Development of a zero-energy-sauna: Simulation study of thermal energy storage

Abstract

As a practical contribution to the energy transition from fossil to renewable energy, this paper addresses a wellness product with high energy demand: the sauna. The overall goal of the presented research project is to develop and demonstrate a so-called Zero-Energy-Sauna. In this paper, the development by means of numerical simulations is discussed. In a preliminary study, multiple concepts have been systematically derived and assessed. One innovative concept has been patented and an extended version of this concept is being implemented in this research project. The implemented concept utilizes solar energy and applies two types of thermal energy storage: a pressurized, stratified hot water storage and a closed low-pressure adsorption storage. The main purpose of the hot water storage is the heat supply, while the purpose of the adsorption storage is to provide steam. We formulate and investigate two numerical models for these thermal energy storages. For the hot water storage, an one-dimensional model is applied which considers the effect of natural convection. With this model, different charging and discharging scenarios are examined, proving the applicability of this type of hot water storage for a Zero-Energy-Sauna. For the adsorption storage, a previously developed and published model is adopted and extended by a metal plate for manual steam generation. Based on this model, various configurations of the adsorption storage are studied, revealing an optimum design for maximum steam generation. The storage designs derived by numerical simulations serve as blueprints for the two thermal energy storages. Both storages are currently being implemented and experimentally investigated in the Zero-Energy-Sauna of the ongoing research project.