiranih prediktivnih algoritama, potrebno je prije odrediti ili procijeniti teoretski potencijal tih poboljšanja. U ovom radu je prikazan pristup koji omogućava procjenu teoretskog potencijala optimizacije postavki dinamičke kontrole za solarne kombi-sustave. Dinamička optimizacija je vršena za solarni kombi-sustav sa solarnim udjelom od 35% tokom cijele godine. Teoretski potencijal optimizacije postavki kontrole spremnika, kao i protok radnog fluida u kolektorskom krugu. Solarni toplinski kombi-sustav je simuliran u programu TRNSYS i optimizacija je vršena binarnim pretraživačkim algoritmom programiranom u GenOpt programu (Generic optimization software). Rezultati pokazuju da je ušteda na promatranom kombi-sustavu sa dinamički optimiziranim masenim protokom u solarnom krugu tek 0.3% veća nego kod istoga sustava sa optimiziranim, ali fiksnim masenim protokom radnog fluida. Optimizacijski potencijal postavki kontrole spremnika je pokazao bolje rezultate, postigavši 4.4% veću uštedu toplinske energije za sustav sa dva električna grijača
Otkrivanje i dijagnoza kvarova u velikim solarnim toplinskim sustavima
A four-step concept for fault detection and fault diagnosis for solar thermal systems has been developed in the framework of the ongoing research activities at Kassel University. This concept is able to combine different general approaches for fault detection and fault diagnosis in one structure. Additionally it introduces a systematic categorization of information and a more precise terminology by distinguishing between element sensor values, measured values, features and symptoms.Koncept u četiri koraka za otkrivanje i dijagnozu kvarova (FDD) u velikim solarnim toplinskim sustavima je razvijen u okviru tekućih istraživačkih aktivnosti na Sveučilištu Kassel. Ovaj koncept kombinira različite opće pristupe za otkrivanje i dijagnozu kvarova u jednoj strukturi. Osim toga, uvodi se sustavna kategorizacija podataka i preciznija terminologija prema razlikovanju između veličina dobivenih iz osjetnika, mjerenih veličina, svojstava i simptoma za pojedine elemente sustava
Der Krieg in der Ukraine - Die Vorstellungen und Emotionen von Schülerinnen und Schülern
Dieser Beitrag stellt die Ergebnisse einer qualitativen Studie mit Schülerinnen und Schülern zu ihren Vorstellungen, Emotionen und Meinungsbildungsprozessen mit Bezug auf den Ukraine-Krieg dar. Zusätzlich werden mit dem Krieg in Verbindung stehende und für die Politikdidaktik relevante Themenbereiche diskutiert und ein Ausblick auf mögliche didaktische Anknüpfungspunkte gegeben
Techno-economic evaluation of electricity price-driven heat production of a river water heat pump in a German district heating system
Large scale heat pumps (HP) are an important technology that will link district heating (DH) systems to the electricity sector in future smart energy systems. This paper examines the feasibility of the integration of a river water HP at a combined heat and power plant in Germany. It is part of a more extensive study about the transformation of a DH system in an urban district towards a 4th generation DH system. The focus is on operational characteristics and economic efficiency of electricity price-driven heat production. A novel method for estimating the coefficient of performance (COP) of two-stage ammonia HPs based on the difference between sink and source temperature is presented. The HP achieves a seasonal COP in the range of 3.4 to 3.7. The 15-year simulation with the software energyPRO shows that electricity-price driven operation is especially relevant for lower heat loads during the non-heating season. The correlation between volatility of electricity market price change and flexible operation is analysed. Finally, the levelized cost of heat for four designs with heat outputs of the HP from 4.7 MWth to 6.1 MWth and increasing storage sizes are compared. The results indicate that electricity costs are reduced in more flexible systems, but cost parity to the minimum dimensioning is not yet reached with the underlying economic framework conditions. However, the parameters that benefit the economic efficiency of more flexible systems are discussed
Entwicklung eines Verfahrens für die Wirtschaftlichkeitsberechnung solarthermischer Anlagen: die LCOH Methode
SolNet:PhD-scholarships and courses on solar heating
AbstractSolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference-accompanying Master courses, placements of internships, and PhD scholarship projects. A new scholarship project, “SHINE”, will be launched in autumn 2013 in the frame work of the Marie Curie program of the European Union (Initial Training Network, ITN). 13 PhD-scholarships on solar district heating, solar heat for industrial processes, as well as sorption stores and materials will be offered, starting in December 2013. Additionally, the project comprises a training program with five PhD courses and several workshops on solar thermal engineering that will be open also for other PhD students working in the field. The research projects will be hosted by six different universities and five companies from all over Europe
Microvesicles from indoxyl sulfate-treated endothelial cells induce vascular calcification in vitro
Vascular calcification (VC), an unpredictable pathophysiological process and critical event in patients with cardiovascular diseases (CVDs), is the leading cause of morbi-mortality and disability in chronic kidney disease (CKD) patients worldwide. Currently, no diagnostic method is available for identifying patients at risk of VC development; the pathology is detected when the process is irreversible. Extracellular vesicles (EVs) from endothelial cells might promote VC. Therefore, their evaluation and characterization could be useful for designing new diagnostic tools. The aim of the present study is to investigate whether microvesicles (MVs) from endothelial cells damaged by uremic toxin and indoxyl sulfate (IS) could induce calcification in human vascular smooth muscle cells (VMSCs). Besides, we have also analyzed the molecular mechanisms by which these endothelial MVs can promote VC development. Endothelial damage has been evaluated according to the percentage of senescence in endothelial cells, differential microRNAs in endothelial cells, and the amount of MVs released per cell. To identify the role of MVs in VC, VSMCs were treated with MVs from IS-treated endothelial cells. Calcium, inflammatory gene expression, and procalcification mediator levels in VSMCs were determined. IS-treated endothelial cells underwent senescence and exhibited modulated microRNA expression and an increase in the release of MVs. VSMCs exposed to these MVs modulated the expression of pro-inflammatory genes and some mediators involved in calcification progression. MVs produced by IS-treated endothelial cells promoted calcification in VSMCs
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