# Eco friendly Electricity generation: Electricity from speed breakers

This article has been presented by our friend Annamalai Arunachalam in BITS, Pilani and is posted with his permission.

## Abstract

In this technological era, all the modern equipments and advancements rely on the electricity. Electricity serves as a back bone to these achievements. Can we imagine a second without electricity? Calculate the losses caused by the shortage of electricity.

Currently there are various methods for electricity generation. Here is a novel method for generating electricity from speed breakers which is eco-friendly.

In our design, the speed breakers have to be made with springs. When a vehicle loads a speed breaker it compresses air and this air is used to drive the impeller. This serves as a source for the alternator.

Thus in this article, going to present a new method of electricity generation. Hope this design will be implemented soon !!!

## Sources of Energy

The various sources of energy are

- Solar
- Tidal
- Wind etc

In this article we are using the speed breaker as one of the energy source.

## Speed breakers

In Indian roads, currently we have speed breakers of rigid type, made of steel or with tar. When a heavy load crosses the speed breaker it remains unreformed, which alone limits the speed of vehiclesThe national highways come with minimum 8 meters wide, 0.015m thickness. We are proposing slight changes in the current roads.

## Proposed design

Here we are making the speed breaker of vibrating type, when a vehicle crosses the speed breaker, it gets depressed and then it gets back to its original position.

### Dimensions

Height of speed breaker : 0.2m

Width of speed breaker : 0.4m

Length of speed breaker : 4m

Material used for speed breaker: Steel

### Speed breaker -design

The speed breakers are fitted with helical spring at the base. The shape of speed breaker is trapezoidal, because when a vehicle comes to point A, the load will be acting between A and B. This compresses the speed breaker, this goes down due to the presence of spring. When a vehicle is in between B & C, there will be maximum load on the speed breaker. At the C & D, there will be minimum load on speed breaker.

A hollow trench has to be dig out with dimensions slightly greater than the size of speed breaker. The dimensions are

Height: 0.35m

Length : 4m

Width :0.45m

The bottom layer of the trench is filled with concrete or with wooden plates of 0.5m. This is for cushion effect. Above this layer helical springs of n windings is wounded.

The speed breaker is assumed to be a uniformly distributed load.

The self (dead) weight of speed breaker can be represented as

When a vehicle with a maximum load passes, it loads the speed breaker it is represented as

Therefore the total weight on the speed breaker is found to be the sum of initial (dead) weight and the weight of the vehicle (load applied).

Total weight (w)= Dead weight + Vehicle weight

For the design of speed breaker, the design weight can be found by the product of factor of safety and its total weight. The factor of safety determines the maximum level that the beam (speed breaker) can be loaded.

### Spring design

The actual height of spring is 0.3m before loading. The deflection of the spring is given by

?= 64 w *n*N*R^3 /(Gd^4)

where

?-deflection (in our case maximum ? =0.1m)

w=designed load

R= mean diameter of coil

d =diameter of wire

n=no of spring turns

G= Modulus of rigidity = 8*10^4 N/mm2

N= No. of springs

#### Impact of vehicle on speed breaker

#### Maximum load on speed breaker

#### Vehicle leaving the speed breaker

The no of turns in the spring to get the deflection of 0.1m is given by

n= ?Gd^4/(64 w*N*R^3)

After the vehicle crosses the speed breaker, the air inside the base will be compressed.

### Pneumatic design

When the load is on the speed breaker, the volume of air compressed by it is found by,

Volume of compressed air = Volume of air in base Volume of spring

= l*b*h N*n*?d^2/4

= x m^3/s

The x m^3/s air released is taken through the outlet at one end of speed breaker. A pneumatic cylinder with an FRL unit is connected to the outlet of this pipe. When the pressure in the FRL unit exceeds the defined level the valve opens and the pressurized air is given to the nozzle.

The diameter of the inlet (nozzle) must be greater than the outlet.

di>d0

Here the pressure energy is converted to kinetic energy i.e pressure?high velocity. The atmospheric air is compressed by the speed breaker and is used to drive the impeller.

### Impeller-design

When air with higher velocity strikes the vanes of impeller, it starts rotating. The energy available at the inlet is only kinetic energy and the outlet is atmospheric. The impeller has

- Nozzle
- Runner and bucket
- Casing

The amount of air striking the vanes of runner is controlled by providing a spear in nozzle

#### Runner

It consists of a circular disc on the periphery of which have number of buckets evenly spaced are fixed. Each bucket is divided in to 2 symmetrical parts by a dividing wall is know as splitter. The splitter divides air jet in to two equal parts. The buckets are shaped in such a way that jet gets deflected through 160 or 170 degree. Materials used are cast iron, caste steel, or stainless.

#### Casing

This can be provided to safeguard against accidents.When air jet strikes the runner revolves for a longer time due to inertia.

### Alternator

An electrical generator is a machine which converts mechanical energy in to electrical energy. The energy conversion is based on the principle of production of dynamically induced e.m.f. According to Faradays laws of electromagnetic induction, whenever a conductor cuts magnetic flux, dynamically induced e.m.f. is produced in it. This e.m.f causes a current to flow if the conductor circuit is closed.

Two basic essential parts of an electric generator are

- A magnetic field and
- A conductor or conductors which can so as to move to cut the flux.

Alternator varies from d.c generator in the aspect of stationary armature mounted on a stationary element called stator and field windings on a rotating element called rotor. So slip rings, brushes and commutator are eliminated.

Generation of induced e.m.f: When the rotor rotates, the stator conductors are cut by the magnetic flux, hence they have induced e.m.f. produced in them.

#### Speed and frequency

In an alternator, there exists a definite relationship between the rotational speed (N) of the rotor, the frequency(f) of the generated e.m.f. and the number of poles (P).

Consider the armature conductor marked x situated at the centre of a N-pole rotating in clockwise direction. The conductor being, situated at the place of maximum flux density will have maximum e.m.f. induced in it.

The direction of the induced e.m.f. is given by Flemings right hand rule. i.e the thumb indicates the direction of the motion of the conductor relative to the field.

When the conductor is in the interpolar gap as at gap A, it has minimum e.m.f. induced in it, because flux density is minimum. Again when it is at the centre of a S- pole, it has maximum e.m.f induced in it, because flux density at B is maximum. But the direction of e.m.f. when the conductor is over a N- pole is opposite to that when it is over a S- pole. Obviously one cycle of e.m.f. is induced in a conductor when one pair of poles passes over it. In other words, the e.m.f. in an armature conductor goes through one cycle in angular distance equal to twice the pole-pitch.

Let

P= total no of magnetic poles

N= rotative speed of the rotor in r.p.m

f= frequency of generated e.m.f. in hz

Since one cycle of e.m.f is produced when a pair of poles passes past a conductor the no of cycles of e.m.f produced in one revolution of the rotor is equal to the no of pair of poles.

No of cycles/revolution = P/2

and

No of revolutions/second = N/60Frequency = (P/2)*(N/60)= P*N/120 hz

Thus the mechanical energy from speed breaker serves as an input source to the alternator which generates the electricity of 10kw

### Conclusion

In this article, written about a new approach of generation of electricity from the speed breaker. This can generate up to 100Kwatts of power which can be used for various purposes. Here we have converted the mechanical energy to pneumatic energy then to electrical energy. This design will help to reduce the cost of electricity generation.

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