1,721,064 research outputs found
Ground source heat pumps in high humidity soils : an experimental analysis
No full textThis paper shows the results of a monitoring campaign on an invertible ground source heat pump (GSHP) with borehole heat exchangers installed in the historical center of Venice in the frame of the renovation of an ancient building where other renewable energy systems, such as solar energy systems, are not admitted because of historical preservation regulations. Despite the coastal position, the use of surface or ground water was not achievable in this case. In fact, the withdrawal from wells is absolutely forbidden in Venice, due to the risk of subsidence of the soil. In addition, as often happens in Venice, the internal channels next to the building have insufficient water flow rate. The experimental analysis highlights very satisfactory performance especially in comparison with the alternative use of air source heat pumps. The high humidity of the soil and the underground water flow present even in the surface layers of the soil promote the quick thermal rebalancing in the borehole field. For the same reason, although there is un-balance between the heat rejected in summer and the one extracted during winter, no consequent thermal degradation of the ground heat exchange is encountered
Optimal Arrangement of Photovoltaic Panels Depending on Climate and Building’s Intended Use
No full textIn many contemporary projects of sustainable buildings the surface occupied by the photovoltaic (PV) panels is divided into parts having different orientations and slopes, different from the ideal arrangement. In case of re-use of existing buildings, the reason for this choice is generally the need to exploit the surfaces available on the roof. However, in the case of new buildings, the reason may consist in the need for continuous electricity generation along the day. The question that arises is the following: at what extent these solutions are less convenient than the optimal one? In this work different configurations of the PV park are compared using computer simulations. At first, the ideal arrangement was defined and compared with other configurations, inspired by actual projects. Then, a case study was examined: it is a residential building, typical of the Italian suburbs. The analysis was performed using the weather data of two Italian cities: Venice, in northeast, and Trapani, in southern Italy
On-field validation of a seasonal performance calculation method for chillers in buildings
No full textIn the last years the importance of part load conditions in the estimation of chiller performance in real world operation has been completely acknowledged. As a matter of fact, chillers are sized for peak loads, so they usually run under part load conditions, far from the full load ones, taken as references in catalogues. Some methods for these calculations already exist, both in Standards and in building energy simulation programs, but they lack an extensive validation in actual HVAC systems. In this regard, the present paper compares the chiller performance estimated via the calculation method contained in Standard EN 14825 against monitored data taken along an entire cooling season, both in a small HVAC plant and in a large one. In the present paper a variation of the calculation method contained in Standard EN 14825 is use
Experimental analysis of the performances of a surface water source heat pump
No full textNowadays the heat pump is gaining new interest thanks to recent regulations which include this technology among those able to exploit renewable energy sources in addition to the already acknowledged opportunity to achieve significant energy and economic benefits if well applied In particular the use of geothermal energy as heat source/sink looks very promising. Besides the use of ground heat exchangers and water from wells, an adequate availability of surface water can suggest its use for the heat pump especially when it is impossible the application of the other two alternatives. This is the case of the plant here reported. A heat pump installed in the historical centre of Venice and using lagoon water for the HVAC plant of a historical structure refurbished for hotel use. The plant characteristics and the adopted technical solutions are here illustrated as well as the results of an annual monitoring of the building-plant system. The experimental data have also permitted a comparison with the performances of alternative plant solutions simulated in front of the same operative conditions. For this aim the two case studies of a corresponding air source heat pump and a more traditional solution, based on condensing boilers and air cooled chillers, have been considered. The performance analysis shows a net superiority for the surface water heat pump
Optimisation of insulation and solar control strategies as function of building’s intended use in the retrofit of massive buildings
No full textIn temperate climates, such as most Italian ones, the need to limit both winter heat losses of buildings and their overheating in other periods is present. The second requirement is particularly relevant in the presence of high internal and solar gains. In these climates, it is not convenient to exceed the insulation thickness. Therefore, when the energy renovation of an old building with heavy masonry is performed it is a question of optimizing the position (internal or external) and the thickness of the additional insulation. Another question is the choice of a solar control strategy, if extended glazed surfaces are present. Both of these problems are present in old Italian public buildings, particularly in schools. This paper presents a computerized methodology for optimizing these choices. The case study consists in a typical school building from the early 1900s with a heavy structure and large glass surfaces in a climate of Northern Italy (Bologna), with cold winter and hot summer. The results show that the external insulation is the best performing, and that there is an optimal thickness when the building is a school. If the building is reused for offices, due to the lower internal gains, the energy convenience of the external insulation increases, but its optimal thickness becomes excessive. Small slats inserted between the glasses are the best performing solar control device from both an energy and visual comfort point of view; on the other hand, the external slats provide better thermal comfort in the warmer period
Strategie d’integrazione della produzione da risorse rinnovabili nei territori del Triveneto
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