It is nice to
see this addressed. Yet what is
described here is likely going nowhere.
I do think that the shifting of dense cold water in the ocean to the surface
as a self-powering flow is far more promising.
Yet we are
surrounded by this radiation and converting it into electron flow is desirable.
I have speculated on using a low
temperature band gap device, however that could be made to convert all that
obvious potential into electricity, but have really gone no further. I just think we need to try.
Here it is been
looked at. It is noteworthy that the
Carnot Cycle applied to most of our heat engines leave us with spent hot water
at boiling point. Reducing boiling point
using reverse refrigeration or the reverse Rankin Cycle Engine can produce an
additional 75% brake horse power to bring the temperature down to our body
temperature but remains largely unapplied.
Thus taking a
room temperature regime and knocking it down to a cryogenic temperature while converting
a large chunk into kilowatts is certainly attractive as an idea. It is just not a project that anyone would
want to devote a lifetime to. It is
easier to be inefficient.
Is Earth's
infrared radiation a potential energy source?
At any given moment, our planet bleeds 100 million
gigawatts of infrared radiation back into space. Needless to say, converting
this wasted heat to a renewable energy source would be a sure-fire game
changer. Physicists from Harvard University may have just figured out how to do
it.
Our Earth, which is heated by the sun, is much
warmer than the frozen space that surrounds it. This creates a heat imbalance
that could be transformed into direct-current (DC) power. But making this
happen is considerably easier said than done.
"It's not at all obvious, at first, how you
would generate DC power by emitting infrared light in free space toward the
cold," noted principal investigator Federico Capasso in a statement. "To generate power by emitting, not by
absorbing light, that's weird. It makes sense physically once you think about
it, but it's highly counterintuitive. We're talking about the use of physics at
the nanoscale for a completely new application."
Capasso, along with his colleagues Steven Byrnes and
Romain Blanchard, have proposed two designs for a device they call an emissive
energy harvester (EEH). Once developed, they would convert infrared
radiation (IR) into usable power. And somewhat paradoxically, they would run in
reverse.
The first type of EEH is comparable to a solar
thermal generator. It would consist of a "hot" plate at the same
temperature as the Earth and air, with a "cold" plate on top of it.
Facing up towards the sky, the cold plate would feature a material that cools
by very efficiently radiating heat. The resulting heat difference between the
plates could generate a few watts per square meter — day or night. And in fact,
the researchers are basing these measurements on a case study conducted at a
location in Larmont, Oklahoma. The researchers admit that keeping the cold
plate cooler than the ambient temperature will be a challenge, but it
illustrates an important principle — that difference in temperature can
generate work.
"Solar panels for heating and cooking are already
used in much of the world," he says. "You could easily couple that to
the (infrared) harvester."
As for the second device, it would rely on
temperature differences between nanoscale electronic components (namely diodes
and an antenna) rather than a temperature that can be felt with touch.
"If you have two components at the same
temperature, obviously you can't extract any work, but if you have two
different temperatures you can," says Capasso. "But it's tricky; at
the level of the electron behaviors, the explanation is much less
intuitive."
Unfortunately, the technology to build these devices
doesn't exist — at least not yet. But the groundwork certainly makes it look
promising.
"Now that we understand the constraints and
specifications, we are in a good position to work on engineering a
solution," adds Byrnes. In fact, he envisions a sheet printed with
thousands of tiny IR-harvesting rectennas that could be laminated on a solar
panel or integrated into a solar water heater.
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