TY - THES A1 - Atenkeng Tendong, Jean Carlos T1 - The Economic, Social and Environmental Valuation of the Hambach Forest. N2 - Forest ecosystems provide mankind with economic, social and environmental benefits called ecosystem goods and services. More often than not, some of these benefits are either mutually exclusive or come with negative impacts on the society or the environment. Hence, estimating the monetary value of these benefits is essential in decision making and policies on scarce natural resources. This thesis aims at estimating the monetary value of about 200 ha of the remaining Hambach forest which was once about 8,500 ha. In recent years, this forest has been the focus of numerous protests from environmentalists who believe that the German energy company RWE should not continue cutting down forest trees in order to extract its rich lignite reserves for electricity production. The environmentalists cite the loss of biodiversity and climate change as the base of their argument but fail to support this statement with an actual valuation study of the existing forest. On the contrary, RWE values the Hambach mine at €4 to €5 billion. In this light, this thesis makes a generous attempt at placing a monetary value on the 200 ha of Hambach forest using benefit transfer and meta-analysis as the main valuation techniques. Moreover, other techniques for a possible primary valuation project are elucidated. Besides, the social and environmental impacts of lignite mining are examined. Eventually, the obtained results are analyzed and discussed along with a concluding chapter on possible solutions and subsequent developments. KW - Hambach forest KW - Ecosystem services KW - Valuation KW - Benefit transfer KW - RWE Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-3732 ER - TY - THES A1 - Lyu, Sixiang T1 - Catalytic upgrading of ablative fast pyrolysis vapors with different catalysts N2 - As the fuel demands are increasing and oil reserves are depleting, the need for alternative fuels is becoming increasingly necessary. Fast pyrolysis has received considerable attention in the conversion of biomass into bio-oils which can be used for transportation fuel production. However, bio-oil produced from conventional fast pyrolysis has poor quality mainly due to its high amount of oxygenated compounds and requires upgrading before it can be used as transportation fuel. Catalytic upgrading is a prospective process in which oxygen can be removed from the bio-oil using a catalyst, which was studied in this paper. The main objective of this paper is to investigate the catalytic effects of six applied catalysts on the quality of the bio-oil derived from wheat/barley straw biomass. Fast pyrolysis of the biomass feedstock was performed in an ablative reactor at 550 ℃, and the pyrolysis vapors were led through a catalytic layer (at 400 ℃) in a second reactor for upgrading. Different properties were analyzed for evaluating the quality of the upgraded bio-oils, including water content (for calculating organic content), total acid number (TAN), higher heating value (HHV), elemental composition, and chemical composition. It was found that all catalysts, especially activated carbons (SC40 and SC44), reduced the tarry phase yield with increasing aqueous yield, resulting in the upgraded bio-oils with lower carbon and higher oxygen contents due to their catalytic activities. Moreover, the use of catalysts significantly reduced the sulfur content,making the final bio-oils more attractive due to the environmental concerns. SC40 was the best catalyst in increasing phenols yield and decreasing acids and ketones yields. The zeolite catalysts showed good selectivity to phenols production; the increasing load of nickel ions (Ni) on HZSM-5 slightly enhanced the formation of phenols and eliminated the formation of acids and ketones compared to unmodified HZSM-5. The upgraded bio-oil is still not qualified to be used as transportation fuels. However, it can be used as feedstock for producing specific chemicals in the modern refineries. KW - Biomass KW - Fast pyrolysis KW - Catalytic upgrading KW - Bio-oil KW - Activated carbons Y1 - 2018 ER - TY - THES A1 - Dai, Chenke T1 - Testing the Influence of Platinum Load on Performance of Fuel Cells Using Impedance Spectroscopy and Current Voltage Measurement N2 - Increasing Platinum catalyst loading in proton exchange membrane fuel cell is supposed to increase the performance and lifetime. However, Platinum is an extremely expensive material. Therefore, increasing loading could contribute to the price significantly. The aim of this work is to measure the proton exchange membrane fuel cell performance under three different catalyst loading on cathode and determine the optimum loading for performance in these three tested loading levels. The tested cathodic loadings are 0.3 mg/cm2, 0.6 mg/cm2 and 0.9 mg/cm2. By applying two methods: current-voltage measurement and electrochemical impedance spectroscopy, the open circuit voltages, polarization, power output and impedance were recorded. From the experiment, it is found that the internal resistance decreased with increasing Platinum loadings on the cathode. The simulation results indicate this change is mostly contributed by decreasing cathodic resistance. With increasing cathodic Platinum loading, the cathodic resistance decreases. It is also found during experiments, the polarization, open circuit voltage and power performance first increased and then stayed at same level. These indicators showed best performance at 0.6 mg/cm2 cathodic loading level. Combined with simulation results, the large impedance value of constant phase element in equivalent model for 0.9 mg/cm2 loading is considered as the reason why the power performance stop improving. Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-7730 ER - TY - THES A1 - Helou, Ziad T1 - Opportunities and challenges for the solar industry in Lebanon. N2 - Lebanon faces a significant energy crisis characterized by unreliable electricity supply, political instability, and outdated infrastructure. This thesis explores the potential of solar energy as a sustainable solution to address these challenges, focusing on economic, technical, and regulatory barriers while drawing comparative insights from Cyprus’s renewable energy model. The research examines three primary questions regarding the economic and technical challenges hindering solar energy adoption in Lebanon, the lessons that can be learned from Cyprus to inform solutions, and the comprehensive strategies that can support the development of Lebanon’s solar energy sector. The findings reveal that while Lebanon has experienced rapid growth in solar energy adoption, the sector is undermined by systemic issues such as low-quality imports, skill gaps, insufficient grid infrastructure, and the dominance of diesel generators. Comparative analysis with Cyprus underscores the importance of robust regulatory frameworks, financial accessibility, public-private partnerships, and accreditation systems for solar installers. Additionally, the analysis highlights the critical role of improving capacity factors in Lebanon, with findings showing that even a 1% increase could supply power to over 16,000 homes, emphasizing the potential efficiency gains for Lebanon’s solar energy sector. The thesis also evaluates Lebanon’s progress toward its 2030 renewable energy targets, noting that while the country appears to have met these targets in percentage terms, the achievement is largely a result of reduced electricity generation rather than genuine renewable capacity growth. Recommendations include enforcing quality standards, establishing national accreditation systems, addressing corruption, and leveraging international funding for infrastructure modernization and workforce development. This research emphasizes that Lebanon’s transition to renewable energy is not only a technical and economic endeavor but also a pathway to greater energy independence and environmental sustainability. KW - Solar energy KW - Renewable energy KW - Capacity factor KW - Grid modernization KW - Energy policy KW - Lebanon energy crisis KW - Solar photovoltaics KW - Energy transition KW - Distributed energy systems KW - Solar market regulation KW - Energy storage KW - Microgrid integration KW - Power grid stability KW - Reverse current flow KW - Islanding effect KW - Net metering KW - Sustainable development KW - Public-private partnerships KW - Solar waste management KW - Energy infrastructure Y1 - 2025 ER - TY - THES A1 - Besliu, Stas T1 - Emulsion splitting by applying CO2 and pressure N2 - This investigation is focused on analysing pressurized CO2 injection as a technique for breaking oil-in-water emulsions and proposing an efficient substitute for conventional methods. The destabilisation mechanisms, flotation rate acceleration, and segregation of phases in the system undergo considerable improvement through CO2 microbubbles formation. The ability to effectively separate and isolate aqueous and oil phases is important for treating industrial wastewater, hence optimizing waste reduction and resource recovery. The laboratory studies explore various operational parameters, such as CO₂ consumption efficiency, pressure variations, and residence time, in order to optimize splitting in various emulsion mixtures. The studies proved to effectively provide up to 95% total organic carbon (TOC) reduction, particularly achieved in combination with prolonged flotation and settling. Significantly, treatment by CO2-induced separations proved to have most efficiency in synthetic Sodium Lauryl Sulphate (SDS)-based emulsions and in industrial scenarios such as in cooling lubricants. In addition, prolonging flotation time to an overnight timeframe significantly increased TOC reduction in the case of the SDS emulsion. The presented results offer a new look over the experimental development of separation technologies, demonstrating the effective splitting of emulsions by injecting CO2 without additional pressure input and thus its feasibility in an industrial setting. In addition to providing a chemical-free separation alternative, this method offers the advantage of reduced energy input and the potential for CO2 recapture and reuse as well as oil recovery. KW - Emulsion splitting KW - oil-in-water emulsion KW - flotation KW - oil recovery. Y1 - 2025 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-21931 ER - TY - THES A1 - Schlüter, Leon T1 - Modelling Power Generation of Photovoltaics using Weather Data for the Design of an Electrolysis System N2 - To simplify the process towards the development of necessary hydrogen energy storage systems, this research project provides important information and tools for the planning process of such systems on a small scale. Several questions about a solar powered system using hydrogen for energy storage designed for the companies WSN and ESN, could not be answered sufficiently with the available tools which made developing new tools necessary. This tool incorporates various input variables and PV energy generation data to simulate the system's performance over a year into a Microsoft Excel based simulation. Within the framework of the tool developed over the course of the thesis, theoretical exploration of various options for system composition can take place. The insights gained there can be transferred to the implementation of actual projects and have an impact on the speed at which these projects can be realized. The results of the simulation led to the proposal of a system designed for the company WSN, where hydrogen serves as a long-term energy storage solution. Notably, this approach significantly reduces the surplus energy that goes unused, making the system more efficient. This research contributes valuable insights and practical tools to enhance the planning and implementation of small-scale hydrogen energy storage projects. KW - System simulation KW - Hydrogen energy storage KW - Green hydrogen KW - Renewable energy storage KW - Renewable microgrid Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-18547 ER - TY - THES A1 - Maung, Wai Lin T1 - Design, control and development of gas handling unit for hydrogen supply system for a 10kW fuel cell system N2 - Hydrogen fuel cells have been gaining attentions for marine mobility application because of it’s potential as a promising green technology with high energy intensity and reduced weight; Proton Exchange Membrane Fuel cell generates electric power by consuming hydrogen and oxygen as reactants. The fuel cell system consists of multiple sub-systems such as anode gas supply components, cathode air compressors with humidification systems and a cooling circuit. They all must be regulated according to the nominated working conditions of the stack, and one of the most important parameters is the hydrogen supply feed of the fuel cell system. The hydrogen supply system must be robust to handle different working conditions of the stacks such as load fluctuation, purging of water and nitrogen from anode side and subsequent pressure fluctuations. It is critical to control the anode pressure with respect to varying conditions since unbalanced H2 supply can lead to membrane failure, hydrogen starvation and drying out which can lead to deterioration and reduce the lifetime of the stack. The thesis describes the development of “Gas Handling Unit” as the effective hydrogen supply system which will be incorporated with a particle filter, switch off solenoid valve, proportional valve, pressure transmitters and a pressure safety valve for venting during critical conditions. The design and control of the gas handling unit is detailed along with material compatibility of metals and sealants polymers with hydrogen applications. The relevant safety regulations and technical standards are identified and followed during the design process. Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-20335 ER - TY - THES A1 - Izzuddin, Kamal T1 - Experimental and Simulative Study on the Performance of PEM Fuel Cell under Different Operating Conditions N2 - The aim of the thesis is to study the influence of operating conditions on the performance of the proton exchange membrane fuel cell (PEMFC) such as temperature, cathode stoichiometry and cathode relative humidity. The experiment is conducted at temperature points of 60°C, 70°C and 80°C, where at each temperature point cathode stoichiometry of 2 and 5 are set. Within each stoichiometry, the cell is operated at cathode relative humidity of 50%, 75% and 100%. The fuel cell performance is analyzed using two methods, current-voltage measurement, and the electrochemical impedance spectroscopy, where the polarization curves, power output density and high-frequency resistance (HFR) are recorded. A numerical analysis is then conducted on a 3-dimensional straight single channel fuel cell and is fitted with the data measured experimentally. Increasing the temperature has a different degree of improvement on the fuel cell’s performance based on its cathode stoichiometry and relative humidity settings. The HFR measurements provide an insight into the voltage loss that is exerted by the fuel cell on each test condition. The numerical analysis shows that the impact of operating conditions does not exhibit any significant differences on the fuel cell model. KW - Proton exchange membrane fuel cell KW - Current and voltage measurement KW - Electrochemical impedance spectroscopy KW - High-frequency resistance KW - CFD KW - Numerical analysis Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:1383-opus4-15909 ER -