Abstract
Ground coupled heat pumps are a notoriously efficient system for heating and cooling buildings. Sometimes the characteristics of the building and the user’s needs are such that the amount of heat extracted from the ground during the winter season can be considerably different from the amount injected in summer. This situation can cause a progressive cooling or heating of the ground with a negative effect on the energy efficiency and correct operation of the system. In these cases, an accurate sizing has to be done. In systems already built, it could be necessary to intervene a posteriori to remedy an excessive ground thermal drift due to the energy unbalance. In this work, such a situation relating to a real office building in Italy is investigated and several solutions are examined, one of which has been then implemented. In particular, a hybrid heat pump using as heat sink both the ground and external air is compared with common solutions through computer simulations using a dedicated numerical model, which has also been compared with monitoring data. As a result, the hybrid heat pump shows better performance and limits the thermal drift of the ground temperature.
Highlights
Climate change is a major challenge for the international Community
In 2017, following the analysis described below, the heat pump was changed with a new machine (Figure 2c) coupled to both the boreholes and an air-condenser (Figure 2d) to be used only during the cooling season; in summer, the heat pump can switch between the ground heat exchangers and air-condenser without a secondary loop, no additional compressors or pumps are present
From 2017 to 2026, the thermal drift of the ground temperature is lower than the previous period and, in addition, the profile is more stable; this is due to the use of the test reference year of Padova [39] as a climate boundary condition
Summary
Climate change is a major challenge for the international Community. European Countries aim to achieve net zero emissions by 2050 [1,2]. An important contribution to achieving this goal can come from buildings that account for up to 36% of final energy use [3]. Nowadays, heating and cooling energy consumption in buildings is mainly based on fossil fuels [4], which considerably contribute to greenhouse emissions. The first step is surely to limit the energy use in buildings by adopting efficient solutions. This can be obtained by optimizing the building envelope with suitable materials and technologies [5]. Once this is done, new systems based on the exploitation of renewable energy sources can be installed to increase the energy efficiency
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