626 research outputs found

    Hydropower Potential for Energy Recovery in Wastewater Systems. Assessment Methodology and Practical Application

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    Tesis por compendio[ES] Los Objetivos de Desarrollo Sostenible (ODS) plantean un llamamiento global para conseguir la sostenibilidad en aspectos esenciales de la vida humana. El actual consumo de energía para el tratamiento de aguas residuales es muy elevado, y las previsiones apuntan a un incremento de la demanda en la próxima década. En este contexto, resulta necesario aplicar la perspectiva de sostenibilidad, para conseguir de forma simultánea todos los ODS. Un desempeño energético más sostenible de las Estaciones Depuradoras de Aguas Residuales (EDAR) implica acciones en dos líneas, reducir el consumo, y generar energías renovables in situ. Para implantar medidas a corto plazo, es necesario explorar las posibilidades que pueden ofrecer las tecnologías ya maduras, y evaluar su potencial contribución a la descarbonización del sector. La generación de electricidad mediante maquinaria hidráulica aprovechando la energía potencial de los efluentes podría ser una de ellas. El principal objetivo de esta tesis doctoral consiste en desarrollar una metodología, dirigida a los agentes de gobernanza, para evaluar el potencial de generación de energía hidráulica en EDAR, considerando las tres dimensiones de sostenibilidad. De este modo, poder ilustrar las posibilidades de aplicación de esta tecnología, actualmente poco conocida para el sector, que podría contribuir a una gestión más sostenible de las aguas residuales. Las fases desarrolladas incluyeron: 1) Contextualización: Se revisó el estado del arte sobre las necesidades energéticas y las tecnologías para la generación de energía renovable en EDAR. Paralelamente sobre el estado de la tecnología para la recuperación de energía en redes de agua existentes mediante maquinaria hidráulica. Para completar este marco, la revisión se amplió con una búsqueda exhaustiva de casos de estudio reales de aplicación en EDAR. En esta fase se identificaron 49 casos de estudio y se analizó su desempeño energético. Los resultados de esta fase en general demostraron que existe una experiencia real en la aplicación práctica de esta tecnología que no se está utilizando para el desarrollo de todo su potencial en este sector. 2) Desarrollo de la metodología: Se analizaron las metodologías existentes para evaluación del potencial de esta tecnología, y el resultado se comparó con la información obtenida en la contextualización. Como resultado, durante esta tesis se ha desarrollado una metodología con una nueva perspectiva. En primer lugar, se introduce la necesidad de considerar el nivel al que se produce la toma de decisiones, para adaptar el alcance del estudio (un grupo de EDAR). A continuación, la metodología se desarrolla en dos etapas. En la etapa 1 (evaluación técnica) el potencial de generación de energía hidráulica se estima de forma individual para cada EDAR. En la etapa 2 (evaluación global) se propone un método de decisión multicriterio (MCDA) introduciendo criterios de sostenibilidad. La alineación de la metodología con su contexto de aplicación se considera una cuestión clave, de modo que el método propuesto se basa en las directrices del instrumento de gobernanza para aguas residuales en España (Plan DSEAR). 3) Aplicación práctica: Esta fase completa el estudio con la aplicación a un grupo de 186 EDAR de la Comunidad Valenciana (España), con la misma modalidad de financiación. Se estimó una generación de electricidad de 340,472 kWh/año, aunque como hallazgo se observó la posibilidad de que dicho potencial sea mayor. En la etapa 2 se mostró que, cuando los resultados de la etapa 1 se ponen en el contexto de sostenibilidad, se obtiene una nueva perspectiva. Esta investigación demuestra que, en el marco de los ODS, la recuperación de energía hidráulica del agua residual podría ser una opción más en la descarbonización de este sector. Tomando como base esta propuesta, agentes de gobernanza para la gestión de aguas residuales en otro contexto podrían desarrollar metodologías similares adaptadas a su propio entorno.[CA] Els Objectius de Desenvolupament Sostenible (ODS) plantegen una crida global per a aconseguir la sostenibilitat en aspectes essencials de la vida humana. L'actual consum d'energia per al tractament d'aigües residuals és molt elevat, i les previsions apunten a un increment de la demanda en la dècada vinent. En este context, resulta necessari aplicar la perspectiva de sostenibilitat, per a aconseguir de manera simultània tots els ODS. Un acompliment energètic més sostenible de les Estacions Depuradores d'Aigües Residuals (EDAR) implica accions en dues línies, reduir el consum, i generar energies renovables in situ. Per a implantar mesures a curt termini, és necessari explorar les possibilitats que poden oferir les tecnologies ja madures, i avaluar la seua potencial contribució a la descarbonització del sector. La generació d'electricitat mitjançant maquinària hidràulica aprofitant l'energia potencial dels efluents podria ser una d'elles. El principal objectiu d'esta tesi doctoral consisteix a desenvolupar una metodologia, dirigida als agents de governança, per a avaluar el potencial de generació d'energia hidràulica en EDAR, considerant les tres dimensions de sostenibilitat. D'aquesta manera, poder il·lustrar les possibilitats d'aplicació d'esta tecnologia, actualment poc coneguda per al sector, que podria contribuir a una gestió més sostenible de les aigües residuals. Les fases desenvolupades van incloure: 1) Contextualització: Es va revisar l'estat de l'art sobre les necessitats energètiques i les tecnologies per a la generació d'energia renovable en EDAR. Paral·lelament sobre l'estat de la tecnologia per a la recuperació d'energia en xarxes d'aigua existents mitjançant maquinària hidràulica. Per a completar este marc, la revisió es va ampliar amb una cerca exhaustiva de casos d'estudi reals d'aplicació en EDAR. En esta fase es van identificar 49 casos d'estudi i es va analitzar el seu acompliment energètic. Els resultats d'esta fase en general van demostrar que existeix una experiència real en l'aplicació pràctica d'esta tecnologia que no s'està utilitzant per al desenvolupament de tot el seu potencial en este sector. 2) Desenvolupament de la metodologia: Es van analitzar les metodologies existents per a avaluació del potencial d'esta tecnologia, i el resultat es va comparar amb la informació obtinguda en la contextualització. Com a resultat, durant esta tesi s'ha desenvolupat una metodologia amb una nova perspectiva. En primer lloc, s'introdueix la necessitat de considerar el nivell al qual es produeix la presa de decisions, per a adaptar l'abast de l'estudi (un grup de EDAR). A continuació, la metodologia es desenvolupa en dues etapes. En l'etapa 1 (avaluació tècnica) el potencial de generació d'energia hidràulica s'estima de manera individual per a cada EDAR. En l'etapa 2 (avaluació global) es proposa un mètode de decisió multicriteri (MCDA) introduint criteris de sostenibilitat. L'alineació de la metodologia amb el seu context d'aplicació es considera una qüestió clau, de manera que el mètode proposat es basa en les directrius de l'instrument de governança per a aigües residuals a Espanya (Pla DSEAR). 3) Aplicació pràctica: Esta fase completa l'estudi amb l'aplicació a un grup de 186 EDAR de la Comunitat Valenciana, amb la mateixa modalitat de finançament. Es va estimar una generació d'electricitat de 340,472 kWh/any, encara que com a troballa es va observar la possibilitat que aquest potencial siga major. En l'etapa 2 es va mostrar que, quan els resultats de l'etapa 1 es posen en el context de sostenibilitat, s'obté una nova perspectiva. Esta investigació demostra que, en el marc dels ODS, la recuperació d'energia hidràulica de l'aigua residual podria ser una opció més en la descarbonització d'este sector. Prenent com a base esta proposta, agents de governança per a la gestió d'aigües residuals en un altre context podrien desenvolupar metodologies similars adaptades al seu propi entorn.[EN] The Sustainable Development Goals establish a universal agenda to call for action and achieve sustainability in essential aspects of human life. Nowadays the energy demand for wastewater treatment is very high and it is expected to increase in the next decade. Therefore, the performance of this industry will have an effect on SDG 6, but also on SDG 7 and 13. In this context, it is necessary to apply the sustainability approach to wastewater systems to simultaneously achieve all these goals. More sustainable energy performance of wastewater treatment plants (WWTPs) implies two parallel steps: a reduction of energy consumption and the implementation of renewable energy technologies. To take action in the short term, existing mature technologies should be explored to evaluate their potential contribution to the decarbonization roadmaps in the wastewater industry. Hydropower might be one of these technologies. The main objective of this thesis is to develop a methodology, addressed to wastewater governance stakeholders, to assess the potential of hydropower application to WWTPs, regarding all three dimensions of sustainability. According to this, the final aim of this study is to illustrate the practical possibilities, usually unknown, that hydropower could offer to the wastewater sector in the pathway towards more sustainable systems. To achieve that aim, the steps in this research included: 1) Contextualization: The review of the state of the art was conducted in two lines. Firstly, about the energy needs for wastewater treatment and technologies for renewable energy generation. Secondly, about hydropower for energy recovery from existing networks. To complete the framework, this stage was extended with an exhaustive search and analysis of real case studies of hydropower applications to WWTPs. In this stage, 49 case studies were identified, and their energy data were extracted to obtain energy self-sufficiency indicators and analyze their renewable energy profiles. Furthermore, the technical data of their hydropower systems were examined. The overall results of this stage showed that there is an existing experience that is not being used to explore hydropower as an option for energy recovery in the wastewater sector. 2) Methodology development: In a preliminary step, existing methodologies for hydropower potential assessment were analyzed and compared with the framework obtained from the contextualization. As a result, a methodology with a broader approach was developed. First, it introduces the consideration of the decision-making level to select the scope of the study (a group of WWTPs). Then, the proposed methodology consists of two steps. In step 1 (technical assessment of hydropower potential) individual power output is estimated for each site. This step was validated with the data obtained during the contextualization. In step 2 (global assessment), after analyzing existing guidelines, a multi-criteria decision analysis (MCDA) method with sustainability criteria is defined. As the alignment with the context is a key issue introduced in this proposal, this method is based on the guidelines in the wastewater governance instrument in Spain (PDSEAR). 3) Practical application: This stage completes the research with the application of the proposed methodology to a case study, a group of 186 WWTPs in the region of Valencia (Spain), selected according to their management model. The generation was estimated at 340,472 kWh/year, but it was found that the potential could be higher. The results also showed that the perspective may be different, if the outcomes from step 1, are put into context in step 2, with the application of the MCDA method. This research demonstrates that, in a sustainability framework, hydropower might be an interesting option to consider for the decarbonization of wastewater systems. Based on this study, decision-making stakeholders could design their own methodologies, adapted to the specific context.The authors would like to acknowledge grant PID2020–114781RA-I00 funded by MCIN/AEI/ 10.13039/501100011033.Llácer Iglesias, RM. (2023). Hydropower Potential for Energy Recovery in Wastewater Systems. Assessment Methodology and Practical Application [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/201558Compendi

    Safe Multi-Agent Reinforcement Learning with Quantitatively Verified Constraints

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    Multi-agent reinforcement learning is a machine learning technique that involves multiple agents attempting to solve sequential decision-making problems. This learn- ing is driven by objectives and failures modelled as positive numerical rewards and negative numerical punishments, respectively. These multi-agent systems explore shared environments in order to find the highest cumulative reward for the sequential decision-making problem. Multi-agent reinforcement learning within autonomous systems has become a prominent research area with many examples of success and potential applications. However, the safety-critical nature of many of these potential applications is currently underexplored—and under-supported. Reinforcement learn- ing, being a stochastic process, is unpredictable, meaning there are no assurances that these systems will not harm themselves, other expensive equipment, or humans. This thesis introduces Assured Multi-Agent Reinforcement Learning (AMARL) to mitigate these issues. This approach constrains the actions of learning systems during and after a learning process. Unlike previous multi-agent reinforcement learning methods, AMARL synthesises constraints through the formal verification of abstracted multi- agent Markov decision processes that model the environment’s functional and safety aspects. Learned policies guided by these constraints are guaranteed to satisfy strict functional and safety requirements and are Pareto-optimal with respect to a set of op- timisation objectives. Two AMARL extensions are also introduced in the thesis. Firstly, the thesis presents a Partial Policy Reuse method that allows the use of previously learned knowledge to reduce AMARL learning time significantly when initial models are inaccurate. Secondly, an Adaptive Constraints method is introduced to enable agents to adapt to environmental changes by constraining their learning through a procedure that follows the styling of monitoring, analysis, planning, and execution during runtime. AMARL and its extensions are evaluated within three case studies from different navigation-based domains and shown to produce policies that meet strict safety and functional requirements

    A Bi-objective cap-and-trade model for minimising environmental impact in closed-loop supply chains

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    A Closed-Loop Supply Chain (CLSC) is a complex network with unique environmental features and attributes that requires specific managerial policies and strategies. Quantitative models can provide a solid basis for these policies and strategies. This study expands the work of Shoaeinaeini et al. (2021) on Green Supply Chain Management. We propose a bi-objective facility location, demand allocation, and pricing model for CLSC networks. The proposed model considers two conflicting objective functions: maximising profits and minimising emissions. We show consumer environmental awareness can predict the products’ rate of return and determine a more suitable price for new products and the acquisition price for used products. The cap-and-trade policy has been implemented at its fullest potential, allowing the trading of carbon quotas. Therefore, companies may decide to produce less to sell more quotas or vice-versa, effectively picking the most profitable option. The model is solved and tested with the commercial solver BARON. The model effectively shows the trade-off between generating profits and emission reduction. Companies are able to turn a profit while abiding by the government’s intention of reducing emissions. The comparison with a single-objective version of the model highlights that the concurrent optimisation of economic and environmental objectives yields better results. The acquisition price of used products is a value worthy of monitoring. The government should focus on policies to assist the reverse flow of used products

    Logic programming for deliberative robotic task planning

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    Over the last decade, the use of robots in production and daily life has increased. With increasingly complex tasks and interaction in different environments including humans, robots are required a higher level of autonomy for efficient deliberation. Task planning is a key element of deliberation. It combines elementary operations into a structured plan to satisfy a prescribed goal, given specifications on the robot and the environment. In this manuscript, we present a survey on recent advances in the application of logic programming to the problem of task planning. Logic programming offers several advantages compared to other approaches, including greater expressivity and interpretability which may aid in the development of safe and reliable robots. We analyze different planners and their suitability for specific robotic applications, based on expressivity in domain representation, computational efficiency and software implementation. In this way, we support the robotic designer in choosing the best tool for his application

    Learning Reward Machines in Cooperative Multi-Agent Tasks

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    This paper presents a novel approach to Multi-Agent Reinforcement Learning (MARL) that combines cooperative task decomposition with the learning of reward machines (RMs) encoding the structure of the sub-tasks. The proposed method helps deal with the non-Markovian nature of the rewards in partially observable environments and improves the interpretability of the learnt policies required to complete the cooperative task. The RMs associated with each sub-task are learnt in a decentralised manner and then used to guide the behaviour of each agent. By doing so, the complexity of a cooperative multi-agent problem is reduced, allowing for more effective learning. The results suggest that our approach is a promising direction for future research in MARL, especially in complex environments with large state spaces and multiple agents.Comment: Neuro-symbolic AI for Agent and Multi-Agent Systems Workshop at AAMAS'2

    Jornadas Nacionales de Investigación en Ciberseguridad: actas de las VIII Jornadas Nacionales de Investigación en ciberseguridad: Vigo, 21 a 23 de junio de 2023

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    Jornadas Nacionales de Investigación en Ciberseguridad (8ª. 2023. Vigo)atlanTTicAMTEGA: Axencia para a modernización tecnolóxica de GaliciaINCIBE: Instituto Nacional de Cibersegurida

    Tacit knowledge in craft pedagogy: a sociological analysis

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    Though a very silent man he was so mild and calm that Ged soon lost his awe of him, and in a day or two he was bold enough to ask his master 'When will my apprenticeship begin, Sir?' 'It has begun', said Ogion. There was silence, as if Ged was keeping back something he had to say. Then he said it: 'But I haven't learned anything yet!' 'Because you haven't found out what I am teaching,' replied the mage. going on at his steady long-legged pace along their road ... From: The Earthsea Quartet, by Ursula /e Guin This thesis explores the relationship between tacit knowledge and a pedagogy that centres round a master-apprentice relationship, in order to locate tacit craft knowledge within a broader taxonomy of knowledge forms and their transmission practices. By its own definition tacit knowledge constitutes a unique class of phenomenon, namely that which is not presentable in language. It is thus a difficult concept to grasp and an even more difficult concept to represent in words. Evidence from a single qualitative case study on craft transmission practices m the institutional training centre of the Furniture Industry Training Board (known as the 'trade school') in Cape Town is presented and analysed in accordance with a conceptual scheme that derives from the earlier work of Basil Bernstein. Against the background of this analysis of craft pedagogy, the nature of the 'tacit' is explored through a detailed analysis of the evaluative requirements of the final trade test. Thereafter a conceptual model is developed to provide a theoretical explanation for the form that tacit craft knowledge takes. The findings show that strong external 'classification' and 'framing' relations (terms developed by Bernstein) constitute the trade school as a specialised context that is temporarily insulated from the work practices of mass production factories. It is a particular relation between work organisation, tool and materials usage, that retains the traditional craft or trade of cabinet making as the 'identity' recognised as legitimate in the trade school. Internal 'framing' displays two modalities. While strong macro pacing that resembles the daily routine in a factory is maintained throughout the five stages of the apprenticeship II curriculum, very weak initial framing over selection, sequencing and mtcro pacing allows apprentices to develop their own rhythms of work and to make their own decisions about task realisation. However, just before the end of the final stage and before apprentices take their final trade test framing over selection, sequencing and pacing is strengthened and made explicit. Evaluation criteria are very strongly framed in all stages of the apprenticeship curriculum. In terms of the regulative discourse of the trade school the master-apprentice relation is undoubtedly an asymmetrical relation that is mediated through a surrogate kinship role taken on by the master-trainer to exercise a form of positional control. The qualities of character and conduct that are transmitted are those of the autonomous artisan representing a collective craft tradition. The outcome of a strongly classified and framed craft pedagogy that centres round a masterapprentice relationship is found to be an external performance that is grounded or embedded in an internally held competence. Such internalised competence refers to a capacity for visualisation that acts as a proxy for a relationship between 'parts' and 'whole' that cannot be rendered in words. This relationship is held in the body and constitutes what can be called the 'tacit' in craft. The identity of the craft worker or 'tradesman' rests crucially on this combination of external performance and internalised time-space relation. Given this understanding of craft it becomes possible to describe craft as a restricted form of context independent 'knowledge' rather than merely as 'skill'. The conceptual model that is developed in the later part of the thesis locates craft as a form of knowledge that is independent of context in the sense that all craft knowledge realises an order of relation between the features of the object being made that is given by a particular embodied principle of arrangement. It is on this basis that craft takes its place in a systematic taxonomy of knowledge forms, which, although functioning at a fairly high level of abstraction 1s, nevertheless consistent with the empirical findings of the study. Implications of thesis findings and conclusions for an understanding of knowledge and pedagogy more generally are presented in the final chapter
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