scholarly journals A comparative study of model fitting for estimating the overall efficiency of grid-connected photovoltaic inverters

2021 ◽  
Vol 19 ◽  
pp. 350-355
Author(s):  
J. Ramos-Teodoro ◽  
◽  
J. Rodríguez ◽  
M. Pérez ◽  
M. Berenguel
Keyword(s):  
Goodness Of Fit ◽  
Model Fitting ◽  
Operating Conditions ◽  
The Other ◽  
Photovoltaic System ◽  
Case Scenario ◽  
Actual Operating ◽  
Direct Measurements ◽  
Overall Efficiency ◽  
Fitting In

Determining the static overall efficiency of inverters is sometimes necessary for control o design purposes. As getting this information from the manufacturers’ datasheets or certified laboratories might not be always viable, this paper addresses its estimation from direct measurements under actual operating conditions. Particularly, the Sandia Inverter Model has been taken as a paradigm of methodology and adapted to deal with the available data for an office building’s photovoltaic system over the 2013- 2017 period. Two unidimensional and two bidimensional models have been selected and compared to assess their goodness of fit on three inverters of the same kind of which the system consists. The best-case scenario corresponds to an exponential curve fitting, in which the R-square value increases over 0.95, outperforming the other models.

Analysis of the Design and Operation of a Hybrid Trigeneration-Photovoltaic System Installed in a Shopping Mall

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Aldo López Vega ◽  
Carlos Rubio-Maya ◽  
Gregory J. Kowalski ◽  
J. Jesús Pacheco Ibarra
Keyword(s):  
Net Present Value ◽  
Maximum Energy ◽  
Operating Conditions ◽  
Photovoltaic System ◽  
Shopping Mall ◽  
Second Law ◽  
Exergy Destruction ◽  
Present Value ◽  
Actual Operating ◽  
Overall Performance

Abstract In this paper, the analysis of the design and operation of a hybrid trigeneration/photovoltaic system installed in a shopping mall is presented. Thermodynamic models based on the first and second laws are developed to analyze all the system's components individually and integrated all together in a trigeneration scheme. Thermodynamics models were validated through experimental data obtained from the equipment running on site. Once the models were validated, it was possible to analyze the actual operating conditions to determine the suitability of the design configuration and to predict the overall performance of the system. In the analysis of the system's design, the first and second law efficiencies, the exergy of each stream, as well as the exergy destruction in each component are reported. In the analysis of the system's operation, several scenarios under different operating conditions were studied and the most suitable scenario was determined by applying an economic analysis based on the net present value. The results show the configuration on which the maximum energy efficiency of the system is obtained as well as the best operation strategy where the greatest economic savings are achieved.

Distribution of leaf orientations in six conifer species

2001 ◽  
Vol 79 (4) ◽  
pp. 389-397 ◽  
Author(s):  
Hugh J Barclay
Keyword(s):  
Pseudotsuga Menziesii ◽  
Pinus Contorta ◽  
Goodness Of Fit ◽  
Tsuga Heterophylla ◽  
Picea Sitchensis ◽  
The Other ◽  
Thuja Plicata ◽  
Leaf Angle ◽  
Conifer Species ◽  
Abies Grandis

Leaf angle distributions are important in assessing both the flexibility of a plant's response to differing daily and seasonal sun angles and also the variability in the proportion of total leaf area visible in remotely sensed images. Leaf angle distributions are presented for six conifer species, Abies grandis (Dougl. ex D. Don) Lindl., Thuja plicata Donn. ex D. Don, Tsuga heterophylla (Raf.) Sarg., Pseudotsuga menziesii (Mirb.) Franco, Picea sitchensis (Bong.) Carr. and Pinus contorta Dougl. ex Loud. var. latifolia. The leaf angles were calculated by measuring four foliar quantities, and then the distributions of leaf angles are cast in three forms: distributions of (i) the angle of the long axis of the leaf from the vertical for the range 0–180°; (ii) the angle of the long axis of the leaf for the range 0–90°; and (iii) the angle of the plane of the leaf for the range 0–90°. Each of these are fit to the ellipsoidal distribution to test the hypothesis that leaf angles in conifers are sufficiently random to fit the ellipsoidal distribution. The fit was generally better for planar angles and for longitudinal angles between 0° and 90° than for longitudinal angles between 0° and 180°. The fit was also better for Tsuga heterophylla, Pseudotsuga menziesii, Picea sitchensis, and Pinus contorta than for Abies grandis and Thuja plicata. This is probably because Abies and Thuja are more shade tolerant than the other species, and so the leaves in Abies and Thuja are preferentially oriented near the horizontal and are much less random than for the other species. Comparisons of distributions on individual twigs, whole branches, entire trees, and groups of trees were done to test the hypothesis that angle distributions will depend on scale, and these comparisons indicated that the apparent randomness and goodness-of-fit increased on passing to each larger unit (twigs up to groups of trees).Key words: conifer, leaf angles, ellipsoidal distribution.

THE VALUE OF FINE BUBBLE DIFFUSER TESTING UNDER ACTUAL OPERATING CONDITIONS IN A HIGHLY INDUSTRIAL WASTEWATER

2005 ◽  
Vol 2005 (14) ◽  
pp. 2232-2247
Author(s):  
Michael S. Demko ◽  
Frank Coughenour ◽  
John J. Pacifici ◽  
Sam Jeyanayagam ◽  
David T. Redmon
Keyword(s):  
Industrial Wastewater ◽  
Operating Conditions ◽  
Actual Operating ◽  
Fine Bubble

Investigating realistic anode off-gas combustion in SOFC/ICE hybrid systems: mini review and experimental evaluation

2021 ◽  
pp. 146808742110583
Author(s):  
Ioannis Nikiforakis ◽  
Zhongnan Ran ◽  
Michael Sprengel ◽  
John Brackett ◽  
Guy Babbit ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Internal Combustion Engines ◽  
Engine Performance ◽  
High Energy ◽  
Operating Conditions ◽  
Compression Ignition ◽  
Case Scenario ◽  
Gas Combustion ◽  
Thermodynamic Conditions ◽  
Decentralized Energy

Solid oxide fuel cells (SOFCs) have been deployed in hybrid decentralized energy systems, in which they are directly coupled to internal combustion engines (ICEs). Prior research indicated that the anode tailgas exiting the SOFC stack should be additionally exploited due to its high energy value, with typical ICE operation favoring hybridization due to matching thermodynamic conditions during operation. Consequently, extensive research has been performed, in which engines are positioned downstream the SOFC subsystem, operating in several modes of combustion, with the most prevalent being homogeneous compression ignition (HCCI) and spark ignition (SI). Experiments were performed in a 3-cylinder ICE operating in the latter modus operandi, where the anode tailgas was assimilated by mixing syngas (H2: 33.9%, CO: 15.6%, CO2: 50.5%) with three different water vapor flowrates in the engine’s intake. While increased vapor content significantly undermined engine performance, brake thermal efficiency (BTE) surpassed 34% in the best case scenario, which outperformed the majority of engines operating under similar operating conditions, as determined from the conducted literature review. Nevertheless, the best performing application was identified operating under HCCI, in which diesel reformates assimilating SOFC anode tailgas, fueled a heavy duty ICE (17:1), and gross indicated thermal efficiency ([Formula: see text]) of 48.8% was achieved, with the same engine exhibiting identical performance when operating in reactivity-controlled compression ignition (RCCI). Overall, emissions in terms of NOx and CO were minimal, especially in SI engines, while unburned hydrocarbons (UHC) were non-existent due to the absence of hydrocarbons in the assessed reformates.

The Impact of Electric Hybrid Compressor to Make Transport Environmentally Friendly

2013 ◽  
Vol 391 ◽  
pp. 207-212
Author(s):  
Maciej Bajerlein
Keyword(s):  
Energy Consumption ◽  
Operating Conditions ◽  
Vehicle Speed ◽  
Suspension Systems ◽  
Actual Operating ◽  
Vehicle Operation ◽  
Total Energy Balance ◽  
The Impact ◽  
Road Emission ◽  
Speed Engine

This paper presents the investigations, whose aim was to determine the influence of the operation of electric and mechanical compressors on the energy consumption of city buses in public transport. The tests were performed on pneumatic systems used in city transit vehicles whose underlying component is a compressor generating pressure for the brake and suspension systems. Owing to the application of a portable analyzer - SEMTECH DS the emissions (with a secondly resolution) of CO, HC, NOx, CO2 in the exhaust gases were measured. The on-road emission tests were performed in the actual operating conditions in SORT driving tests. These tests reflect the actual vehicle operation in a real task through preset procedures of their realization and measurements determining the energy consumption and exhaust emissions or the influence of the vehicle accessories and all variables (vehicle speed, engine load, acceleration or distance covered) on the total energy balance. The on-road tests were performed on a runway of the Bednary airstrip in Poland.

Ambient Condition Effects on NOx and CO Emissions From Process Heaters

2008 ◽  
Author(s):  
Wesley R. Bussman ◽  
Charles E. Baukal
Keyword(s):  
Atmospheric Pressure ◽  
Ambient Air ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Ambient Conditions ◽  
Fuel Gas ◽  
Natural Draft ◽  
Actual Operating ◽  
Wide Range ◽  
Pollution Emissions

Because process heaters are typically located outside, their operation is subject to the weather. Heaters are typically tuned at a given set of conditions; however, the actual operating conditions may vary dramatically from season to season and sometimes even within a given day. Wind, ambient air temperature, ambient air humidity, and atmospheric pressure can all significantly impact the O2 level, which impacts both the thermal efficiency and the pollution emissions from a process heater. Unfortunately, most natural draft process burners are manually controlled on an infrequent basis. This paper shows how changing ambient conditions can considerably impact both CO and NOx emissions if proper adjustments are not made as the ambient conditions change. Data will be presented for a wide range of operating conditions to show how much the CO and NOx emissions can be affected by changes in the ambient conditions for fuel gas fired natural draft process heaters, which are the most common type used in the hydrocarbon and petrochemical industries. Some type of automated burner control, which is virtually non-existent today in this application, is recommended to adjust for the variations in ambient conditions.

DISTRIBUTIONAL ANALYSIS OF RELATED SYNSETS IN WordNet FOR A WORD SENSE DISAMBIGUATION TASK

2005 ◽  
Vol 14 (06) ◽  
pp. 919-934 ◽  
Author(s):  
KOSTAS FRAGOS ◽  
YANIS MAISTROS
Keyword(s):  
Target Word ◽  
Goodness Of Fit ◽  
Hypothesis Test ◽  
Word Sense Disambiguation ◽  
The Other ◽  
Reasonable Assumption ◽  
P Value ◽  
Word Sense ◽  
Chi Square ◽  
Sense Disambiguation

This work presents a new method for an unsupervised word sense disambiguation task using WordNet semantic relations. In this method we expand the context of a word being disambiguated with related synsets from the available WordNet relations and study within this set the distribution of the related synset that correspond to each sense of the target word. A single sample Pearson-Chi-Square goodness-of-fit hypothesis test is used to determine whether the null hypothesis of a composite normality PDF is a reasonable assumption for a set of related synsets corresponding to a sense. The calculated p-value from this test is a critical value for deciding the correct sense. The target word is assigned the sense, the related synsets of which are distributed more "abnormally" relative to the other sets of the other senses. Our algorithm is evaluated on English lexical sample data from the Senseval-2 word sense disambiguation competition. Three WordNet relations, antonymy, hyponymy and hypernymy give a distributional set of related synsets for the context that was proved quite a good word sense discriminator, achieving comparable results with the system obtained the better results among the other competing participants.

scholarly journals Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield

2020 ◽  
Author(s):  
Jin Pan ◽  
Charbel Harb ◽  
Weinan Leng ◽  
Linsey C. Marr
Keyword(s):  
Particle Size ◽  
Respiratory Tract ◽  
Filtration Efficiency ◽  
The Other ◽  
Woven Fabric ◽  
Protection Efficiency ◽  
Overall Efficiency

AbstractWe evaluated the effectiveness of 11 face coverings for material filtration efficiency, inward protection efficiency on a manikin, and outward protection efficiency on a manikin. At the most penetrating particle size, the vacuum bag, microfiber cloth, and surgical mask had material filtration efficiencies >50%, while the other materials had much lower filtration efficiencies. However, these efficiencies increased rapidly with particle size, and many materials had efficiencies >50% at 2 μm and >75% at 5 μm. The vacuum bag performed best, with efficiencies of 54-96% for all three metrics, depending on particle size. The thin acrylic and face shield performed worst. Inward protection efficiency and outward protection efficiency were similar for many masks; the two efficiencies diverged for stiffer materials and those worn more loosely (e.g., bandana) or more tightly (e.g., wrapped around the head) compared to a standard earloop mask. Discrepancies between material filtration efficiency and inward/outward protection efficiency indicated that the fit of the mask was important. We calculated that the particle size most likely to deposit in the respiratory tract when wearing a mask is ∼2 μm. Based on these findings, we recommend a three-layer mask consisting of outer layers of a flexible, tightly woven fabric and an inner layer consisting of a material designed to filter out particles. This combination should produce an overall efficiency of >70% at the most penetrating particle size and >90% for particles 1 μm and larger if the mask fits well.

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