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Pegada carbónica e área ocupada para produção de eletricidade em Portugal Continental
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Esta dissertação constitui um estudo de dois indicadores de sustentabilidade associados à geração de energia elétrica em Portugal: a intensidade carbónica e a área ocupada para diversas fontes de produção de eletricidade do mix de geração de energia elétrica de Portugal continental entre os anos de 2015 e 2018. A ordem de grandeza dos valores encontrados foi comparada com as bases de dados de valores standard do IPCC, Ecoinvent, SNIAmb, documentos AIA, e estudos teóricos de forma a comprovar a sua validade. Devido ao facto dos valores tabelados da intensidade carbónica associados à eletricidade produzida por este mix representarem apenas as emissões diretas (e muitas vezes somente as de CO2) associadas à queima de combustíveis fósseis primários na fase de operação, nesta dissertação, a análise deste valor foi expandida de modo a englobar as emissões indiretas e diretas associadas aos diversos materiais utilizados em duas das três fases do ciclo de vida de uma central, as fases de construção e operação, de cada um dos seis tipos de centrais estudadas, e todos os gases com efeito de estufa emitidos, nomeadamente o CO2, CH4, N2O e SF6. Para isso, foram recolhidos e analisados diversos estudos do ciclo de vida das variadas tecnologias utilizadas para produção de eletricidade em diversos pontos do globo, como por exemplo centrais nos Estados Unidos, Brasil, ou China, e diversos valores de fator de emissão associados quer às emissões indiretas, onde foi excluído o transporte, quer às emissões diretas de cada material utilizado. Com estes valores, foi possível estimar dois fatores de emissão distintos, um deles intitulado de fator de emissão direto, que inclui unicamente as emissões diretas da queima do combustível principal utilizado para produção de eletricidade, e o fator correspondente às emissões totais, que inclui as restantes emissões diretas da fase de operação, como por exemplo o uso do refrigerante SF6, bem como as emissões indiretas da fase de operação, por exemplo as correspondentes à extração do combustível de entrada, e as emissões da fase de construção, intitulado de fator de emissão total. Assim, este estudo consiste na análise a seis tecnologias - as centrais hidroelétricas com albufeira de reserva e a fio de água, centrais termoelétricas a carvão e a gás natural, centrais eólicas, e centrais solar fotovoltaicas – sendo que a fronteira do sistema para a pegada carbónica inclui a extração de materiais e a sua transformação, e a construção e operação de cada central, excluindo o transporte de eletricidade pela rede até ao consumidor final. Os fatores de conversão para 𝐶𝑂2𝑒𝑞 respeitam os valores associados ao potencial de aquecimento global, numa base de 100 anos, descritos no quinto relatório do IPCC. Tendo em conta que a média dos valores tabelados entre 2015 e 2018 é equivalente a 307 𝑔 𝐶𝑂2⁄𝑘𝑊ℎ, os resultados obtidos apresentaram valores médios para os dois fatores referidos anteriormente de 397 e 475 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ, respetivamente, o que corresponde a 129% e 155% da média dos valores apresentados ao público. Tal como esperado, as centrais termoelétricas a carvão representam a maior fonte de emissão de gases com efeito de estufa por kWh produzido, com um valor 3 vezes superior às segundas classificadas, as centrais termoelétricas a gás natural, e 39 vezes superior às centrais com o fator de emissão específico mais baixo, as centrais solar fotovoltaicas. Relativamente à área ocupada, cuja fronteira cinge-se à área de construção, foi mapeada a área ocupada pelas centrais ativas no período em estudo e obtiveram-se informações relativas às razões área ocupada por potência instalada, e área ocupada por eletricidade produzida que poderão vir a ser úteis em processos de escolha relacionados com o ordenamento do território. Nesta dissertação foi obtido um mapa com a extensão de Portugal continental no qual se representam as assumidas áreas utilizadas para a produção de energia elétrica, tendo a totalidade destas áreas aumentado de 590 para 623 km2 , semelhante à área do município de Pombal, Leiria. Desta área, em média, 89% é ocupada por centrais hidroelétricas, 8% por centrais eólicas, e os restantes 3% divididos pelas restantes tecnologias. A tecnologia que apresenta valores mais baixos de área ocupada por potência instalada e por eletricidade produzida, representando uma melhor ocupação do espaço utilizado, é a termoelétrica a gás natural, enquanto a tecnologia com valores mais altos é a hidroelétrica com albufeira. Esta dissertação estima que a intensidade carbónica varia de 32 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ para uma central solar fotovoltaica a 1245 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ para uma central termoelétrica a carvão, a razão área ocupada por potência instalada varia de 0,08 𝑚2⁄𝑘𝑊 para uma central termoelétrica a gás natural a 86 𝑚2⁄𝑘𝑊 para uma central hidroelétrica com albufeira, e a razão área ocupada por eletricidade produzida varia de 2 × 10−5 𝑚2⁄𝑘𝑊ℎ para uma central termoelétrica a gás natural a 5 × 10−2 𝑚2⁄𝑘𝑊ℎ para uma central hidroelétrica com albufeira.
This thesis constitutes a study of two sustainability indicators associates with the production of electricity in Portugal: carbon intensity and occupied area for the diverse sources of production in the electric energy generation mix of continental Portugal between the years of 2015 and 2018. The order of magnitude of the calculated values was compared with the standard values present in the databases of IPCC, Ecoinvent, SNIAmb, EIA documents and theoretical studies in order to prove their validity. Since the tabulates values of the carbonic intensity associated to the electricity produced by this mix only represent the direct emissions (and many times just the ones associated with CO2) linked to burning the primary fossil fuels used in the operational phase, in this thesis, the analysis of this value was expanded to include the indirect and direct emissions associated with the various materials used in two of the three phases of the lifecycle of a power plant, the construction and operational phases, of each one of the six types of power plants studied, and all the emitted greenhouse gases, namely CO2, CH4, N2O and SF6. To achieve this, different studies on the life cycle of the various technologies used to produce electricity in different points across the globe, such as the United States, Brazil or China, and various emission factor values associated with both the indirect emissions, where transportation was not included, and direct emissions for each material used were gathered and analyzed. With these values, it was possible to estimate two distinct emission factors, one denominated direct emission factor, that included only the direct emissions associated with burning the main fossil fuel used for the production of electricity, and the factor correspondent to the total emissions, that includes the rest of the direct emissions of the operational phase, such as the usage of the coolant SF6, as well as the indirect emissions in the operational phase, such as the ones corresponding to the extraction of the entry fuel, and the emissions in the construction phase, named total emission factor. Knowing that the average tabulated value between 2015 and 2018 is 307 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ, the results of this thesis show that the average values of the two factors mentioned previously are 397 e 475 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ, respectively, which corresponds to 129% and 155% of the average value presented to the public. As expected, coal powered thermoelectric power plants represent the biggest source for greenhouse gas emissions per kWh produced, with a value 3 times larger than second-placed natural gas-powered thermoelectric power plants, and 39 times larger than solar photovoltaic power plants, the ones with the lowest specific emission factor. So, this study consists of an analysis of six technologies – hydroelectric with reservoir and run-of-river, thermoelectric powered by coal and natural gas, wind, and solar photovoltaic – where the system’s limits for the carbon footprint include the extraction of materials and their transformation, and the construction and operation of each power plant, excluding the transport of electricity via the grid to the final consumer. The conversion factors for 𝐶𝑂2𝑒𝑞 respect the values associated with the global warming potential, on a 100-years base, detailed on the IPCC’s fifth report. In terms of occupied area, whose limits are constrained to the construction area, the area occupied by the active power plants during the study period was mapped and information related to the ratios of area occupied per installed power and area occupied per electricity produced, which might be useful in the choosing process related to land management, was obtained. So, in this thesis, a map with the same geographical extension as the Portuguese mainland was produced to represent the assumed areas used to produce electric energy was created, with the total area growing from 590 to 623 km2 , which is similar to the area of the municipality of Pombal, Leiria. From this area, on average, 89% is occupied by hydroelectric power plant with a reservoir, 8% by wind power plants, and the remaining 3% split between the other technologies. The technology that has the lowest values of occupied area per installed power and per electricity produced, representing a better used of the space it occupies, is natural gas powered thermoelectric, while the technology with the highest values is hydroelectric with reservoir. This thesis estimates that the carbon intensity varies from 32 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ for a solar photovoltaic power plant to 1245 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ for a coal powered thermoelectric power plant, the ratio of area occupied per installed power varies from 0.08 𝑚2⁄𝑘𝑊 for a natural gas powered thermoelectric power plant to 86 𝑚2⁄𝑘𝑊 for a hydroelectric power plant with reservoir, and the ratio of area occupied per electricity produced varies from 2 × 10−5 𝑚2⁄𝑘𝑊ℎ for a natural gas thermoelectric power plant to 5 × 10−2 𝑚2⁄𝑘𝑊ℎ for a hydroelectric power plant with reservoir.
This thesis constitutes a study of two sustainability indicators associates with the production of electricity in Portugal: carbon intensity and occupied area for the diverse sources of production in the electric energy generation mix of continental Portugal between the years of 2015 and 2018. The order of magnitude of the calculated values was compared with the standard values present in the databases of IPCC, Ecoinvent, SNIAmb, EIA documents and theoretical studies in order to prove their validity. Since the tabulates values of the carbonic intensity associated to the electricity produced by this mix only represent the direct emissions (and many times just the ones associated with CO2) linked to burning the primary fossil fuels used in the operational phase, in this thesis, the analysis of this value was expanded to include the indirect and direct emissions associated with the various materials used in two of the three phases of the lifecycle of a power plant, the construction and operational phases, of each one of the six types of power plants studied, and all the emitted greenhouse gases, namely CO2, CH4, N2O and SF6. To achieve this, different studies on the life cycle of the various technologies used to produce electricity in different points across the globe, such as the United States, Brazil or China, and various emission factor values associated with both the indirect emissions, where transportation was not included, and direct emissions for each material used were gathered and analyzed. With these values, it was possible to estimate two distinct emission factors, one denominated direct emission factor, that included only the direct emissions associated with burning the main fossil fuel used for the production of electricity, and the factor correspondent to the total emissions, that includes the rest of the direct emissions of the operational phase, such as the usage of the coolant SF6, as well as the indirect emissions in the operational phase, such as the ones corresponding to the extraction of the entry fuel, and the emissions in the construction phase, named total emission factor. Knowing that the average tabulated value between 2015 and 2018 is 307 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ, the results of this thesis show that the average values of the two factors mentioned previously are 397 e 475 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ, respectively, which corresponds to 129% and 155% of the average value presented to the public. As expected, coal powered thermoelectric power plants represent the biggest source for greenhouse gas emissions per kWh produced, with a value 3 times larger than second-placed natural gas-powered thermoelectric power plants, and 39 times larger than solar photovoltaic power plants, the ones with the lowest specific emission factor. So, this study consists of an analysis of six technologies – hydroelectric with reservoir and run-of-river, thermoelectric powered by coal and natural gas, wind, and solar photovoltaic – where the system’s limits for the carbon footprint include the extraction of materials and their transformation, and the construction and operation of each power plant, excluding the transport of electricity via the grid to the final consumer. The conversion factors for 𝐶𝑂2𝑒𝑞 respect the values associated with the global warming potential, on a 100-years base, detailed on the IPCC’s fifth report. In terms of occupied area, whose limits are constrained to the construction area, the area occupied by the active power plants during the study period was mapped and information related to the ratios of area occupied per installed power and area occupied per electricity produced, which might be useful in the choosing process related to land management, was obtained. So, in this thesis, a map with the same geographical extension as the Portuguese mainland was produced to represent the assumed areas used to produce electric energy was created, with the total area growing from 590 to 623 km2 , which is similar to the area of the municipality of Pombal, Leiria. From this area, on average, 89% is occupied by hydroelectric power plant with a reservoir, 8% by wind power plants, and the remaining 3% split between the other technologies. The technology that has the lowest values of occupied area per installed power and per electricity produced, representing a better used of the space it occupies, is natural gas powered thermoelectric, while the technology with the highest values is hydroelectric with reservoir. This thesis estimates that the carbon intensity varies from 32 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ for a solar photovoltaic power plant to 1245 𝑔 𝐶𝑂2𝑒𝑞 ⁄𝑘𝑊ℎ for a coal powered thermoelectric power plant, the ratio of area occupied per installed power varies from 0.08 𝑚2⁄𝑘𝑊 for a natural gas powered thermoelectric power plant to 86 𝑚2⁄𝑘𝑊 for a hydroelectric power plant with reservoir, and the ratio of area occupied per electricity produced varies from 2 × 10−5 𝑚2⁄𝑘𝑊ℎ for a natural gas thermoelectric power plant to 5 × 10−2 𝑚2⁄𝑘𝑊ℎ for a hydroelectric power plant with reservoir.
Descrição
Tese de mestrado integrado em Engenharia da Energia e do Ambiente, 2021, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Gases com efeito de estufa Emissões diretas e indiretas Fase de construção e operação Mix de geração de energia elétrica Ciclo de vida Teses de mestrado - 2021