Evaluation of Environmental Loads for the Synthesis of a Trigeneration System

2010 ◽  
Author(s):  
Luis M. Serra ◽  
Miguel A. Lozano ◽  
Monica Carvalho
Keyword(s):  
Natural Gas ◽  
Assessment Tool ◽  
Programming Model ◽  
Technical Information ◽  
Hot Water ◽  
Case Scenario ◽  
Worst Case ◽  
Environmental Loads ◽  
Heating And Cooling ◽  
One Year

This paper details the calculation of the environmental loads associated with the construction of each piece of equipment (considering that the materials were not reused at the end of the equipment’s lifetime, which is the worst case scenario) and operation of a trigeneration system. The purpose of a trigeneration system is to meet the demands of a consumer center — in this case, a medium-sized hospital located in Zaragoza, Spain. The evaluation extended over a period of one year, considering previously specified energy service demands (electricity, heat - sanitary hot water and heating -, and cooling). The system interacted with the economic environment (market) through the purchase of natural gas and electricity from the grid, and also through the sale of autogenerated electricity to the grid, according to Spanish regulations. Therefore, the environmental loads regarding the operation of the system were associated with the consumption of natural gas and electricity purchased/sold from/to the grid. Technical information on each piece of equipment was obtained from catalogs and from consultation with manufacturers. Regarding natural gas, special care was taken to correctly identify the natural gas supplied to a user in Spain (it was considered that the gas comes from Algeria, transported in Liquefied Natural Gas (LNG) carriers, including pipeline transportation to the user and controlled burning). The electricity supplied by the Spanish electric grid was also properly specified and characterized. The environmental loads were calculated utilizing SimaPro, a specialized Life Cycle Assessment tool, and then incorporated into a linear programming model, solved by LINGO optimization software. Environmental criteria were used to obtain the optimal configuration and operation of the system simultaneously.

scholarly journals Temperature Control Concept for Parallel IGBT Operation

Electronics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 429
Author(s):  
Andrej Brandis ◽  
Denis Pelin ◽  
Tomislav Matić ◽  
Danijel Topić
Keyword(s):  
Temperature Control ◽  
Thermal Conditions ◽  
Bipolar Transistors ◽  
Test Model ◽  
Test Results ◽  
Case Scenario ◽  
Basic Algorithm ◽  
Worst Case ◽  
Heating And Cooling ◽  
Control Concept

This paper addresses the concept of load balancing in the operation of parallel insulated-gate bipolar transistors (IGBTs), in which the temperature is used as the main control parameter. In parallel IGBT operation, it is essential to ensure an equal load distribution across all IGBTs. Two basic algorithm concepts for temperature control were developed for the purpose of balancing. A test model based on the parallel IGBTs operation was assembled in a laboratory and the developed algorithms were tested for the chosen parameters. MATLAB was used for final data processing. The comparison between the two implemented basic algorithms provides insights into the temperature behavior of parallel IGBTs in terms of individual IGBT’s heating and cooling trajectories and time constants. All tests were conducted without the heatsinks to obtain the worst-case scenario in terms of thermal conditions. The test results show that temperature control in the operation of parallel IGBTs is possible but limited.

scholarly journals Robust Topology Optimization of Truss-Like Space Structures

2021 ◽  
pp. 296-306
Author(s):  
Michael Hartisch ◽  
Christian Reintjes ◽  
Tobias Marx ◽  
Ulf Lorenz
Keyword(s):  
Topology Optimization ◽  
Explicit Knowledge ◽  
Programming Model ◽  
Dimensional Space ◽  
Mathematical Optimization ◽  
Space Structures ◽  
Case Scenario ◽  
Worst Case ◽  
Robust Topology Optimization ◽  
Traditional Manufacturing

AbstractDue to the additional design freedom and manufacturing possibilities of additive manufacturing compared to traditional manufacturing, topology optimization via mathematical optimization gained importance in the initial design of complex high-strength lattice structures. We consider robust topology optimization of truss-like space structures with multiple loading scenarios. A typical dimensioning method is to identify and examine a suspected worst-case scenario using experience and component-specific information and to incorporate a factor of safety to hedge against uncertainty. We present a quantified programming model that allows us to specify expected scenarios without having explicit knowledge about worst-case scenarios, as the resulting optimal structure must withstand all specified scenarios individually. This leads to less human misconduct, higher efficiency and, thus, to cost and time savings in the design process. We present three-dimensional space trusses with minimal volume that are stable for up to 100 loading scenarios. Additionally, the effect of demanding a symmetric structure and explicitly limiting the diameter of truss members in the model is discussed.

Forecasting the Domestic Utilization of Natural Gas in Nigeria (2015-2020)

2016 ◽  
Author(s):  
J. J. Adaji ◽  
R. U. Onolemhemhen ◽  
S. O. Isehunwa ◽  
A. Adenikinju
Keyword(s):  
Natural Gas ◽  
Alternative Fuels ◽  
Arima Model ◽  
Ordinary Least Squares ◽  
Case Scenario ◽  
Worst Case ◽  
Gas Utilization ◽  
Real Gdp ◽  
Resource Endowment ◽  
Utilization Patterns

ABSTRACT Domestic utilization of natural gas in Nigeria is being hampered by the poor developments in the natural gas sector over the years, with low level of electricity (generation) consumption per capital, weak legal, commercial and regulatory framework amidst poor infrastructural developments in natural gas as compared to that which exists for oil. Nigeria ranks the second in gas flaring and shows low volumes of domestic gas utilization, consuming only about 11% out of the 8.25 billion cubic feet produced per day in 2014 despite its natural gas resource endowment. This paper examines the determinants of domestic utilization of natural gas in Nigeria from 1990-2013. It investigates its relationship as a function of price of natural gas, price of alternative fuels, foreign direct investment, volumes of gas flared, electricity generated from natural gas sources and per capital real GDP. Going further, it forecasts its likely growth rate for a short-term period, using an econometric methodology of ordinary least squares and an ARIMA model, it estimates the relationship between the variables and uses the historical trend to forecast into the future. The result of the study showed that the determinants jointly explain the pattern of domestic gas utilization in Nigeria by 98%. Individually, per capital real GDP, electricity generated from natural gas sources and changes in the volume of domestic utilization of natural gas was found to have a positive and significant effect on domestic gas utilization. Further, the forecast values show evidence of a slow but gradual increase in utilization pattern in the near future from 2015-2020. A best-case scenario of an increase of 0.15% and a worst-case scenario of a decrease of 0.14% was presented. In conclusion, having identified significant influences on domestic gas utilization patterns in Nigeria it is imperative that the government uses economic instrument to enhance the utilization patterns in Nigeria by improving economic activities and developing the power sector which shows significant influence in domestic natural gas utilization patterns.

Methods for Determining the Amount of Hydrates Formed During Blowdown of Natural Gas Compressor Station

2014 ◽  
Author(s):  
Y. Beauregard ◽  
K. K. Botros
Keyword(s):  
Natural Gas ◽  
Temperature Drop ◽  
Measured Data ◽  
Compressor Station ◽  
Case Scenario ◽  
Equilibrium Conditions ◽  
Worst Case ◽  
Moisture Contents ◽  
Natural Gas Hydrates ◽  
Allowable Range

Natural gas hydrates could form during blowdown of compressor station yard piping, even if the moisture composition is within the allowable range of up to 65 mg/st.m3. This is because the temperature of the gas drops well below the vapour-hydrate equilibrium. If sufficient hydrates form, they have the potential to impede the path of the gas to the blowdown stack exit. To evaluate this risk, it is important to determine the conditions at which hydrates could form under gas blowdown situations and accurately determine the quantity that would form as both gas pressure and temperature drop during the blowdown process. This paper first compares the hydrate equilibrium conditions for different moisture contents obtained with a publicly available model to published measured data for some alkanes present in natural gas. A gas blowdown scenario establishing the gas conditions (P and T) is then presented based on the worst case scenario of adiabatic expansion of the gas. Based on these conditions, two methods are developed to quantify the amount of hydrates that could form during the blowdown process. These methods are demonstrated on a gas blowdown event of compressor station discharge yard piping where the gas was assumed to have moisture contents of 65 mg/st.m3. The potential amount of hydrates formed and the implications on the gas path to blowdown exit are discussed.

Computer modeling as tools to estimate the impact of fuel type on the capacity rating of lime kilns

TAPPI Journal ◽  
2015 ◽  
Vol 14 (7) ◽  
pp. 461-473
Author(s):  
J. PETER GOROG ◽  
W. RAY LEARY ◽  
DAVID WANG ◽  
KEVIN DAVIS
Keyword(s):  
Natural Gas ◽  
Paper Industry ◽  
Operating Conditions ◽  
Fuel Oil ◽  
Fuel Type ◽  
Case Scenario ◽  
Modeling Tools ◽  
Worst Case ◽  
The Impact ◽  
Capacity Rating

In response to the drop in the price of natural gas, the U.S. pulp and paper industry has switched from using fuel oil to natural gas to fire kilns used to regenerate lime in the kraft process. While being financially attractive, replacing fuel oil with natural gas can be challenging. This is particularity true when the capacity rating is constrained by the temperatures of the gas exiting the kiln. In the worst case scenario, the increase in flue gas temperatures associated with switching from fuel oil to natural gas can significantly de-rate the capacity of the kiln. This paper describes a range of computational modeling tools that can be used to estimate the impacts of kiln geometry, fuel type, operating conditions, and burner design on kiln performance. Data taken from operating kilns is presented, which validates the use of these models. A detailed case study is presented showing how small amounts of torrefied wood can be co-fired with natural gas as a replacement for fuel oil without de-rating the capacity of the kiln. The visualization of the flow fields, temperature distributions, and species concentrations provided by computer models are critical to optimizing kiln operations as new fuels are being considered as replacements for more expensive, carbon intensive fuel oil.

Reducing Probabilistic Weather Forecasts to the Worst Case Scenario: Anchoring Effects

2008 ◽  
Author(s):  
Sonia Savelli ◽  
Susan Joslyn ◽  
Limor Nadav-Greenberg ◽  
Queena Chen
Keyword(s):  
Case Scenario ◽  
Worst Case ◽  
Weather Forecasts ◽  
Worst Case Scenario ◽  
Anchoring Effects

Experience of negative pressure wound therapy over sternal wound healing: A retrospective review

WCET Journal ◽  
2019 ◽  
Vol 39 (2) ◽  
pp. 9-18
Author(s):  
Wai Sze Ho ◽  
Wai Kuen Lee ◽  
Ka Kay Chan ◽  
Choi Ching Fong
Keyword(s):  
Wound Healing ◽  
Negative Pressure ◽  
Negative Pressure Wound Therapy ◽  
Assessment Tool ◽  
Wound Care ◽  
Wound Therapy ◽  
Treatment Pathways ◽  
Wound Assessment ◽  
One Year

Objectives The aim of this study was to retrospectively review the effectiveness of negative pressure wound therapy (NPWT) in sternal wound healing with the use of the validated Bates-Jensen Wound Assessment Tool (BWAT), and explore the role of NPWT over sternal wounds and future treatment pathways. Methods Data was gathered from patients' medical records and the institution's database clinical management system. Seventeen subjects, who had undergone cardiothoracic surgeries and subsequently consulted the wound care team in one year were reviewed. Fourteen of them were included in the analysis. Healing improvement of each sternal wound under continuous NPWT and continuous conventional dressings was studied. In total, 23 continuous NPWT and 13 conventional dressing episodes were analysed with the BWAT. Results Among conventional dressing episodes, sternal wound improvement was 2.5–3% over 10 days to 3.5 weeks, whereas 4–5% sternal healing was achieved in 5 days to 2 weeks with sternal wire presence. Better healing at 11% in 1 week by conventional dressing was attained after sternal wire removal. In NPWT episodes, 8–29%, 13–24%, and 15–46% of healing was observed in 2 weeks, 3.5 to 5 weeks and 6 to 7 weeks, respectively. Only 39% wound healing was acquired at the 13th week of NPWT in one subject. With sternal wire present, 6%–29% wound healing progress was achieved by NPWT in 1–4 weeks, and 16–23% wound improvement in 2 to 4.5 weeks by NWPT after further surgical debridement. After sternal wire removal, 6–34% sternal wound healing occurred by continuous NPWT for 1–2 weeks, and maximum healing at 46% after 2.5 weeks of NPWT were observed. Conclusions Better wound healing was achieved in the NPWT group in comparison to conventional dressings alone. However, suboptimal sternal wound healing by NPWT alone was observed. Removal of sternal wire may improve the effectiveness of NPWT. Successful tertiary closure after NPWT among subjects supports the important bridging role of NPWT in sternal wound healing. Factors causing stagnant sternal wound healing by NPWT alone are discussed.

EXPEDITION TO MALI, 2020

2020 ◽  
pp. 12-28
Author(s):  
D. V. Vaniukova ◽  
◽  
P. A. Kutsenkov ◽  
Keyword(s):  
Mass Murder ◽  
The State ◽  
Case Scenario ◽  
Worst Case ◽  
Traditional Art ◽  
Peter The Great ◽  
State Museum ◽  
Bobo Dioulasso ◽  
Oriental Studies ◽  
The Village

The research expedition of the Institute of Oriental studies of the Russian Academy of Sciences has been working in Mali since 2015. Since 2017, it has been attended by employees of the State Museum of the East. The task of the expedition is to study the transformation of traditional Dogon culture in the context of globalization, as well as to collect ethnographic information (life, customs, features of the traditional social and political structure); to collect oral historical legends; to study the history, existence, and transformation of artistic tradition in the villages of the Dogon Country in modern conditions; collecting items of Ethnography and art to add to the collection of the African collection of the. Peter the Great Museum (Kunstkamera, Saint Petersburg) and the State Museum of Oriental Arts (Moscow). The plan of the expedition in January 2020 included additional items, namely, the study of the functioning of the antique market in Mali (the “path” of things from villages to cities, which is important for attributing works of traditional art). The geography of our research was significantly expanded to the regions of Sikasso and Koulikoro in Mali, as well as to the city of Bobo-Dioulasso and its surroundings in Burkina Faso, which is related to the study of migrations to the Bandiagara Highlands. In addition, the plan of the expedition included organization of a photo exhibition in the Museum of the village of Endé and some educational projects. Unfortunately, after the mass murder in March 2019 in the village of Ogossogou-Pel, where more than one hundred and seventy people were killed, events in the Dogon Country began to develop in the worst-case scenario: The incessant provocations after that revived the old feud between the Pel (Fulbe) pastoralists and the Dogon farmers. So far, this hostility and mutual distrust has not yet developed into a full-scale ethnic conflict, but, unfortunately, such a development now seems quite likely.

Risk-Based Robust Bidding Strategies for EVs’ Aggregators in Day-ahead Markets with Uncertainty

2020 ◽  
Author(s):  
Ahmed Abdelmoaty ◽  
Wessam Mesbah ◽  
Mohammad A. M. Abdel-Aal ◽  
Ali T. Alawami
Keyword(s):  
Robust Optimization ◽  
Electricity Market ◽  
Real Life ◽  
Optimization Approach ◽  
Case Scenario ◽  
Worst Case ◽  
Bidding Strategies ◽  
Wind Generators ◽  
Proposed Model ◽  
Optimal Bidding

In the recent electricity market framework, the profit of the generation companies depends on the decision of the operator on the schedule of its units, the energy price, and the optimal bidding strategies. Due to the expanded integration of uncertain renewable generators which is highly intermittent such as wind plants, the coordination with other facilities to mitigate the risks of imbalances is mandatory. Accordingly, coordination of wind generators with the evolutionary Electric Vehicles (EVs) is expected to boost the performance of the grid. In this paper, we propose a robust optimization approach for the coordination between the wind-thermal generators and the EVs in a virtual<br>power plant (VPP) environment. The objective of maximizing the profit of the VPP Operator (VPPO) is studied. The optimal bidding strategy of the VPPO in the day-ahead market under uncertainties of wind power, energy<br>prices, imbalance prices, and demand is obtained for the worst case scenario. A case study is conducted to assess the e?effectiveness of the proposed model in terms of the VPPO's profit. A comparison between the proposed model and the scenario-based optimization was introduced. Our results confirmed that, although the conservative behavior of the worst-case robust optimization model, it helps the decision maker from the fluctuations of the uncertain parameters involved in the production and bidding processes. In addition, robust optimization is a more tractable problem and does not suffer from<br>the high computation burden associated with scenario-based stochastic programming. This makes it more practical for real-life scenarios.<br>

scholarly journals A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 491
Author(s):  
Alina E. Kozhukhova ◽  
Stephanus P. du Preez ◽  
Aleksander A. Malakhov ◽  
Dmitri G. Bessarabov
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Combustion Temperature ◽  
Volume Fraction ◽  
Morphological Characteristics ◽  
Al Alloy ◽  
Impregnation Method ◽  
Case Scenario ◽  
Worst Case ◽  
Thermal Distribution

In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC.

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