In modern architecture, highly glazed commercial buildings account for considerable amount of energy, specifically in cold and hot climates because of heating, cooling, and lighting energy load demand. Abatement of this high building energy is possible by employing semitransparent photovoltaic (STPV) window which has triple point advantages as they control the admitted solar gain and daylight and generates benign electricity. Integration of internal light shelves (ILS) to this STPV window assists in controlling visual comfort. Thus, this study aims to evaluate the impact of a nonuniform layout of double-glazing (DG) low-e STPV and DG low-E argon-filled clear glass integrated into a fully glazed open-office facade combined with ILS in cardinal orientations under Riyadh, London, Kuala Lumpur, and Algiers climates. Comprehensive energetic and radiance simulations were conducted to evaluate three groups of STPV configurations. The first group replaced the glazing area with amorphous silicon (a-Si) modules with different transparencies; the second and third groups changed only 75% and 50% of the glazing area, respectively, with STPVs integrated with the ILS. The results revealed that the integration of a-Si modules did not meet the visual comfort requirements but obtained the maximum saving in the east-west axis. It was also found that the optimum design on the south-facing facade with the nonuniform facade achieved 50% of STPV10 coverage in clear glazing windows combined with ILS; the energy saving ratios comparing the reference models were 76%, 83%, 65%, and 70% in Riyadh, London, Kuala Lumpur, and Algiers, respectively. Thus, the integration of STPVs with ILS is considered a more efficient way and effective solution to reduce the possibility of glare discomfort.
Currently, the overall energy consumption in the buildings sector is responsible for almost one-third of the energy used worldwide. Heating, cooling, and artificial lighting load demands are the reason for this high consumption. Energy loss and gain both incur in higher order through the transparent building window envelopes [
Recent trend is to employ semitransparent window over fully transparent window to control the entering solar light. Semitransparent photovoltaic (STPV) windows are specially gaining importance as they have ability to abate the energy demand being energy efficient over conventional windows [
The most significant rating indices used for evaluating the thermal performance of an STPV fenestration system are the solar heat gain coefficient (SHGC) and thermal transmission (U-value) [
However, power generation from STPV is strongly correlated with the transmittance level of PV. Lower transmittance generates higher power while stops viewing from interior to exterior while higher transmittance generates lower power and allows viewing. The current practice of STPVs is applied to uniform layouts for the whole window area. Only a few studies have investigated the spatial distribution of glazing types [
A comprehensive numerical parametric simulation of integrated STPVs combined with ILS was conducted based on EnergyPlus and Diva-for-Rhino simulation tools. All STPV configurations were simulated in four diverse climates to analyze the influence of different latitude and climatic conditions on the optimal configuration of the combined systems. The Meteonorm meteorological database corresponding to Riyadh was used for the subtropical desert climate, while the Typical Meteorological Year (TMY) files of London, Algiers, and Kuala Lumpur were used for the marine west coast (temperate) and Mediterranean climates and tropical rainforest, respectively. Among the most important reasons for selecting these cities are the differences in external temperature (either too cold, too hot or average) and the amount of solar radiation that affect the solar panel performance and external illuminance in each zone based on the sky condition. Table
Climatic conditions of different cities used in this study.
Cities (climate) | Latitude | Longitude | Average air temperature in winter and summer (°C) | Annual average solar irradiance (kWh/m2) | Sky condition | External illuminance (klx) |
---|---|---|---|---|---|---|
Riyadh (subtropical desert climate) | 24.43°N | 46.43°E | 14.4–36.1 | 2200 | Clear | 19 to 35 |
London (marine west coast climate) “Cfb” | 51.09°N | 0.11°W | 4.3–17.3 | 1000 | Overcast | 03 to 20 |
Kuala Lumpur (tropical rainforest) “Af” | 03.07°N | 101.33°E | 27.2–28.3 | 1600 | Intermediate | 18 to 23 |
Algiers Mediterranean “Csa” | 36.43°N | 3.15°E | 11.1–25.6 | 1900 | Clear-overcast | 10 to 36 |
An open-plan perimeter office zone was modelled using the Diva-for-Rhino simulation software in cardinal orientations as shown in Figure
3D model of perimeter open-office zone and furniture arrangements in cardinal orientation.
In this study, a total of nine STPV configurations and reference models were examined referring to the level of transmittance (10%, 20%, and 30%) and the height and length of flat internal light shelves. The spatial combination of STPVs, glazing surfaces, and internal light shelves is based on the principle of dividing the facade into upper daylight and the lower part for viewing [
STPV configurations applied in each part of the simulation. (a) Reference model. (b) First Group. (c) Second Group. (d) Third Group.
The chosen STPVs were amorphous silicon (a-Si) types that were obtained from Onyx in Spain and had a range of visible light transmittance (10%, 20%, and 30%), suitable for building residents with an excellent outdoor view. The performance of ordinary a-Si PV thin-film modules becomes distinctly low (less than 5%). As a result, a change between the energy and daylighting performances ought to be affected to maximise the benefits of energy. A better PV module transmittance could result in a decline of energy conversion efficiency as well as an upgrade of the solar heat benefit coefficient. Table
Thermooptical properties of various STPV (10%, 20%, and 30% VLT) and reference glazing models.
Glazing configurations | SHGC (%) | U-value (W/m2K) | External light reflection (%) | Transmittance VLT (%) | Peak power (Wp/m2) |
---|---|---|---|---|---|
Double-glazing low-E argon-filled | 0.65 | 1.1 | 13 | 79 | — |
STPV DG low-E 10% | 0.09 | 1.6 | 7.3 | 40 | |
STPV DG low-E 20% | 0.12 | 1.6 | 7.3 | 34 | |
STPV DG low-E 30% | 0.17 | 1.6 | 7.3 | 28 |
The energy modelling of EnergyPlus makes it possible to simulate the energy production of the STPV system by means of an equivalent one-diode model [
Input electrical parameters of various STPV transparencies.
Parameters of PV | STPV 10% | STPV 20% | STPV 30% |
---|---|---|---|
Efficiency of module (η∘) | |||
Max power (Pmax) | 123 watts | 104 watts | 86 watts |
Max power voltage (Vpm) | 132 V | 132 V | 132 V |
Max power current (Ipm) | 0.93 A | 0.79 A | 0.65 A |
Open circuit voltage | 191 V | 191 V | 191 V |
Short circuit current | 1.15 A | 0.97 A | 0.77 A |
Temperature coefficient of Pmpp | −0.19%/C° | −0.19%/C° | −0.19%/C° |
Temperature coefficient of Voc | −0.28%/C° | −0.28%/C° | −0.28%/C° |
Temperature coefficient of Isc | +0.09%/C° | +0.09%/C° | +0.09%/C° |
On the other hand, an ideal HVAC system is also assumed to supply the required heating or cooling air to the related zone to meet the set point indoor air temperature of 26°C in the summer and 20°C in the winter season based on international standard (ASHRAE 55, ISO 7730), with a heating and cooling coefficient performance of 1. Taking into account that the simulated open-office components are in cardinal orientation, the floor, the ceiling, and the internal walls were adiabatic. The HVAC system was turned on only during the occupancy schedule, which was from 8.00 AM to 5.00 PM.
A flat LED ceiling surface-mounted luminaire with an input power of 17.4 W was installed in regular distances of 1.5 m by 2 m in columns and rows, respectively. This arrangement is for illuminating the whole work plane with a sufficient quantity of light in the case of an absence of daylight based on the lumen method [
The quantitative results derived from the radiance simulation (Diva-for-Rhino program) depend significantly on the successful configuration of the input parameters according to the specification of the STPV and ILS design. The radiance parameters such as materials reflection as depicted in Table
Material reflection coefficient percentage.
Material | Reflection coefficient (%) |
---|---|
Ceiling | 80 |
Floor | 40 |
Wall | 70 |
Furniture | 50 |
Light shelve | 90 |
Radiance parameters used in daylighting simulation.
Radiance parameter | Ambient bounces | Ambient divisions | Ambient sampling | Ambient accuracy | Ambient resolution |
---|---|---|---|---|---|
Value | 7 | 1500 | 100 | 0.1 | 300 |
In this context, the annual climate-based daylight metrics were applied to evaluate the daylighting performance and were compared with the reference model under various sky and external illuminance conditions. The first metric is daylight autonomy (DA), which was evaluated based only on a minimum illuminance level of 300 lux, but this metric alone failed to consider the effect of glare under excessive daylighting [
The performance indicators of visual comfort used in this study.
Criteria | Performance indicator of delighting quantity and quality |
---|---|
UDI | 100 lux < dark area (needs artificial light) |
100 lux–2000 lux (comfortable), at least 50% of the time | |
>2000 lux too bright with thermal discomfort | |
DA | Set up 300 lx |
DGP | 0.35 < imperceptible glare |
0.35–0.40 perceptible glare | |
0.4–0.45 disturbing glare | |
>0.45 intolerable glare |
The impacts of spatial distribution transparencies and integrated ILS on the STPV performance set up in open-office buildings in different climates were numerically investigated in terms of annual net energy consumption. Hereafter, the net energy consists of cooling, heating, and lighting energy minus the energy produced with a-Si solar cells. It is expressed with kWh per year, as presented in Tables
Overall energy consumptions and net energy of different STPV configurations oriented to south and north axis in Riyadh, London, Kuala Lumpur, and Algiers cities.
Southern facade | Northern facade |
---|---|
Overall energy consumptions and net energy of different STPV configurations oriented to east and west axis in Riyadh, London, Kuala Lumpur, and Algiers cities.
Eastern facade | Western facade |
---|---|
On an annual basis, the results revealed that the net energy consumption of all STPV configurations compared to the reference model has a significant reduction, in particular, the cooling load energy, except for the first group of STPV configurations with all transparencies in the south-north axis of London due to the counterproductive effect on the heating load, which almost doubled from 6568 kWh to 7435 kWh for STPV 30% and STPV 10%, respectively. Inversely, the net energy used by the first group was less than other configurations in the east-west axis because of the sharp decline of cooling energy, as depicted in Table
As expected, the integration of STPVs in the southern facade acquired the maximum annual yield, while the eastern facade had the least lighting energy consumption. Nevertheless, the more transmittance glazing integrated into the upper part of the window with ILS obtained a lower lighting energy in the southern facade, as depicted in the third group. The south-north axis consumes more energy than the east-west axis within all climate contexts.
The integration of ILS and STPV (second and third groups) leads to a significant improvement in terms of energy in the south-north axis rather than the east-west axis because of the substantial impact of ILS with high transmittance of clear glass in the upper part of window, which reflected the concentrated solar heat gain and daylight into the back area to reduce both cooling and lighting energy. Consequently, the optimum energy performance of various STPVs combined with ILS configurations achieved with the second group (75% of STPV10 with 0.75 m ILS) in the south-north axis and the first group (STPV10 without ILS) in the east-west axis. The variances of net energy consumption between the optimum and worst configurations in both axes are approximately 73% to 48% in Riyadh, 94% to 30% in London, 64% to 36% in Kuala Lumpur, and 73% to 50% in Algiers, which indicates the importance of balancing the spatial distribution of glazing and the significant role of ILS in the southern facade that directly affects energy savings.
The evaluation of the daylighting performance of various integrated transparencies of STPV a-Si windows combined with ILS scenarios was based on achieving a balance between climate-based daylight metrics (DA300 lux & UDI100 lux-2000 lux thresholds) and DGP for glare comfort. It is important to mention that a-Si windows modules were treated as uniform optical properties. Three effective visible transmittance values of the STPV window modules were simulated: 10%, 20%, and 30%. The minimum value of 10% was selected to ensure a certain minimum view to the outdoors.
The figures in Tables
DA300 lux distribution of fully glazed open office in cardinal orientations (Riyadh).
Reference model | STPV 30% | ||||||
South = 98.5% | East = 93.5% | North = 93.6% | West = 97.9% | South = 12.9% | East = 11.6% | North = 0% | West = 18.3% |
STPV 20% | STPV 10% | ||||||
South = 4% | East = 3% | North = 0% | West = 3% | South = 0% | East = 0% | North = 0% | West = 0% |
STPV 10% 50% | STPV 10% 75% | ||||||
South = 54% | East = 34% | North = 5% | West = 45% | South = 21% | East = 16% | North = 0% | West = 23% |
STPV 20% 50% | STPV 20% 75% | ||||||
South = 55% | East = 35% | North = 6% | West = 46% | South = 26% | East = 18% | North = 0% | West = 27% |
STPV 30% 50% | STPV 30% |
DA300 lux distribution of fully glazed open office in cardinal orientations (London).
Reference model | STPV 30% | ||||||
South = 90% | East = 84% | North = 78% | West = 84% | South = 15% | East = 8% | North = 0% | West = 8% |
STPV 20% | STPV 10% | ||||||
South = 3% | East = 2% | North = 0% | West = 2% | South = 0% | East = 0% | North = 0% | West = 0% |
STPV 10% 50% | STPV10% 75% | ||||||
South = 55% | East = 29% | North = 3% | West = 30% | South = 20% | East = 12% | North = 0% | West = 11% |
STPV 20% 50% | STPV20% 75% | ||||||
South = 57% | East = 30% | North = 4% | West = 31% | South = 24% | East = 14% | North = 0% | West = 14% |
STPV 30% 50% | STPV 30% 75% | ||||||
South = 61% | East = 33% | North = 5% | West = 33% | South = 30% | East = 16% | North = 0% | West = 16% |
DA300 lux distribution of fully glazed open office in cardinal orientations (Kuala Lumpur).
Reference model | STPV 30% | ||||||
South = 98% | East = 99% | North = 98% | West = 96% | South = 2% | East = 8% | North = 0% | West = 5% |
STPV 20% | STPV10% | ||||||
South = 0% | East = 1% | North = 0% | West = 0% | South = 0% | East = 0% | North = 0% | West = 0% |
STPV 10% 50% | STPV 10% 75% | ||||||
South = 51% | East = 62% | North = 47% | West = 50% | South = 0% | East = 9% | North = 0% | West = 4% |
STPV 20% 50% | STPV 20% 75% | ||||||
South = 56% | East = 65% | North = 52% | West = 53% | South = 0% | East = 18% | North = 0% | West = 12% |
STPV 30% 50% | STPV 30% 75% | ||||||
South = 64% | East = 72% | North = 61% | West = 58% | South = 11% | East = 31% | North = 4% | West = 21% |
DA300 lux distribution of fully glazed open office in cardinal orientations (Algiers).
Reference model | STPV 30% | ||||||
South = 97% | East = 95% | North = 92% | West = 94% | South = 16% | East = 11% | North = 0% | West = 8% |
STPV 20% | STPV 10% | ||||||
South = 3% | East = 1% | North = 0% | West = 2% | South = 0% | East = 0% | North = 0% | West = 0% |
STPV 10% 50% | STPV 10% 75% | ||||||
South = 66% | East = 41% | North = 3% | West = 36% | South = 24% | East = 17% | North = 0% | West = 12% |
STPV 20% 50% | STPV20% 75% | ||||||
South = 68% | East = 43% | North = 4% | West = 37% | South = 31% | East = 20% | North = 0% | West = 16% |
STPV 30% 50% | STPV 30% 75% | ||||||
South = 73% | East = 45% | North = 6% | West = 40% | South = 40% | East = 26% | North = 0% | West = 21% |
Tables
UDI thresholds in cardinal orientations under clear sky condition (Riyadh city).
Orientation (Riyadh) | South | East | North | West | South | East | North | West | South | East | North | West |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Configuration (STPV) | UDI <100 | UDI 100–2000 | UDI >2000 | |||||||||
R. model | 0 | 0 | 0 | 0 | 75 | 82 | 99 | 73 | 25 | 18 | 1 | 27 |
STPV 10% | 100 | 100 | 100 | 100 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
STPV 20% | 88 | 89 | 100 | 82 | 12 | 11 | 0 | 18 | 0 | 0 | 0 | 0 |
STPV 30% | 66 | 76 | 96 | 66 | 34 | 24 | 4 | 34 | 0 | 0 | 0 | 0 |
STPV 10% 75% | 32 | 59 | 81 | 47 | 68 | 41 | 19 | 53 | 0 | 0 | 0 | 0 |
STPV 20% 75% | 40 | 62 | 91 | 52 | 60 | 38 | 9 | 48 | 0 | 0 | 0 | 0 |
STPV 30% 75% | 16 | 47 | 59 | 30 | 84 | 53 | 41 | 70 | 0 | 0 | 0 | 0 |
STPV 10% 50% | 6 | 15 | 20 | 9 | 92 | 83 | 80 | 86 | 2 | 2 | 0 | 5 |
STPV 20% 50% | 3 | 12 | 15 | 6 | 95 | 85 | 85 | 89 | 2 | 3 | 0 | 5 |
STPV 30% 50% | 1 | 7 | 8 | 2 | 96 | 89 | 92 | 91 | 3 | 3 | 0 | 6 |
UDI thresholds in cardinal orientations under overcast sky condition (London city).
Orientation (London) | South | East | North | West | South | East | North | West | South | East | North | West |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Configuration (STPV) | UDI <100 | UDI 100–2000 | UDI >2000 | |||||||||
R. model | 2 | 3 | 3 | 2 | 69 | 82 | 96 | 83 | 28 | 15 | 0 | 15 |
STPV 10% | 100 | 100 | 100 | 100 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
STPV 20% | 86 | 92 | 100 | 92 | 14 | 8 | 0 | 8 | 0 | 0 | 0 | 0 |
STPV 30% | 62 | 78 | 97 | 78 | 38 | 22 | 3 | 22 | 0 | 0 | 0 | 0 |
STPV 10% 75% | 37 | 65 | 95 | 64 | 62 | 35 | 5 | 35 | 1 | 0 | 0 | 0 |
STPV 20% 75% | 31 | 59 | 89 | 57 | 69 | 41 | 11 | 42 | 0 | 0 | 0 | 0 |
STPV 30% 75% | 25 | 49 | 73 | 48 | 74 | 51 | 27 | 52 | 1 | 0 | 0 | 0 |
STPV 10% 50% | 12 | 21 | 32 | 21 | 84 | 76 | 68 | 77 | 4 | 3 | 0 | 3 |
STPV 20% 50% | 11 | 19 | 27 | 18 | 85 | 79 | 73 | 80 | 4 | 3 | 0 | 2 |
STPV 30% 50% | 9 | 14 | 20 | 14 | 86 | 83 | 80 | 83 | 5 | 3 | 0 | 0 |
UDI thresholds in cardinal orientations under intermediate sky condition (Kuala Lumpur city).
Orientation (Kuala Lumpur) | South | East | North | West | South | East | North | West | South | East | North | West |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Configuration (STPV) | UDI <100 | UDI 100–2000 | UDI >2000 | |||||||||
R. model | 0 | 0 | 0 | 0 | 85 | 76 | 88 | 82 | 15 | 24 | 12 | 18 |
STPV 10% | 100 | 100 | 100 | 100 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
STPV 20% | 100 | 93 | 100 | 96 | 0 | 7 | 0 | 4 | 0 | 0 | 0 | 0 |
STPV 30% | 71 | 55 | 75 | 70 | 29 | 45 | 25 | 30 | 0 | 0 | 0 | 0 |
STPV 10% 75% | 32 | 25 | 34 | 39 | 68 | 74 | 66 | 61 | 0 | 1 | 0 | 0 |
STPV 20% 75% | 16 | 14 | 19 | 27 | 84 | 85 | 81 | 73 | 0 | 1 | 0 | 0 |
STPV 30% 75% | 8 | 3 | 8 | 15 | 92 | 97 | 92 | 85 | 0 | 0 | 0 | 0 |
STPV 10% 50% | 3 | 2 | 3 | 6 | 97 | 97 | 97 | 94 | 0 | 1 | 0 | 0 |
STPV 20% 50% | 2 | 0 | 2 | 4 | 98 | 99 | 98 | 96 | 0 | 1 | 0 | 0 |
STPV 30% 50% | 1 | 0 | 1 | 2 | 99 | 99 | 99 | 98 | 0 | 1 | 0 | 0 |
UDI thresholds in cardinal orientations under CEI clear sky condition (Algiers city).
Orientation (Algiers) | South | East | North | West | South | East | North | West | South | East | North | West |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Configuration (STPV) | UDI <100 | UDI 100–2000 | UDI >2000 | |||||||||
R. model | 1 | 1 | 1 | 1 | 66 | 78 | 99 | 82 | 33 | 11 | 0 | 17 |
STPV 10% | 100 | 100 | 100 | 100 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
STPV 20% | 85 | 89 | 100 | 92 | 15 | 10 | 0 | 8 | 0 | 1 | 0 | 0 |
STPV 30% | 54 | 69 | 97 | 75 | 46 | 30 | 3 | 25 | 0 | 1 | 0 | 0 |
STPV 10% 75% | 24 | 53 | 94 | 58 | 76 | 47 | 6 | 42 | 0 | 0 | 0 | 0 |
STPV 20% 75% | 15 | 46 | 84 | 50 | 85 | 53 | 16 | 50 | 0 | 1 | 0 | 0 |
STPV 30% 75% | 7 | 30 | 50 | 30 | 93 | 69 | 50 | 70 | 0 | 1 | 0 | 0 |
STPV 10% 50% | 4 | 11 | 13 | 13 | 93 | 87 | 86 | 86 | 3 | 2 | 0 | 1 |
STPV 20% 50% | 3 | 9 | 14 | 10 | 93 | 89 | 86 | 89 | 4 | 2 | 0 | 1 |
STPV 30% 50% | 3 | 5 | 8 | 5 | 93 | 93 | 92 | 93 | 4 | 2 | 0 | 1 |
Glare is one of the most disturbing side effects of lighting. High luminance or extreme luminance differences associated with the visual field cause this effect. Computation of glare indices is done based on equations that can correlate luminance values or luminance distributions relating to the field of view of the observer, with the human glare sensation. Therefore, the DGP metric was employed to evaluate the annual daylight glare of reference models compared to the optimum STPV combined with ILS configurations based on their net energy and climate-based daylight metrics performance in various orientations and climates as shown in the figures included in Table
DGP in cardinal orientation of reference model open-office buildings in different cities.
Reference model | Annual DGP east facade (Riyadh) | Annual DGP south facade (Riyadh) | Annual DGP west facade (Riyadh) |
Optimum model | Annual DGP east facade (Riyadh) | Annual DGP south facade (Riyadh) | Annual DGP west facade (Riyadh) |
Reference model | Annual DGP east facade (London) | Annual DGP south facade (London) | Annual DGP west facade (London) |
Optimum model | Annual DGP east facade (London) | Annual DGP south facade (London) | Annual DGP west facade (London) |
Reference model | Annual DGP east facade (KL) | Annual DGP south facade (KL) | Annual DGP west facade (KL) |
Optimum model | Annual DGP east facade (KL) | Annual DGP south façade (KL) | Annual DGP west façade (KL) |
Reference model | Annual DGP east facade (Algiers) | Annual DGP south facade (Algiers) | Annual DGP west facade (Algiers) |
Optimum model | Annual DGP east facade (Algiers) | Annual DGP south facade (Algiers) | Annual DGP west facade (Algiers) |
Legend | |||
The temporal maps of the occupied hours of the reference model illustrated that the simulated office in tropical climates (low latitudes) has imperceptible glare through the year. This is because the solar altitude, which is higher at midday, caused a remarkable drop in cardinal orientation, especially when adopting ILS. In contrary, the remaining tested climates (medium and high latitudes) show intolerable glare in the east-west axis, which can be explained due to the solar altitude in the winter season being lower, which causes a direct penetration to the office. The integration of optimum configuration eliminates intolerable glare from an imperceptible glare state in the summer season in cardinal orientation due to the usage of ILS that reflects the direct sunlight to the center and back area of the office. Furthermore, it provides a significant improvement of reducing glare states, in particular in southern orientations.
The largest potential of maximum and optimum percentage savings that can be attained by integrating nine STPV glazing combined with and without ILS compared of employing the reference model (see the base model) in cardinal alignments within four different cities can be seen in Table
The maximum and optimum energy saving percentages of STPV combined with ILS configurations in different climates regions.
Configurations | Riyadh city | London city | Kuala Lumpur city | Algiers city | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
South | East | North | West | South | East | North | West | South | East | North | West | South | East | North | West | |
STPV 10% | 0.53 | 0.69 | 0.15 | −0.14 | 0.67 | −0.24 | 0.50 | 0.30 | 0.22 | 0.62 | 0.12 | |||||
STPV 20% | 0.49 | 0.64 | 0.13 | 0.45 | −0.15 | 0.64 | −0.25 | 0.41 | 0.27 | 0.49 | 0.20 | 0.44 | 0.56 | 0.72 | 0.08 | 0.60 |
STPV 30% | 0.46 | 0.63 | 0.11 | 0.40 | −0.10 | 0.72 | −0.23 | 0.35 | 0.24 | 0.45 | 0.18 | 0.36 | 0.52 | 0.59 | 0.06 | 0.53 |
STPV 10% 75% | 0.72 | 0.23 | 0.74 | 0.46 | 0.40 | 0.76 | 0.64 | |||||||||
STPV 20% 75% | 0.83 | 0.63 | 0.20 | 0.89 | 0.77 | 0.76 | 0.51 | 0.70 | 0.43 | 0.66 | 0.37 | 0.83 | 0.71 | 0.64 | 0.59 | |
STPV 30% 75% | 0.78 | 0.55 | 0.70 | 0.18 | 0.83 | 0.68 | 0.75 | 0.44 | 0.67 | 0.36 | 0.63 | 0.32 | 0.75 | 0.52 | 0.63 | 0.52 |
STPV 10% 50% | 0.68 | 0.76 | 0.41 | 0.58 | ||||||||||||
STPV 20% 50% | 0.74 | 0.44 | 0.68 | 0.31 | 0.80 | 0.57 | 0.76 | 0.39 | 0.64 | 0.28 | 0.61 | 0.25 | 0.66 | 0.49 | 0.59 | 0.43 |
STPV 30% 50% | 0.71 | 0.38 | 0.27 | 0.77 | 0.50 | 0.37 | 0.62 | 0.24 | 0.60 | 0.22 | 0.61 | 0.38 | 0.39 | |||
Optimum performance of STPV configurations (maximum energy saving + visual comfort) | ||||||||||||||||
Maximum energy saving of STPV configurations |
A comprehensive investigation was carried out in this study to evaluate the net energy and visual comfort of STPV configurations combined with and without ILS compared to a reference model of an open-office building in different climate regions. The key findings of this study are as follows: In hot regions, the integration of DG-STPV (first group) instead of DG-clear glazing can effectively reduce cooling energy consumption. Conversely, it increases the heating energy in a temperate climate region (London) mainly due to the thermal properties of DG-STPV, especially in south-north axis. The first and second group configurations did not provide sufficient daylight to the office. But the third group configurations meet the visual comfort requirements (DA300 lux, UDI100 lux–2000 lux) and eliminate a significant portion of glare in all climates because of the adoption of ILS that reflects and balances the quantity of illuminance in the centre and back daylit areas. The maximum performance in terms of overall energy is achieved by means of the second group in the south-north axis, with the first group in the east-west axis including all transparencies. As depicted in Table
Optimum STPV and ILS configurations.
Overall, these outcomes give a vision of the correlation between the net energy visual comforts related to the spatial distribution of STPVs and clear glazing configurations combined with ILS in various climates. Also its adoption offers a range of benefits for the carbon footprint within buildings and develops design strategies that seek to balance implemention of STPV window and ILS with the improvements in energy efficiency and luminous environment aspects. Further studies need to evaluate the impact of internal dynamic shading devices and any STPV technology in terms of thermooptical properties and high conversion efficiency with various sizing. Eventually, the potential of applying STPVs combined with ILS has a substantial influence to provide better visual comfort and save energy in open-office buildings.
The data used in the study can be made available upon sending request to the corresponding author.
The authors declare that there are no conflicts of interest regarding the publication of this paper.
This research has been funded from Research Deanship in University of Ha’il, Saudi Arabia, through Project no. RG-20 105.