Hot tap water production by a 4 kW sorption segmented reactor in household scale for seasonal heat storage

Abstract

\u3cp\u3eReplacing fossil fuel by solar energy as a promising sustainable energy source, is of high interest, for both electricity and heat generation. However, to reach high solar thermal fractions and to overcome the mismatch between supply and demand of solar heat, long term heat storage is necessary. A promising method for long term heat storage is to use thermochemical materials, TCMs. The reversible adsorption–desorption reactions, which are exothermic in the hydration direction and endothermic in the reverse dehydration direction, can be used to store heat. A 250 L setup based on a gas–solid reaction between water–zeolite 13X is designed and tested. Humid air is introduced into a packed bed reactor filled with dehydrated material, and due to the adsorption of water vapour on TCM, heat is released. The reactor consists of four segments of 62.5 L each, which can be operated in different modes. The temperature is measured at several locations to gain insight into the effect of segmentation. Experiments are performeignore.txtd for hydration–dehydration cycles in different modes. Using the temperatures measured at different locations in the system, a complete thermal picture of the system is calculated, including thermal powers of the segments. A maximum power of around 4 kW is obtained by running the segments in parallel mode. Compactness and robustness are two important factors for the successful introduction of heat storage systems in the built environment, and both can be met by reactor segmentation. With the segmented reactor concept, a high flexibility can be achieved in the performance of a heat storage system, while still being compact. The system is also able to produce domestic hot tap water with the required temperature of 60 °C. This can be done by implementing a recuperating unit to preheat the inflow by recovering the residual heat in the outflow. In this work, the recuperator is simulated by a heater, and applicability of the system for domestic purposes is assessed. An energy density of 198 kWh/m\u3csup\u3e3\u3c/sup\u3e is calculated on material level, and the energy density calculated on reactor level is around 108 kWh/m\u3csup\u3e3\u3c/sup\u3e and 61 kWh/m\u3csup\u3e3\u3c/sup\u3e for experiment without and with preheating, respectively.\u3c/p\u3