Solar power plant Gemasolar

The solar power plant 'Gemasolar' situated near Seville in Spain uses unique innovations which makes it not only more efficient than other thermoelectric solar plants, but also able to continue producing electricity without sunlight. Because its central tower receiver and molten salt storage technology enables it to produce electricity for 15 hours without the sun (and even 24 hours in summer time), Gemasolar can continue to operate during the night or cloudy weather. This means, for the first time solar energy has become manageable, and capable of responding to large scale commercial demand.

Fine Tubes has been working with SENER for 4 years developing and producing the corrosion-resistant heat exchanger tubes for the steam generators as well as the high performance tubing that make up the receiver of the Gemasolar central tower - which is capable of absorbing 95% of radiation in the solar spectrum and transmitting this energy to be stored in the molten salt compound in its interior.

“SENER values highly the contribution of Fine Tubes to this project. The service conditions of components required high quality and reliable products - which Fine Tubes has rigorously fulfilled. Other remarkable aspects during the manufacturing process were meeting deadlines, and continuous information transfer, two points where the collaboration with Fine Tubes was crucial and essential for the successful development of the project." Santiago Arias, Technical Director of Operation and Maintenance, from Torresol Energy, and Peru Arribalzaga, Project Management of SENER.


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Background

SENER has been working in the solar field industry since the 1980’s when the company was developing solar technology, including the first heliostats (mirrored panels which reflect sunlight). During 2001-2005 the company worked on two groundbreaking solar power plant projects, Solar Tres and Andasol-1, which provided them with enormous research and development opportunities resulting in the creation of Gemasolar.

The Gemasolar project itself began in 2006, when SENER designed and installed an experimental unit in the Almeria Solar Platform which demonstrated the validity of the receiver design and the molten salts system. Together with Abu Dhabi’s alternative energies company MASDAR, the company formed Torresol Energy in 2008 and Gemasolor started commercial production in 2011.

The 185 hectare site near Seville boasts 2,650 heliostats which aim solar radiation at the tower’s receiver system. The radiation heats molten salts that circulate inside the tower to temperatures of more than 500 °C. These salts are used directly as the heat absorption fluid: they are pumped from the cold molten salt tank to the receiver at the top of the tower, where they are heated to extreme temperatures, after which they descend to the hot molten salt tank or directly to the heat exchanger where they generate steam. When excess of energy is received, i.e., when the received heat radiation is more than the turbine demand, the level in the hot tank increases, enabling the power plant to generate electricity for up to 15 hours without any incoming solar radiation.

Challenges

Because Gemasolar is a first-of-its-kind; challenges have been present at every project stage. It is unique due to its innovative design and cutting edge equipment developed by SENER; notably the central tower and receiver, the solar field and the control system.


© TORRESOL ENERGY

The central receiver is the main component for this type of thermosolar plant and its component parts need to perform reliably in extreme conditions throughout the plant’s lifetime. Fine Tubes needed to provide extremely robust tubes made from a material with a high resistance to corrosion, thermo-mechanical fatigue and creep to be capable of holding the molten salt. High quality and durability for these tubes is vitally important because the receiver availability is continuous, absorbing an enormous amount of solar energy - the equivalent of more than 1,000 suns.                                                 

SENER also required heat exchanger tubing to operate effectively within the steam generator units. Once again quality and durability were imperative, the units work at very high pressure turning the turbines to generate electrical power for over 27,500 homes per year.

Solutions

There are no ‘off the shelf’ solutions in a project such as this and Fine Tubes first went to work with SENER creating prototype panels. Because we were able to exceed the standard definitions required for these component parts, SENER selected us to be the exclusive supplier of tubes for the manufacturing panels of the central receiver. We have produced over 15 km of high performance 25mm OD seamless tubing for the system, which holds the 565°C molten salt (nitric salt), housed in the 140 metre high Gemasolar tower. Made from the corrosion-resistant nickel-chromium alloy, the tubing has superior resistance to very high temperatures and the extreme service conditions.

We also provided over 300m of 19mm OD heat exchanger tubes manufactured from the same nickel-chromium alloy, but with a thicker wall to withstand the high pressures present within the steam generators.

The plant was officially opened in October 2011. The results achieved in the first year of Gemasolar operation have broken all expectations. Since then, its available production hours are increasing significantly and it is hitting all production goals.

After a routine annual maintenance stop at the beginning of 2012, the plant achieved continuous 24-hour production for 12 straight days in winter, successfully delivering the projected energy supply to the grid. For the coming year, the plant is projected to continue the same upward production trend, producing a total for the year of over 110 GWh net, functioning for a total of 6,450 hours at full capacity.

Next Steps 

There is still a lot to learn about the operation of a plant as unique as Gemasolar and to SENER it represents a starting point for the cost reduction strategy in the thermosolar energy sector. The company is confident that its future tower projects will be much more profitable and that in the coming years with the standardisation of the industry, concentrated solar power (CSP) can be competitive with traditional energy sources.

This is a global industry that will continue to grow and Torresol Energy has plans to develop more of these large scale plants throughout the world. New opportunities are being sought in the international market and the company is developing solar plants in India, the United States, the MENA region and South Africa. Several potential new plants are foreseen and SENER is already working with Fine Tubes on further collaborations - as the receiver of each new plant will use around 50km of tubes.

The Gemasolar plant has won the CSP Today USA ‘Thermosolar Innovation 2011’ prize, (this year it also won the CSP Seville prize for the 2012 dispatchability solution) while Torresol Energy won two of the European CSP Today prizes, for ‘Commercialized Technology Innovation 2011’ and ‘Most Effective Project Development 2011’.

SENER was selected as a winner in the awards presented by the FIDIC, the International Federation of Consulting Engineers, for its Gemasolar project. The plant received the Award of Merit in the Major civil engineering projects category, along with other 11 major constructions from around the world, ‘for its contribution to improve quality of life'.

In 2013, SENER  was awarded The European Energy Awards as Engineering Company of the Year. SENER received this award for innovative projects such as the Gemasolar solar thermal plant.

About SENER 

SENER has a wide experience in the development of process and power generating plants, especially in combined cycle, cogeneration, thermosolar, nuclear energy, liquid natural gas regasification, biofuels, refinery units, chemicals, petrochemicals and plastics plants, as well as in transportation, storage and distribution systems for solid, liquid, and gaseous fuels.

SENER has specialized engineering teams in all of the relevant disciplines: process, instrumentation, civil and structural, piping, electrical, I&C and mechanical engineering, procurement management, and planning and control. Its services include all of the possible engineering and construction operations such as: feasibility and conceptual design studies, facility basic and detail engineering, procurement, work supervision, start-up, training of personnel, construction and construction management as well as EPC projects.

SENER has earned an outstanding reputation in generation and efficient use of energy as well as in chemical and industrial processes. SENER was awarded with the ‘Engineering Firm of the Year 2011’ trophy, an award it won in both the European and US versions, and ‘Increased Dispatchability Solution 2011’ in recognition of the company’s revolutionary molten salt storage system. 

Further information

http://www.sener-power-process.com/ENERGIA/ProjectsI/gemasolar
http://www.torresolenergy.com/TORRESOL/gemasolar-plant/en

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