BMW testing cars with solar panels

Yes, Audi still uses the solar sunroof as an option on A8 series, and V8 and V10 engined A6 series cars. I would like to see them offer the feature on Q7 for the same purpose. Maybe replace that third panel all the way in back would be a good idea. Also, replace the nearly worthless sunroof in the A5/S5 with a solar unit would be a better use of space since they can't make the car without the sunroof from what I understand anyway.

— Neverfollow (View Profile)

Posted on 5/15/2008 1:20:38 PM | | Votes: 3   

Wow.

No need to be a prick.

Is a comment about Audi an automatic knock against BMW?

Grow up little man. Grow up.

— answer (View Profile)

Posted on 5/15/2008 4:25:52 PM | | Votes: 2   

Um, I think starting an argument for no reason is pretty "weak".

My post was relevant, not derogatory to your precious BMW in the slightest, and certainly not mean sprited.

There is a difference between name calling as you put it, and using the correct word as an accurate discriptor of something or someone.

With that said, you definately are a prick.

— answer (View Profile)

Posted on 5/15/2008 10:29:27 PM | | Votes: 0   

Audi has had this for years.

— 993Turbo (View Profile)

Posted on 5/16/2008 8:03:52 AM | | Votes: 2   

Also... This for the engineers out there. Solar panel collects heat from the sun. Why can't the panel collect heat from the exhaust instead of using water add to the car?

I don't know therefore I ask.

— Brembo (View Profile)

Posted on 5/15/2008 12:02:47 PM | | Votes: 2   

Brembo,

There are basically two ways you achieve this:
1. Semiconductors. If you use semiconductors, you have a certain operational temperature window- just like everything electronics. If the temperature gets rather too high, you may end up with a damaged system. Thus the semiconductor approach is favourable to temperature regimes that can be managed.
2. Furnace: this is best suited for systems that have high operating ambient temperature. You collect the heat to heat up a fluid that in turn is used to drive a turbine.

With technology we have increased the operational windows of semiconductors but they still are not close to the operational window of the furnace based solar power system.
The key will be to find the sweet spot to adopt the most efficient technology which if my memory serves me right is semiconductor-based solar panels.

— AdmiralT20 (View Profile)

Posted on 5/15/2008 1:12:55 PM | | Votes: 1   

Interesting.

To avoid damage from over heating, can't the energy be transfer elsewhere in the car to store like a battery.

— Brembo (View Profile)

Posted on 5/15/2008 2:21:06 PM | | Votes: 1   

Brembo,

The reason that conventional solar panels are not used in the way you stated is because solar panels do not convert heat into electricity at all.

Solar panels convert light energy into electrical energy (heat given off is wasted energy and part of the inefficiency of a photovoltaic solar panels).

Put as simply as possible the basic idea behind conventional photovoltaics is that light (photons) excite atoms in a thin semiconductor layer. When atoms are excited sufficiently by these incoming photons, some of their electrons "break away" from their host atom and begin to move within the semiconductor. This flow of electrons is what we harness as electrical current.

The reason manufacturers have not yet used photovoltaics (PV's) to cover the roof of cars is 2 fold.

1) Conventional PV's are very inefficient. Even the best available tech is still only able to convert less than 30% of the available solar energy into usable electricity.

2) Conventional PV's are very expensive. It would cost the manufacturer hundreds if not thousands of dollars per car to outfit the entire roof with solar panels.

The gain in efficiency would be very marginal and given the high cost, the idea is neither feasible nor practical with current technology. The best PV's would be able to provide power for a small fan or to trickle charge the vehicles battery or to run some low power accessories. Running the car on solar power is out of the question. You would need hundreds or thousands of square feet of PV's in direct sunlight to provide the power required to actually drive a normal vehicle.

— AutoEng (View Profile)

Posted on 5/15/2008 3:12:11 PM | | Votes: 2   

Thanks, I just got smarter in this forum.

— Brembo (View Profile)

Posted on 5/15/2008 8:27:14 PM | | Votes: 4   

Actually it is the radiation.

— AdmiralT20 (View Profile)

Posted on 5/15/2008 1:16:29 PM | | Votes: 4   

YEah, but isn't heat the transfer of energy?

— Brembo (View Profile)

Posted on 5/15/2008 2:19:11 PM | | Votes: 1   

Sholeman,

As Brembo just mentioned, heat is a form of energy transfer.
There are basically three methods of transferring heat: Conduction, Convection, and Radiation.

— AdmiralT20 (View Profile)

Posted on 5/15/2008 3:05:05 PM | | Votes: 1   

Many of BMW's innovations have been highly beneficial, this isn't just some lame marketing fad, if there's efficient gains to be made here then BMW will go ahead with the technology, if not then they won't. At least their trying to help kerb their dependence on oil, the auto industry is under such huge pressure nowadays to be seen as green, BMW have managed to lower their CO2 emisions by more than any other manufacturer in the business so i don't think what their doing is h=just to be seen as "hip" and "cool", there's realy gains to be made here.

— Kinger (View Profile)

Posted on 5/16/2008 4:29:27 AM | | Votes: 2