Contributions to uncertainty reduction in the estimation of PV plants performance

Esta tesis doctoral presenta un procedimiento integral de control de calidad en centrales fotovoltaicas, que comprende desde la fase inicial de estimación de las expectativas de producción hasta la vigilancia del funcionamiento de la instalación una vez en operación, y que permite reducir la incertidumbre asociada su comportamiento y aumentar su fiabilidad a largo plazo, optimizando su funcionamiento. La coyuntura de la tecnología fotovoltaica ha evolucionado enormemente en los últimos años, haciendo que las centrales fotovoltaicas sean capaces de producir energía a unos precios totalmente competitivos en relación con otras fuentes de energía. Esto hace que aumente la exigencia sobre el funcionamiento y la fiabilidad de estas instalaciones. Para cumplir con dicha exigencia, es necesaria la adecuación de los procedimientos de control de calidad aplicados, así como el desarrollo de nuevos métodos que deriven en un conocimiento más completo del estado de las centrales, y que permitan mantener la vigilancia sobre las mismas a lo largo del tiempo. Además, los ajustados márgenes de explotación actuales requieren que durante la fase de diseño se disponga de métodos de estimación de la producción que comporten la menor incertidumbre posible. La propuesta de control de calidad presentada en este trabajo parte de protocolos anteriores orientados a la fase de puesta en marcha de una instalación fotovoltaica, y las complementa con métodos aplicables a la fase de operación, prestando especial atención a los principales problemas que aparecen en las centrales a lo largo de su vida útil (puntos calientes, impacto de la suciedad, envejecimiento…). Además, incorpora un protocolo de vigilancia y análisis del funcionamiento de las instalaciones a partir de sus datos de monitorización, que incluye desde la comprobación de la validez de los propios datos registrados hasta la detección y el diagnóstico de fallos, y que permite un conocimiento automatizado y detallado de las plantas. Dicho procedimiento está orientado a facilitar las tareas de operación y mantenimiento, de manera que se garantice una alta disponibilidad de funcionamiento de la instalación. De vuelta a la fase inicial de cálculo de las expectativas de producción, se utilizan los datos registrados en las centrales para llevar a cabo una mejora de los métodos de estimación de la radiación, que es la componente que más incertidumbre añade al proceso de modelado. El desarrollo y la aplicación de este procedimiento de control de calidad se han llevado a cabo en 39 grandes centrales fotovoltaicas, que totalizan una potencia de 250 MW, distribuidas por varios países de Europa y América Latina. ABSTRACT This thesis presents a comprehensive quality control procedure to be applied in photovoltaic plants, which covers from the initial phase of energy production estimation to the monitoring of the installation performance, once it is in operation. This protocol allows reducing the uncertainty associated to the photovoltaic plants behaviour and increases their long term reliability, therefore optimizing their performance. The situation of photovoltaic technology has drastically evolved in recent years, making photovoltaic plants capable of producing energy at fully competitive prices, in relation to other energy sources. This fact increases the requirements on the performance and reliability of these facilities. To meet this demand, it is necessary to adapt the quality control procedures and to develop new methods able to provide a more complete knowledge of the state of health of the plants, and able to maintain surveillance on them over time. In addition, the current meagre margins in which these installations operate require procedures capable of estimating energy production with the lower possible uncertainty during the design phase. The quality control procedure presented in this work starts from previous protocols oriented to the commissioning phase of a photovoltaic system, and complete them with procedures for the operation phase, paying particular attention to the major problems that arise in photovoltaic plants during their lifetime (hot spots, dust impact, ageing...). It also incorporates a protocol to control and analyse the installation performance directly from its monitoring data, which comprises from checking the validity of the recorded data itself to the detection and diagnosis of failures, and which allows an automated and detailed knowledge of the PV plant performance that can be oriented to facilitate the operation and maintenance of the installation, so as to ensure a high operation availability of the system. Back to the initial stage of calculating production expectations, the data recorded in the photovoltaic plants is used to improved methods for estimating the incident irradiation, which is the component that adds more uncertainty to the modelling process. The development and implementation of the presented quality control procedure has been carried out in 39 large photovoltaic plants, with a total power of 250 MW, located in different European and Latin-American countries.

Barriers to the adoption of photovoltaic systems: The state of the art

Although photovoltaic (PV) systems have become much more competitive, the diffusion of PV systems still remains low in comparison to conventional energy sources. What are the current barriers hindering the diffusion of PV systems? In order to address this, we conducted an extensive and systematic literature review based on the Web of Science database. Our state-of-the-art review shows that, despite the rapid development and maturity of the technology during the past few years, the adoption of PV systems still faces several barriers. The wide adoption of PV systems-either as a substitute for other electricity power generation systems in urban areas or for rural electrification-is a challenging process. Our results show that the barriers are evident for both low- and high-income economies, encompassing four dimensions: sociotechnical, management, economic, and policy. Although the barriers vary across context, the lessons learned from one study can be valuable to others. The involvement of all stakeholders-adopters, local communities, firms, international organizations, financial institutions, and government-is crucial to foster the adoption.

A novel multicomponent regulatory system mediates H2 sensing in Alcaligenes eutrophus

Oxidation of molecular hydrogen catalyzed by [NiFe] hydrogenases is a widespread mechanism of energy generation among prokaryotes. Biosynthesis of the H2-oxidizing enzymes is a complex process subject to positive control by H2 and negative control by organic energy sources. In this report we describe a novel signal transduction system regulating hydrogenase gene (hox) expression in the proteobacterium Alcaligenes eutrophus. This multicomponent system consists of the proteins HoxB, HoxC, HoxJ*, and HoxA. HoxB and HoxC share characteristic features of dimeric [NiFe] hydrogenases and form the putative H2 receptor that interacts directly or indirectly with the histidine protein kinase HoxJ*. A single amino acid substitution (HoxJ*G422S) in a conserved C-terminal glycine-rich motif of HoxJ* resulted in a loss of H2-dependent signal transduction and a concomitant block in autophosphorylating activity, suggesting that autokinase activity is essential for the response to H2. Whereas deletions in hoxB or hoxC abolished hydrogenase synthesis almost completely, the autokinase-deficient strain maintained high-level hox gene expression, indicating that the active sensor kinase exerts a negative effect on hox gene expression in the absence of H2. Substitutions of the conserved phosphoryl acceptor residue Asp55 in the response regulator HoxA (HoxAD55E and HoxAD55N) disrupted the H2 signal-transduction chain. Unlike other NtrC-like regulators, the altered HoxA proteins still allowed high-level transcriptional activation. The data presented here suggest a model in which the nonphosphorylated form of HoxA stimulates transcription in concert with a yet unknown global energy-responsive factor.

Produção de energia por mini e micro hidrelétricas na rede de distribuição de água.

A geração de energia hidrelétrica enfrenta uma crescente restrição a sua expansão, diretamente relacionada a fatores ambientais e da limitação de terrenos com potencial economicamente aproveitável. A partir deste fato, é relacionada uma possível fonte de energia hidrelétrica, resultante do aproveitamento dos potenciais presentes na rede de distribuição de água das cidades, ainda sem nenhum aproveitamento. O desenvolvimento desta fonte de energia se dá com a instalação de mini e micro centrais hidrelétricas nos condutos da rede distribuidora de água. Este trabalho tem por objetivo avaliar o potencial de aproveitamento hidrelétrico por mini e micro hidrelétricas por meio de técnicas de modelagem e de otimização, para agilizar e facilitar o procedimento de identificação dos potenciais e a instalação na rede de abastecimento. O trabalho leva em conta as diversas peculiaridades das redes de distribuição de água e dos equipamentos eletro-hidráulicos, discorrendo sobre a possível complementariedade da geração de energia durante os picos de consumo. Discorre também sobre a contribuição para a rede de distribuição elétrica, na logística e nos custos de implantação além de discutir a tipologia das turbinas capazes de aproveitar o potencial energético. É avaliado, com o auxilio de modelos hidráulicos e de otimização, o posicionamento das centrais geradoras na rede e os possíveis benefícios, restrições e impedimentos ao seu uso, desenvolvendo uma metodologia para facilitar a tomada de decisão quanto ao aproveitamento para geração, ou não, em redes diversas. A construção deste procedimento e ferramenta são desenvolvidos a partir do estudo de caso do sistema distribuidor de água do Município de Piquete no estado de São Paulo, Brasil.

Risco de mercado na comercialização de energia elétrica: uma análise estruturada com foco no ambiente de contratação livre - ACL.

A motivação para o desenvolvimento desse trabalho surge em um momento em que se verifica uma participação cada vez mais significativa das fontes energéticas renováveis não convencionais no País. Não obstante, o cenário de evolução evidencia que o arcabouço regulatório e as regras de mercado não acompanharam as especificidades inerentes à exploração dessas fontes. Assim, para que se mantenha adequado ritmo de inserção na matriz energética, devem ser buscadas opções para que fontes alternativas sejam cada vez mais competitivas na atual configuração do mercado energético. A contribuição dessa pesquisa, portanto, centra-se na análise dos riscos de mercado incorridos por esses geradores de fontes intermitentes de energia ao comercializarem energia no ambiente de contratação livre. Nessa perspectiva, a Dissertação foi desenvolvida abordando tipos de geração de energia e suas características técnicas e econômicas, legislação do setor elétrico, regras de comercialização, balanço energético do sistema, formação de preços no mercado de curto prazo e precificação de contratos no ACL, diferença de preços entre submercados, requisitos de flexibilidade e sazonalidade nos contratos de venda a consumidores livres e seu impacto na precificação de contratos, identificação de comportamento energético complementar para mitigação de riscos de mercado entre fontes renováveis e rebatimento na formulação de mecanismo de hedge, análise de portfólio de contratos e estratégia ótima de contratação de energia para agentes geradores atuando no ACL. Como resposta ao desafio de equacionar o impasse surgido na comercialização de fontes de produção sazonal, propõe-se um modelo para definir estratégias de contratação para agentes geradores e comercializadores a partir da complementação energética entre diferentes tipos de fontes, de forma a maximizar os ganhos de comercialização para um risco estabelecido. Busca-se a composição ideal dessas fontes na carteira de um comercializador para minimizar o risco de exposição à volatilidade dos preços do mercado de curto prazo. Isso é possível em virtude das compensações energéticas feitas entre as diferentes fontes em um portfólio combinado, mitigando a receita em risco decorrente das variações que existem nos preços de curto prazo e na produção energética. De forma complementar, estruturou-se um modelo de negócio no qual uma empresa detentora de ativos de geração hidrelétrica compra os direitos de produção de uma eólica e/ou biomassa para incorporar ao seu portfólio e vender como contrato por quantidade. Determinou-se o volume de energia a ser comprado de cada fonte, o preço, a estratégia mais indicada de contratação e a mitigação de fatores de risco contemplados nos contratos de venda, buscando maximizar os ganhos de comercialização condicionada a critérios de risco pré-fixados.

Developing Autonomous Microgrids: A Theoretical Case Study

Microgrids are autonomously operated, geographically clustered electricity generation and distribution systems that supply power in closed system settings; they are highly compatible with renewable energy sources and distributed generation technologies. Mocrogrids are currently a serially underutilized and underappreciated commodity in the energy infrastructure portfolio worldwide. To demonstrate feasibility under poor conditions (little renewable energy potential and high demand) this capstone project develops a theoretical case study in which a renewable microgrid is employed to power rural communities of southern Montgomery County, Arkansas. Utilizing commercially manufactured 1.5-megawatt wind turbines and a 1-megawatt solar panel generation system, 4-megawatts of lithium ion battery storage, and demand response technology, a microgrid is designed that supplies 235 households with reliable electricity supply.

Electrocatalytic reduction of CO2 to formate using particulate Sn electrodes: Effect of metal loading and particle size

The development of electrochemical processes for the conversion of CO2 into value-added products allows innovative carbon capture & utilization (CCU) instead of carbon capture & storage (CCS). In addition, coupling this conversion with renewable energy sources would make it possible to chemically store electricity from these intermittent renewable sources. The electroreduction of CO2 to formate in aqueous solution has been performed using Sn particles deposited over a carbon support. The effect of the particle size and Sn metal loading has been evaluated using cyclic voltammetry and chronoamperometry. The selected electrode has been tested on an experimental filter-press type cell system for continuous and single pass CO2 electroreduction to obtain formate as main product at ambient pressure and temperature. Experimental results show that using electrodes with 0.75 mg Sn cm−2, 150 nm Sn particles, and working at a current density of 90 mA cm−2, it is possible to achieve rates of formate production over 3.2 mmol m−2 s−1 and faradaic efficiencies around 70% for 90 min of continuous operation. These experimental conditions allow formate concentrations of about 1.5 g L−1 to be obtained on a continuous mode and with a single pass of catholyte through the cell.

Análise do regime de produção distribuída fotovoltaica para autoconsumo

Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2016

Optimização de um sistema híbrido off-grid PV, Gerador Diesel e Baterias

Tese de mestrado integrado, Engenharia da Energia e do Ambiente, Universidade de Lisboa, Faculdade de Ciências, 2016

U.S. Democracy Promotion from Bush to Obama. EUSpring Working Paper No. 1, April 2015

Throughout the twenty-first century the United States (U.S.) has attempted to balance its traditional national security interests, whilst also seeking to promote the long-term transformation of the Middle East and North Africa (MENA) towards democracy based on liberal values. With the September 11, 2001 terrorist attacks providing a catalyst for policy change, the U.S. has moved away from its twentieth-century policy of pursuing a regional status quo and instinctively balking at political change. Yet, the U.S. has not abandoned its reliance on autocratic regimes that cooperate on more immediate national security interests such as counter-terrorism, counter-proliferation, and the free-flow energy sources into the global market. Rather, U.S. democracy promotion in the MENA has become incremental by design and is characterized by its gradualist and often collaborative nature. U.S. foreign policy in the MENA is, therefore, depicted by a cautious evolutionary stance rather than supporting revolutionary shifts in power.

Costs and Benefits of RES in Europe up to 2030. DIA-Core Policy Brief, 24 June 2014

Introduction. This Policy Brief follows-up on the DIA-CORE Policy Brief on “Assessing costs and benefits of deploying renewables”, dated 26 September 2014, which highlighted the complexities in making a comprehensive and appropriate assessment of costs and benefits resulting from an increased use of renewable energy sources (RES). It distinguished the different types of effects into system-related effects, distributional effects and macro-economic effects, and looked at the related data requirements, which need to be comprehensive and standardised. This DIA-CORE Policy Brief uses the tools proposed in the previous Policy Brief to estimate the effects on Member States of reaching the EU-wide RES target of 27% of the EU’s energy consumption by 2030. This allows to draw some conclusions on the differentiated impacts across Member States, and the potential implications for an effort sharing approach. It also assesses whether a higher ambition level could be beneficial. The paper also takes into account the implications of national policy frameworks and highlights the importance of reforms to reduce the costs of RES adoption.

US Democracy Promotion from Bush to Obama. EUSpring Working Paper No. 1, 15 April 2015

Throughout the twenty-first century the United States (U.S.) has attempted to balance its traditional national security interests, whilst also seeking to promote the long-term transformation of the Middle East and North Africa (MENA) towards democracy based on liberal values. With the September 11, 2001 terrorist attacks providing a catalyst for policy change, the U.S. has moved away from its twentieth-century policy of pursuing a regional status quo and instinctively balking at political change. Yet, the U.S. has not abandoned its reliance on autocratic regimes that cooperate on more immediate national security interests such as counter-terrorism, counter-proliferation, and the free-flow energy sources into the global market. Rather, U.S. democracy promotion in the MENA has become incremental by design and is characterized by its gradualist and often-collaborative nature. U.S. foreign policy in the MENA is, therefore, depicted by a cautious evolutionary stance rather than supporting revolutionary shifts in power.

Budget-in-brief /

Description based on: Fiscal year 1997; title from cover.

Modeling and simulation /

Mode of access: Internet.

Programs and services /

Describes grants-in-aid programs of the Bureau's Division of Energy Conservation and Alternative Energy and the Bureau's Division of Recycling and Waste Reduction.