Abstract

The main influencing parameter on the efficiency of adsorptive thermochemical energy storage is the efficiency of the desorption process, which is influenced by the process conditions, for example, desorption time and desorption temperature, and the working pair (adsorbent–adsorbate). Due to constrained process requirements, for example, hours of sun shine and low desorption temperatures available from a flat plate solar collector (333–373 K), the only possibility to increase the efficiency is to change the working pair. The reference working pair water–zeolite 13X needs high desorption temperatures of 500 K and high heat inputs per mass adsorbent (1080 kJ kg−1) in the desorption process to reach the maximum efficiency of 79 % and maximum energy density of 844 kJ kg−1. Therefore, the goal is to reach efficiencies in the same range as the maximum efficiency of water–zeolite 13X for desorption temperatures lower than 500 K with the usage of different adsorbates. Four systems of alcohol as adsorbate on activated carbon are compared with the reference working pair. The usage of alcohols on activated carbon allows for highly efficient adsorptive storage even at low desorption temperatures between 360 and 450 K. The maximum efficiency is shifted to higher desorption temperatures with increasing carbon chain length of the alcohol. At low desorption temperatures, the energy density and efficiency of methanol, ethanol, and propanol are higher than the energy density of the reference system. Hence, the alcohol systems on activated carbon are viable alternative approaches for regulating these process parameters.

Abstract

The paper describes the development of a novel thermal system for all kind of low consumption electric vehicles. For the first time in our knowledge, a compact thermal system integrates a heat pump, a thermal storage unit, a photovoltaic panel and distributed high efficiency annular fans including PCT resistors in their centers. The vehicle is divided in three independent compartments: food storage, battery pack and cabin which are thermally managed with defined priorities in relation to whether the vehicle is plugged-in, in motion or parked unplugged. The implemented control strategies adapt themselves in relation to the outdoor temperature to minimize energy consumption. Phase Change Materials PCM are used to keep the battery pack temperature conditioned even when the vehicle is parked unplugged in the open air at extreme cold temperatures, in that case during the day the PMC material integrated in the battery pack accumulate the energy produced during the day by the solar panels and release heat during the night. Following simulations of various condition of operation rather advanced algorithms have been implemented into an electronic board so that the conditioning of the three compartments is made by autonomous decisions in practically all conditions of operations. The cold storage unit has been dimensioned in such a way that per the typical two-hour mission of a hot summer, the three compartments of the temperature controlled food delivery vehicle could be temperature and humidity conditioned using only the thermal energy storage. The system could also be monitored and activated by a smart phone. The temperature controlled food delivering vehicle integrating all developed technologies will be demonstrated in operation at the exhibition of TRA 2018.

Abstract

The exterior finish layer in building facades is exposed to considerable environmental loads, which can reduce the service life of the materials, increasing the need for replacement. New climate challenges impose to look more carefully at the long-term performance and durability of building components and materials. Thermal stresses due to daily temperature fluctuations and UV exposure can significantly damage facades and degrade their performance. This research measures the long-term performance of a responsive cementitious finish plaster. The developed cement plaster is combined with phase change materials (PCMs), and thermochromic (TC) pigments to control solar radiation and surface temperatures dynamically on the exterior façade year around. The main objective of the study is to quantify the effect of long-term UV exposure on the optical performance of the cement plasters. PCMs with three different melting temperatures of 18oC, 24oC, and 28oC were combined with two different colors of blue and red TC paint with a transition temperature of 31oC. Accelerated UV aging of the samples was performed using lab tests to simulate exposure to UV radiation for two years. The solar reflectance of the samples was characterized before and after the accelerated UV aging tests. The results of the aging tests revealed that UV exposure impacts the solar reflectance of the finish material based on the method of integrating the TC paint to the cement plaster. In the case of TC paint applied to the surface, the solar reflectance of the plasters with only the TC is reduced by 15% after aging, while the ones combined with PCMs have a similar solar reflectance value after aging.