www.thenational.ae
October 22. 2009
Dust and haze in the coastal regions of Abu Dhabi emirate significantly reduce the efficiency of the world's cheapest solar energy technology, research from the Masdar Institute shows. That may give the more costly photovoltaic (PV) panels an edge in the race to find the country's renewable energy source to help generate the Government's target of 7 per cent of the emirate's electricity by 2012. Masdar, the Abu Dhabi Government's clean energy fund and the institute's parent company, is testing a number of options including solar and geothermal energy to decide which will take the lead role in powering Masdar City, the zero-emissions development at the edge of the capital.
Concentrated solar thermal power, in which mirrors focus the heat of the sun to boil water and turn a standard generator, should be the cheapest solar option. But computer modelling at the Masdar Institute shows that in Abu Dhabi, where dust and haze diffuse sunlight for many months, solar thermal is significantly less efficient, said Sgouris Sgouridis, an assistant professor at the Institute. "You don't get the efficiencies you expect out of the concentrated solar thermal," he told a gathering of green-energy experts, hosted by the Dubai-based Gulf Research Centre.
"They are around 15 to 20 per cent off [the ideal efficiency level] and that makes the consideration of photovoltaics much stronger in this region." The calculations were for areas around Masdar City, Dr Sgouridis said, and did not apply to inland regions with reduced humidity. solar thermal, he said, "is certainly cheaper but in some cases you might want to go with the PV. A dirty PV panel works; a dirty [concentrated solar energy] system doesn't work at all."
Solar thermal is vulnerable to haze because it relies on concentrating the direct radiation of the sun, while for PV, it matters far less how sunlight strikes the panel, said Francesco D'Avack, a solar analyst at New Energy Finance, which serves as a clearing house for data on renewables. "For solar thermal you need direct radiation, and if you have haze you don't have direct radiation," Mr D'Avack said. But in the right environment, solar thermal plants have a significant advantage over PV for utilities and other large power producers, because once the plant is heated and starts producing power, it is less susceptible to brief cloud cover or other slight disruptions to direct sunlight.
"For solar thermal the quality of the power is much higher and you have dispatchability," Mr D'Avack said. "They have much smoother power output." Dr Sgouridis stressed that the Masdar Institute's findings on conditions in Abu Dhabi were still under peer review and had no direct link with the parent company's investments in either type of technology. The firm is tendering a project to build a 100-MW solar thermal plant at Madinat Zayed in Al Gharbia, with a construction contract originally due to be awarded in the third quarter. It has recently been reported that the project site had been moved, delaying the tendering process. Masdar declined to comment on the project yesterday.
The firm is also investing significantly in PV solar panels, in which sunlight is directly transformed into a current of electricity. Masdar operates a 10mw solar array on the city site, and has opened a plant in Germany to begin producing its own panels. Construction on a second plant in Abu Dhabi will start next year. Dr Sgouridis said the latest model for Masdar City showed PV would supply between 50 and 60 per cent of the development's energy needs. About 26 per cent would come from solar thermal, he said, with the balance coming from a range of sources including geothermal, waste-to-energy, and thermal tube collectors, which use the sun to heat water and directly power cooling systems.
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