Basilica di Santa Maria di Collemaggio

High-efficiency hydronic pew-based heating system specifically designed for the Basilica di Collemaggio. In such system the heat transfer fluid (water) is heated by the generator, which is a water to water heat pump, and is distributed through small pipes to the benches and the heated footboards. The pews thus integrate hydronic radiant panels, specifically adapted for the purpose, placed in order to maximize the radiative surface and the related view factor in respect to seated people. The whole heating system was designed assuming an heat pump with a nominal power of 30 kW (brine input temperature of 0◦C and water output temperature at 40◦C) with a SCOP of the geothermal heat pump system equal to 4. It takes into account also electric consumption due to required auxiliaries. The geothermal heat exchanger are realized with 4 boreholes (150 m deep each) placed on the back of the Basilica. The entire system is turned on 1 h before each celebration at nominal power and to be switched off at the end of the event.

The effectiveness of the proposed heating system was simulated considering the whole church’s environment using CFD software. It shows that the increase in air temperature in the upper part of the church during the heating system operations is about 2.5◦C, and thus it does not cause abrupt or substantial changes in temperature. As already said, the main advantage of the local heating system is that the air in the church is not heated towards high temperatures,but that the heat is directly radiated to people. Whereas the air temperature around the benches only rises slightly (with a temperature of about 13◦C), the radiant temperature at the positions where the people are seatedreaches a level of 17◦C or higher. It can be considered an acceptable level for providing human thermal comfort, according to the results of the comfort analysis.