G. Cáceres

Thermo-mechanical analysis of ceramic encapsulated phase-change-material (PCM) particles

Thermal energy storage (TES) is of growing importance, and involves the storage of both sensible and latent heat. Latent heat storage is particularly attractive, since it can store the energy as the latent heat of fusion at a constant temperature, thus providing a high energy storage density. The low temperature encapsulated phase change materials (PCM) in buildings have been extensively investigated mostly in rigid cells. The present paper studied the encapsulation of salts PCM material within elastic shells. The mechanical feasibility of such a spherical shell coating of a melting material is first investigated. The influence of encapsulation on the melting process of PCMs is thereafter studied for this particular geometrical case, including the complicated interactions with melting temperature of PCMs. The stored energy and pressure variation due to the volume change during the melting process are examined. It is shown that the encapsulated PCM particles can melt without cracking the coating shell only under specific conditions.

Performance of molten salt solar power towers in Chile

Chile is facing important challenges to develop its energy sector. Estimations demonstrate that in its electricity consumption Chile will grow at an annual rate of 4.6% until 2030, despite ongoing efficiency improvements. To satisfy this demand in a sustainable way, the national energy policy promotes the integration of novel and clean power generation into the national power mix, with special emphasis on concentrated solar power (CSP). The present paper assesses the development of solar-based electricity generation in Chile by CSP, achieved by a Solar Power Tower plant (SPT) using molten salt as heat carrier and store. Such SPTs can be installed at different locations in Chile, and connected to the main national grid. Results show that each SPT plant can generate around 76 GWhel of net electricity, when considering solar irradiation as the sole energy source and at a 16% overall efficiency of the SPT process. For operation in a continuous mode, a hybrid configuration with integrated gas backup system inc...

Two-Phase Shrinking Porous Media Drying: A Modeling Approach Including Liquid Pressure Gradients Effects

This article deals with the drying modeling of a saturated deformable porous media (solid + fluid). This modeling takes into account the mechanical behavior of the product as well as its initial conditions such as its moisture content and geometry. The effect of fluid pressure gradient on the fluid transfer is described by using Darcys law, and the fluid compressibility is characterized by its bulk modulus of elasticity. The solid phase is supposed to be incompressible and the porous media permanently diphasic (ideal shrinkage hypothesis). The description of the strong thermo-hydro-mechanical coupling that takes place within the material during drying is taken into account in the light of Biots consolidation theory by adopting Terzaghis effective stress principle. The numerical resolution is performed by FEM and ALE methods. A comparison between experimental results (convective drying of an alumina gel) and numerical results improves the ability of this modeling to describe thermo-hydro-mechanical coupling. It further highlights a current lack of precision in the determination of the thermophysical parameters values that control the model.

A validated design simulation tool for passive solar space heating: Results from a monitored house in West Lothian, Scotland

Determining the availability of renewable sources on a particular site would result in increasing the efficiency of buildings through appropriate design. The overall aim of the project is to develop a pioneering software tool allowing the assessment of possible energy sources for any building design project. The package would allow the user to simulate the efficiency of the Passive Solar Space Heating referred in the Low and Zero Carbon Energy Sources (LZCES) Strategic Guide stated by the Office of the Deputy Prime Minister (2006) and the Building Regulations. This research paper presents the tool for modelling the passive solar sources availability in relation to low-carbon building. A 3-month experimental set up monitoring a solar house in West Lothian, Scotland, was also undertaken to validate the simulation tool. Experimental and simulation results were found in good agreement following a one-to-one relationship demonstrating the ability of the newly developed tool to assess potential solar gain available for buildings. This modelling tool is highly valuable in consideration of the part L of the Building Regulations (updated in 2010).

Renewable energy transition: a market-driven solution for the energy and environmental concerns in Chile

Chile is undergoing a remarkable energy matrix transition to renewable energy. Renewable energies are expanding extraordinarily fast, exceeding earlier predictions. As a result, the country is expected to meet its 2025 goal of generating 20% of its electricity from renewable energy sources quite before. Chile has become one of the first countries in the world with subsidy-free markets, where renewable projects compete directly with other conventional sources. Favorable market conditions and successful policy reforms were keys to fostering this renewable energy development. Although the country has achieved a substantial growth in renewable energy investment in a relatively short period of time, this optimism should be treated with caution. A successful transition requires a combination of a clear decision making, persistent and consistent government policies, and a clear commitment to tackling challenges to accommodate renewable energy in the power system. In this context, this paper analyses the Chilean renewable industry and the required government policies to succeed in this transition. For this purpose, we identify several critical factors that have attracted and that could attract investment to the renewable energy sector and propose key recommendations to effectively address the major challenges faced for the future development of the industry.