The ecological transition at the centre of the United Nations 2030 Agenda and the relevant EU policies are increasingly becoming an emerging issue in the political choices of most countries. It is an important challenge to ensure sustainable development and overcome the issue of energy supply. Italy produces 35% of its electricity consumption, a too low percentage that obligates the nation to purchase abroad to cover the overall needs. Energy communities can represent an interesting and viable option for businesses and citizens struggling with the abrupt rising of energy prices. In community energy systems, the energy demand of a group of households or public services is met by electricity collectively generated through renewable sources and this feature is particularly suggested in small towns to promote social benefits and environmental advantages. In this work, possible scenarios of an implementable energy community were investigated for the small mountain municipality of Soveria Mannelli, located in Southern Italy. A building stock made of four public edifices was used as a reference case for which heating needs were determined by dynamic simulations based on the EN ISO 52016-1 procedure. Other simulations carried out in the TRNSYS environment allowed for implementing different schemes of the energy community considering diverse building interaction modes, in which photovoltaic generators and electric batteries cooperate to supply heat pump systems to assure the maximum share of self-consumed electric energy. Indeed, this paper is targeted at the identification of the best solution in terms of technical and economic performance. Despite an evident study limitation is represented by the exclusive use of PV and electric storage systems, the results demonstrate a potential CO₂ emission reduction of over 80%. The more profitable solution for the Municipality was identified with an NPV of 11 k€ in 20 years with appreciable payback.

In the EU, the building sector is responsible for 40% of the global energy consumption for final uses and 36% of the carbon dioxide (CO₂) emissions. Heat pumps allow for the replacement of conventional systems based on fossil fuels with the perspective of combining PV and solar thermal collectors. In order to rationalize the use of the solar source, this paper examined the self-consumption electricity share, the CO₂ equivalent emissions, and the domestic hot water demand covered by renewable sources which were determined in two opposite climatic conditions. These involved both electric and thermal storage systems and considered two different control strategies. The first is commonly used for the management of air-conditioning systems, the second was specifically conceived to maximize the exploitation of the solar source. Results showed that the latter significantly reduced grid dependence in both locations, determining the direct satisfaction of 76% of the thermal and electric loads through the PV self-consumption, determined by 18 kWp of installed PV and a battery capacity of 24 kWh. In terms of equivalent CO₂ emissions, when the two control strategies were compared, a remarkable reduction in emissions was registered for the latter, with percentages ranging between 8% and 36% as a function of PV surface and battery capacity. The analysis of domestic hot water supplies revealed disparities between the two localities: the colder first, relied more on heat pumps for water heating, while the warmer second, benefitted from the large availability of solar radiation.

The Trombe wall is a passive system used in buildings that indirectly transfers thermal energy to the adjacent environment by radiation and convection, and directly by the thermo-circulation that arises in the air cavity delimited between a transparent and an absorbing surface. Nevertheless, the latter is painted black to increase the energy gains, but this produces a negative visual impact and promotes the overheating risk in summer. To mitigate these aspects, a hybrid Trombe wall equipped with PV panels can be employed. The PV installation results in a more pleasing wall appearance and the overheating risk reduces because part of the absorbed solar radiation is transformed into electricity. To determine the actual performance of a such system, transient simulation tools are required to consider properly the wall thermal storage features, variation of the optical properties, air thermo-circulation, and PV power production. Alternatively, regarding the traditional Trombe wall, the literature provides a simplified empirical method based on the dimensionless parameter solar load ratio (SLR) that allows for preliminary evaluations and design. In this paper, the SLR method was calibrated to determine the monthly auxiliary energy to be supplied in buildings equipped with PV-Trombe walls in heating applications. The SLR method was tuned by a multiple linear regression by data provided by TRNSYS simulation that allowed to obtain the energy performances in actual conditions of PV-Trombe walls installed on the same building but located in different localities. The comparison between the TRNSYS results and the calibrated SLR method determined average errors ranging between 0.7% and 1.4%, demonstrating the validity of the proposed methodology.

Heat pumps in buildings allow for the limiting of CO₂ emissions by exploiting directly the renewable energy available in the external environment (aerothermal, hydrothermal and geothermal sources). Moreover, other renewable technologies such as active solar systems can be integrated easily into use with them. This combination not only increases the share of primary energy provided by renewable sources for heating/cooling but also improves the heat pump performance indices. Nevertheless, in cold climates, air–water heat pumps should be equally penalized due to the unfavorable outdoor air temperature. Conversely, a water–water heat pump, connected with a solar tank and thermal solar collectors, overcomes this issue. Indeed, the higher temperature attainable in the cold source allows for reaching greater COPs, and when the solar tank temperature level is enough, emitters can be directly supplied, avoiding the absorption of electric energy. In this paper, this plant configuration, in which a further tank after the heat pump was considered to manage the produced thermal energy, is investigated. Proper control strategies have been developed to increase the renewable share. Regarding a reference residential building located in Milan, for which the water–water heat pump was sized properly, a parametric study, carried out in TRNSYS by varying solar tank volume and collecting surface, has allowed for the identification of the optimal system configuration. A renewable share, ranging between 54% and 61% as a function of the collecting surface and the storage volume, was detected, as was an average seasonal coefficient of performance (SCOP) over 4. Regarding two common heating plant configurations using an assisted PV air-to-water heat pump and a gas boiler, the optimal solution allows for the limiting of CO₂ emissions by 33% and 53%, respectively.

This research delves into the foundational elements of thermal comfort, crucial alongside visual comfort, acoustic comfort, and air quality for ensuring the quality and sustainability of living environments. With increasing recognition of thermal comfort’s implications across various human activities, from energy management for efficiency to considerations of environmental impact and economy, its comprehensive understanding is paramount. The study scrutinizes the prevailing methodology of evaluating comfort via true thermal sensation rating, dissecting the involved variables and their relative significance in determining comfort levels. Following this analysis and parameter definition, a comparative assessment of diverse sensors was conducted to gauge measurement accuracy concerning key variables of interest, thereby identifying the most suitable sensor for real-world applications. Conducted at the ENEA research center in Rome, the study executed an experimental setup within one of the center’s offices. Subsequently, reflections were made on the feasibility of providing indoor comfort indications amidst variable data availability, exploring potential simplifications and approximations to streamline comfort index evaluations.

The accurate estimation of the instantaneous UV Index (UVI) is critical for public health, yet it is often attempted using broadband pyranometers (measuring Global Horizontal Irradiance GHI) or photometers (measuring Lux). This approach is known to be unreliable, particularly under the complex radiative conditions induced by clouds. However, the physical mechanisms driving this failure, specifically the changes in the spectral quality of sunlight, are not fully quantified. This study utilizes a high-resolution spectroradiometer and pyranometer at a Mediterranean site (Rende, Italy), analyzing instantaneous UVI, GHI and a set of derived analytical metrics: the Erythemal Efficacy, the UV Spectral Quality Ratio and the Clearness Index. The core metric of the paper is the Erythemal Efficacy, designed to quantify the “spectral quality” or “biological hazard” per unit of total energy. It is defined as the ratio of the instantaneous UV Index to the instantaneous GHI measured by the pyranometer. The analysis confirms a decoupling between instantaneous UVI and broadband GHI, exhibiting a wide, non-functional scatter. The paper shows that this failure is caused by the high variability of the Erythemal Efficacy, which is not a constant. Its variability is shown to be linearly governed by the internal Ultraviolet A to Ultraviolet B (UVA/UVB) spectral ratio. Most critically, the Erythemal Efficacy was found to follow a counter-intuitive trend, increasing significantly as the Clearness Index decreases. The common assumption of clouds as spectrally “grey” attenuators is flawed. Clouds act as selective filters, attenuating the GHI, dominated by Visible to Near-Infrared (VIS/NIR), more severely than the UVI. This increases the relative biological hazard of the light that penetrates thick cloud cover. This study provides a physical explanation for the failure of broadband proxies and demonstrates that instantaneous GHI or Lux-based UVI alerts are fundamentally unreliable, as they fail to capture the critical variability of spectral quality.