The view from Spain's solar power tower

edition.cnn.com
March 10, 2010

(CNN) - - Cresting the brow of autovia A-49 in Andalusia, 10 miles outside of Seville, the world's first commercial solar "power tower" appears on the skyline like a giant obelisk. Even on an overcast morning the sun's rays are so intense they illuminate the water vapor and dust hanging in the air to create a giant lattice of white lines that appear to emanate from the eye of the tower. The tower itself is 115 meters high - - the height of a 14-storey building - - and, bathed in intense white light, the overall effect resembles nothing so much as a religious object.

Valerio Fernandez is director of operations for the PS10 platform and its neighbor, PS20. That means he is responsible for the 624 giant mirrors - - or heliostats - - that reflect the sun's rays into a receiver located at the top of the tower. Each heliostat measures 120 m², which gives the entire heliostat field an area of 75,000 m². On a sunny day this can produce up to 11 MWs of energy, enough to power a town of 6,000 homes, such as the neighboring community of Sanlucar la Mayor.

But Fernandez isn't satisfied. "Our goal is to operate more than 300 MWs for the year 2013," he told CNN. "So in a few years we will be constructing and putting into service new and larger plants in order to provide huge amounts of solar renewable energy to this area of Spain."

As Valerio explains the concept ("We just reflect light into the receiver, which is basically a boiler where we generate steam, and then we drive this steam through a turbine in order to move a generator and generate electricity,") we are aware of the faint whirring of 600-odd motors that allow the heliostats to track the sun on two axes and concentrate this radiation on the tower.

The effect is incongruously life-like; hundreds of enormous mirrors all turning themselves towards the sun like a field of giant metal sunflowers. We decide to get a better view. Putting aside fears that we will be fried like ants under a magnifying glass, we ascend the tower. From here the vista is even more spectacular: a glittering blanket of more than 600 mirrors winks up at us from the sun-scorched earth.

Here is also where the receiver is located. Composed of four, vertical 5.5 meter by 12 meter panels, arranged in a semi-cylindrical configuration inside a cavity with an opening of 11 meters by 11meters, the receiver is designed to deliver 55 thermal MWs of saturated steam at temperatures of 257 Celsius. More than 92% of the sunlight reflected at the tower is converted into steam.

To the west lies an even larger tower surrounded by more mirrors. Although currently closed for maintenance, when PS20 is fully online again in April it will be the world's most powerful solar power tower. With a power capacity of 20 MWs, double that of PS10, PS20 should produce enough clean energy to supply 10,000 homes. Valerio is understandably optimistic. "We want to get as much of our energy from solar power as we can because it's renewable, it's clean and its contribution to combating climate change is very important," he said. "That's why we are working to develop this technology as much as possible so it can have a large role in the future."