This paper describes the characterization of four salt hydrates as potential thermochemical material for compact seasonal heat storage in the built environment. First, magnesium sulfate was investigated in detail using TG-DSC apparatus. The results of this study revealed that magnesium sulfate is able to store almost 10 times more energy than water of the same volume. However, the material was unable to take up water (and release heat) under practical conditions. A new theoretical study identified three salt hydrates besides magnesium sulfate as promising materials for compact seasonal heat storage: aluminum sulfate, magnesium chloride and calcium chloride. These salt hydrates (including magnesium sulfate) were tested in a newly constructed experimental setup. Based on the observed temperature lift under practical conditions, it was found that magnesium chloride was the most promising material of the four tested salt hydrates. However, both calcium chloride and magnesium chloride tend to form a gel-like material due to melting or formation of a solution. This effect is undesired since it reduces the ability of the material to take up water again. Finally, it was observed that performing the hydration at low-pressure will improve the water vapor transport in comparison to atmospheric pressure hydration.
Transmission electron microscopy (TEM) measurements and theoretical analysis are combined to construct the physical picture of formation of SiO2 fractal aggregates in a methane/hexamethyldisiloxane/air atmospheric pressure flame. The formation of SiO2 fractal aggregates is described as a multistage process. The first stage is combustion of fuel in a narrow flame front region with formation of main combustion products including SiO2 molecules. Further downstream SiO2 molecules join in liquid nanoclusters. After cooling combustion products due to heat losses to surroundings, the nanoclusters become solid in a cold flame region and join in fractal aggregates there. Along with growth of fractal aggregates, the restructuring process proceeds in a cold flame region that leads to the decrease of the fractal dimension of fractal aggregates. The measured parameters of fractal aggregates are in accord with those followed from theoretical models.
About 30% of the energy consumption in the Netherlands is taken up by residences and offices. Most of this energy is used for heating purposes. In order to reduce the consumption of fossil fuels, it is necessary to reduce this energy use as much as possible by means of insulation and heat recovery. The remaining demand could be met by solar thermal, provided that an effective way would exist for storing solar heat.
Thermochemical reactions are one of the most promising means for compact, low loss and long term storage of solar heat in the built environment. The heat can be stored by making use of a reversible chemical reaction. In theory, an energy density 5-10 times higher than water can be reached. Additionally, no storage losses are associated with thermochemical heat storage. Thermochemical materials have been identified that are cheap, non-toxic, have sufficient energy density and have reaction temperatures that can be reached by a vacuum tube collector. These requirements are fulfilled by a number of salt hydrates. A detailed study at ECN identified MgCl 2 .6H 2 O as the most promising salt hydrate for compact seasonal heat storage. The material was found to be capable of storing and releasing heat under practical conditions. In the present paper, the results on MgCl 2 .6H 2 O characterization and the first results using a fixed bed reactor will be presented.
The main features of low calorific gases as those from biomass gasification processes, landfills, mines and sewage sludge are well known. They can be expressed as low calorific values, high water content, corrosive actions and composition changes. Due to these characteristics there are up to date no combustion systems available which are capable to utilise such gases efficiently. The ordinary combustion concepts frequently do not guarantee sufficient flame stability. The high emissions of harmful substances as CO and NO x are another problem. Because of mentioned difficulties it is necessary and also a challenge to develop an efficient and flexible combustion system which can handle these problems.Through several matching steps of numerical and experimental investigations Gaswärme-Institut e. V. Essen (GWI) developed a progressive combustion system based on the concept of continuous air staging (COSTAIR). Burner tests at a small scale thermal load of 30 kW proved a stable combustion and low NO x and CO emissions for different qualities of low calorific gases. The best design of a small scale burner was transferred to larger thermal loads by applying of scale-up criteria. Already achieved experimental results at 200 kW th confirmed the efficient performance and the high potential of the burner for use of low calorific gases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.