IEEE Spectrum November, 2014 - 15

Yan Yan, GuodonG Xie, and alan Willner

nEwS

went to press in October. Statnett and its
European grid partner, Dutch-German
firm Tennet, foresee charging up the
1,400‑MW NordLink in 2018. The pair
of Norway-U.K. cables, a joint effort of
Statnett and London-based National
Grid, is slated to start by 2020.
There should be many more cables
to come if European countries make
good on official goals to eliminate carbon emissions from power generation by
2050. The German government's Advisory Council on the Environment, for
example, concluded in its influential
2011 report that an optimal zero-carbon
power system for Germany would need
more than 40 gigawatts of interconnection to Norway. That system, the council
projected, would deliver power at a very
affordable 6 to 7 euro cents per kilowatthour. Without Norwegian storage, power
costs would rise to 9 to 12 euro cents per
kilowatt-hour.
Ånund Killingtveit, a professor of
hydraulic and environmental engineering at the Nor weg ian University of Science and Technology, says
Norwegian hydropower is up to at
least part of the task. Killingtveit led
a five-year, US $5.7 million research
program on hydropower balancing,
which showed that existing hydropower reservoirs could "fairly easily"
move about 25 GW of energy in and
out of storage without damaging the
environment-five times as much as
they currently manage. The key, he
says, is installing pumps to shift water
from one reservoir to a higher one
nearby, thus actively storing power
rather than just deferring production.
If there is a limit to Norway's energy
storage potential, it may ultimately be the
country's own grid. Statnett has begun
a 10-year, $8 billion to $10 billion grid
upgrade, but it factors in only 3.5 GW of
additional power from the three cable
projects. The question may be how many
power lines the Norwegians will accept to
smooth Europe's departure from fossil
fuel power. -peter fa ir ley

TwisT and shouT
spiraling radio beams send data
at 32 gigabits per second

A team led by engineers at the University of Southern
California has sent multiple channels of data over a single
frequency by twisting them together into a beam resembling a piece of fusilli pasta. By combining several polarized
beams carrying information into a single spiraled beam, the team was
able to send up to 32 gigabits per second across 2.5 meters of open air,
a rate around 30 times as fast as an LTE wireless connection.
The high data rate was made possible through a technique known as
orbital angular momentum (OAM) multiplexing, says USC electrical engineering professor Alan Willner, who partnered with researchers from
the University of Glasgow and Tel Aviv University on the experiment.
A property of electromagnetic waves first identified in the 1990s, OAM
can be harnessed to let multiple channels of information ride along a
single frequency. "I could have a wave that twists slowly and one that
twists a little faster, and those waves are now orthogonal to one another,"
Willner says. "If you put them together and send them spatially colocated through the same medium, you have doubled your capacity."
Willner and others have previously demonstrated the twisting technique with beams of light, reaching
rotAtiNg rADio: Waves of the
data transmission speeds of 2.56 terasame frequency won't interfere with
bits per second through the air in 2012
one another if they are given different
and 1.6 Tb/s over optical fiber in 2013.
degrees of orbital angular momentum.

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Table of Contents for the Digital Edition of IEEE Spectrum November, 2014