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This study presents a sophisticated numerical simulation model for a forced circulation solar water heating system (FC-SWHs), specifically designed for the unique climatic conditions of Algeria. The model aims to cater to the hot water needs of single-family houses, with a daily consumption of 246 L. Utilizing a dynamic approach based on TRNSYS modeling, the system’s performance in Ain Temouchent’s climate was scrutinized. The model’s validation was conducted against literature results for the collector outlet temperature. Key findings include a maximum monthly average outlet temperature of 38 °C in September and a peak cumulative useful energy gain of 250 W in August. The auxiliary heating system displayed seasonal energy consumption variations, with the highest rate of 500 kJ/hr in May to maintain the water temperature at 60 °C. The energy input at the storage tank’s inlet and the consistent high-level energy output at the hot water outlet were analyzed, with the former peaking at 500 W in May. The system ensured an average water tank temperature (hot, middle and bottom) and water temperature after the mixer, suitable for consumption, ranging between 55 °C and 57 °C. For applications requiring cooler water, the mixer’s exit temperature was maintained at 47 °C. The study’s key findings reveal that the TRNSYS model predicts equal inlet and outlet flow rates for the tank, a condition that is particularly significant when the system operates with high-temperature water, starting at 55 °C. The flow rate at this temperature is lower, at 7 kg/hr, while the water mass flow rate exiting the mixer is higher, at 10.5 kg/hr. In terms of thermal performance, the system’s solar fraction (SF) and thermal efficiency were evaluated. The results indicate that the lowest average SF of 54% occurs in July, while the highest average SF of over 84% is observed in September. Throughout the other months, the SF consistently stays above 60%. The thermal efficiency of the system varies, ranging from 49 to 73% in January, 43–62% in April, 48–66% in July, and 53–69% in October. The novelty of this research lies in its climate-specific design, which addresses Algeria’s solar heating needs and challenges. Major contributions include a thorough analysis of energy efficiency metrics, seasonal auxiliary heating demands, and optimal system operation for residential applications, supporting Algeria’s goal of sustainable energy independence.

The constantly increasing energy demand in aged households of urban areas highlights the need for effective renovation solutions towards nZEB to meet the European Commission’s energy reduction and decarbonization targets. To address these targets, a variety of retrofitting interventions are proposed that incorporate hydronic systems into the building envelope, minimizing heat loss through the external walls and occasionally heating or cooling adjacent thermal zones. The present study analyses a low-temperature solar-powered hydronic active wall layer attached to the skin of a residential building in combination with solar collectors for heat generation. A typical floor of a five-storey, post-war, poorly insulated multi-family building is modelled considering two different climatic conditions: Berlin (Germany) and Kastoria (Greece). The design parameters, such as the area of the collector, the temperature of the fluid entering the active layer, the volume of the buffer tank and insulation thickness have been determined in order to optimize the impact on the heating system. Techno-economic assessment—followed by sensitivity analysis—has been conducted to scrutinize the feasibility of such a renovation solution. Last but not least, the nZEB compliance for both cases is examined based on EU and national nZEB definitions. The results indicate that a reduction of heating demand by up to 93% can be achieved, highlighting that such a renovation solution can be profitable in both examined locations while at the same time reaching the nZEB state.

Urban buildings significantly contribute to greenhouse gas (GHG) emissions, while also being highly vulnerable to rising temperatures driven by climate change. This dual role is particularly critical in Mediterranean regions, where hot, dry summers and dense urban fabrics exacerbate thermal discomfort. This study investigates the impact of future climate scenarios (2050 and 2080) on indoor thermal comfort in residential blocks with interior courtyards. A numerical approach based on TRNSYS 18 is used, combining a microclimatic courtyard model and a green wall energy balance model. Thermal discomfort is evaluated over the summer period for all building floors, distinguishing daytime (06:00–18:00) and nighttime (18:00–06:00) conditions. The results show a marked increase in cumulative discomfort (°C.h), especially on upper floors where solar exposure and heat accumulation are highest. Green walls demonstrate notable effectiveness on intermediate floors (4th–8th), acting as thermal buffers and reducing peak overheating during the day. However, their performance is limited at night due to the dominance of stored heat release over direct solar gains which highlight the importance of integrating green walls with complementary passive strategies to enhance resilience to climate change in dense urban environments.

Ground source heat pump (GSHP) systems stand for an efficient technology for renewable heating and cooling in buildings. To optimize not only the design but also the operation of the system, a complete dynamic model becomes a highly useful tool, since it allows testing any design modifications and different optimization strategies without actually implementing them at the experimental facility. Usually, this type of systems presents strong dynamic operating conditions. Therefore, the model should be able to predict not only the steady-state behavior of the system but also the short-term response. This paper presents a complete GSHP system model based on an experimental facility, located at Universitat Politècnica de València. The installation was constructed in the framework of a European collaborative project with title GeoCool. The model, developed in TRNSYS, has been validated against experimental data, and it accurately predicts both the short- and long-term behavior of the system.

The sizing of a solar thermal system to feed the water distillers in the laboratory of the Santander Technological Units is presented, proposing a comparative study between three calculation methods (f-chart, instantaneous and ACSOL) for the estimation of the surface of solar capture, finally supported by modeling in the TRNSYS software of the final system, to evaluate its behavior dynamically during one year. Initially, a search for information is carried out to establish the models to develop each of the calculation methods, additionally technical data is collected from the laboratory equipment to determine the consumption of hot water. Subsequently, each of the calculation methods is applied in order to size the catchment surface, to finally carry out a comparative study between the results obtained, determining which is the most appropriate method for the calculation and defining the dimensions of the same, to develop a modeling of the dynamic behavior of the system through the TRNSYS Software. The final result presents a storage system with an average temperature of 62.13 ° C and solar collectors with an average temperature of 58.7 ° C for one year of operation. Finally, the operating time of the resistive stills is reduced from 11 hours a day to 6 hours with the integration of the Thermosolar system.

The authors would like to acknowledge the support given by the rest of the members and institutions participating in the REHABILITAGEOSOL (RTC-2016-5004-3) project. The computationalwork has been carried out using the computer facilities of the Extremadura Center for Advanced Technologies (CETA-CIEMAT).

Buildings consume approximately ¾ of the total electricity generated in the United States, contributing significantly to fossil fuel emissions. Sustainable and renewable energy production can reduce fossil fuel use, but necessitates storage for energy reliability in order to compensate for the intermittency of renewable energy generation. Energy storage is critical for success in developing a sustainable energy grid because it facilitates higher renewable energy penetration by mitigating the gap between energy generation and demand. This review analyzes recent case studies—numerical and field experiments—seen by borehole thermal energy storage (BTES) in space heating and domestic hot water capacities, coupled with solar thermal energy. System design, model development, and working principle(s) are the primary focus of this analysis. A synopsis of the current efforts to effectively model BTES is presented as well. The literature review reveals that: (1) energy storage is most effective when diurnal and seasonal storage are used in conjunction; (2) no established link exists between BTES computational fluid dynamics (CFD) models integrated with whole building energy analysis tools, rather than parameter-fit component models; (3) BTES has less geographical limitations than Aquifer Thermal Energy Storage (ATES) and lower installation cost scale than hot water tanks and (4) BTES is more often used for heating than for cooling applications.

The vision of decarbonization creates the need to design and construct even more energy-efficient buildings. This current target is even more compelling and challenging. The main issue when designing energy-efficient buildings is to identify present and future building energy requirements. A trending method for solving this problem is dynamic building energy simulation. One of the main inputs during energy simulation is weather data. However, the real problem lies in the fact that standard weather data are good at defining the present situation, and they help in designing buildings that behave efficiently under current climate conditions. To achieve the goal of constructing climate proof buildings, the Weather Research and Forecast meteorological model (WRF) was used to predict future climate scenarios. At first, data from previous years (2006–2010) were used to represent the current climate. The model was used to generate future climate data. Thus, results were produced for 5 year periods 2046–2050 and 2096–2100. These data were used for the energy simulation of an office building in Thessaloniki, Greece. The simulation results showed a reduction in heating loads by approximately 20% in the long term and a simultaneous impressive increase in cooling loads by 60%, highlighting the inadequacy of the existing building shell, as well as the heating, ventilation, and air-conditioning (HVAC) system design.

Heating ventilating air-conditioning (HVAC) systems have been increasingly widespread in Italy: they can exploit renewable energies, are energy efficient systems, do not directly consume fossil fuels, and in the post-pandemic era, have also been subject to incentive processes by the Italian government. In South Tyrol, subject to harsh climates in both the winter and summer seasons, ground-source heat pump (GSHP) systems can be an excellent solution for the air conditioning of buildings. Unfortunately, too often, the design of HVAC systems with borehole heat exchangers (BHEs) is not adequate, and therefore, an innovative and expeditious numerical solution is proposed. A new numerical element (named Type285), written in Fortran code, was developed for TRNSYS 18 and able to implement the main features of BHEs and the surrounding aquifer. Type285 was compared with numerical models present in the literature (using hydrogeological software such as MODFLOW) and validated with the experimental data. The demonstration of the exchanged energy increase between the BHE and subsoil due to the increase in the groundwater flow velocity was carried out and evaluated. The choice to simulate BHE in TRNSYS using Type285 can be a fast and advantageous solution for HVAC system design.

This study investigates the influence of input values for building energy model parameters on simulation results, with the aim of improving the reliability and sustainability of energy performance assessments. Dynamic simulations were conducted in TRNSYS for three theoretical multi-residential buildings, varying parameters such as referent model dimensions, infiltration rates, envelope thermophysical properties, and interior thermal capacitance. The case study, based in Slovenia, demonstrates that glazing-related parameters, particularly the solar heat gain coefficient (g-value), exert the most significant influence—reducing the g-value from 0.62 to 0.22 decreased simulated heating (qH,nd) and cooling (qC,nd) demands by 25% and 95%, respectively. In contrast, referent dimensions for modeled floor area proved least influential. For Building III (BSF = 0.36), dimensional variations altered results by less than ±1%, whereas, for Building I (BSF = 0.62), variations reached up to ±20%. In general, lower shape factors yield more robust energy models that are less sensitive to input deviations. These findings are critical for promoting resource-efficient simulation practices and ensuring that energy modeling contributes effectively to sustainable building design. Understanding which inputs warrant detailed attention supports more targeted and meaningful simulation workflows, enabling more accurate and impactful strategies for building energy efficiency and long-term environmental performance.