Optimized integration concepts for basic-booster heat pump solutions for building renovations
Achieving climate-neutral cities in Europe requires replacing of gas-fired boilers with efficient heating systems that can be integrated into existing older apartment buildings. In addition to district heating, basic-booster heat pumps combined with minimally invasive thermal refurbishment of old buildings are essential. Because the performance of heat pumps depends largely on the required temperature lift, they are typically paired with floor heating systems. In building renovation, however, such solutions as changing from radiators to floor heating systems is often overly invasive. Therefore, it is essential to retain existing radiators while reducing supply temperatures below 45 °C through targeted thermal refurbishment. This work presents detailed simulations to assess the performance of basic-booster heat pump systems and optimize the design of intermediate heating circuits. The results show that basic-booster heat pumps can achieve up to 25% higher coefficients of performance compared to single-stage systems. Optimal performance is obtained by appropriately sizing the central basic heat pump, minimizing the temperature spread, and matching the temperature level of the intermediate circuit to the intermediate pressure level of a comparable two-stage cycle. An intermediate storage tank enables the system to use a day-night-shift, which can increase the coefficient of performance by approximately further 10% through the utilization of higher daytime ambient temperatures and reduce nighttime fan noise from air-source units. When properly designed, the basic-booster heat pump system offers an efficient and practical technology to replace gas boilers in building renovations for urban areas.