DYNAMIC ANALYSIS OF SOLAR HOT WATER SYSTEMS: THE CASE STUDY OF A DWELLING LOCATED IN ITALY

Abstract The present paper is aimed at the energetic analysis of a solar hot water system performed on a dwelling located in different cities in Italy, precisely, from north to south: Bolzano, Turin, Bologna, Rome, Brindisi and Trapani. The study is focused on a group of apartments, where the domestic hot water is provided by a solar system coupled with a storage tank and a recirculation loop; it is worth to mention that the recirculation loop is obligatory on this kind of plants. Therefore, a dynamic energetic study is carried out, assigned the hot water load profiles and the set parameters of the solar collectors with reference to the configurations here tested (flat plane and evacuated tube). Thus, dynamic simulations have been performed by means of TRNSYS simulations tool, setting different parameters: collector configuration and mass flow rate. Several ideas and results emerged from this study, such as the sizing process of the whole system, according to the variation of the solar fraction for all the analyzed scenarios. A digression with simulation results regarding a specific case concludes the paper. More specifically, the study of water temperature oscillations in winter and summer time with reference to the climatic data of Bologna has been carried out under particular operating conditions: i) the pump of the recirculation loop is powered all time (24 hours a day) ii) the pump is switched off during the night, except when the water temperature in the loop falls below a certain threshold temperature

Energy savings in hospital patient rooms: the role of windows size and glazing properties

Abstract Large windows with increased exposure to daylight have strong positive effects on the well-being of building occupants and can provide energy savings when appropriate glazing specifications are employed. The work evaluates the impact of different window sizes and glazing on heating and cooling energy needs in a hospital patient room, in order to investigate the energy savings achievable by adopting wider openings and to identify the most effective glazing types. Simulations have been conducted for different commercially available glazing systems. The authors analyzed the energy performance of a base case window with 25% Window-to-Wall Ratio (WWR) and of a wall-to-ceiling window with 77% WWR, in rooms facing the four different orientations and located in Bologna, Italy. Results show that the adoption of wider windows with appropriate glazing can lower the heating and cooling energy demand

The bin method to investigate the effect of climate conditions on the SCOP of air source heat pumps: the Italian case

The paper investigates the seasonal performances of electric air-to-water heat pumps specifically related to climatic conditions of the place where the heat pump is installed. The analysis is carried out using easily available weather data for some Italian towns differently located, and using the bin-method proposed by UNI/TS 11300-4. Two different types of heat pumps (on-off and inverter-driven variable speed compressor) are considered and comparisons between different types of heat pumps and different places of installation are performed. The analysis shows that the climate of the installation place is the most important factor that affects seasonal indexes of heat pumps; moreover, as expected, inverter heat pumps better perform than on-off ones

How the Energy Price Variability in Italy Affects the Cost of Building Heating: A Trnsys-Guided Comparison between Air-Source Heat Pumps and Gas Boilers

The paper investigates the variation in building thermal energy demand for different indoor air set-point temperature and presents an economic analysis comparing the cost of a heating generation system based on an air-to-water heat pump and a gas boiler. Dynamic simulations were performed considering three different residential building characteristics of the Italian building stock placed in different Italian municipalities: Milan, Rome and Naples. An economic analysis was carried out considering the gas and electricity prices related to the years 2019–2022 provided by Italian Regulatory Authority for Energy, Networks and Environment (ARERA). The analysis showed the competitiveness of the heat pump compared with the gas boiler as a heating generation system in terms of annual costs for heating in almost all the scenarios considered and also showed an important reduction in building thermal energy demand if the set-point temperature was reduced, even by 1 ◦C

Effect of real temperature data on the seasonal coefficient of performance of air source heat pumps

In this paper, a transient analysis is performed in order to evaluate how effective climate data affect the determination of the seasonal coefficient of performance of ASHPs. Three Italian cities, characterized by different climates, are considered as reference case studies and the influence of real meteorological data, collected from different years, on the heat pump SCOP is performed. The analysis is carried out by employing the dynamic software TRNSYS. Numerical results show small variations in SCOP, while a significant influence on annual thermal energy demand can be observed. The analysis also underlines the absence of a general correlation between annual thermal energy supplied by the heat pump and SCOP and between HDD and SCOP