Ever since I bought an iRobot vacuum Roomba (it works very
well in most rooms), I’d been wondering when someone would build
one that works outside buildings as a window washer. Therefore I
was psyched to discover not one, but two such prototypes during my
latest foray through the wonderful world of YouTube.
The first one is the cooler looking of the two and has been in
testing for a few months. It’s an experimental model created at the
University of Nebraska and actually sticks itself to the glass. See
for yourself (but turn down the volume a little as the sound of the
motor is a bit annoying):
The second robot is a more serious industrial machine that
appears to be much closer to hitting the commercial market.
Lucky for us the sun is a wonderful source of clean energy. Its
rays can be harnessed and transformed into electricity using
semi-conductor-based solar cells that power homes, buildings, and
even transportation. Researchers have spent decades trying to
refine this process.
Recently, MIT researchers have made a
significant mark in this endeavor. Associate Professor Marc A.
Baldo, leader of the project, and a team of four graduate students
of the Department of Electrical Engineering and Computer Science,
have constructed a cost-efficient solar concentrator device based
on a failed 1970s model that uses glass and dye. In practical
terms, the concentrator device is a high-efficiency window.
Currently, solar concentrators on the market track the sun’s
rays using large mobile mirrors that are both expensive to arrange
and to maintain. Furthermore, Baldo explains, the solar cells that
house these concentrators must be cooled, thus the entire assembly
Baldo’s new solar concentrator increases the amount of usable
energy by a factor of 40, all while cutting costs by reducing the
amount of solar cell, which because its base is silicon is rather
The device consists of glass coated with a mixture of relatively
inexpensive dyes that absorbs the light and re-emits it on a new
wavelength into the glass to be collected by the solar cells, which
are located on the edges of the glass.
Baldo says the 1970s model failed in two ways: the collected
light was absorbed before it reached the edges of the glass and the
dyes were unstable.
Using optical techniques developed for lasers and other diodes,
the MIT engineers found the perfect ratio
of dyes that would allow the light that is absorbed and emitted to
travel a longer distance before reaching the solar cells.