In urban multifamily houses, decentralized DHW systems using gas or electric boilers are still widely used. Their replacement with renewable energy sources is difficult and generally needs centralized DHW systems with a circulation system that ensures comfort and hygiene at the price of elevated heat losses. A consortium of three academic and one industry partner developed a decentralized DHW system, which uses the residual heat from the exhaust air of a controlled ventilation unit as energy source for a micro heat pump. The entire system, including ventilation unit, heat pump, and storage tank fits into the bathroom prewall and produces hot water for one apartment. This contribution gives an overview of the system and focusses on the development of the flat storage tank that fits into the prewall space of less than 30 cm width.

SPF Institute for Solar Technology