The nuclear industry lacks a well documented, systematic procedure defining the requirements for power plant cycle selection and optimisation. A generic technoeconomic optimisation methodology is therefore proposed that can serve in the selection of balance-of-plant configurations and design conditions for High Temperature Gas-cooled Reactor (HTGR) power plants. The example of a cogeneration steam plant coupled to a pebble bed reactor, with or without an intermediate buffer circuit, was used in search of a suitable methodology. The following analyses were performed: • First order thermal hydraulic analysis • Second order thermal hydraulic analysis including cost estimation • Third order steady state analysis to evaluate part-load operation • Third order transient analysis to test operability and controllability The assumptions, level of detail required, modelling methodology and the type of decisions that can be made after each stage are discussed. The cycles under consideration are evaluated and compared based on cycle efficiency, capital cost, unit energy cost and operability. The outcome of this study shows that it is worthwhile spending the effort of developing a second order costing model and a third order model capable of analysing off-design conditions. First order modelling could be omitted from the methodology. The advantage of a second order model is that the cycle configuration can be optimised from a unit energy cost perspective, which incorporates the effects of both capital cost and cycle efficiency. The optimum cycle configuration differs from that predicted by first order modelling, which illustrates that first order modelling alone is insufficient. Third order part-load operation analysis showed operability issues that were not apparent after first or second order modelling. However, transient analysis does not appear justified in the very early design stages. To conclude, the proposed methodology is summarised as follows: • Evaluate the user requirements and design constraints. • Apply design principles from the Second Law of thermodynamics in selecting cycle configurations and base case operating conditions. • Optimise the operating conditions by performing second order thermal hydraulic modelling which includes component design and cost estimation. • Evaluate part-load operation with third order analysis. • Select the cycle with the lowest Levelised Unit Energy Cost (LUEC) and simplest operating strategy. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.

The nuclear industry lacks a well documented, systematic procedure defining the requirements for power plant cycle selection and optimisation. A generic technoeconomic optimisation methodology is therefore proposed that can serve in the selection of balance-of-plant configurations and design conditions for High Temperature Gas-cooled Reactor (HTGR) power plants. The example of a cogeneration steam plant coupled to a pebble bed reactor, with or without an intermediate buffer circuit, was used in search of a suitable methodology. The following analyses were performed: • First order thermal hydraulic analysis • Second order thermal hydraulic analysis including cost estimation • Third order steady state analysis to evaluate part-load operation • Third order transient analysis to test operability and controllability The assumptions, level of detail required, modelling methodology and the type of decisions that can be made after each stage are discussed. The cycles under consideration are evaluated and compared based on cycle efficiency, capital cost, unit energy cost and operability. The outcome of this study shows that it is worthwhile spending the effort of developing a second order costing model and a third order model capable of analysing off-design conditions. First order modelling could be omitted from the methodology. The advantage of a second order model is that the cycle configuration can be optimised from a unit energy cost perspective, which incorporates the effects of both capital cost and cycle efficiency. The optimum cycle configuration differs from that predicted by first order modelling, which illustrates that first order modelling alone is insufficient. Third order part-load operation analysis showed operability issues that were not apparent after first or second order modelling. However, transient analysis does not appear justified in the very early design stages. To conclude, the proposed methodology is summarised as follows: • Evaluate the user requirements and design constraints. • Apply design principles from the Second Law of thermodynamics in selecting cycle configurations and base case operating conditions. • Optimise the operating conditions by performing second order thermal hydraulic modelling which includes component design and cost estimation. • Evaluate part-load operation with third order analysis. • Select the cycle with the lowest Levelised Unit Energy Cost (LUEC) and simplest operating strategy. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2010.

Global pressure to reduce greenhouse gas (GHG) emissions, energy security concerns and increasing demand for liquid fuels incentivize the search for more sustainable and secure alternative methods for producing liquid fuels with improved efficiency and reduced environmental impacts. One of the economically attractive examples of these alternate methods is the gas-to-liquid process, however, its environmental impacts are worse than traditional petroleum refining. Carbon capture and sequestration is an option to reduce greenhouse gas emissions of processes, but it decreases the efficiency of the process and often results in economic infeasibility. Instead, integrating different processes and feedstocks was demonstrated to improve the efficiency, economic and environmental performance of the processes. The focus of this thesis is to design and simulate a novel integrated biomass, gas, nuclear to liquids (BGNTL) process with negative greenhouse gas emissions. In this process, nuclear heat from a high temperature gas-cooled reactor (HTGR) is used as the heat source for a steam methane reforming (SMR) process. The integrated HTGR and SMR process requires detailed analysis and modeling to address key challenges on safety, operability, economic and environmental impacts of the integrated process. To this end, a rigorous first principle based mathematical model was developed in gPROMS modeling environment for the integrated HTGR/SMR process. The results for a large scale design of this system indicate that hydrogen rich syngas with H2/CO ratio in the range of 6.3 can be achieved. To meet the desired H2/CO ratio (around 2) required for the downstream fuel synthesis processes, the HTGR/SMR derived syngas can be blended with a hydrogen lean syngas from biomass gasification. In this thesis, the large scale design of the BGNTL process to synthesize gasoline, diesel and dimethyl ether (DME) is investigated. The results from the gPROMS model of the integrated HTGR/SMR system are used for simulating the BGNTL process in Aspen Plus. The performance of the BGNTL process was compared with a biomass, gas to liquids (BGTL) process. The efficiency, economics, and environmental impact analyses show that the BGNTL process to produce DME is the most efficient, economic and environmentally friendly process among all the considered designs. The results demonstrate that process integration exploits certain synergies that leads to significantly higher carbon and energy efficiencies and lower greenhouse gas emissions. In addition, it was found that all the studied designs yield a net negative greenhouse gas emissions when carbon capture and storage technology is implemented. As another sustainable alternative to meet the required H2/CO ratio of the syngas when biomass resources are not available, it is proposed to apply the nuclear heat to the mixed reforming of methane. This represents using steam and waste CO2 to reform methane into valuable syngas. The developed model for the integrated HTGR/SMR system is extended to the mixed reforming of methane (MRM) process and it was demonstrated that integrated HTGR/MRM process can be a promising option to achieve certain desired H2/CO ratios for the downstream energy conversion processes. / Thesis / Doctor of Philosophy (PhD)

Biomass conversion into forms of energy is receiving current attention because of environmental, energy and agricultural concerns. The purpose of this thesis is to analyze the environmental, energy, economic, and technological aspects of using a form of biomass, switchgrass (panicum virgatum), as a partial or complete replacement for coal in power generation and cogeneration systems. To examine the effects of such a substitution, an environmental biocomplexity approach is used, wherein the agricultural, technological, economic, and environmental factors are addressed. In particular, lifecycle analysis (LCA) and a three-dimensional integrated economic, energy and environmental analysis is employed. The effectiveness of alternate technologies for switchgrass preparation, harvest and use in terms of greenhouse gas impact, cost and environmental implications is examined. Also, different scenarios of cofiring and biomass preparation pathways are investigated. Optimization of the total biomass power generation cost with minimum greenhouse gas effect is undertaken using mathematical programming for various alternate competitive biomass processing pathways. As a byproduct of this work a generic tool to optimize the cost and greenhouse gas emissions for allocation of fuel sources to the power generating sinks is developed. Further, this work discusses the sensitivity of the findings to varied cofiring ratios, coal prices, hauling distances, per acre yields, etc. Besides electricity generation in power plants, another viable alternative for reducing greenhouse gases (GHGs) is the utilization of biomass in conjunction with combined heat and power (CHP) in the process industries. This work addresses the utilization of biowaste or biomass source in a processing facility for CHP. A systematic algebraic procedure for targeting cogeneration potential ahead of detailed power generation network design is presented. The approach presented here effectively utilizes the biomass and biowaste sources as external fuel, and matches it with the use and dispatch of fuel sources within the process, heating and non-heating steam demands, and power generation. The concept of extractable energy coupled with flow balance via cascade diagram has been used as a basis to construct this approach. The work also discusses important economic factors and environmental policies required for the cost-effective utilization of biomass for electricity generation and CHP.

Biomass conversion into forms of energy is receiving current attention because of environmental, energy and agricultural concerns. The purpose of this thesis is to analyze the environmental, energy, economic, and technological aspects of using a form of biomass, switchgrass (panicum virgatum), as a partial or complete replacement for coal in power generation and cogeneration systems. To examine the effects of such a substitution, an environmental biocomplexity approach is used, wherein the agricultural, technological, economic, and environmental factors are addressed. In particular, lifecycle analysis (LCA) and a three-dimensional integrated economic, energy and environmental analysis is employed. The effectiveness of alternate technologies for switchgrass preparation, harvest and use in terms of greenhouse gas impact, cost and environmental implications is examined. Also, different scenarios of cofiring and biomass preparation pathways are investigated. Optimization of the total biomass power generation cost with minimum greenhouse gas effect is undertaken using mathematical programming for various alternate competitive biomass processing pathways. As a byproduct of this work a generic tool to optimize the cost and greenhouse gas emissions for allocation of fuel sources to the power generating sinks is developed. Further, this work discusses the sensitivity of the findings to varied cofiring ratios, coal prices, hauling distances, per acre yields, etc. Besides electricity generation in power plants, another viable alternative for reducing greenhouse gases (GHGs) is the utilization of biomass in conjunction with combined heat and power (CHP) in the process industries. This work addresses the utilization of biowaste or biomass source in a processing facility for CHP. A systematic algebraic procedure for targeting cogeneration potential ahead of detailed power generation network design is presented. The approach presented here effectively utilizes the biomass and biowaste sources as external fuel, and matches it with the use and dispatch of fuel sources within the process, heating and non-heating steam demands, and power generation. The concept of extractable energy coupled with flow balance via cascade diagram has been used as a basis to construct this approach. The work also discusses important economic factors and environmental policies required for the cost-effective utilization of biomass for electricity generation and CHP.

Energy security is probably one of the most challenging issues around the world. Therefore, the focus on methods of decreasing energy consumption and consequently its associated greenhouse gas (GHG) emissions is intensified by policy decision makers. Residential buildings are one of the potential sectors that can reduce its energy consumption in various ways, such as: improving thermal characteristics of the building, using more energy efficient appliances and using renewable energy resources. Among these methods, integration of solar technologies to buildings provides one of the substantial opportunities for reducing energy consumption and the associated GHG emissions in Canada’s residential sector. Therefore, this research work was conducted to assess the impact of solar technologies and solar technology integration strategies on the end-use energy consumption and the associated greenhouse gas (GHG) emissions in Canadian residential sector by using a new state-of-the-art end-use energy and GHG emissions model of the Canadian residential housing stock. The new Canadian residential end-use energy and emissions model that is used in this project incorporates a 17,000 house database developed using the latest data available from the Energuide for Houses database, Statistics Canada housing surveys, and other available housing databases, and utilizes an advanced building energy simulation program as its simulation engine. A new neural network methodology is incorporated into the model to estimate the socio-economic and demographic dependencies of the energy consumption of discretionary end-uses such as appliances, lighting and domestic hot water, while a new approach is used to incorporate occupancy, appliance, lighting and domestic hot water load profiles into the model. A new method is used to calculate the GHG emissions from electricity consumption used in the residential sector based on the actual electrical generation fuel mix and the marginal fuel used in each province as a function of time of the year. Each solar technology is added to the eligible houses to examine the interrelated effects of integrated solar technologies and practices on the housing stock. The objective is to conduct realistic assessments of the cost effectiveness, energy savings and GHG emission reduction benefits of integrated solar technologies for the entire Canadian housing stock (CHS) as well as for different regions, house type, and fuel types. The integrated solar technologies and practices that are assessed include passive solar with added thermal storage and motorized blinds, solar DHW system, and photovoltaic electricity and heat generation systems. This project provides a comprehensive techno-economic and emissions assessment of integrated solar technologies and practices, and will be useful for developing national and regional policies and strategies related with integrating solar energy into the residential sector.

<p>Much of current interest in aviation biofuels centers on trying to curb emissions of carbon dioxide and other greenhouse gases (GHGs) [1]. The problem is that the alternative aviation fuels which have been developed so far are not economically viable without policy supports and are underwhelming in regards to their environmental sustainability. The objective of this research is to identify biofuel pathways that perform better economically and environmentally than those which have been developed thus far. This paper will pursue this objective by examining the economic performance of a CH pathway fed by field pennycress under a number of possible scenarios.</p> <p>We conduct a stochastic discounted cash flow techno-economic analysis (TEA) of a plant designed to use catalytic hydrothermolysis (CH) technology to produce renewable diesel fuel, renewable jet fuel, and renewable naphtha from pennycress seed oil on a “greenfield” site under sixteen different scenarios defined by plant location, stage of commercialization, choice of fuel product slate, and policy environment. We combine process parameters such as conversion efficiencies, heat and water requirements, and capital costs for our model plant with stochastic projections of key input and output prices in order to model the distribution of possible financial outcomes for the plant over a twenty-year productive life. Our work follows McGarvey and Tyner (2018) in many respects, but uses updated process parameters from Applied Research Associates, Inc. (ARA), connects with economic analyses of the potential pennycress oil supply chain, and includes novel approaches to modeling key policies (US Renewable Fuel Standard, California Low Carbon Fuel Standard, and US Biodiesel Blender Tax Credit) and price series (US No. 2 diesel fuel, soybean oil, and dried distiller’s grains with solubles) [2]. Our output metrics include distributions of Net Present Values (NPVs), Probabilities of Loss (POLs), and distributions of Breakeven Prices (BEPs) for key inputs and outputs.</p> <p>Our results show that aviation biofuels production at a greenfield CH plant fed by pennycress seed oil is not economic under current market and policy conditions. Our breakeven metrics for a renewable jet fuel policy incentive, crude oil prices, and the input cost of pennycress oil indicate this could change if one of the following were to occur: </p> <p>· A crude oil price increase of at least 31-52%</p> <p>· A jet fuel price increase of at least 11-26%</p> <p>· A pennycress oil price discount of 2-6% from soybean oil prices</p> <p>· Some combination of the above</p> <p>These findings are heavily influenced by current policy design.</p>

This work seeks to compare various Acetone-Butanol-Ethanol (ABE) fermentation extraction chemicals on an economic and environmental basis. The chemicals considered are: decane, a decane/oleyl alcohol blend, decanol, a decanol/oleyl alcohol blend, 2-ethyl-hexanol, hexanol, mesitylene, and oleyl alcohol. To facilitate comparison a pure-distillation base case was also considered. The aforementioned extractants are a mix of both toxic and non-toxic extractants. Non-toxic extractants can be used directly in fermentation reactors, improving overall fermentation yield by removal of toxic butanol. The extractants were modelled in Aspen Plus V8.8 and separation trains were designed to take advantage of extractant properties. The separation section of the plant was then integrated with upstream and downstream units to determine the Minimum Butanol Selling Prices (MBSP) for second generation extractive ABE fermentation. Upstream processes include biomass (switchgrass) solids processing, biomass pre-treatment/saccharification and fermentation while downstream processes include utility generation and wastewater treatment. The cost of CO2 equivalent emissions avoided (CCA) was used as a metric to compare environmental impact of each process as compared to gasoline. The economic best and environmental best extractant is shown to be 2-ethyl-hexanol with a MBSP of $1.58/L and a CCA of $471.57/tonne CO2 equivalent emissions avoided. Wastewater treatment, which is often ignored in other works, was found to makeup over 30% of total installed capital cost for all extractants. / Thesis / Master of Applied Science (MASc)

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Published Article / This study investigates the use of off-grid micro-hydrokinetic river system as a cost-effective and sustainable electricity supply option for remote rural residents in close proximity to flowing water and not having access to grid electricity. This hydrokinetic technology is still in the development stage and there is a lack of application especially in rural areas with reasonable water resource. This study will present the economic and environmental benefits of the proposed system. A mathematical model is developed to simulate the system performance as submitted to different solicitations. A test prototype will also be used in order to validate the simulation results.