Piezoelectric materials are materials that are capable of producing electric current when subjected to mechanical stress and vice versa. The piezoelectric effect was first discovered in the year 1880 by the brothers Jacques Curie and Pierre Curie and has ever since been applied and experimented with in multiple scenarios.
Several naturally occurring materials such as crystals, certain ceramics, sugar, enamel, etc. exhibit this property. Some of the earliest applications of the piezoelectric effect date back to WWI and WW2 where piezoelectric materials were used to make radar-detectors, super-sensitive microphones, sonar devices, and smart sensors in various weapons.
Through the years researchers developed newer methods of using piezoelectric materials and today they are seen in a wide range of smart sensors, actuators, etc., including daily use objects such as gas grills and stoves, cigarette lighters, microphones, and quartz watches.
But how do such materials help the building industry?
Concepts centered around sustainability have become necessary for consideration in the design and construction of any structure to minimize and reduce negative environmental impacts. It is exactly under this bracket that piezoelectric materials can be put to use.
These materials can capture and respond to ambient vibrations, airflow, sound waves by storing and converting the mechanical energy induced by stress and latent heat into electric current. This very well validates their usage in energy harvesting and smart sensing in buildings to make the structures self-sustainable.
Imagine if you could harness the mechanical energy of a group of students walking in a school corridor, or teams of athletes playing a football match, or the vibrations caused by the movement of hospital beds and other medical equipment, and convert the stress induced by such movements into electricity, you would be able to generate electricity on-site and support off-grid systems.
If that be the case then doesn’t all this make one wonder if the piezoelectric effect could be achieved in some very commonly used building materials such as timber and concrete? Here are a few facts to clear out the ambiguity.
Concrete is known to be a widely used building material in the building industry- so commonly used that a piezoelectric property addition to its properties would make a majority of the built forms across the globe self-sustainable.
But since its chemical composition and structure do not resemble a crystal it does not inherently exhibit piezoelectric properties. But research has shown that the addition of admixture components and external conditioning can increase the piezoelectric properties of cement mixtures which can then be used for on-site energy harvesting.
On the other hand, timber, which is yet another widely used building material, shows potential for the application of the concept of piezoelectricity. Timber being a lightweight construction material comes with the issue of generating high sound vibrations and most often needs interventions such as dampers to avoid discomfort caused due to heavy vibrations in the structure. Here piezoelectric materials can be used to both absorb the unnecessary vibrations and convert them into usable electrical energy.
This technique of using the concept of conversion of mechanical-to-electrical ambient vibrations can be brought under the category of on-site energy generation and can significantly reduce the operational energy demand of the building.
Then how exactly is it that this effect can be used in architecture?
“Building components can significantly reduce their energy consumption through implementing energy harvesting, self-sustained sensing and actuating devices with piezoelectric materials.”
Using piezoelectric materials in the implication of sustainability in architecture includes harvesting the multitude of ambient vibrations that the occupants of a building have to offer. Acoustical treatment to diminish the impact of unwanted noise can be spearheaded by using piezoelectric materials to absorb and convert the mechanical waves into electricity. This would also mean that more and more devices can be operated wirelessly winding up in less demand for and usage of operational energy.
A good place to use piezoelectric materials could be entry and exit ways, into and out of a building/room/any space alike. A doormat like an element, with embedded piezoelectric materials, can be introduced that could collect and store mechanical energy every time a person walked over it while entering or leaving a room/space which can then be used to power the electrical features of that very space.
Similarly, since piezoelectric materials are also capable of capturing and responding to sound waves, lighting and ventilation features can be controlled with the sound waves produced by the users of the space in the form of claps or voice receptors.
Buildings that are often exposed to heavy wind loads, moderate seismic vibrations, and mechanical waves alike can harvest the mechanical energy of the vibrations and store them for future use as electrical energy in creating off-grid technologies for buildings.
While high-rise buildings can benefit from the vibration energies, low-rise buildings can draw mechanical energy from more localized activities such as the pedestrian movement of occupants across various spaces of the building. Such are the concepts being researched and developed.
In Japan, a piezoelectric power mat was installed to harness mechanical energy from the walking of the commuters to provide electricity to light up LED display boards in the station. A similar mat-ceramic tiles-were installed in a train station in Tokyo at the ticket counters to generate electricity by the piezoelectric effect.
As part of the research, a system was developed to collect and harness vibrations from moving vehicles on highways. Another example of a similar research experiment is that of a system that was developed to use ambient vibrations to generate electricity enough to melt snow on sidewalks.
Many such applications are still under research and experimentation with a massive scope for advancement in application techniques and use. And although piezoelectric materials seem to be promising in displaying properties for usage in the sustainability bracket, they bear limitations that may restrict or minimize their usage only to those areas that effectively offer the required amount of mechanical energy or sources alike for the required amount of power quotient to be achieved for usage.
It is, therefore, necessary to study their composition and behavioral properties under high stress and then invest them in techniques for sustainability.
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