India, with plans to install 550 MW of CSP by 2013, could emerge a major player in this area.

Concentrating solar power (CSP) is emerging as a viable alternative. The German summer is usually cloudy and not warm enough to generate grid quality electricity from solar power. But this has not deterred technologists and researchers there to come up with high efficiency solar technologies suitable for countries in the so-called sun belt, such as India.

Solar photovoltaic (PV) technology has been used for long to generate power from the sun. But its use has remained limited because of its low efficiency and other constraints. Now, concentrating solar power (CSP) is emerging as a viable alternative.

Unlike PV cells which are flat, CSP involves the use of parabolic mirrors in long troughs, which concentrate solar irradiation into a centrally placed special tube which absorbs radiation. The heat generated into the tube is then used to produce electricity.

One of the biggest benefits of CSP is its ability to store thermal heat which ensures continuous supply of power even when the sun is down and when it gets cloudy. Globally, the technology is being used only in the US and Spain at just a few locations. India, with plans to install 550 MW of CSP by 2013, could emerge a major player in this area.

The core of a CSP plant is the special tube placed at the focal point of parabolic mirrors. The mirrors have a motorised system that enables them to keep tracking the sun. Inside the glass tube is a steel tube with absorber separated by vacuum insulation. The ceramic metallic tube contains synthetic oil which gets heated up to 400 ° Celsius. The oil flows into a heat exchanger which generates steam, which in turn, is used to generate power using conventional steam turbines.

"The receivers have to achieve maximum solar absorption and at the same time minimal emmmission of heat. The surface of the glass tube remains cold, while the temperature in the steel tube could go up to 400 ° Celsius. And materials of both the tubes have to withstand the pressures during the lifespan of a power plant," Christoph Fark, managing director of Schott Solar CSP, said. Schott and Siemens are the only two companies in the world that manufacture these glass receivers.

India had planned to set up a 35 MW plant based on CSP in Rajasthan way back in 1994, but the project was postponed indefinitely because no qualified contractors were able to submit a bid. Now, of course, the situation has changed.

The Jawaharlal Nehru National Solar Mission recognises CSP as a key source of renewable power. The ministry of new and renewable energy is setting up a string of demonstration projects. A 10 mw CSP plant is already under construction near Bikaner by ACME, a private company.

Ministry officials said CSP could be an attractive option for the country, given the fact that large areas of northwest India fall in the high radiation zone. The costs can be brought down if concentrating mirrors and receiving tubes are manufactured locally.

Schott officials said the company’s glass tubing manufacturing facility at Vadodara can be upgraded to manufacture receivers if required.