The present investigation focuses on the study of the thermal inertia of buildings examining the extent to which the envelope and internal components can moderate their internal climate. Especial emphasis is given to the analysis of thermal mass effects in conditions of overheating in buildings with predominantly day-time occupancy schedules such as offices and mixed use buildings. The thesis comprises three parts. The first part discusses the principles and definitions of thermal inertia identifying a number of aspects which are relevant to the thermal performance of buildings. A review of the physical principles and parameters for quantification of heat storage in building elements is also included. The second part presents the results obtained from a series of field experiments carried out in six buildings in different locations to observe the thermal reaction on their internal spaces according to the particular thermal mass characteristics of each case. The third part is devoted to the analytic work by means of parametric studies and by comparing the field experiments findings with computer simulation results and exploring additional aspects of thermal mass effects. The analytic studies included the application of the diurnal heat capacity method for the calculation of internal temperature swings obtaining results in close agreement with both SERI-RES simulations and field measurements. A calculation worksheet is proposed to facilitate the internal swing calculations. Finally, the conclusions obtained from the results were used to define a series design measures aimed at the improvement of indoor thermal conditions by the optimisation of the effect of thermal mass of buildings in warm environments.

This thesis presents an analysis of the performance of optimisation using Kriging surrogate models on low-carbon building design problems. Their performance is compared with established genetic algorithms operating without a surrogate on a range of different types of building-design problems. The advantages and disadvantages of a Kriging approach, and their particular relevance to low-carbon building design optimisation, are tested and discussed. Scenarios in which Kriging methods are most likely to be of use, and scenarios where, conversely, they may be dis- advantageous compared to other methods for reducing the computational cost of optimisation, such as parallel computing, are highlighted. Kriging is shown to be able, in some cases, to find designs of comparable performance in fewer main-model evaluations than a stand-alone genetic algorithm method. However, this improvement is not robust, and in several cases Kriging required many more main-model evaluations to find comparable designs, especially in the case of design problems with discrete variables, which are common in low-carbon building design. Furthermore, limitations regarding the extent to which Kriging optimisa- tions can be accelerated using parallel computing resources mean that, even in the scenarios in which Kriging showed the greatest advantage, a stand-alone genetic algorithm implemented in parallel would be likely to find comparable designs more quickly. In light of this it is recommended that, for most lowcarbon building design problems, a stand-alone genetic algorithm is the most suitable optimisation method. Two novel methods are developed to improve the performance of optimisation algorithms on low-carbon building design problems. The first takes advantage of variables whose impact can be quickly calculated without re-running an expensive dynamic simulation, in order to dramatically increase the number of designs that can be explored within a given computing budget. The second takes advantage of objectives that can be !Keywords To Be Included For Additional Search Power: Optimisation, optimization, Kriging, meta-models, metamodels, low-energy design ! "2 calculated without a dynamic simulation in order to filter out designs that do not meet constraints in those objectives and focus the use of computationally expensive dynamic simulations on feasible designs. Both of these methods show significant improvement over standard methods in terms of the quality of designs found within a given dynamic-simulation budget.

Ce travail de thèse traite différents aspects de la conception basse consommation. Tout d’abord, le concept du calcul réversible, considéré comme le premier essai pour un calcul sans dissipation, est présenté. Puis, je me suis intéressée aux dissipations des circuits complémentaires MOS puisque c’est la logique la plus couramment utilisée dans les circuits numériques. J’ai proposé deux approches pour réduire la consommation de ces circuits numériques. La première approche porte sur la réduction de la dissipation due aux glitchs. J’ai proposé une nouvelle méthode qui consiste à adapter les tensions de seuil des transistors pour assurer un filtrage optimal de ces glitchs. Les résultats de simulation montrent que nous obtenons jusqu’à16% de réduction des glitchs, ce qui représente une amélioration de 18% par rapport à l’état de l’art sur la base des circuits de référence ISCAS85. La deuxième approche porte sur la réduction de la dissipation obtenue en faisant fonctionner les transistors MOS en régime d’ inversion faible (sous-seuil). Les circuits fonctionnant dans ce régime représentent une solution idéale pour les applications ultra-basse-consommation. Par contre, l’une des préoccupations majeures est qu’ils sont plus sensibles aux dispersions des processus de fabrication, ce qui peut entraîner des problèmes de fiabilité. Je propose un modèle compact qui détermine le point d’énergie minimum de façon analytique, donc sans recourir à une simulation type SPICE, tout en étant suffisamment précise vis-à-vis de la variabilité(due à la dispersion). L’écart de résultat entre le modèle compact et un modèle SPICE complet est de 6%. / This thesis focuses on different aspects of ”Low Energy Design”. First, reversible logic, as it is the first attempt for low energy computing, is briefly dis- cussed. Then, we focus on dynamic energy saving in the combinational part of CMOS circuits. We propose a new method to reduce glitches based on dual threshold voltage technique. Simulation results report more than 16% average glitch reduction. We also show that combining dual-threshold to gate-sizingtechnique is very interesting for glitch filtering as it brings up to 27 % energy savings. In the third part of this dissertation, we have been interested in sub-threshold operation where the minimum energy can be achieved using a reduced supply voltage. Sub-threshold operation has been an efficient solution for energy-constrained applications with low speed requirements. However, it is very sensitive to process variability which can impact the robustness and effective performance of the circuit. We propose a model valid in sub and near threshold regions in order to correctly estimate the circuit performance in a variability aware analysis. We provide an analytical solution for the optimum supply voltage that minimizes the total energy per operation while considering variability effects. Spice simulations matches the analytical result to within 6%.

The primary objective of this research was to investigate and develop an electrostatic energy-harvesting voltage-constrained CMOS/BiCMOS integrated circuit (IC) that harnesses ambient kinetic energy from vibrations with a vibration-sensitive variable capacitor and channels the extracted energy to charge an energy-storage device (e.g., battery). The proposed harvester charges and holds the voltage across the vibration-sensitive variable capacitor so that vibrations can induce it to generate current into the battery when capacitance decreases (as its plates separate). To that end, the research developed an energy-harvesting system that synchronizes to variable capacitor's state as it cycles between maximum and minimum capacitance by controlling each functional phase of the harvester and adjusting to different voltages of the on-board battery. One of the major challenges of the system was performing all of these duties without dissipating the energy harnessed and gained from the environment. Consequently, the system reduces losses by time-managing and biasing its circuits to operate only when needed and with just enough energy while charging the capacitor through an efficient inductor-based precharger. As result, the proposed energy harvester stores a net energy gain in the battery during each vibration cycle.