PIEZOELECTRIC
ARCHITECTURE
SUSTAINABLE ENERGY DEVELOPMENT
JAGDEEP SINGH | B.ARCH SEM III | September 7, 2015
WHAT IS PEIZOELECTRIC EFFECT?
Piezoelectricity is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure. It is derived from the Greek piezo or piezein, which means to squeeze or press, and electric or electron, which means amber, an ancient source of electric charge. Piezoelectricity was discovered in 1880 by
French physicists Jacques and Pierre Curie.
The piezoelectric effect is understood as the linear electromechanical interaction between the mechanical and the electrical state in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process in that materials exhibiting the direct piezoelectric effect
(the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect (the internal generation of a mechanical strain resulting from an applied electrical field). For example, Lead Zirconate Titanate(LZT) crystals will generate measurable piezoelectricity when their static structure is deformed by about 0.1% of the original dimension. Conversely, those same crystals will change about 0.1% of their static dimension when an external electric field is applied to the material. The inverse piezoelectric effect is used in production of ultrasonic sound waves.
MECHANISM
A piezoelectric substance is one that produces an electric charge when a mechanical stress is applied (the substance is squeezed or stretched). Conversely, a mechanical deformation (the substance shrinks or expands) is produced when an electric field is applied. This effect is formed in crystals that have no center of symmetry. To explain this, we have to look at the individual molecules that make up the crystal. Each molecule has a polarization, one end is more negatively charged and the other end is positively charged, and is called a dipole. This is a result of the atoms that make up the molecule and the way the molecules are shaped. The polar axis is an imaginary line that runs through the center of both charges on the molecule. In a monocrystal the polar axes of all of the dipoles lie in one direction. The crystal is said to be symmetrical because if you were to cut the crystal at any point, the resultant polar axes of the two pieces would lie in the same direction as the original. In a polycrystal, there are different regions within the material that have a different polar axis. It is asymmetrical because there is no point at which the crystal could be cut that would leave the two remaining pieces with the same resultant polar axis.
PAGE 1
In order to produce the piezoelectric effect, the polycrystal is heated under the application of a strong electric field. The heat allows the molecules to move more freely and the electric field forces all of the dipoles in the crystal to line up and face in nearly the same direction
The piezoelectric effect can now be observed in the crystal. Figure 3 illustrates the piezoelectric effect. Figure 3a shows the piezoelectric material without a stress or charge. If the material is compressed, then a voltage of the same polarity as the poling voltage will appear between the electrodes (b). If stretched, a voltage of opposite polarity will appear (c). Conversely, if a voltage is applied the material will deform. A voltage with the opposite polarity as the poling voltage will cause the material to expand, (d), and a voltage with the same polarity will cause the material to compress (e). If an AC signal is applied then the material will vibrate at the same frequency as the signal (f).
PAGE 2
PAGE 3
MATERIALS
Many materials, both natural and synthetic, exhibit piezoelectricity
Naturally occurring crystals
Quartz
Berlinite (AlPO4), a rare phosphate mineral that is structurally identical to quartz
Sucrose (table sugar)
Rochelle salt
Topaz
Tourmaline-group minerals
Lead titanate (PbTiO3)
Synthetic crystals
Gallium orthophosphate (GaPO4), a quartz analogic crystal.
Langasite (La3Ga5SiO14), a quartz analogic crystal.
Synthetic ceramics
Ceramics with randomly oriented grains must be ferroelectric to exhibit piezoelectricty. The macroscopic piezoelectricity is possible in textured polycrystalline non–ferroelectric piezoelectric materials, such as AlN and ZnO. The family of ceramics with perovskite, tungsten-bronze and related structures exhibits piezoelectricity:
Barium titanate (BaTiO3)—Barium titanate was the first piezoelectric ceramic discovered.
Lead zirconate titanate (Pb[ZrxTi1−x]O3 0≤x≤1)—more commonly known as PZT, lead zirconate titanate is the most common piezoelectric ceramic in use today.
Potassium niobate (KNbO3)
Lithium niobate (LiNbO3)
Lithium tantalate (LiTaO3)
Sodium tungstate (Na2WO3)
Ba2NaNb5O5
Pb2KNb5O15
Zinc oxide (ZnO)–Wurtzite structure. While single crystals of ZnO are piezoelectric and pyroelectric, polycrystalline (ceramic) ZnO with randomly oriented grains exhibits neither piezoelectric nor pyroelectric effect.
PAGE 4
Lead-free piezoceramics
More recently, there is growing concern regarding the toxicity in lead-containing devices driven by the result of restriction of hazardous substances directive regulations. To address this concern, there has been a resurgence in the compositional development of lead-free piezoelectric materials.
Sodium potassium niobate ((K,Na)NbO3). This material is also known as NKN. In 2004, a group of Japanese researchers led by Yasuyoshi Saito discovered a sodium potassium niobate composition with properties close to those of PZT, including a high T_{C}. Certain compositions of this material have been shown to retain a high mechanical quality factor
(Q_{m}\approx 900) with increasing vibration levels, whereas the mechanical quality factor of hard PZT degrades in such conditions. This fact makes NKN a promising replacement for high power resonance applications, such as piezoelectric transformers.[31]
Bismuth ferrite (BiFeO3) is also a promising candidate for the replacement of lead-based ceramics. Sodium niobate NaNbO3
Bismuth titanate Bi4Ti3O12
Sodium bismuth titanate Na0.5Bi0.5TiO3
So far, neither the environmental impact nor the stability of supplying these substances have been confirmed.
PAGE 5
APPLICATIONS OF PEIZOELECTRICITY IN ARCHITECTURE
SOLAR-POWERED PIEZOELECTRIC SPORTS STADIUM, RAIBAREILLY, INDIA
India just broke ground on a gorgeous solar-powered sports complex that will harvest piezoelectric energy from the crowds that enter its gates. Designed by Studio Symbiosis, the Athletic Ripple
Project was recently commemorated by India's National Congress President, Sonia Gandhi. The vast new complex emerges out of the natural landscape as an iconic structure that mimics the form of water droplets.
Each section, or ripple, contains a different sporting activity space. The “droplets” vary in size, design and purpose, but Studio Symbiosis unified each section by designing them to symbolize individual pebbles in a pond. The complex to emulates the ebb and flow of a swelling pond, and therefore gradates into the existing landscape rather than obstructing it.
The complex is a sort of “sports city” that was designed to minimize congestion — a pedestrian walkway will be constructed down the middle, and opposing roadways surround the perimeter. The walkway brings visitors closer to the action and away from the surrounding urban environment and traffic. The sports center also boasts an impressive roster of sustainable and energy-efficient building strategies. The roofs of the various stadium cells are lined with both solar and pneumatic panels, which collect and generate energy. The center’s anticipated heavy foot traffic will also be put to good
PAGE 6
use — piezoelectric generators will harness the movement of the crowds and convert it into energy. The ambitious project will continue to develop and it’s currently slated for completion in 2012.
NEW PIEZOELECTRIC RAILWAYS HARVEST ENERGY FROM PASSING TRAINS
Piezoelectric technology generates energy from pressure and stress on certain surfaces, and we’ve seen it harvest electricity from roads and dance floors to power lights and signs. Recently Israeli company Innowattech unveiled a new use for this versatile energy tech – they’re planning to install piezoelectric pads throughout the country’s railways to generate electricity.
The company has previously used piezoelectric pads on Israeli highways, and now they’re using similar (albeit larger) devices on railways. Innowattech plans on substituting 32 standard railway pads with their own piezoelectric
IPEG PADS, which are of a similar design. In addition to generating energy, the new IPEG pads can determine the size of the wheel that passes over them, as well as the speed and weight of the vehicle. A prototype of the energy-generating system was installed last year by the Technion University and
Israel Railways in order to show the benefits of the technology. The project discovered that a railway track with trafficked by 10 to 20 ten-car trains could produce as much as 120 kWh, which could be used to power infrastructural systems such as signs and lights. Any surplus energy would then be uploaded to the country’s power grid.
PAGE 7
POWERLEAP HARNESSES ENERGY FROM FOOT STEPS!
POWERleap is a floor tiling system that converts wasted energy from human foot traffic into electricity. The magic behind that awesomeness is piezoelectric technology and advanced circuitry design, which converts pitter-patter into power. First showcased in 2007 as part of Metropolis magazine’s Next Generation design competition, we see HUGE potential from this invention.
Individual footsteps might not produce a significant amount of power, but if you consider the total kinetic energy from stampedes of shoppers on 5th avenue, (or commuters in a train station, or revelers in a nightclub), it all adds up fast and could be a viable energy source to power specific applications like lights.
PAGE 8
'STRAWSCRAPER' DESIGN BY BELATCHEW ARKITEKTER
The Swedish architecture firm
Belatchew Arkitekter devised a bizarre new plan for updating one of
Stockholm's tallest buildings. They have proposed adding thousands of large, hairlike straws to the exterior of the Söder Torn tower to harness wind energy. The innovative -- yet entirely strange -- idea could amount to the world's first ever "Strawscraper" if it ever comes to fruition.
"By using piezoelectric technology a large number of thin straws can produce electricity merely through small movements generated by the wind," Belatchew Arkitekter writes in a press release for their creation. "The result is a new kind of wind power plant that opens up possibilities of how buildings can produce energy."
The fancy straws -- composed of
"composite material with piezoelectric properties that can turn motion into electrical energy" -- would certainly give the Söder Torn a new, eye-catching facade. It would also expand the building's current 24-story height to a whopping 40 stories. The extra 16 flights were written into the building's original design; alas the project ended up stopping short in 1997.
PAGE 9
“POWER-GENERATING FLOOR” AT TOKYO STATION
When the East Japan Railway Company (JR
East) decided to invest in alternative energy sources, it only had to look to its users for the perfect source of energy.
Recently the company decided to update their Tokyo Station with a revolutionary new piezoelectric energy generating floor.
The system will harvest the kinetic energy generated by crowds to power ticket gates and display systems!
Piezoelectric flooring is a technology with a wide range of applications that is slowly being adopted in the race to develop alternative energy sources. After all, human power is readily available in pretty much any area with heavy foot traffic, such as a dancefloor, or a tourist attractions.
Naturally, we were excited to hear that JR East will be installing these systems in the floor of one of busiest subway stations on the planet.
JR East has been trialing these systems for the past year. They have recently improved and expanded the system by changing the floor covering from rubber to stone tiles, and have improved the layout of the mechanisms to improve energy generation. The total amount of floor-space will add up to around 25 square meters, and they expect to obtain over 1,400kw per day – more than enough to power their systems.
