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 - 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 - 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 -