Modeling, control and performance evaluation of bottom-up motorized shade

Integration of daylighting into buildings using motorized interior shades is challenging. If it is done properly, reduction of energy for artificial lighting and eventually building cooling demand can be achieved, while providing an improved visual and thermal office environment, beneficial for the occupants' health and performance. If it is poorly done, it can lead to increased cooling demand due to overheating, thermal discomfort and glare problems. In this study, the daylighting and thermal performance of "bottom-up" shades was presented. The bottom-up is a motorized roller shade that operates in reverse of a conventional roller shade (opens from top to bottom), so as to cover the bottom part of the window, providing privacy to the occupants, while allowing daylight to enter from the top section. A daylighting simulation model, validated with experimental results, was developed in order to establish correlations between the shade position, outdoor illuminance and work plane illuminance for different outdoor conditions as well as to allow a sensitivity analysis of the impact of shade optical properties on the results. Moreover, the model was used to compare "bottom-up" shades with conventional roller shades. The results showed that the Daylight Autonomy (DA) for the bottom-up is 8%-58% higher than the DA for a conventional roller shade, with a difference of 46% at the back part of the room, away from the façade, where the use of artificial lighting is usually more needed, proving the advantage of bottom-up shade versus conventional roller shades, by allowing the natural light to enter from the top section of the façade deep into the room. Thermal experiments were conducted to examine the possible advantages of the use of a bottom-up shade's "sealed" cavity, showing increase of the effective thermal resistance of the fenestration, compared with no shades and with conventional roller shades. Finally, a methodology is proposed for the development of a control algorithm for a bottom-up shade, applicable for any location and orientation

Modelling, Design and Experimental Study of Semi-Transparent Photovoltaic Windows for Commercial Building Applications

As the building sector is moving to net-zero energy building performance targets and beyond, the use of building integrated solar systems becomes essential. Semi-transparent photovoltaic (STPV) window technologies are expected to play a key role in on-site electricity generation of new and retrofitted high-performance commercial and institutional buildings. In most commercial and high-rise residential buildings where reducing the costs of cooling energy is important, STPV windows can be used as integrated strategy to reduce solar heat gains and generate solar electricity while still providing adequate daylight and view to the outdoors. The research presented on this thesis is based on the conviction that window technologies should be considered as an integral part of a broad strategy of energy-conserving, energy-efficient building design. The main objective of this work is to provide a systematic study of STPV windows through experimental work and simulations that will allow these technologies to become ubiquitous on buildings in the near future. The end goal is to transform buildings from energy consumers to energy producers without compromising on occupancy comfort. Hence, all performance characteristics (e.g., electrical, thermal and daylighting) should be studied and quantified individually and in combination in order to capture the impact such technologies have on the building energy performance and occupancy comfort. In this work, design concepts of windows integrating STPV technologies are developed, modelled and studied in typical perimeter zones. The thermal and electrical performance of four crystalline Si-based prototype STPV windows was studied experimentally. Specially designed prototypes were mounted in a calibrated hot-box calorimeter apparatus developed for this study. The apparatus is placed inside a two-storey high environmental chamber with a solar simulator (SSEC) and exposed to emulated sunlight produced by a continuous solar simulator. The SSEC facility allows tests to be performed under fully controlled and repeatable conditions (temperature and irradiance). Operating cell temperatures of up to 80.5°C were observed under 1000 W/sq.m irradiation, still air and ambient air temperature of 21°C. An experimental procedure for the determination of Solar Heat Gain Coefficient (SHGC) for STPV windows is also developed. It was found that the electricity generation from the STPV windows can result in up to 23% reduction of SHGC in comparison to a heat absorbing (e.g., tinted or fritted glass) window with the same optical and thermal properties. In addition, the performance data generated was used to verify thermal-electrical performance models for the prediction of cell operating temperatures and solar energy yield. Low-order thermal models for various STPV window assemblies were developed. Using typical meteorological weather data as inputs, the thermal models could predict the operating cell temperatures of an assembly (e.g., double glazed low-e argon window with integrated photovoltaics) within +/- 5°C, resulting in less than +/- 3% error in the annual solar energy yield. A general simulation methodology was developed integrating thermal, electrical and daylighting performance modelling. The methodology was applied to evaluate the potential benefits of various STPV façade designs in cooling-dominated commercial building applications under continental climate. The simulations revealed that the selection of the ideal STPV optical properties is sensitive on the daylight and lighting controls applied in the building, and photovoltaic cell technology utilized (crystalline Si-based spaced cells, a-Si “see-through” and fully transparent organic thin film technologies were examined). In regards to design of a building façade, it was shown that the three-section design concept integrating Si-based spaced PV cells on the upper section of the façade (daylight section) and “see-through” thin PV film on the middle section (view section) has the potential to maximize daylight utilization and view to the outdoors while minimizing the possibility for glare to occur and producing an optimal amount of solar electricity

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

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

Experimental comparison on the energy performance of semitransparent PV facades under continental climate

Semi-Transparent Photovoltaic panels (STPV) have become an important element in the building integration of photovoltaic panels (BIPV). STPV panels can be integrated on double skin facades (DSF) and insulating glazing units (IGU) acting as their exterior layer, generating electricity, controlling the solar heat gains and utilizing daylight. In addition, a mechanically ventilated DSF integrating STPV panels (DSF-PV), can cool down the PV panels, increase their efficiency but also use the preheated air to enhance the thermal efficiency of the mechanical system connected to the DSF-PV. Two virtually identical STPV are integrated on a DSF-PV and a IGU-PV respectively and their electrical performance is evaluated experimentally. Under the same exterior and interior conditions, it is found that the DSF-PV has a 3% greater electrical performance than the IGU-PV and if the cavity of the DSF-PV is selectively ventilated, the DSF-PV can generate more than 9% of electric power than the IGU-PV

Precise Monitoring of Lettuce Functional Responses to Minimal Nutrient Supplementation Identifies Aquaponic System’s Nutrient Limitations and Their Time-Course

In aquaponics, a closed-loop system which combines fish and crop production, essential nutrients for plant growth are often at sub-optimal concentrations. The aim of the present study was to identify system limitations and thoroughly examine the integrated response of its components to minimal external inputs, notably crop’s functional parameters, fish performance, and microorganism profile. Lettuce and red tilapia were co-cultivated under only Fe and Fe with K supplementation and their performance was evaluated against the control of no nutrient addition. Photosynthesis, the photosynthetic apparatus state, and efficiency, pigments, leaf elemental composition, and antioxidant activity of lettuce were monitored throughout the growth period, along with several parameters related to water quality, fish growth, plant productivity and bacterial community composition. Nutrient deficiency in control plants severely impacted gas exchange, PSII efficiency, and chlorophyll a content, from day 14 of the experiment, causing a significant increase in dissipation energy and signs of photoinhibition. Fe+K input resulted in 50% and two-fold increase in lettuce production compared with Fe and control groups respectively. Nutrient supplementation resulted in higher specific growth rate of tilapias, but did not affect root microbiota which was distinct from the water bacterial community. Collectively, the results emphasize the importance of monitoring crop’s functional responses for identifying the system’s limitations and designing effective nutrient management to sustain the reduced environmental footprint of aquaponics

Precise Monitoring of Lettuce Functional Responses to Minimal Nutrient Supplementation Identifies Aquaponic System’s Nutrient Limitations and Their Time-Course

In aquaponics, a closed-loop system which combines fish and crop production, essential nutrients for plant growth are often at sub-optimal concentrations. The aim of the present study was to identify system limitations and thoroughly examine the integrated response of its components to minimal external inputs, notably crop’s functional parameters, fish performance, and microorganism profile. Lettuce and red tilapia were co-cultivated under only Fe and Fe with K supplementation and their performance was evaluated against the control of no nutrient addition. Photosynthesis, the photosynthetic apparatus state, and efficiency, pigments, leaf elemental composition, and antioxidant activity of lettuce were monitored throughout the growth period, along with several parameters related to water quality, fish growth, plant productivity and bacterial community composition. Nutrient deficiency in control plants severely impacted gas exchange, PSII efficiency, and chlorophyll a content, from day 14 of the experiment, causing a significant increase in dissipation energy and signs of photoinhibition. Fe+K input resulted in 50% and two-fold increase in lettuce production compared with Fe and control groups respectively. Nutrient supplementation resulted in higher specific growth rate of tilapias, but did not affect root microbiota which was distinct from the water bacterial community. Collectively, the results emphasize the importance of monitoring crop’s functional responses for identifying the system’s limitations and designing effective nutrient management to sustain the reduced environmental footprint of aquaponics

Component-based SHGC determination of BIPV glazing for product comparison

Publisher Copyright: © 2024 The Author(s)Building-integrated photovoltaic (BIPV) systems are intrinsically designed to generate electricity and to provide at least one building-related function. When BIPV modules act as glazing products in windows, skylights or curtain walls, their ability to control the transmission of solar energy into the building must be characterised by a Solar Heat Gain Coefficient (SHGC) or g value (also known as Total Solar Energy Transmittance – TSET – or “solar factor”). For the comparison of BIPV glazing products consisting of one PV laminate and possibly further, conventional glazing layers separated by gas-filled cavities, the procedures documented in international standards for architectural glazing (e.g. ISO 9050 and EN 410) form a suitable starting point. Easily implemented modifications to these procedures are proposed to take both optical inhomogeneity (if relevant) and extraction of electricity from BIPV glazing units into account. Geometrically complex glazing and shading devices, and light-scattering glazing layers, are outside the scope of the proposed methodology; SHGC determination for obliquely incident solar radiation is also excluded. For these cases, the experimental calorimetric approach documented in [ISO 19467:2017; ISO 19467-2:2021] is recommended. The paper also presents results and conclusions from an implementation exercise and sensitivity study carried out by participants of the IEA-PVPS Task 15 on BIPV. The cell coverage ratio in the PV laminate, the thermal resistance offered by the glazing configuration, the choice of boundary conditions and the effect of extracting electricity were all identified as parameters which significantly affect the SHGC value determined for a given type of BIPV glazing. A practicable approach to accommodate the great variety of dimensions typical for BIPV glazing is also proposed. These findings should pave the way for modifying the existing component-based standards for architectural glazing to take the specific features of BIPV glazing into account.Peer reviewe