Intoduction:
The word piezoelectric is derived from the greek word piezein meaning Squeeze. Piezoelectric is nothing but change in electric polarization that is produced when a material is subjected to mechanical stress and due to it external electric field is produced.
Piezoelectric effect is reversible that is when we apply an electric charge mechanical strain is produced. We can say that piezoelectric road is a new energy evolution to provide a sustainable solution in terms of environment, economy and social needs.
Piezoelectric Energy Roads
At present we are using asphalt roads. Whenever vehicle passes over it the road vibrates and lot of heat energy is generated and it is wasted. By using piezoelectric generators in roads we can convert it into energy.
Piezoelectric material in form of piezoelectric devices is used in the application of making piezoelectric roads. When a vehicle travels in a road, the wheels exert a force into the piezoelectric device and so the deformation in the material takes place. These piezoelectric devices are placed about 5 centimetres below the surface of the roads. This deformation absorbs the force and helps in power generation.
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Piezoelectric Smart Road Construction
- The first layer is laid with Fine gravel and sand content. Then a thin layer of asphalt is laid and it acts as a strong base for generators.
- Piezoelectric generators are placed in quick drying concrete and left for half an hour.
- All the generators are connected in series to get collective output.
- A bitumen sheet is used to cover all the generators to provide better adhesion of concrete to asphalt.
- Finally a thick layer of asphalt is laid which completes the construction.
- For one km of piezoelectric road we can generate 44000 KWH per year.
Sensors used On Road
A piezoelectric sensor is a device that converts one type of energy into another. When electrical energy is produced due to piezoelectric effect it is found proportional to the magnitude of the force. This makes the sensor as an ideal converter of mechanical energy into electric potential.
When used to count vehicles the sensor is mounted into the road’s surface. When a vehicle moves over the sensor it presses it and produces an electric potential. The size of the signal is proportional to the degree of deformation. When vehicle moves off the voltage reverses.
Piezoelectric Materials For Power Generation In Roads
Some of the most commonly used piezoelectric materials are as follows:
1. Piezoelectric Substrate:
- Quartz
- GaAs
2. Thin Film Piezoelectrics:
- ZnO
- Lead Zicornate titanate
Piezoelectric Energy Harvesting Generators
Generators harvest the mechanical energy and converts to electrical energy. It is then stored at the harvesting module. Then it is charged into the battery at one end of the road and then it is distributed.
How much does Piezoelectric Road Costs?
- Generator size – 1 sq feet
- 1 generator approximately Rs.2000
- No of generators needed is 3280 for 1 KM of road
- Cost estimation is 70 lakhs for 1 KM of road
Piezoelectric Roads In Various Countries
ISRAEL – In 2009 Trans Israel highway was embedded with a piezoelectric device to test its efficiency by using the electrical energy produced by the moving vehicles. The result met the required amount of energy i.e 200 KWH for a single lane and 1MWH for four lane.
Countries like INDIA and CALIFORNIA also implemented Piezoelectric roads.
Advantages Of Piezoelectric Roads
- Movement of vehicles are mostly constant on busy roads and so constant power can be produced.
- The power generated is this concept is green power and so there is no harm on the environment.
- This power can be used for street lights and small scale purposes.
- The response is very fast. Even the remote area can be easily electrified.
- It is very easy to control small displacement with the applied voltages.
Disadvantages Of Piezoelectric Roads
- It exhibits high Hysterisis and creep.
- High electric field may lead to breakdown and failure.
- Maintenance of roads is difficult and constant inspections are to be made.
