Rhys Jacob

Geopolymer encapsulation of a chloride salt phase change material for high temperature thermal energy storage

In an effort to reduce the cost and increase the material compatibility of encapsulated phase change materials (EPCMs) a new encapsulated system has been proposed. In the current study a molten salt eutectic of barium chloride (53% wt.), potassium chloride (28% wt.) and sodium chloride (19% wt.) has been identified as a promising candidate for low cost EPCM storage systems. The latent heat, melting point and thermal stability of the phase change material (PCM) was determined by DSC and was found to be in good agreement with results published in the literature. To cope with the corrosive nature of the PCM, it was decided that a fly-ash based geopolymer met the thermal and economic constraints for encapsulation. The thermal stability of the geopolymer shell was also tested with several formulations proving to form a stable shell for the chosen PCM at 200°C and/or 600°C. Lastly several capsules of the geopolymer shell with a chloride PCM were fabricated using a variety of methods with several samples remaining stable after exposure to 600°C testing.

A numerical model for thermal energy storage systems utilising encapsulated phase change materials

In an effort to reduce the cost of thermal energy storage for concentrated solar power plants, a thermocline storage concept was investigated. Two systems were investigated being a sensible-only and an encapsulated phase change system. Both systems have the potential to reduce the storage tank volume and/or reduce the cost of the filler material, thereby reducing the cost of the system when compared to current two-tank molten salt systems. The objective of the current paper is to create a numerical model capable of designing and simulating the aforementioned thermocline storage concepts in the open source programming language known as Python. The results of the current study are compared to previous numerical results and are found to be in good agreement.

Economic Studies on High-Temperature Phase Change Storage Systems

Abstract In this chapter cost comparisons of encapsulated phase change materials (EPCMs), coil-in-tank, and heat pipe thermal energy storage systems are reviewed. Due to the increased interest in this field there are a number of studies on the economics of the aforementioned systems. However, in the absence of any commercial-scale systems confident cost estimations are difficult. Of great benefit to latent heat cost estimation is the construction of two-tank molten salt systems, which can provide a good estimation of tank cost, and other balance of system costs. As companies start to develop these technologies, more accurate cost information can be provided allowing a more critical comparison to be made.

Encapsulation of High-Temperature Phase Change Materials

Abstract In an attempt to solve the poor conductivity and material compatibility issues that are common with phase change materials (PCMs), the encapsulation of these materials is proposed. The encapsulation of the PCM involves the covering of the PCM in a suitable material. This has the benefit of increasing the surface area available for heat transfer (increasing the overall thermal conductivity) and allowing the PCM to be in contact with a more suitable material (reducing compatibility issues). The following review is intended to investigate the experimental and numerical attempts to fabricate and simulate encapsulated PCMs (EPCMs) as an appropriate form of thermal energy storage for high-temperature (>300°C) uses.

Capital cost expenditure of high temperature latent and sensible thermal energy storage systems

In the following study cost estimates have been undertaken for an encapsulated phase change material (EPCM) packed bed, a packed bed thermocline and a traditional two-tank molten salt system. The effect of various heat transfer fluids (air and molten salt), system configuration (cascade vs one PCM, and direct vs indirect) and temperature difference (ΔT = 100-500 °C) on the cost estimate of the system was also investigated. Lastly, the storage system boundary was expanded to include heat exchangers, pumps and fans, and heat tracing so that a thorough cost comparison could be undertaken. The results presented in this paper provide a methodology to quickly compare various systems and configurations while providing design limits for the studied technologies.In the following study cost estimates have been undertaken for an encapsulated phase change material (EPCM) packed bed, a packed bed thermocline and a traditional two-tank molten salt system. The effect of various heat transfer fluids (air and molten salt), system configuration (cascade vs one PCM, and direct vs indirect) and temperature difference (ΔT = 100-500 °C) on the cost estimate of the system was also investigated. Lastly, the storage system boundary was expanded to include heat exchangers, pumps and fans, and heat tracing so that a thorough cost comparison could be undertaken. The results presented in this paper provide a methodology to quickly compare various systems and configurations while providing design limits for the studied technologies.