Principles of saving energy with dynamic thermal storage

Panel: Panel 7. Innovative buildings technologies

Authors:
Kaare Gether, Gether AS, Norway
Harald Gether, Green Innovation, NTNU, Norway
Helge Skarphagen, NIVA, Norway
Jørgen Gether, MSc, Gether AS, Norway

Abstract

This paper describes the interaction between thermal storage and various sources of variation in heat supply and demand, to promise overall thermodynamic work within a temperature span of 20°C or less. This allows coefficients of performance (COP) of 6.0, twice that of conventional heat pumps and in many cases free cooling without heat pumps. Variation in ambient air temperature, solar radiation or patterns of energy usage, optimised in conjunction with heat pumps and dynamic thermal energy storage (DTES), promise to save large amounts of energy used for the heating and cooling of buildings. For example, cooling at night at 24 °C, rather than in warm afternoons at 34°C will remove 45% of the thermodynamic load. Economic savings are further improved where off-peak tariffs for electric power exist. Variation from various sources, combined with thermal storage, promises to become an attractive source of renewable energy and economic savings. Furthermore, a dynamic thermal energy storage (DTES) may be combined with borehole thermal energy storage (BTES) to allow summer heat to be used for heating in wintertime, whilst cooling during summer. A DTES is constructed in practice as a below-ground 'well' adjacent to a (new or existing) building. The area on top is available for other use. Typical size for a single-family home is a volume of 5-7 m³ and a cross-section of 2-3 m². The technology promises to be cost effective in mass application, in particular for commercial buildings.