Erinevate energia salvestustehnoloogiate uudsed rakenduspõhimõtted liginullenergiahoonetes

A Thesis for applying for the degree of Doctor of Philosophy in Technical Sciences.In this thesis the renewable energy storage options in residential buildings are under investigation. This is to store cheap electricity due to the temporary overproduction of large wind farms and also on-site solar and wind farms. In an electric system, there should be a balance at all times between energy production and consumption: as much as is produced should also be consumed. Deviating significantly from this balance can damage electrical equipment or cause serious network failures and even blackouts. Unfortunately, both solar and wind energy generation possibilities are associated with (rapid) changes in production. The simplest examples are wind gusts for wind turbines and intermittent cloud cover for solar panels where the electric output power changes in seconds. In order to smooth out the rapid changes in electricity production, the work proposes the possibility to add ultracapacitors to the battery bank for temporary energy storage, which would act as a buffer and are able to temporarily store the produced electricity. So far, the sale of green energy to the electricity grid has been supported at the state level. However, this paper examines the next step in how to support the storage capacity of the produced energy in order to increase self-consumption. To this, a state subsidy measure for battery banks is proposed. Due to short-term overproduction of electricity, there are more and more situations where electricity is sold at zero or even negative prices on the power exchange. The reason is simple - it is more practical for producers to temporarily pay to consumers for electricity consumption than to stop production for a while. This work also proposes a method for storing energy in heat carriers under favorable conditions for the consumer in order to ensure a balance between the production and consumption of the electricity network.Antud doktoritöö käsitleb taastuvenergia salvestusvõimaluste kasutamist elumajades. Seda nii kohapealsete päikeseparkide ja tuulegeneraatorite kui ka suurte tuuleparkide aeg-ajalisest energia ületootmisest tingitud odava elektrienergia salvestamiseks. Energia tootmise ja tarbimise puhul peaks valitsema igas hetkes tasakaal: sama palju kui toodetakse tuleb ka tarbida. Kui sellest tasakaalust väga kõrvale kalduda, võib see elektrilisi seadmed kahjustada või esineb tõsiseid võrgurikkeid ja isegi katkestusi. Paraku on aga nii päikese- kui ka tuuleenergia tootmine seotud (kiirete) muutustega toodangus. Lihtsaimad näited selleks on tuulepuhangud tuulegeneraatorite puhul ning vahelduv pilvisus päikesepaneelide puhul mil elektriline väljundvõimsus muutub sekunditega. Tasandamaks kiireid muutusi elektritootmisel, pakutakse töös välja võimalus lisada akupangale energia ajutiseks salvestamiseks ülikondensaatorid, mis käituks puhvrina ning on võimelised toodetud elektrienergiat ajutiselt salvestama. Senini on riiklikul tasandil toetatud roheenergia müüki elektrivõrku. Antud töös uuritakse aga järgmist etappi, kuidas toetada toodetud energia salvestusvõimalusi eesmärgiga suurendada omatarbimist. Selleks pakutakse välja riiklik akupankade subsideerimise meede. Elektrienergia lühiajalisest ületootmisest tulenevalt esineb üha rohkem olukordi, mil elektribörsil müüakse elektrit null või isegi negatiivse hinnaga. Põhjus on lihtne – tootjatel on otstarbekam ajutiselt elektritarbimisele peale maksta, kui tootmine korraks seisma panna. Antud töös pakutakse samuti välja meetod, kuidas tarbijale soodsatel tingimustel energiat soojuskandjatesse salvestada, tagamaks elektrivõrgu tootmise ja tarbimise tasakaalu.Publication of this theisis is supported by the Estonian University of Life Sciences; and the Doctoral School of Energy and Geotechnology III, (Estonian University of Life Sciences ASTRA project “Valuechain based bio-economy”); and the Estonian Centre of Excellence in Zero Energy and Resource Efficient Smart Buildings and Districts, ZEBE, grant 2014-2020.4.01.15-0016 funded by the European Regional Development Fund

Coordinated and optimized voltage management of distribution networks with multi-microgrids

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 201

Mini Wind Harvester and a Low Power Three-Phase AC/DC Converter to Power IoT Devices: Analysis, Simulation, Test and Design

Wind energy harvesting is a widespread mature technology employed to collect energy, but it is also suitable, and not yet fully exploited at small scale, for powering low power electronic systems such as Internet of Things (IoT) systems like structural health monitoring, on-line sensors, predictive maintenance, manufacturing processes and surveillance. The present work introduces a three-phase mini wind energy harvester and an Alternate Current/Direct Current (AC/DC) converter. The research analyzes in depth a wind harvester’s operation principles in order to extract its characteristic parameters. It also proposes an equivalent electromechanical model of the harvester, and its accuracy has been verified with prototype performance results. Moreover, unlike most of the converters which use two steps for AC/DC signal conditioning—a rectifier stage and a DC/DC regulator—this work proposes a single stage converter to increase the system efficiency and, consequently, improve the energy transfer. Moreover, the most suitable AC/DC converter architecture was chosen and optimized for the best performance taking into account: the target power, efficiency, voltage levels, operation frequency, duty cycle and load required to implement the aforementioned converter

Energy Harvesting Techniques for Small Scale Environmentally-Powered Electronic Systems

The continuous advances in integrated circuit fabrication technologies, circuit design, and networking techniques enable the integration of an in-creasing number of functionalities in ever smaller devices. This trend de-termines the multiplication of possible application scenarios for tiny em-bedded systems such as wireless sensors, whose utilization has grown more and more pervasive. However, the operating life time of such sys-tems, when placed in locations not allowing a wired connection to a de-pendable power supply infrastructure, is still heavily limited by the finite capacity of currently available accumulators, whose technology has not improved at the same pace of the electronic systems they supply. Energy harvesting techniques constitute a real solution to power un-tethered computing platforms in this kind of spatially-distributed applica-tions. By converting part of the energy freely available in the surrounding environment to electrical energy, the operating life of the system can be extended considerably, potentially for an unlimited time. In recent years an increasing number of researchers have investigated this possibility. In this dissertation we discuss our results about the study and design of systems capable of harvesting energy from various regenerative sources. We start with the design of an airflow energy harvester, focusing on the optimization of its power generation and efficiency performances, and obtaining superior results with respect to similar works in literature. Then we deal with the improvement of this architecture to implement a fully autonomous vibrational harvester, featuring uncommon in-the-field configuration capabilities. Afterwards we investigate the applicability of self-powered wireless sensor nodes to heavy duty and agricultural machinery, finding attractive vibration sources capable of providing enough power to sustain remarkable data transmission rates. To address remote monitoring applications with stringent needs in terms of power supply availability, we present a truly flexible multi-source energy harvester, along with a simulation framework expressly developed to anticipate the harvester performance when placed in a specific operating environment. Furthermore, the design strategies allowing energy harvesters to fully exploit the locally generated power can be profitably applied in the field of distributed electricity generation from renewable energy sources, to enhance the self-consumption capabilities of microgeneration systems. Based on this motivation, we finally propose a grid-assisted photovoltaic power supply to improve the self-sustainability of ground-source heat pumps, and analyze original data on the consumption profiles of these systems to assess the effectiveness of the design. Energy harvesting techniques have the potential to enable many cut-ting-edge applications, especially in remote sensing and pervasive computing areas, which can bring innovations in several fields of human activity. In this thesis we contribute tackling some of the numerous open research challenges still hampering the widespread adoption of this technology

An Integrated AC-DC Rectifier Converter for Low Voltage Piezoelectric Energy Harvesting and Constant-Voltage Lithium-Ion Cell Charging Application

Energy harvesting is probably one the most sought after solutions that is being given attention to and has become of great importance for last few years. Due to advances in microelectronics and growing demand of autonomous devices, researchers have been working on harvesting energy from ambient sources such as solar, thermal, wind and kinetic energy. Also, growth of rechargeable battery technology has resulted in research in ambient energy harvesting for charging purposes. In this field, piezoelectric effect has been identified as a viable solution to address both low power applications and battery charging applications. Piezoelectric effect is described as the phenomenon of generating a voltage from a mechanical stress and vice-versa. Piezoelectric elements have been seen to offer outstanding performance in scavenging energy because of their high power density, which make them suitable for integrated micro-generators. Many vibration-based harvesting technology use piezoelectric transducers as AC power source. This work emphasizes on vibration based piezoelectric energy harvesting from a very low input voltage source. The main objective of the thesis is to design a power converter that can successfully rectify and boost piezoelectric AC voltages from a few hundred millivolts to a stable usable DC voltage without the use of a bridge diode rectifier circuit. The thesis begins with the introduction to the concept of energy harvesting and piezoelectricity, followed by investigation of a 13x25 mm, 28µm thick, laminated piezoelectric thin film made of Polyvinylidene Fluoride (PVDF) acting as the transducer. The transducer was subjected to a repeated vibration impulse and its resultant voltage response was determined. The thesis then moves towards presenting an integrated AC-DC rectifier converter which eliminates the use of full bridge diode rectifiers that have been known for being inefficient for low power energy harvesting. The stages of operation of the power converter is presented along with the simulation results. The work has also been extended to show the charging application of a Lithium-Ion thin film cell under constant voltage charging scheme using a MATLAB/SIMULINK battery model. A prototype of the converter was also built in the laboratory and presented to show the performance of the integrated AC-DC rectifier converter. A dSPACE controller board was employed to implement the open loop control and the converter switching scheme. Experimental results were presented and assessed before finally moving onto the conclusion and suggested future works

Management strategies of electric vehicles and Concentrating Photovoltaic systems for microgrids

The present PhD dissertation is focused on the development of management strate- gies of electric vehicles and concentrating photovoltaic systems in microgrids (MGs). Firstly the MG concept and then the state-of-the-art analysis of the most important components (that are photovoltaic and energy storage systems and electric vehicles) are presented. Then, the first part of the thesis is focused on the concentrating photovoltaic (CPV) systems, the most promising new technology for improving the efficiency of PV systems. In particular, two prototypes characterization and the role of CPV systems in MGs are introduced. In fact, the knowledge of the CPV issues highlighted during the characterization process allows the development of a suitable EMS, in order to guarantee the quality, the reliability and the controllability of the MG and consequently of the main electrical power system, especially in presence of a large number of renewable energy sources (RESs). The second part of the dis- sertation deals with the analysis of two battery electric vehicles (BEVs) models. Nowadays, the exploitation of BEVs has to be placed in a future contest in which the vehicle batteries will perform different tasks in addition to driving purpose, such as the vehicle to grid (V2G) paradigm. Thus, an accurate model that reproduces the battery behavior under real dynamic driving conditions is mandatory, as well as its validation. Moreover, the EV modelling allows to make the EV feedback in- formation reliable for managing correctly and profitably an EV eet inside a MG. Consequently, in the last part, two management strategies (MSs) are presented. The former operates in a MG composed by office and laboratory loads, a CPV plant and a traditional at-plate PV one and a BEV eet. The MS proposed aims to maxi- mize the energy self-consumption by respecting both the driver needs and the MG requirements. The second MS manages the same MG by employing a stationary storage system instead of a BEV eet. In this case, the MS purpose is to guarantee a at-programmable power production profile at the DC node of the MG, even in case of severe weather conditions

Power Electronics Applications in Renewable Energy Systems

The renewable generation system is currently experiencing rapid growth in various power grids. The stability and dynamic response issues of power grids are receiving attention due to the increase in power electronics-based renewable energy. The main focus of this Special Issue is to provide solutions for power system planning and operation. Power electronics-based devices can offer new ancillary services to several industrial sectors. In order to fully include the capability of power conversion systems in the network integration of renewable generators, several studies should be carried out, including detailed studies of switching circuits, and comprehensive operating strategies for numerous devices, consisting of large-scale renewable generation clusters

Energy Management of Distributed Generation Systems

The book contains 10 chapters, and it is divided into four sections. The first section includes three chapters, providing an overview of Energy Management of Distributed Systems. It outlines typical concepts, such as Demand-Side Management, Demand Response, Distributed, and Hierarchical Control for Smart Micro-Grids. The second section contains three chapters and presents different control algorithms, software architectures, and simulation tools dedicated to Energy Management Systems. In the third section, the importance and the role of energy storage technology in a Distribution System, describing and comparing different types of energy storage systems, is shown. The fourth section shows how to identify and address potential threats for a Home Energy Management System. Finally, the fifth section discusses about Economical Optimization of Operational Cost for Micro-Grids, pointing out the effect of renewable energy sources, active loads, and energy storage systems on economic operation

Micro Combined Heat and Power Units in the UK: Feasibility Assessment Using Real Time Pricing and Analysis of Related Policies

This thesis considers the techno-economic feasibility of micro combine heat and power (micro-CHP) units within individual dwellings. A cost-minimisation unit-commitment control strategy is applied so that units are operated in their most advantageous fashion in various scenarios. A variety of dwelling types and energy needs were modelled (with data from the Carbon Trust field trial) and a set of sample days chosen to represent seasonal changes. Four different micro-CHP technologies were examined and thermal storage and auxiliary heating considered. The objective was to establish whether a possible introduction of Real Time Pricing (RTP) of energy would affect the viability of micro-CHP and to establish which, if any, support mechanisms might be appropriate. The results show that fuel cell micro-CHPs out-performed the engine-based micro- CHP in most aspects. Low heat to electricity ratio is a desired characteristic given that the electricity price is typically significantly higher than that of gas and a higher production of on-site electricity is favourable. The results show that significant reduction in energy bills (electricity and gas) are possible under RTP compared to fixed tariffs but, in most cases, are not sufficient to cover the capital costs of the micro-CHP. Adoption of micro-CHP becomes tenable when financial incentives such as capital grants and operational cost support (such as Feed in Tariffs, FiT) exist. The results show FiT to be effective from both the consumers’ and a government’s points of view. However, operational cost support alone might not be sufficient to encourage uptake of micro-CHPs and therefore a loan scheme, which supports the initial cost, should be implemented in parallel. A study of CO2 emissions showed that the extent emissions reduction contributed by micro-CHPs is strongly dependent on the type of micro-CHP used and somewhat less influenced by the price of energy