Highly efficient, cost-effective solar-geothermal heat supply concept for multi-family houses and small residential areas

Abstract

The concept mentioned above is in principle designed in a similar way as the energy concept of so-called “solar houses” or “solar active houses” with high solar fractions > 50 %, where heat is usually generated by solar thermal collectors and stored in large-volume hot water stores. Regarding the high efficient, cost-effective solar-geothermal heat supply concept introduced in this paper, about 50 % of the annual heat demand for domestic hot water and space heating can be provided by solar energy. Another 40 % of the annual heat demand is provided by shallow geothermal energy, and only an additional 10 % of the annual heat demand is required in the form of electrical energy to operate a compression heat pump. The high efficiency of the concept is derived from an efficient combination of the used technologies in conjunction with a specially adapted control strategy and the use of innovative key products. For example, the geothermal source system is based on highly efficient, slim, helical ground heat exchangers with high specific heat transfer capacities, which are immersed only up to 10 meters in the ground. In contrast to conventional borehole heat exchangers, the installation of these innovative heat exchangers is relatively low priced and, due to the small drilling depth, no hydrogeological problems are expected. This contribution is focused on the presentation of the above described, newly developed system concept as well as first results of the design and simulation studies for a pilot heat supply system that is planned to be realized in a complex of three multi-family houses within a total living area of approx. 3 530 m² in the German city Crailsheim, which is located 80 km north-east of Stuttgart. The development of the concept is part of the research project ‘1to10 – Development, testing and demonstration of a sustainable, standardized solar-geothermal heat supply concept’. In the conceptual design phase of the project, theoretical work for the realization of such systems is performed. Another key part of the design phase is for example the issue of a stakeholder analysis and, based on this analysis the development of a constellation of stakeholders.