TPT November 2016

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)

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N OVEMBER 2016