Economic optimization of wind farms in function of the cost of energy produced

Esta tese apresenta um estudo sobre otimização económica de parques eólicos, com o objetivo de obter um algoritmo para otimização económica de parques eólicos através do custo da energia produzida. No estudo utilizou-se uma abordagem multidisciplinar. Inicialmente, apresentam-se as principais tecnologias e diferentes arquiteturas utilizadas nos parques eólicos. Bem como esquemas de funcionamento e gestão dos parques. São identificadas variáveis necessárias e apresenta-se um modelo dimensionamento para cálculo dos custos da energia produzida, tendo-se dado ênfase às instalações onshore e ligados a rede elétrica de distribuição. É feita uma análise rigorosa das características das topologias dos aerogeradores disponíveis no mercado, e simula-se o funcionamento de um parque eólico para testar a validade dos modelos desenvolvidos. Também é implementado um algoritmo para a obtenção de uma resposta otimizada para o ciclo de vida económico do parque eólico em estudo. A abordagem proposta envolve algoritmos para otimização do custo de produção com multiplas funções objetivas com base na descrição matemática da produção de eletricidade. Foram desenvolvidos modelos de otimização linear, que estabelece a ligação entre o custo económico e a produção de eletricidade, tendo em conta ainda as emissões de CO2 em instrumentos de política energética para energia eólica. São propostas expressões para o cálculo do custo de energia com variáveis não convencionais, nomeadamente, para a produção variável do parque eólico, fator de funcionamento e coeficiente de eficiência geral do sistema. Para as duas últimas, também é analisado o impacto da distribuição do vento predominante no sistema de conversão de energia eólica. Verifica-se que os resultados obtidos pelos algoritmos propostos são similares às obtidas por demais métodos numéricos já publicados na comunidade científica, e que o algoritmo de otimização económica sofre influência significativa dos valores obtidos dos coeficientes em questão. Finalmente, é demonstrado que o algoritmo proposto (LCOEwso) é útil para o dimensionamento e cálculo dos custos de capital e O&M dos parques eólicos com informação incompleta ou em fase de projeto. Nesse sentido, o contributo desta tese vem ser desenvolver uma ferramenta de apoio à tomada de decisão de um gestor, investidor ou ainda agente público em fomentar a implantação de um parque eólico.

Disseminated M. avium complex infection in the Swiss HIV Cohort Study: declining incidence, improved prognosis and discontinuation of maintenance therapy.

Introduction of potent antiretroviral combination therapy (ART) has reduced overall morbidity and mortality amongst HIV-infected adults. Some prophylactic regimes against opportunistic infections can be discontinued in patients under successful ART. (1) The influence of the availability of ART on incidence and mortality of disseminated M. avium Complex infection (MAC). (2) The safety of discontinuation of maintenance therapy against MAC in patients on ART. The Swiss HIV-Cohort Study, a prospective multicentre study of HIV-infected adults. Patients with a nadir CD4 count below 50 cells/mm3 were considered at risk for MAC and contributed to total follow-up time for calculating the incidence. Survival analysis was performed by using Kaplan Meier and Cox proportional hazards methods. Safety of discontinuation of maintenance therapy was evaluated by review of the medical notes. 398 patients were diagnosed with MAC from 1990 to 1999. 350 had a previous CD4 count below 50 cells/mm3. A total of 3208 patients had a nadir CD4 count of less than 50 cells/mm3 during the study period and contributed to a total follow-up of 6004 person-years. The incidence over the whole study period was 5.8 events per 100 person-years. In the time period of available ART the incidence of MAC was significantly reduced (1.4 versus 8.8 events per 100 person-years, p < 0.001). Being diagnosed after 1995 was the most powerful predictor of better survival (adjusted hazard ratio for death: 0.27; p < 0.001). None of 24 patients discontinuing maintenance therapy while on ART experienced recurrence of MAC during a total follow-up of 56.6 person-years (upper 95% confidence limit 5.3 per 100 person-years). Introducing ART has markedly reduced the risk of MAC for HIV-infected individuals with a history of very low CD4 counts. Survival after diagnosis of MAC has improved after ART became available. In patients responding to ART, discontinuation of maintenance therapy against M. avium may be safe.

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level from London to St. Catharines, April 1847.

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level

Handwritten sheet of paper detailing the cost of transporting boxes containing the Gravatt’s level from London to St. Catharines. This sheet is signed by S.D. Woodruff, Jan. 11, 1847.

Approximate cost of completing the railway from Port Dalhousie to St. Catharines and an estimate of the cost of the piers at Port Dalhousie signed by William Hamilton Merritt

Approximate cost of completing the railway from Port Dalhousie to St. Catharines and an estimate of the cost of the piers at Port Dalhousie signed by William Hamilton Merritt (5 pages, handwritten), July 8, 1854.

Approximate estimate of the cost of completing the Port Dalhousie Railway to the Grand Central Railway Station at Lock 12

Approximate estimate of the cost of completing the Port Dalhousie Railway to the Grand Central Railway Station at Lock 12. This document is badly torn and burned but most of the text is legible, July 14, 1854.

Estimated cost of the Port Dalhousie and Thorold Railway sent to George Rykert by S.D. Woodruff

Estimated cost of the Port Dalhousie and Thorold Railway sent to George Rykert by S.D. Woodruff, Aug. 5, 1854.

Approximate estimate of the cost of constructing and completing the Port Dalhousie and Thorold Railway to St. Catharines

Approximate estimate of the cost of constructing and completing the Port Dalhousie and Thorold Railway to St. Catharines signed by S.D. Woodruff (2 pages, handwritten), Jan. 8, 1855.

Cost of the railway from Port Dalhousie to St. Catharines

Cost of the railway from Port Dalhousie to St. Catharines (1 page, handwritten), Jan. 11, 1855.

Approximate estimate of the cost of extending the Port Dalhousie and Thorold Railway from Geneva Street to the Great Western Railway Station at Lock no. 12

Approximate estimate of the cost of extending the Port Dalhousie and Thorold Railway from Geneva Street to the Great Western Railway Station at Lock no. 12 (2 copies) [one appears to be a rough copy] (2 pages, handwritten), Feb. 2, 1855.

Letter of estimate sent to S.D. Woodruff for the total cost of construction and equipment of the extension of the line to Port Colborne

Letter of estimate sent to S.D. Woodruff for the total cost of construction and equipment of the extension of the line to Port Colborne [this is unsigned]. There is an envelope with this letter that suggests that it is from Mr. Shanly, Mar. 12, 1857.

Chart of estimate of cost of Port Dalhousie and Thorold Railway extension Line no. 1

Chart of estimate of cost of Port Dalhousie and Thorold Railway extension Line no. 1 signed by Mr. Shanly, Mar. 12, 1857.

Chart of the estimated cost of Line no. 1

Chart of the estimated cost of Line no. 1, n.d.

Chart outlining Port Dalhousie and Thorold Railway cost of planks, bridge, railway crossing and approaches thereto

Chart outlining Port Dalhousie and Thorold Railway cost of planks, bridge, railway crossing and approaches thereto, n.d.

Approximate estimate of the cost of macadamizing, grading, bridging and putting in culverts from Hurst’s Bridge above Thorold to Port Robinson

Approximate estimate of the cost of macadamizing, grading, bridging and putting in culverts from Hurst’s Bridge above Thorold to Port Robinson (2 pages, handwritten), n.d.