What are Adaptive Photovoltaic Facades and how do they function?

It is an established fact these days that out of the total worldwide energy demand, approximately 40% is consumed by our buildings. Similarly, our fossil fuel based activities such as air conditioning, heating, ventilating, etc. account for more than 30% of the overall anthropogenic emission of greenhouse gases. Therefore, it is undeniable that these buildings also present an excellent potential for energy savings. This is the exact reason why the idea of Zero Energy Building (ZEB) has gained so much attention all over the world.  Photovoltaic (PV) system can be integrated into the buildings as a viable alternative for harvesting this huge source of energy.

Building-integrated photovoltaics or BIPV is suitable for use in all parts of a building envelope including the skylights, shades, roofs, and facades etc. However, it has been observed that the façade mounted systems are less effective compared to the ones that are roof mounted. This is simply because of the difference in solar irradiance between vertical and horizontal surfaces. Therefore, in the BIPV systems market, the largest market share currently belongs to rooftop applications. However, experts around the world are engaged in efforts to make the façade BIPV systems more efficient. Their goal is to use adaptive photovoltaic facades as a climate-adaptive building shell and a dynamic building envelope.

Adaptive Photovoltaic (PV) Facades:

One of the most important purposes of a building facade is to make it function as a mediator or boundary where a plethora of advanced technologies can be integrated for the fulfilment of various goals. In today’s context, the growing demand for sustainability has brought about significant changes in the concept of building façade or envelope. It is no longer considered to be a passive barrier, but an adaptive, active, and sensible layer between the exterior and interior environments. The focus of these adaptive facades is to deal with multiple requirements such as mitigation of environmental impacts, saving and harvesting energy, and much more. With their adaptive characteristics, these facades work towards improving building performance by enhancing daylight utilisation, reducing cooling and heating loads, generating electricity, and fine tuning different activities. In simple words, an adaptive PV façade is a photovoltaic system mounted on a façade capable of integrating the benefit of integrated solar tracking with that of adaptive shading.

In order to operate at the peak efficiency, perpendicular alignment to the sun is necessary for the PV modules. However, façade BIPV receives lower incident radiation compared to ground and rooftop installations because of its vertical orientation. However, they can contribute significantly to local electricity generation because of lower seasonal and diurnal variations. They also allow PV integration into other components of the façade such as shading systems, cladding, etc.

A solar tracking mechanism is one of the important necessities for adaptive PV façade systems to be able to yield maximum solar cells. Compared to horizontally fixed and fixed-tilt modules, solar tracking improves a PV module’s output by 70% and 40% respectively. Dual-axis and single-axis are the two categories of solar trackers. However, incorporation of dual-axis trackers in BIPV installations is extremely difficult. Solar trackers can operate both in presence or absence of sun sensors. In the absence of sun sensors, solar tracking is accomplished utilising cyclic astronomical algorithms capable of evaluating the position of the sun.

Currently, the most serious roadblock for adaptive PV façade modules is the complex technical nature of the solar tracking actuators. When designed for extensive use in outdoor locations, these components can be very expensive. Moreover, as a result of their mechanical complexity, they need substantial maintenance on a regular basis. The heavy weight of the trackers has also been a concern for many. However, the good news is that there is a growing interest around the world to develop low weight and low cost solar trackers ad actuators. As an example, soft pneumatic actuators with compressed air-control have already been tested and implemented.

Final Thoughts:

As building-integrated photovoltaics become an integral part of the global drive to shift towards zero energy buildings, facades gain the centerstage in terms of addressing the global energy issues.  One of the sure-fire ways to deal with these demands is to implement intelligent alternatives such as PV facades. Adaptive PV facades present a viable approach towards the optimisation of both solar gain control and solar energy production through a façade mounted and PV integrated shading device.

CGS Façade Group is a team of experts with a combined experience of over hundred years in façade consultation, design, engineering and documentation. We offer complete solutions for your building façade, staring from the initial sketch concept to fabricated products that create your building envelope. Please contact us for all your building façade related needs.