Sep. 10, 2008 - Issue #673: Sex in the City 2008
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Institute says cities could be turning asphalt into energy
When talk first emerged about building a series of nuclear power plants in
Alberta, a local blogger in favour of the plan made a harsh remark that
also bore some truth. Even if one of the power plants had a meltdown, he
said, the worst that could happen would be that Edmonton would be flattened
to the ground by a nuclear explosion, and the city would be reduced to
nothing more than a giant parking lot. In other words, he joked, it would
look exactly as it does now.
Jokes aside, if new research from the Worcester Polytechnic Institute (WPI)
in Massachusetts pans out, there might just be a silver lining to
Edmonton’s embarrassing asphalt surplus. According to Dr Rajib
Mallick, an associate professor of Civil and Environmental Engineering at
WPI who does research on the thermal properties of pavement, Albertans
might be able to avoid building any more power plants because they’ve
been standing right on top of a clean way of generating energy all
along.
The solar energy absorbed by streets and parking lots, Mallick says, could
not only prove to be a sustainable source of energy but could also reduce
the heat island effect that is often encountered in larger cities.
“We’d been scratching our heads and thinking about how to
reduce the urban heat island effect,” Mallick explains. “In the
meantime, a company called Novotech approached us and they said,
‘Well, is it possible to look at the capture of solar energy from
pavements?’”
The heat island effect, for the uninitiated, occurs when large areas
covered in asphalt and concrete absorb heat from the sun’s rays and
then slowly release it back into the air throughout the day. As the experts
from the Heat Island Group explain on their website, due to this
phenomenon, urban areas often experience weather two to four degrees warmer
than the surrounding countryside.
Due to this increase in temperature, heat-driven chemical reactions that
take place in the atmosphere occur more readily, and noxious gases like
nitrogen dioxide are produced as a result. The negative effect on air
quality in and around urban areas is considerable, and affected regions
often see the incidence of respiratory illness increase as well.
At the same time, air-conditioning costs and electricity demands also go
up, which puts a strain not only on the power grid but on the environment
as well.
It’s not just southern cities reeling from the effects anymore
either. Slowly but surely, more northerly cities are starting to see the
impacts as well. Even officials in Edmonton are starting to get worried
about it, with local city planners recommending that the city take steps to
reduce the heat-island effect in the downtown core.
However, municipalities are struggling to find effective ways of coping with the problem. In some cities, officials are painting roads and rooftops white or experimenting with other ways of making these surfaces more reflective. Other cities have resorted to planting thousands of trees in an attempt to shade the ground.
Mallick’s team, however, has taken the completely opposite approach:
they’ve actually been busy designing a pavement that absorbs as much
solar energy as possible. The best pavement that they’ve come up with
so far is made largely with the highly conductive rock quartzite. Applying
a super absorbent coat of paint to the surface of the road helps too.
The next step, once the heat is captured in this special asphalt, involves
transferring this heat from the pavement to a series of fluid-filled pipes
that Mallick refers to as the heat-exchanger system. From there, the energy
can be moved elsewhere and put to good use.
As Mallick points out, depending on how one decides to set up the
heat-exchanger system, the energy absorbed by the blacktop can be used for
all sorts of things such as generating electricity or heating and
sterilizing water. It could even be used to melt snow and ice in the
winter.
“There has actually been research in Holland for using this [kind of
system] to heat and then to store water at a relatively warm temperature in
an aquifer, and then to bring it back up in the winter time to melt your
snow,” Mallick points out.
Trent Bancarz, a spokesperson for Alberta Transportation, says he’s
intrigued by the idea, but he’s not entirely convinced that
it’s ready to be implemented just yet.
“As a concept it sounds interesting,” Bancarz says.
“However, it sounds like something that’s very much in its
infancy. It’s certainly not something we would be doing anytime soon,
though, I suppose as the technology gets more developed, who knows, it may
someday become practical to do it here.”
Mallick however, is much more optimistic, saying that he expects that it
will be less than a year before he implements his designs somewhere on a
much larger scale, outside of his lab. Actually, he’s already been
approached by several interested parties.
On the other hand, Mallick is quick to admit that his invention can’t
be used everywhere. Airport runways and busy highways that carry heavy,
fast moving traffic should probably be avoided for now, for safety reasons.
Other stretches of pavement, however, are likely fair game.
“The best application for this kind of system, as we see it now, is imagine a big hotel, or a big office or a Wal-Mart, which has a huge parking lot,” Mallick says. “If you can actually get that heat out of that parking lot, it can help you cut down your energy costs for that building.
“Does this means we have to do asphalt farming, as in set up asphalt parking lots in places that there aren’t any right now?” he asks, rhetorically. “No, absolutely not. But if you have a parking lot, and you have to live with it, well then use it!” V
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