1,721,012 research outputs found
Experimental investigation and optical visualization of a salt gradient solar pond integrated with PCM
No full textThe thermal performance of a solar pond is affected by the amount of heat lost to the ground through the lower convective zone (LCZ) in which the heat is stored. Studies are focused on decreasing the heat losses, to maximize the energy stored and guarantee the stability of the thermohaline system over time. Phase change materials (PCMs) can help to achieve all these goals, since they work as thermal energy storage (TES), exploiting the latent heat absorbed during the solid-liquid phase change. This paper presents an experimental application of PCMs in the LCZ of a small solar pond. The paraffin wax was enclosed in aluminium cylinders which have been arranged on the bottom. The temperature of the solution in deep is monitored both with and without the PCM. The stability of the pond is analyzed through a laser shadowgraph technique, to visualize the effect of the thermal convection on the interfaces. Results show that the LCZ of the solar pond with PCM is around 3 °C colder than the reference case after a 6-h heating period. The shadowgraph analysis proves that the thermal convection in the reference case is stronger and damage the interface until break. The monitoring of the solar pond with PCM shows an improved stability
Technical analysis and economic evaluation of a complex shore-to-ship power supply system
No full textIn port areas, with the progressive increase in maritime traffic, the problem of pollution is crucial especially when the port is near to an urban area. The cold ironing allows a reduction of pollutants satisfying the power demand of ships while they are at berth, replacing on board diesel engines. In this paper, the methodology of analysis of the electrical loads required by ships concerns the typical week of each month over a one year period. The power is provided by a cogeneration plant powered by natural gas. It is flanked by a Compressed Air Energy Storage system since the energy demand is linked to the presence of ships in port and so very variable over time. The heat waste is recovered in a heating district network for overall optimization. At last, the economical aspect has been evaluated to prove the feasibility of the whole system. The results, for the case of the port of Ancona, show that a 1.5 MW and 2 MW cogenerator covers the 83.05% and 92.5% of the electrical need of ships respectively, and the 61% and 74% of the thermal need of buildings over the period analysed. The coverage of the CAES system is not influenced by the rated power
Local energy production scenarios for emissions reduction of pollutants in small-medium ports
No full textEnvironmental impact produced by ships in ports is a relevant problem, especially when they are located close to urban areas. This paper, taking Ancona (Italy) as a case study, analyzes the CO2 (and other chemical species) emissions produced by the auxiliary engines of ferry ships at berth. Three different configurations have been investigated, one grid-connected and two with local power plants. Cogenerative and photovoltaic scenarios have been considered varying the power size and the presence of a storage system. A computational model, based on maritime traffic and meteorological data over a one-year period, returns the percentages of the energy covered by the plant, the grid and the storage system. Environmental analysis shows that the grid-connected cold ironing scenario reduces the CO2 emissions by 34.5% compared to on-board diesel generators emissions. Cogeneration systems reduce CO2 emissions by 60–62%, while photovoltaic ones around 39%. All scenarios prove to be economically feasible
Utilizzo dell’energia solare per la dissalazione: integrazione di un lago solare con un dissalatore basato su principi termici
No full textNell’ambito delle attività di ricerca svolte presso il Dipartimento di Energetica dell’Università di Ancona, sull’utilizzo delle energie rinnovabili tramite laghi solari, e presso il Dipartimento di Ingegneria Nucleare e Conversioni di Energia dell’Università di Roma “La Sapienza”, sulle problematiche della dissalazione, è in atto una collaborazione scientifica finalizzata ad approfondire i complessi aspetti termofluidodinamici connessi all’integrazione di un lago solare a gradiente salino con un dissalatore basato su principi termici, realizzato quasi interamente in titanio. La ricerca ha inoltre come scopo la valutazione della fattibilità ingegneristica e della convenienza economica di una tale realizzazione, oltre alla definizione delle procedure di esercizio più efficienti dell’impianto integrato lago-solare-dissalatore, al variare delle diverse condizioni di funzionamento (temperatura del lago solare, temperatura dell’acqua mare, funzionamento a carico parziale, etc.). Ulteriore prodotto della ricerca sarà lo studio del comportamento del titanio, ampiamente utilizzato nella realizzazione, a contatto con fluidi ad alta corrosività, quali l’acqua di mare e la soluzione salina del lago solare
Optimal sizing of a photovoltaic/energy storage/cold ironing system: Life Cycle cost approach and environmental analysis
Full text linkTraditional cold ironing allows ships to shut down their auxiliary engines, during the berthing time, and to be powered by an on-shore power supply. Traditionally the energy demand is satisfied by electricity form the national grid. Alternatively, a local energy production increases the energetic self-sufficiency of the port areas and reduces the pressure on the national grid with continuous peaks of energy demand. This way the port area can be considered a microgrid, characterized by both energy producers and consumers. This paper presents an optimization model, implemented on MATLAB, to provide the best sizing for a combined photovoltaic/energy storage/cold ironing system. The ferry traffic of the port of Ancona (Italy) has been taken as case study. The proposed model returns the percentage of the energy demand covered, the interactions with the national grid, and the optimal size of the PV plant and the storage capacity basing on a Life Cycle Cost (LCC) approach. Results show that the optimal configurations are 2100 kW and 3600 kW with 5750 kWh (without and with storage system) considering lower initial and operational costs, and 3700 kW and 6400 kW with 17,350 kWh (without and with storage system) hypothesizing higher costs. All scenarios ensure an environmental saving, compared to traditional on-board diesel generators, with 87.4 % maximal CO2 reduction achieved
Preliminary investigations on the effects of low electric current treatment on activated sludge floc structure.
No full textIndoor and Outdoor Performance of an Enhanced Photovoltaic Panel through Graphene/Fins/Phase Change Materials
Full text linkThe operative temperature of a photovoltaic cell influences the electric conversion yield. This can be enhanced by cooling the panel. Among the studied solutions, phase change materials (PCM) exploit latent heat and absorb a large amount of energy at a nearly constant temperature. PCMs suffer from a low thermal conductivity. Under these premises the paper presents a hybrid graphene/fins/PCM cooling system to maximize efficiency gains and thermal recovery. An indoor laboratory characterization, under a solar simulator, compares the proposed model with a reference one (an identical, simple PV module) under fixed environmental conditions. Outdoor tests investigate the performances of the two systems under natural conditions. Indoor results show that the front temperature of the proposed PCM integrated module is averagely 6 °C less, with a peak of 8 °C, than the reference case. This means an increase in the electric yield of about 3%. Outdoor investigations prove that, when the PCM is solid and during the melting phase, the proposed system is averagely 1.12 °C and 4.87 °C colder than the reference case, respectively. The thermal efficiency is 30% and 65%, respectively. Once the melting process is completed, the performance becomes worse, and the hybrid panel is almost 3 °C warmer than the simple panel
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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