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

ABSTRACT 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

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

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

Double skin façades integrating photovoltaics and active shadings: a case study for different climates

In this paper the energy potential of an innovative Double Skin Façade integrating Photovoltaics (DSF-P) for different weather conditions is investigated. The proposed system consists of semi-transparent and opaque PV modules integrated in the exterior skin of the façade and active shading devices implemented within the cavity. The innovative single or multi–story proposed DSF can co-generate solar electricity and thermal energy (for space heating or other building applications). In order to effectively cool down the photovoltaics and increase their electrical efficiency, the buoyancy-driven air flow within the cavity may be assisted by a fan (natural / hybrid ventilation). Active roller blinds are taken into account to regulate heating and cooling loads while controlling the daylight in the corresponding adjacent indoor spaces. With the aim to simulate the system performance, the temperature distribution and the airflow in the DSF, a mathematical model was developed. It is also capable to predict the energy flow, as well as the active and passive effects of the DSF-P on the energy consumption of the adjacent perimeter zones. The simulation model is based on a detailed transient finite difference thermal network, including accurate algorithms for the calculation of the heat transfer phenomena taking place within the DSF-P. The model, also allows performing parametric and sensitivity analyses, useful for pre-feasibility studies at the design phase of new buildings or for retrofit projects implementing the proposed DSF-P. In this paper, in order to determine the values of critical design and operating parameters that minimize the overall energy consumptions, a parametric analysis is carried out. Thus, a case study related to a high-rise office building located in diverse climate zones is presented. Simulation results show the effects due to some crucial DSF-P design and operation parameters on the energy demand of the adjacent zones, and the effectiveness of the proposed system to reach the goal of net zero energy building

On the relation between the energy and social characteristics of the residential sector

Social, financial, energy and technical data from about 1110 households have been collected during 2004 in the major Athens area. The sample has been divided in seven income groups and a detailed analysis has been performed. Important conclusions have been drawn regarding the quality of households, the operational conditions and the energy spent per income group. Low income people are more likely to be living in old buildings with poor envelope conditions. The cost per person and unit area is much higher for the low income group for both heating and electricity. Fuel poverty is quite high, especially when the actual oil prices are considered. © 2006 Elsevier B.V. All rights reserved

Comfort considerations in Net ZEBs: Theory and design

This chapter examines thermal, visual, and acoustic comfort, and indoor air quality (IAQ). It identifies and quantifies major sources of comfort. IAQ is a measure of the healthiness and comfort of air in buildings. The three main methods to ensure good IAQ are: removal or reduction of source of contaminants, ventilation, or filtration of contaminants. The elements of indoor environmental quality are critical to the success of Net-zero energy buildings (Net ZEBs). While indoor conditions were traditionally viewed as being passively endured by occupants, it is now widely accepted that occupants actively adapt their environment and themselves to improve comfort. Because these adaptations may have a significant effect on energy use, comfort and energy are tightly linked. As such, maintaining comfort through careful building design and operation should be considered throughout the building life cycle