Energy harvesting using kinetic energy of vehicles

With the increasing global energy demand, clean and affordable sources of energy are being adopted 
over time. Road Power Generation (RPG) is thus an alternate to conventional electricity generation. 
RPG technologies generate electrical power from vehicles by harnessing their kinetic energy. The most 
common RPG technology is RPG by speed breaker mechanism. However, this paper will discuss the 
construction of a novel Electro-Mechanical system which can be employed on the surface of a road and 
thus can produce electricity of up to six kilowatts per day. A vehicle induces reciprocating linear motion 
into the RPG flip plates which is then converted to rotary motion via rack and pinion. This angular 
motion is converted to electricity via a PMDC generator which can be used to power streetlights. This 
method of generating electricity is called RPG by flip plate mechanism or RPG by reciprocating linear 
motion


INTRODUCTION
The need of alternate energy sources is not a debate but a necessity in this modern era. The demand of clean and affordable energy sources led to the breakthrough of renewable energy sources. RPG is a similar advancement which can be argued to be a green source of energy. With the increasing number of cars on roads, RPG should be the base of smart cities.
Previous RPG methods have not been successful because of the following reasons: • They require the vehicles to slow down their movement because they have the characteristics of a speed breaker.
• The wear and tear of the RPG unit requires substantial maintenance; specifically the springs.
• The safety of the vehicles to step on these units is a major challenge.
RPG by flip plate mechanism addresses the above issues significantly. This foot unit utilizes the hortizontal stroke of the vehicle and as a result; the vehicles do not have to slow down anymore. The maintenance of the RPG unit is very easy, and any malfunction does not endanger the vehicle above. The piezoelectric material as discussed above is a handy way to generate electricity but has several drawbacks when applied to the concept of RPG (Lee et al., 2010).
• Sound waves bend the piezoelectric material, creating a changing voltage.
• Crystal is prone to crack if overstressed.
• It may get affected by long use at high temperatures. Road Power generation by speed breakers is the most common RPG method as of now, but it also has several drawbacks (Rao, Kumar, & Suresh, 2014): • Cannot be installed on main roads or highways since it requires the car to stop.
• If too much pressure is applied the spring can deform.
• If too less pressure is applied, the unit may not produce any electricity.

RPG BY HARNESSING THE WASTED HEAT ENERGY
This type of road power generation is a prediction made in the domain of RPG. It can be set up by employing heat absorbing material to capture the wasted heat energy of tires. It is predicted to have the following pitfalls: • Very high setup cost.
• Material quality is very rare.
• High maintenance cost.

METHODOLOGY AND RESEARCH
The RPG unit is 4 foot wide, 3 foot long and 3 foot high in structural dimension. The frame which holds everything in place is made up of high tensile steel or can be made of any material with high stress tolerance. It has the following parts:  The upper shaft had a 20 mm gauge and had 3 circular pinions mounted on it. Each pinion had 64 teeth, a diameter of 5 inches and thickness same as that of the rack. Each pinion had a clutch bearing fitted at the center and then passed through the 20mm shaft. The shaft also has a type A sprocket mounted on it with 66 teeth. The shaft was placed just below the rack arrangements by the means of pillow blocks and fitted in the RPG unit.  Furthermore, to transfer the energy of this shaft to the DC generator, one spur gear is also mounted on the lower shaft. This shaft was also held using pillow blocks and fitted in the RPG unit.

POWER GENERATION AND STORAGE
The other spur gear was fitted on the shaft of a 24V, 1050 rpm, 1.1 kW PMDC generator. After the generator does some useful work, the voltage produced was fed to a buck/boost converter. This buckboost converter steps up or down the input voltage to a constant 13V DC output. This voltage was then fed to a charge controller which cuts off the supply once the battery is fully charged.
An Arduino Uno was connected to a voltage sensor module and a current sensor module to monitor the average energy production per vehicle.

WORKING OF THE RPG UNIT
The RPG unit is placed on the same level as the road surface. When a moving car runs over the RPG unit, the male flip plate is displaced 5 cm to the female flip plate. This displacement causes potential energy to be stored in the springs. When the spring releases that stored energy (by bringing the male flip plate back to its original position), the racks rotate the pinions by a circumference of 5 cm. This rotation induces a unidirectional rotation in the upper shaft, since the pinions have clutch bearings at their centers. As a result, a uniform, unidirectional, rotation is produced (Chandwani, Patel, & Kothari, 2017).
This rotation in the upper shaft is transferred to the lower shaft by means of a chain drive sprocket. Since torque and angular velocity are inversely proportional, the upper shaft will have high torque and low angular velocity compared to the lower shaft which will have lower torque and a higher angular velocity.
The flywheel in the lower shaft helps to resist the change in the rotational speed of the lower shaft due to its high moment of inertia. As a result, energy is stored in the flywheel and released to the generator which converts the energy stored into electrical energy (Fatima & Mustafa, 2011).

RESULTS AND CONCLUSION
In this paper an Electro-mechanical system was designed and implemented. It is clear that the factors affecting the power production is the spring's constant 'k' and the distance between the plates. Since it was not possible for us to continuously change the distance between the flip plate A and B, we decided to change the spring constant. Upon experimentation, following results were obtained.