Re: Homebuilt train to Orbost

[dbromage@fang.omni.com.au (David Bromage)]

David Martin (d_martin@mountains.net.au) wrote:
> If solar cars can crack 100km/h, think what steel wheels on steel rail could
> do with one or two solar carriages in tow.

Probably about 30km/h. You'll be hard pressed to find any steel in a solar
car. It's all light aluminium, composites and plastic. And only holds one
person. The average solar car weighs less than 100kg. Teams invariably use
female drivers because they weigh less. The car needs all its solar panel
area to move itself and the driver.

Towing two trailers would require more powerful motors, which would
increase the weight considerably. Solar cars already use the most powerful
lightweight motors available. You'd effectively have to make all vehicles
powered, which means basically three cars.

The biggest problem is cell efficiency. The best conversion is about 27%.
The maximum power of the sun is about 1000W/m2, and that's when the sun is
directly overhead. When the sun is low in the sky, it can be down around
350W/m2.

To give you an idea of what this means, I did a quick back of the envelope
calculation. If you covered the entire roof of an XPT with solar cells
(leaving room for exhaust and fans), on a sunny day you could just about
power the air conditioning of one trailer.

I have seen a solar powered model railway, but never anything carrying
passengers.

Last of all is the cost. UNSW's new solar car cost $2 million to build!

As I type this I happen to be wearing my Bayer Solar Boat Race shirt.
I invite everybody to visit Canberra in late April for the annual solar
boat race, part of the the Australian Science Festival. You'll learn a lot
about solar technology.

Cheers
David