Dissertations / Theses on the topic 'Air conditioning in large buildings'

This study presents the complete design of a photovoltaic system in commercial buildings. PV installation for Multiarena was primary used for internal consumption, rest of production will be sent according intentions in grid. Project presents theoretical demand calculations for building consumptions. According to the theoretical calculations numerical study has been provided by software Indoor Climate and Energy program. Detailed electric optimization strategy can be founded in project description, as well as the sizing of the photovoltaic installation and economic and financial issues related to it. Study presents several models for photovoltaic system and their economic analysis. Environmental issues can be founded at the end of the study.

Active and passive cooling methods have been the subject of much investigation. Nevertheless, there remains a significant opportunity to utilise the so-called "responsive building elements" and to arrange for cooperative deployment with downsized, conventional HVAC systems. The integration of an air culvert with an active cooling system along with associated control is the subject of this thesis. The issues studied within this thesis are as follows. The quantification of air culvert thermal efficacy. The elaboration of an integrated system design method that accounts for the transient interaction between the air culvert and the air conditioning systems. The requirement for hybrid system control when deployed within different climates. The ESP-r system was adopted within the present work. A ground temperature model was established for the hot/dry climate location selected and validated against measured soil temperature profiles. A culvert model was derived and verified empiricall y and by inter-model comparison. Results showed that the ESP-r model can robustly quantify the thermal performance of an air culvert. The culvert was then coupled to a residential villa situated in the hot/arid climate domain and its contribution explored. A constant air volume air-conditioning system was then linked to the culvert-building model and used to research approaches to the control of such a hybrid cooling system. A general control strategy was then devised corresponding to specific objectives and constraints. Results confirmed that the final control set-up can be implemented for a culvert/HVAC hybrid cooling system regardless of climate type, with cooling load matching in excess of 85% keeping indoor resultant temperatures within comfort threshold limits. The project conclusion is that a culvert may be deployed in a manner that allows significant down-sizing of conventional cooling plant, thereby achieving both capital and running costs savings without appreciable loss.

The research has shown that cooling in UK Office buildings can be undertaken far more efficiently than generally occurs at present, by combining the selection highly efficient air conditioning systems, such as chilled ceilings, and by ensuring building design and operation is undertaken in an energy efficient manner. The potential energy consumption, carbon emissions and running cost savings appear to be comfortably over 50% compared to current practice.

Modern development in many Third World countries in the hot regions of the world,, have been accompanied by the construction of highly energy-wasteful buildings. The interiors of these buildings have to be mechanically airconditioned in order to achieve thermal-comfort conditions. The consequence of this, has been the rapid increase in electricity-generating plant capacity to match demand (of which, for example at present in Oman, more than 70% nationally is used for air-conditioning modern, energyinefficient buildings). The aim of this work was to find the most suitable way of stabilising or even reducing the electricity demand in a country like Oman. The first step taken to achieve this aim, was to study and draw out lessons from the vernacular architecture of the different climatic regions in Oman. This has been followed by a literature survey that looks at passive and active natural cooling techniques for buildings in hot climates. Mathematical models were then developed to analyze and compare those passive techniques that are most suitable for an environment like that of Oman. Different ways of reducing the heat gain through the roof were investigated and compared. These include the addition of insulation, shading, air-cooling of the roof when the ambient air temperature is lower than that of the roof, and roof ponds. Roof ponds were found to be the most effective of those techniques analyzed. An improved design of the roof pond (the Water Diode roof pond) that eliminates the need for covering the roof pond during the day and uncovering it at night, was suggested and analyzed. The analysis showed promising results. Mathematical models were also developed to analyze and compare dif f erent ways of reducing the heat gain through the walls. These included the use of closed cavities, naturally ventilated cavities, the addition of insulation, and the effect of using brick as compared to concrete block. The analysis suggested that the combination of a Water Diode roof pond and insulated brick wall construction will reduce the heat gain through the envelope of a single room by more than 90%, when compared to a room with un-insulated roof and single-leaf concrete block walls. An empirical validation of the mathematical models was conducted. The results showed a good agreement between the actual and predicted values. An economical analysis of the commonly used roof and wall constructions in Oman, was also conducted. This compared the life-cycle cost of nine different construction techniques, with eight different airconditioning schedules. The result of this analysis showed a clear advantage of using roof insulation, reflective double glazing, and insulated walls with brick outer-leaf and concrete block inner-leaf.

The aim of this thesis is to study the energy performance of a building integrated heating and cooling system. The research objectives are to investigate the system operating characters, to develop mathematical models for the heating and cooling systems, to demonstrate the technologies experimentally, to identify the best designs for a combined system and to investigate the cost effectiveness of the system. The main components of the systems are the aluminium plate façade and the building wall behind it, these form a plenum between them and the air is then heated or cooled as it flows through this plenum. Mathematical models were developed based on the energy balance equations and solved by matrix inversion method. These models were then validated with experimental results. The experiments were carried out in the laboratory with a facade area of 2m2. Two designs of facade were tested, i.e. flat and transpired plates. Results showed that the transpired design gave better thermal performance; the system efficiency for the flat plate was only about 30%, whereas it was about 85% for the transpired plate. On the other hand, a cooling system with double plenums was found to be better than a single plenum. Thus, a transpired plate with two plenums was identified as the best design for space heating and cooling. The cooling efficiency was nearly 2.0 even at low solar radiation intensity. A simulation study was carried out by assuming a 40m2 of façade was installed on an office building in London. The yearly energy saving was estimated as 10,877kWh, which is equivalent to 5,874kgCO2/year of emission avoidance. The system is calculated to cost about £70/m2, and for a discount rate of 5% and 30 years of lifetime, the payback period for this system would be less than a years.

This study aims to improve the performance of existing indirect evaporative coolers. A new dew point indirect evaporative cooler with counter-current heat/mass exchanger was developed in this research by optimal design, material selection, numerical simulation, experimental investigations and economic, environmental, regional acceptance analysis. A new dew point heat/mass exchanger using a counter-current flow pattern was designed by numerical simulation in terms of material, structure, geometrical sizes and operating conditions. The numerical results indicate that under a typical cooling design condition, i.e., 35oC dry-bulb/24oC wet-bulb temperatures, the heat exchanger could achieve a wet-bulb effectiveness of approximately 1.4. The results of numerical simulation are consistent with some published test data. Based on the numeric results and the material selection determined from a set of related tests, a prototype dew point heat/mass exchanger and the associated air cooler was designed and constructed in laboratory. Testing was carried out to evaluate the performance of the experiment prototype. The results indicate that the wet-bulb effectiveness of the prototype ranged from 55% to 110% for all test conditions. The power consumption of the prototype ranged from 10 to 50 W with energy efficiency (or COP) rated from 3 to 12. It is also found that the water consumption of the prototype was very small which ranged from 0.2-1.3 litre/h. A comparison between the numerical and experimental results was carried out and the reasons for the discrepancy were analysed. This research also investigates the feasibility, economic and environmental potential of using a dew point cooler in buildings in Europe and China. From the related studies in this thesis, it is concluded that the dew point cooler can achieve a higher performance (in terms of effectiveness and energy efficiency) than the typical indirect evaporative coolers without adding too much cost. It is found that the effectiveness and energy efficiency of the heat/mass exchanger in the cooler are largely dependent upon channel geometries, the intake air velocity, temperature, humidity and the working-to-intake air ratio but less on the feed water temperature. To maximise effectiveness and energy efficiency, it is suggested that 1) the channel height and the length of exchanger should be set below 6 mm and 1-1.2 m respectively; 2) the intake channel air velocity should be controlled to 0.5-1 m/s; and 3) the working-to-intake air ratio should be adjusted to 0.4-0.5. It is also concluded that the dew point system is suitable for most regions with dry, mild and hot climate. It is, however, unsuitable for humid regions where the system is used as a stand-alone unit. Compared to the conventional mechanical compression cooling system, the dew point system has a significantly higher potential in saving energy bills and reducing carbon emission. A project to construct an 8 kW commercial dew point cooler is currently under development with the assistance of a Chinese company. By the optimisation of material, structure and geometries, the cooler is expected to achieve a cooling output of 8 kW at the inlet air of 38oC dry-bulb/ 21oC wet-bulb temperatures, with a wet-bulb effectiveness of 1.02 at 1530 m3/h of supply air flow and 1200 m3/h of discharge air flow, whereas the power input of the unit is about 450 W and the energy efficiency (or COP) at 18.5.

The use of vegetation to block shortwave radiation can reduce cooling loads in hot climates. From July 22nd, 1989 to October 7, 1989, this study, using shade cloth to simulate vegetative canopies, compared the electricity used for air conditioning between quarter-scale models. The treatments were: (1) canopies of the same density on east, west, and/or south walls, (2) wall canopies versus roof canopies of the same density, (3) wall canopies of different densities, and (4) roof canopies of different densities. Although the savings in electricity in any treatment was usually less than 11%, the results showed: dense canopies gave better savings than medium canopies, which, in turn, gave better savings than the least dense canopies; wall canopies gave better results than a roof canopy; an east wall canopy gave better results than a west wall canopy; and shading all walls except the north gave better results than shading only the east and west wall.

In many dry desert climates such as in Kuwait, the summer season is long with a mean daily maximum temperature of 45°C. A round 80% of total electricity generation is consumed by air-conditioning systems in domestic buildings. A hybrid cooling technique to reduce the domestic cooling demand would have both environmental and economic benefits for Kuwait. A passive cooling technique, which assists the situation, is ground cooling. In this thesis a thermal model of an earth air heat exchanger (EAHE) has been developed to calculate the pre-cooling of ventilation air that can be achieved for a building through use of a buried pipe below ground surface.

This study investigated the effectiveness of wind-driven natural ventilation in courtyard and atrium-type buildings, particularly in the context of ventilative cooling. Courtyard and atrium buildings are currently enjoying great popularity. Perhaps a primary reason for their revival comes from the energy and environmental awareness of the current period, in which courtyard and atrium concepts are emerging as very promising. Wind-driven ventilation is one of the most basic and probably among the most efficient ways to prevent overheating, and provide cooling in the summer season, especially in humid climates. A review of previous works showed that little attention has been given to the wind-driven natural ventilation capability of these structures, and to the means of maximizing this ventilation. This study was thus aimed to fill part of the gap in this subject. In order to evaluate the wind-driven ventilation effectiveness of these structures, and to examine some of the influential parameters, experimental wind tunnel tests were made. Actual indoor air flows were measured in small replica models of four-storey courtyard and atrium buildings by means of small calibrated orifice plates. A parametric study of the geometry of the courtyard was made in isolation conditions, where the depth and breadth of the courtyard were systematically varied. Several atrium ventilation modes were tested both in isolation and in urban terrains. The tests involved different roof geometries and various roof porosities. The measurements were followed by a discussion on the validity of simple computational methods to predict airflow in atria. The investigation portrayed the importance of some factors, such as the wind orientation rather than the courtyard geometry, for enhancing the flow in these structures. The superiority of some atrium designs over the courtyard types, particularly in sheltered sites, was underlined. The study concluded with a discussion of design guide-lines and referred the reader to an application as an example, describing a simple step-by-step method to estimate the cooling benefits of these structures in a particular site, and making use of the measurement data obtained from the study.

Natural ventilation is a passive cooling method that has significant potential to reduce building energy consumption and to positively contribute to indoor environmental conditions. Because the window is an important element in naturally ventilated buildings, it can be used to adjust indoor air flow. However, lack of knowledge about occupants‘ window control behaviour and how this relates to different window typology would result in discrepancy between actual and proposed building performance. And also, limit the potential of natural ventilation in the building. This thesis explores the relationship between indoor air velocity, occupants‘ window control behaviour and window design. This study is based on field measurement and occupant comfort survey in four office buildings in a hot and humid climate in South-east China. The field study was carried in September and October of 2012. The indoor and outdoor thermal conditions, indoor air flow speed, window state and effective opening area were monitored. Occupant thermal comfort questionnaires were given to participants four times a day to record their comfort perceptions in the office. The field study gives new insights into the correlation between indoor air speed, occupants‘ window control behaviour and window design. For the research 14400 set of indoor and outdoor temperature and relative humidity data, 174560 indoor air velocity records and 1344 copies of questionnaires were collected. The results of this study defined comfort zone for this climate which is consistent with Givoni‘s comfort zone for a hot and humid climate. The indoor air flow path is identified by measuring the indoor air velocity across different parts of the office and related window opening combinations. Besides, the effective opening area is reduced with decreased indoor air temperature when the indoor air temperature is lower than 25°c. None of the windows is closed when the indoor air temperature is higher than 28°c. During the working hours, the changing of effective opening is related to the air velocity across the desk surface. And measured maximum indoor air velocity measured around the occupant is 1.8m/s which did not result in occupants‘ window changing behaviour to adjust for comfort. In conclusion, this study proved that occupants who live in hot and humid climate can accept higher humidity level. If the air velocity can be avoided across the occupant‘s working surface, then a higher indoor air velocity is still accepted by occupant as within their comfort threshold. So, there are great potentials for occupant to extend their comfort threshold and adapt to the local climate. Besides, window opening type and position has a significant impact on indoor air velocity and pattern. It would also influence convective cooling affect and occupant thermal comfort. This is evident from the indoor air velocity measurement results and the occupant comfort survey results. In addition, accessibility is important to window design. In the naturally ventilated office building, if occupants find it difficult to operate the window, this will have an influence on the natural ventilation potential in the building and cause the occupant discomfort. Thus, the findings of this study will help architects and engineers to design naturally ventilated office buildings in South-east China.

An examination of contemporary office buildings in the warm humid region of Kenya revealed the predominance of highly glazed lightweight buildings that are prone to overheating and rely on costly and unsustainable active climate control systems. In the midst of growing energy demand and a potential deficit in supply, the influx of these poorly designed buildings has intensified the need to explore viable climate-responsive design alternatives suitable to local conditions that can extend occupant comfort and reduce the need for energy intensive environmental control systems. This view is shared by the Kenyan government which has set ambitious targets to develop and enforce national codes for energy efficiency and conservation in buildings by 2030. However, despite the clear and urgent need, research shows that little work has been developed to date that can be applied to the Kenyan context and climate. In this research, ways of improving the thermal comfort and performance of office buildings in the warm humid city of Mombasa (latitude 4°S) were explored. The work was developed through a series of field studies of local vernacular and modern case study buildings and subsequent computer simulations. From this, vernacular Swahili-inspired design strategies were derived and the application of the potentially most significant mitigation strategy to typical local office buildings examined further. Although other work exists elsewhere that may be comparable to parts of this study, this is the first effort that brings together the post occupancy evaluation of buildings in Mombasa, a thorough investigation of the effectiveness of the vernacular strategies found in Swahili architecture, and the validation of the application of these strategies to modern offices. Initial findings derived from a parametric study revealed external shading to be the most effective design strategy as it alleviated solar heat gain transmitted through glazing into buildings, resulting in a significant reduction in discomfort hours. Subsequently, using a series of dynamic computer simulations run for a typical office building in Mombasa, the average monthly solar heat gain coefficient (SHGC) values were derived for a typical year. These previously unavailable latitude (and hemisphere) specific solar path indices were deemed critical in the provision of essential data for effective external shading device design. The findings indicated that low SHGC values of under 0.5 gave the general indication of low percentage of discomfort hours (under 10%). Additionally, estimates of potential annual cooling energy savings of up to 60% were made based on the reduction of SHGC values for shading elements of practicable size. The application of these study findings to two local office buildings revealed that the derived SHGC values and energy estimates provide useful references when considered for similar type office buildings on similar latitudes. For both buildings, it was predicted that energy savings of 15% to 61% could be achieved from the application of suitably sized external shading devices. It was suggested that this type of information would encourage designers to use external shading devices as a method of maintaining thermal comfort, conserving energy and lowering operating costs in office buildings. Finally, recommendations for the incorporation of minimum shading standards in building regulations have been made and presented in a design guidance document.

The work presented in this thesis investigates design, computer modelling and testing a sub-wet bulb temperature evaporative cooling system for space air conditioning in buildings. The context of this evaporative cooling technology design is specifically targeted at locations with a hot and dry climate such as that prevailing in most regions of Middle East countries. The focus of this technology is to address the ever-escalating energy consumption in buildings for space cooling using mechanical vapour compression air conditioning systems. In this work, two evaporative cooling configurations both based on sub-wet bulb temperature principle have been studied. Furthermore, in these designs, it was sought to adopt porous ceramic materials as wet media for the evaporative cooler and as building element and use of heat pipes as heat transfer devices. In the first test rig, the prototype system uses porous ceramic materials as part of a functioning building wall element. Experimental and modelling results were obtained for ambient inlet air dry bulb temperature of 30 and 35oC, relative humidity ranging from 35% to 55% and intake air velocity less than 2 (m/s). It was found that the design achieved sub-wet bulb air temperature conditions and a maximum cooling capacity approaching 242 W/m2 of exposed ceramic material wet surface area. The wet bulb effectiveness of the system was higher than unity. The second design exploits the high thermal conductivity of heat pipes to be integrated as an effective heat transfer device with wet porous ceramic flat panels for evaporative cooling. The thermal performance of the prototype was presented and the computer model was validated using laboratory tests at temperatures of 30 and 35oC and relative humidity ranging from 35% to 55%. It was found that at airflow rates of 0.0031kg/s, inlet dry-bulb temperature of 35oC and relative humidity of 35%, the supply air could be cooled to below the inlet air wet bulb temperature and achieve a maximum cooling capacity of about 206 W/m2 of wet ceramic surface area. It was shown that the computer model and experimental tests are largely in good agreement. Finally, a brief case study on direct evaporative cooling thermal performance and environmental impact was conducted as part of a field trip study conducted on an existing large scale installation in Mina Valley, Saudi Arabia. It was found that the evaporative cooling systems used for space cooling in pilgrims’ accommodations and in train stations could reduce energy consumption by as much as 75% and cut carbon dioxide emission by 78% compared to traditional vapour compression systems. This demonstrates strongly that in a region with a hot and dry climate such as Mina Valley, evaporative cooling systems can be an environmentally friendly and energy-efficient cooling system compared to conventional vapour compression systems.

The wide uses of solar energy technology (solar thermal collector, photovoltaic and heat pump systems) have been known for centuries. These technologies are intended to supply domestic hot water and electricity. However, these technologies still face some barriers along with fast development. In this regards, the hybrid energy system combines two or more alternative technologies to help to increase the total efficiency of the system. Solar assisted heat pump systems (SAHP) and photovoltaic/thermal collector heat pump systems (PV/T-HP) are hybrid systems that convert solar radiation to thermal energy and electricity, respectively. Furthermore, they absorb heat first, and then release heat in the condenser for domestic heating and cooling. The research initially investigates the thermal performance of novel solar collector panels. The experimental results indicate an average daily efficiency ranging from 0.75 to 0.96 with an average of 0.83. Compared with other types of solar collectors, the average daily efficiency of novel solar thermal collectors is the highest. The research work further focuses on the integrated system which combines solar collector and air source heat pump (ASHP). The individual components, configurations and layout of the system are illustrated. Theoretical analysis is conducted to investigate thermodynamic cycle and heat transfer contained in the hybrid system. Laboratory tests are used to gauge the thermal performance of the novel SAHP. A comparison is made between the modelling and testing results, and the reasons for error formation are analysed. The research then considers the specially designed PV/T collector that employs the refrigerant R134a for cooling of PV modules and utilizes the glass vacuum tubes for reducing the heat loss to the ambient air. The PV/T collector consists of 6 glass vacuum tube-PV module-aluminium sheet-copper tube (GPAC) sandwiches which are connected in series. The theoretical analysis and experimental tests all give the satisfactory results of up to 2.9% improvement of electrical efficiency compared with those without cooling. The research finally focuses on the integrated heat pump system where the PV/T collector acts as evaporator. Based on the energy balance of the four main components of the heat pump system, a mathematical model of the heat pump system is presented. When the instantaneous ambient temperature and solar radiation are provided, results are obtained for the spatial distributions of refrigerant conditions, which include temperature, pressure, vapour quality and enthalpy. Detailed experimental studies are carried out in a laboratory. Three testing modes are proposed to investigate the effect of solar radiation, condenser water flow rate and condenser water supply temperature on energy performance. The testing results show that an average coefficient of performance (COP) reached 3.8,4.3 and 4.0 under the three testing modes with variable radiation, condenser water supply water temperature and water flow rate, respectively. However, this could be much higher for a large capacity heat pump system using large PV panels on building roofs. The COP increases with the increasing solar radiation, but decreases as the condenser water supply temperature and water flow rate increases.

The UK building stock accounts for about half of all energy consumed in the UK. A large portion of the energy is consumed by nondomestic buildings. Offices and retail are the most energy intensive typologies within the nondomestic building sector, typically accounting for over 50% of the nondomestic buildings’ total energy consumption. Heating, ventilating and air conditioning (HVAC) systems are the largest energy end use in the nondomestic sector, with energy consumption close to 50% of total energy consumption. Different HVAC systems have different energy requirements when responding to the same building heating and cooling demands. On the other hand, building heating and cooling demands depend on various parameters such as building fabrics, glazing ratio, building form, occupancy pattern, and many others. HVAC system energy requirements and building energy demands can be determined by mathematical modelling. A widely accepted approach among building professionals is to use building energy simulation tools such as EnergyPlus, IES, DOE2, etc. which can analyse in detail building energy consumption. However, preparing and running simulations in such tools is usually very complicated, time consuming and costly. Their complexity has been identified as the biggest obstacle. Adequate alternatives to complex building energy simulation tools are regression models which can provide results in an easier and faster way. This research deals with the development of regression models that enable the selection of HVAC systems for office buildings. In addition, the models are able to predict annual heating, cooling and auxiliary energy requirements of different HVAC systems as a function of office building heating and cooling demands. For the first part of the data set development used for the regression analysis, a data set of office building simulation archetypes was developed. The four most typical built forms (open plan sidelit, cellular sidelit, artificially lit open plan and composite sidelit cellular around artificially lit open plan built form) were coupled with five types of building fabric and three levels of glazing ratio. Furthermore, two measures of reducing solar heat gains were considered as well as implementation of daylight control. Also, building orientation was included in the analysis. In total 3840 different office buildings were then further coupled with five different HVAC systems: variable air volume system; constant air volume system; fan coil system with dedicated air; chilled ceiling system with embedded pipes, dedicated air and radiator heating; and chilled ceiling system with exposed aluminium panels, dedicated air and radiator heating. The total number of models simulated in EnergyPlus, in order to develop the input database for regression analysis, was 23,040. The results clearly indicate that it is possible to form a reliable judgement about each different HVAC system’s heating, cooling and auxiliary energy requirements based only on office building heating and cooling demands. High coefficients of determination of the proposed regression models show that HVAC system requirements can be predicted with high accuracy. The lowest coefficient of determination among cooling regression models was 0.94 in the case of the CAV system. HVAC system heating energy requirement regression models had a coefficient of determination above 0.96. The auxiliary energy requirement models had a coefficient of determination above 0.95, except in the case of chilled ceiling systems where the coefficient of determination was around 0.87. This research demonstrates that simplified regression models can be used to provide design decisions for the office building HVAC systems studied. Such models allow more rapid determination of HVAC systems energy requirements without the need for time-consuming (hence expensive) reconfigurations and runs of the simulation program.

Among many smart grid technologies, demand response (DR) is gaining increasing popularity. Many utility companies provide a variety of programs to encourage DR participation. Under these circumstances, various building energy management (BEM) systems have emerged to facilitate the building control during a DR event. Nonetheless, due to the cost and return on investment, these solutions mainly target homes and large commercial buildings, leaving aside small- and medium-sized commercial buildings (SMCB). SMCB, however, accounts for 90% of commercial buildings in the US, and offer great potential of load reduction during peak hours. With the advent of Internet-of-Things (IoT) devices and technologies, low cost smart building solutions have become possible for the SMCB; nonetheless, related intelligent algorithms are not widely available. This dissertation work investigates automated building control algorithms, tailored for the SMCB, to realize automatic device control during DR events. To be specific, a control framework for Air-Conditioning (AC) units� coordination is proposed. The goal of such framework is to reduce the aggregated AC power consumption while maintaining the thermal comfort inside a building during DR events. To achieve this goal, three major components of the framework were studied: building thermal property modeling, AC power consumption modeling and control algorithms design. Firstly, to consider occupants� thermal comfort, a reverse thermal model was designed to predict the indoor temperature of thermal zones under different AC control signals. The model was trained with supervised learning using coarse-grained temperature data recorded by smart thermostats; thus, it requires no lengthy configuration as a forward model does. The cost efficiency and plug-and-play feature of the model make it appropriate for SMCB. Secondly, a power disaggregation algorithm is proposed to model the power-outdoor temperature relationship of multiple AC units, using data from a single power meter and thermostats. Finally, algorithms based on mixed integer linear programming (MILP) and reinforcement learning (RL) were devised to coordinate multiple AC units in a building during a DR event. Integrated with the thermal model and AC power consumption model, these algorithms minimize occupants� thermal discomfort while restricting the aggregated AC power consumption below the DR limit. The efficiency of these control algorithms was tested, which demonstrate that they can generate AC control schedule in short notice (5 minutes) ahead of a DR event. Verification and validation of the proposed framework was conducted in both simulation and actual building environments. In addition, though the framework is designed for SMCBs, it can also be applied to large homes with multiple AC units to coordinate. This work is expected to give an insight into the BEM sector, helping the popularization of implementing DR in buildings. The research findings from this dissertation work shows the validity of the proposed algorithms, which can be used in BEM systems and cloud-based smart thermostats to exploit the untapped DR resource in SMCB.
PHD
For power system operation, the demand and supply should be equal at all time. During peak hours, the demand becomes very high. One way to keep the balance is to provide more generation capacity, and thus more expensive and less efficient generators are brought online, which causes higher production cost and more pollution. Instead, an alternative is to encourage the load reduction via demand response (DR): customers reduce load upon receiving a signal sent by the utility company, usually in exchange for some monetary payback. For buildings to participate in DR, an affordable automation system and related control algorithms are needed. This dissertation proposed a cost-effective, self-learning and data-driven framework to facilitate small- and medium-sized commercial buildings or large homes in air-conditioner (AC) units control during DR events. The devised framework requires little human configuration; it learns the building behavior by analyzing the operation data. Two algorithms are proposed to coordinate multiple AC units in a building with two goals: firstly, reducing the total AC power consumption below certain limit, as agreed between the building owners and their utility company. Secondly, minimizing occupants’ thermal discomfort caused by limiting AC operation. The effectiveness of the framework is investigated in this dissertation based on data collected from a real building.

Buildings contribute a significant part to the electricity demand profile and peak demand for the electrical utilities. The addition of renewable energy generation adds additional variability and uncertainty to the power system. Demand side management in the buildings can help improve the demand profile for the utilities by shifting some of the demand from peak to off-peak times. Heating, ventilation and air-conditioning contribute around 45% to the overall demand of a building. This research studies two strategies for reducing the peak as well as shifting some demand from peak to off-peak periods in commercial buildings: 1. Use of gas heat pumps in place of electric heat pumps, and 2. Shifting demand for air conditioning from peak to off-peak by thermal energy storage in chilled water and ice. The first part of this study evaluates the field performance of gas engine-driven heat pumps (GEHP) tested in a commercial building in Florida. Four GEHP units of 8 Tons of Refrigeration (TR) capacity each providing air-conditioning to seven thermal zones in a commercial building, were instrumented for measuring their performance. The operation of these GEHPs was recorded for ten months, analyzed and compared with prior results reported in the literature. The instantaneous COPunit of these systems varied from 0.1 to 1.4 during typical summer week operation. The COP was low because the gas engines for the heat pumps were being used for loads that were much lower than design capacity which resulted in much lower efficiencies than expected. The performance of equivalent electric heat pump was simulated from a building energy model developed to mimic the measured building loads. An economic comparison of GEHPs and conventional electrical heat pumps was done based on the measured and simulated results. The average performance of the GEHP units was estimated to lie between those of EER-9.2 and EER-11.8 systems. The performance of GEHP systems suffers due to lower efficiency at part load operation. The study highlighted the need for optimum system sizing for GEHP/HVAC systems to meet the building load to obtain better performance in buildings. The second part of this study focusses on using chilled water or ice as thermal energy storage for shifting the air conditioning load from peak to off-peak in a commercial building. Thermal energy storage can play a very important role in providing demand-side management for diversifying the utility demand from buildings. Model of a large commercial office building is developed with thermal storage for cooling for peak power shifting. Three variations of the model were developed and analyzed for their performance with 1) ice storage, 2) chilled water storage with mixed storage tank and 3) chilled water storage with stratified tank, using EnergyPlus 8.5 software developed by the US Department of Energy. Operation strategy with tactical control to incorporate peak power schedule was developed using energy management system (EMS). The modeled HVAC system was optimized for minimum cost with the optimal storage capacity and chiller size using JEPlus. Based on the simulation, an optimal storage capacity of 40-45 GJ was estimated for the large office building model along with 40% smaller chiller capacity resulting in higher chiller part-load performance. Additionally, the auxiliary system like pump and condenser were also optimized to smaller capacities and thus resulting in less power demand during operation. The overall annual saving potential was found in the range of 7-10% for cooling electricity use resulting in 10-17% reduction in costs to the consumer. A possible annual peak shifting of 25-78% was found from the simulation results after comparing with the reference models. Adopting TES in commercial buildings and achieving 25% peak shifting could result in a reduction in peak summer demand of 1398 MW in Tampa.

This thesis presents a new method developed to adapt existing hydronic systems in buildings to take advantage of low temperature district heating (LTDH). The work carried out was performed by extensive use of buildings’ energy modelling, validated through recorded data. Two different case studies were investigated and the dynamic heat demand profiles, simulated for each building, were used to evaluate plate radiators connected to single and double string heating loops. The method considered an optimisation procedure, based on supply and return temperatures, to obtain the required logarithmic mean temperature difference (LMTD). The results of the analysis are presented as the average reduction of LMTD over the heating season compared to the base case design conditions. The developed strategy was applied to a Danish single family house from the 1930s. Firstly it was hypothesised a heating system based on double string loop. Two scenarios were investigated based on the assumption of a likely cost reduction in the end users energy bills of 1% per each 1◦C reduction of return and average supply and return temperatures. The results showed possible discounts of 14% and 16% respectively, due to more efficient operation of the radiators. For the case of single loop system, the investigated scenario assumed a cost reduction in the end users energy bill of 1% per each 1◦C lower reduction of average supply and return temperature. Although low return temperatures could not be achieved, the implementation of the method illustrates how to efficiently operate these systems and for the given scenario a possible discount of 5% was quantified. The method was also applied to a UK small scale district heating (DH) network. The analysis began by assessing the buildings of the Estate having double string plate radiator systems. Assuming a likely cost reduction in the end users energy bills of 1% per each 1◦C reduction of return temperature, the optimisation led to obtain a possible discount in the end users energy bills of 14% with a possible yearly average return temperature of 41◦C, compared to the present 55◦C. Moreover, few improvements in the operation of the heat network were proposed. It was assumed to operate the buildings with underfloor heating systems (UFH) with average supply and return temperatures of 40/30◦C, whereas the ones with plate radiators with the optimised temperatures of 81/41◦C. The results shown that an overall average return temperature of 35.6◦C can be achieved operating the heat network as suggested. This corresponds to a decrease in the average return temperature of 18.6◦C compared to the present condition and to a reduction of 10% in the distribution heat losses. Finally, the lower average return temperature achievable would guarantee a better condensation of the flue gases, improving the overall efficiency of the biomass boiler. This was quantified as a possible reduction of fuel consumption of 9% compared to present conditions.

The heating and air-conditioning energy demand of skyscrapers with atria between buildings is explored. Radiation, conduction, convection, and ventilation were evaluated to determine annual heating and cooling energy demands for a 100-building city located in Provo, Utah. Spreadsheets models were developed and calibrated with a computational fluid dynamics model. Three spreadsheet model cases were examined: a baseline no-atrium case, a conditioned atrium case, and an unconditioned atrium case. The energy demands and atrium temperatures were compared between the different cases. The research concludes that atria can be used between buildings to reduce the heating and cooling energy demands. The exposed surface area of the city was reduced by 73.7%. This resulted in a 49.7% reduction in heating and cooling energy consumption for the unconditioned atrium case and a 16.0% reduction in energy consumption for the conditioned atrium case.

This thesis investigated the feasibility of different advanced solar assisted air conditioning systems for a typical medium office building in all eight Australian capital cities. The technical, environmental, and economic performances of each system have been analysed in comparison with the referenced conventional vapour compression cooling system using the whole building energy simulation software EnergyPlus. The research has concluded that solar cooling technology is technically and economically applicable in Australian climates which can contribute to reducing energy consumption and greenhouse gas emissions from the building sector.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The thesis was initiated by a Consulting Engineering Company (KV3) as a research project to investigate various options in which the efficiency and energy utilisation of conventional air conditioning systems may be enhanced by using alternative and renewable energy. Initially, eight options had been identified and through a process of determining the degree of commercialisation the alternative options were reduced to three. These options, referred to as the sustainable cooling alternatives, are active mass cooling, night flushing and roof cooling system. The roof cooling system comprised a roof-pond, roof-spray, pump and storage tank. The roof cooling system was mathematically and experimentally modelled. The roof cooling experiment was performed under a variety of weather conditions with the roof-pond and storage tank temperatures continuously recorded. The experimentally recorded temperatures were compared to the temperatures generated by the theoretical simulation calculations for the same input and weather conditions. Good agreement was found between the mathematical and experimental model. The largest discrepancy found between the simulated temperature and the experimental temperature was in the order of 1 ºC. A one-room building has been assumed to serve as a basis to which the sustainable cooling alternatives could be applied to for theoretical simulation. The one-room building had four façade walls and a flat roof slab. Night flushing, active mass cooling and the roof cooling system were applied to the one-room building such that the room air temperature and space cooling load could theoretically be simulated. The theoretical simulations were also repeated for the case where the roof-pond and roof-spray were applied as standalone systems to the one-room building. The theoretical simulation calculations were performed for typical summer weather conditions of Stellenbosch, South Africa. Under base case conditions and for a room thermostat setting of 22 ºC the peak cooling load of the one-room building was 74.73 W/m². With the application of night flushing between the hours of 24:00 and 07:00, the room cooling load was reduced by 5.2% by providing 3.9 W/m² of cooling and reducing the peak room temperature by 1.4 ºC. The active mass cooling system was modelled by supplying water at a constant supply temperature of 15 ºC to a pipe network embedded in the roof slab of the one-room building. The sea may typically be considered as a cold water source for buildings situated at the coast. The active mass cooling system reduced the peak cooling load of the one-room building by 50% by providing 37.2 W/m² of cooling and reducing the peak room temperature by 6.7 ºC. When the roof-spray and roof-pond systems were applied as standalone systems to the oneroom building, the peak cooling load of the one-room building could be reduced by 30% and 51% respectively. This is equivalent to 22.3 W/m² of peak cooling by the roof-spray and 38 W/m² of peak cooling by the roof-pond. The roof-spray reduced the peak room temperature by 3.71 ºC while the roof-pond reduced the peak room temperature by 5.9 ºC. Applying the roof cooling system to the one-room building produced 46 W/m² of peak cooling which resulted in a 61.1% reduction in peak cooling load. The roof cooling system reduced the peak temperature by 8 ºC. By comparing the sustainable cooling alternatives, the roof cooling system showed to be the most effective in reducing the one-room building peak cooling load. Over a 24 hour period the roof cooling system reduced the net heat entry to the one-room building by 57.3%. In a further attempt to reduce the peak cooling load, the sustainable cooling alternatives were applied in combinations to the one-room building. The combination of night flushing and roof-spray reduced the peak cooling load by 36% while a combination of night flushing and active mass cooling reduced the peak cooling load by 55%. Combining night flushing with the roof-pond also yielded a 55% peak cooling load reduction. The combination of roofpond, active mass cooling and night flushing provided 51 W/m² of cooling which corresponded to a 68% reduction in peak cooling load. Utilising the sustainable cooling alternatives in a combination in the one-room building gave improved results when compared to the case where the sustainable cooling alternatives were employed as standalone systems. It is illustrated by means of a sensitivity analysis that the ability of the roof cooling system to produce cool water is largely influenced by ambient conditions, droplet diameter and roofspray rate. Under clear sky conditions, an ambient temperature of 15 ºC, relative humidity of 80%, a roof-spray rate of 0.02 kg/sm² and a roof-pond water level of 100mm, water could be cooled at a rate of 113 W/m². The roof-spray energy contributed to 28 W/m² whilst the night sky radiation was responsible for 85 W/m² of the water cooling. It must however be noted that the water of the roof cooling system can never be reduced to a temperature that is lower than the ambient dew point temperature.
AFRIKAANSE OPSOMMING: Die tesis is geïnisieer deur ‘n Raadgewende Ingenieurs Maatskappy (KV3) as a navorsingsprojek om verskeie opsies te ondersoek waarmee die effektiwiteit en energie verbruik van konvensionele lugversorgingstelsels verbeter kan word deur middel van alternatiewe en hernubare energie. Agt opsies is oorspronglik geïdentifiseer en deur middel van ‘n proses waarby die graad van kommersialisering van hierdie alternatiewe maniere bepaal is, kon die opsies verminder word tot drie. Hierdie opsies, ook verwys na as die volhoubare verkoelingsalternatiewe, sluit in aktiewe massa verkoeling, dakverkoeling en nagventilasie. Die dakverkoelingstelsel bestaan uit dakwater, ‘n dakspuit, ‘n pomp en ‘n stoortenk. Die dakverkoelingstelsel is wiskundig en eksperimenteel gemodelleer. Die dakverkoelingseksperiment is uitgevoer onder ‘n verskeidenheid van weersomstandighede. Die dakwater asook die stoortenk se water temperatuur is voortdurend aangeteken. Dieselfde weer- en insetkondisies is gebruik vir die simulasie berekening en die temperature van die stoortenk se water en die dakwater is vergelyk met die temperatuurlesings van die eksperimentele werk. Die temperature van die eksperimentele lesings het goed vergelyk met die temperatuur simulasie berekeninge. Die grootste verskil tussen die simulasie en eksperimentele temperatuur was in die orde grootte van 1 ºC. ‘n Een-kamer gebou is aangeneem om as basis te dien waarop die volhoubare verkoelingsalternatiewe aangewend kon word vir teoretiese simulasie. Die een-kamer gebou het uit vier buite mure en ‘n horisontale beton dak bestaan. Nag ventilasie, aktiewe massa verkoeling en die dakverkoelingstelsel is toegepas op die een-kamer gebou en die kamer se verkoelingslas asook die kamer se lugtempertuur is teoreties gesimuleer. Die teoretiese simulasies is ook herhaal vir die geval waar die dakwater and dakspuitstelsel apart aangewend is op die een-kamer gebou. Die teoretiese simulasie berekeninge is uitgevoer vir tipiese somer weersomstandighede vir Stellenbosch, Suid Afrika. Onder basisgeval omstandighede, waar die een-kamer gebou gesimuleer is, sonder enige volhoubare verkoelingsalternatiewe en ‘n termostaat verstelling van 22 ºC, is die piek verkoelingslas bereken as 74.73 W/m². Met die toepassing van nagventilasie tussen die ure 24:00 en 07:00 was die piekverkoelingslas van die kamer verminder met 5.2% deur 3.9 W/m² se verkoeling te verskaf en die piekkamer temperatuur te verminder met 1.4 ºC. Aktiewe massa verkoeling is gesimuleer deur water teen ‘n konstante temperatuur van 15 ºC te verskaf aan ‘n pypnetwerk, geïnstalleer in the beton dak, van die een-kamer gebou. Geboue geleë aan die kus kan tipies seewater oorweeg as ‘n bron van koue water. Aktiewe massa verkoeling het die piekverkoelingslas van die een-kamer gebou verminder met 50% deur 37.2 W/m² se verkoeling te verskaf en die piekkamer temperatuur te verminder met 6.7 ºC. Wanneer die dakspuit- en dakwaterstelsel aangewend is op die een-kamer gebou as enkel staande stelsels, is die piekverkoelingslas verminder met 30% en 51% onderskeidelik. Dit is ekwivalent aan 22.3 W/m² se verkoeling vir die dakspuitstelsel en 38 W/m² se verkoeling vir die dakwaterstelsel. Die dakspuitstelsel het die piekkamer temperatuur verminder met 3.71 ºC terwyl die dakwaterstelsel ‘n 5.9 ºC verlaging in piekkamer temperatuur tot gevolg gehad het. Die dakverkoelingstelsel het 46 W/m² se piekverkoeling verskaf wat ‘n 61.1% vermindering in piekverkoelingslas tot gevolg gehad het. Die ooreenstemmende piek temperatuur vermindering is 8 ºC. Deur die verskeie volhoubare verkoelingsalternatiewe met mekaar te vergelyk, word getoon dat die dakverkoelingstelsel die mees effektiefste manier is om die een- kamer se piekverkoelingslas te verminder. Oor ‘n tydperk van 24 uur het die dakverkoelingstelsel die totale energievloei na die een-kamer gebou met 57.3% verminder. In ‘n verdere poging om die piekverkoelingslas te verminder, is die volhoubare verkoelingsalternatiewe toegepas in kombinasies op die een-kamer gebou. Die kombinasie van nagventilasie met die dakspuitstelsel het die piekverkoelingslas met 36% verminder, terwyl ‘n kombinasie van nagventilasie en aktiewe massa verkoeling ‘n 55% vermindering in piekverkoelingslas tot gevolg gehad het. Die kombinasie van dakwater en nagventilasie het ook ‘n piekverkoelingslas vermindering van 55% teweeggebring. Die kombinasie van dakwater, aktiewe massa verkoeling en nagventilasie het 51 W/m² se verkoeling veskaf, wat ooreenstem met ‘n 68% vermindering in piekverkoelingslas. Deur die volhoubare verkoelingsalternatiewe in kombinasies toe te pas op die een-kamer gebou, kon beter resultate verkry word toe dit vergelyk is met die geval waar die volhoubare verkoelingsalternatiewe as enkelstaande stelsels toegepas is. Dit is geïllustreer deur middel van ‘n sensitiwiteitsanalise dat die vermoë van die dakverkoelingstelsel om koue water te produseer, beïnvloed word deur buitelug kondisies, waterdruppel deursnee en dakspuit massa vloeitempo. Onder die oop hemelruimteomstandighede, ‘n buitelug temperatuur van 15 ºC, ‘n relatiewe humiditeit van 80%, ‘n dakspuit massa vloeitempo van 0.02 kg/sm² en dakwatervlak van 100 mm, kon water verkoel word teen ‘n tempo van 113 W/m². Die dakspuit gedeelte het 28 W/m² bygedra terwyl die nagruim radiasie sowat 85 W/m² se verkoeling verskaf het. Daar moet egter kennis geneem word dat die water temperatuur van die dakverkoelingstelsel nooit verminder kan word tot onder die buitelug doupunttemperatuur nie.