# Efficiency of a Solar Powered Car

## Main Question or Discussion Point

As I am currently residing in Doha, Qatar, I've decided to base my mini-thesis on Solar energy. And although I haven't got it finalized yet, I'm thinking of investigating the efficiency of solar powered cars.

I could build a toy car and input solar-powered batteries as opposed to another toy car with regular batteries. I would then measure the difference in speed, longevity, etc.

I'd appreciate it if you could drop by some suggestions. Thank you. :)

## Answers and Replies

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Doug Huffman
Gold Member
Quantify the performance of a hypothetical 100% efficient solar powered car.

Hi! I was also thinking, maybe measuring the effectiveness of Solar Energy as the primary power source of a city?

Doug Huffman
Gold Member
Remember that the Solar Constant is about 1350 Watt/meter^2 and that less than continuously depending on latitude and cloud cover.

russ_watters
Mentor
"Efficiency" and "effectivenes" are tough words to use on their own in this context, because the energy is free, so why would we care much about the efficiency?

Ie, if a gas turbine power plant is 40% efficient and a solar farm is 20% efficient, which should you use to power your city? The more efficient one? No: the cheaper one. The only thing efficiency matters for in this example is how it factors into the cost calculations.

You'll need to think very specifically about what you are trying to investigate and how (or if) efficiency figures in.

hgducharme and mheslep
Thanks so much for the critique! I'll most likely stick to Mr. Huffman's suggestion of quantifying the performance of a hypothetical 100% efficient solar powered car as it could be supported experimentally. It's not too hard nor too simple as well.

If you've got any other suggestions or comments, please let me know. Thanks :)

Khashishi
All electricity is the same, once you stored it into batteries. So I don't see how you learn anything by running solar-powered batteries. Or do you mean a battery of photovoltaic cells? Usually battery refers to energy storage, not generation.

russ_watters
Mentor
Thanks so much for the critique! I'll most likely stick to Mr. Huffman's suggestion of quantifying the performance of a hypothetical 100% efficient solar powered car as it could be supported experimentally. It's not too hard nor too simple as well.

If you've got any other suggestions or comments, please let me know. Thanks :)
You're welcome....

...so do you want to continue to develop this idea here? What parameters, specifically, do you want to compare? I mean: "100% efficient" at doing what? To expand a bit on my previous post, people use the word "efficiency" to talk about car performence, but that's mainly just a loose word choice. Fuel efficiency or fuel economy are more descriptive. They let us know that unlike thermodynamic efficiency, the answer isn't expressed in %, it is typically expressed in distance per fuel energy. And even for actual %s, they are only unitless because the units cancel in the calculation: energy out per energy in. So you still have to specify what the parameters are. So that's what I mean about being very specific about what you are trying to evaluate.

For electric cars, common measures are:

-MPGe (which is the US government's attempt to make the efficiency measure compatible with gas car MPG).
-Miles per charge.
-kWh per 100 miles

CWatters
Homework Helper
Gold Member
Perhaps have a look at the area, mass and efficiency of solar panels needed to power a car and then decide if it would be practical to put solar cells on a car.

Fuel efficiency and fuel economy.... Wow. Those are really good ones. I haven't exactly thought of the parameters yet as I am still on the verge of proposing the project to my supervisor. I was initially going to propose another project before, but I stumbled upon a reading that a country such as Qatar does not adhere to Solar Energy. And I found that pretty interesting.

Also, regarding Mr. Huffman's suggestion, if it's "hypothetical", am I then also basing it on hypothetical data? Because I just realized that if no machine is 100% efficient, then what's the purpose of proceeding with the experiment? :/

CWatters
Homework Helper
Gold Member
See the comments by russ_watters above. You have to be careful what you mean by "efficiency" - it's not always the most important thing.

For example:

All electric room heaters are 100% efficient.
Condensing gas furnaces/boilers are perhaps 95% efficient.

So it looks like electric is better than gas. However in the UK electricity costs three times as much as gas (per kWH).

Hmmm, yes, but... It does have a lot to do with the country's fuel economy, doesn't it?
I'm slowly realizing that there may be a lot of flaws to that research question.

I thought of another one... You know, just so I'd have a lot to propose to my supervisor.
- Determination of thermoelectric characteristics in the ambient environment of Qatar

Uhmmm... Peltier tiles, maybe?

Please let me know what you think. Thanks :)

Or if you have other research questions in mind...

Bystander