Despite of all the advances in smartphone technology in recent years, smartphones still remain limited by their battery life. Unlike other power hungry components in the smartphone, the cellular data and Wi-Fi interfaces often continue to be used even while the phone is in the idle state to accommodate unnecessary data traffic produced by some applications. In addition, bad reception has been proven to greatly increase energy consumed by the radio, which happens quite often when smartphone users are inside buildings. In this paper, we present a Short message service Push based Service (SPS) to save unnecessary power consumption when smartphones are in idle state, especially in bad reception areas. First, SPS disables a smartphone's data interfaces whenever the phone is in idle state. Second, to preserve the real-time notification functionality required by some apps, such as new email arrivals and social media updates, when a notification is needed, a wakeup text message will be received by the phone, and then SPS enables the phone's data interfaces to connect to the corresponding server to retrieve notification data via the normal data network. Once the notification data has been retrieved, SPS will disable the data interfaces again if the phone is still in idle state. We have developed a complete prototype for Android smartphones. Our experiments show that SPS consumes less energy than the current approach. In areas with bad reception, the SPS prototype can double the battery life of a smartphone.

The essay consists of three chapters. In chapter 1, I find that wages in U.S. regions have been diverging instead of converging from 1975 onward. This coincides with the period of accelerating skill-biased technological change. A decomposition of the divergence rate indicates three channels underlying the divergence: (1) an ever-widening wage gap between college graduates and high school graduates, (2) an increasing within-education group wage differential across regions, and (3) a concentration of skill composition across local labor markets. I then developed an endogenous skill-biased technology adoption model in which firms invest capital more intensively in regions with higher employment share of college graduates, explaining these three channels jointly. Finally I quantitatively assess the model by separately calibrating the regional aggregate production function; the results show that the relative skilled-labor efficiency has been persistently higher in skill-abundant regions, nevertheless the countrywide skill-biased technological change, is the main force making divergence happening. Chapter 2 studies energy-saving technological change in U.S. manufacturing sector, whose intensive margin and extensive margins are identified. I find that energy and capital are mostly complementary to each other, while labor is substitutive to energy-capital composite. However, a Cobb-Douglas nesting of labor is rejected. Quantitative exercise shows that in the post-crisis period, within in industry energy-saving technological change accounts for the largest proportion of the aggregate sectoral energy efficiency promotion in the long run. In contrast, in the short run, factor adjustment combined with sectoral shift accounts for the largest proportion of energy intensity reduction. Lastly, I provide evidence that structural change has taken place around the oil crisis in 1970s, which is consistent with the existing literature. In chapter 3, I documented the increasing dispersion of skill composition across different areas in the U.S. Meanwhile, the U.S. Housing Market has experienced a dramatic increase in the housing price, as well as a similarly increase in its dispersion across metropolitan areas. A set of related stylized facts are documented in this paper. First, the real wage goes similarly as real housing prices, but quantitatively different. Second, the rents and housing prices have not been going in the exactly same way, in terms of first two moments. Third, we find that local income inequality is positively correlated to the local housing price level. Based on these observations, we build a model where a dispersed skill-biased technology change can account for all the phenomena at the same time. / Ph. D.

no / An economizer, one type of heat exchangers, is specifically named to carry out heat exchange between hot gas and water. It is considered in this work to provide heat recovery between exhaust gas and boiler's feed water. As it has been studied to obtain high heat recovery with several designs, here the economizer is devised with new approach to achieve the best heat recovery as well as economical applicability in an existing pasteurized milk plant. The new economizer is designed to divide an exhaust gas into two portions flowing up on the left and right of the economizes passing across aligned banks of tubes and then flowing down and up again in an unmixed-triple pass fashion. The pressure drop and dew point temperature of corrosive acid depended on the fuel's type are also taken into account. Moreover, the mathematical models based on the energy equation in partial differential equations of two-dimensional initial value problems have been developed to simulate the performance of the newly designed economizer. The observation data prove that the designed economizer can achieve the heat recovery of the exhaust gas up to 57% with the average of 38% and can save the consumption of liquefied petroleum gas of about 13%.

No / In this work, energy consumption in a middle vessel batch reactive distillation (MVBRD) column is considered for the production of lactic acid via hydrolysis of methyl lactate. A dynamic optimization problem incorporating a process model is formulated to minimize the batch time which consequently minimizes the total energy consumption. The problem is subject to constraints on the amount and purity of lactic acid. The optimisation variables are reflux ratio and/or reboil ratio which are treated as piecewise constant. The earlier work of the authors on energy consumption in conventional batch reactive distillation column (CBRD) for the same reaction system is used for comparative analysis with the energy consumption in MVBRD. As an example, for a given separation task, the optimization results show that MVBRD is capable of saving over 23 % energy compared to energy consumption in CBRD column for the same task.

The goal of the master's thesis is elaborating energy audit within the current legislation in Czech republic. Thesis includes introduction, in which has been described photovolatics panels. The building is evaluated in terms of energetic, economic and environmental. Part of the energy audit was to designed and evaluated austerity measures.

The aim of the thesis is the energy rating of buildings. The introduction included the issues of the topic, including normative and legislative regulations, process energy performance certificates along with energy audits for residential building. The object is evaluated in terms of energy, economic and environmental. Within the energy audit was designed and evaluated austerity measures.

More than half of the world’s population lives in urban areas and this figure is expected to increase. The worldwide trend is in the direction of urbanization. Building sustainable cities is one of the sustainable development goals (SDGs) initiated by United Nations Sustainable Development Solutions Network. In the anthropocene of human induced climate change, what makes a city sustainable? This paper takes Beijing as the case study, uses building smart infrastructures and lowering ecological footprints as the main thread, uses a mixed research method of questionnaires, interviews and site survey, and discusses four aspects -- transportation, waste management, green spaces and energy saving buildings -- from employees’ perspectives of how to a build a sustainable city. This paper also discusses the relations between smart infrastructure and the resilience of a city, and relations between lowering ecological footprints and a green city, and draws a conclusion that a resilient and green city is a sustainable city. We can build a sustainable Beijing only through vigorously developed public transportation, well managed waste, the development of diversified green spaces, and buildings that efficiently use natural resources as energy supplies.

This research presents the design and evaluation of an intervention that introduces modification of time perceptions as one of the solutions to promote sustainable behaviours. It is demonstrated in this thesis that unnecessary energy use is often caused by temporal tensions, defined as the relation between actions to be performed and available time. This research proposes that it is possible to deliberately reduce temporal tensions, and this can motivate people to behave more sustainably. Persuasive technology and human-computer interaction provided the tools needed to manipulate time perceptions and therefore bring about changes in the specific behaviours that result in unnecessary energy usage. Previous studies indicate that behaviours play an important role in energy consumption. From the different domains of energy use that could be examined, cooking was chosen to be the platform where the studies on behaviour change and energy use would take place. How behaviours influence energy use motivated the design of empirical studies to understand behaviours related to domestic energy use and identify what are the determinants of these behaviours. Each determinant was related to a strategy to be included on a behaviour change intervention. A wider survey was developed to understand students acceptance of a set of proposed energy saving techniques, and resulted in a vast volume of information about user preferences and intentions to perform the suggested energy saving behaviours for cooking. It emerged that participants rushed into the cooking tasks without much deliberation, consequently not following preparation procedures and thus using more energy. Information gathered during the first studies also showed that participants behaviours were partially motivated by the need to speed up the cooking process in order to reduce boredom when they were waiting for the food to cook, consequently resulting in extra energy usage. The knowledge gathered from the preceding steps and a literature review informed the design of strategies to modify the non-sustainable behaviours and promote energy saving. A user-centred design process involving an idea generation session and scenario analysis was used to provide a set of strategies to be embedded in an intervention, containing the specific methods to tackle the correspondent determinants of behaviours. The specific needs of the cooking activity indicated that an electronic intervention was an adequate platform to be implemented and tested. Two high resolution working prototypes of the electronic interventions were developed as mobile phone applications. The final study comprised the evaluation of the proposed interventions in improving aspects of the cooking activity, the acceptance of the interventions and effectiveness in promoting energy saving.

Food retail with large supermarkets consumes significant amounts of energy. The environmental impact is also significant because of the indirect effect from CO2 emissions at the power stations and due to the direct effect arising from refrigerant leakage to the atmosphere. The application of trigeneration (local combined heat, power and refrigeration) can provide substantial improvements in the overall energy efficiency over the conventional supermarket energy approach of separate provision of electrical power and thermal energy. The use of natural refrigerants such as CO2 offers the opportunity to reduce the direct impacts of refrigeration compared to conventional systems employing HFC refrigerants that possess high global warming potential. One approach through which the overall energy efficiency can be increased and the environmental impacts reduced, is through the integration of trigeneration and CO2 refrigeration systems where the cooling generated by the trigeneration system is used to condense the CO2 refrigerant in a cascade arrangement. This research project investigates experimentally and theoretically, through mathematical modelling and simulation, such a system and its potential application to supermarkets. A small size CO2 refrigeration system for low and medium food temperature applications was designed and constructed to enable it to be integrated with an existing trigeneration system in the refrigeration laboratory at Brunel University to form an integrated trigeneration and CO2 refrigeration test facility. Prior to the construction, the design of the system was investigated using mathematical models developed for this purpose. The simulations included the CO2 refrigeration system, CO2 evaporator coils and the integration of the trigeneration and CO2 refrigeration systems. The physical size of the design and component arrangement was also optimised in a 3D AutoCAD model. A series of experimental tests were carried out and the results showed that the medium temperature system could achieve a very good COP, ranging from 32 to 60 due to the low pumping power requirement of the liquid refrigerant. The low temperature system performed with average steady state COP of 4, giving an overall refrigeration system COP in the range between 5.5 and 6. Mathematical models were also developed to investigate the application of the integrated trigeneration and CO2 refrigeration system in a case study supermarket. The models were validated against test results in the laboratory and manufacturers’ data. The fuel utilisation efficiency and environmental impacts of different trigeneration and CO2 refrigeration arrangements were also evaluated. The results indicated that a system comprising of a sub-critical CO2 refrigeration system integrated with a trigeneration system consisting of a micro-turbine based Combined Heat and Power (CHP) unit and ammonia-water absorption refrigeration system could provide energy savings of the order of 15% and CO2 emission savings of the order of 30% compared to conventional supermarket energy systems. Employing a trigeneration system with a natural gas engine based CHP and Lithium Bromide-Water sorption refrigeration system, could offer energy savings of 30% and CO2 emission savings of 43% over a conventional energy system arrangement. Economic analysis of the system has shown a promising payback period of just over 3 years compared to conventional systems.

The issue of low energy construction is currently actual and often discussed topic. The main reason is continuously increasing consumption and price of energy. Additionally, projections show this trend is not going to rapidly change in the upcoming years. The construction of buildings in low energy standard should become one of the most significant sources in energy savings in European Union for the upcoming period. Low energy constructions in contrast with standard constructions are distinguished not only because of low energy consumption and lower operating expenses but also for its favorable impact on the environment. The main purpose of this thesis will be the assessment of economical effectiveness of current low energy constructions and underline the importance of energy saving constructions by using LCA method as one of the possibilities in increasing the quality of environment.