The search for more sustainable energy to match the growing energy demand begins with finding more dispatchable resources such as solar energy. As one of the promising solar technologies, concentrated solar power (CSP) has a full capacity to store thermal energy for extended operation. Nevertheless, some key components in CSP systems usually face extreme environment, such as uneven solar flux, cyclic thermal expansion, structural degradation on the solar absorber tubes in a Concentrated Solar Power Tower (CSPT) Plant. In this study, we applied Multiphysics simulation to explore the benefits of introducing optimized fins for heat transfer enhancement and uniform temperature distribution, the goal is to improve the thermal efficiency of such advanced solar absorber tubes. The results of this study can supply design guidance for the manufacturing process of absorber tubes, and eventually can benefit the solar energy community for the next generation of molten salt based CSP system.

RF receiver improvements in size, weight, power, and sensitivity are constant goals in the wireless communications community. The combination of phased array antenna systems with high speed analog to digital converters helps engineers meet these goals, because many of the analog components and tasks found in a traditional receive chain are moved into the digital domain. Although the hard work of signal reception is moved into digital signal processing, digital receivers rely on a high performance analog front end to properly condition a signal before analog to digital conversion. In this thesis, two RF front ends are developed for direct sampling L-band phased array receiver applications, which comprise the two main chapters of this document. Both RF front ends are developed on low cost, quick turnaround time PCB materials. Results for system gain and noise figure are presented for each front end. First, the development of an L-band analog front end for a direct sampling GPS phased array receiver is described, with particular attention to gain and noise figure in context of the full system link budget. The RF front end for the GPS phased array receiver meets design expectations by achieving a system gain of 65 dB and a system noise figure of 1.5 dB at the GPS L1 frequency. Second, the redesign and improvement of the Advanced L-band Phased Array Camera (ALPACA) RF over fiber transmitter is documented. New mechanical and electrical design requirements were brought on from the change of target observatory from the collapsed Arecibo obervatory in Puerto Rico, to the Greenbank Observatory in Greenbank, West Virginia. The ALPACA RF over fiber signal transport system with the redesigned transmitter reaches the design expectation of a system noise temperature contribution less than 1 K. Average gain of the RF over fiber system is 49 dB, gain differences between channels are less than 2 dB, and isolation between channels is better than 35 dB. Under optimal conditions, the noise figure of the RF over fiber link is 2.4 dB (213.3 K), which allows for up to 11 dB of attenuation to be added to any given transmit channel to level the gain across all 138 ALPACA channels.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第24963号 / 理博第4988号 / 新制||理||1712(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 澁谷 拓郎, 教授 久家 慶子, 教授 大見 士朗 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Parabolic solar trough receivers are used to collect heat via the mean of a heat transfer fluid. This component is one among a myriad of the Concentrated Solar Power (CSP) devices. Parabolic troughs reach high temperatures around 400 ºC. improving the Parabolic Solar Trough's receiver with an IR selective coating will increase the heat transfer absorbed by the heat transfer fluid and reduce the radiative heat loss. Thus, optimizing the receiver will ameliorate the efficiency of the electrical production for a CSP. The parabolic solar receiver existing in industry currently are made of stainless steel with no specific coating for IR solar rays spectrum selection. Therefore, the heat transferred through the absorber is limited to certain light spectrum. Furthermore, numerous receivers proposed are made from materials that contaminates their optical properties when oxidized such as aluminum [1]. The heat transfer and optical analysis of the PTC are essential to optimize and understand its performance under high temperatures and reduce the heat loss. In this paper, our focus is on presenting a super-lattice IR selective coating to minimize the radiative heat loss. Making use of the power of metamaterials to confection optical properties that are inexistent in nature, the coating will serve to maximize the tube's reflectance above 70% in the IR. Not only does the selective coating enhance the optical properties of the receiver, but also it ensures performance stability for high temperatures.

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