Characterisation and efficiency test of a li-ion energy storage system for PV systems

Li-ion batteries are modern electrical energy storage systems which are undergoing an intense development in their technological features. Their high specific energy, efficiency and durability, together with the lowering of their production costs, are placing them as one of the most promising actors in the field of electrical energy storage technology used as tool for integrating renewable energy sources. But due to the fact that they are in an early stage of development, their reliability must be trusted. This paper describes a method and the results for testing round trip efficiencies of a modern Li-ion battery based energy storage system integrated in a PV system. According to the related standards, the efficiency of a battery and an inverter/charger has been characterised, under technical restrictions and specific operation conditions for its use with PV systems

On the relation between battery size and PV power ramp rate limitation

PV power fluctuations caused by clouds are leading operators of grids with high renewable energy penetration rates to impose ramp rate limitations. Costly battery energy storage systems are used for fulfilling these regulations but the question of the power and energy requirements for accomplishing them has not been fully answered. This work analyses the effects of reducing the size of a battery designed to absorb every fluctuation by taking into consideration, both, the fluctuation occurrence and the penalties in case of non-compliance of a given prescribed ramp-rate limitation. A theoretical analysis was carried out in order to assess the relation between size reduction and ramp rate compliance, obtaining as result a model for predicting the probability of non-compliances with a reduced battery. Additionally, the battery size reduction analysis was applied to the particular grid code currently proposed for Puerto Rico, creating new tools for selecting a battery with reduced power and energy capacity

Surrogate Model of the Optimum Global Battery Pack Thermal Management System Control

_The control of the battery-thermal-management-system (BTMS) is key to prevent catastrophic events and to ensure long lifespans of the batteries. Nonetheless, to achieve a high-quality control of BTMS, several technical challenges must be faced: safe and homogeneous control in a multi element system with just one actuator, limited computational resources, and energy consumption restrictions. To address those challenges and restrictions, we propose a surrogate BTMS control model consisting of a classification machine-learning model that defines the optimum cooling-heating power of the actuator according to several temperature measurements. The la-belled-data required to build the control model is generated from a simulation environment that integrates model-predictivecontrol and linear optimization concepts. As a result, a controller that optimally controls the actuator with multi-input temperature signals in a multi-objective optimization problem is constructed. This paper benchmarks the response of the proposal using different classification machine-learning models and compares them with the responses of a state diagram controller and a PID controller. The results show that the proposed surrogate model has 35% less energy consumption than the evaluated state diagram, and 60% less energy consumption than a traditional PID controller, while dealing with multi-input and multi-objective systems.European Commissio: Grant Agreement No. 824300

Validation of energy management strategies for a BIPV system with a lithium ion battery demonstrator

Study of grid interface in rooftop PV systems with energy storage. The specific objective for this energy strategy is to maximize the consumption of locally produced PV power, hence minimizing the injection of power into the electrical grid

Biomasa hondakinak balioztatzeko prozesu motak

Lan honetan biomasa hondakinak balioztatzeko prozesu nagusiak aztertu dira. Alderaketaren ardatzak honelakoak izan dira: lehengaiaren hezetasuna, erreakzioa burutzeko baldintzak (batik bat, konbertsio-denbora eta tenperatura), lortutako produktuak eta teknologiaren heldutasuna. Biomasa balioztatzeko erabiltzen diren teknologiak bi talde nagusitan banatu daitezke: Termokimikoak eta biokimikoak. Konbertsio termokimikoan oinarritzen diren prozesu nagusiak errekuntza, gasifikazioa, torrefakzioa eta pirolisia dira. Erreakzioak tenperatura altuan egiten direnez, konbertsio-denbora baxua izan ohi da. Komenigarria da prozesu hauetan lehengai lehorrak (basogintza, nekazaritza eta abeltzaintza ustiaketetako hondakinak eta papergintza industriako hondakinak) erabiltzea. Bestalde, prozesu biokimiko edo biologikoetan, mikroorganismoek erreakzioan parte hartzen dute eta lehengai hezeak erabiltzen dira: mindak, gorotzak, araztegietako hondakin uren lohiak eta elikadura-industriako hondakin organikoak. Prozesu nagusiak konpostatzea, digestio anaerobikoa eta hartzidura alkoholikoa dira. Tenperatura baxua izaten da (70ºC baino baxuagoa) eta ondorioz, erreakzio-denbora luzea eta bolumen handiko erreaktorea behar da. Erreakzioak burutzeko, egunak (hartzidura alkoholikoan), asteak (digestio anaerobikoan) edo hilabeteak (konpostatzearen kasuan) behar dira

Biomasa-galdara baten karakterizazio esperimentala eta simulazio dinamikoak

Biomass is one of the available renewable energy sources which can be used for thermal energy generation. In this work, the experimental characterization of a pellet boiler has been carried out, with fixed thermal loads, and also in a dynamic mode. In order to perform the dynamic testing, the thermal energy demands of a building with offices and laboratories have been used. Additionally, a model of the installation has been developed with TRNSYS simulation software. The model of the boiler has been validated with the experimental testing results. That way, the accuracy of the simulation is ensured, and the model can be used to analyze how the boiler would operate in a certain installation.; Energia termikoa lortzeko iturri berriztagarrien artean biomasa daukagu. Lan honetan, pellet galdara baten karakterizazio esperimentala burutu da, bai karga finkoetan, bai modu dinamikoan. Entsegu dinamikoak burutzeko, bulegoak eta laborategiak dauzkan eraikin bateko karga termikoak erabili dira. Bestalde, instalazioaren modeloa garatu da, TRNSYS simulazio programaren bidez. Galdararen modeloa entsegu esperimentalen emaitzen bidez balioztatu da. Horrela, simulazioen zehaztasuna ziurtatzen da, eta modeloa erabil daiteke galdarak instalazio batean nola funtzionatuko lukeen aztertzeko

Hydrogen and Carbon Nanotubes from Pyrolysis-Catalysis of Waste Plastics: A Review

More than 27 million tonnes of waste plastics are generated in Europe each year representing a considerable potential resource. There has been extensive research into the production of liquid fuels and aromatic chemicals from pyrolysis-catalysis of waste plastics. However, there is less work on the production of hydrogen from waste plastics via pyrolysis coupled with catalytic steam reforming. In this paper, the different reactor designs used for hydrogen production from waste plastics are considered and the influence of different catalysts and process parameters on the yield of hydrogen from different types of waste plastics are reviewed. Waste plastics have also been investigated as a source of hydrocarbons for the generation of carbon nanotubes via the chemical vapour deposition route. The influences on the yield and quality of carbon nanotubes derived from waste plastics are reviewed in relation to the reactor designs used for production, catalyst type used for carbon nanotube growth and the influence of operational parameters

Storage size for PV power ramp rate control

Durante los próximos años, se espera integrar una gran cuota de energía fotovoltaica (FV) en redes eléctricas de todo el mundo, gracias al incremento de su competitividad frente a fuentes de energía convencionales. Para alcanzar una integración de FV a gran escala, los problemas de estabilidad y calidad de suministro deben evitarse y su papel en la red tiene que evolucionar hasta convertirse en un agente activo. En concreto, las fluctuaciones de potencia FV causadas por nubes están llamando la atención de operadores de redes con alta tasa de penetración de energías renovables, llevándoles a imponer limitaciones de rampas de potencia. Dichas fluctuaciones se mitigan acoplando sistemas de almacenamiento de energía como baterías, pero todavía tienen un alto coste y su uso puede entorpecer la viabilidad de proyectos FV. En este contexto, el éxito de un proyecto radica en un correcto dimensionado de la batería y en la creación de estrategias y técnicas avanzadas para minimizar los requisitos de almacenamiento. Esta tesis aborda el dimensionado de sistemas de almacenamiento de energía aplicados a mitigar fluctuaciones de potencia de centrales FV para cumplir con una limitación de rampa prescrita. El estudio se basa en el hecho de que las fluctuaciones críticas apenas ocurren, por lo que los requisitos de potencia y capacidad de batería deben minimizarse equilibrando un grado de cumplimiento adecuado y un tamaño de batería práctico. Analiza los efectos de reducir el tamaño de una batería diseñada para absorber todas las fluctuaciones, teniendo en cuenta la ocurrencia de fluctuaciones y la penalización en caso de incumplimiento de rampas. Un análisis exhaustivo evalúa la relación entre la reducción del tamaño y el cumplimiento de rampas, obteniendo como resultado un modelo para predecir la probabilidad de incumplimientos con una batería reducida. Además, el análisis de reducción de tamaño se aplica a la normativa propuesta para Puerto Rico, implementando tres alternativas. El potencial para reducir el tamaño sin incurrir en penalizaciones es alto y sube más si parte de las fluctuaciones ascendentes se absorben limitando los inversores FV. Por lo tanto, se ha creado una estrategia de control avanzada para coordinar la limitación de inversores con una batería reducida, con el propósito de mejorar el índice de cumplimiento de rampas de la central FV. Posteriormente, la técnica de sobredimensionado del generador FV se ha estudiado como solución para mitigar parte de las fluctuaciones. Los resultados muestran que para un mismo tamaño de batería, una combinación adecuada de estas soluciones incrementa la producción FV anual, creando nuevas herramientas para seleccionar una batería de potencia y capacidad reducidas. Por último, la estrategia de control de batería reducida se ha implementado y validado en un laboratorio, abordando aspectos de precisión y de respuesta de control requeridos para implementar el método en una planta FV utility-scale. ABSTRACT During the next years, a large share of PV power is expected to be integrated in worldwide electricity grids by virtue of the increase of its competitiveness against conventional energy sources earlier than expected. In order to achieve a large-scale integration of PV, grid-stability and power quality problems must be avoided, whereas the role of PV power in the grid must be shifted to becoming an active agent. In particular, short-term PV power fluctuations caused by clouds are raising the attention of operators of grids with high renewable energy penetration rates, leading them to impose ramp rate limitations. Such fluctuations are mitigated coupling modern energy storage systems such as batteries, but these devices still have a high cost and their use may hinder the feasibility of PV projects. In this context, the success of a project lies in the correct sizing of the battery and in creating advanced strategies and techniques to minimise the storage requirements. This thesis addresses the sizing of energy storage systems used for mitigating short-term power fluctuations of PV plants to comply with a prescribed ramp rate limitation. The study is based on the fact that strong fluctuations scarcely occur, so battery power and capacity requirements must be minimised according to a trade-off between an adequate grade of compliance and a practical battery size. It analyses the effects of reducing the size of a battery designed to absorb every fluctuation by taking into consideration, both, the fluctuation occurrence and the penalties in case of non-compliance of the ramp-rate limitation. A deep analysis assesses the relation between size reduction and ramp rate compliance, obtaining as result a model for predicting the probability of non-compliances with a reduced battery. Additionally, the size reduction analysis is applied to the particular grid code currently proposed for Puerto Rico, implementing three alternatives. The potential for reducing the size without falling into penalties is high, but it increases if part of the fluctuations can be absorbed by limiting PV inverters during upwards fluctuations. Therefore, an advanced control strategy has been created to team up PV inverter limitations with a reduced battery in order to improve the ramp rate compliance of the plant. Besides, PV array oversizing technique is studied as an alternative to mitigate part of the fluctuations. The results show that for the same storage size, a proper combination of these solutions increases the yearly PV production, creating new tools for selecting a battery with reduced power and energy capacity. Finally, the reduced size battery control strategy is implemented and validated in a laboratory, addressing the accuracy and control response required for implementing the method in a utility-scale PV plant

Biomasa hondakinak balioztatzeko prozesu motak

Lan honetan biomasa hondakinak balioztatzeko prozesu nagusiak aztertu dira. Alderaketaren ardatzak honelakoak izan dira: lehengaiaren hezetasuna, erreakzioa burutzeko baldintzak (batik bat, konbertsio-denbora eta tenperatura), lortutako produktuak eta teknologiaren heldutasuna. Biomasa balioztatzeko erabiltzen diren teknologiak bi talde nagusitan banatu daitezke: Termokimikoak eta biokimikoak. Konbertsio termokimikoan oinarritzen diren prozesu nagusiak errekuntza, gasifikazioa, torrefakzioa eta pirolisia dira. Erreakzioak tenperatura altuan egiten direnez, konbertsio-denbora baxua izan ohi da. Komenigarria da prozesu hauetan lehengai lehorrak (basogintza, nekazaritza eta abeltzaintza ustiaketetako hondakinak eta papergintza industriako hondakinak) erabiltzea. Bestalde, prozesu biokimiko edo biologikoetan, mikroorganismoek erreakzioan parte hartzen dute eta lehengai hezeak erabiltzen dira: mindak, gorotzak, araztegietako hondakin uren lohiak eta elikadura-industriako hondakin organikoak. Prozesu nagusiak konpostatzea, digestio anaerobikoa eta hartzidura alkoholikoa dira. Tenperatura baxua izaten da (70ºC baino baxuagoa) eta ondorioz, erreakzio-denbora luzea eta bolumen handiko erreaktorea behar da. Erreakzioak burutzeko, egunak (hartzidura alkoholikoan), asteak (digestio anaerobikoan) edo hilabeteak (konpostatzearen kasuan) behar dira