Installed photovoltaic nameplate power have been growing rapidly around the worldin the last few years. But how much energy is returned to society (i.e. net energy) by this technology, and which factors contribute the most to the amount of energy returned? The objective of this thesis was to examine the importance of certain inputs and outputs along the solar panel production chain and their effect on the energy return on (energy) investment (EROI) for crystalline wafer-based photovoltaics. A process-chain model was built using publicly available life-cycle inventory (LCI) datasets. This model has been kept simple in order to ensure transparency. Univariate sensitivity analysis for processes and multivariate case studies was then applied to the model. The results show that photovoltaic EROI values are very sensitive to assumptions regarding location and efficiency. The ability of solar panels to deliver net energy in northern regions of the earth is questionable. Solar cell wafer thickness have a large impact on EROI, with thinner wafers requiring less silicon material. Finding an alternative route for production of solar-grade silicon is also found to be of great importance, as is introduction of kerf loss recycling. Equal system sizes have been found to yield an primary EROI between approximately 5.5-19 depending on location and assumptions. This indicates that a generalized absolute EROI for photovoltaics may be of little use for decision-makers. Using the net energy cliff concept in relation to primary EROI found in this thesis shows that primary EROI rarely decreases to less than the threshold of 8:1 in univariate cases. Crystalline photovoltaics under similar system boundaries as those in the thesis model does not necessarily constrain economic growth on an energetic basis.

Durante as últimas três décadas, o segmento do gás natural vem mostrando avanço expressivo dado a participação na matriz energética brasileira. Esse crescimento se deve a importância da sua oferta, e um potencial de menor impacto ambiental em comparação com outros ativos energéticos de origem fóssil. Devido as essas características o Gás Natural tornou-se uma da fonte de energia mais usada. A despeito dos benefícios técnicos e econômicos o gás natural passou a ser também uma fonte estratégica de energia, principalmente em razão dos menores impactos ambientais que proporciona em comparação ao petróleo e seus derivados. Diante desse quadro o Brasil vem ampliando e disponibilizando, desse recurso em função da descoberta de novos campos em São Paulo e no litoral do Nordeste. No entanto, o mesmo não pode ser dito em relação à infraestrutura de transporte dutoviária, a malha atual de distribuição de gás refinado do país deixa de atender a uma parcela significativa da população residente nas regiões Norte, Centro-Oeste e mesmo, de municípios do interior de estados importantes do Nordeste e do Sudeste. Sendo assim, procurou-se determinar quais os benefícios e ônus, em termos de impactos ambientais acarretados pela situação atual de oferta de Gás Natural e também avaliar para a condição de suprimento futuro para este insumo. Para tal, decidiu-se adotar a Avaliação do Ciclo de Vida (ACV), que trata-se de uma ferramenta de gestão ambiental usada para avaliar impactos ambientais, associados a produtos, processos e serviços. Sua principal característica é de avaliar de forma sistêmica, levando em conta todas as etapas do seu ciclo de vida. O objetivo deste trabalho foi avaliar a contribuição ambiental para o planejamento da oferta futura de gás natural no Brasil, segundo a abordagem de ciclo de vida. Para a análise ambiental, aplicou-se o método de Avaliação de Impacto do Ciclo de Vida (AICV), Recipe midpoint e, para análise energética o método Demanda Primária de Energia foi utilizado, seguido pelo cálculo do Índice de Retorno Energético sobre o investimento (EROI). Os resultados em termos de perfil ambiental indicaram que os processos que mais contribuíram para as emissões de Gases de Efeito Estufa são os de extração e processamento do gás bruto nas Unidades de Processamento de Gás (UPGNs). As principais contribuições para Mudanças Climáticas são emissões CH4, que ocorrem durante o transporte do gás bruto ou acabado. Para a região Sul e Centro-Oeste, observou-se a influência de perdas de CO2, que ocorrem nas estações de compressão que deslocam o gás desde a Bolívia até as regiões Sul e Centro-Oeste do país. Em termos de Demanda Primária de Energia (PED) os resultados apontam uma concentração de consumos na forma de NRF. Pode-se observar que as perdas de CH4 com maior representatividade ocorre em sua grande maioria na extração do insumo durante a retirada do recurso fóssil das reservas. Para condição de suprimento futuro, a análise mostrou que para PED, a distância de transporte é um fator decisivo de impacto, suplantando inclusive o volume de gás processado a ser distribuído. Já no tocante a Mudanças Climáticas (CC), esses dois parâmetros serão decisivos, sendo que o maior peso para efeito de geração de impacto recairia sobre a quantidade de gás distribuído. / During the last three decades, the natural gas field has shown considerable progress as its participation in the Brazilian energy matrix. This growth is related to the supply and demand as well as the potential of lower environmental impact compared to other fossil fuels. Therefore, considering these characteristics, the Natural Gas became one of the main sources of energy. Beside the technical and economic benefits of the natural gas, it has also become a strategic source of energy, mainly due to the smaller impacts that are provided when compared to Oil and its derivatives. In view of this situation, Brazil has expanded and making available this resource due to the discovery of new reserves in São Paulo and the Northeast Coast. However, the scenario of the pipeline transport infrastructure is different. The country\'s current refined gas distribution network is not serving a significant portion of the residential population in the North, Midwest and even important counties in the countryside of the Northeast and Southeast.Therefore, it was sought to determine, for the current situation, the benefits and the overall environmental impact of the Natural Gas supply and to evaluate the future condition for this input. For this, it was decided to adopt the Cycle Assessment of Life (ACV) which is an environmental management tool used to evaluate environmental impacts associated with products, processes and services. Its main characteristic is to evaluate in a systemic way, taking into account all stages of its life cycle. The goal of this work was to evaluate the environmental contribution to the planning of the future supply of the natural gas in Brazil, according to the life cycle approach. For the environmental analysis, it was used the Life Cycle Impact Assessment (AICV), Recipe midpoint and, for energy analysis, the Primary Energy Demand method was used, followed by the calculation of the Energy Return on Investment Index (EROI). The results in terms of the environmental profile indicated that the processes that most contributed to the GHG emissions are the extraction and processing of the raw gas in the Gas Processing Units (UPGNs). The main contributions to Climate Change are CH4 emissions, which occur during the transportation of the raw or finished gas. For the South and Center-West, it was observed the influence of CO2 losses, which occur in the compression stations that move the gas from Bolivia to the South and Center-West areas of the country. In terms of PED, the results indicate a concentration of consumptions as NRF. It can be observed that the most of the losses of CH4, with great relevance, occur in the extraction of the input during the withdrawal of the fossil resource from the reserves. For the future supply condition the analysis showed that, for PED, the transport distance is a decisive factor, even supplanting the volume of refined gas to be distributed for the impact profile. Regarding CC, these two parameters will be important, and the greatest impact weight will be on the amount of gas distributed.

No description available.

This thesis examines the energy return on investment (EROI) of a model 3 MW hybrid gas-geothermal plant on the Texas Gulf Coast. The model plant uses a design similar to the DOE Pleasant Bayou No. 2 test geothermal plant, and uses a gas engine to harness entrained methane and an Organic Rankine Cycle turbine to harness thermal energy from hot brines. The indirect energy cost was calculated using the Carnegie Mellon University Economic Input-Output Life Environmental Life Cycle Analysis (EIO-LCA) model. The EROI of the plant using the 1997 EIO-LCA energy data is 12.40, and the EROI of the plant using 2002 EIO-LCA energy data is 14.18. Sensitivity analysis was run to determine how the plant parameters affect the EROI. A literature review of the EROI of different power sources shows that the EROI of the hybrid geothermal plant is greater than the EROI of flash steam geothermal and solar, but is lower than the EROI of dry steam geothermal, wind power, nuclear, coal, gas, and hydroelectric plants. An analysis of the EROI to financial return on investment (FROI) shows that the FROI for a hybrid geothermal plant could be competitive with wind and solar as a viable renewable resource in the Texas electricity market. / text

Large-scale deployment of low-carbon energy technologies is important for counteracting anthropogenic climate change and achieving universal energy access. This thesis explores potential growth rates of technologies necessary to reach a more sustainable global energy system, the material and energy flows required to commission these technologies, and potential future availability of the required resources. These issues are investigated in five papers. Potential future growth rates of wind energy and solar photovoltaics, and the associated material requirements are explored, taking the expected service life of these technologies into account. Methodology for assessing net energy return and natural resource use for wind energy systems are analyzed. Potential future availability of lithium and phosphate rock are also investigated. Estimates of energy and materials required for technologies such as wind energy and photovoltaics vary, and depend on the assumptions made and methods used. Still, it is clear that commissioning of low-carbon technologies on the scale required to reach and sustain a low-carbon energy system in coming decades requires significant quantities of both bulk materials and scarcer resources. For some technologies, such as thin film solar cells and electric vehicles with lithium-ion batteries, availability of materials could become an issue for potential growth rates. Future phosphate rock production could become highly dependent on few countries, and potential political, social and environmental aspects of this should be investigated in more detail. Material and energy flows should be considered when analyzing growth rates of low-carbon technologies. Their estimated service life can indicate sustainable growth rates of technologies, as well as when materials are available for end-of-life recycling. Resource constrained growth curve models can be used to explore future production of natural resources. A higher disaggregation of these models can enable more detailed analysis of potential constraints. This thesis contributes to the discussion on how to create a more sustainable global energy system, but the methods to assess current and future energy and material flows, and availability of natural resources, should be further developed in the future.

The aim of this thesis is to evaluate ORC systems and technologies from an energy and economic perspective. ORC systems are a growing renewable electricity generation technology, but New Zealand has limited local skills and expertise for identifying ORC resource opportunities and subsequently developing suitable technologies at low cost. For this reason, this thesis researches ORC technology, resource types, and international development, with the aim to determine guidelines for how to cost-effectively develop ORC systems, and to make recommendations applicable to furthering their development within a New Zealand context. This thesis first uses two surveys, one of commercial ORC installations, and a second of economic evaluations of ORC systems in literature, to determine what resources and economic scenarios are supportive of commercial development. It is found that geothermal resources provide the largest share of ORC capacity, with biomass and waste-heat recovery (WHR) being developed more recently. The surveys also found that countries with high electricity prices or policy interventions have developed a wider range of resources using ORC systems. This thesis then undertakes an EROI evaluation of ORC electricity generation systems using a combination of top-down and process based methodologies. Various heat sources; geothermal, biomass, solar, and waste heat are evaluated in order to determine how the utilised resource can affect energy profitability. A wide range of EROIstnd values, from 3.4 – 22.7 are found, with solar resources offering the lowest EROIs, and geothermal systems the highest. Higher still EROI values are found to be obtainable with longer system lifetimes, especially for WHR systems. Specific engineering aspects of ORC design and technology such as high-side pressure, heat storage, modularity, superheating, pinch-point temperature difference, and turbine efficiency are evaluated in terms of economic performance, and a variety of general conclusions are made about each. It is found that total system thermo-economic optimisation may not lead to the highest possible EROI, depending on the objective function. Lastly, the effects of past and potential future changes to the markets and economies surrounding ORCs are explored, including the New Zealand electricity spot price, steel and aluminium prices, subsidies, and climate policy. Of the subsidy types explored, it is found that directly subsidising ORC system capital has the greatest effect on the economic performance of ORC systems, as measured by common metrics. In conclusion, this thesis finds that ORC systems have a limited applicability to New Zealand’s electricity market under current economic conditions outside of geothermal and off-grid generation, but changes to these conditions could potentially make their development more viable. The author recommends that favourable resources should be developed using systems that provide high efficiencies, beyond what might provide the best economic performance, in order to increase EROI, and reduce the future need for costly investments into increasingly less favourable resources.

The aim of this thesis is to evaluate ORC systems and technologies from an energy and economic perspective. ORC systems are a growing renewable electricity generation technology, but New Zealand has limited local skills and expertise for identifying ORC resource opportunities and subsequently developing suitable technologies at low cost. For this reason, this thesis researches ORC technology, resource types, and international development, with the aim to determine guidelines for how to cost-effectively develop ORC systems, and to make recommendations applicable to furthering their development within a New Zealand context. This thesis first uses two surveys, one of commercial ORC installations, and a second of economic evaluations of ORC systems in literature, to determine what resources and economic scenarios are supportive of commercial development. It is found that geothermal resources provide the largest share of ORC capacity, with biomass and waste-heat recovery (WHR) being developed more recently. The surveys also found that countries with high electricity prices or policy interventions have developed a wider range of resources using ORC systems. This thesis then undertakes an EROI evaluation of ORC electricity generation systems using a combination of top-down and process based methodologies. Various heat sources; geothermal, biomass, solar, and waste heat are evaluated in order to determine how the utilised resource can affect energy profitability. A wide range of EROIstnd values, from 3.4 – 22.7 are found, with solar resources offering the lowest EROIs, and geothermal systems the highest. Higher still EROI values are found to be obtainable with longer system lifetimes, especially for WHR systems. Specific engineering aspects of ORC design and technology such as high-side pressure, heat storage, modularity, superheating, pinch-point temperature difference, and turbine efficiency are evaluated in terms of economic performance, and a variety of general conclusions are made about each. It is found that total system thermo-economic optimisation may not lead to the highest possible EROI, depending on the objective function. Lastly, the effects of past and potential future changes to the markets and economies surrounding ORCs are explored, including the New Zealand electricity spot price, steel and aluminium prices, subsidies, and climate policy. Of the subsidy types explored, it is found that directly subsidising ORC system capital has the greatest effect on the economic performance of ORC systems, as measured by common metrics. In conclusion, this thesis finds that ORC systems have a limited applicability to New Zealand’s electricity market under current economic conditions outside of geothermal and off-grid generation, but changes to these conditions could potentially make their development more viable. The author recommends that favourable resources should be developed using systems that provide high efficiencies, beyond what might provide the best economic performance, in order to increase EROI, and reduce the future need for costly investments into increasingly less favourable resources.

Brown macroalgae or brown seaweed is a promising source of ethanol that may avoid the challenges of arable land use, water use, lignin content, and the food vs. fuel debate associated with first generation and cellulosic ethanol sources; however, this promise is challenged by seaweed’s high water content, high ash content, and natural composition fluctuations. Notably, lifecycle studies of seaweed ethanol are lacking in the literature. To address this gap, a well-to-wheel model of ethanol production from farmed brown seaweed was constructed and applied to the case of Saccharina latissima farming in British Columbia (BC), Canada, to determine energy return on energy invested (EROI), carbon intensity (CI), and near shore seaweed farming production potential for seaweed ethanol and to examine the production cost of seaweed ethanol. Seaweed farming and ethanol production were modeled based on current BC farming methods and the dry grind corn ethanol production process; animal feed was included as an ethanol co-product, and co-product credits were considered. A seaweed ethanol yield calculation tool that accounts for seaweed composition was proposed, and a sensitivity study was done to examine case study data assumptions. In the case study, seaweed ethanol had lower CI than sugarcane, wheat, and corn ethanol at 10.1 gCO2e/MJ, and it had an EROI comparable to corn ethanol at 1.78. Seaweed ethanol was potentially profitable due to significant revenue from animal feed sales; however, the market for seaweed animal feed was limited by the feed’s high sodium content. Near shore seaweed farming could meet the current demand for ethanol in BC, but world near shore ethanol potential is likely an order of magnitude lower than world ethanol production and two orders of magnitude lower than world gasoline production. Composition variation and a limited harvest season make solar thermal or geothermal seaweed drying and storage necessary for ethanol production in BC. Varying seaweed composition, solar thermal drying performance, co-product credits, the type of animal feed produced, transport distances, and seaweed farming performance in the sensitivity study gave an EROI of over 200 and a CI of -42 gCO2e/MJ in the best case and an EROI of 0.64 and CI of 33 gCO2e/MJ in the worst case. Co-product credits and the type of animal feed produced had the most significant effect overall, and the worst cases of seaweed composition and solar thermal seaweed drying system performance resulted in EROI of 0.64 and 1.0 respectively. Brown seaweed is concluded to be a potentially profitable source of ethanol with climate benefits that surpass current ethanol sources; however, additional research into seaweed animal feed value, co-product credits, large scale seaweed conversion, and the feasibility of solar thermal or geothermal seaweed drying is required to confirm this conclusion. / Graduate

No description available.

Questa tesi di dottorato analizza l’utilizzo del sorgo (Sorghum bicolour (L.) Moench) al fine di produrre energia elettrica, tramite combustione diretta della biomassa. Il focus della tesi è stato quello di sottolineare i benefici ed i rischi associati all’uso di tre genotipi di sorgo caratterizzati da diversa lunghezza del ciclo culturale (precoce, medio-tardivo e tardivo). La dinamica e la durata del processo di essicazione in campo sono state simulate attraverso un modello ad hoc (“sorghum haying model”), il quale integrato a CropSyst, è stato utilizzato per realizzare un’analisi del rischio produttivo stimando le perdite di biomassa (respirazione e meccanizzazione), ed i mancati affienamenti. Nell’analisi del rischio vengono stimati il numero di ettari necessari e la probabilità di eccedere la soglia di 64.000 ton ss anno-1 necessari per l’alimentazione di una centrale nell’Oltrepò pavese . Inoltre uno studio di Life Cycle Assessment è stato condotto per la valutazione dell’impatto ambientale dell’utilizzo del sorgo integrato a quello della paglia per il completamento del fabbisogno totale della centrale 94.000 ton ss anno-1. Particolare attenzione inoltre è stata data alla variazione del contenuto di C organico del suolo dovuto alla rimozione della paglia ed all’interramento dei mancati affienamenti di sorgo. Il genotipo precoce mostra le migliori performance produttive ed energetiche oltre che la più alta probabilità di eccedere la soglia di 64.000 ton ss anno-1. Lo studio di LCA non ha mostrato differenze significative tra i genotipi anche se il minor impatto ambientale, è stato evidenziato dal genotipo tardivo conseguenza dell’interramento della più alta quantità di mancati affienamenti. / This PhD thesis explores the use of sorghum (Sorghum bicolour (L.) Moench) as a dedicated bio-energy crop and highlights the benefits and risks associated with the use of early, medium-late and late sorghum genotypes to generate electricity by direct combustion in a biomass power plant. The dynamics and duration of the field drying process were simulated through the development of a specific model ("sorghum haying model"), which integrated with CropSyst, was used to perform a production risk assessment analysis estimating the biomass losses (respiration and mechanical), the haymaking failures and consequently to quantify the amount of dry baled biomass available for the power plant. In addition, the number of hectares needed to plant sorghum and the probability to exceed the threshold of 64000 Mg DM y-1, necessary to feed a biomass power plant in Oltrepò Pavese, were estimated. A complete Life Cycle Assessment (LCA) study was carried out in order to evaluate the environmental impact of the three sorghum genotypes involved in this study. The LCA study takes into consideration the use of winter wheat straw as an additional biomass source to satisfy the total biomass power plant needs (94000 Mg DM y-1). Particular attention was given to the soil organic C change (ΔSOC) due to straw removal and haymaking failures soil incorporation. Early genotype showed the best biomass production and energy performance as well as the highest probability to exceed the threshold of 64000 Mg DM y-1. The LCA results did not show significant differences between genotypes although the lower environmental impact, has been achieved by the late genotype due to the highest amount of haymaking failures incorporated in the soil.