37 research outputs found
STACKED: The building design, systems engineering and performance analysis of plant factories for urban food production
No full textExpanding cities across the world rely increasingly on the global food network, but should they? Population growth, urbanisation and climate change place pressure on this network, bringing its resilience into question. For decades urban agriculture has been discussed in popular media and academia as a potential solution to improve food security, quality and sustainability. The new idol in this discussion is the plant factory: A fully closed system for crop production. Arrays of LEDs provide light and hydroponics provide water and nutrients to vertically stacked layers of crops, hence the term vertical farming. The plant factory features more extensive climate control than high-tech greenhouses. The question remains whether this level of climate control is necessary, effective and/or efficient. The scope of this research is therefore to investigate the potential and limitations of plant factories for urban food production. The STACKED method was developed to address the performance of plant factories across multiple scales, from leaf to facility to city. The role of plant processes in the total energy balance was outlined first. Performance was assessed by analysing the resource requirements, including energy, electricity, water, CO2 and land area use, for the production of fresh vegetables. The impact of façade and cooling system design was analysed in detail. Lastly, the effects of local food production on the urban energy balance were assessed for various scenarios. The results of this dissertation can serve as a foundation for future studies on the application of plant factories in both theoretical and real world applications.Expanding cities across the world rely increasingly on the global food network, but should they? Population growth, urbanisation and climate change place pressure on this network, bringing its resilience into question. For decades urban agriculture has been discussed in popular media and academia as a potential solution to improve food security, quality and sustainability. The new idol in this discussion is the plant factory: A fully closed system for crop production. Arrays of LEDs provide light and hydroponics provide water and nutrients to vertically stacked layers of crops, hence the term vertical farming. The plant factory features more extensive climate control than high-tech greenhouses. The question remains whether this level of climate control is necessary, effective and/or efficient. The scope of this research is therefore to investigate the potential and limitations of plant factories for urban food production. The STACKED method was developed to address the performance of plant factories across multiple scales, from leaf to facility to city. The role of plant processes in the total energy balance was outlined first. Performance was assessed by analysing the resource requirements, including energy, electricity, water, CO2 and land area use, for the production of fresh vegetables. The impact of façade and cooling system design was analysed in detail. Lastly, the effects of local food production on the urban energy balance were assessed for various scenarios. The results of this dissertation can serve as a foundation for future studies on the application of plant factories in both theoretical and real world applications.A+BE | Architecture and the Built Environment No 5 (2021)Climate Design and Sustainabilit
VERTICAL - The re-development of vacant urban structures into viable food production centres utilising agricultural production techniques
No full textProblem definition and objective. Population growth and rapid urbanisation may result in a shortage of food supplies in the future. Existing high-rise buildings may offer opportunities for the solution of this problem. The objective of this study was to investigate aspects of the requirements, design and energetic performances in the re- development of existing high-rise structures into vertical farming facilities. Study design. Literature review, followed by prospective performance analysis and feasibility study. Setting. Two representative office buildings in Delft, the Netherlands and in Wan Chai, Hong Kong SAR are selected as case studies. Main outcome measures. Production efficiency is expressed in production capacity, energy use and production output. Energy, taken as the performance indicator, is expressed as energy expenditure per production area. Results. Design guidelines were formulated according to data from the relevant literature. For both case studies the key features proved to be spatial layout, façade construction and production density. The split-production zone with a transparent non-insulated façade and a single production layer offers the best performance in terms of cooling energy use and total energy use, relative to the production area. However, for achieving maximum production in the existing buildings we prefer a design with a similar façade construction and layout but with four stacked production layers.Building TechnologyArchitectural Engineering and TechnologyArchitecture and The Built Environmen
Charge carrier mobility in disordered organic blends for photovoltaics
No full textCharge transport in disordered organic blends is studied theoretically by numerically solving the Pauli master equation. The influence of morphology, disorder, electric field, and charge carrier concentration on blend mobility is assessed. Important differences between neat materials and blends are found. The dependence of mobility on charge carrier concentration is more pronounced in blends and it is influenced by the electric field strength. At low charge carrier densities, blend mobility is found to decrease with increasing field. Additionally, the impact of the volume ratio of the constituent materials and their domain size on the mobility is presented. Especially for strongly disordered materials charge transport is favored by relatively large domains. To compare these theoretical findings with existing experimental mobility data, the current density in a space-charge-limited device is computed. The author finds that, for the parameters and morphologies studied, the apparent mobility in such a device decreases with increasing bias voltage.
CTE-STEM 2022: Proceedings of Sixth APSCE International Conference on Computational Thinking and STEM Education 2022
No full textWeb Information System
Systematic Side-Channel Analysis of Curve25519 with Machine Learning
No full textProfiling attacks, especially those based on machine learning, proved to be very successful techniques in recent years when considering the side-channel analysis of symmetric-key crypto implementations. At the same time, the results for implementations of asymmetric-key cryptosystems are very sparse. This paper considers several machine learning techniques to mount side-channel attacks on two implementations of scalar multiplication on the elliptic curve Curve25519. The first implementation follows the baseline implementation with complete formulae as used for EdDSA in WolfSSl, where we exploit power consumption as a side-channel. The second implementation features several countermeasures, and in this case, we analyze electromagnetic emanations to find side-channel leakage. Most techniques considered in this work result in potent attacks, and especially the method of choice appears to be convolutional neural networks (CNNs), which can break the first implementation with only a single measurement in the attack phase. The same convolutional neural network demonstrated excellent performance for attacking AES cipher implementations. Our results show that some common grounds can be established when using deep learning for profiling attacks on very different cryptographic algorithms and their corresponding implementations.Cyber Securit
