NOVEMBER 2019
No special materials are needed for
the mirrors – because they reflect the
light they remain cool. For the collector,
refractory ceramic bricks, as used inside
kilns, are employed to withstand the
high temperatures. The light beam is
focused on the ceramics, with whatever
the process is being used to heat, such as
steam or cement, placed inside.
Gross has three ambitions for
application of the technology: first, for
customers who want to produce steam
for industrial processes; second, for
processes such as cement manufacture;
and third, to split water to create green
hydrogen.
For industrial use, the next stage will
be to integrate CSP into manufacturing
processes. Cement manufacture, which
alone accounts for over 7 per cent of
global carbon dioxide emissions, is
currently undertaken in rotary kilns.
The process would have to be adapted to
integrate CSP.
Gross says the initial focus would be
on the first stage, calcining, because this
is where most of the energy is used. In
calcining, limestone (calcium carbonate)
is heated to between 900-1000°C to drive
off carbon dioxide, leaving calcium
oxide. Gross envisages that it would be
achieved by carrying limestone to the top
of the tower via conveyor belt in batches,
for heating in a form of oven.
Alternatively, steam would be heated
to 1000°C and brought to ground level
in insulated pipes (with only a 10-20°C
temperature drop) and either used to
heat the materials directly or used in a
convective heater to heat an oven.
The important point, Gross stresses,
is that Heliogen’s system allows steam to
be heated to the required temperature at
low cost, and it can then be transferred to
April 2020 / www.theengineer.co.uk 38
view of having the best sites for sunlight, or the most suitable
processes, and is in negotiations to sign them up.
Most would like to run their processes 24 hours a day, he
added, but this can be made possible through thermal storage.
Again, this can be achieved cheaply by blowing air or steam
heated by the solar collector over refractory bricks, from which
the heat can be recovered overnight.
Gross describes green hydrogen as “the holy grail”. This
presents an additional challenge because it would need the
target to withstand 1500°C. Then the hydrogen would have to be
compressed and transported.
Currently, using solar photovoltaic electricity to electrolyse
water is uncompetitive with reformation of methane for
producing hydrogen. However, Gross believes CSP will be more
efficient then PV because it uses heat from the sun directly
rather than converting it to electricity first, and again the
process will be capable of continuing overnight.
He sets out an ambitious timescale for practical
applications, expecting to see the technology in use with steam
customers this year, integration into processes such as cement
or steel production next year, and for hydrogen production by
2022.
Installing CSP does not entail a large construction
project. Only the tower, around 40m, would need significant
construction skills. The mirrors do not need any special
foundations and could be installed by unskilled labour. In time
they will be powered by solar panels and connected by wi-fi,
eliminating cabling.
From the point of view of funding, Heliogen already has a
number of well-known investors such as Bill Gates on board.
More have come forward since the launch. Gross is confident
the company has the backing it needs. “We’re really well
financed,” he said, “we can easily take it all the way to the
market.”
Heliogen’s system could be used for industrial heat or to produce green fuels
COVER FEATURE: ENergy
wherever the heat is needed.
“The next stage is integrating with
actual processes, and that is work we’re
going to do with customers,” he said.
Following November’s
demonstration, Heliogen has been
approached by “over 1,000” prospective
customers, though the company is not
able to announce any names yet.
“We have some customers who just
want steam for an industrial process – we
can sell to them right away,” Gross said.
Other prospective clients are offering
to work together on the R&D needed
to adapt and integrate CSP into their
processes. Gross is keen to combine
Heliogen’s expertise with that of
industry partners on their processes.
It is in a position to choose those who
are most promising from the point of
Global installed capacity of
concentrated solar power increased
by 11% to reach 5.5GW during 2018,
it was reported in June last year.
Spain accounted for almost half of
the world’s capacity, at 2,300 MW,
the US following with 1,740 MW. There
is significant interest in North Africa,
the Middle East, India and China.
The CSP market was in its early
years dominated by plants based
on parabolic troughs to focus the
sunlight, but over the last decade
the use of a central power tower has
been favoured in new plants because
it allows higher temperatures (up to
565oC), promising greater efficiency.
The heat is generally used to
power steam turbines to generate
electricity.
At the end of 2018, 2GW of
concentrated solar power projects
were under construction in ten
countries in Africa, Asia, the Middle
East and South America, with most of
the capacity being built in the United
Arab Emirates (0.7 GW) and China
(just over 0.5 GW). All but 3 of 23
plants under construction planned to
include thermal energy storage (TES),
mostly using molten salt as a heat
storage and transfer medium. The
molten salt acts as the heat source
for power generation, which can
continue day and night.
Nearly all the commercial CSP
capacity under construction at
the end of 2018 was in emerging
countries. No new capacity has
entered commercial operation in
Spain since 2013 and in the United
States since 2015.
The Chinese government
launched its first batch of 20
demonstration CSP projects in
September 2016, and seven of the
20 were connected to the grid by
January 2020. The other 13 were
reportedly incomplete and some
had been cancelled. The connected
projects are all rated at either 50MW
or 100MW. Two are parabolic trough
systems and of the rest all but one
use towers, with molten salt energy
storage.
The first CSP tower plant in
Latin America, Cerro Dominador,
in the Atacama desert, recently
raised its 2,300t receiver to the
top of its 250m tower in a weeklong
operation, in one of the last
stages before being ready to enter
operation. The project uses 10,600
mirrors to concentrate the sunlight,
again with molten salt as the
storage medium.
CSP AROUND THE WORLD
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