Nelson Martins
@ua.pt
Mechanical Engineering Department
Universidade de Aveiro, Portugal
Scopus Publications
Scopus Publications
André Quintã, Cheila Conceição, Nelson Martins, and Jorge A. F. Ferreira
Informa UK Limited
S. Sorte, A. Figueiredo, G. Vela, M.S.A. Oliveira, R. Vicente, C. Relvas, and N. Martins
Elsevier BV
Sandra Sorte, Nelson Martins, Mónica S. A. Oliveira, German L. Vela, and Carlos Relvas
MDPI AG
The rapid growth of the wind energy industry has resulted in a significant increase in Wind Turbine Blade (WTB) waste, posing challenges for recycling due to the composite materials used in their construction. Several proposed techniques, including mechanical, thermal, and chemical processes, have been considered for wind-blade recycling, but determining the most effective approach remains a critical issue. This study presents the first comprehensive systematic review of available wind-blade recycling processes, evaluating their economic, technical, and environmental performance. Additionally, we consider the physical and mechanical properties of the recycled materials, which can aid in identifying potential markets for these materials. Among the various recycling technologies, microwave pyrolysis emerges as the most promising technique for recycling large quantities of WTB, despite some challenges and uncertainties surrounding its effectiveness and feasibility at an industrial scale. However, the optimal recycling technique for WTB will depend on multiple factors, including the blade material, the desired environmental impact, and the economic feasibility of the process. Based on this review, mechanical recycling appears to be more energy-efficient, while the fluidised bed recycling process demonstrates a lower primary energy demand, global warming potential, and power consumption. These findings provide valuable guidance for decision-makers in the wind energy industry to develop effective waste management strategies and plans for sustainable wind energy development. Addressing WTB waste and implementing efficient recycling techniques will be critical in mitigating environmental impacts and promoting sustainability in the renewable energy sector as the wind energy industry grows.
Cheila Conceição, André Quintã, Jorge A. F. Ferreira, Nelson Martins, and Marco P. Soares dos Santos
MDPI AG
Water heating is a significant part of households’ energy consumption, and tankless gas water heaters (TGWHs) are commonly used. One of the limitations of these devices is the difficulty of keeping hot water temperature setpoints when changes in water flow occur. As these changes are usually unexpected, the controllers typically used in these devices cannot anticipate them, strongly affecting the users’ comfort. Moreover, considerable water and energy waste are associated with the long-time response to cold starts. This work proposes the development of a model predictive control (MPC) to be deployed in low-cost hardware, such that the users’ thermal comfort and water savings can be improved. Matlab/Simulink were used to develop, validate and automatically generate C code for implementing the controller in microcontroller-based systems. Hardware-in-the-loop simulations were performed to evaluate the performance of the MPC algorithm in 8-bit and 32-bit microcontrollers. A 6.8% higher comfort index was obtained using the implementation on the 32-bit microcontroller compared to the current deployments; concerning the 8-bit microcontroller, a 4.2% higher comfort index was achieved. These applications in low-cost hardware highlight that users’ thermal comfort can be successfully enhanced while ensuring operation safety. Additionally, the environmental impact can be significantly reduced by decreasing water and energy consumption in cold starts of TGWHs.
Rodrigo Almeida, Petia Georgieva, and Nelson Martins
Elsevier BV
M.A. Russo, D. Carvalho, N. Martins, and A. Monteiro
Elsevier BV
Luís Sousa Rodrigues, Daniel Lemos Marques, Jorge Augusto Ferreira, Vítor António Ferreira Costa, Nelson Dias Martins, and Fernando José Neto Da Silva
MDPI AG
Domestic refrigeration and freezing appliances can be used for electrical load shifting from peak to off-peak demand periods, thus allowing greater penetration of renewable energy sources (RES) and significantly contributing to the reduction of CO2 emissions. The full realization of this potential can be achieved with the synergistic combination of smart grid (SG) technologies and the application of phase-change materials (PCMs). Being permanently online, these ubiquitous appliances are available for the most advanced strategies of demand-side load management (DSLM), including real-time demand response (DR) and direct load control (DLC). PCMs are a very cost-effective means of significantly augmenting their cold storage capacity and, hence, their load-shifting capabilities. Yet, currently, refrigerators and freezers equipped with PCMs for DSLM are still absent in the market and research works focusing on the synergy of these technologies are still scarce. Intended for a multidisciplinary audience, this broad-scoped review surveys the literature to evaluate the technological feasibility, economic viability and global impact of this combination. The state-of-the-art of SG-enabling technologies is investigated—e.g., smart meters, Internet-of-Things (IoT)—as well as current and future standards and norms. The literature on the use of PCMs for latent heat/cold storage (LHCS) is also reviewed.
André F. Quintã, Ismael Ehtiwesh, Nelson Martins, and Jorge A.F. Ferreira
Elsevier BV
M.A. Russo, D. Carvalho, N. Martins, and A. Monteiro
Elsevier BV
André F. Quintã, Jonathan D. Oliveira, Jorge A. F. Ferreira, Vítor A. F. Costa, and N. Martins
ASME International
Abstract An innovative methodology and a virtual test bench (VTB) are proposed to support the design of water heaters’ control strategies. This platform allows to speed up the development and evaluation of control systems even before the existence of prototypes or real test environments. By simulating the environmental conditions and the state of the different device components, it will be possible to detect and correct possible initial errors in the control system design which can be time consuming and costly due to subsequent modifications to the system or equipment components. The architecture of the proposed system establishes four operating modes: open-loop data acquisition, real-time simulation, hardware-in-the-loop simulation, and test of the complete real system, the incorporation of these functionalities in the same platform is not reported in the literature for domestic water heaters. The virtual test bench was designed to accommodate different water heaters including, but not limited to, gas, electric, and heat pumps, for instantaneous hot water production or including hot water storage. The prototype of the virtual test bench is described emphasizing the hardware-in-the-loop methodologies and embedded control. The particular case study of a tankless gas water heater (TGWH) is presented implementing the different operation modes in the virtual test bench. The water heater models, control strategies, simulation, and experimental data are presented and discussed.
Rodrigo Almeida, Petia Georgieva, and Nelson Martins
Springer International Publishing
Wagd Ajeeb, Monica S A Oliveira, Nelson Martins, and S M Sohel Murshed
IOP Publishing
Abstract The heat transfer performance of conventional thermal fluids in microchannels is an attractive method for cooling devices such as microelectronic applications. Computational fluid dynamics (CFD) is a very significant research technique in heat transfer studies and validated numerical models of microscale thermal management systems are of utmost importance. In this paper, some literature studies on available numerical and experimental models for single-phase and Newtonian fluids are reviewed and methods to tackle laminar fluid flow through a microchannel are sought. A few case studies are selected, and a numerical simulation is performed to obtain fluid flow behaviour within a microchannel, to test the level of accuracy and understanding of the problem. The numerical results are compared with relevant experimental results from the literature and a proper methodology for numerical investigation of single-phase and Newtonian fluid in laminar flow convection heat transfer in microscale heat exchangers is defined.
M.A. Russo, L. Ruivo, D. Carvalho, N. Martins, and A. Monteiro
Elsevier BV
Wagd Ajeeb, Monica S.A. Oliveira, Nelson Martins, and S.M. Sohel Murshed
Elsevier BV
Wagd Ajeeb, Monica S.A. Oliveira, Nelson Martins, and S.M. Sohel Murshed
Elsevier BV
Tatiana Zhiltsova., Nelson Martins, Mariana R. F. Silva, Carla F. Da Silva, Mirtha A. O. Lourenço, David M. Tobaldi, Daniel Covita, Maria Paula Seabra, and Paula Ferreira
MDPI AG
In the present study, two photocatalytic graphene oxide (GO) and carbon nanotubes (CNT) modified TiO2 materials thermally treated at 300 °C (T300_GO and T300_CNT, respectively) were tested and revealed their conversion efficiency of nitrogen oxides (NOx) under simulated solar light, showing slightly better results when compared with the commercial Degussa P25 material at the initial concentration of NOx of 200 ppb. A chemical kinetic model based on the Langmuir–Hinshelwood (L-H) mechanism was employed to simulate micropollutant abatement. Modeling of the fluid dynamics and photocatalytic oxidation (PCO) kinetics was accomplished with computational fluid dynamics (CFD) approach for modeling single-phase liquid fluid flow (air/NOx mixture) with an isothermal heterogeneous surface reaction. A tuning methodology based on an extensive CFD simulation procedure was applied to adjust the kinetic model parameters toward a better correspondence between simulated and experimentally obtained data. The kinetic simulations of heterogeneous photo-oxidation of NOx carried out with the optimized parameters demonstrated a high degree of matching with the experimentally obtained NOx conversion. T300_CNT is the most active photolytic material with a degradation rate of 62.1%, followed by P25-61.4% and T300_GO-60.4%, when irradiated, for 30 min, with emission spectra similar to solar light.
Diogo Gonçalves, Yahya Sheikhnejad, Mónica Oliveira, and Nelson Martins
Elsevier BV
Abstract This study steps into the roadmap of agenda 2030 to mitigate the human footprint on an environment with the aim of management of energy consumption in residential/commercial buildings. In order to materialize this concept, a new generation of adaptable systems of intelligent supervisory predictive control (ISPC) is introduced and implemented in which energy consumption tends to be minimized without sacrificing occupants thermal comfort. The methodology of ISPC includes building thermal simulation and multi-objective optimization algorithm that interact with conventional machine-level controllers of HVAC systems, to define optimized setpoints considering current and forecasted operation conditions. The development of a reliable surrogate model, based on robust machine learning techniques, is a key feature to confer greenness to a building in order to promote sustainability in the built environment and finally to have a smart green building. It is showed that the proposed ISPC is capable of delivering a robust, energy- and cost-effective decision while being independent of the HVAC system. The implemented energy management, as a non-destructive retrofitting procedure, can be applied to both new and existing buildings and with any level of HVAC technology.
Luis S. Rodrigues, Jorge A. Ferreira, Fernando N. Silva, Nelson D. Martins, Daniel Lemos Marques, Carlos M. Almeida, and Viatcheslav Molchanov
Institute of Electrical and Electronics Engineers (IEEE)
We describe some practical and empirically validated multivariate sensor calibration methods, which have allowed us to successfully obtain usable data from low-cost, low-precision sensors and signal conditioning electronics; we demonstrate the efficacy of these methods with real examples of nonlinear correction of thermocouple measurements from errors originated by the simultaneous influence of the cold junction and the temperature of the signal conditioning and digitizing electronic circuit components.
Hugo Marques, Mónica Oliveira, and Nelson Martins
Elsevier BV
Abstract The energy consumption of conventional HVAC systems in cold climates is strongly influenced by the ventilation thermal loads required to keep adequate levels of indoor air quality. The improvement of the energy efficiency of such systems may be achieved using heat recovery systems consisting of heat exchangers used to heat cold outdoor air using as heat source hot discharge air. Today, heat recovery systems are mostly made of metallic materials, namely aluminium alloys. The present paper assesses the technical viability of an alternative concept using polymeric materials. A set of functional requirements have been defined taking into account the operating conditions of the heat recovery system in order to select a polymer that is considered an alternative to the current metals. Polystyrene was the polymer selected. It is also reported a cradle to grave life cycle assessment for polystyrene and aluminium establishing a comparative analysis of environmental impact between both. The indicators considered are: emission of greenhouse gases and energy consumed.
Yahya Sheikhnejad, João Simões, and Nelson Martins
Elsevier BV
Abstract In this study, a new application of a Tesla turbine (TT) is presented in which a TT is introduced as a promising solution to enhance the energy efficiency of refrigeration cycles. For this special purpose, a TT is represented as a regenerative system that minimizes the wasted energy without compromising the system output quality or sacrificing standards of design and move one step forward, towards more sustainable industries. To achieve this goal, a 3D thermohydrodynamic analysis of the Newtonian turbulent compressible flow of high-pressure methane through a Tesla turbine has been performed under different configurations and operational conditions. Methane was defined as a real gas through the Redlich–Kwong equation of state. The complex unstructured grid generation was employed to produce a low-skewness mesh for a CFD model on the commercial software of ANSYS Fluent for simulation of heat and mass transfer by FVM. As a result of the present study, practical design rules are proposed to support engineers defining optimized TTs for predetermined operating conditions, namely regarding power output, disc sizes and angular velocity.
Reza Sirous, Fernando José Neto da Silva, Luís António da Cruz Tarelho, and Nelson Amadeu Dias Martins
Elsevier BV
Abstract Densification of the biomass residues as an efficient method to produce a renewable and CO2 neutral energy resource has been in consideration in recent years. However, according to a recent boost in the European wood pellet demand, the importance of R&D studies for substitution and enhancement of current raw materials for pelleting purposes has been increased. A large amount of annual garden waste and agricultural residues in Portugal causes that so-called Mixed Biomass Pelleting (MBP) method becomes a promising approach of the future that by closing the cycles in the agro-economic environments of Portugal, enhances the socio-economic conditions in the rural areas. This itself will have one more important consequence of wildfire prevention in the Portuguese forests. This work as a subset of a broader study that aims to develop an evaluation tool for circular economies will cover the information required for a techno-economic analysis of mixed biomass pelleting by a review on potential assessment methods, a rough-cut assessment of agro-residues potential for Portugal and gathering the required information about pellets origin, characteristics and legislative frames.
Y. Sheikhnejad, D. Gonçalves, M. Oliveira, and N. Martins
Elsevier BV
Abstract This study addresses a new generation of adaptable intelligent control systems for energy management. The proposed approach consists of a high-level predictive control system based on advanced simulation and optimization algorithms which interact with conventional machine-level controllers of HVAC systems, e.g., PID, in order to define optimized set points considering current and forecasted operation conditions, minimizing a predefined objective cost function, e.g., energy consumption, subjected to maintain predefined levels of comfort. The flexibility of the proposed architecture and the development of reliable surrogate models based on robust machine learning techniques are key features to combine green building requirements while granting or even improving occupant comfort. A first version of the proposed system was developed, and preliminary results emphasize its role in the path of transition to intelligent green buildings as a part of new buildings or, more important, as a retrofit of current buildings, with almost no changes on infrastructures, but promoting them to a smart building level.
Yahya Sheikhnejad, João Simões, and Nelson Martins
MDPI AG
A countless amount of energy has been wasted in all kinds of expansion valves (EV) in industries. In fact, EVs, including regulators, throttling valves, capillary tubes, etc., have been used to intentionally reduce the potential of carrier fluid. City gate stations (CGS) have been recognized as one of the important points with high potential for energy harvesting due to its function for regulating natural gas (NG) pressure by EV. In this study, Tesla turbine (TT) is introduced as a new candidate for substitution of EV, particularly those that have been employed in CGS on high-pressure NG pipelines, as well as those applications in which high-potential fluid must be reduced to a low-potential state to form a complete thermodynamic cycle or to be used at end-user equipment. Although harvesting energy is one of the hottest fields of science and engineering, there are few traces of research on using a TT as an alternative for EVs, even for the industries possessing high-pressure lines. This numerical experiment intends to show the capability of TT as a robust candidate for substituting regulation valves through investigating thermohydrodynamic characteristics of the turbulent high-pressure compressible NG flow through a TT under different operation conditions. This study, with the objective of managing the exploitation of resources, can be considered as one step forward toward reinforcing economic and environmental pillars of sustainable development. It is also found that the generated power by TT can support the 285 7W LED simultaneously, or it is equivalent to 84.4 m2 area of the solar panel (150 W, 15.42% efficiency) for the climate condition of Toronto, Canada.