Electric Power Plant of Sea Wave Using Piezoelectric Sensors.

20/10/2019

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• Erick Rohan
• Fernanda Carolina
• Gustavo Teixeira
• Larissa Silva
• José Vitor

Salvador, Bahia.

Overview

Energy consumption through renewable sources assists in reducing energy consumption from fossil fuels, which is largely responsible for the release of CO2 into the atmosphere and consequently contributes to global warming.

Considering the potential energy available in the oceans, Brazil is territorially favored with about 7.36 thousand kilometers of waterfront watered by the Atlantic Ocean.

Based on this condition, we aim to generate electrical energy from wave power, in view of the Brazilian ocean current, particularly the Bahian coast. Thus, the proposed solution aims to evaluate the technical feasibility of the projection and installation of a wave power mini-plant of piezoelectric sensors.

Objectives

1. To develop the feasibility of applying a system for capturing and converting hydrodynamic energy into electrical energy;
2. To compose the renewable energy production matrix, mitigating the use of fossil fuel sources and the greenhouse effect emitted gases;
3. To contribute to existed renewable forms that assists in a more sustainable environment.

Specifications

By carefully investigation the schematic model of the mini-mill scale is shown below:

Subtitle:

1 - Lever arm;

2- Drag force;

3- Necessary pressure to generate Watt.

Source: Gustavo Teixeira’s picture and scanner

Since the application of piezoelectric sensors in terrestrial systems such as sidewalks and highways goes through idle periods, we consider the possibility of using these materials at sea, taking advantage of the continuous movement of waters, which causes a drag force on any material installed in order to resist to your movements. Thus, we created a system to contribute to the production of electrical energy that harnesses the mechanical energy of the seas.

1. Piezoelectric

In 1880, the French physicists Pierre Curie, and his brother Jacques Curie stated that it is likely to generate a potential difference by compressing quartz crystals. The most commonly found piezoelectric materials in nature are the Quartz Crystals, Zinc Oxide, and artificially high-efficiency PZT (Lead Zirconate Titanate).

The piezoelectric effect, whose component can give rise to electric charges, has been studied in order to achieve a capable generator of supplying energy to devices with low current.

1.1. The operation principle

Usually the charges on a piezoelectric crystal are perfectly balanced even if they are not regularly arranged.

There is a vector cancellation of the charges, admitting no extra charge on the crystal faces.

Pressing the crystal tends to balance the charges.

There will be no cancellation of charges. Then, from the pressure exerted on the crystal, an electrical network was produced on the crystal faces - and this is piezoelectricity. Comparison between the Pecém wave power plant in Ceará and the generation system using Piezoelectric material.

1.1. PZT (Lead Zirconate Titanate)

The PZT has ferroelectricity and piezoelectricity behavior that allows important technological applications in transducers, amplifiers and sensors.

Ceramics that have piezoelectricity properties belong to the group of ferroelectricity materials. Current systems are almost exclusively based on Lead Zirconate Titanate (PZT); that is, they consist of mixed crystals of lead zirconate (PbZrO3) and lead titanate (PbTiO3). The piezoceramic components have a polycrystalline structure that contains several crystallites (domains) and each one of them is composed of a plurality of elemental cells. The elemental cells of these ferroelectricity ceramics exhibit the perovskite crystal structure, which can generally be described by the formula A2+B4+O32- .

The schematic diagram of an ideal perovskite structure, without considering distortions due to spontaneous bias below Curie temperature. The bivalent positively charged ion is located in the center of the cube, while the tetravalent positively charged ion forms the corners of the cube. The bivalent negative ions in the center of the margin of each cube in this illustration. As for PZT (lead zirconate titanate) mixed crystal, the formula is: A: Pb2+, B: Ti4+ / Zr4+.

After sintering, the domains of a ceramic body show a statistically distributed arbitrary orientation, ie piezoelectric. These piezoelectricity properties must be originated by polarization. In this process, the ceramic body is exposed to a strong CC electric field, aligning it towards the field. They maintain this orientation on a large scale even after the CC field is no longer applied - a necessary condition for the piezoelectricity behavior of ferroelectricity ceramics.

According to Michael McApine, in his 2010 work “Technological Innovation”, he says that PZT is up to be 100 times more efficient than quartz, and it can achieve an 80% conversion of force into electricity, PZT becomes more efficient as more energy applies to it and it has a limit absorption of 871 w/m2.

1.1.1. Piezoelectric Sensors

The vibration sensor is a component designed to pick up a vibration and to convert it into an electrical signal by vibrating the structure.

The vibration sensors are generally constructed from piezoelectric materials. When a force is exerted on the crystal and a voltage is generated, it can be very high, reaching values up to thousands of volts in some cases. Although they can generate large stresses, these materials are not good conductors of electricity.

1.1.2. PZT Piezoelectric Sensor Pads

Table 4.1 - Pressure, voltage, current and power ratio

Researches show that sizing to connect a 10 W LED bulb requires 1 insert diameter = 35mm; radius = 17.5 mm = 0.0175 m; area = 2r2= 0,00192 m2; and by applying a force of 20 N (2.0 kgf) there is a response of 0.0244 W. That is, to obtain 10W it would require 409.84 pulses of the force applied on the tablet to obtain the desired 10W.

Thus, for a lamp to operate for 1 hour, it would take 1,475,424 pulses for 20 N to force on the tablet to generate 10 Wh.

• The 100 pads system

To maintain the same force of 20 N over the area of 100 tablets (0.192 m2) a pressure of 10 416.6 Pascal would be required which would correspond to a mass of 200 kg. Like this, 2000N2,44W. It would take 4.09 pulses to reach the desired 10 W. For a lamp to operate for 1 hour, 14 754 09 force pulses of 2000N over 100 tablets are required to produce 10Wh.

1.2. The Wave Power Plate

The plate will be submerged and it will have the following dimensions:

680.4 N corresponds to the force produced by the hammer on the piezoelectric inserts.

According to the behavior of the kg x Pot graph, the calculation was necessary to identify the angular coefficient to know the proportion.

According to the table presented in the article “Electricity generation by piezoelectric sensors” by Luiz Fernando Suzarte Silva Ferreira of the Center University of Brasilia: The approximate electric power value for the pressure exerted by a mass of 11.34 kgf is 0.123 W. As the dimensioning is for 6 pads in each plate: 6x0,123W = 0,738W.

• Em cada pulso/compressão há a possibilidade de comprimir as duas placas: 2x0,738W = 1,476W
• In each pulse / compression there is the possibility to compress the two plates: 2x0,738W = 1,476W

Thus, to turn on a 10W lamp requires 6.775 compressions to occur in the system, approximately 7.

To generate enough power to keep the lamp on for 1 hour, ie 10Wh, 7 x 3600s = 24 390.2 compressions are required:

With an average rate of 8 waves per minute on the coast we have;

8 compressions - 60 s;

24 390.2 compressions - x s;

x = 182 926.8 s = 50 813 hours = 2,1 days.

At a distance of 10 m, using the dimensions given here for the paddles (0.3 m x 0.42 m). It is possible to install 30 blades that in 2,1 days are capable of producing.

30 x 10Wh = 330 Wh.

This energy is enough to keep a 32” TV that consumes 48 W for 6h and 15 mins, or a simple 300W blender, turned on for 1h.

1. The structure

The structure of the mini plant is composed of

1. 1 6.6kg PET paddle G 0.42m x 0.3m; area = 0.126 m2;

anchor;

1. 2100Wh battery bank;

Sea buoy (customized);

Aluminum bar 10m

Larger lever arm of PET G 0.6m;

Smallest PET G arm 0.3m;

Converter;

Two plates with 6 piezoelectric inserts each, arranged in parallel, and produce for each 3.4W compression pulse. The 6 tablets form an area = 0.01152 m2;

Piezoelectric sensors.

Data: Sea drag force = 680.4 N; with drag coefficient CD = 0.6; and velocity V = 3 m / s.

This force is applied to both plates.

Plate layout with 6 tablets

PLATE ENLARGEMENT ALREADY POSITIONED IN THE STRUCTURE (SIDE VIEW)

With this system it is possible to produce 24 390.2 compression pulses in a period of 2.1 days, considering a wave frequency of 8 waves per minute, sufficient to light a 10W LED lamp in a period of 1h.

The structure of the mini plant is composed of

1. 1 PET paddle G 0.42m x 0.3m; area = 0.126 m2;
2. Larger lever arm of PET G 0.6m;
3. Smallest PET G arm 0.3m;
4. Two plates with 6 piezoelectric inserts each, arranged in parallel, and produce for each 3.4W compression pulse. The 6 tablets form an area = 0.01152 m2.

Data: Sea drag force = 680.4 N; with drag coefficient CD= 0,6; and velocity V = 3 m / s.

This force is applied to both plates.

Using this system it is possible to produce 10495.6 compression pulses in the 21.86 h period considering a wave frequency of 8 waves per minute, sufficient to light a 10W LED lamp in the 1 h period.

3. Costs

Paddles: R$0.20 cents / kg 6.6 x 0.20 = R$ 39.60;

Piezoelectric sensors: R$ 120,00;

Aluminum bar: R$ 17,00/meter 17 x 10 = R$ 170,00;

Sea buoy: R$ 100,00;

Anchor: R$ 100.00;

2100Wh Battery Bank: R$ 500, and

Converter = R$ 400.

In conclusion, the study made it possible that the mini-plant system would produce 4500Wh / month or 4.5kWh/month.

Comparação de custo x energia gerada entre o sistema Piezoelétrico com a usina maremotriz em construção em Pecém Ceará.

The energy converted from a 0.92 m high wave at a constant speed of 3 m / s by a single generator cell composed of a 0.262 m2 area palette and 0.9 meter long axis using 12 PZT sensors, with 6 sensors on each side and 3.43 W per pulse (wave).

The Brazilian wave regime has an average of 8 waves per minute, which equals 0.133 Hz, considering this wave regime the energy generated per second by a generating unit and of 0.457 w / s (Eq. 1).

P=Pp*w=3,43*0,133=0,457 w/s (Eq. 1)

The cost of 30 generating units considering 12 PZT piezoelectric sensors each1,92*10-3 m2 area, shaft section area of 19,6 cm2 and palette thickness of 2 cm, both made of PETG, 1 rectifier 15 Amps, 1 DC / DC converter, 1 12 V battery with 115 ah capacity, in Brazil, it costs 1620 reais.

The cost of the wave power station in Ceará in Pecém is 18 million reais and it produces 100 Kw / s. With the same amount of money it would be possible to build 337500 PZT piezoelectric crystal generation units, which generates 154.23 kw/s, demonstrating a 54.23% increase in electrical output with the same investment, disregarding the drastic reduction of cost when producing the scale generating unit. (Eq 2)

PT=P*337500=154237,5 w/s (Eq. 2)

4. REFERÊNCIAS

https://www.maxwellbohr.com.br/downloads/robotica/mec1000_kdr5000/tutorial_eletronica_-_aplicacoes_e_funcionamento_de_sensores.pdf

http://www.mec.uff.br/pdfteses/WashingtonBatistaLima2013.pdf

https://semanaacademica.org.br/system/files/artigos/robson.pdf

https://www.ceramtec.com.br/materiais-ceramicos/piezoceramicos/basicos/

http://www.scielo.br/pdf/ce/v49n310/a0849310.pdf

https://www.bloomberg.com/news/articles/2019-05-16/cornell-university-s-crypto-professor-to-launch-his-own-coin

SISTEMA DE GERAÇÃO DE ENERGIA VIA SENSORES PIEZOELÉTRICOS

SIMULAÇÃO DE ONDAS OCEÂNICAS NA COSTA SUL-SUDESTE BRASILEIRA PARA ANÁLISE DO POTENCIAL ENERGÉTICO

https://www.ece.nus.edu.sg/stfpage/elelc/Publication/2019/ACS%20NANO_19V13_2_Self-Powered%20and%20Self-Functional%20Cotton%20Sock%20Using%20Piezoelectric%20and%20Triboelectric%20Hybrid%20Mechanism%20for%20Healthcare%20and%20Sports%20Monitoring.pdf

https://periodicos.itp.ifsp.edu.br/index.php/IC/article/view/273/406

https://www.nucleodoconhecimento.com.br/engenharia-eletrica/geracao-de-energia

CÁLCULO DAS PROPRIEDADES ELETROMECÂNICAS EFETIVAS DE MATERIAIS ELASTO-PIEZOELÉTRICOS POROSOS

https://www.researchgate.net/publication/275379329_The_Power_and_Efficiency_Limits_of_Piezoelectric_Energy_Harvesting

https://teses.usp.br/teses/disponiveis/3/3132/tde-04082003-173204/publico/Tese_final.pdf