ABB is supplying a comprehensive power and automation solution for one of the world’s largest solar thermal power plants – a solution that includes uniquely accurate control equipment to enable the 1,248 parabolic troughs to capture maximum energy from the sun.

The solution encompasses an extensive array of power and automation products and systems for the 100-megawatt (MW) Extresol 1 and 2 solar thermal power plant and solar collector field in Extremadura, western Spain.

Extresol 1 and 2 will each produce 50 MW of electricity from a vast solar field of parabolic trough collectors covering more than 510,000 square meters, equivalent in size to around 70 soccer fields.

Clean power for 60,000 homes
Together, both power plants will generate enough electricity to provide 60,000 Spanish homes with clean energy and avoid 298,000 metric tons of CO2 emissions a year. Extresol 1 is scheduled to start operation at the end of 2009 and Extresol 2 six months later.

Along with the 100-MW Andasol 1 and 2 solar thermal power project in neighboring Andalusia – for which ABB has also supplied an extensive power and automation solution – Extresol is one of the largest solar energy projects in the world. Both projects are jointly owned by Sener and Cobra, two Spanish engineering and construction companies.

A solar field of parabolic troughs at Andasol 1 about six months before completion.

ABB’s comprehensive scope of supply to Extresol includes control systems for the power plant and parabolic trough collectors, instrumentation, motors, drives and low-voltage products, as well as substation power equipment for delivering the energy safely and reliably to the national power grid.

Advanced positioning
The solution also includes AC500 programmable logic controllers equipped with an advanced solar positioning algorithm especially developed by ABB for parabolic trough collectors and solar trackers. The algorithm enables the collectors to follow the passage of the sun to within 0.03 degrees of error, thereby absorbing the maximum amount of energy at all times.

Each of the 1,248 collectors is equipped with an AC500 PLC. Besides their outstanding accuracy, the PLCs are certified to withstand the demanding operating conditions of extreme heat during the day and low temperatures at night.

High-efficiency power generation
Parabolic trough collectors are the most efficient and widely used method for large-scale solar thermal power generation. The collectors are parabolic mirrors that reflect and concentrate the sunlight onto tubes containing heat transfer fluid. The fluid is then used to heat steam in a turbine to generate electric power.

ABB has played a leading role in the development of solar concentration and parabolic trough technology since the 1990s when it developed a distributed control system for the world’s first test facility on behalf of the International Energy Agency at the Plataforma Solar de Almería (PSA) in Spain. The PSA is Europe’s leading test facility for solar concentration technologies.