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Thermal performance of SS-PCM composites, simulating building envelope conditions, is difficult to asset with traditional laboratory equipment. However, in this work, the evaluation of three SS-PCM based on eutectic fatty acid mixtures of capric-myristic (CA/MA), lauric-myristic (LA/MA) and palmitic-stearic (PA/SA) was accomplished by a testing setup that allows to test samples in steady-state and dynamic conditions. Moreover, a SS-PCM-based acrylic plaster was evaluated as a fiber cement siding finish. The obtained values were used to calculate the thermal transmittance (U-value), heat storage capacity, and thermal inertia parameters under a simulated diurnal cycle. Results showed that the use of phase change materials in powder form increase thermal lag between 148% and 180% and present a decrement factor <0.2. Furthermore, building envelopes as fiber cement siding with a SS-PCM-based acrylic plaster coating decreased 20.8% the indoor temperature, increase 67.26% the thermal lag and decrease 9% of the decrement factor. The authors are pleased to acknowledge the financial assistance of the “Ministerio de Ciencia, Tecnología e Innovación-MINCIENCIAS” through the PhD grant 758-2016-Contract 036–2016, Universidad de Antioquia and Sumicol S.A.S. The work is partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31—MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI) (RED2018-102431-T). This work is partially supported by ICREA under the ICREA Academia programme. Dr. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group GREiA (2017 SGR 1537). GREiA is a certified agent TECNIO in the category of technology developers from the Government of Catalonia.

In this paper a tool for the evaluation of transmission system adequacy is presented. Although similar in the basic assumptions to the classic versions of the Fuzzy Power Flow (FPF), the approach has significant differences in the formulation. First, it is symmetrical (no influence of the slack bus in the results), so all the fuzzy power injections are in the same situation. Second, by including line constraints, only feasible deterministic power flows are accepted in the fuzzy variables calculations, leading to a more correct representation of the possible impact of uncertainty. Third, recalculation of the estimated node fuzzy injections leads to a clear picture of the repressed power flows and thus of the adequacy of the grid. On the other hand, the Constrained Fuzzy Power Flow (CFPF) separates completely the analysis of the network from the generation influence and costs, which is indispensable in a unbundled organization of the power system.

Abstract A method for simulating predictive control of building systems operation in the early stages of building design is presented. The method uses building simulation based on weather forecasts to predict whether there is a future heating or cooling requirement. This information enables the thermal control systems of the building to respond proactively to keep the operational temperature within the thermal comfort range with the minimum use of energy. The method is implemented in an existing building simulation tool designed to inform decisions in the early stages of building design through parametric analysis. This enables building designers to predict the performance of the method and include it as a part of the solution space. The method furthermore facilitates the task of configuring appropriate building systems control schemes in the tool, and it eliminates time consuming manual reconfiguration when making parametric analysis. A test case featuring an office located in Copenhagen, Denmark, indicates that the method has a potential to save energy and improve thermal comfort compared to more conventional systems control. Further investigations of this potential and the general performance of the method are, however, needed before implementing it in a real building design.

Artículos en revistas Units within a control area, participating in the secondary frequency control, are usually spinning generating units already connected to the network and operating outside their range of optimal performance. This paper deals with an alternative method of providing secondary frequency control called rapid-start (RS). It consists in assigning a regulation band to several offline units (RS units) which are capable of being started and connected rapidly, therefore allowing the online units to function more closely to their nominal power. RS units have commonly been used for peaking generation and for tertiary control reserve, and have been rarely used for secondary control reserve. As RS operation may have economic benefits, since it allows for better dispatch of the other units in the control area, an appropriate algorithm to start up an RS unit needs to be developed. This paper proposes a machine learning based system (MLBS) to be employed in the decision to start up an RS unit while being used to provide secondary frequency control. The decision-making procedure is carried out by a decision tree. The building and implementation of the RS machine learning based system is illustrated for a secondary frequency control zone within the Spanish power system. info:eu-repo/semantics/publishedVersion

Analysis of interdependencies in Electric Power Systems (EPS) has been recognized as a crucial and challenging issue to improve their trustworthiness. The recent liberalization process in energy markets has promoted the entry of a variety of operators in the electricity industry. The resulting new organization contributed to increase in complexity, heterogeneity and interconnection. This paper proposes a framework for analyzing EPS organized as a set of interconnected regions, both from the point of view of the electric power grid and of the cyber control infrastructure. The emphasis is on interdependencies and in assessing their impact on indicators representative of the QoS perceived by users. Taking a reference power grid as test case, the effects of failures on selected measures are shown, both in case the grid is partitioned in a number of regions and in case of a single region, to illustrate the behavior of different grid and control configurations.

Wood biomass is turned into industrial fuel through chipping. The efficiency of chipping depends on many factors, including chipper knife wear. Chipper knife wear was determined through a long-term follow-up study, conducted at a waste wood recycling yard. Knife wear determined a sharp drop of productivity (>20%) and a severe decay in product quality. Dry sharpening with a grinder mitigated this effect, but it could not replace proper wet sharpening. Increasing the frequency of wet sharpening sessions determined a moderate increase of knife depreciation cost, but it could drastically enhance machine performance and reduce biomass processing cost. Since benefits largely exceed costs, increasing the frequency of wet sharpening sessions may be an effective measure for reducing overall chipping cost. If the main goal of a chipper operator is to increase productivity and/or decrease fuel consumption, then managing knife wear should be a primary target. (C) 2014 Elsevier Ltd. All rights reserved.

Artículos en revistas In this paper we propose a methodology to approximate closed loop capacity equilibria using only open loop capacity equilibrium models. In the closed loop model, generation companies choose capacities that maximize their individual profit in the first stage while the second stage represents the conjecturedprice- response market equilibrium. In the open loop model, firms simultaneously choose capacities and quantities to maximize their individual profit, while each firm conjectures a price response to its output decisions. The closed loop equilibrium model is an equilibrium problem with equilibrium constraints, which belongs to a class of problems that is very hard to solve. The open loop equilibrium model is much easier to solve, however, it is also less realistic. With the approximation scheme proposed in this paper, we are able to solve the closed loop model reasonably well when market behavior is closer to oligopoly than to perfect competition by smartly employing open loop models which reduces the computational time by two orders of magnitude. We achieve this by transforming the open loop equilibrium problem into an equivalent convex quadratic optimization problem which can be solved efficiently. Finally, a case study is presented in order to validate the proposed approximation scheme. info:eu-repo/semantics/publishedVersion

Abstract Portugal’s performance concerning the Refuse Derived Fuel (RDF) strategy, with particular focus on perspectives for the Northern Region based on the current status of integrated municipal waste management systems in that region, was evaluated. Legal documents, official reports and the market were analyzed. The 2015 national installed capacity of waste treatment technologies, from which the high calorific value fraction (HCVF) for RDF production is obtained, is not far from what was predicted for 2013. However, only around 11% of the HCVF had such destiny and the amount of effectively produced RDF was only 30% of the material sent to RDF production (around 30 kt). In Northern Portugal, no RDF production plant was in operation in 2015; the amount of HCVF was estimated to range from 105 to 204 kt for 2015 and around 2.4 times more is expected in 2020. The strategy laydown for RDF failed so far, and thus, low diversion of waste from landfills is observed, mostly due to low landfill taxes and low HCVF quality, resulting in RDF being non-competitive with the imported higher quality product from countries with very high landfilling fees. Moreover, co-incineration and dedicated recovery solutions are scarce. In the Northern region, the HCVF may be treated in the existing municipal waste incinerator or the RDF might be recovered in new dedicated plants, receiving also non-hazardous waste fractions from other origin. Overall, to ensure a sustainable municipal waste management, the intensification of the reuse, preparation for reuse and recycling of waste components from source segregated collection must be significantly promoted.

Clean combustion technologies, based on reactant dilution, have shown very peculiar and innovative characteristics. Reduction of light and noise emission and uniformity of temperature and composition distribution inside the combustion chamber, related to an extension of the reaction zone, make these processes very promising in several technological fields. Analysis of combustion in very diluted conditions is needed for a general understanding of these processes, which remain unknown from many aspects. The study is also useful for the identification of practical constraints which define the most suitable reactor configurations and working parameters for process reliability. The present work deals with a theoretical analysis of methane oxidation in diluted conditions using one of the detailed kinetic schemes available in the literature. A well-stirred reactor (WSR) configuration has been considered as a first attempt of process schematization. This choice is consistent with the experimental characterization of the flameless combustion processes. The influence of residence time, C/O ratio, and inlet temperature on the steady state was studied for an oxygen molar fraction (0.05), chosen as representative of flameless combustion processes. It has been pointed out that only rich conditions (C/O ? 0.25) are possible for WSR creation, because they allow partial methane conversion. Three kinetic regimes, related to different temperature ranges, have been identified on the basis of product distribution analysis. Both the oxidation and pyrolitic regimes, occurring respectively in low- and high-temperature ranges, are the most interesting working conditions for diluted combustion. The former, leading to CO and H2O as main reaction products, is suitable for reburning technology. The latter, which corresponds to large production of CO and H2, has been shown to be a reasonable explanation of flameless combustion. Advantages and potentials of this innovative process are analyzed, taking into account the kinetic pathway followed in the different working conditions.