CSP Today talked to Soledad Garrido, SENER’s Industrial Engineer and commercial responsible of the solar tracker.

CSP Today: SENER has developed a new product: a high accuracy two axes solar tracker for CSP and CPV technologies. Can you provide an insight what factors were taken into consideration in developing this solar tracker? What were the main challenges in doing so?  

Soledad Garrido:
As an engineering company, all SENER efforts in solar energy are focused in introducing high quality products and technologies with the aim of making this renewable energy an economically competitive option and a real, viable, ecological and sustainable alternative to traditional power sources.

SENER’s tracking technology has been specially developed for the demanding requirements of High Concentration Photovoltaic (CPV), Central Tower Receiver Heliostat and Stirling Dish. All these technologies require minimum pointing errors (pointing accuracy better than 0.1º) under demanding operating conditions with which energy production is guaranteed and, therefore, the profitability of the installation.
Therefore, the tracking system must maintain its performances during the total life cycle of the plant (about 25 years) with no degradation, operating in different open-air environments (desert, dust and sand, snow, rain, etc.), under demanding wind conditions and with minimum production, installation and maintenance costs. All this factors were taken into account and as result SENER developed a new high quality product unique in the market.

The key point of SENER’s solar tracker and heliostat is its high performance patented drive and its structure tailor-made design. The heliostat and tracker’s drive is SENER own product, designed, patented and manufactured by the company, that has as main features its compact design: integrating in a single housing the whole set of the azimuth and elevation actuator, which makes it a high reliability, high performance, remarkable rigidity and low maintenance product, and guarantees precise and reliable solar tracker operation.

Applying its expertise and know-how in high accuracy Actuation and Control Systems, SENER is able to produce a unique high performance drive in the market. SENER manufactures under ISO 9001 ensuring that the drive units are built under tight quality controls and guarantees that each drive accomplishes the specifications and ensures the performances of every drive; Also, SENER drive is tested by accelerated life tests in order to guarantee the right operation all along the 25 years of the plant’s useful life.  

CSP Today:The tracker's pointing mechanism is SENER own product, designed, patented and manufactured by the company. Can you elaborate on how this has resulted in improved efficiency, low maintenance and overall reliable solar tracker operation?  

Soledad Garrido:
SENER’s solar tracker and heliostat are characterised by the large surface capacity and an excellent pointing accuracy better than 0.1. Extensive research by our engineers has resulted in unique products in the market, capable of carrying 120 square metres CSP heliostats and PV flat panels, and 85 square metres CPV solar trackers.

On one hand, this large area covered maximizes the energy production and reduces the need of the number of solar trackers and heliostats, thus decreasing dramatically the plant’s civil works, material and maintenance costs. SENER’s structures are designed to make the levelling of the CPV modules and to adjust the shape of the reflecting surface of the heliostat easy, which is mandatory and has a great impact on installation costs.

On the other hand, pointing accuracy is guaranteed even under strong wind conditions, which is critical to the functionality of CSP and CPV.

Regarding CSP applications, heliostats reflecting solar radiation towards the tower’s central receiver use this high accuracy tracking system to direct the mirror surface according to the control strategy, position of the sun and distance to the tower. Likewise, the Stirling dishes that concentrate solar radiation in a focal point need to carry out constant pointing. CPV modules reduce the amount of semiconductor material used compared to traditional flat panels, enabling the use of more efficient material.
 
CSP Today: Regarding various CSP technologies be it parabolic troughs, dish-Stirling engine systems or power towers, it is said that the technical feasibility of these three technologies has been proven. However, the commercial viability is still to be demonstrated for dish-stirling and solar power systems. Improvements have been developed during the last decade for these two technologies, but experimental results from commercial plants are still missing concerning dish-stirlings and solar towers. How do you assess the situation going forward from SENER's perspective?  
 
SENER’s Communication Department:

SENER has always been a pioneer engineering company that has launched innovations in fields such as Space, Marine, Civil... and also in Power and Process. The company has been present for years in the renewable energy field and SENER’s capacity for anticipation in the Concentrating Solar Power field, as well as its ambitious technological development programme, have always been directed at obtaining electricity from solar energy on a large scale, and the company is therefore the leader in cost efficient solar innovations. In this sense, SENER offers practical solutions that can be seen and tested, being Gemasolar the seventh solar project SENER has developed.
 
SENER started working in the power tower technology at the end of 2001, when the company embarked upon the Solar Tres project, an experimental plant with central tower technology with heliostats, and since then it has made considerable progress in this technology.  GEMASOLAR will be the first commercial plant with this system, but SENER has been testing this technology in these past years at the experimental platform PSA in Almeria with excellent results.
 
In the solar field, SENER has developed software, with the Sensol computer programme, which allows to size and optimise plants, to components, such as the heliostats, heliostat axis drive mechanisms, tower receivers, storage systems, direct steam generation systems and beam-down or plant control systems, as well as cylindrical-parabolic collectors. In the case of collectors, SENER has patented the SENERtrough design, with an appreciably lower steel weight and assembly time than other similar collectors. However, the big technological difference of SENER’s solar thermal plants lies in the innovative molten salts storage system, which doubles the energy exploitation level of a conventional thermosolar power station.