How many Panels are needed to power a Solar Car?

Petrol and Diesel cars are yesterday’s news. The current trend in the automotive industry is to switch to electric cars as soon as possible. This is all after the bomb of Global Warming was dropped on the entire world. So, not only are the fossil fuels running out, but their use is also causing a lot of damage to the environment and atmosphere as we speak. The problem however with electric cars is that the source of electricity is usually fossil fuels. With the threat of global warming, it is imperative that electricity is generated primarily from renewable energy.

This is where solar energy comes in. However, there are a lot of limitations when it comes to harnessing the energy of the sun. At the same time, there is also a ton of benefits attached to it. So, the question is – Is it possible to power cars with solar panels? Let’s do the math and find out. I know that math is generally boring, but I will try to keep it as interesting as possible. Time to get started.

2017 Chevy Bolt

Our Assumptions

When talking about a solar powered car, we mean an electric car whose battery is charged with solar panels. This can be done in two ways – directly with on-board solar panels, or indirectly with solar powered charging stations. The great part about using electric to power the car is that the efficiency will be quite high, around 80 to 90 percent. This means that around 80 to 90 percent of the electrical energy supplied will be directly transmitted over to the motors and will help drive the car forward.

For the simplicity of calculations (and to avoid boredom), we are not going to dive into the physics of it. We are going to consider 3 models and their respective mileage according to the amount of energy they require per 100 miles. We will consider both – the direct and indirect modes of solar charging. It is important to remember that most of these calculations will be theoretical and may not hold completely true in real life.

Don’t worry, these cars aren’t solely run by solar panels. They have in-built batteries that are charged beforehand. The solar panels’ job is to recharge this battery on the go. To make our calculations even easier and give a clearer picture, let’s assume that the vehicles are fitted with a battery that will last for a bit more than 100 miles.

There might be slight variations here and there due to various factors that pose a challenge to solar charging. These factors include the efficiency of the solar panel, weather and driving conditions. Let’s get started with the first car.


2017 Chevy Bolt

This car is supposed to consume about 28 kWh per 100 miles. Now, on a typical work day, a person is likely to travel around 33 miles to and from work. Thus, you will be using one third of the battery, or roughly 9 kWh a day. This means that the car can go for about 3 days without any charge. However, it’s best to charge the car daily in case an emergency arises.

Indirect Charging

In the market, you will find that an average solar panel that gives an output of 100 W is around 5.6 square meter in area. So, let’s say you have a garage roof area of about 56 square meters. That means you can get an output of 1 kW. You could also alter the angle to fit in more panels or use your entire roof for solar panels. If you think it will look ugly, don’t worry. Tesla’s Solar Roofing has got you covered.

At the end of the day you manage to somehow get an output of 4 kW with high efficiency solar panels and using your entire roof. Then it would take approximately 9/4 or 2.25 hours to charge your car for the entire day next time. But remember we mentioned that there are many factors to consider when we talk about charging? Because of these factors, the time is practically double or it will require 4.5 hours instead of 2.25. So, leaving your Chevy Bolt for overnight charging will power the vehicle for approximately two days.

But how can we charge the vehicle using solar energy at night you ask? Well it’s simple. The solar panels will charge a battery in the house similar to Tesla’s Powerwall during the day. This, in turn, will charge the car at night.

Direct charging

But that was all about indirect charging. What about direct charging where the solar panels are mounted on the car itself? Well, a car has a lot less area available for mounting solar panels compared to a house. A typical sedan will have around 12 to 14 square meters of area. This is enough for only 200 W. Also, the bigger the car is, more energy it will consume. The Chevy Bolt, being a hatchback, has about 10 square meters of area for solar panels which is enough for 150 W. Now, if by some miracle, the car receives the entire 150 W, it would still take the car 60 hours to charge for a day’s work. This is quite impractical and thus has been ruled out on several occasions.

This is why people (and sometimes even engineers) often regard the whole concept of Solar Car Racing as an urban myth. The engineers behind these cars design them specifically for one person and increase the area available for the panels. They also use super-efficient panels and batteries to help drive the car along with extremely light materials. All of this increases the range of their car on a single charge by miles.


Other models

I am sure that you can do the rest of the calculations yourself for any given car. But, just for reference here are the two others –

A 2013 Nissan Leaf would give approximately the same numbers as the Chevy Bolt since it consumes 29 kWh per 100 miles.

A 2017 Tesla Model S however would consume 35 kWh per 100 miles. Thus, it would require 6 hours to charge the battery for a day or 12 for two.

2017 Tesla Model S

But is it cheaper?

One of the main reasons for switching to new technology is that they prove to be more economical. When it comes to electric cars, let’s first consider the possibility of conventional charging. On average, a kilowatt-hour in america costs 12 cents. Thus it would take $3.36 if you use the Chevy Bolt and $4.2 if you use the Tesla S to travel 100 miles. Considering a Toyota Camry with a mileage of 28 MPG, it would take $8.57 to travel the same distance. That is more than double the amount of the electric car.

On the other hand, the use of solar panels, will incur virtually no operating costs other than maintenance. However, the installation costs are quite high. It costs around $3000 to set up a system that generates 1kW of energy. Going by our previous assumption of a car travelling just 33 miles a day (which is a very optimistic estimate without considering any roadtrips), a person would save about $1000 in a year.

So in three years, all you would be doing is making a profit. It would be absolutely free energy. Also, bear in mind this same system will only be charging your car for about 30 to 50 percent of the time. The rest of the time it can power your home (again, at virtually no extra costs).


The Verdict

As clear as day, the electrical and the solar alternatives are more economical. They are also more environment-friendly. It will only take a few more years and after that, a solar car can be considered as an actual mode of transport for day to day life.

After all that, you must be glad that you don’t have to deal with such calculations in your daily life. As I mentioned before, there are a lot more factors at play here and each of them bring a change to the numbers. If you thought these calculations were child’s play and want to dive deeper into the physics of it all, you can check out Tom Murphy’s blog on Solar Powered Cars.

We have both taken different assumptions and that’s why our numbers may not add up. For the rest of you, see the numbers for yourselves. It is possible to make indirect Solar Cars a reality. Promoting the use of solar energy will bring about new and further developments in the technology used today, and who knows? Maybe one day, solar cars that are directly powered by solar panels may become a reality (or even a thing of the past, if we’re lucky!). I don’t know about you, but a future where everything runs on renewable energy and the atmosphere is devoid of polluting gases, seems pretty exciting to me.