Published Date: 2021-08-01, Sunday
Dr. Rabindra Pokhrel's virtual presentation of his PhD Research Outcome
Monday, August 2 · 2:00 – 3:00 pm
Google Meet joining info
Video call link: https://meet.google.com/hjq-qwuo-ihj
On the energy sustainability of active and passive building integrated technologies in the context of a changing climate for tropical coastal cities
Caribbean Sea surface temperatures have been rising at an alarming rate of 0.020C/year. The effect of rising sea surface temperatures is reflected in an increase in 2m air temperature over the Caribbean. The rise in extreme temperatures increases human discomfort and energy demands for air conditioning (AC) putting both the population and energy infrastructure at higher risk of vulnerability. This vulnerability is amplified in compact cities where anthropogenic heat removal from the built environment further increases the temperature of the urban canyon with feedback on human comfort and energy demands. Although there has been prior work reported on mitigating energy demands due to rising temperatures, these studies are focused mostly on the building scale, where the two-way interaction between the urban climate and buildings is missing. Thus, the effect of energy mitigating technologies on the microclimate and energy demand on a scale of a city is still unknown, so is the assessment of their mitigating impacts under future climate conditions. Such an understanding is important in developing next-generation sustainable active and passive building integrated energy technologies that improve human comfort, mitigate peak demands, and produces power on-site amid a changing climate. This dissertation describes the development of a new methodology for quantifying human discomfort index and peak air conditioning demands for different passive and active building-integrated technologies. The specific goal of the study is to identify different technological scenarios that promote environmental and energy sustainability of the urban environment of tropical coastal cities with San Juan metropolitan area (SJMA), Puerto Rico as a case study for a typical coastal urban city. Short term simulation reflects the peak AC demand reduction potential in increasing order for titled Photovoltaic (TPV) roof, white roof, target temperature (thermostat set points), and efficient HVAC equipment. The role of potential scenarios for improving the overall human comfort, reducing urban heat island, and air conditioning demands are explored for present and future climate change scenarios. Results for SJMA shows that the daily maximum temperatures (in 0C) for the high-density region have mean at 31.2, 32.2, and 33.2 for 2010, 2050, and 2100, whereas the energy mitigation measures reduce it to 31 and 31.8 for 2050 and 2100, respectively. A consequence of the rise in maximum temperature increases AC demand by 12.5% and 25% for mid and end of 21st century respectively as compared to the historic period of 2010. The AC demand reduction potential with energy mitigation measures (a combination of the white roof, tilted PV, and efficient HVAC equipment) reduces the demand by 13% and 1.5% for 2050 and 2100 respectively, compared to the same historic period. The impact of climate change results in the decrease of the sea and land breeze and the decrease is more pronounced for 2050 than 2100 with energy mitigation measures; mainly due to low-temperature gradients between land and sea with mitigation measures for 2050. The mitigation measures have the potential of reducing the UHI intensities to 10C (from 3.50C) and 0.50C (from 3.50C) for the 2050 and 2100 climate periods respectively. The heat index is projected to increase for the mid and end century however, there is no change in heat index for energy mitigation measures. The results of this research have generated new knowledge to support the decisions of policymakers on implementing different technologies for coastal tropical cities. Furthermore, the methodology developed could be used to study the role of different energy mitigation measures for current and future climate for any other tropical coastal city.