• Energy Research

In the perspective of reducing land occupation of built environments, the most efficient strategy is to increase the reuse of obsolete or abandoned constructions instead of designing new buildings. This is particularly true regarding public buildings, usually characterized by considerable dimensions. The paper is focused on this issue, particularly on its energy implications. It analyzes the headquarters of the “G. D’Annunzio” University in Pescara, Italy, initially designed for commercial use and later converted to a university building during its construction. The authors first carried out a numerical analysis of the building energy performance in its current state and then they proposed some improvement interventions evaluating their incidence on the annual energy balance of the building, showing how the most commonly used energy saving strategies do not give the best results in any case, being greatly influenced by the climatic zone in which the building is located. Starting from these considerations, the authors carried out the analysis by considering three different Italian climatic conditions so as to determine their influence on the building energy performance and to define the best strategy for energy requalification in each climatic zone.

Energy efficiency and thermal and acoustic comfort play crucial roles in the design and management of educational buildings. The literature underscores their influence on students’ and teachers’ well-being and productivity. Additionally, numerous works emphasise the growing environmental awareness among children attending sustainably designed or adapted buildings. In light of these considerations, the present study aims to evaluate the dynamic energy performance of a school located in Northern Italy, conceived as a Nearly Zero Energy Building (NZEB). The school integrates various technologies, intelligent systems, and renewable sources to reduce energy requirements. A second aspect under evaluation involves using both real and virtual anemometers to generate crucial weather data for energy simulations. Dynamic analyses often rely on traditional meteorological year (Typical Meteorological Year) datasets derived from outdated sources, leading to inaccuracies in representing current climatic conditions, especially in the case of results related to a specific period.

Abstract This paper investigates the aerodynamic performance of a Savonius vertical axis wind rotor to be used in an innovative lamppost. The wind generator studied is the main part of a public lighting system (a street lamp) powered by both aeolian and solar renewable energy sources. This study is aimed to analyze the effects of different construction solutions on rotor performance. Experimental dynamic tests were carried out on a 1:1 rotor model in the Environmental Wind Tunnel (EWT) of University “Politecnica delle Marche” (UNIVPM); tests were performed at different wind velocities and for different construction combinations. The results obtained confirmed that, in the tested range 2–3.3 × 10 5 , rotor performance does not depend on the Reynolds number. Tests also showed that the presence of end plates and blade overlap increases the power coefficient C P , max , while the presence of external grids and structural posts has negative effects on rotor performance. The best results were obtained for a configuration having a helical rotor with a 105° twist, open blade overlap and end plates.

Abstract The aim of this paper is to show the possibility to increase small wind turbine performances using a Micro Electro Mechanical System (M.E.M.S.) placed inside the blade. In particular its effects on the Laminar Separation Bubble (LSB) phenomenon are presented. This is a local boundary layer separation, that may occur on aerodynamic bodies operating at low Reynolds numbers as the root blade sections of small horizontal axis wind turbine rotors. Its presence induces an aerodynamic efficiency drop-off due to a drag increase and a lift decrease. Tests are performed on an airfoil designed for the root section of a small wind turbine having a 10 kW nominal power. A M.E.M.S. was placed internally the wing section to produce mechanical disturbances directly inside the boundary layer; M.E.M.S.’ lower face is clamped to the wing structure, while the upper one is glued to a PVC movable strip aligned with the airfoil upper surface. M.E.M.S. was electrically supplied at different amplitudes and frequencies in order to vary vibration modes. Preliminary measurements, performed by using a pressure distribution analysis, were carried out to qualitatively locate the LSB presence. Laminar separation, transition and turbulent reattachment points positions are quantitatively detected by means of a thermographic approach: the heated thin foil technique is used to observe temperature distribution on the airfoil surface and a numerical energy balance approach was employed to evaluate the local convective heat transfer coefficient h . Afterward the local Stanton number distribution was calculated and a first and second derivatives analysis allowed to localize the LSB characteristic points positions. Results showed a very effective M.E.M.S. action for frequencies about 175 Hz and a Reynolds number of 10 5 . A lift increases about 50%, was showed with a consequent increase of the wind turbine C p values.

Abstract The paper discusses the computational fluid dynamics simulation results of a bluff body. A literature case regarding a closed box section of a suspended bridge was selected since it is of practical relevance. An OpenFOAM implementation of a Spalart–Allmaras local correlation based transition model for Reynolds Averaged Navier–Stokes (RANS) equations was used as flow model. Locally-formulated RANS transition models were coupled with the Spalart–Allmaras (SA) model to reduce the computational cost with respect to the SST k − ω model. This model, named γ − R θ , t ˜ -SA, was successfully applied on airfoil sections and results are given by literature. In this paper, we present a set of computations of the flow field around a bluff body in order to stress the need to take into account transition effects in these kind of applications. The measure of the proposed model reliability was attested comparing experimental pressure coefficients and aerodynamic forces on the bridge section; besides, the effects of the model predictions on the critical flutter velocity, estimated by FEM and 2DOF Scanlan model of a pedestrian bridge structure, was examined as case of study.

Nowadays, the importance of implementing energy efficiency (EE) measures is growing significantly worldwide, based on its potential to reduce energy demands and mitigate climate change effects. Paraguay is a developing country with the highest per capita hydroelectric energy generation in the world, but only 18% of local consumption is hydroelectric and 41% of its energy matrix corresponds to oil products. This paper aims to analyse the importance the Country places on EE as a strategy towards sustainable development and to highlight as EE is an effective pathway to mitigate the climate changes and contrast their effects. The authors initially provide an insight into the climate scenarios for Paraguay and underline the effects of the climate changes on the buildings’ comfort. Subsequently, the authors provide, by resourcing a bibliographic review, a description of the Paraguayan sectors of greater energy consumption, its policies and targets set for increasing EE. Besides, the main EE projects developed by other neighbouring South American countries are analysed to show the level of development of each one in the scope of EE and to offer a reference basis of potential virtuous solutions to be adopted in Paraguay. A focus on the building sector is also made to provide a foundation for policy analyses to enhance EE in this sector. As a result of this review, evidence that EE is beginning to take part in Paraguay’s public policies was found, with the leaders becoming aware of its importance. Nevertheless, many concrete results could not be achieved as of yet and overcoming these barriers still involve a great challenge. Regarding the building sector, few advances have been noticed regarding the regulations of buildings’ thermal performance, a reason for which the National objectives set need to be more specific to achieve greater collective awareness to enforce them. Finally, key actions are recommended for Paraguay aiming to improve EE levels to face the climate change phenomenon.

This research seeks to evaluate the impact of climate change (CC) on the thermal performance of buildings. In particular, it is focused on historical residential buildings located in Asuncion, Paraguay, a city characterised by a humid subtropical climate. Energy dynamic simulations of a representative building in its original state and an energy efficient version were assessed to evaluate the effectiveness of common energy retrofit measures under future climate conditions. Low and high Representative Concentration Pathways climate scenarios for 2030, 2050 and 2070 are employed with a CORDEX climate model and compared with observed weather data of 2009. Two thermal comfort assessment methods are considered, the statistic and the adaptive thermal comfort approach, where operative temperatures and overheating and underheating rates are analysed. As expected, the results show that the projected temperature rise will lead to an increment of discomfort rates, but it could be mitigated by energy refurbishment measures. Thus, CC effects on thermal performance of buildings are relevant and must be considered for the development of adaptation strategies able to manage this phenomenon. At present, Paraguay does not have any energy building codes and, instead, the results of this paper underline their needs with a substantial impact on society and building industry of Paraguay since it demonstrates that the creation of energy buildings codes is highly necessary to face CC impact on buildings.

Abstract This paper addresses a computational fluid–dynamics study of a multi–blade inlet damper for gas turbine power plants. This device is used in the aspiration duct of the aforementioned plants with the aim to control the air mass flow rate, to dump flow turbulence and to guarantee the plant security. Nowadays the flat plate is the standard shape for damper blades. Clearly the device is rather simple but the operating conditions may prove burdensome. This is related to the vortex shedding developing behind the damper blades. If the shedding frequency of the vortices is close to the resonance frequency of the structure it generates a synchronism that involves the oscillation growth. This can lead to the structure damage. In this research work we have devised a new airfoil shaped blade for inlet dampers in order to suppress the vortex shedding phenomenon behind the damper blades. A proper numerical analysis of the damper blades pitching stability requires to solve a two-way fluid–rigid body interaction problem. Moreover the overset mesh method is strictly needed to investigate the blades motion due to aerodynamic interactions; as a matter of fact other techniques cannot be advocated for this problem since blades closure requirements produce the overlap of moving zones. For this reason we have developed a specific approach, based on the above mentioned techniques, to investigate the dynamic behaviour of the blades of a inlet damper. The obtained results show as the new blades have a very good pitching stability.