The Current Situation and Perspectives on the Use of Solar Energy for Electricity Generation:Concentrated Solar Power

Concentrated Solar Power

After about a decade of low development, the CSP sector is now reviving, notably due to a favorable supporting framework in Spain and increasing investments in the USA. A CSP plant consists, basically, of a solar concentrator system made of a receiver and collector to produce heat and a power block (in most cases a Rankine cycle). Today, CSP technologies are in the stage of a first commercial deployment of power production in Europe.

Due to past developments in the USA, the most mature large-scale CSP technology is the parabolic trough/heat transfer medium system. In Europe, a parabolic trough power plant with a power capacity of 50 MWe and 7.5 h of storage (Andasol 1) is in operation in Granada, Spain. Two more plants of 50 MWe each are scheduled to be built on the same site.

Central receiving systems (solar tower) are the second main family of CSP technology. An 11 MWe saturated steam central receiver project, named PS 10, has been operating since March 2007 in Andalusia, Spain. This is the first com- mercial-scale project operating in Europe.

Solar Tres is another project under development in Spain based on a molten salt central receiver system. Parabolic Dish engines or turbines (e.g., using a Stirling or a small gas turbine) are promising modular systems of relatively small size (between 5 to 50 kWe), in the development phase, and are primarily designed for decentralized power supply. The solar only average load factor without thermal storage of a CSP plant is about 1,800–2,500 full-load hours per year. The level of dispatching from CSP technologies can be augmented and secured with thermal storage or with hybrid or combined-cycle schemes with natural gas, an important attribute for connection with the conventional grid. For instance, in the Solar Tres project, 15 h molten salt storage is included, leading to a capacity factor of 64 % without fossil fuel power backup. Several integrated solar combined-cycle projects using solar and natural gas are under development, for instance, in Algeria, Egypt, India, Italy, and Morocco.

The cost of electricity for CSP technologies is strongly influenced by the direct normal irradiance (DNI), but also by the reliance on thermal storage that can extend the capacity factor and increase their dispatch capability. For DNI, as encountered in the Sahara region or in the USA, the current cost of electricity production could be decreased between 20 and 30 % with respect to similar technologies operating in Southern Europe. The important resource base in neigh- boring European Mediterranean countries makes it possible to envisage importing CSP energy. For a given DNI, cost reduction of the order of 25–35 % is achiev- able due to technological innovations and process scaling up. Facility scaling up to 400 MWe will result in cost reduction of the order of 14 %. CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists; the most developed are the parabolic trough (see Fig. 4.2), the concentrating linear Fresnel

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reflector, the Stirling dish, and the solar power tower. Various techniques are used to track the sun and focus light. In all of these systems, a working fluid is heated by the concentrated sunlight and is then used for power generation or energy storage (Martin et al. 2005).

The top five countries for CSP are not so easy to predict. Most of the available information considered within this group the following countries: US, Spain,4 India, Australia, and Morocco. Only one European country is included in this group.

After having been blocked for a long time in its development, the CSP sector is undergoing a full revival today due to falling costs, technologies that are more effective to the policies sensitive to environmental questions (Morales Pedraza 2008). For this reason, the total global CSP capacity increased in recent years more than 60 % to about 2,550 MW. Most of this capacity was added in Spain, home to more than three-fourths of the world’s CSP capacity. No new capacity came on line in the USA, but about 1,300 MW was under construction by year end. Elsewhere, more than 100 MW of capacity was operating, mostly in North Africa. The industry is expanding into Australia, Chile, China, India, the MENA region, and South Africa. Falling solar PV and natural gas prices, the global eco- nomic downturn, and policy changes in Spain all created uncertainty for CSP manufacturers and developers.

By the end of 2012, global solar thermal capacity reached an estimated 282 GWth for all collector types, with the capacity of glazed water collectors reaching an estimated 255 GWth. China and Europe account for about 90 % of the world market (all types) and the vast majority of total capacity (REN 21 2013).

According to EC sources, the economic potential of CSP electricity in EU-15 is estimated to be around 1,500 TWh per year, mainly in the Mediterranean coun- tries (DNI > 2,000 kWh per m2 per year). The estimated maximum potential for CSP in the EU-27 is up to 1.8 GW by 2020 and 4.6 GW by 2030. Assuming that a grid infrastructure has been built with Northern Africa countries, the maximum CSP electricity imports would be up to 55 TWh and 216 TWh between 2020 and 2030, respectively. The maximum penetration of CSP electricity for 2020 and 2030 would generate between 1.6 and 5.5 % of the projected EU gross electricity consumption. No fossil fuel backup is assumed, with average load factors at about 6,000 full-load hours in 2020 and 2030, due to the use of thermal storage.

The European industry currently has a market leadership in CSP technologies worldwide. At this stage of development, there is a supply chain industry already able to offer turn-key equipment for power plants in the range of 10–50 MWe. However, an industrial ramp-up in all aspects (engineering, procurement and con- struction, components, manufacturing, and maintenance) will be necessary to go from current market shares to significant ones.

The USA, the birthplace of this sector, today concentrates practically all of the installed CSP capacity in the world with 355 MWe in California. Four American states are particularly involved in developing new CSP projects: Nevada with 64 MWe, California, where two contracts have been signed to develop 800 MWe between 2008 and 2011, Arizona, and New Mexico.

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