To compete with conventional heat-to-power technologies, such as thermal power plants, Concentrated Solar Power (CSP) must meet the electricity demand round the clock even if the sun is not shining. Thermal energy storage (TES) is able to fulfil this need by storing heat, providing a continuous supply of heat over day and night for power generation. As a result, TES has been identified as a key enabling technology to increase the current level of solar energy utilisation, thus allowing CSP to become highly dispatchable. This article aims to review different TES technologies that have been investigated and deployed over the past two decades. The review will give a comprehensive overview of TES technologies investigated, demonstrated and/or deployed in CSP plants with a specific emphasis on TES materials perspective. A thorough analysis will also be given on the state-of-the-art of the CSP technologies including commercial development and research innovation. An attempt is also made to use the information gathered along this review to postulate future technology evolution of CSP plants in terms of CSP configurations, TES technologies and location of CSP plants, and to assess the current and future role of TES in CSP field.
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Linear Fresnel collection systems consist of flat or curved mirrors rows that track the sun and focus its radiation on a fixed receiver. This type of CSP receiver system offers the lowest start-up cost due to its simple design and components . Flat mirrors, which are cheaper than others, allow higher reflectors density per square meter. Its structure is much simpler, which also reduces maintenance costs. However, CSP plants incorporating linear Fresnel receivers have the lowest solar-to-electrical efficiency, falling in the range of 8–10% . LFR have greater optical losses than troughs when the solar radiation angle is small, which reduces the generation in early morning, late afternoon and winter. This drawback can partially be overcomed by using higher operating temperatures (higher than trough plants) . Linear Fresnel CSP systems have received limited interest to date, but offering higher efficiencies has been the main innovation area of focus . Before 2014, just 90 MW of linear Fresnel collectors were installed around the world (see Fig. 12). LFR are projected to account for the 4% (373 MW) of the total CSP capacity operational together with under construction/development by 2021 (see Fig. 12). From the 14 projects found for LFR, one is under contract (1 MW), 7 under construction or development (224 MW), 4 operational (157.4 MW) and 2 non-operational (7 MW). The non-operational plants were constructed in Australia and United States in 2012 and 2008, respectively, and none of them had storage facility. Regarding the operational plants, they were built between 2009 and 2014 in Spain, India and Italy (see Fig. 12). Only the two operational plants in Spain (Puerto Errado thermosolar power plant) have a storage unit based on the Ruth's tank , a steam storage accumulator, with 0.5 h single thermocline storage tank . The currently largest operational Linear Fresnel array is in Dhusar (India), under operation since 2014 (125 MW); with no storage . LFR is the technology that is using different TES media, despite steam is the most used one. In that plants under development, contract or construction, the storage media will be steam, molten salts or concrete (see Fig. 9). China is the only country supporting new generation storage media such as concrete, the plants Zhangbei and Zhangjiakou, CSG Fresnel with 50 MW capacity and 14 h storage will be commissioned in 2020 . Nevertheless, other two plants with molten salt as storage media (two-tank indirect) are under development in China, both of them with a capacity of 50 MW (Urat, 50 MW Fresnel CSP project, and Dacheng Dunhuang, 50 MW Molten Salt Fresnel project) . Morocco and France have commissioned three small size LFR plants, with 1–9 MW capacity (two Morocco and one France), using from 20 min to 4 h storage steam's capacity. The other project under construction, in 2017, is in north of India, 14 MW installed with no storage (Dadri ISCC Plant).The work was partially funded by the Spanish government (ENE2015-64117-C5-2-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to its research group DIOPMA (2017 SGR 118). DIOPMA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. The authors would like also to thank you the Engineering and Physical Sciences Research Council (EPSRC) for their support through the research grants EP/P003605/1 (Joint UK-India Clean Energy Centre) and EP/P004709/1 (Energy-Use Minimisation via High Performance Heat-Power-Cooling Conversion and Integration: A Holistic Molecules to Technologies to Systems Approach).
- Concentrated solar power plants (CSP)
- Thermal energy storage (TES)
ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment