PHOTON: Solar PV and Solar Thermal Come Together in a Pioneering Project
This initiative intends to improve the efficiency of central-tower solar thermal plants and achieve unheard-of power output.
Sometimes, while crossing a plain by car, we can see what looks like a totem surrounded by a legion of adorers. It is one of the least common, but with great potential, renewable energies: solar thermal plants.
Surrounded by thousands of mirrors, technically called heliostats, they concentrate heat in a single point, achieving temperatures north of 1000 C degrees. This heat is used to warm a salt-based fluid that, once liquified, is pumped into a heat exchanger. Once inside that deposit, it transfers heat to water to produce steam and move a turbine. Although most of these plants are based on simple technologies such as steam turbines, finding the optimal settings and materials is a real engineering challenge. Thus, efficiency is still a pending issue.
Within the current alternatives available, which include parabolic trough concentrators and Stirling discs, central-tower solar plants are still the most promising technology. PHOTON, an innovative technological project codeveloped by ACCIONA Industrial, could mean another step in the optimization of the current systems.
The aim of PHOTON is to improve the efficiency of these solar plants by 10-15% with facilities that provide an electrical output between 50 MW and 150 MW. The latter would prove to be truly revolutionary as the main issue with this technology is its lack of scalability. This is due to the high energy loss incurred by the heliostats placed further away from the main tower. Therefore, one of the main areas of development in the project is the improvement of heliostats by using a hybrid wireless solar-PV system. In this way, each heliostat will have the ability to self-calibrate by using its own energy. The new reflective systems are expected to be lighter and easier to install, as the will not require any cables or foundations. Currently, half of the development cost of a solar thermal plant goes to the heliostats. Any improvement in these components is thus bound to improve the profitability of these projects.
Another goal for PHOTON is to develop an optimized central tower model by fulfilling these requirements: obtaining the same energy output with a smaller receptor (by reducing the exposed surface and the receptor’s costs) or increasing the energy output while maintaining the size of current receptors.
Besides ACCIONA Industrial, the “PHOTON: High-performance solar thermal power plants based on hybrid Solar-PV heliostats and tailormade collectors” project has several leading partners, including Aalborg CSP (Denmark), Applied Research Institute F (Lithuania) and Modern E-Technologies (Lithuania). The EUREKA network and the European Commission, as well as the Spanish CDTI (Centre for the Development of Industrial Technology) are funding PHOTON with a two million-euro budget. The new prototypes will enter the testing stage by late 2019.
ACCIONA solar thermal around the world
Currently, ACCIONA Industrial is building its first solar thermal plant in Latin America, the 100 MW Cerro Dominador project, in collaboration with Abengoa. ACCIONA Industrial is also working on a parabolic trough plant in Kathu (South Africa) for Engie, partnering with Sener. This would be one of its latest thermal solar power plants together with the already completed power stations in Bokpoort (South Africa) and Noor I (Morocco).
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