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Tensile-strained crystalline aluminium nitride nanomechanical resonators
(2024) Nindito, Laurentius Radit; Chalmers tekniska högskola / Institutionen för mikroteknologi och nanovetenskap (MC2); Chalmers University of Technology / Department of Microtechnology and Nanoscience (MC2); Wieczorek, Witlef; Ciers, Anastasiia; Wieczorek, Witlef
High-Q_m nanomechanical resonators have proven to be a promising platform for advancing quantum technology. Resonators with Q_m×f_m products exceeding 6.2×10^12 Hz can sustain at least one coherent oscillation at room temperature, enabling their use in emerging quantum applications such as engineering long-lived quantum states and quantum sensing. Silicon nitride has become the favored material in this regard due to its great mechanical properties. However, it is an amorphous material that lacks additional functionalization capabilities beyond its admirable mechanical characteristics. We therefore explore crystalline aluminum nitride (AlN) as a promising alternative platform for high-Q_m nanomechanical resonators. Like other crystalline nitride materials, we expect AlN to possess robust mechanical properties. Moreover, the lack of centrosymmetry in its crystal structure gives rise to its piezoelectricity, making it a particularly versatile material for electromechanical applications. In this thesis, we studied four tensile-strained crystalline aluminum nitride samples with thickness ranging from 90nm to 295 nm. We extracted their elastic properties, including Young’s modulus, residual stress, and intrinsic quality factor. We then designed and realized phononically-shielded high-Q_m nanomechanical resonators out of them. Our bestperforming device achieved a quality factor of 8.6 × 10^6 and a Q_m × f_m product as high as 1.5 × 10^13, sufficient to provide a coherent oscillation at room temperature.
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Feasibility study on electric load adjustment for Rya Wastewater Treatment Plant
(2024) RIFAD, Abdulla; KALLUVAYAL BHASKARAN, Sivani; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik (ACE); Wilén, Britt-Marie; Wilén, Britt-Marie
This thesis investigates the feasibility of adjusting the electric load at the Rya wastewater treatment plant (WWTP), operated by the municipal company Gryaab AB in Gothenburg, Sweden, with the goal of reducing electricity usage momentarily and contributing to the local flexibility market, Effekthandel Väst (EHV). The Rya WWPP consumes approximately 240 GWh of electricity annually, of which most of the electricity is used for inlet pumping and aeration in the activated sludge process, accounting for 70% of the total consumption. As Gothenburg prepares for potential electricity shortages in the years ahead, this study focuses on momentarily reducing electricity usage during the peak hours (morning and evening) through short term and long-term flexibility measures. Flexibility refers to the ability to adjust electricity usage in response to market conditions or grid demands, either by reducing consumption or shifting it to different times. By analysing historical electricity usage data, the report evaluates different scenarios where Gryaab can participate in Effekthandel Väst by momentarily halting the operations or shifting the electricity demand to off-peak hours/periods. Results show that momentary shutdowns of key processes, can lead to significant reductions in electricity consumption. The study compares the financial and operational impacts of short-term versus long-term flexibility. While short-term flexibility offers immediate responses to market conditions and financial benefits, long-term flexibility provides consistent savings and aligns with strategic goals. The findings highlight the socio-economic and environmental benefits of Gryaab’s participation in Effekthandel Väst, including momentary reduced energy consumption and enhanced grid stability. The study concludes that optimised electricity management at the WWTP not only supports Gothenburg’s sustainability targets but also offers substantial cost-savings opportunities during high demand periods.
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A Model for Simulating FCR Prequalification Tests for Kaplan Turbines
(2024) Eriksson, Eddie; Chalmers tekniska högskola / Institutionen för elektroteknik; Chen, Peiyuan; Ekstrand, Christian
Abstract A Kaplan turbine was modeled in Simulink with the purpose of simulating prequalification tests for Frequency Containment Reserve (FCR) provision, based on technical requirements for FCR introduced in 2023. The model did not successfully predict fulfillment of steady-state requirements, and was too optimistic in its prediction of fulfillment of dynamic requirements. However, all tests predicted to fail also failed in real-world tests, indicating a potential use case for ruling out Kaplan turbines not suitable for FCR provision. A sensitivity analysis showed that simulation results were mostly unaffected by runner servo parameters, indicating a flaw in the model. Compensation with a first order low-pass filter significantly improved the accuracy of simulated dynamics. However, several model parameters, including the time constant for the low-pass filter, needed real-world tests for estimation. This reduced the likelihood of achieving high simulation accuracy ahead of conducting real prequalification tests. Using the simulated prequalification tests, methods for improving performance were explored. Both tuning the FCR controllers and the servos controlling guide vanes and runner blades were shown to improve dynamic performance, but tuning the servos improved the stability margins more. An approach to active power feedback was introduced and resulted in perfect fulfillment of the steady-state requirements. The dynamic performance requirements were not affected much, but the stability margins were severely worsened due to larger control movements at higher frequencies. The results suggested that fulfilling all technical requirements for FCR will be very challenging for Kaplan turbines. However, with increased market participation from other sources, this will likely not lead to insufficient FCR capacity in the near future.
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Design and analysis of a low speed and high power permanent magnet synchronous motor for a ship’s pod
(2024) Umami, Muhammad Irsyadul; Yang, Jinzhe; Chalmers tekniska högskola / Institutionen för elektroteknik; Thiringer, Torbjörn
Abstract The route between Gothenburg Port and Frederikshavn Port requires a ship propulsion system capable of delivering 200 kNm torque at 75 RPM. A Permanent Magnet Synchronous Motor (PMSM) is designed for this purpose, with Motor-CAD employed for comprehensive simulations, including geometric design and parameter optimization. The motor, rated at 1568 kW with a maximum current of 800 A, incorporates advanced design considerations to enhance performance. Magnet material selection plays a crucial role in determining the motor’s efficiency and losses. A comparison between the ferrite and the neodymium magnets reveals that the neodymium achieves a higher efficiency of 95.9% compared to 94.1% for the ferrite. Additionally, the neodymium results in significantly lower total losses of 64.19 kW, compared to 95.34 kW for the ferrite, demonstrating superior electromagnetic performance. To address thermal challenges, seawater heat dissipation is implemented as an effective cooling strategy, ensuring optimal system performance. Mechanical stress simulations further guarantee the safety and reliability of the vessel. A life cycle assessment (LCA) evaluates the environmental sustainability of the propulsion system, covering every phase from material selection to decommissioning. This work integrates thermal management, structural analysis, and sustainability to deliver an efficient and environmentally friendly marine propulsion system, offering valuable insights for the development of next-generation ship technologies.
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Digital Twins in Supply Chain: Catalyzing the change towards Circular Economy
(2024) Jensen, Johannes; Panneerselvan, Arunkumar; Chalmers tekniska högskola / Institutionen för teknikens ekonomi och organisation; Chalmers University of Technology / Department of Technology Management and Economics; Agrawal, Tarun; Agrawal, Tarun
This research explores the role of Digital Twin, a key technology in Industry 4.0, in facilitating the shift towards a circular economy via Supply Chains. It also addresses the potential obstacles that hinder the integration of Digital Twin into the Supply Chain. Data was gathered through a comprehensive literature review and interviews with researchers and company personnel to understand the degree to which Digital Twins are utilized in their organizations, and how it can guide them towards circularity in their supply chains.The study reveals that Digital Twins can enhance circularity in supply chains by extending the product lifespan through real-time monitoring and predictive maintenance, as well as by effectively tracking products returned by customers. However, implementing Digital Twin technology in extensive network like supply chains is challenging due to factors that complicate real-time data collection and time-consuming and costly process of modeling every asset. Therefore, in such large networks, a Digital Model could be a more practical and cost-effective solution.