High temperature systems using solid particles as TES and HTF material: A review

Abstract

Thermal energy constitutes up to 90% of global energy budget, centering on heat conversion, transmission, and storage; therefore, the technology for harvesting solar energy worth to be developed. One of them is the concentrated solar power (CSP) solar towers where suntracking heliostats reflect solar radiation to the top of a tower where the receiver is located. The great advantage of CSP over other renewable energy sources is that energy storage is feasible, particularly when the heat transfer fluid (HTF) is also used as thermal energy storage (TES) material which is the case of solid particles. A lot of development efforts are under way for achieving commercial direct solar solid-particle systems. Solid particle systems for transferring high temperature thermal energy are purposed for increasing the efficiency of these systems when converting heat into electric power. This review recapitulates the concept of these systems taking into account the main receiver designs, particle conveyance, particle storage systems and components, the heat exchanger, and the main challenges that must be overcome to split this technology as a commercial one, especially from the materials availability point of view. This review summarizes the actual status of the use of solid particles for TES and as HTF for CSP Tower, and condenses all the available information and classifies them considering the main functional parts and remarking the current research in each part as well as the future challenging issues.

Integration of a thermochemical energy storage system in a Rankine cycle driven by concentrating solar power: Energy and exergy analyses

“…materials being used for CSP applications [Gil 2010;Tiskatine 2017]. Some recent developments are also reported, such as on the use of industrial wastes or by-products [Ortega-Fernández 2015;Gutierrez 2016], chloride salts [Myers 2016], lithium coupled with molten salts [Cabeza 2015], or solid particles [Zhang 2017a;Calderón 2018]. However, their limited energy density (usually between 60 kWhth•m −3 (200 °C-300 °C) for sand, rock and mineral oil, and 150 kWhth•m −3 for cast iron (200 °C-400 °C) [Fernandes 2012]) increases significantly the size of TES systems.…”

Review of solid particle materials for heat transfer fluid and thermal energy storage in solar thermal power plants

“…Only some of them have been deeply studied, and the most remarkable designs are presented in Figure . Solar receivers can be classified according to the way they capture solar heat: Direct receivers, in which the particle media (acting as HTF) directly absorb the solar irradiance. These receiver designs make high solar absorptance to be included among particle media desirable properties. Indirect receivers that use another material to absorb the solar heat and then exchange it to the particle media. …”

“…One option to control residence time is the particle recirculation by making the particles to pass several times through the aperture until they reach the desired temperature . This approach has been modeled and simulations have shown it is effective enough to reach 800°C; nevertheless, possible particle losses in the aperture must be reduced either by using an air curtain or by any other solution.…”

“…Particles are flowing through the receiver at the top of the tower, capturing the concentrated sunlight. After reaching the desired temperature, the solid particles are moved by the conveyance system to a hot storage tank, in which the material is collected until it is moved into a heat exchanger (HEX) to transfer the high temperature heat to the power generation cycle …”

“…After reaching the desired temperature, the solid particles are moved by the conveyance system to a hot storage tank, in which the material is collected until it is moved into a heat exchanger (HEX) to transfer the high temperature heat to the power generation cycle. 15 Exhausted heat particles are then moved to a (relatively) low temperature storage tank to be stored until they can be moved back to the solar receiver on the top of the tower to harvest solar heat again. 12 This plant distribution is similar to the current commercial molten salts CSP tower system 16 ; however, almost all the components of the plant should be specially redesigned for working with solid particles at high temperature.…”