Solar active building with directly heated concrete floor slabs

Abstract

A new concept for solar active houses is presented within this paper. In contrast to existing solar house solutions, the solar collector heat gains are distributed in a temperature-optimized way to three different heat sinks - a significantly smaller storage tank, concrete floor elements directly fed by the solar circuit and a ground heat exchanger which also serves as the heat source of a heat pump, which is the backup heater. This new layout should reduce the today's usual extra system costs of solar houses by about 25%. System simulations prove the functionality of the concept and show even higher solar fractions and energy savings as simulated for the existing solar active house concept. One of the main components in the new concept is the controller which has to decide which heat sink will be charged. A control strategy was developed which evaluates the potential outputs of the collector operating to each heat sink. Simulations allow determining the optimal control parameters for this approach. While the thermal activation is able to compensate the decreasing solar input to the smaller storage tank, the effects of the regeneration of the ground heat exchanger are significantly smaller. However, the regeneration avoids a long-term temperature decrease in the ground and may allow a reduction of the heat exchanger area.