| Work Detail |
Middle Eastern scientists have simulated the use of different integrated photovoltaic systems in high-rise buildings in Dubai. They found that for buildings with more than seven stories, BIPV can be superior to rooftop power generation.
A group of researchers in the Middle East have evaluated how building-integrated photovoltaics (BIPV) can help reduce electricity consumption in high-rise buildings in Dubai, United Arab Emirates.
The academics explained that the city has 25 buildings over 300 meters, while 14 additional skyscrapers of this scale are currently being built. “In Dubai, 38.9% of total energy consumption is related to buildings, and the high-rise sector is key to energy efficiency,” they said. “BIPV can be a very efficient alternative in Dubai due to the reduction of load on buildings and power generation. This work aims to investigate the energy efficiency according to the number of floors with BIPV application.”
The group carried out a series of simulations using EnergyPlus and TRNSYS software and considered a building where all floors have the same dimension: height of 3.6 meters, floor area of ??400 m2 and window-to-wall ratio of 80%.
“The main conditions for the simulation were assumed to be an occupancy density of 0.2 people/m2, a sensible heat of 65 W/person and a latent heat of 54 W/person,” they added. “The lighting density of 20.0 W/m2, the device density of 22.0 W/m2, and the ventilation factors through air conditioners per person were assumed to be 35 m3/person.”
Modeling
The scientists assumed that the building had a temperature of 20ºC for heating and 26ºC for cooling on working days under the Duabi climate. Using previous academic literature, the scientists estimated the buildings annual energy consumption at 360 kWh/m2. A reference model was created with a low-emissivity (Low-E) double-layer photovoltaic window (LDW) and five typologies of BIPV systems were considered.
Three of them were window replacement systems based on translucent amorphous silicon (a-Si) thin film modules. They added three different configurations called double-layer PV window (a-si DW), double-layer low-e PV window (a-si LDW), and triple low-e PV window (a-si LTW).
Another typology of BIPV system was a photovoltaic curtain wall based on crystalline silicon modules (c-si FMAT). The fifth and final option was a hybrid system that combined the FMAT with the a-si LTW.
“As a result of the analysis, the BIPV window replacement system is effective from the 15th floor, the BIPV exterior wall replacement system is effective from the 12th floor, and the hybrid type BIPV window replacement and exterior wall replacement It is effective from the ninth floor,” the academics explained.
Comparison with Rooftop PV
They also noted that BIPV arrays not only add power generation to the building but also reduce its cooling and heating load, due to the materials used for their assembly. In the case of window replacement, scientists also found that the cooling and heating load reduction is more significant than conventional rooftop PV generation.
The three window replacement configurations managed to produce 20.2 kWh/m2 annually, while the load reduction was 27.2 kWh/m2, 33.6 kWh/m2 and 34.1 kWh/m2 in the a-models. si DW, a-si LDW and a- si LTW, respectively. This compares to an annual consumption of 352.6 kWh/m2 for basic LDW.
As for the FMAT c-si system, it managed to reduce the load by 20.1 kWh/m2 and sustain the building with a production of 26.1 kWh/m2. The hybrid configuration reduced the load by 24.9 kWh/m2 and contributed 34.9 kWh/m2 in generation.
The scientists then compared the performance of the different BIPV systems with that of a conventional rooftop installation, which in the simulated building could occupy an area of ??400 m2. They discovered that this array can only be competitive with BIPV arrays if the building does not exceed seven floors.
“The power reduction rate is continuously maintained at 17.0% when applying hybrid type PV, and this result is equivalent to the 5-story scale (17.0%) of the roof-mounted system,” they said. “In addition, compared to the 15.5% energy reduction rate of the LTW a-si, the 6-story scale version (14.2%) of the roof-mounted BAPV was analyzed. C-si FMAT also maintains an energy reduction rate of 13.2% regardless of the increase in the number of floors, which is close to the 7-story scale value (12.2%) of the roof-mounted BAPV ”.
Their findings are presented in the study “ Analyzing the effectiveness of building integrated photovoltaics (BIPV) to reduce the energy consumption in Dubai ”, published in Ain Shams Engineering Journal . The group included academics from Ajman University in the United Arab Emirates (UAE) and Prince Mohammad bin Fahd University in Saudi Arabia. |
