BUSINESS NEWS
cshoimneg rays
37 April 2020 / www.theengineer.co.uk
g
Heliogen’s mirrors
are controlled
using computer
vision and can be
focused on an area
about the size of a
basketball hoop.
This facilitates
extremely high
temperatures.
37
Heliogen achieves this using
computer vision and bespoke software.
Cameras on the tower are pointed at the
entire mirror array, capturing video at
30 frames per second. Computer vision
is used to analyse the position of the
edges of the mirrors and the angles of
refl ection off each, and to make minute
adjustments to the position of each 30
times a second. Each mirror receives
commands via an ethernet connection
and is fi ed with two brushless electric
motors (for minimum maintenance) to
make the continuous small adjustments.
“We aren’t relying on a survey position
or on anything predetermined,” said
Gross. “We’re just looking at the exiting
rays coming off the mirrors to the tower –
the exact thing we care about.”
The reason that this has not been
done before, Gross said, is partly because
suffi cient processing power was not
available, until NVIDIA GPU processors
came down in price suffi ciently,
making it possible to do the complex
computations in real time.
Secondly, major software
development in artifi cial intelligence,
image recognition, and computer vision
analysis – the company’s core intellectual
property – was needed. Though Heliogen
only recently broke cover, it was set up in
2013, and Gross reckons the equivalent of
40 to 50 person-years of work went into
software development, culminating in
November’s demonstration.
Not only were unprecedented
temperatures reached, the cost of the
system is lower. The mirrors do not have
to be stiff , or meticulously positioned,
both of which add to costs. “Our system
is closed loop, like tracking the mirrors
with your eyes open. Other systems are
running blind, positioning the mirrors
based on a look-up table,” Gross said. Any
ground se lement, for example, would
be compensated for automatically.
The mirrors are made of ordinary
glass with a silvered backing, protected
against the elements by a layer of
copper and a coating of outdoor paint
on the back. The glass is only 3.2mm
thick – as thin as possible for maximum
refl ectance, but thick enough to
withstand a hailstorm.
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