Abstract:
Vehicular ad-hoc network is an emerging technology and it is an evidence for the rise of interest in energy consumption control. In most of the vehicular networking concepts, Roadside units are spread out along sides of highways in rural areas as well as on the sides of highways where the connection to the electric grid is merely exists. In such scenarios, these RSU's will be enabled with rechargeable batteries with human intervention. Several emerging schemes of Energy conserving in Road side unit provides details about Energy sources by expanding their validity and also its participation in the network. This survey describes several em Energy harvesting provides an alternative approach to power batteries in wireless network. This paper presents a overview of energy harvesting sources, techniques and challenges. It also examine the possibility of Energy harvesting in vehicular networks. Most importantly the challenges in vehicular environment and also the research problems are discussed.
I.INTRODUCTION:
VANET Vehicular ad-hoc network reinforce two types of communication V2V and V2I. V2V(Vehicle to vehicle communication) is an automobile technology designed to allow automobiles to 'talk' each other. The system will use a region of the 5.9 GHz band set aside by the United States Congress in 1999.V2I(Vehicle to Infrastructure communication) is the exchange of critical and safety information between vehicles and roadway infrastructure with wireless technology, intended primarily to avoid motor vehicle crashes. It is a key research program of the Intelligent Transportation System. In VANET connectivity is one among the research challenges to increase the connectivity. A possible key is to utilize the multiple RSU along the roadways. An
RSU can able to allocate communication between the vehicles and also to infrastructure with in its communication range. As RSU's acts as an information distributor in a vehicular network. A solution is to enlarge the coverage area of a VANET 's wireless nodes. where extending the coverage range of vehicles ratio's may widen the connectivity area of a network but this solution is associated with some of the drawbacks, that is smaller data rates and increased packet collision may result in delivery delays.
Fig.1.1VANET Infrastructure
Fig 1.1 shows the VANET's infrastructure where it includes RSU, vehicles with On Board Units in it and the figure also represents how the communication takes place between the RSU and the vehicles By those proposed solution, the network consumes larger amount of energy, which is not always to be brought about and also
providing electric grid power supply from the RSU is expensive and it is a barrier to the vehicular network. A best way to overcome the energy constraint in a vehicular network is by introducing the energy harvesting techniques as it is a rising technology to increase the battery life of electronic devices by the conversion of various forms of energy to DC(direct current).Energy Harvesting is becoming an eminent research area.
II. ENERGY HARVESTING ARCHITECHTURE:
Solar, wind, RF energy
Energy management input
Energy sources
Energy management output
Regulated system voltage
Figure 1.2 Energy Harvesting Architecture
The architecture represents that ambient energy like wind, solar etc are presented in the form of energy sources as input to the energy management unit, where the energy management unit provide energy to the energy storage. After storing the energy for the usage purpose, the energy is transferred to the output energy management unit in the form of regulated power supply.
III. VARIOUS PROPOSED TECHNIQUES IN ENERGY HARVESTING SOURCES :
Energy harvesting in vehicular environment is an emerging technology. This concept has successful research opportunities and a wide range of proposals are also available. To minimize the carbon foot print in vehicular environment, the wind powered RSU's are used in vehicular communication system, a report is provided with perfect investigation of QOS with energy supply and load where it is proposed by
Adnan Muhtar, Bilal R. Qazi, Samya Bhattacharya, Jaafar M. H. Elmirghani. An optimised solar powered RSU's with efficient sleep scheduling technique has been discussed by Vageesh D.C., Moumita patra and C. Siva Ram Murthy. In communication system, using the Energy harvesting sources over a finite amount of communication intervals have proposed by Imtiaz Ahmed[4]. Energy sources are also available in vehicles vibration, civil structures, railway tracks, human motions and also in ocean waves.In section III and IV several energy sources and research areas in energy harvesting are discussed and section V provides challenges in energy sources.
III.ENERGY HARVESTING SOURCES
A basic component of a Energy harvesting is the energy source as it is forces the scope and amount of energy available for harvesting. There are two categories of energy harvesting sources.
Human power
Movement produces kinetic energy which can be converted in to power. Several forms of transport utilize human power. They include the bicycle, wheelchair, walking,skateboard, wheelbarrow, rowing, skis, and rickshaw. Some forms may utilize more than one person. A person who walking or paddling produces energy to harvest. But energy sources are not much useful in wireless network ex. Sensor nodes are always be installed away from residential area that it could be not reachable from humans.
Ambient sources
Energy harvesting or power harvesting, also called Ambient energy scavenging, is the excellent process of obtaining usable energy from natural sources and human-made sources that always surround us in our everyday environment. The temperature of the air surrounding a power supply or cooling medium is abbreviated as ABM. It is called as Ambient room temperature ranges from 68 to 77 degrees Fahrenheit. Examples of ambient energy sources are solar, wind, RF energy they are not used for energy transfer and they all are meant for energy harvesting. Energy harvesting from ambient sources are merely elegant and needs a complex rectifier design that adapt to frequency bands.
IV.RESEARCH ON ENERGY HARVESTING SOURCES
The use of renewable energy in producing electricity is a well known concept. Energy that is
harvested today to produce electricity includes solar, water, wind and thermal. These are the complex strategies to be considered when designing energy harvesting circuits for VANETarising from the interactions of various characteristics of energy sources, devices used, application requirements ,functionality of the nodes and protocols. Most important sources of ambient energy used in VANET is solar energy. Here we have some research efforts with survey on solar. At George Washington University, the students have installed a solar pavement ,i.e nothing but a solar panel walking path designed by Onyx solar in the year of 2013.A system called Solar Road has been developed by the Netherlands Organisation for Applied Scientific Research (TNO). It depends on photovoltaic cells to convert solar energy in to electric energy to drive the motors electrically, where thermal energy converts solar energy in to heat energy. Hence, there the photovoltaic cell converts sunlight in to electricity. Solar manned aircraft(solar impulse)undergone a test flight in Switzerland from 7 am to 9am on 8th july 2010.It flown to a height of 28,000 feet i.e., 8500m. hence it uses solar fuelled batteries. The technology moved to the next level by solar the impulse. Next Sky sailor, it is a future project, It is nothing but a plane which contains solar cells on its wings developed by swiss federal institute of technology in Zurich. It will be able to search the Martian surface and send the pictures back to the earth
V. ENERGY CHALLENGES IN VEHICULAR ENVIRONMENT
solar and wind energy challenges
To implement the EH methods in vehicular networks several challenges and
constraints are to be faced for each and every energy sources. As the conversion of solar energy in to electric current in photovoltaic system, it is not easy to trigger the RSU from the solar panel. In this, a rechargeable battery is the most important component to be used.
Fig 1.3 represents the Energy harvesting system in vehicular environment. The system consists of a wind turbines and respective Road side units. Where the power generated by the wind turbines due to the environment changes. Large batteries are needed to be equipped with RSU's and extra costs are induced. Vehicles which are arriving at night has enough amount of energy when compared to the vehicles that are arrived during day. Time varying wind speed is a challenge to the researchers. where the wind turbines are costly. And the major disadvantage is that the flying creatures like birds, bats are most affected by the wind turbines and also by the noise pollution.
RF Energy Challenges
.In a highway vehicles transfer RF Energy to Road side units. Apart from solar and wind energy harvesting techniques using RF energy is a cost effective solution. But it is always cautious to use this technique in a vehicular environment.
Figure 1.4 RF energy
The fig 1.4 represents the RF energy I n which antenna is present which acquires radio waves and convert it in to DC and after the conversion the power generated will be send as output. Electromagnetic signal carries the energy and information between the vehicles and RSU's which is eliminated by the RF. It is the major problem. While RF energy has the capability to power the batteries of wireless sensor networks in the order of microwatts. Using RF energy will limit the energy transfer time in a vehicular environment same as that of the Energy Harvesting in RSU's.
Fig 1.3 Energy harvesting environment
Research Development Drawbacks Challenge
1. Solar/wind powered High energy transformation rates Uncertain and costly Trade-off between cost and harvested energy to meet application requirement
2. WAVE protocol High network validity Require new quality Instant plan of an energy saving WAVE standard
3. Locating a group of RSU's Expand network bond Correlated methodologies are needed between RSU's In vehicular network very low number of RSU's are used that are correlated in an energy saving network
Table 1. Open research problems.
5.CONCLUSION:
Energy harvesting in vehicular environment is to improve the performance of vehicular network. Careful evaluation of Energy harvesting ha taking place in vehicular environment. Government officials and researchers are always enquiring about the resources with full-fledged vehicular networks. Power grid connection is replaced with Energy harvesting system in a wireless network. The viability of the Energy harvesting methods in vehicular network is explored, taking in to account the isolated features of the mobile vehicular network. This article sheds light on Energy harvesting architecture, research areas, sources and the challenges.