Master of Science in Building Services Engineering

Permanent URI for this collectionhttp://192.248.9.226/handle/123/12432

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Browsing Master of Science in Building Services Engineering by Author "Attalage, R"

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    Electrical energy saving potential in Sri Lanka office buildings : application to office buildings in Colombo
    Priyantha, LHWKS; Attalage, R
    This research study is focused on the applications to find out the potential cost effective energy saving measures (ESMs) to make projection of EUI (Energy Unit Intensity) values in kWh/m2.year for high rise office buildings in Colombo, Sri Lanka, as it is a widely accepted fact that energy efficient building design measures and techniques are application specific. Therefore, the objectives of this thesis include detailed study in relation to office building energy efficient measures (EEMs) and also study for office building energy saving potential using established Baseline Building parameters. This helps to quantify ‘office buildings energy saving potential’ and make projection of building energy consumption savings for new office buildings. This also helps to find out the potential energy saving measures to make projection of EUI values for office buildings in Colombo, Sri Lanka. The results of this research are based on two selected office building applications in Colombo. The building categories subject to this research are one high-rise office building (height around 100m) and one medium-rise office building (height around 30m) in Colombo. Life cycle analysis is done using the present tariff structure of the Ceylon Electricity Board. In most of the projects, the building sites are selected before the involvement of the design team. Also, within the limited site area, the building is orientated and the outer appearance of the building also finalized in order to maximize the useable capacity and aesthetics. Therefore, due to the above project constraints, some ESMs for building form such as aspect ratio of the building, orientation (reduced East-West faced windows) and WWR (window to wall ratios) are not considered in investigation. The analyzing of the potential ESMs for the selected office buildings are limited to the following energy saving measures due to the project specific limitation mentioned above, current industry practices, modeling software analysis limitations, owners of the buildings planning to rent out the spaces to outside tenants, time frame limitation of this study, viz., Selective glazing for windows, Perimeter circulation space, Open office space at perimeter, Daylighting through windows, Energy efficient lamps and ballasts, Lighting controls and High Efficiency cooling equipment (i.e. efficient chillers). TRACE 700 computer simulation software is used for modeling the buildings as it is a detailed simulation tool that computes building energy use based on the interactions between climate, building form and fabric, internal gains, HVAC systems and day lighting integration. It has been found that incorporation of cost effective energy saving measures (ESMs) for high-rise office buildings in Colombo, Sri Lanka have greater potential to reduce annual electrical energy consumption by minimum 20 percent in comparison with a Baseline Building and it can also establish better EUI values for high-rise office buildings in Colombo, Sri Lanka. Based on this study, it has been established that the EUI value for the high-rise office building in Colombo is 124 kWh/m2.year and EUI value for the medium-rise office building in Colombo is 83 kWh/m2.year. Further it has been found that the payback periods for selected cost effective ESMs are between 2.3 and 3.8 years under Ceylon Electricity Board (CEB) present tariff structure (General Purpose tariff). It is recommended that further research be carried out in this area for both computer modeling and data collection from existing office buildings in Sri Lanka to establish a better and more precise EUI values and higher annual energy saving percentage for office buildings in Sri Lanka, as this study is limited to few ESMs and computer simulation has been done for only two office building applications.
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    Potential of using variable air volume systems against constant air volume systems for medium size office buildings
    Herath, HMSC; Attalage, R
    It is a popular fact among HVAC designers that variable air volume (VAV) systems are energy efficient than more common constant air volume systems. Despite that information, when comes to the selection stage of the most suitable air side system for the project, the designers falter to suggest a VAV system to the client with the higher installation cost yielded by the VAV system in his mind. It is nice if he has the luxury finding the pay back of the VAV system after modelling the building and doing a simulation. But, in reality it is a time consuming and tedious task in a busy schedule. It will be immensely helpful if the HVAC designer can decide whether to go for VAV or Constant Air volume (CAV) by just a careful study on some straight forward facts of the building. Therefore, this research is focused on developing a guideline in to decide whether to go for VAV or CAV for a midrise office building. It was done with the help of TRACE 700 energy simulation software. Few sample buildings are modelled with TRACE 700 in few orientations and a comparison was done taking the CAV system as base design and VAV as alternative. Life cycle analysis is done using the present tariff structures of Ceylon Electricity Board. The results of this research are based on two defined parameters as solar gain factor (SGF) and occupancy diversity factor (ODF). SGF is defined as ratio of solar gain to total cooling load of the building which can be obtained by basic cooling load calculation. ODF is a measure of average occupancy variation of the building. Lower the ODF value means higher the occupancy variation. The building category underwent to this research is mid-rise office buildings (i.e. height between 18m – 30m) and the ODF value for those buildings are between 64% and 80%. For a highly varied occupancy schedule, ODF is 64% and for a uniform occupancy schedule, it is 80%. For those ODF value range, the VAV benefited SGF value range is identified as 11.9-13.4 for a payback period of five years. That means, for a mid-rise office building, VAV system is benefitted for a SGF value range of 11.9 – 13.4. If the SGF is lower than 11.9 in a mid-rise office building, VAV systems are not economical when considered for a payback period of five years or less. For any SGF value in above range, the life cycle payback period can be determined using above linear relationship between SGF and life cycle payback period for a selected ODF value between 64% and 80%. For any exception with ODF values higher than 80%, a complete building simulation should be carried out to determine the required SGF value for that building. Otherwise, the investment for VAV will not be paid back within reasonable time (within five years as considered in this study). On the other hand, for a building with lower ODF than 64%, the investment on VAV is worth even in a SGF value lower than 11.9. Further studies should be carried out for the situations out of those ranges. The significance of some non-quantitative benefits of VAV systems is also highlighted.