Largest solar towers will be in California

Two of the world's leading concentrating solar power (CSP) companies have joined forces to build the 500 MW Palen solar complex in California. Abengoa and Brightsource energy have signed an agreement to jointly develop, build and operate what will be the world's two largest solar power towers. As joint partners, they will work together to permit and finance the project. Abengoa will build the plants as the engineering, procurement and construction contractor, and will lead the operation and maintenance of the plants once online. BrightSource will provide the solar field technology and plant design.
The Palen project consists of two 250 MW units located in a Department of Interior Solar Energy Zone in Riverside County, California. Together the plants will produce enough electricity to prevent the emission of about
17 million tons of CO2 over their life cycle. With permitting and development under way, construction is expected to begin at the end of 2013 and will create more than 2000 jobs in all. The solar plants are expected to come online in 2016. They will be similar in general design to the Ivanpah site (pictured) currently under construction in the Mojave desert, California.
The Palen site had already received authorisation from the California Energy Commission (CEC) for construction and operation of an unspecified 500 MW solar thermal project, but in December 2012 BrightSource filed an amendment to the existing permit seeking authorisation to deploy solar power tower technology.
Converting the project to this technology, coupled with low impact design, will have the effect of significantly reducing the environmental impacts that would have occurred under the original permits. The new design will reduce the project footprint by 13 %, from 4366 acres to approximately 3800 acres, and use 50 % less water by deploying a dry-cooling technology.

Solar field design
Solar power towers generate power by using plane mirrors - heliostats - to concentrate solar heat on a tower-mounted collector/heat exchanger system, ultimately creating high temperature steam to turn a turbine. At the heart of the system is optimisation software and a control system that allow for the creation of steam at a suitable temperature. The steam is then used with conventional power plant turbo-generators.
Each unit at Palen will be centred on a 750-foot tall tower that allows for a high concentration of heliostats. This arrangement significantly reduces the amount of land required to produce the same amount of energy - up to 33 % less than typical photovoltaic farms. Additionally, the design places mirrors on individual poles placed directly into the ground without concrete foundations, allowing the solar field to be built around the natural contours of the land, the retention of native vegetation under the mirrors, and the avoidance of areas of sensitive vegetation.
Abengoa and BrightSource are both experienced developers of solar tower technologies and are pooling their collective experience. Abengoa operates four solar towers in southern Europe, including the first in the world to come into commercial operation (PS10, in Spain, in 2007) and is currently building a fifth tower in South Africa. The company currently has 743 MW of installed solar capacity around the world and 910 MW under construction. It is one of the few companies that builds and operates both parabolic trough and tower CSP plants. BrightSource has solar towers in operation in Coalinga, CA, and in the Negev Desert and its technology is currently being deployed at the 377 MW Ivanpah solar electric generating system, the largest solar tower facility under construction in the world.