Energy Management in Solar Vehicles: Batteries, MPPT, and PV Systems

This report reviews the effective use of solar energy in vehicles, focusing on energy management systems. It highlights the importance of energy management in maximizing vehicle performance, particularly through battery and photovoltaic technologies. The report discusses the role of Maximum Power Point Trackers (MPPT) in boosting battery charging rates and the necessity of backup batteries to prevent system shutdowns. It explores different battery types, including lead-acid, lithium-ion, and alkaline batteries, and examines various photovoltaic technologies used in solar-powered cars. The review also considers the impact of driving strategies on energy consumption, emphasizing the need for efficient energy management to ensure optimal performance in solar vehicles. This document is available on Desklib, a platform providing study tools and resources for students.

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EFFECTIVE USE OF SOLAR ENERGY IN VEHICLES
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Abstract
There was a first solar competition planned in Australia in the year 1987 for triggering the
development of vehicles powered by solar for all interested individuals in the world. The form
that day onwards, there has been a number of technologies that are being used in making the
solar vehicle, improving its functionality into imitating the performance seen in conventional
vehicles. However, limitations still get encountered during the vehicle’s process of development.
Particularly in regards to its management of energy. The energy in this vehicle comes from
battery technology and photovoltaic technology. Energy management in this scenario refers to
the effective and judicious consumption of energy for the purpose of maximizing the vehicle’s
performance. Generally, the systems used in managing energy in solar vehicles are required to
have electrical power flowing from the photovoltaic cells to the various loads that should be
optimized and monitored. The behaviours of the connected loads greatly influence the strategies
and utility planning for the developed soar vehicle. Therefore, proper management of loads is
one strategy for drawing a good amount of power from the PV modules. Devices such as the
Maximum Power Point Trackers should be implemented between batteries and the PV modules
for boosting the charging rates of batteries. Additionally, there has to be a back-up battery within
the vehicle’s system for the elimination of unexpected shutdown of systems. This brings one
back to the importance of determining appropriate systems during the design stages for ensuring
that the solar vehicle is getting maximum energy from its system. This paper aims to review the
systems used in managing solar car energy.
Keywords: Batteries, MPPT, Energy Management, Photovoltaic

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1. Introduction
Solar vehicles are vehicles which make use of photovoltaic modules to source their electrical
energy for charging their batteries. These vehicles are known to be green due to their zero
emission of greenhouse gases into the atmosphere. Generally, figure 1 shown below identifies
the basic system for energy management applicable in solar vehicles (Saravanan et al., 2016).
The sun’s rays force the PV modules to increase their energy state and therefore developing
Direct Current. The electricity produced is taken in by the photovoltaic controller which take sit
for storage within the batteries. In these cars, the batteries function to power DC motor for the
generation of mechanical energy important for moving the vehicle.
The process looks simple but there are difficulties in ensuring the management system is
working. The complication increases when the vehicle should be moving for non-stop for long
distances since the sun rarely maintains its intensity. In theory, the battery’s charging rate should
equalize the consumption of current by the motors in rotation (Mohamed et al., 2019).
Figure 1 above shows an example of a solar vehicle system sued in energy

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On the other hand, this situation is not the operational ideal conditions since the weather is
unpredictable other than various influencing factors such as slope, speed and condition of the
road, therefore, the solar vehicle is considered complex and impractical. If only there were better
systems that manage the energy consumption thereby catering for the needs of the car
(Aravindan et al., 2015).
The introduction of solar vehicles has also allowed competition to be conducted on these
vehicles’ functionality. Hence, invoking researches as the activities look to develop the car. In a
span of 20 years, these solar cars are developing remarkably (Grandone et al., 2016). Their
speed, weight and technique for managing energy are improving. In the past, the solar vehicles
composed of three wheels, 2 existing in the front for suspension and steering systems and a 1 at
the back with its own motor. The body shape of the vehicle allows it to reach 120 km/h as well
as covering long distances.
Figure 2 above identifies a solar car.

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2.Literature Review
This paper intends to conduct a review of the literature to investigate how these solar powered
vehicles being used. The review looks into journals that are associated with battery and
photovoltaic systems efficiency gathering.
2.1.Reviewing Method
Journals with data on systems used in managing vehicle power as well as the electronic
databases. These journals are found on the internet. The literature used was about 5 years old to
make sure relevant and latest technology was used.
2.2.System type
The strategy of managing energy is a very crucial factor which prevents waste or shortage of
energy in solar cars. Also, the system’s energy has to be in good management in that: input from
the driver (through acceleration or braking pads) can be regularly satisfied ensuring that the
battery is being charged consistently. Practically, the array’s electrical output, as well as
electricity demand in the vehicle's application, mostly don not easily synchronize since there
could a higher demand than the array’s output. Hence, complicating the system. System
optimization is therefore important in that power, size, cost and reliability of the solar’s array
together with the battery has to be sustaining the demand (Sabry et al., 2017).
This scenario makes it important to have a minimum difference between the battery’s charging
rate and the PV array’s charging capacity. To solve these issues, one can connect the DC/DC
converter in between the battery and the PV array which make up the control and topology
circuit. This is mostly identified as the MPPT (Sovacool et al., 2018).

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2.2.1.Maximum Power Point Tracker
Using the MPPT is crucial since it allows maximization of the current produced from the PV
array. Rezk and Hasaneen (2015) discuss an experiment that used 26 MPPT which was purposed
to cater for the 1800 cells. The weight of every MPPT was 270 grams and all these MPPTs were
able to generate 97% efficiency. In this system, the design involved 14 MPPT being connected to
produce an overall 45W amount of power from the array cells, while 12 MPPT could be
generating an overall 90W amount of power from the array. On the other hand, Kumar and Sahu
(2019) showcase another experiment involving 12 MPPT being used in boosting the required
maximum power taken from the solar array whenever the car moved. Additionally, Shenoy et al.
(2018) discuss a solar car design which could move at 97 km/h for a distance of 2,998 km. This
solar car was able to take 30 hours and an additional ¾ hours to complete running the distance.
The design purposed to use the MPPT in boosting generated from the PV cells before supplying
its battery. The downside is that its MPPT was not deeply discussed for confidential issues.
2.2.2.Non-MPPT
Mohamed et al. (2019) showcase an experiment on a solar car in which one PLASMATRONIC
solar controller is being used for its capability of charging its system’s battery using 40A
maximum current. This controller is made up of a passive system, hence, it was not purposed to
boost the gained power from its solar cells before charging the battery. On this note, any value
gotten from the PV array would be directly used by the controller in charging its battery.
2.3.Battery Types

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The solar-powered cars make use of batteries whose function include (Harish, et al., 2018):
 Storing the gained electricity from the photovoltaic array when there is the sunlight in the
day.
 Directly supplying current whenever it is needed.
 It is a smoothening medium for fluctuating voltage as well as current output from the
solar cell arrays towards the loads.
This part of the literature review discusses three battery classes that are mostly used in storing
electricity that will be supplied later for running the solar-powered cars.
2.3.1.Lead Acid Batteries
This type of battery is further split into numerous types as per their manufacture’s designs. The
automotive batteries are in most trucks, cars, aircraft and boats for the aim of starting the engine
that will provide power for running. In most cases, these batteries are not deeply discharged or
overused thereby making them last longer and taking several years to wear off (Ballantyne et al.,
2018). The boats and caravans use the leisure batteries for supplying power used in house
appliances and their discharge is moderate. On the other side, for the uninterruptible supply of
power, industrial batteries are the best. They can work in various situations. The tubular-plate
traction battery is purposed for powering electric vehicles. On the other hand, the sealed lead
acid battery is becoming popular in solar vehicles in that they do not need to be maintained
regularly and can be oriented in any position when being used. An example of the sealed lead
acid battery is the gel type battery. The gel type battery has a good performance other than its
disadvantages whereby it is very big and heavy for vehicles powered using solar cells (Akinyele
et al., 2017).

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2.3.2.Litium Ion
Aravindan et al. (2015) look into the use of lithium-ion batteries together with a capacitor unit
that collects current storing the excessively generated electricity by the solar cells. This solar car
also allows direct use of electricity during situations where low-speed travelling is required.
Kim et al. (2019) identify the 25 lithium-ion battery that makes it possible for supplying more
than 40 A/h current and also identifies the 459 lithium-ion batteries that supply an equally large
amount of current.
2.3.3. Alkaline Battery
McKerracher et al. (2015) use the nickel-cadmium batteries which is made up of 204 cells and
supplies 115.6 total voltage for running a rally solar car. Other than the good performance of this
battery, its disadvantage lies in its heavyweight when compared to the lithium battery.
2.4.Types of PV
There is an advancing technology within the science used in solar panels. Lately, the years of
research have produced efficient solar cells made of silicon with improved stability and
standardized cost which has dropped due to the increased manufacturing production of PV cells
(Odeh, 2018). The solar cells have been principally used in powering cars through PVs as one
independent source of electricity, a stand-alone technique as seen in figure 3 below. In
optimizing the output gotten from PV arrays, there is a need for sophisticated designs. The
design depends on the sun’s latitude which commands the array’s angle towards the sun. The
intensity of the sun also has an effect on the PV output electricity that has to be consistent
throughout the daytime. One more important factor is the possibility of the PV array being
steerable or adjustable in following the sun’s latitude as the say advances. Ensuring constant

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position with reference to the sun allows right angle capture of the sun’s rays at the PV’s surface.
Steerable solar arrays are more expensive to develop other than giving preferred array output
compared to fixed arrays (Sharma et al., 2015).
Figure 3 above shows a design of a stand-alone PV solar used in a solar car
Zhang et al. (2015) discuss a solar cell made up of polycrystalline silicon that is purposed to
produce a 480W maximum power to an electric motor. This solar cell is able to allocate enough
power for running the car at 110 km/h. Nuna II was discussed. Nuna II solar cell was made up of
gallium-arsenide triple junctions with an additional SMART-1 satellite launched to the moon.
Also, Saravanan et al. (2016) discuss the solar cell made up of 2800 GaAs cells that possess a
20% efficiency.
Looking at Jeong et al. (2017), whose literature is on a powered PV cell using polycrystalline
silicon cells, there designed solar PV was able to output 1 kW power during a normal sunny day.

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One solar car discussed in (Moluguri et al., 2016) has its design on monocrystalline silicon cells
producing a 6% efficiency while and another a solar cell with 26% efficiency and make use of
more than 3500 cells.
2.5.Driving Strategy
According to Prakash and Mohant (2017), a good strategy for driving is crucial for enduring
controlled speed in accordance with the profile of the road, the condition of weather, sun’s
radiation and battery’s condition. Cruising strategy is a technique that when used properly, it can
be able to generate as much required power as the driving conditions need to be given that the
generated energy is fluctuating. Good strategies allow movement at high speeds while the
consumption at the motor current is kept minimal as stated in (Grandone, et al., 2016). Cruising
strategies have been implemented in different solar car racing in that the design of some of the
racing cars are using driving built on cruising simulation, supervision support as well as speed or
power control optimization (Prakash & Mohanty, 2017).
3.Conclusion
Looking at the solar vehicles, there are great implications within the developing electric vehicles
which are raising more interest in research regarding the effective use of energy within the public
domain. Characteristic system understanding and testing of the developed solar vehicles’
electrical system is important to be able to reach an optimized system which efficiently and
effectively manages to use its battery’s power. Some of the noted and most crucial facts on
vehicles powered by solar cells are mentioned below (Denny et al., 2018):
 Capacity

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The capacity of batteries should be in good quantity for absorbing current provided by the
PV arrays during sunlight hours also, these batteries should be able to last longer.
 Weight
With the addition of weight, the rolling resistance of the solar car is increased. Thereby,
forcing the car to draw in more power from the solar PV array. Therefore, less weight
within the vehicle as seen in aeroplanes improves the vehicle’s operating efficiency.
 Voltage
The total voltage chosen for a battery has to be critically thought upon. This is done
within the early stages of designing the vehicle hence displaying the importance of good
planning. These battery banks used in solar cars should be suited to use as per the PV
array requirement and the controller as well as motor operating voltages.

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