Abstract
Insulation of thermal energy storage tanks is fundamental to reduce heat losses and to achieve high energy storage efficiency. Although water tanks were extensively studied in the literature, the enhancement of the insulation quality is often overlooked. The use of vacuum insulation has the potential to significantly reduce heat losses without affecting the dimension of the storage system. This paper shows for the first time the results of the heat losses tests done for a 0.535 m3 water tank for residential building applications built with a double wall vacuum insulation. The different tests show that the rate of heat losses strictly depends on the temperature distribution inside the tank at the beginning of the experiment. Compared to a conventional water tank insulated with conventional materials, the U-value of the lateral surface was reduced by almost three times (from 1.05 W/K·m2 to 0.38 W/K·m2) using vacuum insulation. However, the bottom part, which is usually used to place the support parts and the piping, is the critical design part of those tanks acting as a thermal bridge with the ambient and enhancing heat losses.
Highlights
The use of renewable energy sources is one of the key actions towards the reduction of gas emissions into the atmosphere
The tank enhancement tested in thisofstudy, are quality significantly compared to conventional insulation insulation is often reduced overlooked, still representing a research gap in due to the minor energy losses at the top using and middle layersmaterials of the tank
Reducing the heat losses conventional with high thermal conductivity could lead to an increase of the dimension of the storage systems indirectly affecting the of the storage itself
Summary
The use of renewable energy sources is one of the key actions towards the reduction of gas emissions into the atmosphere. Different studies and techniques were increase the storing efficiency [13,14] and the use of water tanks with heat pumps using proposed to improve the stratification by enhancing the stratification effect [7,8,9,10,11,12]. We show that mos studies were related to the integration of phase change materials (PCM) to increase the of the studies were conducted through simulations, highlighting a lack of experimenta storing efficiency [13,14] and the use of water tanks with heat pumps using demand-side studies. The results showed that using a vacuum insulated water tank to store the solar heat on a seasonal basis increases the direct renewable heating by 41%, reaching a system efficiency of 51%. Another way to estimate the heat losses in a water tank is to charge the tank over a long period with a gradual temperature increase, reaching a steady state value of heat losses, which are evaluated from the heating power supplied to the tank and the ambient temperature, as reported by Deng et al [29]
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