In agreement with what emerges from the document of IRENA “Innovation Outlook TES 2020”, there are currently 93 CSP plants operating worldwide.
About half of those (47%) are currently integrated with TES systems (Pelay et al. 2017) that mainly use molten salts technology.
Operators of CSP plants that use molten salt TES technologies face several challenges. These include:
• The high cost of the molten salts used as storage media.
• The need for a substantial amount of backup energy in order to minimize the risk of the salt freezing.
• Reliability issues with the TES system, due in part to the corrosive nature of the molten salts.
• Concerns around parasitic use, and cost of antifreeze and circulation pumping.
Source: “IRENA - Innovation Outlook TES 2020”
Solid-particles storage technology like STEM-CSP could offer a compact and cheaper alternative to molten salts for CSP applications. The sand is an inexpensive raw material that benefits from good mechanical properties and is non-toxic, inert and non-flammable. Furthermore, STEM-CSP operates at almost ambient pressure, thus no pressure vessels are needed, reducing capital costs further. The lifetime of STEM-CSP technology is over 30 years and represents the best alternative to molten salts, the closest to time-to-market compared to other new sensible heat TES technologies.
STEM-CSP plant size
To reduce costs for scale economies, the size of CSP projects is increasing, for example the new projects in the United States and elsewhere are in the 150–500 MW range and even larger. Increasing the size helps to reduce costs for scale economies, but appropriate plant size also depends on technology.
Thermal energy storage is becoming an increasingly important feature for new plants as it allows CSP to dispatch electricity to the grid during cloudy periods or at night, provides reliable capacity and ancillary services, and reduces integration challenges. Molten salt is the most widely used system for storing thermal energy, but other types, including STEM-CSP technology, are also in use or being tested and developed.
In this contest, STEM-CSP has all the features needed to compete with other technologies. To meet different needs, Magaldi has developed a type of CSP system equipped with thermal storage suitable for small and medium-sized applications. Thanks to its reduced size, STEM-CSP requires less space to be made available, with noticeably fewer complications in choosing the site and in obtaining building permits.
The advantages are not only linked to the simplicity of construction but also derive from the fact that in this way it is possible to create a CSP system even in the vicinity of industrial areas or cities and it is no longer strictly necessary to find deserted areas far from the point of use of the energy.