Adinugroho, Teguh P.
(2021)
Thermal and energy performance of innovative prismatic building forms.
PhD thesis, University of Nottingham.
Abstract
Already built prismatic buildings show that such forms have an appealing look and past studies have proven that it helps to save energy. Segmentation and inclination are two features exist in prismatic building forms, but the impact from each of them are not yet fully understand, since past studies were more centered to downward inclined wall – also known as self-shading – or just studied one sample of prismatic building as a whole. Thus, a study using diverse prismatic forms tested in different conditions is needed to fill the gap about providing a fundamental understanding to architects regarding the impact of segmentation and inclination to thermal and energy performance. Insights from the use of segmentation and inclination associated with thermal and energy saving performance are expected to help green building project since the early design stage, even before the energy simulation, and to diminish greenhouse gases.
The investigation used EnergyPlus version 8.7.0 to conduct simulations in different latitudes and various design options. Preliminary studies were carried out so the method can be evaluated and revised before the simulation’s full running. In the final, the method utilised 33 prismatic models with a gradual change in the segmentation and inclination. Testing multiple cases with gradually changed models is a key for the investigation, which can only be efficiently carried out by simulation. To ensure performance from the geometry, the research set constant on other simulation parameters, equalised the models’ volume, and used relative compactness ratio (RC). The analysis considered favourable or propitious models by the peak design load and annual electricity consumption over the reference models. It used exhaustive graphs and tables to compare and correlate the different variables.
The research found that help from segmentation is universal in the different tests. Segmentation lowers heating-cooling load and annual electricity consumption from three segments (triangle; N3) to eight segments (octagon; N8). The condition was analysed because with more segmentation the models get more compact and makes favourable solar exposure. It is evident in the simulation in different latitudes and simulation with various design options.
Meanwhile, the inclination is sensitive to different locations and susceptible to various design options. With the sensitivity, inclination prone to make a less energy-efficient building at 0° and 30° latitude locations. In these two latitude locations, a model with quarter lower-part-inclined (Nx-BQI) is the most favourable model in both latitude locations, while over 70% other models are unfavourable. At 60° latitude locations, a model with half upper-part-inclined (Nx-TI) is the most promising, with more than 60% of other models also emerged as favourable. The opposite condition in 30° and 60° latitude was analysed because of the climate and solar angle relative to the location.
Based on each latitude's recommended performance variables, average discrepancy that can be achieved by the propitious/favourable models over the reference cube varies. The discrepancy of cooling load at 0° and 30° locations can get 2.4% by an average, and the average maximum can get 4%. While the energy saving by an average can get 1.3% and the average maximum can get 1.9%. The discrepancy of heating load at 30° and 60° locations by an average can get 4.5%, and the average maximum can get 8.1%.; while the energy saving by an average can get 3.3% and the average maximum can get 6.9%. The tested prismatic models give the best favourable impact in reducing thermal load and energy consumption in 60° locations with cold climate.
Sample day analysis attests that the impact of segmentation can be explained by the portion of the envelope exposed to solar radiation. For inclination, fenestration has significant influence by its solar transmittance to the interior over the outside surface heat balance. Moreover, the implementation of various design options related to other passive systems on prismatic models have different behaviour compared to a conventional envelope that should be realised by building designers. The investigation tested window-to-wall ratio (WWR), envelope material, construction layer, and thickness.
The research also tried different indicators to be correlated with the performance of prismatic forms. This study found that RC and surface number can be used for simple indicators describing prismatic building about its energy efficiency. Still, utilisation of both indicators needs to look at the inclination type relative to the location’s latitude/climate and the applied design options.
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