Campus Mobility for the Future: The Electric Bicycle

Sustainable and practical personal mobility solutions for campus environments have traditionally revolved around the use of bicycles, or provision of pedestrian facilities. However many campus environments also experience traffic congestion, parking difficulties and pollution from fossil-fuelled vehicles. It appears that pedal power alone has not been sufficient to supplant the use of petrol and diesel vehicles to date, and therefore it is opportune to investigate both the reasons behind the continual use of environmentally unfriendly transport, and consider potential solutions. This paper presents the results from a year-long study into electric bicycle effectiveness for a large tropical campus, identifying barriers to bicycle use that can be overcome through the availability of public use electric bicycles

Test generation considering operating conditions and diagnosis issues for large volume yield improvement

Testing and fault diagnosis are performed to detect and identify failures in manufactured integrated circuits. In this thesis, solutions to two important problems in testing and diagnosis are proposed. First, we address the problem of test generation considering operating condition variations. Variations in operating conditions cause path delays to change, resulting in different sets of critical paths at different operating conditions. We propose a method of identifying critical paths over a specified range of operating conditions. We also propose a method of N-detection test generation for transition faults, where each fault is tested through one or more longest paths considering a range of operating conditions. Second we address the problems of improving the speed of diagnosis and identifying systematic defects from a large amount of diagnosis data. Both these aspects of diagnosis can potentially enable rapid high volume diagnosis and help increase the rate of improving yield, or even the final yield itself. To speed up diagnostic fault simulation we propose using a combination of structural preprocessing and concurrent equivalence identification techniques. The structural method aids equivalence identification and together the two techniques speed up diagnosis. We propose an analysis method to identify systematic defects from large volume diagnosis data using design or process parameters. We also show a method to improve analysis sensitivity using multiple parameters. Finally, we suggest a procedure to order the multiple analysis steps to find strongly associated parameters

Numerical study of a concrete core temperature control building for tropics

Due to the hot and humid weather conditions in Singapore, air conditioning is widely used in buildings. In most cases, the air conditioning system consumes up to 50% of the total electricity consumption. One of the biggest challenges in achieving energy efficiency in buildings is to achieve a good indoor comfort level, while reducing the amount of energy consumed by air conditioning. One possible solution is radiant cooling systems; a high temperature cooling system that transports cooling energy to the building space through water, which is a more efficient heat transfer agent compared to air. In this research study, we investigate the performance of a specific type of radiant cooling system - Concrete Core Temperature Control (CCTC) using a transient building and energy modelling tool, CCTC is the practice of pumping cooling water through polymer pipes that are embedded in concrete of the building mass. The CCTC system makes use of the concrete mass as a heat sink for the internal heat Ioad in the building, hence cooling the building space. CCTC, which originated in Europe and is popular in temperate climates around the world, is yet to be validated and implemented in buildings in the tropics. A transient model of a typical commercial space in Singapore containing the CCTC system was developed and its performance measured under variable conditions. The performance of the CCTC was measured in terms of indoor occupant comfort and annual energy consumption. The results were compared to a conventional cooling and ventilation system. Annual weather data of Singapore and heat Ioad of a typical office were created to simulate the hypothetical building with and without CCTC using Transient System Simulation (TRNSYS) software. Variable conditions such as flow rate of the cooling water, mass of concrete and different floor zones in building were considered during the simulation exercise. It was found that, while achieving the same indoor comfort level, the building with the CCTC system was able to achieve significant energy savings at the chiller plant and air-distribution levels. The relative energy saving at chiller plant and air distribution is about 20% and 30%, respectively. On an annual basis, the building with CCTC consumed Iess energy overall when compared to the building without. Further to this, the a parametric analysis of CCTC design perimeters: mass flow rate of the chilled water and thermal mass containing the embedded pipes, was done.Master of Engineering (MAE

Evaluation of low-lift sensible cooling in the tropics using calibrated simulation models and preliminary testing

This article addresses an opportunity to improve Low Exergy air-conditioning system efficiencies in the tropics by incorporating ‘low-lift’ chillers. This paper builds on the 3for2 Project in Singapore, the region's lowest energy consuming office. Using calibrated energy models, laboratory measurements of the low-lift chiller and preliminary on-site testing, the performance of a low-lift chiller was studied in relation to a high-lift chiller. The paper concludes that the complete energy saving potential of high-temperature radiant cooling panels can be realized only if the high-temperature chilled water is produced directly by a low-lift chiller. The preliminary indicate that the peak and annual aggregate of radiant sensible cooling can be reduced by 22.8% and 13.5%ISSN:1876-610

Temperature dependent photovoltaic (PV) efficiency and its effect on PV production in the world : a review

Solar cell performance decreases with increasing temperature, fundamentally owing to increased internal carrier recombination rates, caused by increased carrier concentrations. The operating temperature plays a key role in the photovoltaic conversion process. Both the electrical efficiency and the power output of a photovoltaic (PV) module depend linearly on the operating temperature. The various correlations proposed in the literature represent simplified working equations which can be apply to PV modules or PV arrays mounted on free-standing frames, PV-Thermal collectors, and building integrated photovoltaic arrays, respectively. The electrical performance is primarily influenced by the material of PV used. Numerous correlations for cell temperature which have appeared in the literature involve basic environmental variables and numerical parameters which are material or system dependent. In this paper, a brief discussion is presented regarding the operating temperature of one-sun commercial grade silicon- based solar cells/modules and its effect upon the electrical performance of photovoltaic installations. Generally, the performance ratio decreases with latitude because of temperature. However, regions with high altitude have higher performance ratios due to low temperature, like, southern Andes, Himalaya region, and Antarctica. PV modules with less sensitivity to temperature are preferable for the high temperature regions and more responsive to temperature will be more effective in the low temperature regions. The geographical distribution of photovoltaic energy potential considering the effect of irradiation and ambient temperature on PV system performance is considered.Published versio

3D Printed Liquid Crystal Polymer Thermosiphon for Heat Transfer under Vacuum

A novel approach is presented to 3D print vacuum-tight polymer components using liquid crystal polymers (LCPs). Vacuum-tight components are essential for gas storage and passive heat transfer, but traditional polymer 3D printing methods often suffer from poor interfaces between layers and high free volume, compromising vacuum integrity. By harnessing the unique properties of LCPs, including low free volume and low melt viscosity, highly ordered domains are achieved through nematic alignment of polymer chains. Critical gas-barrier properties are demonstrated, even in thin, single-print line-walled samples ranging from 0.8 to 1.6 mm. A 200 mm evacuated thermosiphon is successfully printed, which exhibits a thermal resistance of up to 2.18 K/W and an effective thermal conductivity of up to 28 W/mK at 60 degrees C. These values represent a significant increase compared to the base LCP material. Furthermore, the geometric freedom, enabled by 3D printing through the fabrication of complex-shaped thermosiphons, is showcased. The authors study highlights the potential of LCPs as high-performance materials for 3D printing vacuum-tight components with intricate geometries, opening new avenues for functional design. An application of integrating 3D printed thermosiphons as selective heat transfer components in building envelopes is presented, contributing to greenhouse gas emissions mitigation in the construction sector.ISSN:2365-709XISSN:2365-709

Projected energy savings of a 3D printed selective heat transfer facade

Dynamic building facades offer untapped potential for reducing building energy consumption and emissions. However, there is currently a lack of suitable technologies for bespoke components for new and retrofit applications. In previous work, we developed a 3D printed polymer facade component that selectively acts as a thermal conductor or insulator depending on outdoor and indoor conditions. Our experiments demonstrate that the element can achieve effective thermal conductivities as low as 0.03 W/mK and as high as 28 W/mK in insulating and conducting modes. In this work, we assess the potential impact of this technology on reducing heating and cooling energy demand. We conducted a parametric analysis of ten physical characteristics of the facade component. Then, we simulated the façade component employed in 270 building typologies and climate combinations. Our results indicate annual energy reduction of up to 80 kWh/m2 (heating) and 15 kWh/m2 (cooling) for building typologyclimate combinations that can benefit the most from this technology.ISSN:1742-6588ISSN:1742-659

Parametric design of an additively manufactured building façade for bespoke response to solar radiation

The building construction industry is adapting Additive Manufacturing (AM) and robotic fabrication techniques to, among other efficiency and cost benefits, reduce the lifecycle Green House Gas (GHG) emissions of new buildings. This research aims to fabricate a low-GHG emission façade by encoding environmental performance using a combination of material selection, AM techniques, and bespoke geometry. This paper presents the design methodology, specifically the response to solar radiation (i.e. shading and daylight transmission). The key contribution of this publication is establishing the digital fabrication process of AM facades: beginning with performative parametric design, using empirical Bi-directional Scattering Distribution Function (BSDF) data of AM thermoplastic elements for daylight simulation to assess performance, and finally optimising the topology for a specific context (location and orientation).ISSN:1742-6588ISSN:1742-659