Energy retrofit of an office building by substitution of the generation system: performance evaluation via dynamic simulation versus current technical standards

A significant percentage of energy requirements, in Europe, is due to heating of buildings. In particular, constructions built in Italy before 1945 are characterized by low energy efficiency and represent a significant share (about 30%) of the total built stock. Retrofit actions in this field can lead to valuable energetic and economic savings. In this work, we ran a dynamic simulation of a historical building of the University of Pisa (suitable benchmark for many Italian public administration buildings) during the heating season. In the first phase, we evaluated the energy requirements of the building and the performance of the existing natural gas boiler, validated with past billings of natural gas. In the second phase, we verified the energetic savings obtainable by the substitution of the boiler with an air-to-water electrically-driven modulating heat pump, simulated through a cycle-based model. We also evaluated the main economic metrics, viz.: discounted payback period, internal rate of return, net present value and profitability index at the expected end of life of the heat pump. The cycle-based model of the heat pump, validated with manufacturers’ data available only at specified temperature and load conditions, can provide more accurate results than simplified models adopted by current technical standards, thus increasing the effectiveness of energy audits.