Daylight Performance of Perimeter Office Façades utilizing Semi-transparent Photovoltaic Windows: A Simulation Study

AbstractThis paper presents the potential impact of semi-transparent photovoltaic windows on the daylighting performance of commercial building façades. The performance of three façade configurations is examined, integrating Si-based, opaque spaced cells and transparent thin film technologies. Simulation results suggest that a semi-transparent photovoltaic module with visible effective transmittance of 30%, integrated as the outer glass layer of a double-glazed window, provides sufficient daylight within the perimeter zone throughout the year, with sDA300lx/50%=1 and DGI=5%. Moreover, a three-section façade configuration integrating Si-based spaced PV cells on the upper section and thin film PV on the middle section of the façade has the potential to maximize daylight utilization and the view to the outdoors

Time-lapse photography and image recognition to monitor occupant-controlled shade patterns: Analysis and results

This paper presents a high-level overview of a methodology for analysing window shade use in existing buildings. Time-lapse photography is paired with a robust image recognition algorithm to facilitate assessment of shade use and identify any possible trends. The methodology applied on a highrise building consisting of multiple open plan offices. The analysis showed that the mean shade occlusion and the shade movement rate depend on façade orientation, with the near-south façade having the highest values and the near-north façade having the lowest ones. An average shade use rate of 0.5/day was observed, with the 72% of the shades never adjusted, throughout the period of observation. Copyrigh

Parametric analysis to support the integrated design and performance modeling of net zero energy houses

Building performance models routinely involve tens or hundreds of components or aspects and at least as many parameters to describe them. This results in overwhelming complexity and a tedious process if the designer attempts to perform parametric analysis in an attempt to optimize the design. Traditionally, during design, parameters are selected on a one-at-a-time basis and, occasionally, formal mathematical optimization is applied. However, many subsets of parameters show some level of interaction, to varying degrees, suggesting that the designer should consider manipulating multiple design parameters simultaneously. This paper is divided into two parts. The first part presents a methodology for identifying the critical parameters and two-way parameter interactions. The second part uses these results to identify the appropriate level of modeling resolution. The methodology is applied to a generic model for net-zero or near-net-zero energy houses, which will be used for an early stage design tool. The results show that performance is particularly sensitive to internal gains, window sizes, and temperature setpoints, and they indicate the points at which adding insulation to various surfaces has minimal impact on performance. The most significant parameter interactions are those between major geometrical parameters and operating conditions. Increased modeling resolution for infiltration and building-integrated photovoltaics (BIPV) only provides a modest improvement to simpler models. However, explicit modeling of windows, rather than grouping them into an equivalent area, has a significant impact on predicted performance. This suggests that identifying and implementing the appropriate level of modeling resolution is necessary, and that it should be detailed for some aspects even in the early stage design

Manually-operated window shade patterns in office buildings: A critical review

Despite the significant impact that the position of movable shading devices has on building energy use, peak loads, and visual and thermal comfort, there is a high degree of uncertainty associated with how building occupants actually operate their shades. As a result, unrealistic modeling assumptions in building performance simulation or other design methods may lead to sub-optimal building designs and overestimation or underestimation of cooling loads. In the past 35 years, researchers have published observational studies in order to identify the factors that motivate building occupants to operate shading devices. However, the diversity of the study conditions makes it is difficult to draw universal conclusions that link all contributing factors to shade movement actions. This paper provides a comprehensive and critical review of experimental and study methodologies for manual shade operation in office buildings, their results, and their application to building design and controls. The majority of the many cited factors in office buildings can be categorized into those affecting visual comfort, thermal comfort, privacy, and views. Most office occupants do not operate their shades more than weekly or monthly and they do so based on long-term solar radiation intensity and solar geometry trends rather than reacting to short-term events. They generally operate them to improve visual conditions rather than thermal conditions. Occupants in offices with automatically-controlled heating and cooling tend to be less diligent about using shading devices to improve their comfort

Energy performance, comfort, and lessons learned from an institutional building designed for net zero energy

This paper examines the early performance ofthe Varennes Library, a building designed for net-zero annual energy balance in Varennes, near Montreal, Canada. It produces electricity from a 110.5 kWp building-integrated photovoltaic (BIPV) system where heat is also recovered from a section of the array and used to preheat the outdoor air intake. The building's many architectural and mechanicalfeatures were integrally designed to achieve the net zero energy target over a five-year averaging period with several key decisions made at the early design stage. These include the shape, area, and orientation ofthe roofthat maximizes electricity productionfrom the BIPV (part BIPV/T [building-integrated photovoltaic/thermal with heat recovery]) system and a design layout that promotes daylight penetration and natural ventilation/free coolingduring the cooling season. In thefirstyear after inauguration, an operational energy use intensity (EUI) of 24.8 kBtu/tfy (78.1 kWh/m2y) was achieved and has since been reduced to 22.20 kBtu/fy (70.0 kWh/m2y). Considering renew-ables production, the net-energy use intensity (EUI) is 4.60 kB tu/ fi2y (14.5 kWh/m2y). This is a 95% EUI reduction over the national institutional average and can be further reduced with additional (ongoing) commissioning efforts. Suggested improvements in operation include ensuring the electricity production is optimized and any faults corrected, dimming electric lighting when daylight is sufficient, extending the hours of natural ventilation, and better utilization of the hydronic radiant slab for thermal storage using predictive controls. This paper discusses the process followed in the design of the library, its key features, its early performance, and some of the lessons learned

The relationship between net energy use and the urban density of solar buildings

There is a paradoxical relationship between the density of solar housing and net household energy use. The amount of solar energy available per person decreases as density increases. At the same time, transportation energy, and to some extent, household operating energy decreases. Thus, an interesting question is posed: how does net energy use vary with housing density? This study attempts to provide insight into this question by examining three housing forms: low-density detached homes, medium-density townhouses, and high-density high-rise apartments in Toronto. The three major quantities of energy that are summed for each are building operational energy use, solar energy availability, and personal transportation energy use. Solar energy availability is determined on the basis of an effective annual collector efficiency. The results show that under the base case in which solar panels are applied to conventional homes, the high-density development uses one-third less energy than the low-density one. Improving the efficiency of the homes results in a similar trend. Only when the personal vehicle fleet or solar collectors are made to be extremely efficient does the trend reverse-the low-density development results in lower net energy