Experimental validation and model development for thermal transmittances of porous window screens and horizontal louvred blind systems

Virtually every home in the US has some form of shades, blinds, drapes, or other window attachment, but few have been designed for energy savings. In order to provide a common basis of comparison for thermal performance it is important to have validated simulation tools. This paper outlines a review and validation of the ISO 15099 centre-of-glass thermal transmittance correlations for naturally ventilated cavities through measurement and detailed simulations. The focus is on the impacts of room-side ventilated cavities, such as those found with solar screens and horizontal louvred blinds. The thermal transmittance of these systems is measured experimentally, simulated using computational fluid dynamics analysis, and simulated utilizing simplified correlations from ISO 15099. Correlation coefficients are proposed for the ISO 15099 algorithm that reduces the mean error between measured and simulated heat flux for typical solar screens from 16% to 3.5% and from 13% to 1% for horizontal blinds

Experimental validation for thermal transmittances of window shading systems with perimeter gaps

Virtually all residential and commercial windows in the U.S. have some form of window attachment, but few have been designed for energy savings. ISO 15099 presents a simulation framework to determine thermal performance of window attachments, but the model has not been validated for these products. This paper outlines a review and validation of the ISO 15099 centre-of-glass heat transfer correlations for perimeter gaps (top, bottom, and side) in naturally ventilated cavities through measurement and simulation. The thermal transmittance impact due to dimensional variations of these gaps is measured experimentally, simulated using computational fluid dynamics, and simulated utilizing simplified correlations from ISO 15099. Results show that the ISO 15099 correlations produce a mean error between measured and simulated heat flux of 2.5 ± 7%. These tolerances are similar to those obtained from sealed cavity comparisons and are deemed acceptable within the ISO 15099 framework

Numerical investigation of the energy saving potential of a semi-transparent photovoltaic double-skin facade in a cool-summer Mediterranean climate

202310 bckwAccepted ManuscriptOthersPublic Policy Research Funding Scheme; Hong Kong Construction Industry Council Research Fund; Fundamental Research Funds for the Central Universities; Hong Kong Housing AuthorityPublishedGreen (AAM

Comparative study on the overall energy performance between photovoltaic and Low-E insulated glass units

A novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable