On a summer day, the Negev, the desert that constitutes over half of Israel, shimmers like gold. It might have you reaching for your sunglasses and hat, but Professor David Faiman, director of the Ben-Gurion National Solar Energy Centre, and chairman of the Department of Solar Energy & Environmental Physics at Ben-Gurion University?s Jacob Blaustein Institute for Desert Research in Sde Boker, will tell you that the density of solar energy that reaches the earth is ?very low?. ?To generate energy equivalent to a barrel of oil, a square metre of the earth will need a whole year of sunlight. And the world uses up 200 million barrels in a day,? says Faiman, who lives in Sde Boker in a house largely powered by solar energy, and seems at ease in the afternoon heat.
Israel, which has few natural energy resources, is located at a latitude of 30? N, where the annual incident solar irradiance is about 2,000 kWh per sq m. ?When I came here in the 1970s, I was a theoretical physician. I had no idea about solar energy,? says the former physicist, who is now Israel?s representative to the Task 8 Photovoltaic Specialist Committee of the International Energy Agency. To Faiman, it made sense to approach power generation from two angles?making better photovoltaic cells and efficiently tapping solar thermal energy. ?Here, in Sde Boker, we can test under natural conditions cells that are normally tested only in a simulated lab environment. We are working on characterising the properties of new types of solar cells,? he says, pointing to rows of solar panels glinting in the sun.
Large-scale solar electrification, for long, has remained an expensive dream the world over. But perhaps not anymore. In a fenced-off part of the facility in Sde Boker is a huge dish pointing up at the sun like an outstretched glass bowl. ?It?s the world?s largest solar dish, with a collector area of 400 sq m. It has parabolic mirrors and secondary mirrors to concentrate sunlight on to a 1 sq m solar panel. When a mirror is used to concentrate solar radiation into a small area, as much as 2 kW of electric power and 5 kW of thermal power could be generated, and the latter could be used to heat several hundred litres of deionised water. Zenith Solar uses such a similar concentrated photovoltaic system to generate power at 70 per cent efficiency, at a cost of two to three cents per kWh,? says Faiman, chief scientist and adviser to the company, adding that due to the high concentration of solar radiation, such units need to have safety and containment utilities.
Zenith Solar?s website elaborates: ?The concentration factor, denoted by X, is a measure of the increased light intensity on the semiconductor cell. X equals approximately the area of the optic collector divided by area of the semiconductor solar cell. ZenithSolar system is designed to a concentration factor of 1000 X. In conventional CPV systems, the excess heat generated in the solar cell needs to be removed to avoid damaging the cell and to maintain high efficiency of electricity conversion. ZenithSolar utilises the heat generated at the solar cell receiver to provide usable hot water heating, improving overall solar power conversion efficiency to 75 per cent.? With most solar power systems reaching a maximum efficiency of 50 per cent, this technology might well find a place in the community power plants of the future.