Size: 10 to 50 MW

Demo plants built in the 80's

Two commercial plants in operation in Spain (10 and 20 MW) and 1 more under construction (17 MW + 15h storage)

Larger projects announced in the USA

This conversion technology, also called tower technology, uses big mirrors (heliostats) larger than 100m² which are almost flat and track the sun on two axes. The concentrated radiation beam hits a receiver atop a tower. The working fluid temperature depends on the type of fluid which is used to collect the energy and is within the range of 500 to 600°C.

The PS 10 of Abengoa in Seville is the only power plant of this kind in operation today. The nominal power output is 10 MW and it is designed with a northern heliostat field and saturated steam as working fluid in the receiver. The storage system is only designed to cope with transient situations. On the same site, a second plant of 20 MW nominal power and with a similar design has recently begun operation.

Another 17 MW plant owned by Torresol is under construction. It is located in the province of Seville, with a circular field type equipped with a molten salt receiver and has a storage capacity of 15 hours.

The size of these plants might be limited by the maximum distance of the last row of heliostats from the tower.

At this time, it is premature to already establish reliable cost/power ratios for this technology as the number of operational or ongoing projects is small, but it will not be too different from the parabolic trough plants. The land use is slightly less effective in the case of solar tower plants.

On the other hand this technology does not require a flat land surface like a parabolic trough plant does. A further advantage is the potential increase of the overall conversion efficiency (up to 20%) that can be achieved by raising the working fluid temperature.

The commercial confidence in this technology is growing as more operational plants are being built and consequently it will improve in the near future.

Hybridisation is feasible, but no commercial projects have been built so far.