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

The aspiration for producing algal biofuel is motivated by the desire to replace conventional petroleum fuels, produce fuels domestically, and reduce greenhouse gas emissions. Although, in theory, algae have the potential to produce a large amount of petroleum fuel substitutes and capture carbon emissions, in practice, profitable algal biofuel production has proven quite challenging. This dissertation characterizes the production pathways for producing petroleum fuel substitutes from algae and evaluates constraints on algal biofuel production. Chapter 8 provides a summary of the entire dissertation. The first chapter provides a framework for reporting the production of renewable diesel from algae in a consistent way by using data that are specific and by presenting information with relevant metrics. The second chapter presents a review of analytical tools (i.e., microscopy, spectroscopy, and chromatography) that can be used to analyze the structure and composition of intermediate products in an algal biofuel production pathway. In chapters 3 through 6, the energy return on investment, water intensity, and financial return on investment are presented for three cases: 1) an Experimental Case in which data were measured during five batches of algal biocrude production with a combined processed volume of about 7600 L, 2) a hypothetical Reduced Case that assumes the same energy output as the Experimental Case, with reduced energy and material inputs, and 3) a Highly Productive Case that assumes higher energy outputs than the Experimental Case, with reduced energy and material inputs, similar to the Reduced Case. For all three cases, the second-order energy return on investment was determined to be significantly less than 1, which means that all three cases are energy negative. The water intensity (consumption and withdrawal) for all cases was determined to be much greater than that of conventional petroleum fuels and biofuels produced from non-irrigated crops. The financial return on investment was also found to be significantly less than 1 for all cases, indicating production would be unprofitable. Additionally, it was determined that large-scale algal biofuel production would be constrained by the availability of critical energy and material inputs (e.g., nitrogen and carbon dioxide). The final part of this dissertation presents a first-principles thermodynamic analysis that represents an initial attempt at characterizing the thermodynamic limits for algal biofuel production. In that analysis, the energy, entropy, and exergy is calculated for each intermediate product in the algal biofuel production pathway considered here. Based on the results presented in this body of work, game-changing technology and biotechnology developments are needed for sustainable and profitable algal biofuel production. / text

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.

Abstract Most of the steel produced in the world is based on the integrated blast furnace-converter route, which is based on the use of virgin raw materials. Large amounts of fossil-based, carbon containing reductants are used in blast furnaces, which results in carbon dioxide emissions into the atmosphere. Fossil carbon dioxide emissions from steel production can be reduced by new technologies or moving from non-renewable to renewable energy sources. Biomass-based reductants could be one way to reduce the specific emissions from blast furnace-based steel production. The aim of this thesis was to examine the techno-economic and CO₂ mitigation potentials of using bioreducers in blast furnace ironmaking. Bioreducer feasibility was analyzed in the Finnish context, but the research methods used can be applied more widely. The metallurgical properties of bioreducers were evaluated and compared to fossil-based reductants. The impact of bioreducers on blast furnace behavior and on other steel plant processes was evaluated, with an emphasis on the reductions achieved in CO₂ emissions at the plant scale. The CO₂ emissions, energy consumption and production costs of bioreducers were evaluated, as was the availability of energy wood for bioreducer production. The results show that solid, liquid and gaseous bioreducers can be produced with thermochemical conversion technologies. However, their suitability for blast furnace use varies greatly. The highest substitution of fossil-based reductants in a blast furnace is achieved with charcoal injection. The carbon footprint of torrefied wood, charcoal and Bio-SNG is moderate compared to fossil-based reducing agents and their production is energetically feasible. The economic feasibility of bioreducers is currently weak in comparison to fossil-based reducing agents, but competitive when compared to other CO₂ emission reduction measures such as carbon capture and storage. The biomass availability assessment revealed that sufficient amount of energy wood could be available for bioreducer production in the areas where Finnish steel plants are situated. The feasibility of bioreducer production could be improved by producing a number of products from the biomass and taking advantage of the process of integration possibilities. / Tiivistelmä Suurin osa maailmassa tuotetusta teräksestä valmistetaan integroidulla masuuni-konvertteri reitillä, joka perustuu neitseellisten raaka-aineiden käyttöön. Masuuniprosessissa käytetään suuri määrä fossiilisia, lähinnä hiilipohjaisia pelkistimiä, jotka aiheuttavat hiilidioksidipäästöjä ilmakehään. Fossiilisia hiilidioksidipäästöjä voidaan teräksenvalmistuksessa vähentää uusilla teknologioilla tai siirtymällä uusiutumattomista energialähteistä uusiutuviin. Biomassasta valmistetut pelkistimet voisivat olla yksi mahdollinen keino alentaa masuunipohjaisen teräksenvalmistuksen ominaispäästöjä. Tämän työn tavoitteena oli tarkastella biopelkistimien käytön teknistaloudellista potentiaalia masuunikäytössä ja aikaansaatavia hiilidioksidipäästövähenemiä eri systeemirajauksilla. Työssä keskityttiin tarkastelemaan biopelkistimien hyödynnettävyyttä lähinnä Suomen tasolla, vaikka käytetyt tutkimusmetodit ovat sovellettavissa myös laajemmin. Työssä arvioitiin biopelkistimien metallurgisia ominaisuuksia, niiden vaikutusta masuuniprosessiin ja laajemmin muihin terästehtaan prosesseihin, pääpainon ollessa saavutettavan CO₂ päästövähenemän tarkastelussa. Työssä tarkasteltiin biopelkistimien valmistuksen CO₂ päästöjä, energiankulutusta ja tuotantokustannuksia sekä energiapuun saatavuutta biopelkistimien tuotantoon. Tulokset osoittavat, että biomassasta voidaan valmistaa kiinteitä, nestemäisiä ja kaasumaisia pelkistimiä termokemiallisilla konversioteknologioilla, joiden soveltuvuus masuunikäyttöön vaihtelee suuresti. Masuuniprosessissa suurin fossiilisten pelkistimien korvaavuus saavutetaan käyttämällä puuhiili-injektiota. Torrefioidun puun, puuhiilen ja Bio-SNG:n hiilijalanjälki on varsin maltillinen verrattuna fossiilisiin pelkistimiin ja niiden tuotanto on energeettisesti järkevää. Biopelkistimien taloudellinen kannattavuus verrattuna fossiilisiin pelkistimiin on tällä hetkellä heikko, mutta kilpailukykyinen verrattuna muihin CO₂ päästöjen vähennyskeinoihin, kuten hiilidioksidin talteenottoon ja -varastointiin. Energiapuun saatavuus biopelkistimien valmistukseen on suurin alueilla, jotka sijaitsevat lähellä Suomen terästehtaita. Biopelkistimien tuotannon kannattavuutta voitaisiin parantaa tuottamalla useita tuotteita ja hyödyntämällä prosessi-integraatiota.

根據歐盟2009 年發布之再生能源指令，定義熱泵系統所擷取之大氣熱能、水熱能以及地熱能為再生能源之選項，熱泵技術不受日夜與天候影響，且具安全、有低耗能、低排碳的優點，可應用在空調、暖氣、熱水等設備，備受歐美日本等先進國家重視，也是歐美各國政府極力推廣的項目之一。本研究針對台灣地區家戶住宅所使用小型空氣源熱泵熱水機組，透過環境資源及能源效率的角度，來探討熱泵熱水系統對於台灣住宅部門的適用性。 在研究方法上，針對國內熱泵個案廠商進行系統盤查分析，並且估算使用運轉過程中所需之能源投入，以計算熱水系統在製造過程與運轉使用過程中之環境影響。選擇生命週期評估軟體SimaPro 7.3做為評估工具，使用Eco-Indicator 95、EPS 2000兩種衝擊評估模式，來以生命週期評估探討熱泵熱水系統對環境之影響。並輔以淨能源分析法中能源投資報酬率與能源回收期，以及估算熱泵熱水系統生命週期CO2排放量，來衡量熱泵熱水系統之能源效率是否具有其效益。並進一步針對不同的再生能源發電比例與提升熱泵能源效率比例，探討不同方案的敏感度分析。 根據本研究分析結果顯示，熱泵熱水系統不管從Eco-indicator 95或EPS 2000衝擊評估模式下，運轉使用階段對環境衝擊較大，主要的衝擊項目為重金屬汙染，是因為熱泵熱水系統運轉所使用的電力消耗所致。使用熱泵熱水系統對環境衝擊程度遠較電熱水系統來得小，雖在Eco-indicator 95之衝擊評估模式下，瓦斯熱水系統較熱泵熱水系統環境衝擊程度較小，但以EPS 2000衝擊評估模式下，熱泵熱水系統對環境是最為友善的熱水系統。以淨效益估算熱泵熱水系統源投資報酬（EROI）值為1.45～5.55，能源回收期約為0.22年至2.16年，表示熱泵熱水系統從生命週期的角度來檢視能源效率是具有效益的。由於目前熱泵熱水系統對環境最大的負擔來源是電力的使用，若未來能提高再生能源發電比例、降低臺灣電能含碳濃度，或者提高熱泵能源生產效率，均能降低熱泵熱水系統對環境的負面影響。 / The purpose of this study is to apply life cycle assessment (LCA) and net energy analysis to explore the environmental impacts of the heat pump water heater in Taiwan. In order to achieve this objective, domestic data inventory was gathered from local heat pump industry in Taiwan through questionnaires including input of energy, product output and waste, etc. The SimaPro7.3 program and two impact assessment methods including Eco-Indicator 95, EPS 2000 were utilized to evaluate the environmental impact of the heat pump water heater. Also, we used net energy analysis such as energy return on investment and energy payback time, and estimated the life-cycle CO2 emissions to see whether if the heat pump water heater has its energy efficiency. In addition, the sensitivity analysis was performed by varying renewable energy generation portfolio and the heat pump energy efficiency ratio. Emprical results of two impact assessment methods (Eco-indicator 95 and EPS 2000) show that the main impact on environment of heat pump water heater is from operation phase. When operating the heat pump water heater, it needs to consume electricity which is generated from fossil fuel and caused the environmental impact. Compared with the electric water heater, the environmental impact degree of heat pump water heater is much smaller. In Eco-indicator 95 method, gas water heater has less influence on the environment than heat pump water heater; however, heat pump water heater is the most environment-friendly system in EPS 2000 method. That is because gas is a kind of nonrenewable resource. From the viewpoint of resource stock, gas indeed influence “Depletion of reserves” of environmental impact. By utilizing net energy analysis, the estimated energy return on investment (EROI) of heat pump water heater is 1.45～5.55, and energy payback time is 0.22~2.16 years. It indicates that heat pump water heater has significant benefit from life-cycle perspective. The main impact to environment by heat pump water heater is essentially derived from electricity input. To mitigation this environmental issue, one can reduce environmental impact by increase the proportion of renewable energy generation, and reducing the electricity CO2 emission. Furthermore, improving the energy efficiency of the heat pump would also helpful.