Improving the energy efficiency of buildings is a major priority within the context of the European objectives to reduce greenhouse gas emissions by 55% by 2030 and to achieve climate neutrality by 2050. Nearly Zero-Energy Buildings (nZEBs) offer a promising solution to significantly reduce energy consumption and promote the use of renewable energy sources. There is a significant gap in the scholarly literature regarding systematic reviews focused on the advancements in European legislation related to energy efficiency. Consequently, this paper aims to provide a comprehensive synthesis of the key legislative norms targeting the energy efficiency of buildings and the necessity of utilizing renewable energy sources for electricity generation, with a particular focus on the forecasts for the year 2030. The objective is to offer valuable reference resources and to support the global expansion of nZEB implementation in a sustainable and resilient manner. This research thoroughly evaluates the development of nZEBs, emphasizing design concepts, technological innovations, and their impact on energy efficiency. An analysis of the main barriers to implementation highlights high costs, limited technological feasibility, regulatory constraints, and insufficient stakeholder engagement. The purpose of this paper is to review the literature on building energy efficiency and the European trajectory from passive to zero-energy buildings.

Increasing the energy efficiency of a drug factory is the main purpose of this paper. Different configurations of cogeneration systems are analyzed to meet most of the heat demand and to flatten the heat load duration curve. Due to the variable nature of heat demand, there is a need for heat storage, but there is also a need for the fragmentation of power into two units of cogeneration to increase the operational flexibility in these plants. When the heat produced by the combined heat and power (CHP) unit is insufficient to meet the heat load, the heat stored can then be used to meet that demand. Heat storage plays a significant role in managing the heat supply and demand profiles in the CHP system, and in reducing its capacity and size. Trigeneration and heat storage are used as options to increase the operating time of cogeneration units and, implicitly, the amounts of heat and electricity generated in cogeneration. The results of this study demonstrate the economic and technical viability of the cogeneration and trigeneration solutions proposed. For the values of electricity and natural gas prices at the time of the analysis (2021), Scenario 4 is characterized as the optimal economical and technical option for the current rate of consumption, as it ensures the highest values of heat and electricity production and the shortest investment payback period (5.06 years). Compared with separate heat and power generation, we highlight a primary energy saving of 25.35% and a reduction in CO₂ emissions of 241,138 kg CO₂/year.

Solar air heater systems are equipment that uses energy captured directly from the sun to heat an existing airflow through the module. The technology to operate these systems is based on clean, renewable and free energy. Solar air heaters absorb thermal energy from the sun using an ab-sorption surface and achieve a transfer of heat from the absorption surface to the air flow supplied by one or two fans. This type of equipment can be used for space heating, drying, or ventilation processes. In addition, the equipment is capable of operating in cogeneration with other systems, e.g., preheating the air used for drying wood, preheating the air used to heat industrial premises, or preheating the water used in different heating systems. This scientific work is meant to reveal the current research context and the future opportunities in the case of cogeneration applications of solar air heaters, which are analyzed in light of their actual evolving dynamics. On this basis, we highlight expectations regarding the main problems that the regenerable energy is currently facing in this specific research and development environment as well as focusing our direction on the eventual solutions that are considered in the present and on their shortcomings in the future with evolved necessities.

In the current context of the transition toward climate neutrality and the pressing need to reduce energy consumption in the construction sector, nZEBs have become a central benchmark in European sustainability policies. These buildings offer multiple benefits, such as reduced operational costs, enhanced thermal comfort, and improved indoor air quality. Achieving such performance requires the integration of advanced technological solutions, including passive façades with ventilated cavities. The primary objective of this study is to investigate the influence of cavity geometry on the thermal behavior of a passive façade, through numerical simulations conducted in ANSYS Fluent 17. The study focuses on comparing five distinct configurations with varying cavity widths, aiming to identify the optimal solution in terms of heat transfer efficiency. The main contribution lies in the analysis and correlation of air temperature and velocity distributions with the cavity’s geometric parameters, highlighting the impact of channel width on thermal performance. The configuration with a 12 cm wide air channel recorded the highest heat flux at the outlet, approximately 44 times greater than the façade with a 4 cm wide channel, making it the most efficient solution. The results indicate significantly higher thermal efficiency for the configuration with a larger cavity width, contrary to initial intuitive assumptions. These insights provide a valuable framework for the optimal design of passive façades in nZEB applications and highlight the need for further research, combining numerical and experimental approaches, to develop sustainable and energy-efficient building envelope solutions.

The double-skin façade (DSF), referred to hereinafter as a passive façade, represents an alternative technology aimed at improving the energy performance of buildings with glass envelopes. A passive façade consists of a traditional façade supplemented on the interior by a secondary layer, which is separated by a ventilated cavity with a variable width. Numerous studies have been conducted to optimize the control of passive façades with the aim of improving building energy performance. This study focuses on comparing experimental data for the passive façade with numerical simulations conducted in ANSYS Fluent 17, proposing optimization options based on the analysis of temperature and velocity fields within the façade. The results reveal the dynamics of natural free convection within the passive façade, the presence of recirculation zones in the experimental model, and the manifestation of the “chimney effect” observed in the temperature analysis of the façade’s interior in both experimental and numerical models. ANSYS Fluent 17 is a numerical simulation software used extensively in engineering and research to provide precise and comprehensive solutions for complex fluid dynamics problems. Although there is a body of existing research, the need for further investigation into façade design, control, and optimization continues.

In a global context marked by increasingly evident climate change and an urgent need to reduce carbon emissions, efficient and environmentally friendly energy solutions are no longer just an option, but a necessity. Decarbonizing cities is an essential process for combating climate change and creating a sustainable urban environment. This article provides an analysis of the decarbonization possibilities of the building heating sector in the case of cities with district heating systems. A case study referring to the district heating system of Suceava city, Romania, is provided. The results of this study show a significant reduction in carbon emissions per unit of thermal energy delivered (95.97%) from the district heating system after 2015 because of the change in technology and primary energy source (cogeneration and biomass). Also, a comparative analysis is provided: district heating vs. individual heating in terms of carbon dioxide (CO₂) emissions for the same amount of heat supplied to end consumers in 2023. The comparative analysis highlights a difference in CO₂ emission of 81.66% (0.220 kg CO₂/kWh for individual heating and 0.040 kg CO₂/kWh for district heating). The implications of high-efficiency cogeneration in the decarbonization of the building heating sector are analyzed and highlighted.