• Energy Research

The EPBD, together with other acts and funding programs, strongly promotes the passive strategies in order to achieve, above all in summer, indoor comfort conditions, reducing or avoiding the active air-conditioning. The adoption and the design of these strategies are not indifferent to the specific boundary conditions. In this paper, the performances achievable adopting an earth-to-air heat exchanger for an air-conditioned building are evaluated for winter and summer. The analysis has been carried out on varying the main boundary conditions related to the environmental context, the soil, the tube properties and connected behaviours of the airflow crossing it. Several control strategies have been simulated too, in order to propose the most suitable design criteria for each climate. The fan electrical energy represents a design critical aspect, requiring an accurate evaluation, in order to achieve the maximum thermal exchange and limiting the pressure drops inside the buried pipes. Otherwise, the use of an EAHX can be also penalizing.

Abstract Nowadays the study of Net Zero Energy Buildings (NZEBs) is fundamental, because they are the main strategy to reduce the building energy demand and CO2-equivalent emissions. This paper analyses a case study concerning a multipurpose building located in Palermo (Southern Italy), and evaluates the benefits related to the use of an earth-to-air heat exchanger in a NZEB, in terms of energy saving and reduction of CO2-equivalent emissions, for a Mediterranean climate. The chosen building envelope is thermally performing. The HVAC system consists in fan-coil units connected to an air-to-water heat pump, and mechanical ventilation. The energy demand is reduced by an earth-to-air heat exchanger that pre-heats the ventilation outside air in winter and cools it in summer. The optimization of the heat exchange with the ground is a key-element to reduce the primary energy requirements and CO2-equivalent emissions, especially during summer. Moreover, this paper assesses the possibility to obtain a NZEB using only on-site renewable energy (on the roof of the building), with and without the earth-to-air heat exchanger. The energy analysis is carried out by means of a dynamic building simulation engine, namely EnergyPlus. In addition, a thermal performance and an environmental analysis are performed.

Abstract In order to deliver the European energy and climate objectives to 2050, significant changes are essential in the building sector, especially regarding the existing stock. Indeed, there is a huge potential for action, also regarding historic buildings. In this regard, today the question is: how to combine the building protection requirements and the application of energy efficiency measures? This paper tries to answer, evaluating if the refurbishment of historic architectures, in order to achieve very low energy need, is possible and economically feasible. More in detail, the applicability of the cost-optimal methodology (EPBD Recast 2010/31/EU) for historic buildings is discussed, by adopting the macroeconomic perspective, in order to take into account of the energy, environmental and economic impacts of about 60 packages of energy efficiency measures. The study is aimed to introduce a methodological approach to define reference buildings for historic architectures, through in-situ investigation of structural and energy peculiarities and, as real case study, the refurbishment of an Italian building of the XV century is presented. Moreover, guidelines are proposed to properly select energy efficiency measures, according to a point of view of cost-optimality. Conservation, aesthetical requirements, structural and energy issues are considered, as well as the incidence of all economic factors.

Buildings account for an important share of global energy consumption and CO2 emissions, so increasing energy efficiency in buildings is essential to ensure an energy transition and sustainable development. In this study, we evaluate the energy benefits obtained through the application of a double-skin façade (passive façade). Subsequently, this is combined first with an airflow network and a control logic for opening windows (active façade) and secondly with transparent photovoltaic modules. The proposed measures are applied to an office building at the University of Naples Federico II. Building’s thermal and energy performance are evaluated using EnergyPlus software, starting from validated energy demands of the base buildings. Both passive and active façade provided a reduction in primary energy consumption for space conditioning, of about 17% and 28%, respectively, and in the total primary energy consumption, of about 4% and 9%, respectively. The best solution, with the maximum energy saving in total primary energy consumption, approximately 20%, is achieved with the active façade and with 80% of the outer layer of the double-skin façade covered by PV modules. The results show that transparent double-skin facades are promising and effective for energy retrofit.

Abstract The ‘Energy Performance of Buildings Directive’ Recast (i.e., 2010/31/EU) establishes that building energy retrofit should pursue “cost-optimal levels”. However, a reliable and rigorous cost-optimal analysis is an arduous and computationally-expensive issue, especially for complex buildings such as hospitals. The paper tackles this issue by providing a novel methodology to identify robust cost-optimal energy retrofit solutions. Multi-stage and multi-objective (Pareto) optimization is performed with the aim of minimizing the computational burden required to achieve reliable outcomes. The methodology combines EnergyPlus and MATLAB® and includes two optimization stages, preceded by a preliminary energy investigation that performs Latin hypercube sampling and sensitivity analysis. The preliminary investigation and the first optimization stage, which runs a genetic algorithm, aim at detecting efficient energy retrofit measures (ERMs) to reduce thermal energy demand for space heating and cooling. In the second optimization stage, these ERMs are combined with further ERMs, addressed to improve the efficiency of energy systems and to exploit renewable energy sources. Investment cost, primary energy consumption and global cost related to the resulting retrofit packages are investigated by means of smart exhaustive sampling. Finally, the cost-optimal solution is identified both in presence of a limitless economic availability and of limited budgets. The methodology is applied to a hospital reference building (RB), which represents hospitals built in South Italy between 1991 and 2005. The RB is defined by using an original approach, as required by the complexity of the examined building category. The achieved cost-optimal retrofit packages imply a reduction of primary energy consumption up to 67.9 kW h/m2 a (12.2%) and of global cost up to 2932 k€ (24.5%) with a maximum investment of 1236 k€.

Abstract The urbanization has negative effects on the environment, mainly related to the generation of pollution, the modification of the properties of the atmosphere, the covering of the soil surface. The cumulative effects produce the so-called phenomenon of ‘Urban Heat Island’ (UHI). Cool roofs have a positive impact on the global environment, by reducing the energy required for interior cooling and related greenhouse gas emissions. Moreover these help to mitigate the UHI effect. A cool roofing material is characterized by higher solar reflectance in comparison to conventional roof coatings and high infrared emittance values. This paper is aimed to investigate the potentialities of high reflective commercial products not specialized for cool roofing. Three paints of the automotive sector have been selected. These products have very fast drying, good adhesion directly to different type of materials, good gloss and appearance, greater durability than traditional, lower cost and application time. Laboratory measurements are performed for the characterization of thermal-optical properties of different prototype samples, by considering application on different substrates (aluminum, ceramic tile, bitumen membrane, polyvinyl chloride sheet) as well as different configurations (evaluating the adoption of gripping and external gloss). Only the white acrylic paint shows good values for spectral reflectance (77–80%) and thermal emissivity (92%) that are comparable with commercial products. The artificial accelerated weather resistance tests and natural exposure effects have been also evaluated. Then, several numerical analyses are proposed for a real case study and some roof technologies also with different insulation level. The main evaluated indexes are the seasonal and annual energy savings, the reduction of polluting emissions and the cost effectiveness. Globally summer benefits are very satisfying meanwhile the annual energy saving varies between 0.3% and 3.0%.

This study introduces an innovative methodology for designing sustainable urban energy districts using Geographic Information Systems (GIS). The scope is to identify specific parts of the urban fabric, suitable for becoming energy districts that can meet the energy needs of dwellings and activities and produce an energy surplus for the city. The method uses building archetypes to characterize the districts and perform simulations through an algorithm based on correction coefficients considering variables such as total building height, exposure, year of construction, and building typology. By leveraging GIS, this approach supports the creation of urban energy maps, which help identify and address potential energy-related issues in various urban contexts. Additionally, the research explores different scenarios for developing energy communities within the district, aiming to optimize energy use and distribution. A case study in Naples, Southern Italy, demonstrates that installing photovoltaic panels on the roofs of buildings can allow a complete electrical supply to the building stock. The final goal is to provide a robust tool that enhances confidence in urban energy planning decisions, contributing to more sustainable and efficient energy management at the district level. This approach may support the urban and territorial governance towards sustainable solutions by developing strategies for the creation of energy communities and optimizing the potential of specific sites.

Abstract The main purpose of this study is to evaluate, based on experimental data, the potential of pre-cooling the ventilation air based on ground-to-water heat exchanger, coupled with an intermediate water-to-air exchanger, during the summer period. The case study for this investigation is an existing nearly zero energy building located in Benevento, a middle-size city of South Italy with typical Mediterranean climate. Measurements of several performance parameters with four different HVAC possible configurations are shown as well as monitoring of energy uses and indoor microclimatic conditions in order to verify if comfort conditions inside the building are guaranteed together with the achievement of ‘nearly zero energy target’. Indeed, the study intends to assess the interaction between building and power grid and evaluate the temporal correspondence between building load and PV generation with hourly time step. The discussion about the hourly energy balance serves as reference to export or improve management and design strategies in regions with comparable climate conditions.