Wenxiao Chu, Maria Vicidomini, Francesco Calise, Neven Duić, Poul Alberg Østergaard, Qiuwang Wang, Maria da Graça Carvalho,
The COVID-19 pandemic has had a significant impact on the supply chains of traditional fossil fuels. According to a report by the International Energy Agency (IEA) from 2020, oil-refining activity fell by more than the IEA had anticipated. It was also assumed that the demand in 2021 would likely be 2.6 million bpd below the 2019 levels. However, renewable markets have shown strong resilience during the crisis. It was determined that renewables are on track to meet 80% of the growth in electricity ...
Tópico(s): Energy and Environment Impacts
2022 - Multidisciplinary Digital Publishing Institute | Energies
João Garcia, M. Filomena Teodoro, R. Cerdeira, Luís Coelho, Prashant Kumar, Maria da Graça Carvalho,
A methodology to predict PM10 concentrations in urban outdoor environments is developed based on the generalized linear models (GLMs). The methodology is based on the relationship developed between atmospheric concentrations of air pollutants (i.e. CO, NO2, NOx, VOCs, SO2) and meteorological variables (i.e. ambient temperature, relative humidity (RH) and wind speed) for a city (Barreiro) of Portugal. The model uses air pollution and meteorological data from the Portuguese monitoring air quality station ...
Tópico(s): Vehicle emissions and performance
2016 - Taylor & Francis | Environmental Technology
Sandrina Pereira, Mário Costa, Maria da Graça Carvalho, Abel Rodrigues,
This manuscript examines the potential of poplar short rotation coppice cultivation for bioenergy in the Alentejo region, Southern Portugal. The biomass is intended to fulfil, at least, 10% (energy basis) of the fuel needs of two Portuguese coal-fired power plants (Sines and Pego), using co-firing technology. The study considers the overall production chain from cradle to power plant gate, cultivated in scrubland areas with duration of 12 years, harvested every three years and with 6667 plants per ...
Tópico(s): Biofuel production and bioconversion
2016 - Elsevier BV | Energy Conversion and Management
Raquel Segurado, Mário Costa, Neven Duić, Maria da Graça Carvalho,
The electricity production in S. Vicente is based on fossil fuel and wind power and, although there are significant wind resources, they are not fully used because of its intermittent nature. In a previous work, we proposed solutions to tackle this issue. Since this island does not have fresh water available, excess wind power can be provided to desalination units to produce desalinated water to supply the population. Other solution studied previously was the use of desalinated water in a pumped ...
Tópico(s): Energy and Environment Impacts
2015 - Elsevier BV | Energy
João Garcia, R. Cerdeira, N. Tavares, Luís Coelho, Prashant Kumar, Maria da Graça Carvalho,
Four geometrical configurations of a real street canyon in Barreiro city (Portugal) are considered to study their influence on the dispersion of PM10. These configurations include actual architectural layout of the street (Option 1), and three virtual cases (Options 1–3). Option 2 includes the modification of real geometry by including 4 m gaps between the buildings situated on the southern part of the street canyon. Option 3 considers 6 m gaps between buildings as opposed to 4 m gaps in Option 2. ...
Tópico(s): Urban Heat Island Mitigation
2013 - Elsevier BV | Urban Climate
This paper will summarise the European Strategy for Energy and Climate Change. In current international negotiations Europe has proposed a 20% reduction in GHG (greenhouse gases) in the developed countries by 2020 or 30% should there be an international agreement in the domain. However it is important to define measures to achieve the targets. One of the principal tools is to improve energy efficiency under the energy efficiency action plan, which will help to achieve a 20% energy saving by 2020. ...
Tópico(s): Renewable Energy and Sustainability
2012 - Elsevier BV | Energy
Goran Krajačić, Neven Duić, Zlatko Zmijarević, Brian Vad Mathiesen, Aleksandra Anić Vučinić, Maria da Graça Carvalho,
EU import dependence on hydrocarbons and resulting negative environmental impact related to their use led to setting of new measures and energy policy that will make, in time, a post carbon society more feasible and achievable. Energy systems of this society will be based on four pillars: Renewable Energy, Buildings as Positive Power Plants, Energy Storage and Smart grids in combination with Plug-in Vehicles. All these pillars must be supported by the use of smart energy storage. The results of ...
Tópico(s): Microgrid Control and Optimization
2011 - Elsevier BV | Applied Thermal Engineering
Gilberto Tavares, Zdena Zsigraiová, Viriato Semião, Maria da Graça Carvalho,
This work proposes the application of two multivariate statistical methods, principal component analysis (PCA) and partial least square (PLS), to a continuous process of a municipal solid waste (MSW) moving grate-type incinerator for process control – monitoring, fault detection and diagnosis – through the extraction of information from historical data. PCA model is built for process monitoring capable of detecting abnormal situations and the original 16-variable process dimension is reduced to eight, ...
Tópico(s): Spectroscopy and Chemometric Analyses
2011 - Elsevier BV | Waste Management
Goran Krajačić, Neven Duić, Antonis G. Tsikalakis, Manos Zoulias, George Caralis, E. Panteri, Maria da Graça Carvalho,
Faster market integration of new energy technologies can be achieved by use of proper support mechanisms that will create favourable market conditions for such technologies. The best examples of support mechanisms presented in the last two decades have been the various schemes for the promotion of renewable energy sources (RES). In the EU, the most successful supporting schemes are feed-in tariffs which have significantly increased utilisation of renewable energy sources in Germany, Spain, Portugal, ...
Tópico(s): Microgrid Control and Optimization
2011 - Elsevier BV | Energy Policy
Maria da Graça Carvalho, Matteo Bonifacio, P. Dechamps,
Tópico(s): Climate Change Communication and Perception
2010 - Elsevier BV | Energy
Goran Krajačić, Neven Duić, Maria da Graça Carvalho,
When it comes to the energy planning, computer programs like H2RES are becoming valuable tools. H2RES has been designed as support for simulation of different scenarios devised by RenewIsland methodology with specific purpose to increase integration of renewable sources and hydrogen into island energy systems. The model can use wind, solar, hydro, biomass, geothermal as renewable energy sources and fossil fuel blocks and grid connection with mainland as back up. The load in the model can be represented ...
Tópico(s): Social Acceptance of Renewable Energy
2009 - Elsevier BV | International Journal of Hydrogen Energy
Zdena Zsigraiová, Gilberto Tavares, Viriato Semião, Maria da Graça Carvalho,
Usually in islands both primary energy sources and drinking water are missing. Additionally, municipal solid waste (MSW) must be managed avoiding exclusive use of landfills, which limits sustainable development. Power generation from MSW incineration contributes significantly to replacing energy produced from fossil fuels and to reduce overall emissions. A solution based on thermodynamics, environmental and economic analyses and 3D-GIS modelling for the afore-mentioned problems for Cape Verde is ...
Tópico(s): Electric Vehicles and Infrastructure
2009 - Elsevier BV | Energy
Naim Hamdia Afgan, Maria da Graça Carvalho, Petros A. Pilavachi, Nélson Martins,
Decision making methods are used as a tool for the selection of alternatives to be evaluated on the basis of several criteria. Evaluation of the potential routes for natural gas supply to the Southeast and Central European countries is studied using single and multi-criteria evaluation. The potential options included in this analysis are the: Yamal Route; Nabucco Route; West Balkan Route; LNG Neum Route; and Gas by Wire Route. In part 1, the paper was devoted to the definition of the indicators ...
Tópico(s): Global Energy and Sustainability Research
2008 - Elsevier BV | Energy Conversion and Management
Nain H. Afgan, Maria da Graça Carvalho,
Tópico(s): Electric Vehicles and Infrastructure
2008 - Elsevier BV | Energy Policy
Gilberto Tavares, Zdena Zsigraiová, Viriato Semião, Maria da Graça Carvalho,
Abstract Purpose – The high costs of collection and transportation of municipal solid waste (MSW) on the overall waste management budget (sometimes more than 75 per cent) makes it an issue to be urgently addressed for improvement. The paper aims to focus on the optimisation of routing networks for waste collection/transportation. Design/methodology/approach – The paper proposes herein the application of geographic information system (GIS) 3D route modelling for waste collection/transportation to optimise ...
Tópico(s): Transportation and Mobility Innovations
2008 - Emerald Publishing Limited | Management of Environmental Quality An International Journal
Gabriel Vyto de Lima Tavares, Zdena Zsigraiová, Viriato Semião, Maria da Graça Carvalho,
Collection of municipal solid waste (MSW) may account for more than 70% of the total waste management budget, most of which is for fuel costs. It is therefore crucial to optimise the routing network used for waste collection and transportation. This paper proposes the use of geographical information systems (GIS) 3D route modelling software for waste collection and transportation, which adds one more degree of freedom to the system and allows driving routes to be optimised for minimum fuel consumption. ...
Tópico(s): Transportation and Mobility Innovations
2008 - Elsevier BV | Waste Management
Goran Krajačić, Rui Martins, Antoine Busuttil, Neven Duić, Maria da Graça Carvalho,
Hydrogen as an energy vector can increase penetration of renewable and intermittent sources in the energy supply of the islands and it can serve as an energy vector that may allow reaching 100% renewable energy supply of island communities. This article presents summary of the results of several case studies: Island of Mljet—Croatia, Porto Santo—Madeira, Terceira—Azores, and Malta. The islands were analysed by RenewIslands methodology and it was decided to apply hydrogen as an energy vector. Different ...
Tópico(s): Integrated Energy Systems Optimization
2008 - Elsevier BV | International Journal of Hydrogen Energy
Naim Hamdia Afgan, Maria da Graça Carvalho, Petros A. Pilavachi, Nélson Martins,
The need for diversification of energy sources is an immanent goal in long term energy strategy. In particular, this is of great importance for the natural gas supply. In this respect, evaluation and assessment of potential natural gas resources and their relation to consumers is of great importance. The natural gas supply in Europe is one of the main issues of European energy strategy to be followed in the future. In particular, the natural gas supply in the southeast countries is important. This ...
Tópico(s): Global Energy and Sustainability Research
2007 - Elsevier BV | Energy Conversion and Management
Naim Hamdia Afgan, Maria da Graça Carvalho, M. Jovanović,
Abstract Biomass use for power generation has become an attractive option for the increase of energy production with the increase of efficiency, decrease of environment degradation and waste utilization. Justification of the biomass use benefits requires a multi-criteria assessment based on the evaluation of economic, environmental, technological and social aspects. In this respect, the need for the evaluation of biomass-fired power plant is of great interest for the validation of benefits of biomass ...
Tópico(s): Global Energy and Sustainability Research
2007 - Taylor & Francis | International Journal of Sustainable Energy
Neven Duić, Maria Lerer, Maria da Graça Carvalho,
The article describes the H2RES model for optimisation of integration of hydrogen usage with intermittent renewable energy sources (RES) in island energy systems, on Porto Santo, the example of an isolated island in Madeira archipelago. It shows that it is possible to increase the penetration of renewable energy sources by introducing a hydrogen storage component, albeit at a relatively high cost. It compares peak shaving case based on storing excess wind with one based on storing excess electricity ...
Tópico(s): Energy and Environment Impacts
2003 - Taylor & Francis | International Journal of Sustainable Energy
Minghou Xu, Xiuguang He, J. L. T. Azevedo, Maria da Graça Carvalho,
International Journal of Energy ResearchVolume 26, Issue 14 p. 1221-1236 Research Article An advanced model to assess fouling and slagging in coal fired boilers Minghou Xu, Corresponding Author Minghou Xu National Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, People's Republic of ChinaNational Laboratory of Coal Combustion, Huazong University of Science and Technology, Wuhan 430074, People's Republic of China or J. L. T. Azevedo, Instituto Superior Técnico, ...
Tópico(s): Thermochemical Biomass Conversion Processes
2002 - Wiley | International Journal of Energy Research
Naim Hamdia Afgan, Maria da Graça Carvalho,
The multi-criteria evaluation of new and renewable technologies demonstrates the potential analysis of complex systems. Every energy system under consideration is an entity by itself, defined by the respective number of parameters which are deterministically interrelated according to the physical laws. Sustainability indicators take into account the economic and environmental resources parameters. This paper presents selection of criteria and options for the new and renewable energy technologies ...
Tópico(s): Advanced Energy Technologies and Civil Engineering Innovations
2002 - Elsevier BV | Energy
Augusto César de Mendonça Brasil, Tiago Farias, Maria da Graça Carvalho, Ümit Ö. Köylü,
The structures of both cluster–cluster and particle–cluster fractal-like aggregates were investigated in the present study. Statistically significant populations of numerically simulated aggregates having appropriate fractal properties and prescribed number of primary particles per aggregate were generated in order to characterize three-dimensional morphological properties of aggregates, such as fractal dimension, fractal pre-factor, coordination number distribution function, and distribution of ...
Tópico(s): Heat and Mass Transfer in Porous Media
2001 - Elsevier BV | Journal of Aerosol Science
Minghou Xu, J. L. T. Azevedo, Maria da Graça Carvalho,
Numerical modeling of a front wall pulverised coal fired utility boiler is presented in this paper. Comparison between the predictions and measurements in the boiler is addressed. The accordance of the calculation results with the experimental data at several operating conditions validates the models and algorithm employed in the computation. The need to improve burner or boiler design with the objective of producing NOx abatement while avoiding some negative side effects is also the motivation ...
Tópico(s): Thermochemical Biomass Conversion Processes
2001 - Elsevier BV | Computer Methods in Applied Mechanics and Engineering
D Ayres, Miguel Caldas, Viriato Semião, Maria da Graça Carvalho,
This work addresses the development of a mathematical model to predict the joint distribution for both size and velocity of the droplets in sprays, based on the maximum entropy formalism. Using this joint distribution, models to obtain separated distributions for size and velocity of sprays are also presented. Correlations for the average velocity for both pressure jet and airblast atomisers, based on assumed profiles in the atomiser gun, are obtained as a function of easily measurable parameters. ...
Tópico(s): Particle Dynamics in Fluid Flows
2001 - Elsevier BV | Fuel
Minghou Xu, J. L. T. Azevedo, Maria da Graça Carvalho,
This paper presents numerical simulation of the flow and combustion process in the furnace of a pulverized coal fired utility boiler of 350 MWe with 24 swirl burners installed at the furnace front wall. Five different cases with 100, 95, 85, 70 and 50% boiler full load are simulated. The comparison between the simulation and the plant data is stressed in this study. The heat flux to furnace walls between the measured values and the calculation results is compared. It is found that increasing the ...
Tópico(s): Thermochemical Biomass Conversion Processes
2000 - Elsevier BV | Fuel
Augusto César de Mendonça Brasil, Tiago Farias, Maria da Graça Carvalho,
While the fractal dimension of cluster-cluster aggregates, Df , appears to be a well-established property, the fractal prefactor, kg (also known as structural coefficient), continues to exhibit a large range of possible values. In the present paper, an attempt is made to clarify this issue which leads to conclusive results concerning the value to adopt for the fractal prefactor of simulated aggregates. Starting from a large population of "free" numerically simulated aggregates (i.e., where no restrictions ...
Tópico(s): Advanced Clustering Algorithms Research
2000 - Taylor & Francis | Aerosol Science and Technology
Naim Hamdia Afgan, Maria da Graça Carvalho, Nikolai V. Hovanov,
The paper presents an attempt to select, define and apply a set of sustainability indicators for the energy system assessment. Starting from the general sustainability concept, a set of indicators is defined reflecting specific criteria for the energy system evaluation. Particular attention is devoted to the resource, environment, social and economic criteria. Among these groups of criteria there are individual indicators emphasising respective aspect of the sustainability concept. This approach ...
Tópico(s): Integrated Energy Systems Optimization
2000 - Elsevier BV | Energy Policy
Augusto César de Mendonça Brasil, Tiago Farias, Maria da Graça Carvalho,
In the present paper a simple and straightforward recipe for characterizing the structural and fractal properties of aggregates from their projected images is presented. Starting from geometrical properties that are directly measured from the projected image—such as primary particle mean diameter, maximum projected length, projected area, and overlap coefficient—important threedimensional properties including number of primary particles in an aggregate, radius of gyration, aggregate surface, or ...
Tópico(s): Coagulation and Flocculation Studies
1999 - Elsevier BV | Journal of Aerosol Science
Naim Hamdia Afgan, Mohammad Darwish, Maria da Graça Carvalho,
The paper presents an attempt to assess sustainability of desalination plants for water production based on resource, environmental and economic indicators. Four types of desalination plants are taken into a consideration: single MSF, dual purpose MSF, RO with local energy consumption and RO with PV electric energy production. The analysis is based on data from desalination plants in Gulf countries. In particular, it reflects water production demand and energy sources used for the individual plants. ...
Tópico(s): Sustainable Development and Environmental Policy
1999 - Elsevier BV | Desalination