F. Ochs

Performance of Large-Scale Seasonal Thermal Energy Stores

More than 30 international research and pilot seasonal thermal energy stores (TESs) were realized within the past 30 years. Experiences with operation of these systems show that TES are technically feasible and work well. Seasonal storage of solar thermal energy or of waste heat from heat and power cogeneration plants can significantly contribute to substitute fossil fuels in future energy systems. However, performance with respect to thermal losses and lifetime has to be enhanced, while construction costs have to be further reduced. This paper gives an overview about the state-of the-art of seasonal thermal energy storage with the focus on tank and pit TES construction. Aspects of TES modeling are given. Based on modeled and measured data, the influence of construction type, system configuration, and boundary conditions on thermal losses of large-scale TES is identified. The focus is on large-scale applications with tank and pit thermal energy stores and on recent investigations on suitable materials and constructions. Furthermore, experiences with the operation of these systems with respect to storage performance are discussed.

Seasonal Hot Water Heat Store With Self-Supporting Shell Cover

A new self-supporting cover for seasonal hot water stores has been developed. It is installed at the Institute of Thermodynamics and Thermal Engineering (ITW) as shell cover with prefabricated sandwich elements made of high-performance concrete with PUR core. Due to the significantly higher strength of the high-performance concrete very thin units can be produced. In contrast to conventional self-supporting covers for the construction no scaffolding and hence no foundation is required. Reduced material usage and consequently reduced primary energy demand for construction is a further advantage of this concept.