No abstract

In the present study, we report the results obtained from numerical simulations of low grade heat storage. Four different fluid encapsulated materials were tested in four design types for their suitability as a small scale, low temperature thermal energy storage (TES). This was done by analysing and evaluating the maximum temperature reached per sphere for three different positions inside the tank, which correspond to the top right, centre and bottom right sphere. The influences of the material properties and the inlet/outlet tank designs were analysed and evaluated based on the results. The heat transfer fluid (HTF) was water and the storage materials selected were water, glycerol, MDM and MD3M. These were heated sensibly from an ambient temperature of 20°C to 90°C. The analysis shows that the materials with the highest relevant properties do not in fact charge the tank the fastest. Furthermore, the design of the inlet greatly affects the heating dynamics of the system, whereas changing the outlet design marginally affects the results.

This paper studies the influence of material thermal properties on the charging dynamics in a low temperature Thermal Energy Storage, which combines sensible and latent heat. The analysis is based on a small scale packed bed with encapsulated PCMs, numerically solved using COMSOL Multiphysics. The PCMs studied are materials constructed based on typical thermal properties (melting temperature, density, specific heat capacity (solid and liquid), thermal conductivity (solid and liquid) and the latent heat) of storage mediums in literature. The range of values are: 25–65°C for the melting temperature, 10–500 kJ/kg for the latent heat, 600–1,000 kg/m3 for the density, 0.1–0.4 W/mK (solid and liquid) for the thermal conductivity and 1,000–2,200 J/kgK (solid and liquid) for the specific heat capacity. The temperature change is monitored at three different positions along the tank. The system consists of a 2D tank with L/D ratio of 1 at a starting temperature of 20°C. Water, as the heat transfer fluid, enters the tank at 90°C. Results indicate that latent heat is a leading parameter in the performance of the system, and that the thermal properties of the PCM in liquid phase influence the overall heat absorption more than its solid counterpart.

The growth of solar energy is projected to slow down during 2023–25 despite the fall in costs due to economic deceleration, reduced incentives, and market barriers including the lack of relevant and flexible energy project planning and decision-making tools. This study proposes a flexible and computationally simple multi-criteria decision analysis (MCDA)-based model that takes technical, financial, environmental, social and legal aspects of all project options as input and outputs a feasibility score for each option, which enables ranking the options and identifying the best alternative. The proposed model is applied to a real-world photovoltaic solar farm planned at a site in England and comprising nine different configurations formed by varying system capacity, energy storage option, mode of stakeholder, and network connections. The results of our study show that in this case the options without battery storage and a greater number of off-taker connections are more favorable than the options with battery storage. The analysis also shows that for the solar farm of the presented case study, ‘self-consumption fraction’ and ‘energy yield’, ‘net present value’, ‘life-cycle carbon emission reduction’, ‘ease of permit acquisition’ and ‘public approval’ are key sub-criteria for ‘technical’, ‘financial’, ‘environmental’, and ‘social and legal’ criteria, respectively. A sensitivity analysis was conducted to assess the confidence on the obtained solution, and a change in the first preference was noticed when ‘environmental’ and ‘social and legal’ aspects are given higher weight over ‘technical’ and ‘financial’ aspects. The results obtained are in line with the recommendations by experts, who carried out an independent feasibility analysis considering the same options.

Using thermal energy storage alongside renewables is a way of diminishing the energy lack that exists when renewable energies are unable to run. An in-depth understanding of the specific effect of material properties is needed to enhance the performance of thermal energy storage systems. In this paper, we used fitting models and regression analysis to quantify the effect that latent heat of melting and material density have on the overall heat absorption. A single tank system, with encapsulated phase change materials is analysed with materials properties tested in the range of values commonly found in the literature. These materials are, therefore, hypothetically constructed ones based on materials such as paraffin. The software used for the numerical analysis is COMSOL Mulitphysics. Results show that the relationship between the latent heat and density regarding heat absorbed is a positive linear function for this system.