TPT November 2016

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NOVEMBER 2016 61
G LOBA L MARKE T P L AC E
›For Mr Coy, one intriguing question is how the US might get
dangerous drivers off the road without first having to suffer
through a recession. Driverless cars would help, the authors
suggest. For example, Dr Winston observed, much mayhem
is caused by drivers with suspended licences. Driverless cars
would give these grounded miscreants a way to get around
without taking the wheel themselves.
Technology
Australian scientists, adepts at exploiting
solar power, achieve 97 per cent efficiency
for conver ting sunlight into steam
The “Big Dish” at the Australian National University (Canberra)
is made up of a concave surface of reflectors, directing
sunlight to a receiver suspended at the focal point. A new
receiver for the dish, designed and built by scientists at ANU’s
Research School of Engineering, is reported to have achieved
97 per cent efficiency for converting sunlight into steam.
Writing in New Atlas (formerly Gizmag), Michael Irving said
that the team that designed, built and tested the receiver
describes it as resembling a top hat, with a wide brim running
around the bottom of a narrower cavity that extends upwards.
The dish reflects sunlight onto water pipes that wrap around
the bottom of the receiver’s brim and up into the cavity,
heating the water to 500°C (932°F) and turning it into steam.
To minimise heat loss, the steam hits that peak temperature
at the deepest part of the cavity, so that any heat that is lost
can feed back into the pipes around the brim.
“When our computer model told us the efficiency that our
design was going to achieve, we thought it was alarmingly
high,” Dr John Pye, of the Research School of Engineering,
told Mr Irving. “But when we built it and tested it, sure enough,
the performance was amazing.” (“Solar Thermal Record Sees
97 Percent Conversion of Sunlight Into Steam,” 22 August)
New Atlas distinguished photovoltaic solar panels, which
absorb sunlight and direct-convert it into electricity, from the
concentrating solar power (CSP) system in use at ANU –
which reflects sunlight from a wide area and focuses it in on
a small receiver. As the receiver heats up, water inside turns
into steam, driving a turbine to generate electricity. Rather
than storing that power in potentially costly batteries, the
thermal energy is stored in molten salts so that water can
be added to create steam (and subsequently electricity) long
after the sun goes down.
Dr Pye said that the ANU design could result in a ten per cent
reduction in the cost of solar thermal electricity. “Our aim,” he
told Mr Irving, “is to get costs down to 12 cents per kilowatt-
hour of electricity so that this technology will be competitive.”
Dorothy Fabian, Features Editor (USA)