Abstract
Thermal energy storage (TES) systems for concentrated solar power plants are essential for the convenience of renewable energy sources in terms of energy dispatchability, economical aspects and their larger use. TES systems based on the use of concrete have been demonstrated to possess good heat exchange characteristics, wide availability of the heat storage medium and low cost. Therefore, the purpose of this work was the development and characterization of a new concrete-based heat storage material containing a concrete mix capable of operating at medium–high temperatures with improved performance. In this work, a small amount of shape-stabilized phase change material (PCM) was included, thus developing a new material capable of storing energy both as sensible and latent heat. This material was therefore characterized thermally and mechanically and showed increased thermal properties such as stored energy density (up to +7%, with a temperature difference of 100 °C at an average operating temperature of 250 °C) when 5 wt% of PCM was added. By taking advantage of these characteristics, particularly the higher energy density, thermal energy storage systems that are more compact and economically feasible can be built to operate within a temperature range of approximately 150–350 °C with a reduction, compared to a concrete-only based thermal energy storage system, of approximately 7% for the required volume and cost.
Highlights
The density of the various mix designs was calculated as a weight-to-volume ratio, the latter being estimated as the average value of the three heights and three diameters measured for each concrete specimen
This study showed that the addition of phase change material (PCM)-containing steel capsules has a double effect on the performance of the concrete, depending on the quantity of capsules and their degree of filling: an increase in the stored energy density due to the contribution of latent heat was obtained
The purpose of this work was the development of a new type of heat storage medium based on the use of a widely available, low-cost material, concrete, to which a small amount of phase-changing material, solar salt, was added, microencapsulated in a porous medium, diatomite
Summary
Increasing attention to environmental issues, such as the containment of global warming, reduction of greenhouse gas emissions, environmental sustainability of human activities and the rapid depletion of fossil energy resources [1,2], requires the transition to a different energy system model based on the clean and efficient use of renewable and sustainable energy [3,4,5,6,7,8] that is capable of avoiding power grid overloads.Concentrated solar energy plays an important role in this context because it can provide zero-emission high-temperature heat (CST) and electricity (CSP) [9,10,11,12]. The major advantage of CSP/CST plants lies in the possibility to integrate a thermal energy storage (TES) system and store a large amount of solar heat to make it available even in periods when sunlight is not present and to produce electricity at a better cost. This allows the more efficient use of the turbine and other components of the power block. The stored energy density is an important parameter [16] to evaluate the performance of TES technologies because the required volume should be as low as possible
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